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Katarina Dimic-Misic, Kari Vanhatalo, Olli Dahl, Patrick Gane
Rheological properties comparison of aqueous dispersed nanocellulose derived from a novel pathway-produced microcrystalline cellulose or by conventional methods

Appl. Rheol. 28:6 (2018) 64474 (15 pages)

Novel-produced never-dried and dried microcrystalline cellulose (MCC) was previously compared with a commercial MCC. The novel MCC was shown to be a suitable starting material for producing cellulose nanofibrils, in turn having similar molecular weight Mw, crystallinity, and particle size comparable to those from sequentially enzymatic and mechanically treated softwood sulphite pulp, but at lower cost. The study here presents a rheological parameterisation of the aqueous suspension throughout the process, aimed at delivering a correlation between specific surface area, at equal material particle size, and adsorptive coupling between neighbouring cellulose particles and interstitial water under flow. We conclude that combining dynamic viscosity with an independent measure of particle size provides a suitable quality control of MCC-derived cellulose nanofibrils, obviating the need for individual property-raw material relationships to be evaluated, and this principle may provide a generalised method for use in the production of cellulose nanofibrils.

Cite this publication as follows:
Dimic-Misic K, Vanhatalo K, Dahl O, Gane P: Rheological properties comparison of aqueous dispersed nanocellulose derived from a novel pathway-produced microcrystalline cellulose or by conventional methods, Appl. Rheol. 28 (2018) 64474.

The gas separation process by asymmetric polymeric membranes has received much attention during the last decades because of its more energy efficiency than other conventional separation processes. Hollow fibers are the most favored membrane geometry owing to their high surface area per unit volume of membrane module. One of the key elements determining the potential and applications of asymmetric hollow-fiber membranes are the structural properties mainly including pore size, pore distribution, selective layer thickness, molecular orientation and defectiveness. These elements can generally vary depending on conditions during dry-jet wet-spinning process. Flow conditions in spinneret during extrusion are known to affect the dense-layer of hollow fibers and possibly to enhance separation performance of hollow fibers. The aim of this study was to determine flow conditions of polyetherimide/N-Methyl-2-pyrrolidone solvent/ethanol non-solvent spinning solutions flowing through concentric annulus of spinneret during hollow fiber spinning process. The rotational rheometer was used to characterize rheological properties of spinning solutions. Newtonian behavior of the spinning solutions with arbitrary composition was shown. The effect of spinning solution and spinneret dimension on flow profile in spinneret was investigated. The Newtonian character of the spinning solutions caused constant velocity profile resp. shear rate profile regardless of dope composition when flowing through a spinneret with some flowrate. It has been shown the spinneret dimensions and geometry play a crucial role in controlling the shear flow in spinneret. The phase behavior of the PEI/NMP/EtOH dope system at a temperature of the hollow fiber spinning process (40oC) was studied.

Cite this publication as follows:
Ullsperger J, Valek R: Properties of polymer solutions intended for formation of hollow fibers membranes by inversion phases process, Appl. Rheol. 28 (2018) 65935.

The creep behavior of a new type epoxy resin adhesive which is room-temperature cured and used for reinforcing engineering structures was studied. The tensile strength of the adhesive has reached the desired values for the structural adhesive used for bonding concrete as the base material with steel. The short-term creep tests were conducted under four different stress levels. The generalized curve for reference stress was obtained by utilizing the time-stress equivalent principle. Moreover, compared with traditional Burgers model, an improved fractional KBurgers model obtained by replacing the Newton derivative with the fractional derivative element (Abel component) in the traditional Burgers model can capture the creep behavior of this epoxy adhesive with high precision in the condition of the room-temperature and tensile stress of 36 MPa.

Cite this publication as follows:
Li H, Luo Y, Hu D: Long term creep assessment of room-temperature cured epoxy adhesive by time-stress superposition and fractional rheological model, Appl. Rheol. 28 (2018) 64796.

Liposomal gel has played an important role in administration of drugs via topical and transdermal routes. Incorporation of liposome into gel not only has overcome the liquid nature of liposomal dispersion but also helped to preserve the original structure of liposome. In this study, we formulated a liposomal gel consisting of Carbopol gel and a diethylaminoethyl dextran (DEAE-DX) coated liposome. The effect of coated and non-coated liposomes on the rheological properties of Carbopol gel was investigated. The rheological results indicated that incorporation of liposomes into Carbopol gel modified the viscoelastic and flow behaviour of the gel significantly. Apart from that, liposomal gel consisting of DEAE-DX coated liposomes exhibited more solid-like behavior compared to the non-coated liposomal gel. Incorporation of DEAE-DX coated liposomes increased the yield stress of liposomal gel compared to non-coated liposomes. This supports the findings obtained from the amplitude and frequency tests whereby addition of DEAE-DX enhanced the rigidity of the gel so that the resultant gel was more resistant to flow.

Cite this publication as follows:
Menon P, Teo YY, Misran M: Effect of diethylaminoethyl-dextran coated liposomes on the rheological properties of carbopol gel, Appl. Rheol. 28 (2018) 62616.

This work describes the flow behavior of prevulcanised natural rubber latex (PvNRL) and PvNRL nanoblends containing 0.02, 0.04, 0.06, and 0.08 wt.% of aqueous dispersion of single-walled carbon nanotubes (SWCNT). The assay was performed under varying shear rates (between 0.1-100 1/s) at three separate isothermal temperatures (25, 30, and 35 °C) on a Modular Compact Rheometer (MCR) fitted with a concentric cylinder measuring system. A steady decrease in viscosity upon every single shear rate increment was observed for all the samples analysed. Thus, each measured viscosity was considered an apparent-viscosity; which confirms a typical non-Newtonian flow behavior. PvNRL blends containing highest wt.% SWCNT exhibited higher apparent viscosity at low shear rates, whereas the lowest wt.% SWCNT displayed a lower apparent viscosity, thus signifying a dilution effect. The power law model showed good fitting and successfully predicted the flow behavior within the modelled shear rate region.

Cite this publication as follows:
Agbakoba VC, Hlangothi P, Yah C, Simate G: A study of the flow behavior of prevulcanised natural rubber latex/singlewalled carbon nanotubes (SWCNT) blends using rotational viscometry and power law model, Appl. Rheol. 28 (2018) 64175.

In this research, a fully developed steady flow of a third-grade fluid in a pipe under an externally applied magnetic field with convection on wall is investigated. The governing equations including momentum and energy in the form of partial differential equations are reduced to ordinary differential equations which are solved numerically by using a finite element method (FEM) as part of the FlexPDE software package. For validity, the results are compared with the 4th order Runge-Kutta method. The effect of different physical parameters such as the non-Newtonian parameter, the Biot number, the Hartmann number, the Eckert number on the dimensionless velocity profiles, the dimensionless velocity gradient profiles, the dimensionless temperature profiles, and the dimensionless gradient temperature profiles have been discussed. It is concluded that by increasing the non-Newtonian parameter and Hartman number the dimensionless velocity, the velocity gradient, the temperature and temperature gradient profiles reduce and thus the heat transfer of fluid flow, the shear stress and the skin friction on the pipe wall decrease. Increasing the Biot number caused a decrease of the temperature and a more uniform dimensionless temperature profile of the fluid within the pipe. Besides, with a decrease of the Prandtl number, the dimensionless temperature decreases inside the pipe. In fact, the dimensionless temperature profile becomes flat. For this reason, the dimensionless temperature gradient decreases on the pipe wall which causes the reduction of the heat transfer rate on the pipe wall. Further, by increasing the Eckert number, the dimensionless temperature of the fluid within the pipe and the heat transfer from the fluid to the pipe wall increases. Applying the FlexPDE software for solving governing equations numerically seems to lead to appropriate and reasonable results.

Cite this publication as follows:
Javanmard M, Taheri MH, Ebrahimi SM: Heat Transfer of Third-Grade Fluid Flow in a Pipe Under An Externally Applied Magnetic Field with Convection on Wall, Appl. Rheol. 28 (2018) 56023.

Polytetrafluoroethylene (PTFE) micropowders were used to prepare PTFE-oil organogel. Carbonyl iron particles were dispersed in this organogel to fabricate magnetorheological fluids. The main aim of this paper is to investigate the influences on fieldinduced chains by non-magnetic microstructures inside these organogel-based MRFs. The field-induced anisotropy of MRFs between first normal stress differences to shear stresses and dynamic modulus reveal that organogel widen the non- Newtonian elastic range of MRFs as long as the non-magnetic particles content is appropriate. Both theoretical and experimental results of static and dynamic normal forces indicate that normal forces are influenced by magnetic and non-magnetic microstructures comprehensively. The dynamic normal forces are lower than static ones under low magnetic field strength while the phenomenon becomes opposite in the presence of high strength magnetic field. Moreover, a 3ITT test of normal forces exhibits a significant time-dependent behavior of the normal forces. The investigations of recovery ratio demonstrate that the non-magnetic microstructures help field-induced chains to recover at relatively low magnetic field strength but hinder this structural recovery at high magnetic field strength. Finally, a new investigation method on amplitude-dependent normal forces is introduced showing a four-region behavior as a function of strain amplitude, which reflects the internal microscopic evolution of MRFs and could be a proper way to study the influences on field-induced chains by non-magnetic particles.

Cite this publication as follows:
Zhang H, Hu Z, Yan H, Yang J, Niu F: The influences on field-induced chains by nonmagnetic microstructures inside the magnetorheological fluids Based on PTFE-oil organogel, Appl. Rheol. 28 (2018) 53921.

An approach of Nelson and Ewoldt [Soft Matter 13 (2017) 7578] to create a viscosity model of the Herschel-Bulkley type in order to use only parameters with the potential of containing fluid information has been extended to be applied to drilling fluids using current industry standard procedures. The commonly used Herschel-Bulkley consistency parameter k is found inadequate in describing fluid properties properly as it has a unit dependent on n. Hence, the model is not optimum for digitalisation. The Herschel- Bulkley model is re-written and base its parameters directly on the yield stress and the additional or surplus shear stress at a pre-determined shear rate relevant for the flow situation to be considered. This approach is also applicable for Power-law models.

Cite this publication as follows:
Saasen A, Ytrehus JD: Rheological Properties of Drilling Fluids - Use of Dimensionless Shear Rates in Herschel-Bulkley Models and Power-Law Models, Appl. Rheol. 28 (2018) 54515.

In the last decades, one of the most critical issues concerning the control on the processing, structure and properties of nanocomposites is related to the dispersion of nanofiller in the polymer matrix and internal interactions resulting in percolation. In this study, we investigate the rheological behavior in oscillatory and steady shear flow of poly(lactic) acid based nanocomposites incorporating 0 - 12 wt% graphene nanoplates (GNP) and multi-walled carbon natotubes (OH-MWCNT). The effect of the filler contents and aspect ratio on the viscosity and viscoelastic response is evaluated. Three rheological techniques are used for estimation of rheological percolation threshold. Due to different aspect ratio and state of dispersion of GNP and MWCNTs the percolation threshold differs significantly for both compositions φ ≤ 1.5 wt% for MWCNT/Pla and φp ≤ 5 wt% for GNP/Pla. The larger the aspect ratio of nanofiller, the lower is the rheological percolation threshold. The visualized structure by TEM analysis confirms the rheological predictions for both type composites. The index of flow was estimated by the power law slope of the flow curves and a better dispersion was assumed for MWCNTs in comparison with GNPs due to the surface modification. Based on the rheological percolation threshold and the flow index, nanocomposites were classified in three groups: Newtonian, percolated composites and elastic solids. Both characteristics are used to select the printing parameters for the three groups of nanocomposites, suitable for fused deposition modeling (FDM).

Cite this publication as follows:
Ivanova R, Kotsilkova R: Rheological study of poly(lactic) acid nanocomposites with carbon nanotubes and graphene additives as a tool for materials characterization for 3D printing application, Appl. Rheol. 28 (2018) 54014.

In the current research, focus is on the comparison of Jackson and Tucker (JT) theoretical model to experimental results of large amplitude oscillatory shear (laOS) of immiscible polymer blends. The field of rheology of immiscible polymer blends is currently very deficient in laOS results, especially at moderate to low viscosity ratio values. In addition, most of the theoretical modeling that was carried out on laOS of immiscible polymer blends used the small deformation theory of Maffettone and Minale. The current work adds further knowledge in the field of modeling of immiscible polymer blends by testing the predictions of the large deformation theory of Jackson and Tucker against laOS experimental behaviour. laOS experiments were carried out for a model immiscible blend composed of two Newtonian components (polybutadiene and polydimethylsiloxane) at viscosity ratios 1.34 and 0.39 and at volume fraction value 0.2. Data for the first, third and fifth harmonics of the sinusoidal stress response were recorded by FT-Rheological experimental set up. Validation of Jackson and Tucker model was carried out and the experimental results were compared to the JT model. Furthermore, the theoretical predictions of the JT code were compared to the experiments of Almusallam for two blends at viscosity ratio values of 0.1 and 4.4 at volume fraction value 0.21. The experimental results were plotted in terms of the scaling parameters of Reinheimer et al to test the scaling law. The Reinheimer scaling law was developed for viscosity ratio values larger than 2.5 and hence a new scaling law was developed in the current study taking into consideration the viscosity ratio values less than 2.5.

Cite this publication as follows:
Almusallam AS, Bini TB: Scaling Law Accomplished through Correlation of Large Amplitude Oscillatory Shear of Immiscible Polymer Blends with Jackson and Tucker Model, Appl. Rheol. 28 (2018) 46039.

The viscoelastic properties of a gallium-indium alloy in the pre-yield region make it easier to understand their characteristics, particularly the varying degrees of stiffness and damping properties. These viscoelastic properties were measured with a straincontrolled rheometer, where both strain amplitude sweep mode and the angular frequency sweep mode were conducted. Three groups of experiments were carried out in the strain amplitude sweep mode. In the angular frequency sweep mode, the storage modulus G' and the loss modulus G''were investigated at the linear region, the critical region, and the non-linear region. Experimental results indicate that the gallium-indium alloy exhibited similar viscoelastic properties. The linear viscoelastic region takes place when the strain amplitude is less than the critical strain amplitude of 1%. At the critical regime, the gallium-indium alloy has the strongest relative elasticity. These results are helpful to understand the intrinsic properties of gallium-indium alloys and find their application in flexible circuits, soft robotics, self-healing, and mechanical shock absorption.

Cite this publication as follows:
Yang Y, Sun S, Tang S, Li W, Zhang S: The Viscoelastic Properties of Gallium-Indium Alloy, Appl. Rheol. 28 (2018) 42903.

The temperature has a significant influence on the character of flow of polymer suspensions filled with BaTiO3 nanoparticles, changing its viscosity and rheology. The viscous flow of suspensions at lower temperature from 5 to 25˚C began at higher acti- vation energy ΔEa1 and the systems were thixotropic, characterized with shear thickening at the initial stage of shearing after breaking of structural bonds between the polymer molecules. Herewith, increased shear stresses caused the enlargement of structural elements through additional flocculation by polymer bridging because of adsorption-desorption of EthCell molecule on BaTiO3 nanoparticles surface. At higher temperatures of 30 – 45 ˚C the viscous flow of suspensions began at the lower values of ΔEa2 indicating decreasing of leisure EthCell chains sufficient to form transient polymer network. Elevation of the temper-ature stipulated the predominant contribution of thermal Brownian motion to the character of flow. The mobility of macromolecules segments increased, BaTiO3 nanoparticles became to rotate, making impossible the additional structuring. Hence, the effective hydrodynamic radii of floccules remained constant. Moreover, being thixotropic at lower temperatures, the sus-pensions were characterized by the increasing of effective radii of floccules throughout the shear thickening region. In turn, rheopexic-thixotropic type of flow was characterized by the constant size of floccules along up-flow curves due to the dominant contribution of rotational Brownian motion. Thus, it is very important to control the temperature regime of processing method when exploitation of polymer suspensions.

Cite this publication as follows:
Umerova S, Ragulya A: Temperature dependent rheology of plasticized polymer suspensions filled with ceramic nanoparticles, Appl. Rheol. 28 (2018) 45489.

Drilling fluid constitutes an important part of the drilling operations. Gel strength property of drilling fluids plays a key role in drilling multilateral and long horizontal reservoir sections. Losing the gel strength will accumulate drilled cuttings and as a result, sticking of the drill string. Solving this issue takes a long time and increase the total cost of the drilling operations. The objectives of this paper are to (1) determine the rheological properties of calcium carbonate water-based drilling fluid over a wide range of temperature, (2) assess the effect of adding nanoclay, bentonite, and nanosilica on the gel strength problem associated with the current field formulation of calcium carbonate water-based drilling fluids, and (3) optimize the concentration of bentonite, nanosilica, and nanoclay in the drilling fluid. The concentration of bentonite, nanoclay, and nanosilica was varied from 1 wt% to 10 wt%. Rheological properties results confirmed that the gel strength of the calcium carbonate water-based drilling fluid reached zero lb/100ft2 by increasing the temperature to 200 °F (93.33 °C). This issue was solved by adding different concentrations of bentonite, nanoclay, and nanosilica. At low bentonite concentrations (3.33 wt%), the gel strength still reduced with time. At high bentonite concentrations (10 wt%), the gel strength increased with time. The optimum concentration of bentonite was 6.66 wt%, which yielded a flat rheology profile of the gel strength. These results confirmed that the rheological properties of the water-based drilling fluid were optimized by using bentonite. Similarly, 7.5 wt% nanosilica showed the optimum performance. Nanoclay was not effective in improving the rheological properties of the calcium carbonate drilling fluid.

Cite this publication as follows:
Elkatatny S, Kamal MS, Alakbari F, Mahmoud M: Optimizing the Rheological Properties of Water-based Drilling Fluid Using Clays and Nanoparticles for Drilling Horizontal and Multi-Lateral Wells, Appl. Rheol. 28 (2018) 43606.

Cite this publication as follows:
Baller J, Wagner C, Roose P: Joint Symposium Rheology - 360° of the Belgian Group of Rheology, German Rheological Society, and ProcessNet-Subject Division Rheology, Appl. Rheol. 28 (2018) 53.

Two geometrical models are developed to simulate fluid transport via peristaltic motion in tubes of uniform or linearly decreasing radius: A 2-D axisymmetric tubular model and a 2-D axisymmetric conical model. In both models, peristaltic motion is induced by a traveling wave along the wall of the computational domain which deforms the wall and the computational mesh. These geometrical models are coupled with a finite volume solver from the open source software package OpenFOAM which is used to simulate the peristaltic flow for different Newtonian and non-Newtonian fluids in the laboratory (or Eulerian) frame of reference. After validation of the solver with experimental data, simulations are performed in each geometrical model to determine the influence of a given set of parameters on peristaltic flow behavior and transport efficiency. The parameters that are varied include the wave speed, relative occlusion, Newtonian viscosity, and power-law index for shear-thinning non- Newtonian fluids. For both computational models, the transport efficiency is found to increase strongly with relative occlusion, to decrease as the amount of shear-thinning increases, and to be independent of wave speed. In the tubular model, transport efficiency is found to be independent of Newtonian viscosity, while in the conical model, it decreases as viscosity decreases for Reynolds numbers greater than one.

Cite this publication as follows:
Alokaily S, Feigl K, Tanner FX, Windhab EJ: Numerical Simulations of the Transport of Newtonian and Non-Newtonian Fluids via Peristaltic Motion, Appl. Rheol. 28 (2018) 32832.

The oscillatory shear rheological behaviors of a polyolefin plastomer (POP) at various temperatures were examined within its linear viscoelastic (LVE) regime. The apparent storage modulus, loss modulus, complex modulus, complex viscosity, and phase angle of POP at various temperatures are all found gap dependent, revealing that wall slip occurred under the applied oscillatory shear with the shear stress amplitude controlled constant. All Han plots and van Gurp-Palmen (vGP) plots of POP samples overlapped each other at various gaps at a certain temperature, suggesting that a time-gap-superposition (TGS) is valid with all the apparent angular frequency dependent storage modulus and loss modulus of POP at various gaps shifted to their master curves at a selected reference gap. This indicates that the wall slip can be understood as adding a dashpot in series to POP sample only with the apparent relaxation time multiplied by a shift factor. By TGS, a method to determine the wall slip length b and the actual oscillatory shear rheology of the fluids was consequently established. The results showed that the obtained b is dependent on temperature and wall slip made it possible to extend the experimental angular frequency range to lower frequencies. Further analysis revealed that wall slip did not influence the Arrhenius viscosity dependence of POP on temperature, while the viscous flow activation energy decreased.

Cite this publication as follows:
Li J, Wang L, Yu D, Christiansen JdC, Jiang S: Wall Slip of Polyolefin Plastomers under Oscillatory Shear, Appl. Rheol. 28 (2018) 33226.

Spiral blood flow in the aorta is helpful in maintaining the stability of flow, reduction in lateral forces, turbulence near walls, and shear stress index. Thus, it helps in the prevention of diseases, such as atherosclerosis and atherogenesis, in the aortic arch because of the reduced accumulation of low-density lipoproteins (LDLs). To investigate the actual physics behind the aforementioned phenomenon, we conducted a fluid-structure interaction (FSI)-based numerical simulation of the threedimensional aortic arch model under the influence of a pulsatile spiral flow. Spiral flow was introduced through the use of a mapping methodology between a spiral graft model and aortic model. The physics of time dependent pulsatile spiral turbulent flow was coupled with the structural mechanics of the aorta by using the FSI method. Results showed that the exterior interface of the aortic arch tends to rupture under the actions of centrifugal forces and secondary flow counter-rotating vortices in addition to applied pressure forces. Under systolic and diastolic conditions, the interior and exterior interfaces of the aortic arch both had small displacement, thus showing the insignificant role of velocity gradients in wall deformation. Moreover, LDL accumulation in the aorta under the influence of pulsatile spiral flow has been investigated using particle tracing methodology. The LDLs were evenly distributed in the aorta because of the influence of spiral flow. This result shows that spiral flow can contribute to the elimination of threats from diseases, such as atherosclerosis and atherogenesis.

Cite this publication as follows:
Ashraf F, Cheema TA, Park CW: The Impact of Pulsatile Spiral Flow on the Wall Deformation Characteristics and Low-Density Lipoproteins Accumulation in the Aorta, Appl. Rheol. 28 (2018) 35702.

Rheological properties of KCl/polymer type drilling fluids containing particulate loss prevention material (LPM) were characterized by an integrated inverse model-experimental approach. Rheological measurements for LPM-laden KCl/polymer type drilling fluids were carried out on a 6-speed rotational viscometer. The algorithm based on Tikhonov regularization was validated to be applicable and reliable to compute the shear rate in a rotational viscometer equipped with a widened annular gap. With the validated algorithm, the dial readings versus rotational speed data were transformed into shear stress vs. shear rate form. The results indicate that the rheological diagrams of the KCl/polymer type drilling fluids resemble those of a yield stress fluid and can be well represented by the Hershel-Bulkley model. The observed variation shows that rheological parameters were affected significantly by the addition of particulate LPM. The amount and the particle size of particulate LPM have a combined effect on the rheological properties of LPM-laden KCl/polymer type drilling fluids.

Cite this publication as follows:
Wang G, Du H: Rheological Properties of Kcl/Polymer Type Drilling Fluids Containing Particulate Loss Prevention Material, Appl. Rheol. 28 (2018) 35727.

In petroleum drilling, aqueous Polyanionic Cellulose solutions (PAC) are often used as a drilling fluid model system in experimental laboratory studies to investigate cuttings transport. Cuttings transport refers to the transportation of drilled-off solids out of the wellbore. In these studies, PAC solutions are typically assumed to behave purely viscous, i.e. they do not show timedependent/ thixotropic and/or viscoelastic properties. In this study, a rheological characterization of PAC has been performed in combination with an evaluation of time scales characterizing the fluid to verify the conventional assumption of a purelyviscous fluid. It is found that PAC solutions are generally not purely viscous: They feature viscoelastic behavior on time scales of the order of 0.01 to 1 s, such as normal stress differences, as well as thixotropic behavior on larger time scales of the order of 10 to 1000 s because of their polymeric microstructure. If simplified to a purely viscous fluid, the degree of uncertainty in representing the measured apparent shear viscosity may increase by an order of . 75 to 90 % depending on the relevant time scale. When obtaining flow curves, a sufficiently long measurement point duration (sampling time for a particular torque reading) is required to ensure that the liquid microstructure has reached its dynamic equilibrium at the desired shear rate. Due to their polymeric nature, PAC solutions feature Newtonian viscosity plateaus at both low and high shear rates. For modeling purposes, the application of a Cross/Carreau material function is recommended because it both best describes the flow curve data and minimizes extrapolation errors compared to the conventionally used Power law material function.

Cite this publication as follows:
Busch A, Myrseth V, Skjetne P, Khatibi M, Johansen ST: Rheological characterization of polyanionic cellulose solutions with application to drilling fluids and cuttings transport modeling, Appl. Rheol. 28 (2018) 25154.

In this paper, we present a novel method we have developed for measuring the drag reduction in a dilute polymer solution, based on the triboelectricity phenomenon. The presence of a small quantity of polymer with high molecular density in a liquid decreases the friction of the liquid on solid walls. This property defines drag reduction. The friction itself produces electricity in the liquid known as triboelectricity. In this work, we show that drag reduction can be measured by measuring the triboelectric voltage in the solvent and in the polymer solution. The method was tested on well characterized dilute solution of polyethylene oxide (PEO) and the results obtained agree qualitatively well with those available in the literature, notably showing that for given flow rate, drag reduction by PEO increases with polymer concentration until reaching a plateau. Also, for given concentration, drag reduction increases with flow rate in the range of concentration and flow rate tested. More generally, a similar behavior is expected for any polymer solution obeying the power-law rheological model.

Cite this publication as follows:
Nsom B, Latrache N: Measurement of Drag Reduction in Dilute Polymer Solution using Triboelectric Effect, Appl. Rheol. 28 (2018) 25922.

A triple pressure-stage capillary rheometer was individually developed for providing an insight of pressure effect on polymeric melts viscosity during steady and continuous flow. Three capillary dies with identical/varied diameters and aspect ratio were assembled in series along the flow direction, relying on which the flow was divided into three zones with varied pressures under the same flow rate. Several polymeric melts, such as low density polyethylene (LDPE), polystyrene (PS), polypropylene (PP) as well as its nanocomposites of PP/CaCO3, PP/Mg(OH)2, and PP/ halloysite nanotubes (PP/HNTs) were taken as the experimental samples. The principles for calculating the pressure sensitivity of shear viscosity in capillary flow were discussed, including methods based on constant shear rate (CSR), constant shear stress (CSS), and curve superposition (CSP). For the several polymer melts adopted in this work, a sequence of pressure dependence of viscosity was revealed as PS > PP > LDPE, which is typically acknowledged.

Cite this publication as follows:
Lin X, Liu J, Wu C, Wu M, Ren D, Zhang J: Experimental evaluation of the pressure sensitivity of molten polymer viscosity with a triple-stage capillary rheometer, Appl. Rheol. 28 (2018) 25503.

A novel method is introduced to describe quantitatively hysteresis seen in flow curves of microfibrillated cellulose suspensions. Also, a data normalisation procedure is presented that allows a direct comparison of data from suspensions of different solids contents. The discussion of the flow curve hysteresis of an MFC suspension is proposed to provide a lot of information on the suspension morphology under flow. Such information is not only useful for process design, but also may serve as a quality control tool. Hysteresis data as a function of the suspension solids content are provided, and considered with reference to an overview made of peer work in the field. Two discrete hysteresis loop areas were found in the flow curves presented in this work, each associated with a distinct shear rate region, one where the viscosity of the flow curve during shear rate increase is higher than that of the shear rate flow curve at decreasing shear rate (named positive hysteresis) and another where it is the opposite (named negative hysteresis). This behavior seems to have been rarely reported, and where reported we offer an explanation, based on morphological models and rheometer measurement set up, as to why other researchers may find a variety of hysteresis forms. It is hypothesised that the negative normalised hysteresis is mainly depending on the excessive flocculation/ structuration induced at intermediate shear rates during the shear rate increase, and that it is necessarily less with increasing solids content because of the reduced availability of free water. The positive normalised hysteresis, however, is considered to originate from the different morphologies at lower shear rates, i.e. the initial, homogeneous structure vs. the structure that was previously induced by the intermediate shear during shear rate decrease. The positive normalised hysteresis appears not to depend on the solids content, indicating a self-similarity or scaling behavior of the structuring with respect to the underlying network structure.

Cite this publication as follows:
Schenker M, Schoelkopf J, Gane P, Mangin P: Quantification of flow curve hysteresis data . a novel tool for characterising microfibrillated cellulose (MFC) suspensions, Appl. Rheol. 28 (2018) 22945.

Concentrated suspensions are very complex in nature and exhibit non-Newtonian flow properties although the suspending fluid might behave as a Newtonian fluid. Among the interesting properties, wall slip will be the main focus of this study. The formation of wall slip layer adjacent to the solid boundary may lead to inaccurate measurement of rheological properties. So, the measured viscosity can be lower than the actual viscosity and thus a basic understanding on wall slip is critical. Concentration, particle size, and temperature are the factors affecting the wall slip mechanism. Therefore, this research study tends to study the relationship between the parameters (concentration, particle size, and temperature) and wall slip. The result shows that the slip velocity increases with shear stress under the conditions where (i) concentration decreases, (ii) particle size increases, and (iii) temperature increases. Two regression models considering the three parameters are proposed and can be used respectively as an alternative to predict slip velocity and true shear rate.

Cite this publication as follows:
Chin RJ, Lai SH, Ibrahim S, WanJaafar WZ: Factors affect wall slip: particle size, concentration and temperature, Appl. Rheol. 28 (2018) 15775.

The hydration kinetics of four CEM I 52.5 N cements in the presence of two different superplasticizers was studied. The kinetics was characterized by monitoring the evolution of the dynamic modulus at constant frequency on a rotational rheometer. The method consists of predicting the time dependence of the elastic modulus by a kinetic equation of the self-acceleration type and fitting the equation to the experimental data. The model defines two main characteristic constants i.e. the characteristic time which defines the initial rate of hydration and the self-acceleration coefficient. It is shown that the model can accurately predict the initial hydration of cement paste with and without superplasticizer. The effect of the different cement properties and their interaction with superplasticizers can be observed in the kinetics of hydration.

Cite this publication as follows:
Masalova I, Mbasha W, Haldenwang R, Malkin AY: Rheokinetics of cement paste hydration during the dormant phase, Appl. Rheol. 28 (2018) 15452.

The performance of modern slurry dewatering equipment is essentially dependent on the efficiency of compression. Shear yield stress as an index of flowability and compressibility is affected by suspension properties, while the presence of reagents may be significant. In this work, the effect of fine fraction, pH, flocculant, and collector concentration on the shear yield stress of copper flotation tailings at concentrators placed at Sarcheshmeh and Shahrebabak (Iran) were examined. Slump and settling tests were utilized to investigate the shear yield stress and compressibility of suspension. A pilot scale column was also employed to investigate the compressibility of suspension. Results indicated that shear yield stress increase, while compressibility decrease with flocculant concentration and fine fraction. It was found that the shear yield stress steadily increased with pH. Furthermore, in the presence of collectors the shear yield stress was reduced, while the compressibility enhanced.

Cite this publication as follows:
Garmsiri MR, HajiAminShirazi H: The effect of suspension properties on shear yield stress and compressibility of the suspension of copper flotation tailings, Appl. Rheol. 28 (2018) 15721.

White Portland cement can be used such as decorative coatings, masonry regularization as the skin coat, and many other applications mainly due to the ease of association with pigments to confer coloring to the applied products for aesthetic purposes. Despite of the evaluation of the hardened stage properties to be more commonly found in literature, just a few published works monitored the transition from fluid-to-solid stage, but this is an important step because it defines the performance of products over time. The main purpose of this work was to compare the consolidation of different types of white Portland cement during the hardening stage, i.e. using a combined evaluation of the chemical and physical phenomena. Isothermal conduction calorimetry was the method used to monitor the heat release during the hydration reaction and oscillatory and compressive rheometry were applied to monitor the changes in workability over time. The setting time, measured by Vicat test represents the open time of each composition and was evaluated because it is affected by the physicochemical changes of the cement. Despite the obtained results are standardized, they are empirical/arbitrary by nature. Three brands of white Portland cements (CauêAalborg, and Tolteca) were chosen and their suspensions were prepared to achieve a constant watercement ratio of 0.5. All suspensions presented shear thinning behavior, but different levels of yield stress and apparent viscosity. The Tolteca cement presented the fastest heat release, which impacted the gain on consistency as measured by oscillatory rheometry or the loss of workability as measured by the squeeze flow test. The combined evaluations, i.e. physical and chemical results indicated that despite the fact that the changes during the hardening process had been affected: Correlations were only observed in the physical parameters indicating that the hydration reaction promotes random changes in the microstructure development.

Cite this publication as follows:
Carbone CE, Romano RCdO, Cincotto MA, Pileggi RG: Hardening stage evaluation of white Portland cements using oscillatory and compressive rheometry, isothermal calorimetry and the Vicat test, Appl. Rheol. 28 (2018) 16396.

Cite this publication as follows:
Sahlstrom A: Rheology Step 2 training - continuation training in application of rheological concepts and techniques - viscosity, viscoelasticity and measuring techniques, Appl. Rheol. 27 (2017) 45.

Effect of different bulk sweeteners including maltitol, isomalt and inulin on the steady and dynamic rheological behaviors as well as chocolate structure was investigated. All the chocolate samples showed shear-thinning behavior, which was mainly affected by the shear rates. Among different rheological models, the power law model was the suitable one (high R2) for the chocolate samples containing bulk sweeteners. As the bulk sweetener has the more solid volume fraction, the more flow behavior index n was obtained. Bulk sweeteners depending on their molecular structures were influenced on the apparent viscosity and yield stress. The mechanical spectra of chocolate showed the liquid-like behavior of inulin and maltitol and solid- like behavior of sucrose and isomalt. It was also revealed that the chocolate network structure was completely influenced by temperature and related to the frequency range. During thermal processing, the bulk sweeteners did not have any effect on the chocolate consistency and they cause to reduce the network strength of the chocolate. In addition, the critical stress was sensitive to the type of bulk-sweeteners in the chocolate. Consequently, chocolate can be considered as a weak dispersion which makes aggregates and can be modeled by the weak physical gel model. Current research realized great insight to the chocolate rheology in different processes such as enrobing, shell formation and molding.

Cite this publication as follows:
Kiumarsi M, Rafe A, Yeganehzad S: Effect of different bulk sweeteners on the dynamic oscillatory and shear rheology of chocolate, Appl. Rheol. 27 (2017) 64123.

Bacterial cultures, when under appropriate conditions, will grow into a biofilm. This weak hydrogel, composed of a complex conglomeration of bacterial clusters and extrapolymeric substances, serves to protect and insulate the bacteria from mechanical disturbances and environmental perturbations that may include antibiotics. Measuring the bulk rheology of the biofilm provides a quantitative description of the macroscopic structural integrity of the soft solid, which can be used to evaluate the efficacy of techniques that are often directed at their removal or prevention. Techniques for measuring the rheology of biofilms vary significantly, ranging from filtering or scraping the biofilm from its growth medium to attempting to grow the biofilm directly on the geometry of the rheometer. In this study, we developed a protocol for measuring the bulk rheology of a biofilm that was grown in a liquid medium. By keeping the biofilm intact from its growth phase through its rheological measurement, this method allows the mechanical strength of the biofilm to be probed without compromising its integrity. Presented in the form of case studies, the results from this study confirmed the gel-like structure of the biofilm of the wild-type strain of Pseudomonas aeruginosa (PAO1). The flexibility of this protocol was shown by varying the incubation time of the biofilm from 4 to 9 days, providing a bulk elastic modulus that varied over two orders of magnitude and a yield stress that varied by an order of magnitude. Finally, in an attempt to demonstrate the fragility of biofilm, measurements were also taken on samples that were simply transferred from their incubated Petri dish to the rheometer. Results from the mechanical robustness of the biofilm are highlighted to emphasize the importance of understanding and addressing the mechanical strength of the biofilm system before attempting to remove the bacterial contamination through chemical or mechanical means.

Cite this publication as follows:
Daalkhaijav U, Walker TW: Developing a Nondestructive Technique for Measuring Bulk Rheology of Pseudomonas Aeruginosa Biofilm, Appl. Rheol. 27 (2017) 64033.

A challenge for underground CO2 storage is the leakage of the buoyant supercritical gas through microcracks in wellbores that cannot be sealed with current oilfield cements that are too viscous and cannot penetrate the cracks. Polymer gels consisting of pH-sensitive hydrogel particles suspended in an aqueous solution offer a potential alternative. The rheology of aqueous solutions of Carbopol 934 as a model pH-sensitive gel is measured to find the compositions and pHs for both ease of injection and to seal cracks against the flow of bulk CO2 and CO2 dissolved in brine. The polymer gels have low viscosity at low pH and can easily flow into the microcracks. In the elevated pH of the microcracks, the particles swell creating a significant yield stress sufficient to seal leakage pathways. The yield stress reaches a maximum at pH 5 and it increases with increasing concentration. The flow curves of stress versus shear rate for all pHs and concentrations are well-described by the Herschel-Bulkley model with an exponent of about 0.34 except for highly acidic conditions when the gelant solutions show a much lower yield stresses and higher exponents. The flow curves can be collapsed onto a single universal flow curve rescaled with the yield stress, the low frequency shear modulus and the suspending fluid viscosity. The presence of salts, especially high valence salts, reduce the yield stress of the gels considerably. It is shown that the addition of chelating agents mitigates this effect and can restore more than 30% of the yield stress of the gelant.

Cite this publication as follows:
Shafiei M, Bryant S, Balhoff M, Huh C, Bonnecaze RT: Hydrogel Formulation for Sealing Cracked Wellbores for CO2 Storage , Appl. Rheol. 27 (2017) 64433.

Cement-based materials exhibit highly complex rheological properties, in particular yielding and thixotropy. These two properties can be characterized by considering rebuilding under a constant stress (creep) after shear at high rate. The rebuilding kinetics can be considered through the time evolution of the viscoelastic properties. However at the beginning of the rebuilding process the oscillatory behavior may be non-linear since the microstructure is destroyed by the shear flow. In the present investigation the rebuilding kinetics of cement pastes under oscillatory stress is considered through the transition from large amplitude oscillatory shear (laOS) regime to small amplitude oscillatory shear (SAOS) regime. Three different cement paste mixes are considered: plain cement, nano-clay blended cement paste and cellulose ether blended cement paste. These three mixes are selected in order to deal with qualitatively different rheological properties.

Cite this publication as follows:
Conte T, Bennacer R, Chaouche M: Thixotropic behavior of cement paste under large amplitude oscillatory shear, Appl. Rheol. 27 (2017) 53914.

Hydrogels are cross-linked polymer networks which are water-insoluble. They are suitable for several technical and biomedical applications due to the ability of some gels to swell and deswell as reaction to external stimuli. Such gels are synthesized and shift from a fluid-like liquid with solved components towards the final polymeric network with gel-like properties. Monitoring and characterizing this process is fundamental on the one hand to understand the chemical and physical behavior and on the other hand to adopt the application and production of such gels. Therefore, this investigation focuses on the characterization of the gelation of a nanocomposite hydrogel system based on PNIPAm with and without mechanical loads applied, using rheology. Measurements are conducted featuring rotational and oscillating rheometry and the results found are compared and evaluated. Furthermore the impact of a strong pre-shear, preventing the gelation, prior to the actual gelation, is investigated. The results found show a strong influence of the applied load as well as of an applied pre-shear on the gelation and furthermore on the mechanical properties of the final hydrogels. Therefore those parameters be taken into account for future investigations as well as for the large scale productions of hydrogels.

Cite this publication as follows:
Nowak J, Barhold C, Kessler C, Odenbach S: Gelation of a Nanocomposite-Hydrogel system and its dependency on mechanical loads, Appl. Rheol. 27 (2017) 52850.

Rheological investigations are reported for pure polyolefin and its clay-nanocomposites to establish structure-properties relationship with respect to filler concentration. Flow birefringence is performed through an engineering geometry slit-die to obtain centerline principal stress difference during elongational flow. The centerline stress profile of clay-nanocomposite revealed additional viscoelastic nature even at low silicate concentrations whereas at the slit entrance no exceptional strain hardening was reported. Effects of higher filler concentrations are further examined during the simple shearing flow where non-terminal low frequency strain hardening only at maximum concentration of clay exhibited pseudo solid like response with improved dynamic moduli. The increase in damping coefficient with increasing clay concentration shows polymernanocomposites are more strain sensitive. The Wagner exponential damping function could adequately describe the timestrain separability at all clay concentrations studied. The results of this investigation reveal that the polymers are time-strain separable at all clay concentrations during elongational and simple shearing flows. But different molecular orientations are possible according to layers alignment along the flow direction.

Cite this publication as follows:
Mudasir M, Ahmed R: An Explanation of Structure-Property Relationships for Polymer/Clay-Nanocomposites through Melt Flow Birefringence and Damping Function, Appl. Rheol. 27 (2017) 53700.

The Couette flow of a model yield-stress fluid with slip at the walls, a 0.12% Carbopol® 940 microgel, was analyzed in this work by simultaneous rheometrical and particle image velocimetry measurements (Rheo-PIV). The Rheo-PIV technique was first tested in the analysis of the Couette flow of a Newtonian fluid and then used to determine the velocity and shear rate distributions of the microgel across gap. A reliable and full description of the different flow regimes occurring in the steady Couette flow of yield-stress fluids with slip at the rheometer walls was obtained, which includes rigid body-like motion at stresses below the yield one, rigid body-like motion and shear flow at stresses above the yield one, as well as pure shear flow once the shear stress at the outer cylinder overcomes the yield value. Slip occurred at both cylinders, which were made up of hydrophobic (inner) and hydrophilic (outer) materials, respectively. The slip velocity values measured at both walls increased along with the shear stress and the trends of these dependencies deviated from the predictions of the hydrodynamic and elastohydrodynamic lubrication mechanisms of slip in the flow of soft deformable particle dispersions [1]. Besides, the yield stress was determined with good accuracy from the velocity profiles, as well as the location of the yielded and non-yielded regions for each flow condition. Finally, the consistency of the obtained velocity profiles was tested by comparison with a theoretical prediction for the Couette flow problem of a Herschel-Bulkley fluid without slip.

Cite this publication as follows:
Medina-Banuelos EF, Marin-Santibanez BM, Perez-Gonzalez J, Rodriguez-Gonzales F: Couette flow of a yield-stress fluid with slip as studied by Rheo-PIV, Appl. Rheol. 27 (2017) 53893.

Cite this publication as follows:
Balan C: The 3rd Romainan Society of Rheology - Summer School of Rheology, Appl. Rheol. 27 (2017) 47.

In primary cementing of an oil well, the oil-based drilling mud (lubricant) is displaced by sequential pumping of an aqueous surfactant 'spacer' fluid, and then the aqueous cement slurry. The cement sets to seal the annular space between the geological formation and the steel wellbore casing. In the displacement process, there will be some intermixing of the fluids. Compatibility between the drilling mud, the spacer, and the cement slurry is necessary to achieve successful zonal isolation. In this study, steady shear and dynamic oscillatory shear were used to investigate the changes in rheology that occur as a result of this inter-mixing. For the steady shear measurements the Herschel-Bulkley model shows good agreement with measured stress-strain data, accurately capturing the yield stress and the plastic viscosity over the range of shear rates from 0.75 to 520 s-1. The vis-coelastic properties, which are related to the microstructure of the slurry were examined by using dynamic oscillatory shear and it was demonstrated that this measurement could be utilized to evaluate the compatibility. Moreover, a close relationship between yield stress and storage modulus was observed, which enabled a correlation relating the steady shear and the dynamic oscillatory results.

Cite this publication as follows:
Choi M, Prudhomme RK, Scherer GW: Rheological evaluation of compatibility in oil well cementing, Appl. Rheol. 27 (2017) 43354.

Cite this publication as follows:
Iyer BVS, Dixit H: Complex Fluids Meeting (CompFlu@Hyd 2016), Appl. Rheol. 27 (2017) 45.

This study compared the flow curve fitting and oscillatory strain sweep methods to determine the yield stresses of Portland cement mortars using a ball measuring system (BMS). The tests were performed in two stages. In the first stage, the responses from a BMS with ball diameters of 8, 12, and 15 mm were compared to those from conventional cone-plate geometry with two different polymer dispersions. In the second stage, thirty-five mortars were prepared with 10 wt% of the cement replaced by silica fume. Five water-to-binder ratios and seven concentrations of a polycarboxylate-based superplasticizer were selected. An 8-mm diameter ball was selected for use in mortar production due to the smaller drag that it produced. The results indicated an increase in the linear viscoelastic region due to a reduction in the water-to-binder ratio and/or an increase in the superplasticizer concentration. In oscillatory tests, the dynamic yield stress was related to the stability of the cement paste and the strengths of the internal links between the cement particles. The flow and Herschel-Bulkley yield stresses result were not statistically different. Therefore, flow stress calculations could be carried out using either of these methods. An amplitude sweep test performed using the BMS may be an alternative method of studying the rheology of cement-based materials.

Cite this publication as follows:
Leon-Martinez FM, Cano-Barrita PFdJ: Yield stress of mortars in rotational and oscillatory shear experiments usinag a ball measuring system, Appl. Rheol. 27 (2017) 45838.

Visco-plasticity characterized by yield stress is an important rheological property of composite propellant suspensions. The yield stress along with viscosity affects various unit operations in propellant processing as well as the quality of final product. The characterization of yield stress of propellant suspensions using direct measurement techniques, such as forced falling ball and slump test is described. The slump test is a simple and quick measurement tool with applicability at processing site whereas forced ball drop is useful for measurement of very high yield stress. The yield stress measurement of propellant suspension of four different compositions with varying particle size and volume fraction using above methods is reported and results are compared with vane geometry of rotational rheometer. Further, the yield stress behavior was studied for the propellant compositions with increasing solid loading. The dependence of yield stress of the studied propellant compositions on the reduced packing fraction φ/φm of solids is established and expressed by a mathematical correlation. In addition, effect of vibration on yield stress was also studied using slump test.

Cite this publication as follows:
Dombe G, Yadav N, Lagade R, Mehilal M, Bhongale C: Studies on Measurement of Yield Stress of Propellant Suspensions using Falling Ball and Slump Test, Appl. Rheol. 27 (2017) 45262.

Rheological properties and the mechanical relaxation behavior of rubbery amorphous sucrose-maltodextrin-sodium citrate systems were studied at room temperature using the small amplitude oscillatory shear test in the frequency range of 0.1 - 150 Hz. The system with high sucrose concentration exhibited viscous-dominant relaxation, while the system with high maltodextrin concentration exhibited elastic-dominant relaxation. The addition of sodium citrate could retard molecular mobility presumably due to its molecular interaction with sucrose rather than with maltodextrin. The technique was capable to detect changes in molecular process even with a small variation in the matrix components. Evidences obtained with scanning electron micrographs suggested the possible effect of sodium citrate to interfere with molecular interactions in the system with high maltodextrin concentration, i.e. the system tended to be more brittle.

Cite this publication as follows:
Sritham E, Gunasekaran S: Rheological and Microstructure Evaluations of Amorphous Sucrose-Maltodextrin-Sodium Citrate Mixture, Appl. Rheol. 27 (2017) 43102.

Cite this publication as follows:
Campo-Deano, Araujo N, Pagonabarraga I, Toschi F: Flowing Matter 2017, Appl. Rheol. 27 (2017) 47.

Shortenings are examples of soft viscoelastic materials with important mechanical functions in baking applications. To fully understand their mechanical functionality, it is essential to correlate material microstructure with rheological behavior. We investigated commercial shortenings designed for various applications, with emphasis on those intended for use in laminated doughs. The microstructure of laminating shortenings was characterized by well-defined crystallites arranged in a layer-like fashion, whereas all-purpose and cake shortenings exhibited more distorted crystallites packed in a more heterogeneous manner. Oscillatory and creep shear behavior demonstrated that all shortenings acted as viscoelastic solids, but laminating shortenings had higher viscosities at .rest. in the linear regime. Recovery in the nonlinear regime showed that laminating shortenings had lower fractional recovery associated with pronounced plastic irreversible deformations. Extrusion tests also in dicated higher viscous dissipation for laminating shortenings. It is argued that the unique layered microstructure is partly responsible for the increased viscous and plastic flow of laminating shortenings, aspects that dictate the ability of these products to endure mechanically demanding processes without apparent catastrophic failure.

Cite this publication as follows:
Macias-Rogriguez B, Marangoni A: Bakery shortenings: structure-mechanical function relations, Appl. Rheol. 27 (2017) 33410.

The hardening of cement pastes occurs due to coagulation/flocculation promoted by the hydration reactions. At this way, depending on the physico-chemical characteristics of the powder, different changes are obtained during the microstructure formation. Thus, as the use of supplementary cementitious materials is rising worldwide, this stage of construction process is being more complex. So, this work was conducted to evaluate the hardening phenomenon of pastes formulated with Portland cements blended with limestone filler (LF) and ground blast furnace slag (BFS). Vicat test, oscillatory rheometry and isothermal conduction calorimetry were used to monitor this transition. Vicat test results indicate different setting times as a function of addition, but no information before these times was obtained. Using isothermal calorimetry was possible to monitor the related changes to the chemical reactions since the first contact with water, and using rheometry, the rate and force of cement particle agglomeration. During the discussion of results will be not presented in depth the results of the three methods, but will be shown that they are complementary and provide a better explanation to the transition from fluid-to-solid behavior, independently of kind of supplementary cementitious materials.

Cite this publication as follows:
Romano RCdO, Maciel MH, Pileggi RG, Cincotto MA: Monitoring of hardening of Portland cement suspensions by Vicat test, oscillatory rheometry and isothermal calorimetry, Appl. Rheol. 27 (2017) 36006.

It has been proposed that hydrogen bonding plays a role in promoting the electrospinnability of some materials. In this work, the significance of non-covalent interactions in the electrospinnability of aqueous sugar solutions (i.e. mono- and disaccharide) was investigated as a function of carbohydrate concentration. The electrospinnability of concentrated aqueous solutions of glucose, fructose, and sucrose was studied by physicochemical and rheological characterization methods, and by subsequently examining the resulting morphology via scanning electron microscopy. The results on the electrospinning of concentrated saccharide solutions indicated the significance of non-covalent interactions on the electrospinning of these systems. Electrospinnability models based on critical concentration and visco-elasto capillary theories were compared with the experimental results. It is shown that visco-elasto capillary theory has the closest correlation with the experimental data. The electrospinnability of highly concentrated saccharide solutions appears to be directly related to the density and intermolecular bonding capacity of the solution.

Cite this publication as follows:
Lepe PGT, Tucker N, Watson AJA, LeCorre-Bordes D, Fairbanks AJ, Staiger MP: The electrospinnability of visco-elastic sugar solutions, Appl. Rheol. 27 (2017) 35703.

Cite this publication as follows:
Cheneler D: Technology of Dispersed Systems and Materials: Physicochemical Dynamics of Structure Formation and Rheology (Uriev), Appl. Rheol. 27 (2017) 10.

Cite this publication as follows:
Cheneler D: Biomedical Applications of Polymeric Materials and Composites (Francis and Kumar), Appl. Rheol. 27 (2017) 9.

Limited information exists in literature regarding the effect of styrene-butadiene rubber (SBR) latexes on rheology and stability of lightweight self-consolidating concrete (LWSCC) intended for repair and precast works. Four series of LWSCC mixtures prepared with various lightweight aggregate (LWA) and SBR concentrations were considered in this project: The free water was adjusted to secure compressive strength of 40 ± 3.5 MPa. The slump flow remained fixed at 700 ± 25 mm, while unit weight varied from 1790 to 2280 kg/m3. Test results have shown that SBR additions lead to reduced concrete flow rate and passing ability. However, improved static stability such as bleeding, segregation, and floating of LWA. The rheological properties including yield stress and plastic viscosity increased for higher SBR additions, reflecting increased cohesiveness resulting from coalescence of water-soluble latexes and binding of cementitious matrix. Three categories of LWSCC classes specified in the European Guidelines were proposed with respect to rheological properties. A Ψ-factor was developed along with series of regression models to predict the combined effect of free water, viscosity-modifier, LWA, and SBR on rheology and stability of polymermodified LWSCC.

Cite this publication as follows:
Assaad J: Rheology and stability of lightweight polymer-modified self-consolidating concrete , Appl. Rheol. 27 (2017) 25807.

The overall objective of this work was to explore the rheology of an advanced performance xanthan gum, which is able to endure the shear and turbulent flows typically found in high-shear mixers or even homogenizers. A further goal was the development of a rheological experimental setup that can be used to gain information about the structural recovery after applying a given shear stress. A fast structural recovery after cessation of shear is essential for a wide range of practical applications. The high zero shear viscosity, strong shear thinning response along with a fast drop of viscosity with shear time and structural recovery support the applications of this xanthan gum as thickening agent and stabilizer. The rheological characterization focused on the influence of xanthan gum concentration (0.15 – 0.40%(m/m)) on the dynamic viscoelastic properties, steady shear and thixotropic behavior, and kinetics of structural recovery.

Cite this publication as follows:
Carmona JA, Calero N, Ramirez P, Munoz J: Rheology and structural recovery kinetics of an advanced performance xanthan gum with industrial application, Appl. Rheol. 27 (2017) 25555.

Graphene/polymer nanocomposites are the latest trends in materials science in the recent years, but the technology of their preparation plays a crucial role in obtaining reliable materials with repeatable and enhanced properties. Up to now, there are many unresolved problems in controlling the dispersion of the graphene filler and the corresponding influence on the properties of the final nanocomposite materials. In the present study, we apply rheological methods for controlling the quality of the graphene dispersion. We prepare and characterize epoxy/graphene nanodispersions with graphene contents varying from 0.05 to 1 wt% and explore the effect of different mixing regimes on the dynamic moduli and viscosity, thus assessing the degree of the dispersion. The rheological percolation threshold and relaxation time spectra are determined, in order to evaluate the internal structure of the nanodispersions. The relaxation spectrum is highly efficient to probe the effects of interfaces and interconnections on the relaxation dynamics of molecules in nanodispersions. Rheological results combined with transmission electron microscopy (TEM) observations confirm that the low frequency dynamic viscosity and moduli strongly increase, with increasing the degree of dispersion due to the exfoliation of graphene sheets. The rheological percolation threshold was found at very low concentration depending from the processing conditions. The weight of the relaxation spectra is strongly shifted to higher values, compared to the neat epoxy resin and this effect is much stronger around and above the rheological percolation threshold.

Cite this publication as follows:
Ivanov E, Velichkova H, Kotsilkova R, Bistarelli S, Cataldo A, Micciulla F, Bellucci S: Rheological behavior of graphene/epoxy nanodispersions, Appl. Rheol. 27 (2017) 24469.

This paper presents an experimental study on the rheological properties of heavy crude oil containing sand to determine the effects of sand size distribution and mass concentration on apparent viscosity, thixotropic behavior, yield stress and viscoelastic properties. The results of these analyses demonstrate that heavy crude oil containing sand shows strong shear-thinning behavior and a certain degree of thixotropic properties. After blending heavy crude oil with sand, the apparent viscosity and the area of the thixotropic loop first decrease and then steadily increase with increasing sand mass concentration. At a fixed mass concentration, apparent viscosity appears to increase with increasing particle size, while yield stress decreases. Moreover, adding sand generally enhances the elastic modulus of heavy crude oil, while the complex viscosity remains slightly less than the apparent viscosity. These results provide new information helpful for removing sand from heavy crude oil.

Cite this publication as follows:
Zhang D, Liu S, Xu j: Rheological properties of heavy crude oil containing sand from Bo-hai oilfield in China, Appl. Rheol. 27 (2017) 24849.

This paper investigates the influence of limestone crushed sand dust (LCSD) on rheological properties of cement mortar based on crushed sand (CS) with different mineralogical nature (limestone and siliceous). A LCSD with a specific surface BET of 1470 m2/kg was used at different content replacement by mass of sand (0, 5, 10, 15, and 20 %). The water-cement ratio (W/C) and the cement content were kept constant for all mixes. The results show that the slump decreased as well as the flow time, the yield stress and the viscosity of mortar increased with the increase in LCSD content. Thus, the mortar based on limestone crushed sand (LS) has a low loss of rheological properties compared with a mortar based on siliceous crushed sand (SS). Yet, for 0 % of LCSD, it was found that the rheological properties are nearly equal for both CSs. The use of superplasticizer (Sp) significantly improves the workability and rheological properties. However, the rheological behavior of mortar has been strongly affected by increasing the volume concentration of CS whereas the effect of CS on fresh mortar presents significantly greater disadvantages compared with rolled sand (RS).

Cite this publication as follows:
Safiddine S, Debieb F, Kadri E, Menadi B, Soualhi H: Effect of crushed sand and limestone crushed sand dust on the rheology of cement mortar, Appl. Rheol. 27 (2017) 14490.

In modern intensive care a comprehensive solution for monitoring the coagulation status or blood clotting problems is currently not available, because fast reliable detection of all bleeding-based disorders (coagulation, fibrinolysis, platelet function) cannot be conducted with a single medical device. This situation calls for a comprehensive technical solution, which we think possible to be solved with a rheological piezo-based system. Rheological measurements provide valuable information on the viscoelastic properties of complex fluids. Here, we compared the performance of a commercially available rheological industrial device using shear stress (Kinexus Pro, Malvern) with that of a piezo-based research measuring system (piezoelectric axial vibrator, PAV) applying squeeze flow to sample fluids. Comparative measurements using different xanthan concentrations (0.1 to 5%) were carried out at 25 and 37 °C. At higher concentrations (1, 2, and 5%), there was an overlapping frequency range and a consistent range of the viscous and elastic shear viscosity for both systems, allowing direct comparisons. Specifically the lower concentrations of 0.1, 0.2, and 0.5% xanthan could be used to assess the possibility of both systems to measure blood coagulation, as those concentrations correspond approximately to the viscosity of human blood. Measurement of blood coagulation was then also tested with the PAV. Measurement repeatability was assessed performing blood coagulation measurements over time at different frequencies (10, 100, 300, and 1000 Hz). The middle frequencies of 100 and 300 Hz provided the most repeatable results for blood. Afterwards the activated clotting time (ACT) was performed with PAV at 300 Hz. The piezo-based measuring system was able to differentiate between various heparin blood concentrations (1, 2, and 3 IU/ml). In this study the reliability, repeatability and limitations of the piezo system were examined. Our initial results showed that the piezo system can be used to assess blood coagulation, but further studies are necessary to confirm these promising results. The aim of a fast, small and reliable point-of-care system may be possible with this type of rheological device.

Cite this publication as follows:
Kunnkattu S, Gross T, Stoppelkamp S, Knieps J, Remmler T, Fennrich S, Wendel HP, Rauch N: Potential of a piezo-based measuring method (PAV) as a haemostasis monitoring system compared to a rotational rheometer , Appl. Rheol. 27 (2017) 13540.

In this paper we investigate the rheological complex behavior of a vase of Fergoug dam which is located in the region Perregaux (Western Algeria) as a function of aging time, shear rate, and temperature. The modified Herschel-Bulkley model is used to fit the stationary flow curves of vase as a function of aging time and the generalized model of Kelvin-Voigt is successfully applied to fit the creep and recovery data and to analyze the viscoelastic properties of vase as a function of temperature. Finally the thixotropic behavior studied at constant temperature is analyzed by using the Herschel-Bulkley model including a structural parameter in order to account for time dependent effect. It is demonstrated that the increase in shear rate induces a restructuring and reorganization of the particles of the vase at the microstructural level.

Cite this publication as follows:
Hammadi L, Ponton A: Rheological investigation of vase of dam: effects of aging time, shear rate and temperature, Appl. Rheol. 27 (2017) 14667.

We study the effect of wall slip on the measured values of the yield stress of magnetorheological (MR) fluids. For this aim we used a rheometer provided with parallel-plate geometries of two types, distinguished by having smooth or rough surfaces. We found that wall slip led to the underestimation of the yield stress when measuring geometries with smooth surfaces were used, and that this underestimation was more pronounced for the static than for the dynamic yield stress. Furthermore, we analysed the effect that both irreversible particle aggregation due to colloidal interactions and reversible magnetic fieldinduced particle aggregation had on the underestimation provoked by wall slip. We found that the higher the degree of aggregation the stronger the underestimation of the yield stress. At low intensity of the applied magnetic field irreversible particle aggregation was dominant and, thus, the underestimation of the yield stress was almost negligible for well-dispersed MR fluids, whereas it was rather pronounced for MR fluids suffering from irreversible aggregation. As the magnetic field was increased the underestimation of the yield stress became significant even for the best dispersed MR fluid.

Cite this publication as follows:
Caballero-Hernandez J, Gomez-Ramirez A, Duran JD, Gonzalez-Caballero F, Zubarev A, Lopez-Lopez MT: On the effect of wall slip on the determination of the yield stress of magnetorheological fluids, Appl. Rheol. 27 (2017) 15001.

Cite this publication as follows:
Kontopoulou M, Heuzey M, Mighri F: Symposium on Rheology of Complex Fluids and Honorary Symposium for Pierre Carreau during the 66th Canadian Chemical Engineering Conference, Appl. Rheol. 26 (2016) 53.

Dispersions of acid hydrophobized hydrolysis lignin in light crude oil, industrial oil, and diesel fuel were found to demonstrate the transition from Newtonian to non-Newtonian behavior with shear-thinning and thixotropy within the increase in lignin concentration. Lignin-in-diesel fuel dispersions were shown to have the smallest apparent viscosity while lignin-in-industrial oil dispersions have the highest one and the sharpest drop of viscosity with shear rate increasing. At the same time, relative viscosity demonstrates the inverse dependence: It is highest for lignin-in-diesel fuel suspensions. Calculation of parameters based on microrheological model of elastic flocs with generalized Casson equation allowed determining of the parameters k and A that describe hydrodynamic interaction between separated particles and their aggregates under flow, parameter FA, characterizing the force impeding the break of aggregates and numbers of particles in the floc for different systems as the dependence of shear stress. The explanation based on a higher affinity of diesel fuel to lignin unlike industrial oil and light crude oil as dispersing medium has been given.

Cite this publication as follows:
Savitskaya T, Reznikov I, Grinshpan D: Rheological Behavior of Lignin Based Dispersions Intended for Composite Fuel Production, Appl. Rheol. 26 (2016) 63476.

Dispersion quality has a large influence on the resulting properties of filled polymers, hybrids and nanocomposites in general. Reducing the van der Waals forces and therefore, matching the refractive index between the filler and the matrix should improve dispersion in hybrid materials. However, in this case the usual light-based techniques cannot be used to assess dispersion quality. In this work, dispersions containing silica nanoparticles and a solvent mixture of 1-butanol and benzyl alcohol were analysed by rheological methods. The refractive index of the solvent was changed by varying the mixing ratio, and thus the effect of index difference on the filler-matrix interaction was investigated. In agreement with theory, a stronger gel network was observed when the refractive index of filler and solvent were matched. If the difference in refractive index of the two materials became too large, particles and solvent interaction was reduced, and agglomerates were formed. This resulted in a weaker gel network.

Cite this publication as follows:
Frohlich KA, Mitrentsis E, Clemens F, Hoffmann B, Michaud V, Graule T: Assessment of the Dispersion Quality of refractive index-matched nanodispersions, Appl. Rheol. 26 (2016) 65050.

The shape and fracture of the free surface frequently limits the measuring range and impedes the use of optical velocimetric techniques in parallel plate and cone plate setups. To prevent this, various kinds of edge guards are often employed. In the present study, we elucidate how an edge guard distorts the steady velocity profile in a parallel plate setup. To this end, we analyzed the velocity field of a strongly shear-thinning fluid, a Newtonian fluid and a set of suspensions via particle image velocimetry in a parallel plate device. Several guard ring sizes were studied. The distortion is described by a simple three parameter model. These parameters are mostly constant for different fluids and suspensions with particle volume fractions below 45%. With increasing radius, the guard ring.s influence approaches a limiting value that we attribute to the influence of the fluid surrounding the gap. Our results indicate a limiting ratio of the difference between plate radius and guard to gap size that should always be exceeded. In the presence of a guard ring, even Newtonian fluids do not exhibit a constant shear rate for most radial distances within the gap. This distortion of the velocity field challenges the simple superposition approach of unguarded device and guard influence that is prevalent in the literature.

Cite this publication as follows:
Pieper S, Schmid H: Guard ring induced distortion of the steady velocity profile in a parallel plate rheometer , Appl. Rheol. 26 (2016) 64533.

Linear low density polyethylene (LLDPE)/poly lactic acid (Pla) blends were prepared via different melt mixing methods. The effects of various blend compositions and two mixing methods on morphological and rheological behavior of the blends were studied. Scanning electron microscope (SEM) was used to investigate morphology behavior of the blends. The rheological studies illustrated that all samples presented shear thinning behavior and the Pla-rich blends exhibited a Newtonian region. It was found from the rheological measurements that the LLDPE/Pla (75/25 w/w) prepared by batch mixer exhibited higher values of storage modulus and complex viscosity, which is in agreement with the morphology results. In addition, using the different mixing methods, significant differences in the morphological results for the LLDPE/Pla (50/50 w/w) blend were observed. Finally, the results showed that the blends prepared by batch mixer exhibited better morphology, higher storage modulus, and complex viscosity.

Cite this publication as follows:
Maryam H, Ali H, Navid F: Influence on compounding methods on rheology and morphology of linear low density polyethylene/poly(lactic acid), Appl. Rheol. 26 (2016) 64746.

Cite this publication as follows:
Duenweg B, Prakash JR: Hydrodynamic Fluctuations in Soft-Matter Simulations, Appl. Rheol. 26 (2016) 51.

Cite this publication as follows:
Fischer P: Fluid dynamics in physics, engineering and environmental applications (Klapp, Medina, Cros, and Vargas), Appl. Rheol. 26 (2016) 10.

Cite this publication as follows:
Cheneler D: Fluids, Colloids and Soft Materials: An Introduction to Soft Matter Physics (Fernandez-Nieves and Puertas), Appl. Rheol. 26 (2016) 8.

By following the path of a liquid bolus, from the oral preparatory phase to the esophagus, we show that a few fundamental concepts of fluid mechanics can be used to better understand and assess the importance of bolus viscosity during human swallowing, especially when considering dysfunctional swallowing (dysphagia) and how it can be mitigated. In particular, we highlight the important distinction between different flow regimes (i.e. viscosity controlled versus. inertia controlled flow). We also illustrate the difference between understanding bolus movements controlled by a constant force (or pressure) and those controlled by a constant displacement (or velocity). We limit our discussion to simple, Newtonian liquids where the viscosity does not depend on the speed of flow. Consideration of non-Newtonian effects (such as shear thinning or viscoelasticity), which we believe play an important part in human swallowing, requires a sound grasp of the fundamentals discussed here and warrants further consideration in its own right.

Cite this publication as follows:
Burbidge AS, Cichero JAY, Engmann J, Steele CM: ''A day in the life of the fluid bolus'': An introduction to fluid mechanics of the oropharyngeal phase of swallowing with particular focus on dysphagia., Appl. Rheol. 26 (2016) 64525.

While shear thickening is a well-known feature of some polymer solutions, its observation in the absence of a clear specific chemical or structural mechanism and at very low rates of shear (shear rate ≤ 0.1/s) in our own data, as well as in several polymer systems in the literature, has prompted further investigation. Using the rheologically-reproducible and commercially available dysphagia product ResourceÒ Thicken Up Clear (produced by Nestle Health Science) as a canonical demonstration fluid, we show that the observation of a local maximum in the steady shear viscosity at very low shear rates can be completely attributed to the sample not having reached steady state conditions, and correspondingly, to the measurement not having been performed in steady simple shear flow. We propose two criteria to ensure equilibration during steady state flow rheological measurements: a substantial increase in the measurement time allotted for each point such that the total material strain accumulated in the sample is allowed to reach shear strain ≤ 5 and/or a stricter convergence criterion of 10 consecutive readings within a tolerance of 1%.

Cite this publication as follows:
Wagner CE, Barbati AC, Engmann J, Burbidge AS, McKinley GH: Apparent shear thickening at low shear rates in polymer solutions can be an artifact of non-equilibration, Appl. Rheol. 26 (2016) 54091.

The main objectives of this paper are to (i) study the rutting performance of asphalt binders modified with styrene butadiene rubber (SBR) copolymer, polyphosphoric acid (PPA) and SBR+PPA, (ii) quantify the percent recoveries R and the nonrecoverable compliances Jnr in the multiple stress creep and recovery (MSCR) test, and (iii) indicate the best formulations in terms of rutting performance. All these formulations have the same high-temperature performance grade in the Superpave® specification (PG 76-xx). The Burgers model was used to fit the laboratory data and the parameter GVwas obtained from the model. The degrees of improvement in the R and the Jnr values after binder modification are higher for the AC+SBR+PPA and the AC+PPA than for the AC+SBR and the results are slightly better for the AC+SBR+PPA. The use of longer creep and recovery times led to increases in the stress sensitivity of the modified asphalt binders and in their rutting potential (higher Jnr values and lower R values) and these effects are more pronounced for the AC+SBR. The AC+SBR+PPA was identified as the best formulation in terms of elastic response and susceptibility to rutting, followed by the AC+PPA and the AC+SBR.

Cite this publication as follows:
InocenteDomingos MD, Faxina AL: High-temperature properties and modeling of asphalt binders modified with SBR copolymer and PPA in the multiple stress creep and recovery (MSCR) test, Appl. Rheol. 26 (2016) 53830.

During mixing of wheat flour doughs, the distribution of the gluten network changes as a result of continuously applied large deformations. Especially gliadin, changes its distribution in the whole network during mixing. It is possible to fundamentally explain the role of molecular changes in more detail using large amplitude oscillatory measurements (laOS) in the non-linear region. Therefore, the purpose of this study is to understand the effect of mixing on the non-linear fundamental rheological behavior of soft wheat flour dough using laOS. Dough samples were obtained at 4 different phases of the Farinograph mixing and laOS tests were done on each of them. laOS tets give in depth intracycle understanding of rheology. All samples showed strain stiffening S and shear thinning T behavior at large strains previously not known in the cereal rheology community. Increasing mixing time (phase 1 to phase 4) and decreasing frequency resulted in retardation in the break of strain stiffening as strain increases. The strain stiffening behavior started to decrease for the dough samples at the 3rd and the 4th phases of mixing. laOS data enabled us to describe the non-linear rheological changes occurring both in the viscous part largely attributed to the starch matrix and elastic part largely attributed to the gluten network components of the soft wheat flour dough under large deformations.

Cite this publication as follows:
Yazar G, Duvarci O, Tavman S, Kokini JL: Non-Linear Rheological Properties of Soft Wheat Flour Dough at Different Stages of Farinograph Mixing, Appl. Rheol. 26 (2016) 52508.

This work presents a simple, scalar model for predicting a nonlinear shear stress response of a viscoelastic fluid in large Amplitude Oscillatory Shear (laOS) experiments. The model is constructed by replacing the viscosity in the well-known Maxwell model by a shear rate dependent viscosity function. By assuming the empirical Cox-Merz rule to be valid, this shear rate dependent viscosity function is specified based on the Maxwell expression for the complex viscosity. We thus construct a particular case of the White-Metzner constitutive equation. Numerical solutions as well as an asymptotic analytical solution of the model are presented. The results, analyzed for higher harmonic content by Fourier transform, are compared to experimental data of a viscoelastic solution of wormlike micelles based on cetyltrimethylammonium bromide. Good agreement is found for low frequencies, where viscous properties dominate.

Cite this publication as follows:
Merger D, Abbasi M, Merger J, Giacomin AJ, Saengow C, Wilhelm M: Simple Scalar Model and Analysis for Large Amplitude Oscillatory Shear, Appl. Rheol. 26 (2016) 53809.

Cite this publication as follows:
Wagner C: Workshop of the German Rheological Society (DRG) and the ProcessNet Section Rheology, Appl. Rheol. 26 (2016) 59.

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Kadar R: Nordic Rheology Conference 2016, Appl. Rheol. 26 (2016) 57.

Cite this publication as follows:
Bulavin L, Lebovka N: 7th International Conference, Physics of Liquid Matter: Modern Problems (PLMMP 2016), Appl. Rheol. 26 (2016) 54.

Cite this publication as follows:
Cheneler D: Viscoelasticity of Polymers: Theory and Numerical Algorithms (Kwang Soo Cho), Appl. Rheol. 26 (2016) 10.

Cite this publication as follows:
Cheneler D: Glassy Metals (K. Russew and L. Stojanova), Appl. Rheol. 26 (2016) 8.

Self-consolidating concrete (SCC) is very sensitive to delays or stoppages between successive lifts during casting, especially given that vibration is prohibited with this highly flowable type of concrete. The investigation reported in this paper seeks to quantify the effect of mixture proportioning on thixotropy along with the resulting effect on interfacial bond strength of hardened material that could result from successive lifts. The suitability of the equivalent mortar phase to simplify testing protocols and appropriately predict SCC properties was given particular attention; the concrete-equivalent-mortar (CEM) mixtures are derived from SCC by eliminating the coarse aggregate fraction and replacing it by an equivalent quantity of sand having equal surface area. Tests results have shown that SCC and CEM mixtures prepared with combinations of increased cement content, silica fume, and/or viscosity-modifier led to higher levels of thixotropy. Yet, the responses determined using SCC were higher by around 1.6 times than those of CEM, given the differences in unit weight and air content between both materials. Good correlations are established between thixotropy and interfacial bond strengths of SCC and CEM mixtures. Key words:

Cite this publication as follows:
Assaad J, Daou Y: Use of the equivalent mortar phase to assess thixotropy of fresh SCC - Prediction of interfacial bond strength between successive placement lifts, Appl. Rheol. 26 (2016) 42759.

This paper describes the effects of irradiation on the rheological and electrical properties of a 7.7% mass fraction of native bovine collagen in water. The radiation dose was in the range of 0-500 Gy. Rheological oscillation measurements were done at temperatures of 10, 20, and 30 C. There was a statistically significant dependency of storage and loss moduli on irradiation dose and oscillation frequency. There was no significant change in the electrical conductivity of collagen during oscillation movements or any dependence on irradiation dose.

Cite this publication as follows:
Landfeld A, Houska M, Skocilas J, Zitny R, Novotna P, Stancl J, Dostal M, Chvatil D: The effect of irradiation on rheological and electrical properties of collagen matter, Appl. Rheol. 26 (2016) 43775.

Rheology of Microfibrillated Cellulose (MFC) suspensions is useful for designing equipment to transport, mix, or process them. Pressure-driven flow behavior is particularly important for MFC suspensions if they are to be pumped, extruded or coated. Herein, we report use of slot and pipe geometries for determination of MFC suspension rheology and compare the results to boundary-driven flows. MFC flow behavior in a slot with varying gaps was studied at mass concentrations of 1, 2, and 3% and up to shear rates of 100 000 s-1. The suspensions exhibited yield stress and were highly shear thinning (pseudo-plastic) with apparent power law indices of 0.22 – 0.43. The shear thinning behavior can be explained by a microstructural picture in which a non-yielding center plug is surrounded by a yielded layer and a fiber-depleted water rich boundary layer.

Cite this publication as follows:
Kumar V, Nazari B, Bousfield D, Toivakka M: Rheology of microfibrillated cellulose suspensions in pressure-driven flow, Appl. Rheol. 26 (2016) 43534.

Former studies show that the coarse particle plays a very important role in the determination of the yield stress of fluid-solid mixtures such as debris flows. The characteristics of the coarse particle in these mixtures include particle size, gradation, shape, and type of material. To assess the influence of these coarse particles on the yield stress the concept of equivalent volumetric solid concentration C is introduced. The equivalent concentration can be derived from the volumetric solid concentration by considering the particle size, gradation, shape, and type of material. laboratory experiments to determine the yield stress of various mixtures were conducted to calibrate the coefficients of these coarse particle characteristics. A yield stress phenomenological expression is proposed using the refined volumetric solid concentration (equivalent concentration), which could be calibrated by the experiments in this study. The validation of this phenomenological expression with data from literature shows good agreements, especially for higher volumetric concentrations of the sediments.

Cite this publication as follows:
Yu B, Chen Y, Liu Q: Experimental study on the influence of coarse particle on the yield stress of debris flows, Appl. Rheol. 26 (2016) 42997.

The measurement and the investigation of the errors in a Couette rheometer have been a topic of considerable interest in many rheometric studies. In the present study, a more accurate predictor-corrector method based on CFD and the analytical solution of the problem is described. Comparing to the previous CFD-based method, in addition to considering the effect of the end parts, the presented correction factors also take into account the effect of the wide gap into a single coefficient. The correction factors are computed for both Newtonian and non-Newtonian fluids in wide and narrow gap rheometry. Results showed that the shear rate distribution across the gap is highly non-linear in non-Newtonian wide gap rheometry. Moreover, for very shear thinning fluid i.e. n < 0.4 in narrow gap rheometry, there is a need to apply correction factor to the calculated fluid properties. Comparing the presented CFD approach and the current approach, the correction factor can be enhanced up to 16% depending on the fluid behavior and the gap distance.

Cite this publication as follows:
Hamedi N, Revstedt J, Tornberg E, Innings F: Application of CFD–based Correction Factors to Increase the Accuracy of Flow Curve Determination in a Couette Rheometer, Appl. Rheol. 26 (2016) 35341.

This paper represents the rheology of screen printing pastes based on BaTiO3 nanopowder. It is found that the pastes are shear thickened fluids with subsequent shear thinning under high shear rates. Different concentrations of plasticizer in organic binder lead to various conformations of ethyl cellulose molecules that influence the type of adsorption between polymer molecules and nanoparticles. The flow loop shows intervals of shear rate corresponding to rheopexy, pseudoplasticity and thixo - tropy. The appearance of rheopexy indicates that the added amount of plasticizer may be insufficient to bind the majority of free functional groups of the polymer and the remaining groups are bound with BaTiO3 nanoparticles forming a strong structural network. But in the case of pseudoplastic structures, the polymer molecule exists in the conformation where almost all free functional groups are bound with the nanoparticle surfaces. The pseudoplastic properties of the system are caused by the structural polymer-polymer links. SEM and optical profilometry of the obtained films shows that plasticization lead to the formation of thin (less than 1 μm) smooth (Ra is equal to the size of individual BaTiO3 nanoparticle) prints.

Cite this publication as follows:
Umerova SO, Dulina IO, Ragulya AV, Konstantinova TE, Glazunova VA: Rheology of plasticized screen printing pastes based on BaTiO3 nanopowder, Appl. Rheol. 26 (2016) 33274.

The rheological behavior of thermoplastic elastomers (TPE) based on 50/50 recycled ethylenepropylene-diene monomer (r-EPDM)/polypropylene (PP) was studied to determine the effect of feeding strategy when preparing these blends using twin-screw extrusion. In particular, small and large deformation characterizations have been performed to better understand the relationships between sample preparation and final properties of the blends. It was found that small changes in blend morphology (particle size and interfacial adhesion) are better distinguished in rheological properties (melt state) under large deformation (laOS and step shear) compared to small deformation (SAOS).

Cite this publication as follows:
Mahallati P, MahiHassanabadi H, Wilhelm M, Rodrigue D: Rheological characterization of thermoplastic elastomers (TPE) based on PP and recycled EPDM, Appl. Rheol. 26 (2016) 33503.

Rheological characterization of high-solid sludge is a fundamental requirement for optimizing the mixing and transport of high-solid sludge during anaerobic digestion in waste water treatment systems. We investigate the time evolution of physicochemical properties and rheological characteristics of high-solid digested sludge with total solids (TS) 15−20 wt.% during anaerobic digestion. A series of experiments are carried out over a period of 26 days during the operation of an anaerobic sequencing batch reactor. In equilibrium flow curves, high-solid digested sludge exhibits shear thinning behavior with a yield stress. Strong viscoelastic behavior is exhibited in the linear and non-linear regimes in dynamic and creep tests. A critical shear stress is found in the equilibrium flow curve, which accounts for the viscoelastic property. To accurately model the flow curves, a piecewise Herschel-Bulkley function separated by the corresponding critical shear rate is proposed. The digestion time plays an important role in determining the rheological behavior. Longer digestion times lead to a decreased yield stress in creep tests, and a decreased viscosity and a reduced critical shear stress in the steady flow curve. In addition, the storage modulus G' and the loss modulus G'' are reduced as digestion proceeds, leading to a shorter linear viscoelastic regime. Moreover, we find that the storage modulus G' varies linearly with the concentration of total organic matter in the sludge, suggesting that G' could be used as a new control parameter for monitoring of the anaerobic digestion process.

Cite this publication as follows:
Zhang J, Haward SJ, Wu Z, Dai X, Tao W, Li Z: Evolution of Rheological Characteristics of High-solid Municipal Sludge during Anaerobic Digestion, Appl. Rheol. 26 (2016) 32973.

Resonance phenomena are discussed in detail. The influence of significant parameters as the moment of inertia and the measuring constants are enlightened and verified with measurements. It is shown that resonance frequencies weekly depend upon the moment of inertia and strongly on the geometrical coefficient of the measuring system. Both parameters form the configuration constant. If a measuring system is replaced, the moment of inertia changes little but the configuration constant changes more. Thus resonance frequencies can be shifted some decades. The comparison between the developed formalism and measurements gives good results for different rheological measuring modes. Even at pronounced resonances measurements provide proper results. The formalism can be used for the simulation of measuring values. However, deformation oscillations along the rotating axis generate resonances of higher order at higher frequencies. These phenomena contribute systematically errors and should be avoided.

Cite this publication as follows:
Stettin H: Resonances in oscillatory rheometry, Appl. Rheol. 26 (2016) 24246.

Removing drilled cuttings from the drilling fluid flowing out of an oilwell is essential for obtaining good drilling conditions. Currently this solids control process is performed by use of shale shakers and vacuum devices. Throughout the last decades, the design and performance of the primary solid control devices have changed significantly. Flow through screens is strongly dependent on the rheological properties of the drilling fluid. Drilling fluids with high extensional viscosity seldom have a very strong gel structure, and are generally not affected equally much by vibrations. This explains why solids control is more difficult using a KCl/polymer water based drilling fluid than using an oil based drilling fluid. This article focuses on describing how the drilling fluid viscous properties alter when being exposed to vibrations like those on primary solids control devices. It is based on theoretical analysis, and rheological studies in the laboratory. The solids control efficiency resulting from using different screen configurations is outside the scope of this article, as this topic requires a higher focus on separation technology.

Cite this publication as follows:
Saasen A, Hodne H: The influence of vibrations on drilling fluid rheological properties and the consequence for solids control, Appl. Rheol. 26 (2016) 25349.

The addition of certain ingredients in conventional concrete is essential for improving rheological properties of this construction material. The effect of limestone and superplasticisers on the hydration kinetics of self-compacting concrete (SCC) was investigated on cement paste scale. These additives interact mostly with cement paste, since aggregates are considered to be inert materials. The understanding of the effect of these mineral and chemical additives on the hydration kinetics of cement paste is the key to design a self-compacting concrete with great properties. Four CEM I 52.5 N Portland Cements, limestone (LS) and one type of superplasticiser (SP) were used in this research. The hydration kinetics were evaluated by monitoring the storage modulus growth and different coefficients of a self-acceleration kinetics equation were used to depict the effect of different concentrations of SP with and without the optimum concentration of limestone (30 %) on the hydration kinetics of cement pastes. It was observed that the rate of hydration increased with the increase in SP concentration depending on the cement used. The addition of limestone in the superplasticised cement paste significantly retarded the hydration kinetics for all four cements. The rheological behavior of self-compacting cement paste was found to be very sensitive to the chemical and physical properties of the cements used.

Cite this publication as follows:
Elmakki R, Masalova I, Haldenwang R, Malkin A, Mbasha W: Effect of limestone on the cement paste hydration in the presence of polycarboxylate superplasticiser, Appl. Rheol. 26 (2016) 25122.

Particle motion in fluid is discussed for one-particle systems as well as for dense suspensions, such as cementitious materials. The difference in large particle motion between larger particles and behaviour of fines (< 125 mm) is explained, motion of one particle is shown by numerical simulation. It is concluded and highlighted that it is the particular motion of the fines that to a large extent contribute to the rheological properties of a suspension. It is also shown why larger ellipsoidal particles do not necessarily contribute to the increase of viscosity.

Cite this publication as follows:
Gram A, Silfwerbrand J, Lagerblad B: Particle Motion in Fluid - Analytical and Numerical Study, Appl. Rheol. 26 (2016) 23326.

Cite this publication as follows:
Fischer P: Traffic Flow Dynamics - Data, Models, and Simulation (Martin Treiber and Arne Kesting), Appl. Rheol. 26 (2016) 11.

Cite this publication as follows:
Jarnstrom L: Highlights from the 24th Nordic Rheology Conference (NRC 2015), Appl. Rheol. 26 (2016) 53.

Natural rubber latex concentrate (NRLC) is an important material used in manufacturing dipped products, yet thorough analysis of their colloidal and rheological properties are still lacking in these areas. In this work, the colloidal and rheological behaviour of the NRLC was studied. The NRLC particle size was in the range of 0.3 to 2 μm with narrow particle size distribution. The response of NRLC to an applied deformation was assessed through rheological experiments which include dynamic oscillation and steady state measurements. A change from liquid-like to solid-like behavior was observed as the volume fraction of the NRLC was increased above 0.48. The plastic viscosity and yield stress of the NRLC increased with increasing volume fraction according to the Bingham equation. The maximum packing volume fraction of the NRLC was found to be 0.75 with a diffused double layer thickness of 14 nm at φ=0.61.

Cite this publication as follows:
Lim H, Misran M: Colloidal and rheological properties of natural rubber latex concentrate, Appl. Rheol. 26 (2016) 15659.

Rheological studies of the ceramic based concentrated titania nanoparticle dispersions showed a clear correlation between molecular structure of the cationic polymers used as dispersants and the viscosity of the slurries. Dynamic viscosity of the electrostatically stabilized alkaline (pH 10.0) dispersions of the bare titania nanopowders with a solid loading of 15 - 25 wt.% was rather high (about 1 Pa.s) and the dispersions exhibited shear-thinning flow behavior. For electrostatic and steric stabilization of the concentrated ceramic nanodispersions of titania in alkaline conditions, the dispersions were treated with cationic comb copolymers differing in charge density and the length of PEO side chains. The dispersions treated by the cationic comb copolymers acted as the Newtonian fluids at low and medium shear rates (< 200 s-1) and showed shear-thickening flow behavior at higher shear rates. Dynamic viscosity of the dispersions with a solid loading of 15 - 25 wt.% treated by the cationic comb copolymers was very low (2 to 30 mPa.s). 1

Cite this publication as follows:
Klimkevicius V, Makuska R, Graule T: Rheology of titania based ceramic nanodispersions stabilized by cationic comb copolymers, Appl. Rheol. 26 (2016) 15199.

DLS Microrheology involves tracking the time dependent motion or mean square displacement of dispersed tracer particles of known size using Dynamic Light Scattering (DLS) in order to determine viscoelastic properties of the dispersion medium. The viscoelastic moduli are calculated using a generalised form of the Stokes-Einstein equation which requires Fourier Transformation of the MSD. An alternative approach for estimating the viscoelastic moduli uses a modified algebraic form of the generalized Stokes-Einstein equation, which employs a power law expression to describe the local change in MSD with time. Since the mean square displacement is linearly related to the creep compliance, it can be shown that the same algebraic approach can also be applied to creep measurements made on a rotational rheometer, giving access to the low frequency moduli in a fraction of the time required for oscillatory testing. Furthermore, the quality of the conversion process can be improved by fitting a Burgers model to the time domain data prior to conversion thus minimising errors associated with local differentiation, which is fundamental to the conversion approach.

Cite this publication as follows:
Duffy JJ, Rega C, Jack R, Amin S: An algebraic approach for determining viscoelastic moduli from creep compliance through application of the Generalised Stokes-Einstein relation and Burgers model, Appl. Rheol. 26 (2016) 15130.

Measurements and modeling of the nonlinear viscoelastic properties of a high viscosity silicone oil (polydimethylsiloxane, PDMS) are reported. laOS test were performed with a high precision rotational rheometer to probe the nonlinear response. The measurements show that the material can be safely considered linear below strain amplitude 1. The viscous Lissajous-Bodwitch curves indicate intracycle shear thinning, whereas the elastic Lissajous-Bodwitch curves indicate intracycle strain stiffening in the nonlinear regime. Secondary loops in some of the measured viscous stress curves are attributed to a non-sinusoidal shear rate signal. A multi-element White-Metzner model is used as a constitutive equation, which accurately describes the laOS data in all measured cases. Based on the extension of the measured data by simulations, nonlinear properties are analyzed both for the elastic and for the viscous part. It is observed that the nonlinearity considerably increases the weight of the higher harmonics in the shear stress signal. It is predicted that the viscous nonlinearity has a maximum around 50 rad/s angular frequency, and that the elastic nonlinearity becomes nearly independent of the angular frequency above 30 rad/s.

Cite this publication as follows:
Kokuti Z, Volker-Pop L, Brandstatter M, Kokavecz J, Ailer P, Palkovics L, Szabo G, Czirjak A: Exploring the nonlinear viscoelasticity of a high viscosity silicone oil with LAOS, Appl. Rheol. 26 (2016) 14289.

Alexei Likhtman, a leading scientist in Theoretical Soft Matter Physics, has died aged 44

Born in 1971 into a family with strong scientific tradition, Alexei was educated in Moscow. He was awarded a Diploma in Physics with honours from the Physics Department of Moscow State University (MGU) in 1994. He remained at MGU for his PhD research, supervised by Professor Alexander Semenov. The topic, his first foray into polymer physics, was the calculation of the extraordinary ordered nanoscale patterns of chemical separation that are spontaneously generated within polymer melts whose molecules contain extended regions of different chemistry but joined together. These systems maintained a lifelong fascination for Alexei, as did the collaboration with the experimental group in Crete that the Russians worked with closely. The relationship with Crete remained strong and close until the end of Alexei's life. A more important lifelong partnership also began in Moscow - it was as students there that Alexei and Katrina met and married in December 1990. The family grew after their daughters Sonya and Asya were born while Alexei was working on his PhD thesis. Helping to look after two little girls however did not stop him from producing a high quality piece of work. Till the end of his days Alexei remained a loving, committed, hands on dad, always reliable and extremely loyal to his family. The family stayed in Moscow for two more years, with Alexei as a Scientific Fellow at Moscow State University, before moving to the U.K, in 1998, where he took up a position as a Research Assistant in the Department of Applied Mathematics at Leeds University, where Semenov, now his colleague, had also moved. That initial one year position marked the beginning of family's long life in the UK

Alexei stayed at Leeds from 1998 until 2007: in 1999 he moved to the Department of Physics and Astronomy, where he worked on theories of fast flow of entangled polymer melts, including theory and simulations of the convective constraint release model, supervised by Professor Tom McLeish, and working collaboratively with Prof. Scott Milner at an ex tended international workshop at the Kavli Institute of Theoretical Physics in Santa Barbara. In 2002, Alexei’s research had developed to the point where he was awarded an Advanced EPSRC Fellowship, which he held from 2002-2005 in the School of Physics and Astronomy. In this period, Alexei worked on developing new models of polymer dynamics, simultaneous description of rheology, neutron spin-echo, neutron scattering, diffusion, dielectric spectroscopy and NMR experiments, the theory of chemical reactions in polymers and computer simulations. This work has been recognized in many ways, including the best paper award of the Journal of Rheology (2006). From 2005-2007 Alexei held his Fellowship in the Department of Applied Mathematics, also as University Fellow, supervising a team of three postdoctoral researchers working on molecular simulations of polymer melts, slip-links model of entanglements and experimental rheology. Although a theoretician, he worked with experimental colleagues in different laboratories and performed experiments himself, learning and questioning every single detail. As a result, he personally developed the most reliable experimental protocol for measuring the flow properties of polymer melts yet found by the Leeds lab. For an experimentalist, it was a treat to interact with Alexei in this context, a unique experience that led to improved experiments. Co-supervising a PhD student, Richard Graham, the two formulated a now-celebrated non-linear but easily-computable mathematical model for the flow of linear polymers of well-defined length (the ROLiE-Poly model).

He worked hard not only on brilliant new theoretical science, but on making this accessible to others. For example, his foresight and energy led to the creation, with long-time colleague Jorge Ramirez, of a free software tool (called REPTATE) that enabled experimental scientists in universities and industry to sort their polymer flow data and compare it quickly and efficiently to theoretical models, greatly accelerating fundamental research and its application.

In May 2007, Alexei moved to the Department of Mathematics and Statistics at the University of Reading, as Professor of Mathematical Physics. There, together with Prof. Mark Matsen, he created a new group of theoretical polymer physics and within a few years had put Reading ‘on the map’. The group focused on the microscopic foundations of the tube theory and using a blend of theory and multi-scale simulation to dig deeper, and with more care, into the underlying physics than any other group in the world. A testimony of Alexei’s brilliance is his unique ability to bridge concepts and methodologies from different fields. He did so in his recent simulation work by using concatenated ring polymers to study polymer entanglements.

Alexei achieved enormous academic distinction, and his achievements came remarkably quickly – testament to his brilliance as a scientist. Several theoretical works on the linear and non-linear viscoelasticity of entangled polymers carry his name, including the famous Likhtman-McLeish model (2002) for slow flows (which was 90% Likhtman) and the GlaMM model (2003) for fast flows (with Graham and Milner). His Advanced EPSRC Fellowship came at the age of 31, and he was appointed Professor of Mathematical Physics in Reading at the age of just 35. Yet while undoubtedly successful himself, Alexei was equally proud of the many achievements of the group he developed. For example, in September this year he spoke glowingly of how two poster prizes out of three available at the Institute of Physics Polymer Physics Biennial Conference were won by post-doctoral researchers from his team. In the same month, he was appointed as the first Mercator Fellow of the Freiburg-Strasbourg-Basel-Mulhouse International Research Training Group on 'Soft Matter Science'. He enjoyed a productive visit to Strasbourg, during which he described himself as "feeling like a PhD student again" (possibly partly due to the position that his former PhD supervisor, Semenov, now holds there!). This is typical of his modesty and enthusiasm.

Alexei was one of those wonderful scientists who remind us that just because something is obvious, doesn't make it true. Alexei would challenge every idea that we had at Leeds – including the ones that we thought were obviously true. But the way in which he demolished your ideas was so kind and so surgically precise that it always felt good somehow. He was a particularly vociferous critic of the bad habit that much of the polymer rheology community had got into, of presenting theory together with data from just one technique, then subtly altering the parameters when data from a different technique was brought into comparison. A wonderful paper from 2005 compared his remarkable ‘slip-link model’ to data on rheology, NMR and diffusion measurements simultaneously. He leaves us a permanent reminder that you learn more from theory when it disagrees with experiment and that an experimentalist should have a good grasp of theory and vice versa.

Alexei was a wonderful colleague, and all those who were lucky enough to work with him benefitted immensely from his enthusiasm, support and wisdom. Alexei was an intellectual powerhouse, a truly curious mind, a wonderfully creative thinker, a brilliant teacher at undergraduate and graduate levels, with academic gravitas way beyond his years, yet completely ap proachable, modest and always friendly in a natural way that charmed anybody who met him. The superb group he built in Reading and the quality of people he brought in reflect his vision and sense of commitment.

He was hugely supportive of those for whom he felt he had a responsibility. His dedication to his PhD students and his research team went well beyond professional duty. He sought to provide a family-like environment for the group, especially supportive for those who were far from home. He presented himself as an exemplary reference figure for all the young people in his group, full of energy and full of life. In this continuous work of hospitality and welcome he was supported by his family, to whom he was utterly devoted as husband and father.

Alexei was so much more than an academic and an intellectual. He truly enjoyed life and always managed to combine professional activities with hobbies and family activities. He did so last summer when he visited friends with his family following a workshop and seminar. He had a passion for so many things ranging from sports (especially swimming and hiking) to photography. A truly happy, free spirited man, full of energy and passion for things he did, he had as infectious a love of life as a tireless desire to find scientific truth. He was a great admirer of nature and outdoors with real care about the world and people around him. He was a great friend, a funny, spirited, yet always serious person, and his daily passionate presence, his enthusiasm for science, his warm friendship, will be sorely missed.

Alexei died on 11 October 2015 following a fall while hiking in Maryland, USA. He is survived by his wife Katrina, and their two daughters, Sonya and Asya.

Cite this publication as follows:
McLeish TCB: Obituary Alexei Likhtman (1971-2015), Appl. Rheol. 25 (2015) 53.

This study is a contribution to the understanding of how rheological properties of a fluid influences swallowing, especially people suffering from swallowing disorders (dysphagia). Our hypothesis was that fluid elasticity contributes to safe and pleasant swallowing. In the present study three food grade model fluids with specific rheological properties were developed and used: a Newtonian fluid with constant shear viscosity, an elastic Boger fluid with constant shear viscosity and a shearthinning fluid which was elastic and had rate dependent shear viscosity. By comparing the swallowing of these model fluids the specific rheological effects could be distinguished. Sensory analysis of the perceived ease of swallowing was performed by a panel of healthy individuals, and by a group of dysphagic patients. The swallowing of the latter group was also characterized by videoflouroscopy and the transit times in the mouth and pharynx were determined. The hypothesis was confirmed by dysphagic patients who perceived swallowing easier for the elastic model fluids. A sensory panel of healthy individuals could not distinguish differences in swallowing, likely because their swallowing functions well and is an involuntary process. Quantitative videofluoroscopic measurements of swallowing transit times for the dysphagic patients suggested that fluid elasticity contributed to easy and safe swallowing, but the effect was not statistically significant due to the large spread of type of swallowing disorder.

Cite this publication as follows:
Nystrom M, Muhammad W, Bulow M, Ekberg O, Stading M: Effects of rheological factors on perceived ease of swallowing, Appl. Rheol. 25 (2015) 63876.

Traditional Maxwell-type models have limitations when applied to the flows of real polymers containing macromolecules and complex microstructures. The main weakness of Maxwell models is the use of relaxation-time spectra that conducts to ill-posed problems in integral functions, and shear-induced relaxation spectrum transformations may lead to non-linearity. In contrast, control theory, which has apparently not been applied in rheology so far, enables modelling without knowledge of relaxation times. This study used viscoelastic constitutive equations derived from control theory and a new polymer fingerprint, which we call the rheologically effective distribution (RED). The study shows that a relaxation-time scheme is not essential to describe viscoelasticity, and applying the RED to computational modelling provides many theoretical and practical benefits, including giving higher accuracy. The proposed model is versatile and presents viscoelastic formulas for shear viscosity and other types of flow. Furthermore, the new model provides explanations for the empirical Cox-Merz rule and a power law behavior, the origin of which is frequently disputed in rheology.

Cite this publication as follows:
Borg T, Paakkonen EJ: Linear viscoelastic model for different flows based on control theory, Appl. Rheol. 25 (2015) 64304.

Nonlinear viscoelastic behavior of bitumen has a determinant effect on the performance of asphalt roads suffering permanent deformation due to traffic loads. Up to know, conventional rheological characterization of bituminous binders, such as the time-temperature superposition (TTS) method, only addresses the linear response of this material without considering the application of high strain amplitudes. The strain-rate frequency superposition (SRFS) is an analogous technique that can experimentally determine the flow behavior from nonlinear oscillatory shear experiments. This method was originally applied to soft materials in order to study the slow relaxation process of particular systems by shifting to higher frequencies the behavior usually found at very low frequencies during conventional measurements. In this work, the feasibility of the SRFS method for assessing the rheological properties of bituminous binders has been evaluated. Oscillatory shear measurements accomplished at different constant shear strain ampliture rates (γ. = ωγ0) and test temperatures allowed analysing the influence of the nonlinear behavior of unmodified and polymer modified bitumen on their viscoelastic responses. The results showed that displacements in the responses due to different strain rates were not so significant as to extend the frequency range further than in conventional measurements. Differences in responses between both techniques were mainly observed for polymer modified binders, especially to high strain amplitudes which usually involve nonlinear behaviour. In addition, master curves obtained with constant strain rates, i.e. taking into account nonlinear response of the material, showed similar results to those constructed by using conventional methods with constant strain amplitude. From these results, a closer comprehension of the large deformations generated in asphalt pavements can be achieved by studying the nonlinear viscoelastic properties of the bituminous binder.

Cite this publication as follows:
Bueno M, Garcia A, Partl M: Applications of Strain-Rate Frequency Superposition for Bituminous Binders, Appl. Rheol. 25 (2015) 65980.

Cite this publication as follows:
Hutter M, Koper G: 7th International Workshop and Summer School on Nonequilibrium Thermodynamics (IWNET 2015), Appl. Rheol. 25 (2015) 61.

The sol-gel transition of homogeneous biocomposites synthesized using tetraethyl-orthosilicate alkoxide, calcium nitrate tetrahydrate and di-ammonium hydrogen phosphate salts as reagents are investigated at the macroscopic scale by small amplitude oscillatory shear measurements and probed locally by passive microrheology at 37 C. Structural evolutions during the sol-gel transition are studied by using Fourier Transform Infrared (FT-IR) analysis. The Young's modulus of the aged gels is measured as a function of time, at room temperature. Moreover the materials are dried, thermally treated and characterized by laser scattering analysis and X-ray diffraction to obtain the particle size distribution and crystallite size respectively and to observe the morphology by Scanning Electron Microscopy.

Cite this publication as follows:
Talos F, Ponton A, Abou B, Chevillot A, Lecoq H, Simon S: Multiscale viscoelastic investigation of silica-calcium-phosphate sol-gel materials, Appl. Rheol. 25 (2015) 63567.

Despite the economic and ecologic importance of pine oleoresins, their rheology remains little explored. In this report we describe rheological properties of oleoresins produced by mature trees of four southern pines native to North America (loblolly, slash, longleaf, shortleaf). Results indicate that these oleoresins are structured fluids that exhibit viscoelastic behavior, but differ in flow behavior. Slash pine oleoresin exhibited Newtonian flow behavior while the oleoresin from the longleaf and shortleaf pines showed pseudoplastic behavior and the loblolly pine oleoresin showed Bingham fluid behavior with a yield stress of about 1.980 Pa. Temperature-dependent viscosities for the oleoresin samples studied were well described by the Arrhenius model, yielding flow activation energies ranging from 153.5 to 219.7 kJ/mol. The viscosity of the slash pine oleoresin sample was found to be less sensitive to temperature than that of the shortleaf or longleaf pine samples. The time-temperature superposition principle was successfully applied to pine oleoresins to show behavior over the temperature range of 25 - 65°C typical for a thermorheologically simple system. Such behavior is consistent with the temperature dependent viscoelastic properties found for these complex fluids, and supports the effective use of rheological evaluations for describing physical properties of pine oleoresins.

Cite this publication as follows:
Belyamani I, Otaigbe JU, Nelson D, Strom B, Roberds J: Rheological properties of southern pine oleoresins, Appl. Rheol. 25 (2015) 53708.

Different rheological methods for yield stress estimation of cement pastes during initial hydration were used and results were compared. These methods include measuring of the hysteresis loop, flow curves (recalculated to the same time of hydration) and large amplitude oscillating strain (laOS). Experiments were performed with four Ordinary Portland Cements from one manufacturer, produced at different factories and one polycarboxylate acid based superplasticiser (SP). The yield stress values obtained by constructing flow curves is the only method which gives information about the evolution of the rheological properties, reflecting structure evolution of cements pastes. It was shown that the yield stress values established by the laOS method and that calculated from the flow curves are similar while the values found from the downward part of the hysteresis loops are much lower. Differences in the yield stress values obtained by various methods are related to the different states of the material corresponding to the kinetics of hydration. The hysteresis loops provide information about thixotropic characteristics of the material including characteristic times of rebuilding and the rate of yield stress evolution of cements. The rheological properties are very sensitive to the chemical and physical differences of the cements and could be used for their characterization.

Cite this publication as follows:
Mbasha W, Masalova I, Haldenwang R, Malkin A: The yield stress of cement pastes as obtained by different rheological approaches, Appl. Rheol. 25 (2015) 53517.

Magnetic nanoparticles suspended in suitable carrier liquids can be adopted for use in biomedicine. For this to be achieved, the biocompatibility of these ferrofluids needs to be ascertained. In cancer treatment, potential applications currently under investigation include, e.g. drug targeting by using magnetic fields and the destruction of diseased cells by applying alternating magnetic fields, which cause heating of magnetic nanoparticles. To enable the use of ferrofluids in the actual biomedical context, detailed knowledge of the flow characteristics is essential to ensure safe treatment. From ferrofluids used in the engineering context, a rise of viscosity when a magnetic field is applied - the magnetoviscous effect - is well known. This effect, which leads to an increased viscosity and profound alteration of a fluid's rheological behaviour, has also been demonstrated for biocompatible ferrofluids used in the aforementioned applications. In biomedical applications, ferrofluids will be diluted in the blood stream. Therefore, the interaction between whole blood and the ferrofluid has to be investigated. This is the focus of the current experimental study, which makes use of two different ferrofluids diluted in sheep blood to gain a deeper understanding of the fluid mixtures primarily regarding the relative change in viscosity if an external magnetic field is applied. The results demonstrate a strong interaction between blood cells and structures formed by the magnetic nanoparticles and show a high deviation of results compared to ferrofluids diluted in water. These findings have to be taken into account for future research and applications of similar biocompatible fluids to guarantee safe and effective use in living organisms.

Cite this publication as follows:
Nowak J, Nowak C, Odenbach S: Consequences of sheep blood used as diluting agent for the magnetoviscous effect in biocompatible ferrofluids, Appl. Rheol. 25 (2015) 53250.

An experimental and numerical investigation of the rotational rheometry of yield-stress materials is performed, using waterbased Carbopol dispersions. The flow and fluid characterization in different rheometer geometries, namely the smooth Couette, the grooved Couette, and the vane-in-cup are analyzed. The bi-dimensional flow governing equations are solved numerically, using the finite volume method and Fluent software (Ansys Inc.). The viscoplastic behavior of Carbopol dispersions is modeled using the Generalized Newtonian constitutive equation with the regularized viscoplastic viscosity function proposed by de Souza Mendes and Dutra [1], herein called SMD function. The flow pattern and the presence of apparent wall slip in rheometric measurements of yield-stress materials are investigated and discussed.

Cite this publication as follows:
Marchesini FH, Naccache MF, Abdu A, Alicke AA, deSouzaMendes PR: Rheological characterization of yield-stress materials: Flow pattern and apparent wall slip, Appl. Rheol. 25 (2015) 53883.

We provide methodologies to characterise the rheology of ultra-low volumes of polymer solutions and biological fluids (10 - 100 μL) on a rotational rheometer. The technique utilises a parallel plate geometry with narrow gaps of 20 - 100 micrometers, which is an order of magnitude less than conventional methods. Despite the complications these gaps present, the use of appropriate protocols ensures reliable and accurate rheological characterisation of fluids, including shear-dependent viscosity, normal stresses and linear viscoelasticity. This rheological technique.s usefulness is further demonstrated by showing how the rheology of hyaluronan solutions evolve during fermentation. The intrinsic viscosity of the hyaluronan macromolecule is determined using less than 100 μL of solution extracted directly from the bioreactor, and this is used to provide a reasonable indicator of its molecular weight as it develops during the fermentation process. The ability to measure rheology of ultra-low volumes has applications in the characterisation of biological fluids and high value macromolecules, as well as generally in biotechnology and nanotechnology research fields.

Cite this publication as follows:
Boehm MW, Shewan HM, Steen JA, Stokes JR: Illustrating ultra-low-volume rheology on a conventional rheometer: Charting the development of hyaluronan during fermentation, Appl. Rheol. 25 (2015) 55609.

Suspensions of SiO2 microspheres in glycerine exhibit drastic shear-thickening behavior under steady shear and dynamic oscillatory shear test. The rheological behavior of suspensions agrees with the modified Cox-Merz rules as the dynamic oscillatory rheological behavior at low frequency could be reasonably interpreted in terms of the steady shear behavior. As new insight, the effect of shear history and the relaxation on the rheological behavior was investigated in detail. The result showed that under continuous shear, the viscosity decreases after a 'pulse': The degree of decrease is directly proportional to the shear rate. Similar phenomenon is also found under the continuous stress and dynamic oscillatory shear rate sweep. The shear history shows a non-negligent effect on the rheological behavior, the suspensions with higher viscosity show a lower viscosity under the same shear rate. Moreover, the relaxation time of suspensions shows the direct dependency on the initial viscosity, while the volume fraction of suspensions also affect the relaxation time. For more enlapsed times, also longer relaxation times are needed for the suspensions with lower volume fraction and higher initial viscosity.

Cite this publication as follows:
Chen Y, Li X, Zeng G, Liu W: The influence of continuous shear, shear history and relaxation on the rheological behavior of SiO2/glycerine suspensions, Appl. Rheol. 25 (2015) 44806.

There is often a necessity to measure, or at least estimate, true viscosity values using non-standard measuring systems on a rotational rheometer. This may be to replicate a mixing or manufacturing process on a lab scale, to keep a sample dispersed and uniform during a measurement or to measure some rheological property that would be difficult or impossible with a standard configuration. Such measurements can be made easily enough, but without a process for converting torque to shear stress and angular velocity to shear rate only these raw data variables can be reported. In this paper a simple and novel empirical method for determining strain/strain rate C1 and stress C2 constants for non-standard measuring systems on a rotational rheometer is presented. This method uses relative torque measurements made with a Newtonian and non-Newtonian material and their corresponding power law fitting parameters to determine C1 and C2 using a non-linear regression analysis. Equilibrium flow curves generated for two non-Newtonian fluids using two non-standard mixing geometries show very good agreement with data generated using a standard cone and plate configuration, therefore, validating the approach.

Cite this publication as follows:
Duffy JJ, Hill AJ, Murphy SH: Simple method for determining stress and strain constants for non-standard measuring systems on a rotational rheometer , Appl. Rheol. 25 (2015) 42670.

We present a numerical study of the film casting process, with a focus on the effect of the draw ratio on the swelling of the extruded sheet. So far, studies regarding film casting have dealt mainly with the phenomenon of neck-in and have neglected swelling of the material as it emerges from the die lips. Knowledge of the amount of swelling is important for accurate determination of the effect of stretching and orientation phenomena. The problem is tackled by studying the gap-wise swelling of the sheet or film as it emerges from a wide rectangular die and is subsequently drawn down under different draw ratios. The material is treated as viscoelastic by utilizing the Linear Phan Thien-Tanner (LPTT) model. Newtonian simulations are also carried out. A decoupled iterative algorithm is used for the determination of the shape of the extruded sheet, based on the fact that the sheet.s surfaces belong to streamlines. Our results are in qualitative agreement with results in the literature, with the latter being limited in number and available mainly for the (similar) process of fiber melt spinning.

Cite this publication as follows:
Polychronopoulos ND, Papathanasiou TD: A study on the effect of drawing on extrudate swell in film casting, Appl. Rheol. 25 (2015) 42425.

The relative intensity and phase of the third harmonic, I3/1 and Φ31, deduced from Fourier Transform analysis of large Amplitude Oscillatory Shear (laOS ) experiments were used to differentiate the effect of irradiation and the effect of multiwalled carbon nanotubes (MWCNT) concentration in PP/MWCNT nanocomposites. Alternatively, studies of elastic and viscous non linearities that give shear thinning and thickening or strain softening and hardening were carried out for the same purpose. Using both methods to analyse laOS data, the conclusion was the same: The influence of MWCNTs is noticed at low/intermediate γo strains (10 - 100 %), whereas the effect of irradiation is rather observed at strains above 100 %. This marks a difference with respect to small amplitude oscillatory flow measurements, which are not valid to distinguish between the respective rheological effects of irradiation and MWCNT in polymer nanocomposites. SEC-MALLS-IR-VI analysis was used to determine the long chain branching degree &lambda; of irradiated polypropylene, but this technique is very difficult to be applied for nanocomposites. Face to this shortcoming, an empirical correlation between &lambda; and the value of the I3/1 plateau when γo tends to infinite, found for irradiated neat PP, was used to evaluate the long chain branching degree of nanocomposites.

Cite this publication as follows:
Fernandez M, Huegun A, Munoz ME, Anton S: Nonlinear oscillatory shear flow as a tool to characterize irradiated polypropylene/MWCNT nanocomposites, Appl. Rheol. 25 (2015) 45154.

The creep and recovery of asphalt modified with Elvaloy 4170 and polyphosphoric acid were studied at low temperatures, by inductive phenomenological methods. Two models of the tensile compliance function were investigated. Both models were derived from the linear viscoelastic retardation spectra and successfully used for the description of the creep and recovery tests in the studied asphalt binders. large effects due to oxidative aging in a rolling thin film oven were found from the recovered compliance function recorded in a bending beam rheometer at a temperature of - 20 C. The studied compliance function models worked well at higher and lower temperatures in creep and recovery experiments on conventional and modified asphalt binders for both shear and tensile creep.

Cite this publication as follows:
Hampl R, Vacin O, Jasso M, Stastna J, Zanzotto L: Modeling of tensile creep and recovery of polymer modified asphalt binders at low temperatures, Appl. Rheol. 25 (2015) 34675.

Build-up of cement-based suspensions is a complex phenomenon affected by the mixture concentration and testing parameters as well as the shear history. Accurate measurements of build-up rely on the efficiency of the applied pre-shear regime to achieve an initial defined and dispersed structure to eliminate the shear history. This can therefore enable understanding mechanisms of build-up and quantifying the structuration of cement suspension from a reproducible dispersed state. Dispersing efficiency of various disruptive shear techniques, including rotational, oscillatory, and combination of both was evaluated. The initial and final states of suspension.s structure were determined by applying small-amplitude oscillatory shear (SAOS). Test results showed that oscillatory shear has a greater effect on dispersing concentrated cement suspension than the rotational shear. Furthermore, the increase in shear strain in oscillatory technique enhanced the breakdown of suspension.s structure until a critical point, after which thickening effects dominate. An effective dispersing method is then proposed. This consists in applying a rotational shear around the transitional value between shear-thinning and shear-thickening followed by an oscillatory shear at the crossover shear strain and high angular frequency of 100 rad/s.

Cite this publication as follows:
Mostafa AM, Yahia A: Performance evaluation of different rheometric shearing techniques to disperse concentrated cement suspension, Appl. Rheol. 25 (2015) 34337.

Organic nanoparticles of poly(styrene-co-maleimide) or SMI were synthesized in aqueous dispersion with a maximum concentration of 35 wt.% and are favorably applied in industrial coating processes. In order to evaluate the further processability and flow behavior of these nanoparticle dispersions, general rheological characterization under creep, oscillatory and rotational testing was done by applying various shear stresses, shear rates and frequencies on an air-bearing cylindrical rheometer. Creep tests at different stresses show that the nanoparticle dispersions behave like a viscous material. The crossover of G' and G'' according to oscillatory experiments also demonstrates a transition to viscoelastic behavior at high frequency. The sensitivity of shear-viscosity behavior to concentration and temperature of the dispersions has been evaluated. In parallel, the influences of gap size, repeatability and water evaporation have been statistically evaluated and could be successfully controlled. By comparing oscillatory and rotational rheometry data, flow curves under low shear rates were reconstructed.

Cite this publication as follows:
Taheri H, Stanssens D, Samyn P: Rheological characteristics of a waterborne organic nanoparticle dispersion, Appl. Rheol. 25 (2015) 32889.

This paper reports the rheological behavior of swelled and mineralized hydrogel prepared using polyvinylpyrrolidone (PVP) and carboxymethylcellulose (CMC) hydrogel as base polymer. Herein, the bio-mineral calcium carbonate (CaCO3) was incorporated into the hydrogel using simple liquid diffusion method. The morphology of the swelled and mineralized hydrogel was analyzed through scanning electron microscopy. Further, the normalized time of absorptivity was identified from the time dependent absorptivity behavior of calcite and water filled PVP-CMC hydrogel. The effect of the biomineral (CaCO3) and water on the dynamic viscoelastic properties, after penetrating inside the hydrogel matrix has been evaluated. The frequency sweep at 1 and 10 % strain and also strain sweep measurement were performed to determine the frequency and strain dependent viscoelastic moduli G' and G'' of both swelled and mineralized hydrogel. At higher strain the both moduli showed significant change over wide range of angular frequency region and the nature of mineralized polymer composites (MPC) turned from elastic to viscous. Based on the observed basic properties, MPC (calcite based polymer composites) can be recommended for the treatment of adyanamic bone disorder and water swelled hydrogel can be acclaimed as a scaffold for burned wound dressing.

Cite this publication as follows:
Shah R, Saha N, Kitano T, Saha P: Influence of strain on dynamic viscoelastic properties of swelled (H2O) and biomineralized (CaCO3) PVP-CMC hydrogels, Appl. Rheol. 25 (2015) 33979.

Measuring the rheological properties of multi-component (and multi-phase) systems meets with many special problems which are absent in flows of homogeneous materials. Such complex fluids have inherent structure and all the peculiarities of their behavior are determined by stress-induced temporal-spatial structure rearrangements. This paper is a review devoted to the physical origin and classification of problems encountered in the flow of multi-component materials. Stress-driven phenomena can be related to phase transformations (the formation of a new phase in polymerization, crystallization, amorphous phase separation), molecular and structure orientation, and various forms of self-organization. Some of these time effects are considered to be thixotropic phenomena. Thixotropy of multi-component matters leads to absence of an upper Newtonian plateau, time (rate)-dependence of yield stress and the layered flow in the range of high shear rates. The flow of such matters can lead to the formation of spatially divided structures with different properties and displacement of structures at the macroscopic level that excludes traditional measures of their rheological properties. In addition, the flow of multi-component systems is accompanied by the appearance of anisotropy of their properties. It is emphasized that the stressdriven evolution of rheological properties are not taken into account in the existing widely used constitutive equations.

Cite this publication as follows:
Malkin AY, Kulichikhin V: Spatial-temporal phenomena in the flows of multi-component materials, Appl. Rheol. 25 (2015) 35358.

The core of activated sludge monitoring lies in the biological analyses. Anyway, the knowledge of sludge physical characteristics is crucial for a proper management of WWTPs (Waste Water Treatment Plants). One of these physical features is viscosity that, notwithstanding its valuable role has not yet become a routine analysis. This study examined the evolution of rheological properties of two sludges alongside the .purification route. (from the biological reactor up to the sludge treatments). It could been shown that sludges behaved like non-Newtonian fluids and dry solids content strongly affected viscosity values, which reached relatively high values. Microscopic observation of flocs was carried out. Both the sludges revealed similar features, in particular an over-proliferation of filamentous bacteria. This work showed how rheological measurements can be a tool to obtain information on microbiological composition of activated sludge and how it could be related to settleability properties.

Cite this publication as follows:
Papa M, Pedrazzani R, Nembrini S: Should rheological properties of activated sludge be measured?, Appl. Rheol. 25 (2015) 24590.

As a fundamental rheological property, shear yield stress is used to assess the flowability of suspensions. Slump test is a cheap and quick experiment which is commonly used to estimate shear yield stress on-site. It has been generally believed that, cylinder height to diameter ratio and lifting velocity has no effect on the slump test results. In this work, the sensitivity of the slump test to the height to diameter ratio and lifting velocity of cylinder was investigated. Projections on the top surface of suspension column after the slump test were also analyzed. Results indicated that, the effect of cylinder height to diameter ratio is negligible in the low range of shear yield stress, while it is remarkable in the high range. It was deduced that, using a cylinder with dimension ratio in the range of 0.83 to 1.15 is more reliable. Furthermore, it is shown that the lifting velocity of cylinder has a significant effect on the results. A high lifting velocity could introduce a great error in estimation particularly in a large height to diameter ratio.

Cite this publication as follows:
Garmsiri M, HajiAminShirazi H, Yarahmadi M: An analysis of the influence of cylinder dimension ratio and lifting velocity on the slump test results, Appl. Rheol. 25 (2015) 23416.

Maximizing oil recovery from current reserves is becoming more important as global usage continues to rise. In this paper, we present the development of two microfluidic sandstone devices of high complexity and differing permeability capable of quickly and inexpensively testing the oil recovery performance of fluids with different rheological properties. Our initial baseline experiments were performed by displacing oil with water over a wide range of flow rates. Next, a commercially available fluid thickener, Flopaam 3630, was tested. Flopaam is both shear thinning and viscoelastic and was found, due primarily to its large viscosity, to recover more oil than the water and increase the oil recovery substantially in both the larger and smaller permeability microfluidic sandstone devices. Finally, a shear-thickening nanoparticle solution was studied. The shear-thickening solution was designed to thicken at a shear rate of about 10 s-1, a typical shear rate in the oil reservoirs. These shearthickening fluids were found to be an excellent enhanced oil recovery fluid, especially when the shear rates within the microfluidic sandstone devices closely matched the shear rates associated with the shear-thickening regime. For the high permeability sandstone devices tested, when the appropriate choice of shear-rate-dependent viscosity was used to define a capillary number, the oil recovery obtained from both the Newtonian and non-Newtonian fluids were found to collapse quite well onto a single master curve. This, however, was not the case for the lowest permeability sandstone devices where the increased complexity was found to negatively affect the performance of the viscoelastic fluid when compared to either the Newtonian or the shear-thickening fluid. Finally, it was shown that these oil recovery results are insensitive to whether a single-stage recovery process or a more complex two-stage recovery process that starts with an initial water flood followed by a flood with a secondary fluid were used.

Cite this publication as follows:
Nilsson MA, Rothstein JP: Effect of fluid rheology and sandstone permeability on enhanced oil recovery in a microfluidic sandstone device, Appl. Rheol. 25 (2015) 25189.

Viscosity reduction of aqueous kaolin suspensions by conventional additives (deflocculation) is studied, using standard viscosity measurements. Apparent viscosity at 100 s-1, and flow behavior index n give complex information about changes of viscosity and flow character of deflocculated suspensions. Several widely used deflocculants - electrolytes and polyelectrolytes - are tested in a wide range of concentrations. The optimum concentrations of these deflocculants, which result in minimum apparent viscosity of suspension, are found. Sedimentation stability of deflocculated suspensions is monitored. Inorganic electrolytes are found to be more effective in viscosity reduction. On the other hand, low-molecular-weight polyelectrolytes produce more stable final suspensions.

Cite this publication as follows:
Penkavova V, Guerreiro M, Tihon J, Teixeira JAC: Deflocculation of kaolin suspensions - The effect of various electrolytes, Appl. Rheol. 25 (2015) 24151.

Studies have shown that rheology of asphalt mastic plays an important role in pavement performance, specifically for the case of recycled asphalt pavement (RAP) mastics which contains mostly aged binder. This study determines the rheological properties of RAP mastics and a comparison is conducted with the no-RAP binder. Influence of RAP fines on rutting and cracking performances is also studied. A performance grade PG 70-22 binder is mixed with varying percentages (10, 20, and 40%) of crushed stone (no-RAP) and RAP fines to prepare mastics. Dynamic Shear Rheometer testing is conducted to measure the complex shear modulus G*, and phase angle δ of these mastics at high and intermediate temperatures through frequency sweep. Bending Beam Rheometer test is conducted at low temperatures (-10 C, -16 C, and -22 C) to measure the stiffness S and relaxation (m-value). Direct Tension Test is conducted to compute the failure strain at -22 C. Results show an improvement in rutting with the addition of RAP fines (increase in G*/sinδ), a decline in low-temperature cracking resistance (increase in S). Addition of RAP fines up to 20% does not affect the fatigue resistance of the mastics adversely. However, fatigue cracking of 40% RAP mastic is shown to be high (increase in G*sinδ). 40% RAP mastic shows a smaller failure strain than the virgin binder and 40% no-RAP mastic, which indicates that mastics containing RAP are more susceptible to low-temperature cracking. To characterize the viscoelastic properties of the RAP mastics, the G* master curve is constructed at 22 C reference temperature. RAP mastics. master curves follow the sigmoidal function irrespective of %RAP in mastics. However master curves do not show any significant difference between RAP mastics and no-RAP mastics.

Cite this publication as follows:
Mannan UA, Islam M, Weldegiorgis M, Tarefder R: Experimental investigation on rheological properties of recycled asphalt pavement mastics, Appl. Rheol. 25 (2015) 22753.

For developing a new composite material owning shear-thickening characteristic, the rheological behaviors of nano-sized precipitated calcium carbonate (PCC) particles with irregular sharp in glycerine were investigated systematically by means of steady and dynamic rheometry. The results showed that the concentrated PCC suspensions exhibit a strong shear-thickening behavior under both steady and dynamic oscillatory shear when the volume fraction of PCC above the threshold (about 41 %). In steady shear tests, the critical shear rate decreases and the maximum viscosity in shear thickening region increases dynamically with the increase of volume fraction. While, for suspensions with different volume fractions, the similar critical stress for the onset of shear thickening is found. In dynamic strain sweep at different fixed frequencies, with the increase of fixed frequency, the complex viscosity of suspensions decreases slightly, while the critical strain for shear-thickening shifts to lower value. The dynamic oscillatory rheological behavior of suspensions at low frequency (w < 100 rad/s) could be reasonably interpreted in terms of the steady shear behavior. For the suspensions with same volume fraction, it was interestingly found that the critical dynamic shear rate equaled to the product of critical strain and frequency could agree well with the critical shear rate in steady shear. Moreover, the rheological behavior of PCC suspensions shows excellent reversibility and reproducibility.

Cite this publication as follows:
Chen Y, Xu W, Xiong Y, Peng Y, Peng C, Ou Z: Shear-Thickening Behavior of Precipitated Calcium Carbonate Particles Suspensions in Glycerine, Appl. Rheol. 25 (2015) 12466.

An elasto-visco-plastic model of the Cauchy stress is proposed for gluing solution of railway ballast, with an asymptotic timedependent viscosity accounting for the anti-thixotropic and shear-thickening features. Flow characteristics and time-dependent solidification of the gluing solution in the multiconnected conducts spanned by the gravels, accomplished by the algorithm in generating a ballast consisting of convex octahedral grains, are simulated by using the ANSYS™ package. While different vertical penetrations of the gluing solution can be achieved by using different characteristic times scales of the asymptotic time-dependent viscosity, the lateral extension is rather limited and local. Pouring gluing solution into ballast tends to create more concrete adhesion between the gravels vertically, while concrete lateral adhesion can be obtained by spreading gluing solution onto ballast. The present study provides an integrated method for the estimation of the gluing solution distribution in a ballast, and for optimal layout of the gluing solution arrangement a priori gluing practice.

Cite this publication as follows:
Fang C, Lee Y, Kuo C, Lin Y, Kuo C: Anti-thixotropic non-Newtonian fluid in complex conduct: gluing process simulation of railway ballast, Appl. Rheol. 25 (2015) 14381.

A Sentmanat Extension Rheometer represents one out of a few experimental devices for the measurement of elongational viscosity of polymer melts. However, the appropriateness of this technique for individual polymer materials is not sufficiently apparent and in some case is disregarded or ignored. The proposed visualization technique is based on imprinting painted pattern from the inner surface of the studied polymer samples onto the counter-rotating drums. Digitization of the imprinted pattern gives a possibility to evaluate a degree of sagging, incorrect fixing of rectangular polymer samples to the drums, possible appearance of sample inhomogeneity (variance in thickness, bubbles, etc.). The presented visualization technique is demonstrated using branched LDPE Escorene. Two various imprinted patterns are applied. First, the upper and lower contours are charted on a prepared sample with the aim to determine the sample shapes during stretching and to compare them with the theoretical ones. Second, the inclined rectangular grid pattern is charted for evaluating possible inhomogeneity of the sample.

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Pivokonsky R, Filip P, Zelenkova J: Visualization of elongation measurements using an SER universal testing platform, Appl. Rheol. 25 (2015) 13636.

The rheological behavior of oilfield surfactants (Aromox™ APA-T and APA-TW) at various concentrations was studied using steady shear and dynamic testing. The results showed that the solutions exhibit non-Newtonian behavior at all concentrations, with their rheological character influenced by the temperature and ionic content of the base fluid. Temperature was observed to have a significant effect on viscosity and dynamic data. The apparent viscosity at different temperatures could be reduced to a single master curve using horizontal and vertical shift factors. However, satisfactory scaling could not be attained for the dynamic or viscoelastic data. Molecular scaling using characteristic time for data at different concentrations proved unsuccessful due to the strong non-Newtonian character of surfactant solutions. Scaling relations between rheological parameters and concentration indicated the presence of long micelles in APA-T solutions. APA-TW solutions, on the other hand, contained branched micelles.

Cite this publication as follows:
Dosunmu IT, Shah SN: Steady shear and dynamics properties of drag reducing surfactant solutions, Appl. Rheol. 25 (2015) 12539.

Cite this publication as follows:
Baldi F, Ferri D, Lapasin R, Semenzato A: XIII Italian Conference on Rheology 2014, Appl. Rheol. 24 (2014) 49.

Measurements and modeling of rheological properties of a high viscosity silicone oil (polydimethylsiloxane, PDMS) at high frequency are reported. The linear viscoelastic properties are measured by small amplitude oscillation shear (SAOS) tests with a rotational rheometer. Furthermore, Diffusing Wave Spectroscopy (DWS) is used, which expands the angular frequency range of the measured loss and storage moduli up to 105 rad/s, in a temperature range of 20 - 70 C. Good agreement between both methods is found in the overlapping frequency region, especially at higher temperatures. The DWS data show that the elastic modulus stays dominant and increases with frequency, without a second cross-over point up till 108 rad/s. Flow curves, measured with rotational and with capillary rheometry up to a shear rate of 7.6 × 104 s-1, show shear thinning behavior, which implies nonlinear viscoelasticity. Comparison of the dynamic and complex viscosity shows that the Cox-Merz rule is valid in a frequency range spanning six orders of magnitude. A multi-element White-Metzner model is proposed as a constitutive equation, which accurately describes the nonlinear viscoelastic properties, including the decrease of the loss and storage moduli during amplitude sweeps in oscillatory shear measurements.

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Kokuti Z, vanGruijthuijsen K, Jenei M, Toth-Molnar G, Czirjak A, Kokavecz J, Ailer P, Palkovics L, Volker AC, Szabo G: High-frequency rheology of a high viscosity silicone oil using diffusing wave spectroscopy, Appl. Rheol. 24 (2014) 63984.

The knowledge of enzymatic activity is necessary in many industrial processes. The common measurement techniques are time-consuming and therefore cost-intensive. Measurements of viscosities are a promising approach as a fast and cheap testing method. The major challenges are to find a suitable substrate with Newtonian flow behavior throughout the whole testing range as well as a correlation between viscosity of the solution and the decomposed mass. Water based gelatinebuffer- system as substrate is tested extensively regarding the dependence on different solvents, pH-values and gelatine batches. All viscosity measurements are performed with a rotational viscometer. It is shown that the gelatine-buffer-system is independent of the given parameters and found to fulfill the said requirements. A correlation model based on the Martin equation and necessary assumptions are presented. The required parameters intrinsic viscosity and Martin parameter can be derived by few measurements with little effort. The digesting enzyme Trypsin is used as model enzyme in the degradation experiments. The enzyme concentration is varied and the decrease of the viscosity is measured. A dependency between the enzyme concentration and the enzymatic activity or respectively the viscosity decrease is observed.

Cite this publication as follows:
Sellerberg M, DiBartolo D, Oberrecht J, Tiller J, Walzel P: Viscometric measurement of protease activities on gelatine substrate, Appl. Rheol. 24 (2014) 62660.

Fruit juices concentrated by osmotic distillation are characterized by higher organoleptic and sensorial properties than those of juices concentrated by thermal evaporation as confirmed by several research studies. On the other hand, no literature is readily available about the rheological characterization of juices concentrated by osmotic distillation. This work aimed at investigate the rheological behavior of the concentrated blood orange juice prepared from the clarified juice by using thermal evaporation and osmotic distillation processes as a function of solids concentration in the range 115 - 614 g/kg of total soluble solids (TSS) within a range of 20 - 70 C. The effect of the temperature and concentration on the juice viscosity was studied. Arrhenius-type correlation equations for viscosity were used to represent the temperature dependence of viscosity. Values of the Arrhenius equation parameters (flow activation energy) were calculated for the measured viscosities of juices as a function of concentration. Results indicated no significant differences in the rheological behavior for orange juices concentrated with both methods. The juices exhibited a Newtonian behavior regardless of the concentration method.

Cite this publication as follows:
OlivieroRossi C, Destani F, Cassano A: Rheological behavior of blood orange juice concentrated by osmotic distillation and thermal evaporation, Appl. Rheol. 24 (2014) 63776.

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Lopez-Lopez MT, Rodriguez-Arco L, Duran JD, Gonzalez-Caballero F: 14th International Conference on Electrorheological Fluids and Magnetorheological Suspensions (ERMR2014), Appl. Rheol. 24 (2014) 55.

The rheological properties of diamond (< 10 nm) in silicone oil (PDMS) were analyzed using steady shear and oscillatory shear measurements. Unlike micron sized diamond suspensions these suspensions were non Newtonian and showed strong viscoelastic behavior without the electric field applied. Furthermore these nanodiamond mixtures showed sigmoidal behavior for their apparent viscosity as the shear rate is increased without the electric field applied. When the electric field was applied the apparent viscosity of the mixtures increased by an order of magnitude at lower shear rates. The effects of electric field and concentration on diamond rheology are both examined. The rate of shear thinning for the mixtures is high when the applied electric field is high. At high shear rates for the mixture the electric field does not have much effect. The flow curve was described by the Herschel-Bulkley model. Yield stress values obtained from the model gives an important relationship between yield stress, electric field and concentration, that is τ ∝ En and where 0.8 < n < 1.3.

Cite this publication as follows:
McIntyre C, Pereira A: Electrorheology of nanodiamond/PDMS nanofluids in steady and oscillatory shear, Appl. Rheol. 24 (2014) 63471.

We modify a commercial rheometer so that the disks are aligned perpendicular to the axis of rotation with a precision in parallelism of about 1 μm independent of the rheometer reading. This leads to decrease the zero-gap error by a factor of 25 and more. It enables samples to be studied at gap widths well below the absolute error of commercial rheometers. At gap widths of 20 μm, the modification allows the measurement range to be extended to shear rates up to 105 s-1 enabling to measure low viscosities such as that of solvents or water and of dilute polymer solutions. The measurements are restricted mainly by the torque resolution at low shear rates and by inertia at high shear rates.

Cite this publication as follows:
Dakhil H, Wierschem A: Measuring low viscosities and high shear rates with a rotational rheometer in a thin-gap parallel-disk configuration, Appl. Rheol. 24 (2014) 63795.

This work presents a technique based on optical tracking of the free fall in a Newtonian fluid used in falling ball viscometers. Classical techniques have shown, on one hand a limit in the ball falling height measurement, on the other hand a limit in the accuracy estimation of velocity and therefore a weak precision on the viscosity calculation of the fluids. Our method consist to measure the fall height by taking video scenes of the ball during its fall and thus to estimate its terminal velocity which is a preponderant parameter in the kinematic velocity computing, using both the Stokes or Hoppler formalisms. The precision reached in this approach adjoins encouraging values for future works in the purpose to improve this method further.

Cite this publication as follows:
Kheloufi N, Lounis M: An optical technique for Newtonian fluid viscosity measurement using multiparameters analysis, Appl. Rheol. 24 (2014) 44134.

In this work, the viscosity of soybean oil subjected to thermal degradation has been determined and related to the chemical composition of the oil. In particular, it is found a linear relationship between the viscosity value and the triglycerides content during the degradation process (an increase of the former is associated to a decrease of the latter). Thus, it is shown that viscosity provides us a reliable way of measuring oil degradation and, insofar as proportional to flow time, it allows for the design of simple devices to control the oil quality. Besides, the study of the viscosity behavior along with the changes in composition during the cooking time, i.e. the period of time that the oil is being heated, give us valuable information about the type of chemical reactions occurring within the oil.

Cite this publication as follows:
Olivares-Carrillo P, PerezdelosRios A, Quesada-Medina J, HernandezCifre JG, DiazBanos FG: Viscosity as a measure of oil composition changes due to thermal degradation, Appl. Rheol. 24 (2014) 53667.

The aim of this study is to propose a theoretical frame that is able to lead someone to an appropriate way of modeling cement-based material extrusion. It clearly appears that different extrusion scenarios may occur. Cement-based materials are viscoplastic materials that may undergo drainage during an extrusion process carried out at low velocity. Four material behaviors can be encountered: perfect plastic, viscoplastic, frictional plastic (with evolving properties) and frictional viscoplastic (that has never been reported in the literature as drainage occurs when ram velocity is low and thus when viscous effects can be neglected). In this work, criteria are proposed to choose the more relevant way to model extrusion. Then, models are proposed for the possible extrusion scenarios.

Cite this publication as follows:
Perrot A, Rangeard D, Melinge Y: Prediction of the ram extrusion force of cement-based materials, Appl. Rheol. 24 (2014) 53320.

This historical study deepens the rheologist.s understanding of the motto of The Society of Rheology, of its history, and of its many typographies. The motto "παντα ῥει" is not verbatim something written or said by the ancient Greek Ionian philosopher Heraclitus, ca. 540 - 480 BCE. Rather it is first encountered much later, in the writings of the Roman Simplicius ca. 490 - 560 CE. Thus, although it is uniformly agreed by Greek scholars that it correctly and concisely distills Heraclitian philosophy, that of constant change, and although this is appropriately used as the motto of The Society of Rheology, there is little point in trying to rewrite it into another form (for example to capitalize it) in an effort to be more faithful to an ancient prototype. Rather, we suggest simply reinstating the two missing diacritical marks, and thus, to express it as "πάντα ῥεῖ" which is the form in which the motto was introduced in 1929. This is also consistent with current typography of ancient Greek writings, in use since the ninth century CE, following the byzantine scholars. We provide Table 1 to facilitate accurate typesetting of the motto.

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Beris A, Giacomin AJ: πάντα ῥεῖ: Everything flows, Appl. Rheol. 24 (2014) 52918.

It is well known that the shear and shear rate are not uniform in the azimuthal flow within the gap between parallel concentric disks - perhaps the most versatile among the geometries used in rheometry. This flow inhomogeneity represents a disadvantage, because the data analysis becomes intricate. Typically the stress is calculated at the rim with the assumption that it varies linearly with the radial coordinate, and then a correction is applied. This correction may be very large, depending on the nature of the sample, type of test, and range of parameters. While for steady-state shear flow different methods for correcting the stress are available, for transient flows they are rather scarce and in some cases unavailable. In this work we analyze in detail the stress correction for the main rheometric experiments, and discuss when it is needed. To this end, we performed different tests with a commercial hair gel and a polyacrylamide solution. For oscillatory flows, a simple equation to correct the stress amplitude is obtained in terms of the amplitudes of the torque and shear rate.

Cite this publication as follows:
deSouzaMendes PR, Alicke AA, Thompson RL: Parallel-plate geometry correction for transient rheometric experiments, Appl. Rheol. 24 (2014) 52721.

Cite this publication as follows:
Cheneler D: Mathematical Modelling in Chemical Engineering (A. Rasmuson, B. Andersson, L. Olsson, R. Andersson), Appl. Rheol. 24 (2014) 9.

large amplitude oscillatory shear (laOS) rheology is often performed in order to complement steady simple shear (SSS) rheology, i.e., probe rheological properties of materials that cannot be not observed with SSS alone. However, it is difficult to measure the SSS rheology of some problematic materials due to fracture and ejection, and laOS may alleviate these issues, at least partially. Therefore, it is of interest to obtain SSS rheology information from laOS measurements. We show that a constitutive modeling approach may be used to unify the analysis of laOS data obtained from different viscometric geometries and modes of control and that the laOS data may be used to predict SSS profiles. A model elastoviscoplastic material, a Carbopol solution, was used to validate the approach experimentally. laOS rheometry of problematic biomass slurries was also performed, and the SSS profiles for the slurries were predicted with more confidence than could be obtained from SSS measurements directly.

Cite this publication as follows:
Stickel JJ, Knutsen JS, Liberatore MW: Connecting large amplitude oscillatory shear rheology to unidirectional shear rheology and application to biomass slurries, Appl. Rheol. 24 (2014) 53075.

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Marino R, Giovando S, Gabriele D: Effect of tannin addition on the rheological properties of starch-based adhesives, Appl. Rheol. 24 (2014) 46138.

A novel shear thickening suspoemulsion is formulated and studied with a new rheo-microscope instrument. The experimental fluid system is comprised of a immiscible blend of Newtonian, low molecular weight poly(dimethylsiloxane) and a shear thickening suspension of colloidal silica in poly(ethylene glycol). The blend is studied as a function of composition where phase inversion is evident at low shear rates and is found to be shear rate dependent. A shear thickening viscosity curve is observed when blends comprised of shear thickening fluid dispersed as droplets are subjected to high shear rates. Dispersing a continuously shear thickening fluid, φsilica = 0.42, results in continuously shear thickening response from the blend. Dispersing a discontinuously shear thickening fluid, φsilica = 0.51, results in bulk shear thickening that can also be discontinuous. Shear thickening in the final suspoemulsion is consistently first detected at φSTF = 0.2, with the magnitude of shear thickening being dependent on the particle concentration in the STF phase. The onset of shear thickening also corresponds with the formation of extended droplet structures in the fluid. The complex properties of these suspoemulsions and the ability to formulate dispersed droplet morphologies in this mixture are shown to result from the underlying shear thickening rheology of the dispersed phase.

Cite this publication as follows:
Fowler JN, Kirkwood J, Wagner NJ: Rheology and microstructure of shear thickening fluid suspoemulsions, Appl. Rheol. 24 (2014) 43049.

Electrorheological measurements represent a key approach in characterizing the efficiency of electrorheological fluids. The rotational rheometers, the Physica MCR 501 (Anton Paar) equipped with an electrorheological cell and the Bohlin Gemini CVOR 150 (Malvern Instruments) modified for electrorheological experiments generate an electric field in two completely different ways. Each of the two generations has a specific influence on electrorheological measurements. The experimental data were obtained and compared for a suspension of polyaniline powders mixed (10 wt%) in silicone oil. For a concentric-cylinders arrangement, it was shown that the data are fully comparable for both rheometers. However, for a parallel-plate arrangement, the data using the Physica MCR 501 provide higher values in comparison with both the corresponding plateplate data obtained with the Bohlin Gemini CVOR 150 and with the mutually comparable concentric cylinders data.

Cite this publication as follows:
Peer P, Stenicka M, Filip P, Pavlinek V: Comparison of Electrorheological Measurements Based on Different Methods of Electric Field Generation, Appl. Rheol. 24 (2014) 42875.

The influence of pH of walnut oil emulsions on droplet morphology, droplet size distribution, time and temperature stability, and rheological properties has been studied. It has been found that walnut oil based emulsions form a metastable gel-like microstructure at steady conditions revealed by a linear viscoelastic response at low deformations. Flow curves of investigated emulsions demonstrated shear thinning behavior at moderate shear rates with a tendency to a limiting viscosity at higher loads. The most stable emulsion was formed at weakly acidic conditions (pH = 6), which favors the formation of fine uniform droplets with no visible tendency to coagulation at ambient conditions.

Cite this publication as follows:
Kowalska M, Krzton-Maziopa A: pH effect on viscoelastic behavior and physicochemical properties of walnut oil emulsions, Appl. Rheol. 24 (2014) 45105.

This work contributes to the theory of strain controlled large amplitude oscillatory shear (laOS) as well as modelling the key properties of type III behavior of Hyun, the decreasing storage modulus and a loss modulus with considerable maximum. The latter two can be modelled with the help of the Prandtl element. Since it is a yield stress fluid, the use of laOS is necessary to calculate the storage and loss modulus. Furthermore, a condition is presented which has to be met in order to avoid even harmonics. The storage and loss modulus as well as the higher harmonics of the Prandtl element are determined analytically in this work. They are given as mathematical functions which can be discussed conveniently. This allows the identification of characteristic points which are related to material parameters of the Prandtl element and enable a physically motivated material parameter identification. Beside this, it is observed that the yield strain do not coincide with the crossover G'(γ) = G''(γ) but with the increasing of the loss modulus and the decreasing of the storage modulus. Thanks to the analytical calculations, it is also obvious that the stress response of yield stress fluids does not necessarily include even harmonics. In this work the steady state stress response of the Prandtl element is also presented as Lissajous plots and Pipkin diagrams to visualise the rheological fingerprint.

Cite this publication as follows:
Boisly M, Kastner M, Brummund J, Ulbricht V: Large amplitude oscillatory shear of the Prandtl element analysed by Fourier Transform Rheology, Appl. Rheol. 24 (2014) 35478.

Phase-separable particulate-containing gel structures constitute complex fluids. In many cases they may incorporate component concentration inhomogeneities within the ensemble matrix. When formulated into high consistency suspensions, these can lead to unpredictable time-dependent variations in rheological response, particularly under shear in simple parallel plate and cylindrical rotational geometries. Smoothing function algorithms are primarily designed to cope with random noise. In the case studied here, namely nanocellulose-based high consistency aqueous suspensions, the system is not randomised but based on a series of parallel and serial spatial and time related mechanisms. These include: phase separation, wall slip, stress relaxation, breakdown of elastic structure and inhomogeneous time-dependent and induced structure re-build. When vacuum dewatering is applied to such a suspension while under shear, all these effects are accompanied by the development of an uneven solid content gradient within the sample, which further adds to transitional phenomena in the recorded rheological data due to spatial and temporal differences in yield stress distribution. Although these phenomena are strictly speaking not noise, it is nevertheless necessary to apply relevant data smoothing in order to extract apparent/process viscosity parameters in respect to averaging across the structural ensemble. The control parameters in the measurement of the rheological properties, to which smoothing is applied, are focused on parallel plate gap, surface geometry, shear rate, oscillation frequency and strain variation, and relaxation time between successive applications of strain. The smoothing algorithm follows the Tikhonov regularisation procedure.

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Dimic-Misic K, Nieminen K, Gane PA, Maloney T, Sixta H, Paltakari J: Deriving a process viscosity for complex particulate nanofibrillar cellulose gel-containing suspensions, Appl. Rheol. 24 (2014) 35616.

Rheological and electrical properties of polymeric nanoparticle solutions and their influence on the rheological and electrical properties of red blood cell (RBC) suspensions have been studied. Poly(acrylic acid) macromolecules of different architecture and molecular weight were used: (i) a new core.shell type star polymer whose interior forms hyperbranched polystyrene bearing arms of poly(acrylic acid) with molecular weight Mn = 56 920 Da and (ii) linear polyacrylic chains with average molecular weights Mn = 6000, 20000, and 225000 Da. The polymers dissolved in physiological solution with weight concentrations 1 mg/ml and 0.2 mg/ml were used for the experiments. Under physiological conditions the star-shaped macromolecules present spherical nanoparticles while the linear poly(acrylic acid)s adopt an extended chain conformation close to rod-like particles. The apparent viscosity of the nanoparticle solutions and RBC suspensions in the presence and absence (the control) of nanoparticles were measured using a rotational viscometer Contraves Low Shear 30 (LS 30) at a steady flow at shear rates from 0.0237 to 94.5 s-1 and temperature 37 C. A method, based on the measurement of dielectric properties of dispersed systems in Couette viscometric blood flow was applied. A concurrent measurement system and data acquisition system implied into the Contraves LS 30 were used to quantify the electrical conductivity. The main advantage of this technique is that blood is subjected to a uniform shearing field in a Couette rheometric cell as well as the information about the mechanical and electrical properties of the fluid is obtained in parallel. The results show that rheological and electrical properties of the nanoparticle solutions and RBC suspensions, namely their electrical conductivity and apparent viscosity, are dependent on the shear rates, shape, concentration and molecular weight of the polymers. Key

Cite this publication as follows:
Antonova N, Koseva N, Kowalczuk A, Riha P, Ivanov I: Rheological and electrical properties of polymeric nanoparticle solutions and their influence on RBC suspensions, Appl. Rheol. 24 (2014) 35190.

Incorporation of liposome into gel is the most common approach for the preparation of topical and transdermal liposomal formulation, due to the ability of liposome to improve the drug deposition and permeation rate within the skin. In this study, the liposomal gel consisted of iota-carrageenan, carboxymethyl cellulose, and chitosan-coated-oleic acid liposome were prepared. The effect of liposomes on the rheological properties of the iota-carrageenan-carboxymethyl cellulose mix gel was evaluated. The rheological result indicated that the presence of the chitosan-coated-oleic acid liposomes in the gel had modified the viscoelastic and flow characteristics of the gel. The input energy from the oscillatory test could be stored more effectively in the elastic component of the liposomal gels, as compared to the original gel itself. This result showed that the liposomal gels exhibited greater elasticity and were more solid-like when compared with the original gel system. The complex viscosity of the liposomal gels was slightly higher than the original gel. The complex viscosity of the liposomal gels was also found to decrease with increasing frequency, indicating the shear thinning behavior of the liposomal gels. The lower Power law Index (PDI) of the liposomal gels indicated a greater shear thinning behavior and better spreadability.

Cite this publication as follows:
Tan HW, Misran M: Effect of chitosan-modified fatty acid liposomes on the rheological properties of the polysaccharide-based gel, Appl. Rheol. 24 (2014) 34839.

This paper presents the development of a vane rheometer to estimate mortar plastic viscosity and yield stress. The rheological parameters were developed from measurements using a procedure to convert the vane torque and rotational velocity data into shear stress versus shear rate relationships. The used procedure considered the locally sheared material as a Bingham fluid and computed the characteristic shear rate from Couette analogy. The apparatus was tested with three experimental programs in which many rheological parameters of mortar compositions were calculated. The obtained results validated the rheometer test procedure and confirmed that the test results are reproducible.

Cite this publication as follows:
Soualhi H, Kadri E, Ngo T, Bouvet A, Cussigh F, Kenai S: A new vane rheometer for fresh mortar: development and validation , Appl. Rheol. 24 (2014) 22594.

The effect of concentration on viscoelastic properties of chestnut and acorn starch is discussed in the paper. The starch structure was assessed using a rheological fractional standard linear solid model FSLSM in contrary to very simple power-law model usually used in many published papers concerning determination of rheological properties of starch. Rheological parameters of this model were determined and their changes for different concentrations of the two tested types of starch were discussed. The values of the rheological parameter of FSLSM model give a useful of information concerning the elastic properties of materials such as total elasticity of networks, network oscillations, gel stiffness, structure of cross-linking and relaxation time of the materials. The proposed method for the interpretation of rheological measurements of the two types of starch allows for a comprehensive estimation of the analyzed biomaterial structure. The fractional rheological models can be very useful to control the biomaterial structure the needs of the final to meet envisaged product which is particularly significant from the point of view of materials engineering.

Cite this publication as follows:
Orczykowska M, Dziubinski M: Comparison of viscoelastic properties of chestnut and acorn starch by means of mechanical models with an in-built springpot, Appl. Rheol. 24 (2014) 24766.

Bentonite dispersions in polymer solutions may behave as gel like materials. Under stress, the structure formed at rest is progressively destroyed and a solid-liquid transition occurs. The rheological characterization of such kind of systems is often done by applying stress ramps of the sample. A simple Herschel-Bulkley equation is not convenient to fit the answer of the material to the ramp since it does not take in account the effect of time. The models for yield stress fluids involving two viscosity levels are not convenient too since they don.t take in account the elastic behavior at low stresses. We propose in this paper two equations in order to determine some parameters characterizing the rheological behavior of such systems. The results obtained both in oscillatory and permanent shear are compared according to Winter.s representation and a rescaling of the complex modulus is proposed to superimposed the data in the solid/liquid transition region.

Cite this publication as follows:
Dupuis D, Bekkour K, BenAzouz K: On the modeling of the rheological behaviour of bentonite dispersions in polymer solutions, Appl. Rheol. 24 (2014) 24283.

Cite this publication as follows:
Loren N, Larsson A, Ahrne L, Hermansson A, Lillford P: Water in Soft Materials - ISOPOW XII conference (2013), Appl. Rheol. 24 (2014) 44.

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Roussel N, Bessaies-Bey H, Coussot P: The 1st International RILEM Symposium on Rheology and Processing of Construction Materials, Appl. Rheol. 24 (2014) 46.

Blood vessels have been modeled as non-porous structures that are permeable to solutes mixed in the blood. However, the use of non-physiological boundary conditions in numerical simulations that assume atmospheric pressure at the outlet does not illustrate the actual structural physics involved. The presence of pores in the wall influences wall deformation characteristics, which may increase the risk of rupture in specific conditions. In addition, the formation of secondary flows in a curved blood vessel may add complications to the structural behavior of the vessel walls. These reservations can be addressed by a fluid structure interaction-based numerical simulation of a three-dimensional aortic arch with increased physiological velocity and pressure waveforms. The curvature radius of the arch was 30 mm with a uniform aorta diameter of 25 mm. A one-way coupling method was used between physics of porous media flow and structural mechanics. A comparison of results with a non-porous model revealed that the approximated porous model was more prone to hypertension and rupture. Similarly, the secondary flows found to be an important indicator for the vascular compliance that forced the outer aortic region to experience the largest deformation. Consequently, it is very important to use actual physiological situations of the blood vessels to reach a diagnostic solution.

Cite this publication as follows:
Cheema TA, Kim GM, Lee CY, Hong JG, Kwak MK, Park CW: Characteristics of blood vessel wall deformation with porous wall conditions in an aortic arch, Appl. Rheol. 24 (2014) 24590.

This work contributes to general theoretical aspects of yield stress fluids with significance for practical phenomenological material modeling. It introduces a terminology so that the material class .yield stress fluid. is defined and can be distinguished from the terms .solid. and .liquid.. This new material classification is based on two criteria, the equilibrium relation and the flow function. In line with this terminology, an experimental procedure for classifying the material behavior is presented. The second key aspect of this paper is a discussion on the proper definition of the term .viscosity.. The benefit of the differential viscosity over the dynamic viscosity in case of non-Newtonian fluids in general is worked out. This is shown by the most elementary yield stress fluid, the friction element, because it is the basis of the yield stress concept. Its constitutive equations are given for positive as well as negative strain rates and are also able to represent the preyield behavior. The theory presented in this article is also applied to the Maxwell, Kelvin-Voigt, and Bingham element to demonstrate the working principle.

Supplementary Information is contained as an attachment to the reprint-pdf.

Cite this publication as follows:
Boisly M, Kastner M, Brummund J, Ulbricht V: General aspects of yield stress fluids - Terminology and definition of viscosity, Appl. Rheol. 24 (2014) 14578.

Mechanical properties of various technological materials at large deformations are proposed to characterize by means of some generalized parameters obtained at large oscillation strains but not related to any definite rheological equations. The base for the analysis is the Lissajous- Bowditch figures in two coordinate systems - "stress - deformation" and "stress derivative with respect to the phase angle - deformation". An area of the first of these figures provides the well known integral estimation of dissipative losses in the deformation cycle while the second one presents the new integral measure of the matter's elasticity. The correlation between the proposed integral estimations of the "averaged" dynamic modulus and the values found in using Fourier and Chebyshev series was demonstrated. This integral method was applied for three suspensions of various types. The obtained results allowed for viewing the type of non-linearity: pseudo-plasticity or dilatancy, stiffening or softening, as functions of deformation.

Cite this publication as follows:
Ilyin S, Kulichikhin V, Malkin A: Characterization of material viscoelasticity at large deformations, Appl. Rheol. 24 (2014) 13653.

Impregnation of organic liquid electrolytes in conductive powders is of major importance in the field of energy storage devices such as batteries or super-capacitors. Impregnation during mixing and processing operations becomes usual for practical reasons and requires a better understanding of the changes of the rheological behavior of the mix. In this paper, the impregnation of propylene carbonate (PC) and dimethyl sulfoxide (DMSO) in activated carbon (AC) and carbon black (CB) was studied by using an internal mixer. Monitoring of the torque of the filler/liquid blend as a function of the amount of liquid fed in the mixing chamber, enables to detect the transition from the solid friction of the dry powder to the lubricated liquid (or viscous) behaviour of the concentrated paste of wetted powder. The results were compared with data obtained by conventional nitrogen adsorption porosimetry combined with the knowledge of the molecular diameter of the liquids. A characteristic change was observed as soon as the liquid completely fills the porosity of the filler. Both tested liquids (DMSO and PC) impregnate more carbon black and the take-up rate is slightly higher for DMSO in comparison to PC because, as a polar liquid, DMSO has a better interaction with both fillers.

Cite this publication as follows:
Akkoyun M, Carrot C, Blottiere B: On the use of an internal mixer to study the impregnation of carbon fillers by organic liquids, Appl. Rheol. 24 (2014) 13487.

We present a study of the structural and thermomechanical properties of lyotropic phase in the quasi ternary system made of Cetylpyridinium chloride (CPCl)/hexanol/salt water (0.9% by mass) with and without cobalt microparticles. Phase transition temperatures of the structural sequence isotropic L1/nematic calamitic Nc,/hexagonal H have been determined by differential scanning microcalorimetry. Temperature induced developable domains in hexagonal phase H and disclinations in calamitic nematic phase Nc were observed in crossed polar optical microscopy in confined geometry. A rheological study of calamitic nematic phase Nc highlighted structuring effect of cobalt microparticles from a concentration of 2% to be demonstrated by an increase in viscosity and viscoelastic moduli. This could be explained by a stabilization of disclinations.

Cite this publication as follows:
Ponton A, Meyer C, Foyart G, Aymard L, Djellab K: Structural and thermomechanical investigation of lyotropic liquid crystal phases doped with monodisperse microparticles, Appl. Rheol. 24 (2014) 14147.

Cite this publication as follows:
Rubio-Hernandez F, Gomez-Merino A, Velazquez-Navarro J, Parras L: 4th Iberian Meeting on Rheology. Fundamental and Applied Rheology (IBERO 2013), Appl. Rheol. 23 (2013) 374.

Cite this publication as follows:
Fischer P: Understanding Viscoelasticity - An Introduction to Rheology (Nhan Phan-Thien), Appl. Rheol. 23 (2013) 329.

This study addresses the Taylor-Galerkin/pressure-correction solution of industrial high-speed reverse roller coating flow associated with thin-film paint-coatings of strip-steel. Novel aspects lie in the inclusion of the dynamic wetting line and flow analysis due to surface tension and inelastic rheology effects, via shear-thinning and lowering high shear viscosity levels. The main aim of the study is to predict the zonal flow influences by examining viscous flow structures around the meniscus, nip and wetting line regions, conveyed via streamline and shear rate patterns, surface distributional lift and localised nip-pressures. The majority of this study focuses on the secondary nip-vortex and its influences on the contact point and dynamic wetting line. This aspect of the flow provides the driving mechanism for the onset of instabilities, which governs the entire process and tends to determine the consistency of the film thickness at the outflow. Positive peak-pressures tend to increase with decrease in nip-gap size. At low nip-gap size, negative peak pressures are observed around the substrate-wetting line contact region. At higher speed-ratios, positive peak pressures are seen to increase with less recirculation apparent around the contact zone. Significantly and upon surface tension increase, the dynamic wetting line is sucked further inwards towards the nip-gap, stimulating a localised wetting line-foil third vortex structure, which causes an apparent reduction in film-leakage thickness.

Cite this publication as follows:
Echendu S, Tamaddon-Jahromi H, Webster M: Modelling Reverse Roll Coating flow with dynamic wetting lines and inelastic shear thinning fluids, Appl. Rheol. 23 (2013) 62388.

Production in reservoirs located in deep and ultra-deep water that contain waxy crude oils faces a huge obstacle imposed by the low temperatures of the environment. When the waxy crude oil is subjected to a temperature below the Gelation Temperature, as in the case investigated in the present work, it exhibits a variety of non-Newtonian features: elasticity, plasticity, viscous effects, and time-dependency, which renders to this material a highly complex behavior. A crucial feature that is frequently ignored when the determination of the yield stress is being carried out, is the time-dependency nature of these materials. We demonstrate how significantly different values of yield stress can be obtained if this character of the material is neglected. We use the asphaltenes properties as inhibitors of wax formation and propose a protocol to capture yield-stress parameters. One important conclusion is that waxy crude oils can be classified as apparent-yield-stress fluids, and not (true-) yield-stress materials, with the presence of a dynamic and a static yield-stresses.

Cite this publication as follows:
Soares EJ, Thompson RL, Machado A: Measuring the yielding of waxy crude oils considering its time-dependency and apparent-yield-stress nature, Appl. Rheol. 23 (2013) 62798.

A series of fumed silica nanoparticles were used as an additional emulsifier for highly concentrated (HC) water-in-oil (W/O) emulsions. These nanoparticles, with different hydrophobicity index (HI) in the 0.60 - 1.34 and HI > 3 range, were mixed with the conventional low molecular weight surfactant, sorbitan monooleate (SMO), in the oil phase prior to the emulsification process. The rheological properties of these emulsions were measured and compared with the properties of emulsions stabilized with SMO alone. In the mixed emulsifier system, the changes in rheological parameters were clearly expressed as a function of HI. The mixture of silica nanoparticles and SMO significantly increases the yield stress and plateau modulus of fresh emulsion, compared to the SMO only system. The effect was found to be more pronounced with a decrease in the HI. This is probably related to the reduction in micelle content with the decrease in HI, owing to a concomitant increase in the amount of SMO adsorbed onto the particle surface. Then, interestingly, the Foudazi-Masalova model recently developed for surfactant-stabilized highly concentrated emulsions (HCE) was found to describe successfully the rheological behavior of emulsions in the presence of a mixture of surfactant and fumed nanosilica.

Cite this publication as follows:
Tshilumbu NN, Masalova I: Effect of nanoparticle hydrophobicity on the rheology of highly concentrated emulsions, Appl. Rheol. 23 (2013) 62835.

This paper provides a new model to evaluate the yield stress of suspensions, slurries or pastes, based on the release of a finite volume of material onto a horizontal surface. Considering the height (h) and the radius (R) of the sample at the flow stoppage, two asymptotic regimes, where h > R or h < R, lead to different analytical models that allow the determination of yield stress. Experimental observations show typical sample shape at stoppage between slump (h > R) and spread (h < R). Based on these observations, we have developed a new analytical model to evaluate accurately the yield stress of materials in this intermediate regime. The validity of this model was evaluated from data obtained using various Carbopol(c) dispersions. The yield stress measured with the proposed model was compared with the yield stress evaluated from shear flow curves obtained with roughened plate/plate geometry fitted to the Herschel-Bulkley model. Results show the relevance of the proposed model which that can be applied in the range between models used for the two asymptotic regimes.

Cite this publication as follows:
Pierre A, Lanos C, Estelle: Extension of spread-slump formulae for yield stress evaluation, Appl. Rheol. 23 (2013) 63849.

Cite this publication as follows:
Madsen CG, Abo J, Featherston DW, Baldursdottir S: Rheology: A cross-disciplinary technology evolving to take on new challenges (22nd Nordic Rheology Conference 2013), Appl. Rheol. 23 (2013) 309.

Polysaccharides provide high potential to be used as rheology modifying admixtures in mineral binder systems for the construction industry such as concrete or mortar. Since superplasticizers have become state of technology, today, concrete is more and more adjusted to flowable consistencies. This often goes along with the risk of segregation, which can be effectively avoided by adding stabilising agents supplementary to superplasticizers. Stabilising agents are typically based on polysaccharides such as cellulose, sphingan gum, or starch. Starch clearly distinguishes in its effect on rheology from other polysaccharides, mainly due to the strong influence of amylopectin on the dispersion and stabilisation of particles. Based on rheometric investigations on cementitious and limestone based dispersions with different volumetric water to solid ratios, the mode of operation of modified potato starch is explained in comparison to a sphingan gum. It is shown that the stabilising effect of starch in a coarsely dispersed system is mainly depending upon the water to solid ratio and that above a certain particle volume threshold starch mainly affects the dynamic yield stress of dispersions, while plastic viscosity is affected only to a minor degree. Sphingans operate more independent of the particle volume in a coarsely dispersed system and show significantly higher effect on the plastic viscosity than on the yield stress. In systems incorporating superplasticizers, influences of both stabilising agents on yield stress retreat into the background, while both observed polysaccharides maintain their effect on the plastic viscosity.

Cite this publication as follows:
Schmidt W, Brouwers HJH, Kuhne H-C, Meng B: The working mechanism of starch and diutan gum in cementitious and limestone dispersions in presence of polycarboxylate ether superplasticizers, Appl. Rheol. 23 (2013) 52903.

The shear thickening behavior of concentrated suspensions can be exploited to dissipate energy during impact or shear loading. To preserve the consistency of the thickening behavior in practical applications, particle concentration, and dispersion should be kept within very close bounds over time. In this article, we analyze the influence of the processing methods and storage conditions on the rheological properties of shear thickening fluids (STF) based on monodisperse suspensions of silica particles in polyethylene glycol. Particle dispersion linked to processing method and time strongly influences the value of the critical shear rate and storage in contact with air and humidity is responsible for a change in particle concentration. Encapsulating the suspensions in silicone is proposed as a solution to preserve their rheological properties over time.

Cite this publication as follows:
Soutrenon M, Michaud V, Manson JAE: Influence of processing and storage on the shear thickening properties of highly concentrated monodisperse silica particles in polyethylene glycol, Appl. Rheol. 23 (2013) 54865.

The main objective of this study is to get insight into the dynamic behavior of viscoplastic drop in impingement process in which the Capillary number is greater than one. In numerical analysis, Volume Of Fluid (VOF) approach was used for capturing the liquid-gas interface. Two different drop shapes (spherical and tear shapes) were used to investigate the drop morphology in an impingement process. According to the results, the numerical results concerning the tear shape drop showed proper agreement with experimental reports (mean deviation of 16 %) in different impact velocities. The flow field was discussed during the impact process in terms of its effect on apparent viscosity and spreading length. Influence of contact angle, consistency, power law index, and surface tension variations on spreading parameter (ratio of contact diameter on the substrate to equivalent initial drop diameter) were investigated. Furthermore, three different rheological models (consisting of Herschel-Bulkley, Casson, and Robertson-Stiff) were employed to study the effects of rheological models on simulation outcomes.

Cite this publication as follows:
Noroozi S, Tavangar S, Hashemabadi S: CFD Simulation of Wall Impingement of Tear Shape Viscoplastic Drops Utilizing OpenFOAM, Appl. Rheol. 23 (2013) 55519.

Rheological properties are one of the primary considerations in selecting a fluid for using in chemical flooding enhanced oil recovery (EOR) operations. In this work, the rheological behavior of partially hydrolyzed polyacrylamide (HPAM) used for EOR was characterized by different techniques like steady shear flow and uniaxial elongation in capillary breakup experiments. Particular attention was focused on the main parameters affecting flow behavior of solutions, such as polymer concentration, molecular weight and molecular weight distribution. The shear rate dependence of viscosity for HPAM solutions could be described by the Carreau model. Elastic model was used to fit the rheological results obtained by transient uniaxial extensional technique, which enabled to evaluate relaxation time. The results indicated that the elasticity of HPAM solutions was dominated by molecular weight. Shear viscosity at higher shear rates was mainly influenced by polymer concentration, which was not an important factor determining relaxation time. For HPAM solutions, increasing of molecular weight distribution led to a decrease in shear viscosity, and vice versa for elongational viscosity and relaxation time. In addition, it was found that there was direct proportional relationship between first normal stress difference and elongational viscosity.

Cite this publication as follows:
Wu S: Shear and Elongational Rheology of Partially Hydrolyzed Polyacrylamide Used for EOR, Appl. Rheol. 23 (2013) 53800.

Viscosity measurements were performed in water/AOT (sodium bis(2-ethylhexyl) sulfoccinate)/isooctane microemulsions as a function of temperature between 25 C and 55 C, molar ratio Wo = water/AOT ranging from 3 to 45 and three values of AOT/isooctane volume fractions (Φm = 0.1, 0.15, and 0.2). It was shown that microemulsions behaved as Newtonian fluids in the studied range of shear rate. For a critical molar ratio, Woc, the corresponding viscosity, ηoc, was shown to be constant with temperature but dependent on the micellar concentration. For Wo < Woc, the solutions behaved as simple fluids and the temperature dependence of viscosity was described by an Arrhenius law. The total activation energy was found to be dependent on W with a maximum for Wo = 5. A correlation between the microscopic structure of the reverse micelles and the total activation energy was proposed. However, a complex fluid behavior was observed for Wo > Woc, where the viscosity increased with temperature. For some values of Wo, the viscosity reached a maximum, which could be explained by attractive interdroplet interactions and formation of droplet clusters.

Cite this publication as follows:
Guettari M, BenNaceur I, Kassab G, Ponton A, Tajouri T: Temperature and concentration induced complex behavior in ternary microemulsion, Appl. Rheol. 23 (2013) 44966.

Suspensions composed with silica particles or cellulose fibers dispersed in glycerin and/or xanthan aqueous solutions were formulated with solids volume fraction varying up to 15 and 10 % for silica and cellulose dispersions, respectively. In addition, xanthan was added to the aqueous solutions (water or 82 % glycerin + water) at concentrations of 0.005, 0.1, and 0.2 % to impart non-Newtonian character to matrices, and results were compared to the Newtonian systems, without xanthan addition. Even though developed for suspensions in Newtonian fluids, Krieger-Dougherty and Eilers models described properly the influence of solids content on the flow behavior of suspensions in non-Newtonian fluids. Generally, increasing cellulose particles concentration led to an increase on the suspension pseudoplasticity, while for silica particles such increase was more discrete. Low deformation rheological measurements showed that glycerin-containing matrices were more independent on frequency as compared to suspensions of aqueous xanthan solutions. Results showed that, besides particles characteristics, the rheological properties of the suspending matrix are crucial for determining the arragements and flow properties of suspensions.

Cite this publication as follows:
Sato A, Perrechil F, Cunha R: Rheological behavior of suspensions dispersed in non-Newtonian matrix, Appl. Rheol. 23 (2013) 45397.

Back extrusion represents one of the cheapest experimental methods to determine rheological characteristics of studied fluids, and simultaneously minimise their disruption in comparison with conventional rotational rheometers. This method is based on plunging a circular rod into an axisymmetrically located circular cup containing the experimental sample. Formerly this method has, among other uses, been successfully applied to determinations of parameters appearing in power-law, Bingham and Herschel-Bulkley fluids. The aim of this contribution is to present a sufficiently simple user-friendly procedure for determining individual rheological parameters appearing in the Vocadlo model (sometimes called the Robertson-Stiff model) - yield stress, consistency parameter and flow behaviour index.

Cite this publication as follows:
David J, Filip P, Kharlamov A: Back extrusion of Vocadlo-type fluids, Appl. Rheol. 23 (2013) 45366.

Currently more and more researches have been performing concerning the numerical simulation of the behavior of fresh concrete during pumping or formwork filling. Adequate implementation of the rheology properties of fresh concrete is a determinant key to obtain realistic simulations. However, in many cases, the rheological parameters of the fresh concrete as determined by rheometers are not sufficiently accurate. The common principle of all the rheometers is not to measure directly the rheological parameters of concrete but to measure some basic physical parameters (torque, velocity, pressure, ...) that that in some cases allow the calculation of the rheological parameter in terms of fundamental physical quantities. Errors can be caused by undesired flow phenomena which are not taken into the prediction formulas and by the inaccurate prediction formulas themselves. This is directly related to the poor calibration of the rheometer that cannot cover all ranges of materials. This paper investigates the calibration of the Tattersall MK-II rheometer by performing the numerical simulation for a tremendous range of concrete flowing in the rheometer, using computational fluid dynamics (CFD). This allows to quickly and accurately obtain the rheological properties of fresh concrete, which can then be used consistently for further flow simulations. This method can be applied for all types of rheometer.

Cite this publication as follows:
Le HD, DeSchutter G, Kadri E, Aggoun S, Vierendeels J, Tichko S, Troch P: Computational fluid dynamics calibration of Tattersall MK-II type rheometer for concrete, Appl. Rheol. 23 (2013) 34741.

We discuss the possibility of using penetrometry technique for measuring the yield stress of concentrations made of grains immersed in a colloidal phase, such as concrete or muds. In that aim we used model materials made by suspending glass beads at different concentrations in a kaolin-water paste. We then show that a uniform shear stress develops along the object (plate or cylinder) beyond the entrance length. This shear stress plotted versus the object velocity exhibits a shape similar to the flow curve of the material determined from rheometry. For materials exhibiting the typical flow curve of a simple yield stress fluid, i.e. at bead concentrations smaller than 30 %, the stress associated with an inflection point located at low velocities of this curve appears to correspond to the material yield stress. At larger concentrations of beads the suspensions have a more complex behaviour likely affected by its granular nature at a local scale and the possibility of migration or frictional effects, so that neither conventional rheometry nor penetrometry provide relevant data. We conclude by describing two practical penetrometry techniques for precisely measuring the yield stress of simple pastes.

Cite this publication as follows:
Tikmani M, Boujlel J, Coussot P: Assessment of penetrometry technique for measuring the yield stress of muds and granular pastes, Appl. Rheol. 23 (2013) 34401.

Cite this publication as follows:
Thomas S, Kalarikkal N, Joy J: Third International Conference on Natural Polymers (ICNP 2012), Appl. Rheol. 23 (2013) 59.

This paper discusses the rheological properties of different contents of a commercially available Southern African clay, Eccabond fine (EBF), modified with hexadecyl trimethyl ammonium bromide, and Cloisite 15A (C15A), modified with dimethyl dehydrogenated tallow quaternary ammonium chloride dispersed in silicone oil. Focused-ion beam scanning electron microscopy shows that both C15A and EBF clays have sheet-like morphologies, but the sheets are more compact in the case of EBF clay. The rheological behavior of different suspensions was characterized by using a rheometer. The EBF suspensions behaved like Bingham fluids and also exhibited higher degrees of viscoelasticity than the C15A suspensions. The Casson model used to calculate the data of the yield stresses for the EBF suspensions was found to fit quite well with the flow curve results. The EBF suspensions obeyed the Schwarzl relation, in which the relaxation modulus (G(t)) illustrated a plateau-like behaviour for EBF suspensions compared to the C15A suspensions.

Cite this publication as follows:
Hato MJ, Pillai SK, Choi HJ, Zhang K: The rheology of non-aquoeous suspension of modified eccabond fine (EBF) clay, Appl. Rheol. 23 (2013) 34870.

The flow of complex fluids is routinely encountered in a variety of industrial manufacturing operations. Some of these operations use rheological methods for process and quality control. In a typical process operation small quantities of the process fluid are intermittently sampled for rheological measurements and the efficiency of the process or the quality of the product is determined based on the outcomes of these measurements. The large number of sample-handling steps involved in this approach cost time and cause inconsistencies that lead to significant variability in the measurements. These complications often make effective process/ quality control using standard rheometric techniques difficult. The effectiveness of control strategies involving rheological measurements can be improved if measurements are made online during processing and sampling-steps are eliminated. Unfortunately, online instruments capable of providing sufficiently detailed rheological characterisation of process fluids have been difficult to develop. Commercially available online instruments typically provide a single measurement of viscosity at a fixed deformation rate. This dependence on a single pre-determined shear rate restricts these instruments from identifying changes in the product or the process, especially if the viscosity at the pre-determined shear rate remains unaltered during these changes. We introduce an Online Rheometer (OLR) that uses small amplitude oscillatory squeeze flow to measure the viscoelastic properties of process fluids in-process and in real time under typical processing conditions. We demonstrate that with an appropriate measuring geometry and amplitude of oscillation, the frequency response of typical non-Newtonian fluids can be accurately measured in a process pipe. We also compare our results with other techniques that are typically used for process rheometry, critically evaluating the utility of the OLR technology for advanced process and quality control.

Cite this publication as follows:
Konigsberg D, Nicholson TM, Halley P, Kealy TJ, Bhattacharjee PK: Online process rheometry using oscillatory squeeze flow, Appl. Rheol. 23 (2013) 35688.

We describe and implement an efficient, open-source, multi-platform computer program ReSpect to infer the continuous and discrete relaxation spectra from dynamic moduli measurements obtained by small-angle oscillatory shear experiments. We employ nonlinear Tikhonov regularization and the Levenberg-Marquardt method to extract the continuous relaxation spectrum. To obtain the discrete relaxation spectrum, we introduce a novel algorithm that exploits the continuous spectrum to position the modes. It uses a simple criterion which balances accuracy and conditioning of the resulting least-squares problem to determine a parsimonious number of modes. The end result is an easy-to-use, and easy-to-extend program, which can be used from the command-line or from a graphical user interface to override some of the default algorithmic choices. © 2013 Applied Rheology.

Cite this publication as follows:
Takeh A, Shanbhag S: A Computer Program to Extract the Continuous and Discrete Relaxation Spectra from Dynamic Viscoelastic Measurements, Appl. Rheol. 23 (2013) 24628.

This work evaluates the impact of using bauxite residue (BR) as filler addition in cementitious compositions, during the early ages of transformation from the viscous fluid phase to an elastic solid. Chemical reaction and consolidation (physical phenomena of hardening) were also correlated. The chemical reaction rate was accompanied using isothermal calorimetry and the consolidation measured using oscillatory rheometry (quantifying the storage modulus - G' and relating with yield stress, σ0). The results show that BR accelerates the cement hydration reaction, but in pastes with pure cement, consolidation was faster, showing a distinct effect on the fluid-solid transition.

Cite this publication as follows:
Romano RCdO, Liberato CC, Montini M, Gallo JB, Cincotto MA, Pileggi RG: Evaluation of transition from fluid to elastic solid of cementitious pastes with bauxite residue using oscillation rheometry and isothermal calorimetry, Appl. Rheol. 23 (2013) 23830.

Three major hydrogenated castor oil crystal morphologies have been observed: fiber, rosette and irregular crystal. Due to the difficulty in obtaining samples with a single crystal morphology, rheological studies of suspensions containing mixtures of the three morphologies in an aqueous solution have been undertaken. The viscometry of dilute suspensions has shown that the magnitude of intrinsic viscosity is dominated by the fraction of a crystal morphology type, i.e. fiber > rosette > irregular crystal. A modified Farris model was fitted to the rheology data for mixtures of crystal morphology with interacting particles. A yield stress exists for concentrated suspensions followed by a shear thinning behavior with the increase of shear rate. A power-law relation has been found between yield stress and total particle volume fraction, and a constant exponent of 1.5 has been obtained regardless of crystal morphology.

Cite this publication as follows:
Yang D, Hrymak A: Rheology of Aqueous Dispersions of Hydrogenated Castor Oil , Appl. Rheol. 23 (2013) 23622.

In this work, bentonite suspension and mixtures containing 5 wt% of bentonite and 0.1 and 0.5 wt% of carboxymethyl cellulose (CMC) were investigated in terms of their rheology and hydrodynamic behaviour in pipe flow. All fluids exhibited non- Newtonian rheological behaviour that can be well described by the three parameters Herschel-Bulkley model. The axial velocity distribution was determined using ultrasonic pulsed Doppler velocimetry technique. In the laminar regime the flow parameters were predicted by integration of the constitutive rheological model used. In the turbulent flow, the Dodge and Metzner model was applied to fit the experimental data. The measurements of the friction factor showed a small amount of drag reduction for the pure bentonite suspension, whereas for the polymer.clay blend the drag reduction was more important.

Cite this publication as follows:
Benslimane A, Bekkour K, Francois P: Effect of addition of Carboxymethylcellulose (CMC) on the rheology and flow properties of bentonite suspensions, Appl. Rheol. 23 (2013) 13475.

The aim of the present work was to predict the extrudate swelling behavior of organoclay containing Acrylonitrile- Butadiene-Styrene (ABS) nanocomposite. The modeling was performed on the basis of unconstrained recovery concept originally introduced by Tanner but employing Wagner viscoelastic model with generalized Wagner damping function which is believed to be capable of taking into account the effect of organoclay on viscoelastic properties of nanocomposite sample. This approach enabled us to evaluate the effect of organoclay on extrudate swell in terms of disentanglement kinetics and chain relaxation behavior. In our modeling, the effect of die entrance region on the extent of extrudate swelling was also considered. In order to evaluate the validity of our modeling, the extrudate swell was measured as a function of wall shear stress for samples varying in organoclay content. The results predicted from the model were found to be in relatively good agreement with the experimental results.

Cite this publication as follows:
Saadat A, Nazockdast H, Sepehr F, Mehranpoor M: Viscoelastic modeling of extrudate swell of Acrylonitrile-Butadiene-Styrene/Clay nanocomposite, Appl. Rheol. 23 (2013) 12131.

The objective of this paper is to present the results of a research about the effect of mineral additions and specific lightweight aggregates obtained from wastes materials (crushed EPS and cork) on the rheological properties of renderings mortars. Four series of mortar formulations were prepared. Each series was composed by four mortars mixes with different mineral additions: hydrated lime, glass powder, tungsten mine waste mud, and metakaolin. The proportions of the mortars expressed in terms of apparent volume of cement, mineral addition and sand was 1:1:5. Flowability of mortar was measured using a standard flow table test. The density and the water retention capacity of mortars were also determined. The mortar rheological parameters were evaluated using a rheometer. The results show that the mortar yield stress is strongly influenced by the water amount, binder fineness and mineral addition nature. The mortars plastic viscosity is also influenced by the nature of mineral addition and the partial replacement of sand by EPS aggregates introduce incongruent values, caused by the segregation, in the mortar yield stress, whereas, the cork aggregates is responsible by the yield stress reduction.

Cite this publication as follows:
PereiradeOliveira LA, CastroGomes JP, Nepomuceno M: The influence of wastes materials on the rheology of rendering mortars, Appl. Rheol. 23 (2013) 15505.

The rheological properties of polyethylene oxide (PEO) solutions were investigated, at different temperatures, using small and large deformation rheological methods. Steady-state flow measurements showed that the flow behavior of the PEO solutions is well described by the Cross model, which yields the critical concentrations c* (from the dilute regime to semidilute regime) and c** (from the semi-dilute regime to the concentrated regime). In the range of the temperatures investigated here, the apparent viscosity is found to obey the Arrhenius equation below a critical temperature we believe corresponds to the cloud point temperature. Above the cloud point temperature, the viscosity increased with temperature. Similarly below the cloud point, both transient and dynamic tests showed that PEO solutions exhibit viscoelastic behavior, where both the elastic G' and viscous G'' modules increased with the increase in concentration and with the decrease in temperature. The Cox-Merz rule was found to apply to the PEO solutions at temperatures lower than the cloud point temperature, whilst divergence was reported after phase separation. The frequencies at which G' = G'', i.e. the reciprocal of the relaxation times of the temporary polymer network, was found to increase (the relaxation times decline) with decreasing polymer concentration, in agreement with the relaxation times, derived from the Cross model. In essence, this study demonstrates that it is possible to monitor accurately the cloud point temperature of PEO solutions by viscometric analysis.

Cite this publication as follows:
Bahlouli MI, Bekkour K, Benchabane A, Hemar Y, Nemdili A: The effect of temperature on the rheological behavior of polyethylene oxide (PEO) solutions, Appl. Rheol. 23 (2013) 13435.

An adaptive neuro-fuzzy inference system (ANFIS) was used to accurately model the effect of gum concentration (GC) and shear rate (SR) on the apparent viscosity (h) of the ice-cream mixes stabilized with different concentrations of xanthan gum. ANFIS with different types of input membership functions (MFs) was developed. Membership function "the gauss". generally gave the most desired results with respect to MAE, RMSE and R2 statistical performance testing tools. The ANFIS model was compared with artificial neural network (ANN) and multiple linear regression (MLR) models. The estimation by ANFIS was superior to those obtained by ANN and MLR models. The ANFIS and ANN model resulted in a good fit with the observed data, indicating that the apparent viscosity values of the ice-cream can be estimated using the ANFIS and ANN models. Comparison of the constructed models indicated that the ANFIS model exhibited better performance with high accuracy for the prediction of unmeasured values of apparent viscosity h parameter as compared to ANN although the performance of ANFIS and ANN were similar to each other. Comparison of the constructed models indicated that the ANFIS model exhibited better performance with high accuracy for the prediction of unmeasured values of apparent viscosity h parameter as compared to ANN although the performance of ANFIS and ANN were similar to each other.

Cite this publication as follows:
Toker OS, Yilmaz MT, Karaman S, Dogan M, Kayacier A: Adaptive neuro-fuzzy inference system and artificial neural network estimation of apparent viscosity of ice-cream mixes stabilized with different concentrations of xanthan gum , Appl. Rheol. 22 (2012) 63918.

Cite this publication as follows:
Goh A, Hassell D, Jaafar A: Institute of Materials Malaysia (IMM) 1st Rheology Symposium 2012, Appl. Rheol. 22 (2012) 347.

Cite this publication as follows:
Ilg P: Viscoelastic behavior of rubbery materials (C. M. Roland), Appl. Rheol. 22 (2012) 295.

This paper describes the development of a rapid rheological method for the characterization of functionalized citrus pulp fibers by high pressure homogenization. The suspension rheology of the fibers differ significantly depending on the applied processing conditions, making it critical to have quick and robust quality control tools in place. The weak polyelectrolyte nature of the fibers was considered in order to define the adequate solvent conditions for the rheological evaluation of the suspensions. Secondly, an improved dispersion method using ethylene glycol was developed in order to ensure optimal hydration of the dry fiber. The effect of fiber concentration was then studied both under steady-shear and oscillation tests. The dry matter concentration for the rapid rheological method was set at 4 w/w% above the experimental critical concentration or percolation threshold.

Cite this publication as follows:
Debon S, Wallecan J, Mazoyer J: A rapid rheological method for the assessment of the high pressure homogenization of citrus pulp fibres, Appl. Rheol. 22 (2012) 63919.

This paper discusses the influence of fat type in the structure of ice cream, during its production by means of rheo-optical analysis. Fat plays an important part in the ice cream structure formation. It's responsible for the air stabilization, flavor release, texture and melting properties. The objective of this study was to use a rheological method to predict the fat network formation in ice cream with three types of fats (hydrogenated, low trans and palm fat). The three formulations were produced using the same methodology and ratio of ingredients. Rheo-optical measurements were taken before and after the ageing process, and the maximum compression force, overrun and melting profile were calculated in the finished product. The rheological analysis showed a better response from the ageing process from the hydrogenated fat, followed by the low trans fat. The formulation with palm fat showed greater differences between the three, where through the rheological tests a weaker destabilization of the fat globule membrane by the emulsifier was suggested. The overrun, texture measurements and meltdown profile has shown the distinction on the structure formation by the hydrogenated fat from the other fats.

Cite this publication as follows:
Su F, Lannes SCS: Rheological evaluation of the structure of ice cream mixes varying fat base, Appl. Rheol. 22 (2012) 63871.

Dynamic oscillatory and creep tests are two common rheological methods used to determine viscoelastic properties. In the food industry, these tests are generally performed in the linear viscoelastic region, providing information on food structure and behavior over a range of timescales. However, this small-strain testing gives an incomplete picture of structural deformation and breakdown. Nonlinear oscillatory and creep testing, on the other hand, may yield a more complete fingerprint of food structural behavior. In this study, whey protein isolate (WPI)/k-carrageenan gels with different structures were studied under large amplitude oscillatory shear (laOS) and creep tests to determine the impact of structure on nonlinear oscillatory and creep behavior, and to examine correlations between nonlinear oscillatory and creep parameters. Evaluated structural types comprised a homogeneous protein gel, a bicontinuous gel, in which both WPI and k-carrageenan exhibited a continuous network, and a carrageenan continuous gel. Creep data were fit to 4-element Burgers models for further analysis, and the predicted compliance values were found to be in agreement with experimental data (R2 ≥ 0.90). Carrageenan continuous gels showed the greatest degree of nonlinearity under laOS (25 % strain), while homogeneous gels displayed the least. Nonlinear oscillatory data was found to correlate (R2 > 0.7, p < 0.05) with parameters used in the 4-element Burgers model. Hence, nonlinear viscoelastic behavior among materials may be evaluated by both creep data and nonlinear oscillatory data. However, nonlinear oscillatory data gives a quantitative measure of the type and extent of nonlinear behavior, while creep data indicates only the presence of nonlinear behavior. By combining information on structural behavior derived from nonlinear oscillatory and creep data, it is possible to determine nonlinear behavior over a wide range of timescales, yielding insight into structural deformation and breakdown under application of stress or strain at different rates.

Cite this publication as follows:
Melito HS, Daubert CR, Foegeding EA: Creep and large amplitude oscillatory shear behavior of whey protein isolate/.-carrageenan gels, Appl. Rheol. 22 (2012) 63691.

Simulations are performed to investigate the flow of a shear-thinning, non-Newtonian fluid in a collapsed elastic tube and comparisons are made with experimental data. The fluid is modeled by means of the Bird- Carreau viscosity law. The computational domain of the deformed tube is constructed from data obtained via computer tomography imaging. Comparison of the computed velocity fields with the ultrasound Doppler velocity profile measurements show good agreement, as does the adjusted pressure drop along the tube.s axis. Analysis of the shear rates show that the shear-thinning effect of the fluid becomes relevant in the crosssections with the biggest deformation. In fact, the maximum shear rate is about a factor of thirty larger than its corresponding maximum value in the undeformed tube, and the viscosity is reduced by a factor of two. The effect of the shear-thinning behavior has also been compared with identical simulations carried out for a Newtonian fluid.

Cite this publication as follows:
Tanner FX, Al-Habahbeh AA, Feigl KA, Nahar S, Jeelani SJA, Case WR, Windhab EJ: Numerical and Experimental Investigation of a Non-Newtonian Flow in a Collapsed Elastic Tube, Appl. Rheol. 22 (2012) 63910.

Cite this publication as follows:
Taj D, Savin T: International Workshop on Nonequilibrium Thermodynamics (IWNET 2012) and 3rd Lars Onsager Symposium, Appl. Rheol. 22 (2012) 274.

Cite this publication as follows:
Acker P, Chateau X, Ovarlez G, Toussaint F: Flocculated suspensions: from microstructure to macroscopic behavior, Appl. Rheol. 22 (2012) 269.

Cite this publication as follows:
Fischer P: Polymer Physics - Applications to Molecular Association and Thermoreversible Gelation (F. Tanaka), Appl. Rheol. 22 (2012) 235.

Generally, fly ashes (FA) could function as either semi-reinforcing or non-reinforcing fillers in polymeric systems, depending on particle size, specific surface areas and surface chemistry of FA particles. Typically, FA particles are spherical with smooth surfaces having significant influences on viscoelastic and mechanical properties. Additionally, the presence of heavy metals in FA particles could play role on degradation process of rubber molecules to some extent. In this article, the storage instability and thermal aging properties of FA filled natural rubber (NR) compounds were focused via changes in viscoelastic responses. Results obtained reveal that the storage duration of FA filled NR compounds leads to decreases in elastic modulus and molecular weight, particularly in the compounds with high FA loading. By replacing NR with polyisoprene (IR) containing no non-rubber substances, the storage stability is significantly enhanced. It is believed that the presence of metal ions in both FA and non-rubber substances in NR could catalyze the degradation process of rubber molecules. Such degradation process could effectively be suppressed by the addition of amine-based antioxidant.

Cite this publication as follows:
Saowapark T, Sae-oui P, Sombatsompop N, Sirisinha C: Storage Instability of Fly Ash Filled Natural Rubber Compounds, Appl. Rheol. 22 (2012) 55414.

The influence of polymeric dispersants containing different functional groups on the suspension behaviour of titania pigment slurry was investigated. The dispersants chosen were polyacrylic acid and modified polyacrylamides including homo and copolymers modified with carboxylate and/or hydroxyl groups. The pigment slurry rheology was strongly affected by both pH and dispersant chemical groups. The inorganic coating layer on the titania surface is not smooth, but rough or porous. The surface roughness of the pigment can generate additional contribution to the affinity of the dispersants for adsorption.

Cite this publication as follows:
Farrokhpay S: Rheology of titania pigment slurry, Appl. Rheol. 22 (2012) 55285.

The T-bar rheometrical tool (Brookfield Engineering laboratories, Inc.) is a slender rod which is placed in a material and rotated horizontally about its short axis by a vertical shaft. The torque on the shaft from laminar flow of material around the rod is determined by the material.s rheological properties. T-bar experiments for a Newtonian liquid are shown to agree closely with existing theory. For yield stress materials an approximation is derived for the torque on a rotating T-bar which is supported by experiments on a range of materials. The torque for very slow rotational speed is insensitive to boundaries beyond a few T-bar diameters and is shown to correlate with the material.s yield stress and other non-Newtonian parameters. A stepdecrease in torque for each half-revolution of the T-bar was shown by some materials and possible origins of this effect are discussed.

Cite this publication as follows:
Anderson VJ, Meeten GH: Interpretation of T-bar tool measurements for yield stress materials, Appl. Rheol. 22 (2012) 55370.

Control of food or bolus flow properties is part of several strategies to address aspiration pneumonia in dysphagic patients. An important alternative is the use of prescribed ready-to-use (RTU) oral nutritional supplements (ONS) specially designed for the nutritional support at different stages of dysphagia. However, it is clear that there are significant differences among products designed for the same level or stage of dysphagia. On the other hand, videofluoroscopy has become a key technique for the evaluation of swallowing and, thus, dysphagia. In this study, a new approach for designing RTU ONS products, specifically spoon-thick consistency products, has been carried out. The scientific approach has been based, first, on the characterization of the rheological properties of a standard barium-based commercial product used in videofluoroscopy studies and, then, matching the viscous flow properties of the RTU ONS product accordingly, by taking into consideration both formulation and process conditions. The results obtained clearly suggest that it is possible to obtain an excellent viscous flow behaviour similarity of both swallow barium test feed and RTU ONS produced at industrial scale. In this sense, both linear viscoelasticity properties and non-linear relaxation modulus have to be optimised to obtain the rheological similarity previously mentioned.

Cite this publication as follows:
Brito-delaFuente E, Staudinger-Prevost N, Quinchia LA, Valencia C, Partal P, Franco JM, Gallegos C: Design of a new spoon-thick consistency oral nutrition supplement using rheological similarity with a swallow barium test feed, Appl. Rheol. 22 (2012) 53365.

Cite this publication as follows:
I Balazs: The International Conference on Bio-Based Polymers and Composites 2012, Appl. Rheol. 22 (2012) 268.

Cite this publication as follows:
Wagner C: Joint Focus Session Rheology of the German Rheological Society (DRG) together with the German Physical Society (DPG), Appl. Rheol. 22 (2012) 213.

In-vitro small intestinal flow characteristics of a shear thinning fluid are investigated by transient '2-wave'-squeezing of an elastic tube under different speeds of peristalsis. Such peristaltic flow is the essential physiological transport mechanism in the gastro-intestinal tract. The peristalsis involves both expansion and contraction type of flow (crest and trough of a wavelength). We met the challenge of implementing the UVP technique for monitoring the velocity fields during appropriate peristaltic propulsion of a shear thinning fluid through an elastic tube (in vitro modeled small intestine). The higher wave speed of peristalsis results in higher magnitude of back flow velocity (negative) both in the wave crest and trough regions with positive value being adjacent to the tube wall. In addition, the approximated wall shear rates at the wave trough are also found to be higher than those in the wave crest. The higher value of back flow is expected to be responsible for the improved mixing and convection leading to higher mass transport through the intestinal wall. The measured pressure difference between crest and trough of a peristaltic wave increased, as the wave speed got faster. However, the crest region showed a higher pressure compared to the trough region since the magnitude of back flow velocity in the wave trough is found to be much higher compared to that in the wave crest.

Cite this publication as follows:
Nahar S, Jeelani SAK, Windhab EJ: Peristaltic flow characterization of a shear thinning fluid through an elastic tube by UVP, Appl. Rheol. 22 (2012) 43941.

Ultrasonic Velocity Profiling (UVP) is a powerful technique for velocity profile measurements in research and engineering applications as it is the only available method that is cost-effective, relatively easy to implement and applicable to opaque fluid suspensions, which are frequently found in industry. UVP can also be combined with Pressure Drop (PD) measurements in order to obtain rheological parameters of non-Newtonian fluids by fitting theoretical rheological models to a single velocity profile measurement. The flow properties of complex fluids are almost exclusively obtained today using commercially available instruments, such as conventional rotational rheometers or tube (capillary) viscometers. Since these methods are time-consuming and unsuitable for real-time process monitoring, the UVP+PD methodology becomes a very attractive alternative for in-line flow behavior monitoring as well as quality control in industrial applications. However, the accuracy of the UVP+PD methodology is highly dependent on the shape and magnitude of the measured velocity profiles and there are still a few problems remaining with current instrumentation and methods in order to achieve the robustness and accuracy required in industrial applications. The main objective of this research work was to optimize an UVP+PD system by implementing new transducer technology and signal processing techniques for more accurate velocity profile measurements as well as rheological characterization of complex fluids under industrial/realistic conditions. The new methodology was evaluated in two different pipe diameters (22.5 and 52.8 mm) and tested with three different non-Newtonian fluids in order to obtain a wide range of rheological parameters. Results were also compared to conventional rotational rheometry and tube viscometry. It was found that rheological parameters obtained from accurate velocity data across the pipe radius, especially close to pipe walls where the velocity gradient is high, showed better agreement to conventional rheometry than when compared to results obtained using profiles measured with conventional UVP instrumentation and commercial software (Met- Flow SA Version 3.0). The UVP+PD method is now more robust and accurate. The main challenge remaining is to successfully implement a complete non-invasive system in industrial processes that is able to achieve real-time and accurate complex flow monitoring of non-Newtonian fluid suspensions.

Cite this publication as follows:
Kotze R, Wiklund J, Haldenwang R: Optimization of the UVP+PD rheometric method for flow behavior monitoring of industrial fluid suspensions, Appl. Rheol. 22 (2012) 42760.

Ultrasonic Velocity Profiling with Pressure Drop (UVP+PD) is a technique, which allows the measurement of the shear rate dependent viscosity non-invasively in a laminar pipe flow. To assess the performance of different data processing approaches for the extraction of the rheometric values, model fluids are characterized under well defined flow conditions created with a piston setup. Considering the shear rate range available in the pipe flow, a good quantitative agreement is found between the in-line measurements and the off-line measurements made with a rotational rheometer

Cite this publication as follows:
Birkhofer B, Debacker A, Russo S, Ricci S, Lootens D: In-line rheometry based on ultrasonic velocity profiles: comparison of data processing methods, Appl. Rheol. 22 (2012) 44701.

Measurements of the viscosity of non-Newtonian fluids and suspensions having a solid volume fraction of about 30% or more is of major interest from an industrial point of view. Cement paste and cement grouts for injection grouting applications, with water to cement ratios typically in the range of 0.4 and 0.6 - 0.8 by weight, are two examples of industrial fluid systems. Few in-line techniques are available on the market that can be used for these fluid systems and under realistic field conditions. The so-called UVP+PD in-line rheometry method combining the Ultrasound Velocity Profiling (UVP) technique with Pressure Difference (PD) measurements is a promising new tool for industrial applications. This paper presents an initial pre-study that aims to demonstrate the feasibility of the UVP+PD method using cement grouts for process monitoring and control of grouting applications under realistic field conditions. The UVP+PD method was tested and found successful for continuous in-line measurements of concentrated micro cement-based grouts with water/cement ratios of 0.6 and 0.8. The test set-up consisted of a combination of an experimental .flow loop. and a conventional field grouting rig - UNIGROUT, from Atlas Copco. The rheological properties were determined, directly in-line and the parameters obtained were subsequently compared with off-line measurements using a conventional rotational rheometer.

Cite this publication as follows:
Wiklund J, Rahman M, Hakansson U: In-line rheometry of micro cement based grouts . a promising new industrial application of the ultrasound based UVP+PD method, Appl. Rheol. 22 (2012) 42783.

The in-line rheometer concept based on the combination of the ultrasonic velocity profiling (UVP) technique and pressure difference (PD) measurements was utilized for investigating the influence of particle concentration and size distribution on the rheology of particulate suspensions in pipe flow under realistic industrial process conditions. Well defined model suspensions were used, consisting of 11 mm and 90 mm diameter polyamide particles suspended in rapeseed oil at concentrations ranging from 1 to 25 % by volume. The variation of concentration and particle size distribution had the expected effects on the shear viscositiy of the investigated unimodal and bimodal suspensions. The in-line results showed that the investigated suspensions exhibit Sisko flow behavior and demonstrated that the UVP+PD method can be used to determine the flow behavior of complex fluids and suspensions, even at high solid concentrations, under industrial conditions in-line. The obtained inline results were in good agreement with measurement data obtained using a conventional rotational controlled- stress rheometer. Limitations of commercially available transducer technology were identified and other possible sources of inaccuracy of the UVP+PD method were investigated. Several improvements of the UVP+PD measurement method were proposed.

Cite this publication as follows:
Wiklund J, Birkhofer B, Jeelani S, Stading M, Windhab EJ: In-line rheometry of particulate suspensions by pulsed ultrasound velocimetry combined with pressure difference method, Appl. Rheol. 22 (2012) 42232.

Cite this publication as follows:
Elkins C, Aumaitre E: Lorentz Center Workshop: Dynamics of Complex Fluid-Fluid Interfaces, Appl. Rheol. 22 (2012) 145.

We constructed a macroscopic model illustrating behavior of a single entanglement knot of macromolecules in a melt and examined its behavior at different deformation rates. A model consists of flexible elastic strips, which are tied in a granny knot (modeling not a real geometrical form of entanglements but their behavior at relatively easy sliding). This scheme models the situation when elastic energy exceeds the energy of the Brownian motion. The behavior of a knot chosen for modeling is different at low and high deformation rates. In the previous case knots disentangle as predicted by the .tube. model, elastic strips slip out a knot and this is an illustration of flow. In the latter case, knots tighten up, further extension of strips leads to the increase in stresses up to breakup of a strip. This effect imitates the transition from the flow to the rubbery-like behavior of polymer melts, when flow becomes impossible due to the formation of quasi-permanent entanglements. The general dimensionless correlation for the process under discussion has been proposed.

Cite this publication as follows:
Malkin A, Semakov A, Kulichikhin V: Macroscopic modeling of a single entanglement at high deformation rates of polymer melts, Appl. Rheol. 22 (2012) 32575.

The methodology of evaluation of rheological parameters of non-Newtonian fluids on the basis of rotational viscosimetry data has been described, which is based upon rigorous solution of Couette flow equation and considers informational content of experiments. Class of models is formed for rheologically stationary systems, biviscosity ones included. Functional features of methodology and its generalization for the interpretation of rheological properties measurements results according to plans of experiments have been outlined.

Cite this publication as follows:
Myslyuk M, Salyzhyn I: The evaluation of rheological parameters of non-Newtonian fluids by rotational viscosimetry, Appl. Rheol. 22 (2012) 32381.

Cementitious pastes prepared with air-entraining admixtures (AEA) are very sensitive to mix procedures and environmental conditions. Some of the effects of AEA on the properties of cementitious material are discussed in literature, although for the most part, only in the hardened state. However, the impact temperature has on air-incorporation during the early age stages and on consolidation has been little investigated and as such, is the objective of this work. Thus, pastes formulated with Portland cement and air-entraining admixtures are evaluated in this work with a focus on the role temperature plays in the early age behavior. The results show that air-incorporation was affected by environmental conditions which caused changes in the kinematic viscosity and rate of consolidation.

Cite this publication as follows:
deOliveiraRomano RC, Pileggi RG: Temperature's role in the rheological behavior of cementitious pastes prepared with air-entraining admixtures, Appl. Rheol. 22 (2012) 24333.

Bitumen is used as binder for asphalted roads worldwide. However the service life of asphalt roads is limited due to the viscoelastic properties of bitumen. The lack of yield stress and the flow behavior at high temperatures as well as the stiffness of bitumen at lower temperatures results in the main failure sources of asphalt roads. Many polymers have been used in industry to improve the rheological behavior of bitumen and consequently, service life of roads. The polymers are commonly added to hot bitumen under stirring in order to achieve a stable dispersion. However, most polymers show little to no miscibility in bitumen, which requires long dispersion times and may lead to oxidation of bitumen and degradation of the polymers. Poor miscibility of the dispersed polymer and the bitumen matrix can result in phase separation during transport of molten bitumen, leading to a heterogeneous binder and further failure of the paved road, which is a common problem in the paving industry. Rubber pre-treating leads to a faster mixing process without compromising dispersion quality and stability. Bitumen was modified with SBS, ground rubber and chopped fibers of polymers. These fibers, which showed good stability, can be considered for the future as bitumen modifiers. To evaluate the stability of the modified bitumen, we propose a stability index.

Cite this publication as follows:
Navarro-Gonzalez M, Wagner MH: Storage stability of bitumen modified by the addition of ground rubber, swollen SBS and polymeric short fibers, Appl. Rheol. 22 (2012) 24691.

The principle of silicate layer reinforcement in a polymer matrix is known as the formation of a 3D network of single layers. Nevertheless there is still a lack of knowledge about the physical ageing of nanocomposites respectively the stability of this network over time. As most of the nanocomposite applications have a more or less long-term shelf life respectively storage time, the investigation of the storage-time dependent behavior of the layered 3D structure in a polymer matrix is of major interest. In this study, the rheological (shear and elongational) properties of different polypropylene nanocomposites were measured using a cone-plate rheometer and a Rheotens apparatus. To evaluate the structural stability over time, the samples were measured immediately after processing and after defined periods (18 and 36 months) stored under constant conditions. Furthermore the network structure was determined using XRD and TEM measurements. The results show, that, depending on the clay rate and especially the degree of exfoliation, the rheological properties are changing significantly. Thereby chain splitting caused by photo-oxidative degradation, leading to a loss in molecular weight, as well as a weakened 3D network by reverse diffusion of the polymer chains out of the clay gallery and/or reagglomeration of the nanoparticles are the two main factors.

Cite this publication as follows:
Laske S, Witschnigg A, Mattausch H, Kracalik M, Pinter G, Feuchter M, Maier G, Holzer C: Determining the ageing of polypropylene nanocomposites using rheological measurements, Appl. Rheol. 22 (2012) 24590.

Cite this publication as follows:
Hietala S: Nordic Rheology Conference 2011, Appl. Rheol. 22 (2012) 46.

The measurement of elongational viscosity still evokes a series of problems in comparison with the relatively well-established measurement of shear viscosity. Recently new techniques have appeared enabling measurement of elongational viscosity with the samples for which the aspect ratios of their geometrical shapes (i.e. length vs. width (diameter)) can attain moderate values, i.e. not necessarily of a longitudinal character as in the case of earlier techniques. The aim of this contribution is to experimentally demonstrate the invariantness of transient uniaxial elongational viscosity measured with respect to a rectangular shape and thickness of LDPE samples using a SER Universal Testing Platform fixed in an Anton Paar MCR 501 host system. The width of the samples was varied within the range 2.1-12.7 mm and thickness altered within 0.1-1 mm. An advantage of fixing polymer samples directly to both drums (if possible) over the application of clamps is documented.

Cite this publication as follows:
Filip P, Svrcinova P: Measurement of elongational viscosity of polymer melts using SER Universal Testing Platform, Appl. Rheol. 22 (2012) 14776.

We applied the creep test that allows obtaining rheological information in the long-time domain (low-frequency range) that is not reachable by the use of the dynamic frequency sweep test to characterize the linear viscoelastic properties of polyethylene melts for industrial research and development. We considered the time scale for the creep test and what this imposes as limitations on the ability to make such measurements on a large group of samples. For the long- time creep test in the molten state at high temperatures, polyethylene demands very good stabilization with anti-oxidation packages to allow one to obtain useful data. The time for the sample relaxation from mounting and trimming in the parallel plate geometry of the controlled-stress rheometer prior to initiation of a creep test was also considered. The issue of what stress level to use in the linear viscoelastic region was addressed as was the issue of signal to noise. The creep test was performed within 4 hours for practical use, and the frequency range was extended down 10-4 rad/s. We tested several polyethylene samples as examples taking account of above variables and showed that the data obtained by the creep method overlapped well with low frequency end of the dynamic frequency sweep data. By testing several high molecular weight resins having broad molecular weight distribution and/or long chain branching, we demonstrated the utility of this methodology.

Cite this publication as follows:
Inn Y, Rohlfing DC: Application of Creep Test to Obtain the Linear Viscoelastic Properties at Low Frequency Range for Polyethylene Melts, Appl. Rheol. 22 (2012) 15260.

A high torque vane rheometer is used to measure the yields stress of cement-based materials. It is shown that this apparatus is suitable for the evaluation of the yield stress of various concretes and mortars in the fresh state in comparison with slump tests realized with ASTM Abrams cone. Then, the rheological properties (yield stress and shear flow behaviour) of a homogeneous kaolin clay suspension are studied with the apparatus and favourably compared with other rheometers and geometries.

Cite this publication as follows:
Estelle P, Lanos C: High torque vane rheometer for concrete: principle and validation from rheological measurements, Appl. Rheol. 22 (2012) 12881.

An effort is made to determine theoretically the new rheological properties of a rheologically defined non-Newtonian fluid as a result of the addition of particles in the original fluid. A theoretical model is proposed to determine the rheological properties of a dilute suspension of infinite-length round particles for a Power-law fluid, which is treated as a homogeneous fluid with new rheological properties. The equations of a two-dimensional, dilatational, creeping, steady-state flow of a near-Newtonian fluid around a solid circular particle are developed and solved. The solution is obtained by computation of the dissipation relation and is based on the change of the shear rate in a shear flow of the suspension. The model is solved numerically. The resulting from the particle addition fluid is found to be more shear-thinning in comparison to the original. Experimental evidence from the literature supports the soundness of the present findings.

Cite this publication as follows:
Chernov V, Natan B: A simplified model for the evaluation of the rheological properties of a suspension of solids in a power-law fluid, Appl. Rheol. 22 (2012) 15163.

Cite this publication as follows:
Mothe CG: 1st Brazilian Congress of Rheology (CBR 2011), Appl. Rheol. 21 (2011) 364.

Viscoelastic properties are traditionally measured using sophisticated instrumentation, and the high cost of these rheometers may limit utility. This research attempts to enable viscometers that can provide a torque-time response, with vane attachment and a recommended cup size, to measure viscoelastic properties. Phase angles and shear moduli of model systems (gelatin and polyacrylamide gels) were calculated using torque-time response and deformation zone concept. The methods were applied to data obtained from Brookfield YR-I viscometer and the calculated values were compared with the data obtained from oscillatory testing on a stress controlled rheometer. The methods were improved in several areas by testing different cup sizes, rotational speeds, and viscometers and correcting torque-time responses to obtain most accurate results possible. The developed method, along with the torque-time response obtained from the viscometer, was capable of measuring viscoelastic parameters for the tested materials and further development could design a new quality control device directed towards viscoelastic property measurement.

Cite this publication as follows:
Tanjore D, Daubert CR: A vane-in-cup approach to measure viscoelastic properties of gelatin gels through torque-time responses from Brookfield YR-I viscometer, Appl. Rheol. 21 (2011) 63172.

Concentrated gypsum slurries used for wallboard production are studied using shear and elongational rheometers. It is shown that the rheological behavior of different slurry compositions can be sufficiently accurately described in the framework of the Ostwald-de Waele power law, which reproduces both shear and elongational experimemtal data with sufficiently close values of the consistency and flow behavior indexes for each slurry composition studied.

Cite this publication as follows:
Sinha-Ray S, Srikar R, Lee CC, Li A, Yarin AL: Shear and elongational rheology of gypsum slurries, Appl. Rheol. 21 (2011) 63071.

We herein describe a set of rheological measurements that were carried out in order to characterize the solidification of photopolymers. The solidification depends on the length of time of exposure to UV light, and the intensity of that light, which reduces with distance from the irradiative surface. Liquid prepolymer was solidified inside the gap of a parallel disk rheometer by irradiation of the prepolymer with UV light through a fixed quartz disk. The rheological time-dependent changes were measured and analyzed for both unidirectional and oscillatory shear. The results were compared with those obtained by direct measurement in the absence of shear. When the thickness of the sample was less than 0.1 mm, the analysis for unidirectional shear flow yielded a reasonable agreement for both critical exposure and solidified depth. When the thickness was greater than 0.1 mm, the application of unidirectional shear delayed the start of the solidification but then caused it to occur more rapidly. This dependence of the solidification on the thickness of the sample was more significant for dispersed systems of nanotubes and for dynamic measurements made under oscillatory shear. The increase in viscosity due to photopolymerization was also estimated, and its effect was discussed.

Cite this publication as follows:
Darsono N, Mizunuma H, Obara H: Rheological study of the solidification of photopolymer and dispersed nanotube systems, Appl. Rheol. 21 (2011) 63566.

A new conceptual non-contact method for liquid viscosity measurement in capillary tube using mobile phone as the data acquisition facility is proposed. The video and image for the capillary force driven flow of the test liquid was recorded by the phone camera. After the imaging reconstruction of the flow velocity in the horizontal capillary and the capillary head in the vertical direction, a digital image processing software was developed to calculate the liquid viscosity in MATlaB 2007b environment, recurring to the established theoretical correlation for flow mechanics. To demonstrate the feasibility and accuracy of the method, 10 groups of liquid were measured and the results were compared with the data obtained from a standard rotating viscometer. The relative error was found falling in the range of 0 ~ 20 %. This study establishes a pervasive low cost way for viscosity measurement of various solutions.

Cite this publication as follows:
Yang Y, Wang H, Liu J: Mobile Phone Enabled Pervasive Measurement of Liquid Viscosity, Appl. Rheol. 21 (2011) 63890.

A new method is developed to determine the rheological and tribological behaviour of viscoplastic fluids using a back extrusion test. In back extrusion geometry, the material is forced to flow in the gap between the inner and the outer cylinder. Such a flow is modelled by a Bingham constitutive law under different wall boundary conditions (stick, slip with friction and perfect slip). When steady-state flow is reached, an apparent shear rate is computed. The analysis of the inner cylinder penetration force versus the penetration depth helps us to develop a method to identify the fluid rheological and tribological properties. This method is based on an inverse analysis to identify the fluid behaviour parameters from experiments performed at different ram velocities and with different apparatus geometries. In order to study more complex fluids (Herschell-bulkley rheological behaviour, for example), an equivalent flow curve is plotted from tests characterized by different average shear rates. The tribological behaviour is identified using different wall boundary conditions, varying the surface roughness of the cylinders. The method is applied to oil/sugar suspension and plasticine. Rheological and tribological behaviours are identified and results are compared with those obtained under steady state shear flow. The obtained rheological parameters are close to those provided by the common rheological methods (difference lower than 15 %).

Cite this publication as follows:
Perrot A, Melinge Y, Estelle, Rangeard D, Lanos C: The back extrusion test as a technique for determining the rheological and tribological behaviour of yield stress fluids at low shear rates, Appl. Rheol. 21 (2011) 53642.

The influence of short fibre addition on the rheological behaviour of different non-Newtonian fluids is investigated experimentally. Two types of suspending fluids are considered: power-law shear thinning fluids and yieldstress shear-thinning fluids. The power-law suspending fluids consist of aqueous xanthan solutions at different concentrations. The yield stress fluids are mortar tile adhesives characterised by different rheological parameters. The flow curves of the suspensions at different fibre contents are determined at controlled stresses. Three rheological parameters are inferred from the flow curves: the yield stress, the consistency and the fluidity index. The influence of the fibres on the rheological behaviour of purely shear-thinning fluids is found to be quite similar to what can be expected for Newtonian suspending fluids. On the other hand, addition of fibres to yield stress granular fluids leads to a qualitatively different change of their rheological properties compared to the case of Newtonian suspending fluids. In particular, it is found that the fibres can lead to the decrease of the apparent viscosity and the yield stress for low fibre concentrations in the case of granular suspending fluids. Our experimental findings indicate that the models for fibre suspensions in Newtonian solvents cannot be used straightforwardly in the case of fibre suspensions in granular materials such as building materials, ceramic materials, etc.

Cite this publication as follows:
Ouari N, Kaci A, Tahakourt A, Chaouche M: Rheological behaviour of fibre suspensions in non-Newtonian fluids, Appl. Rheol. 21 (2011) 54801.

The rheological behavior of the olive oil-in-water emulsions has been studied by varying the oil to water ratio as well as the surfactant concentration. The viscoelastic property of the olive oil emulsions was investigated with a cone-and-plate system, using a Bohlin C-VOR Rheometer. The obtained results indicated that the emulsions with greater oil and surfactant concentrations are highly packed systems with greater interdroplet interactions as well as higher critical strain. The viscoelastic property of the emulsions can be enhanced by increasing the oil concentration. The elastic modulus of the emulsions was always predominant over the viscous modulus, thereby emphasizing the elastic character of the above mentioned emulsions. The emulsion with a higher oil composition shows greater elasticity, which implies a strong dynamic rigidity of the emulsions. A high oil composition also enhanced the structural integrity as well as the interdroplet interactions of the emulsion.

Cite this publication as follows:
Tan H, Misran M, Khoo S: Viscoelastic Behavior of Olive Oil-in-Water Emulsion Stabilized By Sucrose Fatty Acid Esters, Appl. Rheol. 21 (2011) 54599.

The behaviour of silicone-oil suspensions of titanate nanorods coated with polypyrrole base in electric field has been investigated. Unlike suspension of globular particles of neat polypyrrole, rod-like particles show a stronger electrorheological (ER) effect corresponding to high rigidity of the structure. A great influence of the oil viscosity on the ER efficiency was observed. A good reproducibility of the effect and a fast response to the switching-on and -off the electric field has been confirmed by monitoring the time course of shear stress under controlled shear rate.

Cite this publication as follows:
Mrlik M, Pavlinek V, Saha P, Quadrat O: Electrorheological properties of suspensions of polypyrrole coated titanate nanorods, Appl. Rheol. 21 (2011) 52365.

An apparatus for small angle light scattering (SALS) and light transmission measurements under shear was built and tested at the University of Massachusetts Amherst. As a new development, the polarization direction can be rotated by a liquid crystal polarization rotator (LCPR) with a short response time of about 20 ms.The experiments were controlled and analyzed with a labVIEWTM based code (labVIEW-TM 7.1) in real time. Quiescent and flow-induced crystallization experiments on isotactic poly-1-butene (iPB) were conducted to demonstrate the instrument and software capabilities. Software was designed with a modular approach, so that further modules can be added to investigate other systems such as polymer blends, colloidal suspensions, solutions with droplets etc. A replica of the SALS apparatus was custom built for ExxonMobil Research in Clinton NJ.

Cite this publication as follows:
Arora D, Nandi S, Winter HH: A new generation of light scattering device with real time data analysis for rheo-optical measurements, Appl. Rheol. 21 (2011) 42633.

Black liquor is the major by-product and biomass fuel of pulp mills, and the understanding of its thermophysical properties is essential for the improvement of the design and the operation of chemical recovery processes. In this work, the rheological behaviour of industrial samples of Eucalyptus globulus black liquor was investigated to study the influence of solids content ranging from 13 % for the white liquor sample, and from 30 to 65 % of dissolved solids for the black liquors, and of temperature from 298.15 to 338.15 K, covering shear rates from 0 to 1200 s-1. The black liquor showed a complex non-Newtonian behaviour, presenting at low shear rates a pseudoplastic behaviour, followed by a viscosity Newtonian plateau. The modified Quemada model gives an expression applicable to all the shear rate range, which was used to describe the flow curves for the viscosity of E. globulus black liquors samples. Moreover, a correlation based on a VTF model with parameters dependent on solids content was successfully developed for the viscosity data of the Newtonian plateau.

Cite this publication as follows:
Costa H, Egas A, Ferreira A, Lobo L: Rheology of Eucalyptus Globulus Kraft Black Liquor, Appl. Rheol. 21 (2011) 42533.

We have interpreted the results of shear creep data on samples of bread dough, tested in a parallel plate rheometer, by using a damage function model. Whilst the agreement between calculation and experimental results is satisfactory for the dough for stress levels less than 500 Pa, increasingly large deviations from the predictions occur for stress levels of 500 and 1000 Pa. This is in contrast with the behaviour in simple shearing, where agreement with the damage function model can be obtained up to shear stresses of several kPa. It is therefore of interest to see why the discrepancy between model predictions and experiments occurs in shear creep at such low stress levels. It is shown that edge fracture in a parallel-plate rheometer, due to the second normal stress difference, N2, is responsible for the deviations and the model behaves quite well for stress levels 300 Pa and below, where edge fracture is not important. Therefore the edge fracture instability, which depends on N2, limits the range of stress which can be applied in shear creep tests.

Cite this publication as follows:
Dai S, Qi F, Tanner R: Interpreting Shear Creep Data for Bread Dough Using a Damage Function Model, Appl. Rheol. 21 (2011) 45070.

We report unprecedented non-Einstein-like viscosity decrease of polymer melts by special low glass transition, Tg, inorganic tin fluorophosphate glass (Pglass) that is remarkably counter to widely accepted dispersions, suspensions, and composites theories. The well dispersed low-Tg Pglass dramatically decrease the polymer melt viscosity while increasing its Young's modulus in the solid state at low loading (<2%) however decreasing with high loading (>2%), making the hybrid Pglass/polymer solid material stronger yet easier to process in the liquid state. Disruption of the Nylon 6 melt dynamics, strong physicochemical interactions, and submicrometer nanophase separation (proved by rheometry, FTIR, DSC, SEM, NMR and XRD) are thought to be responsible for this experimental fact. This finding should beneficially impact our ability to prepare lower viscosity, very highly filled Nylon 6 melts from already existing materials and polymer processing methods such as injection molding and extrusion, making the simple strategy potentially widely applicable in a number of applications such as thinner barrier resistant thin films, composites, and membranes for heterogeneous catalysis.

Cite this publication as follows:
Meng Y, Otaigbe J: Mechanism of unexpected viscosity decrease of polymer melts by low-Tg inorganic phosphate glass during processing, Appl. Rheol. 21 (2011) 42654.

A set of 31 cosmetic emulsions, as the most frequent cosmetic dispersions, comprising lotions and creams (o/w, w/o), was analyzed by rheological procedures (RheoStress 300, Thermo Fischer Scientific) and by sensory profiling. The power law model was used for pseudoplastic body lotions and the Herschel-Bulkley model for viscoplastic creams to get basic rheological parameters (apparent viscosity, consistency parameter, yield stress value, plastic viscosity and flow behaviour index). The content of TiO2 in sun lotions probably caused better agreement with viscoplastic creams. Rheological analysis proved to be more suitable for the storage stability testing of the emulsion than sensory evaluation. Psychorheology was applied as a suitable complex method. Rheological parameters were compared to sensory texture attributes (removing from a package, ease of spreading, skin feel and thickness). Almost 60% of relationships among rheological and sensory parameters were statistically significant (P = 0.05). Considering relationships only between rheological and sensory characteristics (with each other), 46 % were statistically significant (P = 0.05). In the case of apparent viscosity and removing the lotion from a bottle the relationship was reliable enough (correlation coefficient 0.91) to estimate the sensory attribute by fast rheological measurement. The other statistically significant relationships (correlation coefficients 0.53.0.80) proved that the sensory texture acceptability of a cosmetic emulsion could be partly predicted by rheological analysis.

Cite this publication as follows:
Moravkova T, Stern P: Rheological and textural properties of cosmetic emulsions, Appl. Rheol. 21 (2011) 35200.

Rheological behaviour of culture broth stands as a fundamental parameter in bioprocess performances because it affects simultaneously the heat and mass transfer as well as the flow pattern. On-line measurements of rheological behaviour are hardly compatible with the operating condition with respect to accurate and stringent conditions imposed by cell culture strategy. Our scientific and technical objectives are (i) to develop and identify an experimental device enabling on-line rheometry and (ii) to discuss and compare on-line and off-line measurements. In this aim, a bioreactor was equipped with a derivation loop including a specific on-line rheometric device as well as additional physical and biological measurements (specific density, mass flow rate, electrical conductivity, pH,pO2 and temperature) during microbial cell cultures. In a first time, friction curves of calibrated ducts were established with Newtonian and non-Newtonian shear-thinning fluids. In a second time, axenic cultures with two microorganisms (bacteria and yeast exhibiting different sizes) were investigated in pure oxidative culture in order to produce biomass under high cell concentrations: ~ 40 to 110 gCDW/l for E. coli (bacteria) and ~ 75 to 105 gCDW/l for Y. lipolytica (yeast). Cell broths exhibited Newtonian behaviour for E. coli and shear-thinning behaviour for Y. lipolytica, which were both dependant on biomass concentration. On-line and off-line rheological measurements are consistent for E. coli and Y. lipolytica, but significantly differed. On-line estimated viscosity appears higher than off-line apparent viscosity. Several assumptions in relation with microorganism physiology and metabolism (size, morphology, surface properties, concentration, biological activity) could be formulated in agreement with scientific literature. On-line rheology brings new insight to investigate complex interaction between physical and biological phenomena.

Cite this publication as follows:
Manon Y, Anne-Archard D, Uribelarrea J, Molina-Jouve C, Fillaudeau L: Physical and biological study of cell cultures in a bioreactor: on-line and off-line rheological analyses, Appl. Rheol. 21 (2011) 35167.

The interaction between magnetic particles in a bed fluidized by a gas is determined by the magnetizing action of an externally applied magnetic field. As the strength of the field is increased there comes a point at which the bed transits from a fluidlike to a solidlike stable state. Interparticle attractive forces induced by the applied field causes chainlike agglomeration of the particles, which confers the stabilized structure with a mechanical strength. In this paper we report experimental results on the yield stress of fluidized beds of fine magnetic particles stabilized by an externally applied magnetic field. Our results show that, in analogy with magnetorheological fluids (MRFs), particle structuring determines essentially the yield stress of magnetofluidized beds (MFBs). Moreover, our work shows that the dependence of the yield stress on particle size, which stands as a controversial issue in the study of MRFs, can be understood from the analysis of the jamming transition as affected by the size of the particles and the strength of the field.

Cite this publication as follows:
Valverde JM, Espin MJ, Quintanilla MAS, Castellanos A: Jamming and rheology of fluidized beds of magnetized particles, Appl. Rheol. 21 (2011) 35179.

In this study the steady flow viscosity, complex viscosity and relative viscosity of PP/FeSi composite melts with filler contents up to x =0.7 (70 vol.%) of spherical Iron Silicon (FeSi) microparticles (in 10 vol.% steps) with diameter of d < 106 mm have been investigated. Plate-plate and capillary rheometry at different shear rate and angular frequency in the range from 0.12 to 16000 s-1 (rad/s) were used. The results show an inflection point at high filler contents x ≥ 0.4 (40 vol.%) and low shear rates (< 1 s-1) caused by particle/particle interactions.With increasing shear rate and angular frequency the typical shear thinning flow behaviour of polymer melts was found for all investigated filler contents. The viscosity increases with increasing filler content at constant shear rate and angular frequency.Time-temperature-superposition (TTS) and Cox-Merz relation were fulfilled at filler contents up to x =0.3 (30 vol.%). The results of complex viscosity were normalized to a superimposed master curve. The three parameter of the new modified Carreau model were calculated for PP melt and shifted by two factors depending on the filler content. Based on these modifications, the complex viscosity was calculated for each filler content up to x =0.3. The complex viscosity graphs were reduced to a general master curve of the investigated PP/FeSi composites up to x =0.3. Finally, the relative viscosity of the examined composites shows the best fit to the Quemada model

Cite this publication as follows:
Kirchberg S, Ziegmann G: Effect of Spherical Iron Silicon (FeSi) Microparticles on the Viscosity Behaviour of Polypropylene Melt, Appl. Rheol. 21 (2011) 35495.

Cite this publication as follows:
Clasen C: International Workshop on Rheology and Structural Design of Complex Fluids 2011, Appl. Rheol. 21 (2011) 185.

Cite this publication as follows:
Fischer P: Rheology of Particulate Dispersions and Composites (Rajinder Pal), Appl. Rheol. 21 (2011) 75.

This work takes a phenomenological approach to modeling the rheology of polymer/clay nanocomposites in (shear rate) γ ≤ 1 / s based on experimental observations [10]. The total stress was divided to three contributions: Matrix stress, σM, inter-particle (matrix/particle) stress, σP, and hydrodynamic stress σH. Based on the superposition of complex viscosities, η*, plotted against strain rate amplitude, γ0ω, at different nonlinear strain amplitudes, a modified Bingham-type constitutive equation proposed by Doiraswamy et. al [16] was used to model σMP while σH was modeled by using constitutive equation proposed by Lipscomb et. al [25] for ellipsoidal particles. The comparison between experimental and modeling results showed that steady hydrodynamic stress in simple shear flows scales with complex viscosities in oscillatory experiments when compared at γ = γ0ω. On the basis of this observation, the network-like behavior of the polymer nanocomposite was attributed to retarded chain dynamics as a result of polymer/clay interactions. In order to take into account the thixotropic behavior of network structure, the constitutive equation proposed by Coussot [18] was employed for modeling σMP. Both Coussot and Doraiswamy equations gave a reasonable quantitative prediction of transient stress in simple shear flow up to shear rates as high as γ = 0.1 / s.

Cite this publication as follows:
Nazockdast E, Nazockdast H: Rheological Modeling of Polymer/layered silicate Nanocomposites, Appl. Rheol. 21 (2011) 25434.

The composition of high concentration ash slurry requires careful selection of particle size distribution (PSD) to achieve the required rheological properties for efficient disposal through pipelines. In the present study, the maximum static settled concentration, CW-max, tests and rheological measurements were carried out for a total eighteen nos. of ash samples (nine nos. of fly ash samples and nine nos. of fly ash.bottom ash mixture samples) in the concentration range of 60 - 70 wt%. It was observed that the CW-max value reached maximum for the composition of mixture slurry consisting of fly ash and bottom ash with d50 as 6.4 μm and 144 μm respectively at a fixed blend ratio (weight ratio of fly ash to bottom ash) of 4:1. This was attributed to the packing effect and was correlated to the ratio of surface to surface separation for the coarse bottom ash particles, β, to the average fly ash particle size, d50-f, to achieve higher solids concentration. The rheological behaviour of the ash slurry samples were described by non-Newtonian power law model in the range of solids concentration studied. Also a substantial reduction in viscosity was observed for the same composition of mixture slurry sample which was attributed to the poly-dispersive characteristics of the ash particles. It was indicated that the slurry viscosity was very much influenced by particle size ratio (&lambda; = dlarge/dsmall) and volume fraction of solids. The study revels that the blending of fly ash and bottom ash at a controlled PSD may be employed for preparation of high concentration ash mixture slurry for pipeline transport.

Cite this publication as follows:
Senapati PK, Mishra BK, Sahu A, Kumar V: Effective composition of high concentration fly ash-bottom ash mixture slurry for efficient disposal through pipelines, Appl. Rheol. 21 (2011) 23480.

The rheological parameters (elastic modules and the yield stress) of binary mixtures of highly concentrated emulsions with different droplet sizes can be several times lower than additive values in a certain range of concentration. This is related to the proper packing of small droplets between larger ones without compression of droplets. While the yield stress is practically absent for these uncompressed droplets, the rather high storage modulus demonstrates the significance of interdroplet interaction in this system.

Cite this publication as follows:
Foudazi R, Masalova I, Malkin A: The rheology of binary mixtures of highly concentrated emulsions, Appl. Rheol. 21 (2011) 25326.

In this paper, the role of extensional viscosity in different paper coating processes was evaluated. Numerical models for the various coating application processes (blade coating, film coating, and curtain coating) were constructed to calculate the extensional rate. Different rheological methods were employed to measure extensional viscosity versus extensional rate for model coating colour systems. Pilot coater trials were carried out to study the performance of each model coating colour in curtain, blade and film coating. It was demonstrated that extensional viscosity of model coating colours depends on the rate of extension, and colours can be extension thickening or extension thinning.With the numerical calculation results of extension rate in coating application processes, the extensional viscosity test results of model coating colours were matched to their performance in pilot coater experiments. It was shown that increasing the extensional viscosity measured at the appropriate extension rate that exists in blade or rod metering increased blade or rod load. Misting in film coating was reduced by low extensional viscosity measured at the appropriate extension rate. Cratering in curtain coating was reduced by increasing extensional viscosity measured at the appropriate extension rate. It was further concluded that the extensional viscosity can be used to predict the coating performance only if it is measured at the prevailing extensional rate of the specific coating process speed.

Cite this publication as follows:
Yang A, Salminen P, Vervoort S, Endres I, Bachmann H: Role of Extensional Viscosity in Paper Coating, Appl. Rheol. 21 (2011) 23607.

This paper presents an experimental facility that allows simultaneous viscosimetric and Particle Image Velocimetry measurements on concentrated suspensions in a wide-gap Couette rheometer. The experimental procedure is detailed: the optical characteristics of the index-matched suspension are carefully studied, the bottom end effect on both the viscosimetric measurements and the recorded velocity profiles are analysed. First the experimental procedure is tested on a Newtonian fluid whose viscosity is known. The spatial and time resolutions of our device are shown to be 200 μm and 100 ms. The precision of the local viscosity measurement is evaluated to better than 4 %. Then we show that the device can be used to characterize the rheological behaviour of a 47 %-concentrated suspension of 30 μm spheres. According to the particles large size, the Brownian motion can be neglected. However, colloidal interaction are still noticeable.

Cite this publication as follows:
Blanc F, Peters F, Lemaire E: Particle Image Velocimetry in concentrated suspensions : Application to local rheometry, Appl. Rheol. 21 (2011) 23735.

The effects of particle concentration, particle size and temperature on the shear rheology of suspensions of silica nanoparticles are studied. Sterically or electrostatically stabilized silica nanoparticle dispersions with sizes ranging from 5 - 75 nm and particle volume fractions ranging from 0.22 - 25 % exhibited a constant viscosity within the shear rate range of 1 - 200 s-1. There is a non-linear relationship between the concentration and the viscosity of these dispersions that depends on the radii and surface energy of these nanoparticles.We propose an effective maximum packing fraction model based on the concept of an effective particle radius, which takes into account the thickness of the electrical double layer and the surface coating material. The viscosities of all the dispersions collapse onto a universal curve as a function of the volume fraction normalized by the effective maximum packing fraction.

Cite this publication as follows:
Metin C, Bonnecaze R, Nguyen Q: Shear Rheology of Silica Nanoparticle Dispersions, Appl. Rheol. 21 (2011) 13146.

This paper evaluates the use of lightweight aggregates (LWA), namely perlite (PER) and vermiculite (VER) in cement mortars. The workability of mortars was defined in rheometer and flow table tests. Three distinct LWA levels were added (0 - 3, 4.5 - 7, and 9 - 10.5 wt%) requiring the use of distinct water/solids (W/S) ratios (0.18, 0.265 and 0.35, respectively). In order to evaluate the performance of such formulations in the hardened state, the flexural and compressive strength after 28 days curing was also measured. In general, LWA caused a high variation on the yield stress and spread on table, being the yield stress the best rheological parameter to be related with the flow table. PER exerts a strong impact on initial yield stress, while the effect of VER is stronger for longer rheology testing periods. The compressive strength ranged from 12.3 MPa (0 % LWA) to 2.77 MPa (PER) and 2.39 MPa (VER).

Cite this publication as follows:
Senff L, Hotza D, Labrincha JA: Effect of lightweight aggregates addition on the rheological properties and the hardened state of mortars, Appl. Rheol. 21 (2011) 13668.

This paper presents an experimental study of the rheological behaviour of water-in-oil mixtures without any additive, up to 10 % of mass water concentration, where the mixture is considered to be a Newtonian fluid. The selected oil is a classical turbine mineral oil. Viscosity was measured for five temperatures, ranging from 10 to 80 C, for droplet size below 30 $\mu$m. A light decrease of viscosity was detected for water concentrations below 0.1 %. For concentrations greater than 0.2 %, viscosity increases with water concentration. Moreover, the variation of viscosity with temperature shows good correlation with both Walther model and Mac Coull & Walther model. Finally, a new model of water-in-oil mixtures viscosity as a function of temperature and concentration was defined.

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Harika E, Jarny S, Monnet P, Bouyer J, Fillon M: Effect of water pollution on rheological properties of lubricating oil, Appl. Rheol. 21 (2011) 12613.

The effect of shear viscosity on taste and mouthfeel perception has been extensively studied; however, the effect of extensional viscosity on sensory perception has been mostly neglected. This may be important as in-mouth processing is complex and probably best described as a superposition of shear and extensional flow characteristics. Fluid mechanics researchers interested in separating elastic effects from viscous effects use Boger fluids and this approach was adopted here to investigate the effect of fluid elasticity on sensory perception. For the first time, two food grade Boger fluids based on glucose syrup and aqueous solutions of maltodextrin as solvents and xanthan gum as high molecular weight polymer were formulated. The elasticity of the Boger fluids was characterised in rotational shear rheometry, in a filament break-up device and in microcontraction flow. Saltiness perception and mouthfeel of the Boger fluids and samples corresponding to the respective solvent were analysed. Surprisingly, there were no significant differences. Hypotheses attributing this finding to the intrinsic properties of the samples are discussed. A major study would be required to gain in-depth understanding of the sensory properties of these fluids as their flow properties are very different from typical liquid foods.

Cite this publication as follows:
Koliandris A, Rondeau E, Hewson L, Hort J, Taylor AJ, Cooper-White JJ, Wolf B: Food grade Boger fluids for sensory studies, Appl. Rheol. 21 (2011) 13777.

Blood rheology and hemodynamics models show positive correlation between hematocrit and hemodynamic factors that has implication to physiological and arterial disease processes. Blood flow is modeled by the Navier-Stokes equation and its non-Newtonian property by the Casson equation. Hematocrit dependent parameters in the Casson equation integrate the hematocrit level in the mathematical model. Then the mathematical model was linearized on a tetrahedral computational grid using the finite volume method. Results show strong correlation between hematocrit and hemodynamic factors. The determined hemodynamic factors and their strong correlation with the hematocrit provide explanation how these factors promote the atherosclerotic process in the right coronary artery at a steady flow and how influence arterial disease process.

Cite this publication as follows:
Shibeshi SS, Collins WE: Correlation of Hemorheology Parameter Hematocrit with Hemodynamic Factors and Arterial Diseases, Appl. Rheol. 20 (2010) 64092.

The application of sustainability principles in construction encourages the development of new products,with new functionalities and applications, able to improve buildings environmental performance. The use of latent heat storage materials in lime mortars aims to reduce the energy consumption of buildings.This work intends to evaluate the impact of phase change materials (PCM) incorporation in rheological and hardened state properties of aerial lime mortars. A fresh state characterization was conducted through the rheological study complemented with flow table tests of different mortar formulations. To complete the mortar characterization some hardened state properties (porosity, mechanical strength and microstructure) after 28 days, were also evaluated. It was concluded that, the PCM microcapsules incorporation does not compromise aerial lime mortars overall performance and may help to improve some characteristics like workability and mechanical strength. Therefore, it is possible to reduce the energy demand in old buildings, improving their performance and sustainability.

Cite this publication as follows:
Lucas S, Senff L, Ferreira V, BarrosodeAguiar J, Labrincha J: Fresh state characterization of lime mortars for latent heat storage, Appl. Rheol. 20 (2010) 63162.

Bitumen is undoubtedly the most important material in the construction and rehabilitation of flexible road pavements. By increasing the temperature, bitumen changes from brittle solid, to viscoelastic solid and finally to Newtonian fluid. The rheological characteristics of bitumen also vary greatly due to aging,which is a phenomenon initiated in the phases of production and application of bituminous (asphalt) mixtures and continued during the life of road pavements. The aim of this work is to study several rheological parameters in order to evaluate if they are able to quantify the aging of various types of bitumens. Four bitumens from the same distillation column in the refinery, but with different penetration grades, were aged by using the RTFOT method, which simulates the aging of the bitumen during the asphalt mixture production and pavement construction. The original (base) and aged bitumens were characterized with conventional tests used in the paving industry, and the results were compared with the rheological characteristics obtained with small amplitude oscillatory shear tests. Aging was assessed at high temperatures (110 to 180oC) through the activation energy computed from the temperature dependence of the Newtonian viscosity. However, the comparison of the characteristic relaxation times extracted from master curves measured at medium/low temperatures (between 25 to 80oC), proved to be the most sensitive indicator of bitumen aging.

Cite this publication as follows:
Peralta J, Hilliou L, Silva H, Machado A, Pais J, Oliveira J: Rheological Quantification of Bitumen Aging: Definition of a New Sensitive Parameter, Appl. Rheol. 20 (2010) 63293.

An experimental set-up was used to visually observe the characteristics of bubbles as they moved up a column holding xanthan gum crystal suspensions. The bubble rise characteristics in xanthan gum solutions with crystal suspension are presented in this paper.The suspensions were made by using different concentrations of xanthan gum solutions with 0.23 mm mean diameter polystyrene crystal particles. The influence of the dimensionless quantities; namely the Reynolds number, Re, the Weber number, We, and the drag co-efficient, cd, are identified for the determination of the bubble rise velocity. The effect of these dimensionless groups together with the Eotvos number, Eo, the Froude number, Fr, and the bubble deformation parameter, D, on the bubble rise velocity and bubble trajectory are analysed. The experimental results show that the average bubble velocity increases with the increase in bubble volume for xanthan gum crystal suspensions. At high We, Eo and Re, bubbles are spherical-capped and their velocities are found to be very high. At low We and Eo, the surface tension force is significant compared to the inertia force. The viscous forces were shown to have no substantial effect on the bubble rise velocity for 45 < Re < 299. The results show that the drag co-efficient decreases with the increase in bubble velocity and Re. The trajectory analysis showed that small bubbles followed a zigzag motion while larger bubbles followed a spiral motion. The smaller bubbles experienced less horizontal motion in crystal suspended xanthan gum solutions while larger bubbles exhibited a greater degree of spiral motion than those seen in the previous studies on the bubble rise in xanthan gum solutions without crystal.

Cite this publication as follows:
Hassan N, Khan M, Rasul M, Rackemann D: Bubble Rise Velocity and Trajectory in Xanthan Gum Crystal Suspension, Appl. Rheol. 20 (2010) 65102.

The classification of a concrete mixture as self-compacting (SCC) is performed by a series of empirical characterization tests that have been designed to assess not only the flowability of the mixture but also its segregation resistance and filling ability. The objective of the present work is to correlate the rheological parameters of SCC matrix, yield stress and plastic viscosity, to slump flow measurements. The focus of the slump flow test investigation was centered on the fully yielded flow regime and an empirical model relating the yield stress to material and flow parameters is proposed. Our experimental data revealed that the time for a spread of 500 mm which is used in engineering practice as reference for measurement parameters, is an arbitrary choice. Our findings indicate that the non-dimensional final spread is linearly related to the non-dimensional yield-stress. Finally,there are strong indications that the non-dimensional viscosity of the mixture is associated with the non-dimensional final spread as well as the stopping time of the slump flow; this experimental data set suggests an exponential decay of the final spread and stopping time with viscosity.

Cite this publication as follows:
Neophytou M, Pourgouri S, Kanellopoulos A, Petrou M, Ioannou I, Georgiou GC, Alexandrou A: Determination of the rheological parameters of self-compacting concrete matrix using slump flow test, Appl. Rheol. 20 (2010) 62402.

Strain rate frequency superposition (SRFS) has been suggested as new method to extend the frequency range for assessment of the complex storage modulus G* of soft glassy materials to lower frequencies. The basic idea is that relaxation processes in such fluids are accelerated by an external shear field, analogous to the effect of a temperature shift in polymer melts and solutions. Master curves for G' and G'' are constructed from the apparent modulus data determined from non-linear oscillatory shear experiments. Here we validate the SRFS principle for the first time by independent experiments and also demonstrate its limitations.We compare SRFS results to directly measured G', G'' at frequencies down to 10-3 rad/s and creep experiments lasting up to 104 s for a variety of gel-like fluids, including polymeric thickener solutions, a highly concentrated w/oemulsion, and wormlike micellar surfactant solutions, as well as a weakly viscoelastic non-Brownian suspension of glass beads. Good agreement between SRFS data and directly measured G', G'' values for the thickener solutions, the emulsion as well as the suspension. Apparent viscosity data obtained from creep experiments and absolute values of the complex viscosity in the low frequency limit agree fairly well for these fluids. But the method fails for the wormlike micellar solutions and this could be due to non-uniform flow or due to flow-induced structural changes. Finally,we demonstrate that the combination of SRFS, rotational rheometry, and advanced high frequency rheology methods allows for a broad bandwidth characterization of complex fluids spanning an unprecedented frequency range of about eleven decades.

Cite this publication as follows:
Kowalczyk A, Hochstein B, Stahle P, Willenbacher N: Characterization of complex fluids at very low frequency: experimental verification of the strain rate-frequency superposition (SRFS) method, Appl. Rheol. 20 (2010) 52340.

Results are presented aiming to determine whether wall slip occurs while performing rheological measurements of Carbopol solutions and bentonite dispersions at different concentrations using a standard oil-field Couette-type viscometer with two gap sizes. Yield stresses using a vane rheometer were also determined and compared to those obtained by extension of the experimentally-derived rheological curves at the Couette viscometer.The results show that, if preparation procedures are followed as suggested for Carbopol solutions and by API standard for drilling fluids, simulating either the pre-shearing in the rig mud pumps or in the bit nozzles during drilling operations, wall slip does not occur, with a good agreement of the rheograms and of the yield stresses determined for both gap sizes of the Couette viscometer and by the vane rheometer. No slip occurs also for CMC solutions which exhibited pseudoplastic power-law behavior.

Cite this publication as follows:
Kelessidis VC, Hatzistamou V, Maglione R: Wall slip phenomenon assessment of yield stress pseudoplastic fluids in Couette geometry, Appl. Rheol. 20 (2010) 52656.

This paper is concerned with the determination of the constitutive parameters of low concentrations of the complex fluid polyethylene glycol (PEO). Velocity fields of PEO solutions in a microfluidic T-junction have been measured for pressure driven flow using micron resolution particle image velocimetry. As the fluid is forced to turn the corner of the T-junction a range of shear rates, and therefore viscosities, is produced.Thus it is possible to establish the rheological profile from a single experiment. An inverse method used in conjunction with a finite element model was used to determine the constitutive parameters of the fluid, estimated to within 1.5 % error in all three cases considered.

Cite this publication as follows:
Bandulasena HC, Zimmerman WB, Rees JM: Rheometry of non-Newtonian polymer solution using microchannel pressure driven flow, Appl. Rheol. 20 (2010) 55608.

Aqueous solutions of F127 pluronic systems exhibit an interesting thermal gelation above a certain concentration. This phenomenon concerns the transition from a liquid-like behavior at low temperatures to a solid-like behavior at high temperatures, and it is due to different temperature responses from the different polymer segments, polypropylene oxide (PPO) and polyethylene oxide (PEO). Such property leads to a structural change in the self assembled macromolecule upon heating, from an isotropic micellar structure to an ordered cubic structure. These two types of assembly are clearly distinct with respect to their rheological behavior.This contribution emphasizes the rheological properties of the pluronic system in micellar and cubic phase, in combination with NMR, Dynamic Light Scattering and DSC information. The results emphasize the gelation process upon heating and a cubic phase characterized by higher storage modulus and higher A and z Weak Gel Model exponents than the micellar phase. Micellar growth upon heating was found within micellar phase. The presented data support the hypothesis that each polymer segment actively participates in the formation of the different phases: while PPO is responsible for micelle formation, PEO plays a dominating role in cubic phase formation. Finally, different stiffness between the core and the corona of the aggregates in the two phases is observed.

Cite this publication as follows:
Gentile L, DeLuca G, Antunes FE, OlivieroRossi C, Ranieri GA: Thermogelation Analysis Of F127-Water Mixtures By Physical Chemistry Techniques, Appl. Rheol. 20 (2010) 52081.

Electrorheological (ER) and dielectric properties of silicone-oil suspensions of polyaniline (PANI) particles protonated with phosphoric and tetrafluoroboric acids to various doping level have been investigated. The particle conductivity was thus varied between the order of 10-9 S/cm and 10-4 S/cm. The dynamic yield stresses obtained at controlled shear rate mode viscometry, the storage moduli from the oscillatory shear experiments and the dielectric relaxation times from frequency dependences of dielectric constant and loss factor were used as criteria of rigidity or elasticity of ER structures and particle mobility in the electric field. The conductivity of suspension particles plays a decisive role in their ER behaviour. The ER efficiency increased as conductivity of dispersed particles raised, irrespective of the type of employed acid used for the protonation of PANI.

Cite this publication as follows:
Stenicka M, Pavlinek V, Saha P, Blinova NV, Stejskal J, Quadrat O: Electrorheology of suspensions of variously protonated polyaniline particles under steady and oscillatory shear, Appl. Rheol. 20 (2010) 55371.

Thixotropy is an important rheological behavior of waxy crude oils. The objective of this paper is to demonstrate existing model's abilities to describe shear stress decay behaviors of waxy crude oils at constant shear rates. Seven models specially developed for or currently used to waxy crude oils are reviewed as well as two viscoelastic-thixotropic models for human blood. Stress decay behaviors were measured for four waxy crude oils and at various temperatures. Each of the models was used to fit the stress decay plots at a single shear rate, and at multiple shear rates, respectively. Globally, Zhao's model, a complex viscoplatic model with two structure parameters and twelve physical & fitting parameters,matched the experimental plots better than other compared models. While the three models with viscoelastic backgrounds were not quite successful. For use of models, one may make choice by comprehensively considering a model's complexity in mathematic form and abilities to describe the rheological behaviors.

Cite this publication as follows:
Zhang J, Guo L, Teng H: Evaluation of thixotropic models for waxy crude oils based on shear stress decay at constant shear rates, Appl. Rheol. 20 (2010) 53944.

Cite this publication as follows:
Ghirisan A, Broboana D, Balan C: 1st SRR - Summer School of Rheology 2010, Appl. Rheol. 20 (2010) 305.

An enhanced version of the flexure-based microgap rheometer (FMR) is described which enables rheological measurements in steady state shearing flows of bulk fluid samples of PDMS with an absolute gap separation between the shearing surfaces of 100 nm - 100 μmm. Alignment of the shearing surfaces to a parallelism better then 10-7 rad allows us to reliably measure shear stresses at shear rates up to 104 s-1. At low rates and for shearing gaps < 5 mm the stress response is dominated by sliding friction between the surfaces that is independent of the viscosity of the fluid and only determined by the residual particulate phase (dust particles) in the fluid.This behaviour is similar to the boundary lubrication regime in tribology.The absolute gap control of the FMR allows us to systematically investigate the flow behaviour at low degrees of confinement (gap separations 100 nm - 2 μm) that cannot be accessed with conventional (controlled normal load) tribological test protocols.

Cite this publication as follows:
Clasen C, Kavehpour HP, McKinley GH: Bridging Tribology and Microrheology of Thin Films, Appl. Rheol. 20 (2010) 45049.

We present a model for osmotic pressure and shear modulus of highly concentrated emulsions by including the interdroplet interaction in terms of disjoining pressure. The results show that even a small addition in interdroplet interaction can lead to significant deviations from the classical Princen-lacasse-Mason models that take into account only the surface energy as the sole source of elasticity. The newly proposed model predicts new effects, in particular the possibility of nonlinear dependency of elastic modulus on the droplet size, and can be used to discuss the elasticity sources of highly concentrated emulsions. In the second part of this article, the unusual elasticity of highly concentrated explosive emulsions is discussed by using the proposed model.

Cite this publication as follows:
Foudazi R, Masalova I, Malkin A: Effect of interdroplet interaction on elasticity of highly concentrated emulsions, Appl. Rheol. 20 (2010) 45096.

The yield stress of a magnetorheological fluid was measured as a function of magnetic flux density using different techniques. The yield stress values were determined by extrapolating the experimental shear stress-shear rate data to zero shear rate with the help of Bingham and Herschel-Bulkley models, and by using stress ramp and dynamic oscillatory tests.To obtain the rheological data, the rotational rheometer equipped with a magnetic field generator and a plate-and-plate measuring geometry was used. The different methods produced yield stress values which were in reasonable agreement with each other.

Cite this publication as follows:
Jonkkari I, Syrjala S: Evaluation of techniques for measuring the yield stress of a magnetorheological fluid, Appl. Rheol. 20 (2010) 45875.

Cite this publication as follows:
Grassi M, Lapasin R: 11th Conference of the Italian Society of Rheology, Appl. Rheol. 20 (2010) 177.

A new magnetocell, based on a plate-plate twin gap with housing and integrated online flux density measurement, allows for a reliable rheological characterization of magneto¬rheological fluids (MRF). Various modifications introduced into the commercial magnetocell version MRD180/1T (Physica/Anton Paar), distinctly improve the homogeneity of the magnetic flux density distribution and broaden the range of accessible shear rates in a MCR501 rheometer up to more than 3000 s-1. The new design has been licensed to the manufacturer, to provide a commercial twin gap magnetocell. Fixed volume dosing of MRF yields an improved reproducibility of flow curve measurements, as required for the design of technical devices like MR clutches and MR brakes. The twin gap magnetocell enables the mimicking of MRF response relevant for clutch and brake applications, like shear rate or shear stress step or ramp testing, and drive cycle testing.The dynamic shear stress response to changes of flux density and/or shear rate may be characterized. Testing of MRF is possible for brake applications under constant holding torque conditions in the pre-yield regime. MRF creep and recovery for various imposed shear stresses may be monitored as a function of time. Comparison with a concentric cylinder pilot clutch underlines the validity of the shear stress versus flux density characteristic as determined with the twin-gap magnetocell.

Cite this publication as follows:
Gabriel C, Kieburg C, Laun HM: Clutch and brake related testing of magnetorheological fluids using the BASF twin gap magnetocell, Appl. Rheol. 20 (2010) 41778.

This article reports viscosity data on a series of colloidal dispersions collected as part of the International Nanofluid Property Benchmark Exercise (INPBE). Data are reported for seven different fluids that include dispersions of metal-oxide nanoparticles in water, and in synthetic oil. These fluids, which are also referred to as 'nanofluids,' are currently being researched for their potential to function as heat transfer fluids. In a recently published paper from the INPBE study, thermal conductivity data from more than 30 laboratories around the world were reported and analyzed. Here, we examine the influence of particle shape and concentration on the viscosity of these same nanofluids and compare data to predictions from classical theories on suspension rheology.

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Venerus DC, Buongiorno J, Christianson R, Townsend J, Bang I, Chen G, Chung S, Chyu M, Chen H, Ding Y, Dubois F, Dzido G, Funfschilling D, Galand Q, Gao J, Hong H, Horton M, Hu L-W, Iorio CS, Jarzebski AB, Jiang Y, Kabelac S, Kedzierski MA, Kim C, Kim J-H, Kim S, McKrell T, Ni R, Philip J, Prabhat N, Song P, VanVaerenbergh S, Wen D, Witharana S, Zhao X-Z, Zhou S-Q: Viscosity measurements on colloidal dispersions (nanofluids) for heat transfer applications, Appl. Rheol. 20 (2010) 44582.

The semi-hyperbolic (SHPB) die with and possibly without wall lubrication has been proposed as a device for measuring the elongational viscosity of polymeric fluids. Using numerical simulation under the condition of complete wall slip, it was found for two polyethylenes (LDPE and LLDPE) that the calculated elongational viscosity values agreed well with strain-averaged values, < ηe >, obtained from independent measurements in stretching type rheometers. This is in agreement with the original hypothesis of Everage and Ballman (E-B). Numerical simulations showed that the Baird and Huang (B-H) approach for calculating < ηe >, which accounts for the shear stress due to geometric considerations in the presence of complete slip, agreed with data better than did the E-B approach. Numerical simulations using varying degrees of wall slip indicated that reasonable values of < ηe > could be obtained using the B-H approach with wall slip levels which could be most likely reached using a coating such as a flouroelastomer. The numerical simulations provided an explanation as to why the elongational viscosity values determined in the SHPB die for resins such as LDPE, which are extensional-strain hardening, are less sensitive to wall slip than non-strain-hardening resins such as LLDPE.

Cite this publication as follows:
Baird DG, Chan TW, McGrady C, Mazahir SM: Evaluation of the use of a semi-hyperbolic die for measuring elongational viscosity of polymer melts, Appl. Rheol. 20 (2010) 34900.

The present article describes and analyzes different calibration methods for a screw type process rheometer, Searle type, having a die hole at the downstream of a barrel. The work also quantifies the effect of time dependent flows due to the screw on the measurement performance. Time variations in torque and pressure become more notorious at increased resistances to flow (higher fluid viscosities and smaller die diameters). Screw speeds seem to do not affect these variations. Shear stress in the system is related to pressure and torque, and by using any of them, is possible to predict an average viscosity. Similar prediction errors were found when using torque or pressure. A section of practical applications is added to understand the use of a screw type process rheometer better.

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Salas-Bringas C, Lekang OI, Schuller RB: Time variations and calibration of a screw type process rheometer, Appl. Rheol. 20 (2010) 34526.

A rheological characterization and extrusion of aqueous suspensions of natural zeolites were carried out in this work. Preparation of suspensions followed similar routes to those used for the colloidal processing of ceramic powders.The suspensions were prepared at different volume fractions (v/v%) ranging from 5 to 61 v/v% for a pH value of 7. The suspensions showed a Newtonian behavior for solid contents up to 20 v/v% and shear thinning at higher solid loads. For solid contents above 35 v/v%, the suspensions exhibited hysteresis and a yield stress that growth exponentially with the solid load. The appearance of a yield stress and its fast growing at relatively low solid concentration, as compared to other type of ceramic suspensions, is attributed to several factors as inter-particle interactions, the presence of relatively large particles and to the influence of their irregular morphology. Also, a breaking stress was measured for solid contents above 35 v/v%, which characterizes a failure of the structure of the suspensions after yielding. This breaking stress determines the onset of slip flow of the suspensions, which is interpreted in this work as a signal of good extrusion characteristics. Finally, inexpensive and free of surface defects tubes were obtained from natural zeolites.

Cite this publication as follows:
Zacahua-Tlacuatl G, Perez-Gonzalez J, Castro-Arellano JJ, Balmorii Ramirez: Rheological characterization and extrusion of suspensions of natural zeolites, Appl. Rheol. 20 (2010) 34037.

We propose an exhaustive experimental characterization of a series of poly(n-butyl acrylate) samples that were synthesized by controlled radical polymerization and have different molecular weights. We focus on the rheological behavior of these polymers and propose a model of their rheological behavior using a molecular model based on the reptation concept.We report the principal rheological parameters for these homopolymers and demonstrate good agreement between model predictions and experimental data.

Cite this publication as follows:
Jullian N, Leonardi F, Grassl B, Peyrelasse J, Derail C: Rheological characterization and molecular modeling of poly(n-butyl acrylate), Appl. Rheol. 20 (2010) 33685.

Two types of starch gels made with various starch/water concentrations were studied in terms of their mechanical behaviour. Indentation tests were performed which revealed a rate independent load-deflection response. An inverse analysis based on the Marquardt-Levenberg optimisation algorithm and Finite Element Analysis was used to derive the stress-strain behaviour from the indentation data. The inverse predictions for the stress-strain curves are in good agreement with the direct measurements from uniaxial compression and shear tests up to high values of strain. The validity of the method was proven for both self-supporting and non self-supporting gels, with initial moduli ranging from a very small 60 Pa to 55 kPa. Thus the indentation characterisation method is proven as a powerful, fast and efficient way of evaluating and/or monitoring the behaviour of gels.

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Gamonpilas C, Charalambides M, Williams J, Dooling P, Gibbon S: On the characterization of the mechanical behaviour of starch gels using indentation techniques, Appl. Rheol. 20 (2010) 33283.

There have been many publications on the measurement and use of yield stress as a means of determining the ability of a system to suspend. Although in theory it is a useful predictive tool, in reality, it will often be found to give erroneous results, particularly when attempting to draw comparisons between dissimilar systems. Alternative techniques can be used which, whilst not being perfect, will give results which are closer to the reality. Several of these methods are evaluated and compared.

Cite this publication as follows:
Reeve P: Yield Stress: a predictive tool for determining suspending properties?, Appl. Rheol. 20 (2010) 33009.

Fumed silica suspensions in low molecular weight liquids are used in many photonic and microelectronic applications, playing its rheology a major role in the effectiveness of their usage. Particle-particle and particle-liquid medium interactions of suspensions of hydrophilic fumed silica in low molecular weight polar media, polypropylene glycol of 400 and 750 g/mol, concretely, have been already investigated.There, the affinity between polar solvent molecules and fumed silica particles prevents the formation of a 3D gel network. In this work it has been found that fumed silica can develop a flocculated suspension when it is dispersed in polypropylene glycol with a molecular weight of 2000 g/mol. Besides, it has been found that this suspension exhibits time dependent behaviour within its reversible shear thinning region, which is related to thixoelasticity. The experimental method, proposed theoretically by Cheng in 1986 to obtain the dynamic yield stress in thixotropic systems has been here extended successfully to a thixoelastic system.

Cite this publication as follows:
Galindo-Rosales FJ, Rubio-Hernandez FJ: Static and Dynamic Yield Stresses of Aerosil(R) 200 suspension in Polypropylene Glycol, Appl. Rheol. 20 (2010) 22787.

Surface rheological properties affect the dynamics of vesicles, nanoparticles, emulsion droplets, foam bubbles, polymer microcapsules, liquid jets, living cells, lung avioli, thin liquid films, and many other multiphase systems. Surface rheology is therefore relevant for a wide range of disciplines in the areas of physics, chemistry, engineering, biology, and medicine. Currently used descriptions of surface rheology have a number of limitations, and in particular are hard to generalize to the large deformation regime. Data are often analyzed with constitutive equations based on straightforward generalizations of models developed for describing bulk phase rheology. Since the latter are in general designed to describe incompressible materials, they are not guaranteed to describe highly compressible interfaces correctly. Here we discuss a unified approach to surface rheology based on nonequilibrium thermodynamics (NET) that provides a consistent set of balance and constitutive equations for the unambiguous determination of surface rheological parameters, both near and far beyond equilibrium. A closer integration of experimental surface rheology and multiphase nonequilibrium thermodynamics would clearly be beneficial for both disciplines.

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Sagis L: Rheology of complex fluid-fluid interfaces: a unified approach based on nonequilibrium thermodynamics, Appl. Rheol. 20 (2010) 24380.

We propose a viscosity model accounting for experiments of emulsions of two immiscible liquids at arbitrary volume fractions. The model is based on a recursive-differential method formulated in terms of the appropriate scaling variable which emerges from an analysis of excluded volume effects in the system. This variable, called the effective filling fraction, incorporates the geometrical information of the system which determines the maximum packing and reduces to the bare filling fraction for infinitely diluted emulsions. The agreement of our model for the viscosity with experiments and previous theories is good for all the range of volume fractions and viscosity ratios.

Cite this publication as follows:
Mendoza CI, Santamaria-Holek I: Rheology of concentrated emulsions of spherical droplets, Appl. Rheol. 20 (2010) 23493.

A new pressure cell is described to measure the flow behaviour of polymer melts in dependence of temperature and pressure. Special attention is laid on the construction and functionality of the pressure cell. The pressure cell can be pressurized up to 120 bar and is heatable up to 260 C. As a measuring geometry a plate-plate-system is used which is capable of characterising high viscous fluids. First results with high viscous silicone oil show good agreement with known references in literature.

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Krebs M, Wunsch O: Development and testing of a new pressure cell for rheological characterisation of polymer melts, Appl. Rheol. 20 (2010) 23229.

This paper reports on the result of rheological modelling of plaster deposition for paintings restoration. A typical plaster recipe was changed in order to check the effect of water level on rheological properties, both performing oscillatory tests and measuring plaster viscosity at two different temperatures. A model based on momentum balance on a vessel-nozzle geometry for a shear thinning fluid was set-up to simulate the deposition process and numerical results were compared to experimental data. A good agreement was found for moderate deposition times. At high process time, due to phase-separation in plaster, a loss in matching between the simulation and experimental point was found, because the modelling assumption of 'pseudo-homogeneous' behaviour does not apply anymore. Simulations allowed operating charts to be prepared reporting the deposited plaster volume as a function of the main process variables (temperature and pressure) and rheological properties of the plaster. This model could effectively support the development of an automatic deposition system able to recognise the filling volume over the painting surface and to control autonomously feeding of the plaster from a vessel through the deposition nozzle

Cite this publication as follows:
Baldino N, Seta L, Migliori M, Gabriele D, deCindio B, Chdichimo G: Rheological modelling of plaster deposition for painting restoration, Appl. Rheol. 20 (2010) 23110.

In this work,we consider model fluids which are dispersions of clay particles in aqueous solutions of carboxymethyl cellulose. Their rheological properties are measured in both steady and oscillatory shear flows.We present the experimental results obtained for different polymer concentrations and for three different molecular weights of the polymer. The clay is a bentonite sample and the particle concentration is fixed to a value of 5 %. The mechanical properties of these materials is the result of a competition between different mechanisms: association-dissociation of aggregates of particles, adsorption of polymer on the particles and desorption of solvent molecules from the particles, bridging of the particles by long polymer chains.

Cite this publication as follows:
BenAzouz K, Dupuis D, Bekkour K: Rheological characterizations of dispersions of clay particles , Appl. Rheol. 20 (2010) 13041.

A review of rheological in situ measurement techniques applied to liquids and soft solids at high pressures of more than 100 MPa is presented.The instruments reported in the literature fall into four groups: concentric cylinder rheometers, falling body and rolling ball viscometers, capillary viscometers and oscillatory systems. The measurement techniques are classified with respect to the possibility of carrying out an absolute measurement. Some typical experimental problems and error sources connected with high-pressure conditions are outlined and briefly discussed. The majority of the measurement techniques described in the literature are designed for the determination of the dynamic shear viscosity or viscosity function and only a few contributions report on the development of devices for the determination of other rheological parameters, e.g. normal stress differences or viscoelastic moduli.

Cite this publication as follows:
Kulisiewicz L, Delgado A: High-pressure rheological measurement methods: A review, Appl. Rheol. 20 (2010) 13018.

The effect of classical compatibilizers and silica fillers, which are a new potential type of compatibilizers, on the rheological properties of PP/LCP blends was investigated.The frequency sweep, shear stress growth and stress relaxation upon cessation of steady shear were performed to probe the effect of the interfacial modification and the role of silica, on the rheological behaviour of the blend. It was found that SEBS-g-MA improves the interfacial interaction more than SEBS due to the possible chemical bonding between maleic anhydride groups and LCP chains. The results showed while the hydrophilic silica fills both matrix and the LCP dispersed phases, the hydrophobic silica has some compatibilizing effect on PP/LCP blend samples.

Cite this publication as follows:
Foudazi R, Nazockdast H: Rheology of Polypropylene/Liquid Crystalline Polymer Blends: Effect of Compatibilizer and Silica, Appl. Rheol. 20 (2010) 12218.

The present work deals with the study of the rheological behaviour of PVC (polyvinylchloride) pastes containing particles of ~ 150 μm in diameter obtained by polymerization in suspension.The rheological properties of the PVC pastes were characterized by creep experiments using 6-bladed vane geometry. The pastes show a very small compliance and a very narrow linear domain. The effects of temperature, of interstitial liquid and of saturation level of the wet paste were studied in detail and it was found that they significantly modify the creep behaviour. Other techniques allowed us to characterise rearrangements of the particles under load, in compression, by their oedometric modulus and by the failure stresses measured using a shear box. A very high oedometric modulus was measured (20 MPa) and by application of the Mohr-Coulomb criterion the internal friction coefficient (μ ~ 0.6) and the cohesion of the materials were deduced.We conclude from this investigation that the interfacial properties of the grains play a major role in the behaviour of the wet pastes under shear or in compression. The paper illustrates the difficulties in measuring the rheological and the structural properties of jammed systems made from non-ideal (real) particles and reveals the key parameters in studying such media.

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Rabia A, Djabourov M, Feuillebois F, Lasuye T: Rheology of wet pastes of PVC particles, Appl. Rheol. 20 (2010) 11961.

The rheological behavior of ceramic oxide hydroxide alumina pastes with high solid loading is investigated. In order to enable an adequate and experimentally rheological characterization, the measurements are carried out with a Rheostress viscometer under isothermal conditions. Various compositions of a commercial AlOOH powder and binder mixture are investigated. We discuss the variation of loss modulus G', storage modulus G'', apparent and complex viscosities h, h* as function of frequency and shear rate.The solid phase used here is the boehmite; the most important precursor for the g-Al2O3 phase for several applications such as catalysts or functional layers of ceramics. Solid phase compositions used are justified by the applications of boehmite in the manufacturing of catalytic materials. A transition zone that appears at a concentration of 55 %wt of the solid phase (Pural) and at which the rheological behavior changes from viscoelastic to elastic is observed. This transition is of a importance as far as ceramic manufacturing is concerned.

Cite this publication as follows:
Belkham NeH, Mehamha A, Benachour D: Rheological behavior of alumina ceramic pastes, Appl. Rheol. 19 (2009) 64969.

The viscoelastic performance indicators of a commercial roofing membrane and an ecological bituminous membrane, which contains EVA copolymer from disused greenhouses and filler from landfill, are investigated. Rheological methods reveal as a useful tool to investigate basic and technical aspects of these materials. It is shown that using an extrusion rheometer adapted to measure the flexibility at low temperatures and measuring the tackiness by means of a plate-plate rheometer, constitute basic experiments that help to develop new membranes. Under these premises, it is demonstrated that the ecological membrane is a performing material, whose sole shortcoming is a slightly higher application temperature.

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Goikoetxeaundia G, Fernandez M, Munoz ME, Santamaria A: Rheology applied to investigate roofing membranes: The case of an ecological alternative, Appl. Rheol. 19 (2009) 62305.

The rheological behavior of emulsions has been extensively investigated through experiments made at atmospheric pressure. This study presents a new experimental characterization of these fluids with measurements performed under pressure and in a large range of temperature.The results show that viscosities obey Barus model that predicts an exponential increase with pressure. The extent of the increase is governed by a unique piezoviscous coefficient. This coefficient exhibits a non monotonous variation with temperature. It has been shown that its thermal dependence and its value can be related to the viscoelastic properties of the fluid. The coefficient is an increasing function of temperature for a solid-like behaviour and a decreasing function of temperature for a liquid-like behaviour.This approach has been applied to heavy crude oils. It has been demonstrated that water droplets and oil composition modify the elastic character of heavy crude oils and as a consequence they modify their piezoviscosity.

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Chaudemanche C, Henaut I, Argillier J: Combined effect of pressure and temperature on rheological properties of water-in-crude oil emulsions, Appl. Rheol. 19 (2009) 62210.

Experimental and numerical studies have been undertaken to check the influence of a magnetic field on the viscosity of liquid GaInSn with suspended solid particles.The rheological investigations show a significant change of the slope of the measured flow curves between the situation B = 0 and 0.02 T. By means of numerical simulations of the flow in the presence of Lorentz forces it could be shown that the influence of magnetohydrodynamic damping of the flow reduces the measured changes but does not annihilate them. As conclusion a 15 % change of viscosity of the melt in a magnetic field with B = 0.02 T could be fixed.

Cite this publication as follows:
Borin D, Nikrityuk P, Odenbach S: On the magnetic field influence on the viscosity of liquid GaInSn with suspended solid particles, Appl. Rheol. 19 (2009) 61995.

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Reinhart WH: 15th Conference of the European Society of Clinical Hemorheology and Microcirculation (ESCHM 2009), Appl. Rheol. 19 (2009) 312.

"Single-point" equations used for intrinsic viscosity determination are greatly used when working with synthetic polymer solution systems. In this work we have applied them to a biological macromolecule in a bovine serum albumin (BSA)/water system. Almost all single-point equations are available and errors can be lowered. However, we have detected a systematic bias in the estimations provided by "single-point" methods. To overcome it we propose a "double-point" method which gives lower estimation errors for this system. This novel method is not system specific and could be applied to other polymeric solution.

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Curvale R, Cesco C: Intrinsic viscosity determination by 'single-point' and 'double-point' equations, Appl. Rheol. 19 (2009) 53347.

The stability of the flow induced by the extrusion forming process of a cement based material is largely influenced by the relative migration between the lubricating liquid phase and the granular skeleton. In the present work,we propose linking rheological concepts and soil mechanics (consolidation theory, Darcy's law) to reach a simple criterion which predicts the extrusion ability of a mortar. Extrusion tests on studied mortar are performed at different ram velocities for criterion validation.

Cite this publication as follows:
Perrot A, Rangeard D, Melinge Y, Estelle P, Lanos C: Extrusion criterion for firm cement-based materials, Appl. Rheol. 19 (2009) 53042.

Rheological characterisation of mortar is complicated by phenomena of slip, the formation of shear bands and depletion. At relatively low solid fractions a typical Couette geometry and a medium-size mixer-type rheometer were used to determine flow curves. At higher solid fractions a large-size coaxial cylinder rheometer with multiple blade vane geometry was used up to the point where slippage occurred. The viscosity as a function of concentration responds to the Krieger-Dougherty law, when a mortar is considered as a suspension of sand in a matrix of binder slurry. The limits of this description corresponds to a critical solid fraction above which air is entrapped during the mixing procedure: air content measurements demonstrate this phenomenon. A clear relationship between mortar and slurries was established, based on the measured properties of both binder and sand particles, and on the Farris model for polydisperse suspensions. Intrinsic viscosity can be used as a tool to evaluate shape characteristics of the binder particles. A procedure for mixture optimisation of mortars using this model is demonstrated for the case of a trimodal mortar.

Cite this publication as follows:
Hendrickx R, Rezeau M, VanBalen K, VanGemert D: Mortar and paste rheology: concentration, polydispersity and air entrapment at high solid fraction, Appl. Rheol. 19 (2009) 52550.

Adhesive properties of fresh mortar joints containing different dosage rates of a water-soluble polymer (cellulose ether based) are investigated using the probe tack test. This test consists of measuring the evolution of the normal force required to separate at a given velocity two plates between which a thin layer of the sample is sandwiched. Three different adhesive components are inferred from the measured stretching force: cohesion, adhesion and adherence. The influence of the polymer dosage rate and the pulling velocity on the evolution of these adhesive properties is investigated. The adhesive components are then related the rheological properties of the mortars which are shown to behave as Herschel-Bulkley shear-thinning fluids.

Cite this publication as follows:
Kaci A, Bouras R, Chaouche M, Andreani P, Brossas H: Adhesive and Rheological Properties of Mortar Joints, Appl. Rheol. 19 (2009) 51970.

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Ahzi S, Patlazhan S, Remond Y, Khaleel M: Third International Conference on Polymer Behavior (Marrakech, Marocco, 2008), Appl. Rheol. 19 (2009) 247.

Aggregation, heterogeneous flows, and complex particle geometries all pose challenges in rheology. This paper uses squeeze flow rheometry techniques to examine a case, where all of these played a role. The applicability of some squeeze theories is tested, and the ability to predict results based on suspension theories is examined. The squeeze flow data is shown to deviate from Stefan's law [Stefan J, Sitz. Kais. Akad. Wiss. Math. Nat. Wien 69 (1874) 713-735]. The suspension rheology deviated from predicted theory, but by taking into account particle effects such as aggregation the fit to the empirical Maron-Pierce equation [Maron SH and PE Pierce, J. Coll. Sci. 11 (1956) 80-95] could be understood. The conclusions of this study show how using only squeeze flow techniques the synergistic nature of these effects can be better understood.

Cite this publication as follows:
McIntyre EC, Filisko FE: Squeeze Flow Rheology of Zeolite Suspensions, Appl. Rheol. 19 (2009) 44322.

The flow of non-Newtonian technical fibre suspensions (paper pulps) through a number of contractions is analysed and compared. Traditionally technical fibre flows are modelled as flow of fibres in a suspending medium. Here they are treated as crowded flows of fibre flocs from which the liquid may be squeezed in and out from. Compressive flows are common in the fibre-based process industry. They can e.g. be found in the headbox of a paper machine, in extruder nozzles in polymer technology, in the stirrer zone of mixers, etc. Traditionally such flows are analysed in elongational flow terms. Here it will be demonstrated that elongational and compressive flows for technical fibres suspensions differ qualitatively. The nature of technical fibre flocs is also discussed. For historic reasons they have come to be regarded as the outcome of a flocculation process of electrostatic-colloidal and/or mechanical-entanglement type. It will be shown that such a process is unnecessary for technical fibre suspensions and that these flocs are qualitatively different, viz. frozen-developed dissipative structures of the flocky fibre flow from which they originate. It will also be demonstrated that technical fibre flocs, in contrast with flocs of the chemically flocked type, are basically non-coherent, i.e. not kept together by themselves. It is this non-coherence that makes a compressive approach fruitful, for these economically important flows. An attempt to explain the reasons behind the present state of fibre flow theory is presented. The ambition is to stop to the present inproductive tradition in technical fibre flow.

Cite this publication as follows:
Bjorkman U: The non-Newtonian Fluid Mechanics of Technical Fibre Suspensions: Compressive Flows, Appl. Rheol. 19 (2009) 44290.

The combined effect of charged addition and molecular weight, Mw, on the thermal gelation and gel dissolution of poly(Nisopropylacrylamide) chains was explored by using Rheological techniques. The synthesized charged derivative is poly(N-isopropylacrylamide co-Acrylic acid). The rheological behavior of the two macromolecules is clearly different: the thermal gelation of the high Mw and charged macromolecule is much more accentuated. This suggests that the gelation at high temperatures only occurs when the inter polymer aggregate distance is sufficiently short to allow polymer bridging; this situation can be achieved by different approaches, such as increasing polymer concentration and increasing polymer persistence length and polymer Mw.

Cite this publication as follows:
Antunes FE, Gentile L, Tavano L, OlivieroRossi C: Rheological characterization of the thermal gelation of poly(N-isopropylacrylamide) and poly(N-isopropylacrylamide)co-Acrylic Acid, Appl. Rheol. 19 (2009) 42064.

Filament breakup of high viscosity fluids with apparent yield stress has been investigated and strategies for an appropriate characterization of their behavior in CaBER experiments are discussed. Filament profiles of such fluids exhibit significant concave curvature. Accurate determination of filament shape is mandatory for understanding deformation behavior. Therefore, we have set up an optical train including high-speed camera, telecentric objective and telecentric back-light illumination with a blue light emitting diode (LED) providing high contrast filament shape imaging. Image analysis allows for diameter determination with an accuracy of 3.55 μm/pixel. In addition to the transient filament diameter at the neck we have extracted the curvature at this point as a function of time and the region of deformation, in order to characterize the extensional flow behavior.We have investigated the time evolution of filament shape as a function of various experimental parameters like stretching time, velocity profile during stretching, stretching ratio and initial sample volume at constant stretching ratio. Filament thinning is independent of stretching time, tsub>s and stretching velocity profile. But when the same stretching ratio is applied at different initial volume fraction, filament curvature increases strongly with decreasing sample volume leading to an increase of filament life time according to the negative contribution of its curvature to the laplace pressure inside the fluid.

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Niedzwiedz K, Arnolds O, Willenbacher N, Brummer R: Capillary Breakup Extensional Rheometry of Yield Stress Fluids, Appl. Rheol. 19 (2009) 41969.

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Wagner C: Rheologentagung 2009 Berlin, Appl. Rheol. 19 (2009) 179.

The basic rheological properties of two Persian wheat flours - Tajan (11 % protein) and Back Cross Roshan (8 % protein) and two Australian wheat flours-JANZ (12.9 % protein) and Rosella (8.6 % protein) have been characterized.These properties have been interpreted via a damage function model. All samples could be reasonably well described by the damage function model with a power-law relaxation spectrum. Although the shear stresses in the Australian samples were higher, the relaxation parameter G(1) and power-law exponent p for the Australian varieties were lower than those for the Persian samples and the damage functions were different. Since protein contents were different, this indicates that the amount of protein is not the sole determinant of softness in the samples. The damage function f was also calculated for all samples. This function gives a measure of the softening due to working or kneading of the samples at a given strain level.

Cite this publication as follows:
Amirkaveei S: A Comparison of the Rheology of four Wheat Flour Doughs via a Damage Function Model, Appl. Rheol. 19 (2009) 34305.

The objective of this work is to study quantitatively the errors introduced by the standard Newtonian and power-law assumptions used in the determination of the material properties of viscoplastic fluids from circular Couette experiments. The steady-state circular Couette flow of a Herschel-Bulkley fluid is solved assuming that the inner cylinder is rotating at constant speed while the outer one is fixed. Analytical solutions are presented for certain values of the power-law exponent. It is shown that the error in the computed wall shear rate, which is insignificant when the diameter ratio is closed to unity,may grow large depending on the diameter ratio and the material parameters.

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Chatzimina M, Georgiou G, Alexandrou A: Wall shear rates in circular Couette flow of a Herschel-Bulkley fluid, Appl. Rheol. 19 (2009) 34288.

Rheological creep and recovery tests have been applied at different assay times to xanthan gum hydrogels at several concentrations. The Burger model has been successfully applied to fit the creep data and to analyze results. Increasing the xanthan gum concentration also increases the elastic and viscous components without changing the molecular distribution of these hydrogels. A semi-empirical equation considering the different elements of the Burger model has been proposed to analyze compliance behavior in recovery tests. The dependence of the relative contribution to deformation of the Maxwell and Kelvin-Voigt units upon xanthan gum concentration and recovery assay times has been evaluated. Since the recovery ratio is the same for all hydrogels, we suggest parallel structures with no mutual interactions are formed when increasing concentration.

Cite this publication as follows:
Dolz M, Corrias F, Diez-Sales O, Casanovas A, Hernandez M: Influence of test times on creep and recovery behaviour of Xanthan gum hydrogels, Appl. Rheol. 19 (2009) 34201.

We present an experimental study of the stability of the Taylor-Dean flow of well characterized suspensions of solid disks occurring between two horizontal coaxial cylinders. The inner cylinder is rotating and the outer cylinder is at rest. By means of a visualization technique, we determine the shape of the vortices which take place in the flow at the onset of the instability and the corresponding critical parameters against the flake concentration and the system aspect ratio.

Cite this publication as follows:
Daimallah A, Bouabdallah A, Nsom B, Adnane M, Alemany A: Onset of Instabilities in Taylor-Dean Flow of Yield-Stress Fluid, Appl. Rheol. 19 (2009) 33960.

The specific properties of bentonite such as hydration, swelling,water absorption, viscosity, yield stress and thixotropy make it a valuable material in the form of mineral powder for a wide range of uses in agronomy, cosmetics and civil engineering. A flow curve is a quick test used to evaluate the rheological basic properties of a viscous fluid. However, many bentonite dispersions exhibit a complex flow curve, with yield stress and thixotropy area, especially at high concentration. In this study, flow curves from raw and activated bentonites dispersed in water were acquired at 6, 8 and 10% mass concentrations. Five stages along the flow curve were identified.To explain each stage, rheograms obtained from a dispersion made with a model material were studied in depth. The model material was a smectite extracted from a raw bentonite then saturated with calcium or sodium. Many homoionic and bi-ionic dispersions were prepared at various concentrations. The analysis and the modelling of some creep-recovery tests by a Zener model showed the relationship between the initial stage in the flow curve, named AB stage, and the viscoelastic properties of the fluid. The AB stage corresponds to the deformation of the material in the solid state. The τB point corresponds to an intermediate yield stress between the solid state and the start of the heterogeneous fracturation. The study of many bi-ionic dispersions allowed drawing the evolution of the yield stress as a function of concentration and saturation. The composition of the raw bentonites was expressed as an equivalent bi-ionic dispersion by calculating an active smectite percentage. A good correlation was obtained at the highest concentrations between τB from the bi-ionic model dispersions and the raw bentonites dispersions

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Paumier S, Pantet A, Monnet P, Touze-Foltz N: Evaluation of the viscoelastic properties of a clay material using a flow curve, Appl. Rheol. 19 (2009) 23824.

The authors previously introduced an activation model for the onset of shear thickening in electrically stabilized colloidal suspensions. It predicts that shear thickening occurs, when particles arranged along the compression axis in a sheared suspension do overcome the electrostatic repulsion at a critical shear stress, and are captured in the primary minimum of the DLVO interaction potential. A comparison with an experimental investigation on non-aqueous silica suspensions, carried out by Maranzano and Wagner, is performed. For particle systems that fall into the applicability range of the theory, a good coincidence between the experimental data and the model predictions can be found.

Cite this publication as follows:
Kaldasch J, Senge B, Laven J: Shear thickening in electrically stabilized non-aqueous colloidal suspensions, Appl. Rheol. 19 (2009) 23493.

Nanoclay dispersions in organic solvents are widely used in cosmetics for a variety of gels and creams, whose properties depend on the powder content and the processing method. The control of the shear applied during processing is therefore essential for achieving the required properties.This study demonstrates the utility of applying rheological measurements for characterizing cosmetic products based on nanoclays and relating their viscoelastic properties to end-use performances. In particular, a rheological characterization of bentonite dispersions in isododecane at different clay content and shear history is presented. For each inorganic content, both mixed samples and samples subjected to several calendering runs were studied. The effect of shear and clay content on the viscoelastic properties was investigated by a combination of oscillatory shear experiments under small-deformation conditions and by X-Ray diffraction. The tested samples showed a gel-like behaviour with a final structure depending on the applied shear stress. By increasing the inorganic content in the dispersion, a reduction in the gel stability to a further shear application was observed. Two models, developed for colloidal gels,were used to fit the rheological results enabling to evaluate the microstructure and the degree of dispersion of the tested samples and to relate the colloidal structure to the elastic properties.

Cite this publication as follows:
Lionetto F, Maffezzoli A: Rheological characterization of concentrarted nanoclay dispersions in an organic solvent, Appl. Rheol. 19 (2009) 23423.

An optimised method for the detection and analysis of the time dependent pressure associated with the development of melt flow instabilities during extrusion through a capillary die was developed and validated. The magnitude and frequency of the developed quasi-periodic distortions, as well as the pressure profiles along the die length, were found to depend on the MWD, topology, melt elasticity and uniaxial extensional flow properties. Both the onset and magnitude of strain hardening in uniaxial extension appear to be related to the onset for the development of melt flow instabilities under capillary flow. For a better understanding of the role of the extensional properties (namely that of a purely elastic instability) the Hencky strain to failure was also determined and correlated to the observed flow instabilities. Time resolution of the capillary rheometer was improved by a factor of 1000, pressure resolution by a factor of 100 compared to the original set-up.

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Filipe S, Becker A, Barroso VC, Wilhelm M: Evaluation of melt flow instabilities of high-density polyethylenes via an optimised method for detection and analysis of the pressure fluctuations in capillary rheometry, Appl. Rheol. 19 (2009) 23345.

Steady state and transient rheological behaviours of a one-coat render mortar are considered experimentally using a shear rheometer equipped with the vane geometry.The flow curves performed at controlled shear-rates exhibit highly pronounced minima, which is attributed to shear localization and strong thixotropy. This latter property is further investigated separately by considering the temporal growth of the apparent stress at very low shear-rate, reflecting the material's microstructure rebuild up following shearing at different high shear rates. It is found that rebuilding characteristic time is roughly independent upon shear history, indicating that this is a material parameter. The influence of water dosage rate on the rheological behaviour is considered. As expected, apparent viscosity and yield stress decrease with increasing kneading water amount. The rebuilding up kinetics is found to be non sensitive to water dosage rate, suggesting that the material's processability would be preserved when changing this parameter, although significant creeping may be expected at high water dosage rates.

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Kaci A, Chaouche M, Andreani P-A, Brossas H: Rheological behaviour of render mortars, Appl. Rheol. 19 (2009) 13794.

It is observed that, although consisting on very different formulations, the rheological properties of filled polyurethane adhesives may be rescaled onto simple master curves, and described with a small number of parameters: a yield stress, a low frequency elastic modulus and a characteristic time of flow. As a consequence, very simple and qualitative measurements of their deformations, such as the Dog Tail Test, may be used to deduce these parameters. By comparing the values obtained from Dog Tail Test measurements to well-controlled rheological measurements and to finite element computation, we show that such a simple and qualitative test may be used as a tool to measure both the yield stress and the elastic modulus of highly viscoelastic systems

Cite this publication as follows:
Lootens D, Jousset P, Dagallier C, Hebraud P, Flatt R: The ''Dog Tail Test'': a quick and dirty measure of yield stress. Application to polyurethane adhesives, Appl. Rheol. 19 (2009) 13726.

A systematic approach for collecting data from a torque rheometer is described, and the Bousmina et al. model is evaluated for HDPE, LDPE, LLDPE and HDPE/filler composites. The torque rheometer results are in good agreement to capillary and parallel plate viscometer measurements for neat polymers, when the torque values measured are corrected for the temperature rise due to viscous dissipation. For the composites, the torque and capillary results virtually coincide, but the viscosities are lower than those measured with the parallel plate instrument, in oscillatory mode, because the Cox-Merz rule is not valid. Although there are some limitations at high shear rates, due to viscous dissipation, the present work provides a proof and a methodology for the practical utility of torque rheometers for viscosity measurement in highly viscous systems.

Cite this publication as follows:
Santi CR, HageJr E, Correa CA, Vlachopoulos J: Torque Viscometry of Molten Polymers and Composites, Appl. Rheol. 19 (2009) 13148.

In the present study,we investigate the behaviour of the human blood in a stenosed blood vessel. The human blood is studied as a Newtonian as well as non-Newtonian fluid. We consider three rheological models of the shear-thinning non- Newtonian models and compare them with the Newtonian model. The blood flow through a stenosed blood vessel is studied numerically by solving the three dimensional Navier-Stokes equation along with the continuity equation and particular rheological model. Distribution of velocity, pressure,wall shear stresses and flow recirculation characteristics are determined for two time steps of the cardiac cycle. Present results indicate a significant influence of the shear-thinning viscous behaviour of a human blood on the most important hemodynamic parameters that play a key role in formation of atherosclerotic plaques. last but not least, a systematic grid refinement analysis as well as numerical accuracy study IS performed and present numerical results may be treated as the benchmark.

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Ternik P, Marn J: Numerical study of blood flow in stenotic artery, Appl. Rheol. 19 (2009) 13060.

This is a study of three-phase foam rheology to qualify penetration in to backing webs during frothed carpet compounds applications.Transient viscosity as a function of shear rate under a short time period is proposed to characterize flow of these compounds in response to a rapidly changing shear field during their application.We developed a fluid dynamic model that predicts the shear and pressure distributions in the compound during its processing in a metering nip based on process parameters and rheological results.We tested frothed compound formulations that are empirically known to be "penetrating" and "non-penetrating" based on the choice of soap (frothing surfactant). Formulated at the same froth density, penetrating to carpet backing compounds had large froth bubbles, relatively low transient shear viscosity and showed increasing foam breakdown due to shear when compared to non-penetrating compounds. Such frothed compounds readily collapse under shear and have relatively low dynamic stability, so the transition from a three-phased (air/aqueous/solid) to a twophased (water/solid) system occurs much easier and faster during application. The model predicts the shear rate development and a small difference in the pressure distributions in the applicator nip between these formulations, but reduction in drainage for the non-penetrating formulation.

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Triantafillopoulos N, Schreiner B, Vaughn J: Latex Carpet Compound Rheology, Appl. Rheol. 18 (2008) 64250.

Two approaches for determining the entrance pressure drop in capillary rheometry were compared with low-density polyethylene and polystyrene melts as test fluids. Direct measurements with the orifice die were found to yield higher values for the entrance pressure drop, and hence lower values for the wall shear stress, than the Bagley correction method. This was postulated to be caused by the sticking of the melt to the wall of the outlet region of the orifice die. The additional pressure drop created in the outlet region of the orifice die, when the flowing material fills it completely, was also evaluated by means of numerical flow simulation.

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Aho J, Syrjala S: Evaluation of different methods for determining the entrance pressure drop in capillary rheometry, Appl. Rheol. 18 (2008) 63258.

In practice, while placing concrete in a formwork by pumping, the pressure generated by the pump is not controlled. In order to enhance the safety on the worksite, and in view of the current economic and ecologic arguments, it would be useful to dispose of an equation able to predict pressure losses based on the rheological properties of the concrete and the pipe configuration. This paper describes the derivation of an extended version of the Poiseuille formula, for shear-thickening materials with a yields stress, described by the modified Bingham equation. This formula is applied to flow-tests with self-compacting concrete. The results prove the applicability of this extended Poiseuille formula, showing that the flow is occurring in laminar regime, with no significant wall slip.

Cite this publication as follows:
Feys D, Verhoeven R, DeSchutter G: Extension of the Poiseuille formula for shear-thickening materials and application to Self-Compacting Concrete, Appl. Rheol. 18 (2008) 62705.

The rheological behaviour of non-Newtonian, highly concentrated and non-transparent fluids used in industry have so far been analysed using commercially available instruments, such as conventional rotational rheometers and tube viscometers. When dealing with the prediction of non-Newtonian flows in pipes, pipe fittings and open channels, most of the models used are empirical in nature. The fact that the fluids or slurries that are used normally are opaque, effectively narrows down the variety of applicable in-line rheometers even further, as these instruments are normally based on laser or visible light techniques, such as laser Doppler Anemometry. In this research, an Ultrasonic Velocity Profiling technique (UVP), in combination with a pressure difference (PD) measurement, was tested to provide in-line measurement of rheological parameters. The main objective of this research was to evaluate the capabilities of the UVP-PD technique for rheological characterisation of different concentrations of non-transparent non-Newtonian slurries. Kaolin, bentonite, Carboxymethyl Cellulose (CMC) and water solutions were used as model non-Newtonian mining slurries. Results determined by the UVP-PD method were compared with results obtained by off-line rheometry and in-line tube viscometry. The agreement between the UVP-PD method, tube viscometry and conventional rheometry was found to be within 15 % for all of the highly concentrated mineral suspensions investigated over a given range of shear rates.This method, if used in combination with a pressure difference technique (PD), has been found to have a significant potential in the development process of new in-line rheometers for process control within the mining industry.

Cite this publication as follows:
Kotze R, Haldenwang R, Slatter P: Rheological characterisation of highly concentrated mineral suspensions using an Ultrasonic Velocity Profiling with combined Pressure Difference method, Appl. Rheol. 18 (2008) 62114.

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Bacchelli F, Pirini MF, Coppola S: The 10th Conference of the Italian Society of Rheology, Appl. Rheol. 18 (2008) 320.

Cite this publication as follows:
Fischer P, Nicolai T: Food Colloids 2008 - Creating Structure, Delivering Functionality, Appl. Rheol. 18 (2008) 315.

Investigations of rheological properties of ferrofluids have shown strong changes of the viscosity in magnetic fluids with an applied magnetic field. The change of the viscosity . the magnetoviscous effect . can theoretically be described with chain and structure formation under the influence of a magnetic field. Moreover, the formation of these structures leads to the appearance of viscoelastic effects or other non-Newtonian features like yield stress in ferrofluids with an applied magnetic field. With a shear rate controlled rheometer . as it as been used in former experiments . the yield stress could not be investigated directly. Therefore the results concerning a field dependent yield stress based on an extrapolation of shear controlled measurements. For the direct investigations of the yield stress, a dedicated stress controlled rheometer is required, allowing direct investigations of the magnitude and field dependence of this effect. In this work the design of the stress controlled rheometer with its main parameters has been described in detail. The rheological investigations with differently composed fluids show that the stress controlled rheometer enables direct measurements of even small yield stresses in ferrofluids as well as large effects like they are found in magnetorheological fluids (MRF).

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Shahnazian H, Odenbach S: New driving unit for the direct measurement of yield stress with a stress controlled rheometer, Appl. Rheol. 18 (2008) 54974.

Rheological properties of elastomeric nanocomposites with organically modified Montmorillonite clays, as possible replacements or supplements to classical active fillers, such as carbon black or silica, have been intensively studied in recent years. Possessing large specific surface areas acquired through the melt-mixing processes of elastomeric intercalation and subsequent filler exfoliation, the clay particles have indeed proved to be highly eligible reinforcing and thermally stabilizing ingredients for application in elastomers. In fact, their performance has shown to be in many respects superior to that of classical fillers, particularly owing to some unusual, though beneficial, exhibited properties. Namely, apart from uncommonly high surface activity, manifested by creation of a host of van der Waals type secondary linkages with elastomer molecules, the main curiosity of clay filler is its dissipative action. Using dynamic mechanical functions under different deformational and temperature conditions, as means for rheological characterization of nanocomposites, the foregoing nano-scale traits are clearly reflected in substantial stiffness at low strains and, unexpectedly, dwindling energy loss with increasig filler content and/or decreasing temperature. Besides, rheological analysis of this kind, together with appropriate theoretical grounds, has enabled elucidation of peculiar conduct, as well as macroscopic insight into the very nature of secondary interactions in elastomers.

Cite this publication as follows:
Susteric Z, Kos T: Rheological Idiosyncrasies of Elastomer/Clay Nanocomposites, Appl. Rheol. 18 (2008) 54894.

Complex fluids exhibit time-dependent changes in viscosity that have been ascribed to both thixotropy and aging. However, there is no consensus for which phenomenon is the origin of which changes. A novel thixotropic model is defined that incorporates aging. Conditions under which viscosity changes are due to thixotropy and aging are unambiguously defined. Viscosity changes in a complex fluid during a period of rest after destructuring exhibit a bifurcation at a critical volume fraction φC2. For volume fractions less than φC2 the viscosity remains finite in the limit t to infnity. For volume fractions above critical the viscosity grows without limit, so aging occurs at rest. At constant shear rate there is no bifurcation, whereas under constant shear stress the model predicts a new bifurcation in the viscosity at a critical stress σB, identical to the yield stress σy observed under steady conditions. The divergence of the viscosity for σ ≤ σB is best defined as aging. However, for σ > σB, where the viscosity remains finite, it seems preferable to use the concepts of restructuring and destructuring, rather than aging and rejuvenation. Nevertheless, when a stress σA (≤ σB) is applied during aging, slower aging is predicted and discussed as true rejuvenation. Plastic behaviour is predicted under steady conditions when σ > σB. The Herschel-Bulkley model fits the flow curve for stresses close to σB, whereas the Bingham model gives a better fit for σ >> σB. Finally, the model's predictions are shown to be consistent with experimental data from the literature for the transient behaviour of laponite gels.

Cite this publication as follows:
Quemada D: Aging, rejuvenation, and thixotropy in complex fluids: Time-dependence of the viscosity at rest and under constant shear rate or shear stress, Appl. Rheol. 18 (2008) 53298.

Investigations on the behaviour of superparamagnetic nanoparticles under the influence of a high gradient magnetic field in the vascular system is required for a better under-standing of magnetic drug targeting. The influence on the particle transport of the non-Newtonian and Newtonian properties of blood as well as the influence of the heart rate was therefore studied. An analytical model was developed and the calculation of particle trajectories is presented and evaluated.The results show that the non-Newtonian properties of the blood have a positive influence on the number of retended nanoparticles. The calculations also showed that the number of retained nanoparticles was lower in oscillatory flow profile than in steady flow. The influence of the heart rate can be neglected for Womersley numbers smaller than 1.5.

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Gleich B, Weyh T, Wolf B: Magnetic Drug Targeting: an analytical model for the influence of blood properties on particle trajectories, Appl. Rheol. 18 (2008) 52023.

Water soluble polymers such as cellulosic or starch ethers are often included in the mix-design of Self Compacting Concretes (SCCs) in order to improve their stability and robustness. The stability, including resistance to liquid-solid separation and sedimentation, may be attributed to the increase of the viscosity of the liquid phase due to the thickening effect of the polymer. The later is then referred to as a Viscosity-Modifying Admixture (VMA). In the present study, we consider the influence of VMAs on the rheological properties of the material at cement scale level. In particular, the change in the thixotropic properties of the cement paste due to the inclusion of VMA is investigated. It is found that addition of VMA significantly enhances rebuild-up kinetics at rest following shearing at high shear rate. The influence of VMA on the steady state rheological properties is also considered. As reported in the literature, the yield stress is found to monotonically increase with VMA content, while the consistency presents a minimum indicating the existence of an optimum value of the VMA for which the workability of the cement paste is maximum.

Cite this publication as follows:
Bouras R, Chaouche M, Kaci S: Influence of Viscosity-Modifying Admixtures on the Thixotropic Behaviour of Cement Pastes, Appl. Rheol. 18 (2008) 45604.

In the present study, an evolution equation for the Cauchy stress tensor is proposed to take elastic, viscous and plastic characteristics of complex fluids simultaneously into account. In particular, hypoplasticity is incorporated to account for the plastic features. The stress model is applied to investigate time-dependent flows of an elasto- visco-plastic fluid driven by an oscillating boundary with/without an additional stationary boundary to study the cyclic responses and the model performance. Numerical simulations show that while different degrees of elastic and viscous effects can be captured by varying the model parameters, plastic deformation plays a significant role in the velocity distribution, and can be simulated appropriately by use of hypoplasticity. The stress model is capable of accounting for the combined elastic, viscous and plastic features of complex materials in transient motions, and applications may be found in geomorphic fluid motions like granular and debris flows, and flows involving polymers.

Cite this publication as follows:
Fang C, Lee C: Unsteady parallel flows of an elasto-visco-hypoplastic fluid with oscillating boundary, Appl. Rheol. 18 (2008) 45001.

The yield stresses of five samples (two highly concentrated emulsions, two Kaolin dispersions and mayonnaise) were determined in two ways. In one case, steady shear experiments were performed over a range of incrementally decreasing shear rates. The resulting flow curves, plotted as shear stress against shear rate, clearly showed the existence of a yield stress for each sample, the Herschel-Bulkley model being fitted to obtain values. In the second case, oscillatory amplitude sweeps were performed at three frequencies, and the .dynamic yield stress. was defined as the stress at which deviation from linearity occurred; this procedure has often been used to determine the yield stress of emulsions. It was found that the dynamic yield stress is frequency dependent, and cannot therefore be thought of as physically meaningful material property. At no frequency did the dynamic yield stress correlate with the yield stress obtained from the flow curves.

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Masalova I, Malkin AY, Foudazi R: Yield stress as measured in steady shearing and in oscillations, Appl. Rheol. 18 (2008) 44790.

The main characteristics of geological flows such as debris flows, avalanches and lahars is due to the relative importance of viscous versus inertial forces in the momentum balance.This paper considers the motion generated by the collapse of a damretaining mud, itself modeled as a power-law fluid. The equation of motion is derived in a non-dimensional form and solved analytically with the shallow-water assumption in a dry and smooth horizontal channel. Notably indicated are flow regimes and the effect of the reservoir length as well as the effect of mud rheology on flow development. Then, a parametric study of this model is produced and the effect of mud shear-thinning on flow development is pointed out.

Cite this publication as follows:
Nsom B, Ravelo B, Ndong W: Flow regimes in viscous horizontal dam-break flow of clayous mud, Appl. Rheol. 18 (2008) 43577.

A methodology is presented to invert the flow equation of a Herschel-Bulkley fluid in Couette concentric cylinder geometry, thus enabling simultaneous computation of the true shear rates, ΓHB, and of the three Herschel-Bulkley rheological parameters. The errors made when these rheological parameters are computed using Newtonian shear rates, ΓN, as it is normal practice by research and industry personnel, can then be estimated. Quantification of these errors has been performed using narrow gap viscometer data from literature, with most of them taken with oil-field rheometers. The results indicate that significant differences exist between the yield stress and the flow behavior index computed using ΓHB versus the parameters obtained using ΓN and this is an outcome of the higher ΓHB values. Predicted true shear rates and rheological parameters are in very good agreement with results reported by other investigators, who have followed different approaches to invert the flow equation, both for yield-pseudoplastic and power-law fluids.

Cite this publication as follows:
Kelessidis V, Maglione R: Shear rate corrections for Herschel-Bulkley fluids in Couette geometry , Appl. Rheol. 18 (2008) 34482.

A new procedure is described to convert the vane torque and rotational velocity data into shear stress vs shear rate relationships. The basis of the procedure consists in considering locally the sheared material as a Bingham fluid and computing a characteristic shear rate from Couette analogy. The approach is first applied to experimental vane data of Newtonian fluid, then used to process vane experimental data of non-Newtonian and yield stress materials. Results, which are favourably compared with torsional flow, show that the approach correctly predicts the rheological behaviour of the materials investigated.

Cite this publication as follows:
Estelle P, Lanos C, Perrot A, Amziane S: Processing the vane shear flow data from Couette analogy, Appl. Rheol. 18 (2008) 34037.

Electrorheological fluids (ERF) change viscosity when an electric field is applied. A special type of ERF consists of polyurethane particles which are doped with Li+ and/or Zn2+ cations and suspended in silicone oil.This article gives an overview of the temperature dependent behavior of the ER effect for these fluids and describes the basic principles how this is explained. Chemical analyses provide information as a basis for a polarization model in several dimensions down to molecular size.

Cite this publication as follows:
Schneider S, Eibl S: Review of the Electrorheological (ER) Effect of Polyurethane-based ER Fluids, Appl. Rheol. 18 (2008) 23956.

Rheological behavior of asphalt is strongly affected by loading conditions, temperature and environment. One of the main challenges in understanding the rheology of asphalt is to relate the chemical constituents and the micro-structure of asphalt on one hand to its rheological behavior on the other hand. In this work, nonlinear rheological behaviour of asphalt was investigated using a structural rheological model. A first order kinetic equation to describe structural changes in asphalt has been incorporated with the nonlinear rheological model of White- Metzner. The resulting set of governing equations was solved numerically to describe the rheology of asphalts. Different modes of rheological testing and asphalts with different compositions were considered. An analysis and comparison of model behaviour with experimental data from the literature is carried out in both stress growth at constant shear rate and oscillatory shear modes. A strategy is proposed for the estimation and tuning of the model parameters based on available experimental data and literature. Qualitatively, the model can capture the rheological behaviour of non-Newtonian fluids such as asphalt under different modes of rheological testing. Quantitative analysis from this work shows that the model describes the rheological behaviour of asphalt for the temperature range of 20 - 60oC. It is demonstrated that a single set of equations tuned with the steady shear experimental data can be used to predict the nonlinear rheological behaviour of asphalts. In addition, it is shown that the model parameters can be related to the chemical composition of asphalts.

Cite this publication as follows:
Vijay R, Deshpande AP, Varughese S: Nonlinear rheological modeling of asphalt using White-Metzner model with structural parameter variation based asphaltene structural build-up and breakage, Appl. Rheol. 18 (2008) 23214.

Small micellar casein particles were formed in aqueous solutions of native casein after addition of polyphosphate. These socalled submicelles aggregated and gelled with a rate that increased with increasing temperature.The evolution of the viscosity during this process was determined at constant shear rate or shear stress. When applying a small shear stress the viscosity increased strongly until the shear rate became immeasurably slow, but when the applied shear stress exceeded a critical value (σc) the aggregates broke up and the viscosity reached a maximum. At longer times the viscosity decreased rapidly at first, followed by a very slow decrease. sc was independent of the shear rate and heating temperature, but increased strongly with increasing casein concentration.At constant shear rate the stress remained close to σc, but fluctuated irregularly.After cessation of shear flow, gels were formed rapidly. Oscillation shear measurements for σ > σc showed a strongly non-linear response at the time of maximum viscosity.

Cite this publication as follows:
Pitkowski A, Nicolai T, Durand D: Shear flow and large amplitude oscillation shear study of solutions of aggregating micellar casein particles, Appl. Rheol. 18 (2008) 23050.

Cite this publication as follows:
Ancey C: Visco-plastic fluids: from Theory to Application, Appl. Rheol. 18 (2008) 48.

The new ARES-G2 is a rotational rheometer based on the unique concept of separation of motor and force/torque transducer. Designed from ground up, a key objective of the development project was to provide increased flexibility designing rheological experiments and to allow new and application specific test procedures. In order to achieve these goals all major instrument components such as the actuator, transducer, stage, data acquisition, environmental systems, etc. are developed as independent intelligent sub-assemblies, controlled by a central processor. The rigid firmware based on fixed test modes is replaced with a versatile user interface allowing a free combination of instrument instructions, which are downloaded to the instrument prior testing. Fast digital signal processing replaces the analog electronics providing faster, more accurate motor and transducer control and allowing the implementation of full stress control in oscillation and transient test modes. Significantly improved data acquisition with 5 fast data channels in all test modes enables SAOS and enhanced laOS testing with complete support of higher harmonic analysis.

Cite this publication as follows:
Franck A: A new generation of separate motor and transducer rheometers, Appl. Rheol. 18 (2008) 44.

We show that the rheological characteristics of a fresh cement paste can be determined from inclined plane tests.The apparent flow curve measured from inclined plane flows coincides with the apparent rheogram from classical rheometer tests and the flow curve obtained from local Couette flow measurements with magnetic resonance imaging (MRI). In order to describe the thixotropic properties of these fluids we suggest to use a simple model, the four parameters of which may be determined from specific, practical, inclined plane experiments.

Cite this publication as follows:
Jarny S, Roussel N, LeRoy R, Coussot P: Thixotropic behavior of fresh cement pastes from inclined plane flow measurements, Appl. Rheol. 18 (2008) 14251.

a new technique of reconstruction of the velocity profile, the behaviour can be modelled by a unique equation including liquid and solid components but also a structural parameter. It is also rigorously demonstrated that the only one rheological behaviour in steady state in the liquid regime is a truncated power-law which can be defined only for a shear rate and a shear stress higher than a critical value. Moreover, the critical shear rate and shear stress increase with the solid content and depend on the fractal dimension of flocs which implies that thixotropic effects are all the more important as the sludge is thick and fresh.

Cite this publication as follows:
Baudez J-C: Physical aging and thixotropy in sludge rheology, Appl. Rheol. 18 (2008) 13495.

The rheologies of a shear-frozen commercial ice cream and of a model ice cream foam have been studied at - 5oC and other temperatures by capillary rheometry on a commercial manufacturing line and in a Multi-Pass Rheometer, respectively. Both were 50 vol% aerated emulsions of milk fat in an aqueous sucrose solution, but the model ice cream foam was without ice crystals. The data indicate significant wall slip effects which have been analysed using the classical Mooney method, the Jastrzebski variant and one based on Tikhonov regularization. The latter approach yields 'most convincing results', including a previously unreported region of shear thickening at very high shear rates of ~ 3000 s-1 for the model ice cream foam, when the capillary number indicates a possible transition in the flow around bubbles from domination by interfacial effects to viscous effects. Viscous heating effects were observed at relatively low shear rates for the commercial ice cream, but not the model ice cream foam. This was attributed to the melting of the ice crystal phase in the commercial ice cream, and, hence, absent from the model ice cream foam.

Cite this publication as follows:
Martin P, Odic K, Russell A: Rheology of commercial and model ice creams, Appl. Rheol. 18 (2008) 12913.

Effectiveness of drag reduction by small addition of a surfactant in the turbulent flow of water depends on the structure and concentration of the additive, temperature of the solution and turbulence intensity, possible flow disturbance by a mechanical obstacle and the content of ions in water, but also on the age of the surfactant solution.We show how important aging effects are in connection with total surfactant concentration, in particular how rheological parameters of the drag reducing solution change with time.

Cite this publication as follows:
Mik V, Myska J, Chara Z, Stern P: Durability of a Drag Reducing Solution, Appl. Rheol. 18 (2008) 12421.

The XVth International Workshop on Numerical Methods for Non-Newtonian Flows (XVth IWNMNNF 2007) was held on the island of Rhodes, Greece, in June 6 - 10, 2007. Since their inception in 1979, in Providence, Rhode Island, USA, the workshops are rotated biennially between North America and Europe. This was the first time the meeting was held in Greece. Rhodes Island was a proper destination, as the meetings have come a full circle after almost 30 years of frantic activity, which have seen workshop meetings in castles, lakes, islands, seasides. Rhodes, as the capital of the Dodecanese Islands, combines all of the above, and has been a place of tourism and holidays since antiquity. The XVth IWNMNNF was by all measures a truly international event, drawing around 60 scientists and engineers from 18 countries around the world. The Workshop included a plenary lecture by Roger Tanner, from University of Sydney, Australia, and 7 thematic sessions. [more]

Cite this publication as follows:
Mitsoulis E, Mavrantzas VG: Numerical Methods for Non-Newtonian Flows - XVth IWNMNNF 2007, Appl. Rheol. 17 (2007) 354.

Genetic Programming (GP) is used to estimate the functions that describe the torque and the force acting on the external sphere due to steady state motion of viscoelastic fluid between two eccentric spheres. The GP has been running based on experimental data of the torque at different eccentricities to produce torque for each target eccentricity. The angular velocity of the inner sphere and the eccentricity of the two spheres have been used as input variables to find the discovered functions. The experimental, calculated and predicted torque and forces are compared. The discovered function shows a good match to the experimental data.We find that the GP technique is a good new mechanism of determination of the force and torque of fluid in eccentric sphere model.

Cite this publication as follows:
Elbakry M, Radi A: Genetic programming approach for flow of steady state fluid between two eccentric spheres, Appl. Rheol. 17 (2007) 68210.

The assumptions implicit in the simplified expressions used to convert the torque-rotational speed data of parallel-disk viscometry into rim shear rate and rim shear stress are identified. The rim shear stress generated by the simplified expression is compared against the actual rim shear stress. The error involved is quantified for two standard rheological models and for a set of laboratory data. Under normal operation conditions of parallel-disk viscometers this error was found to be within the acceptable limit. However, for highly shear thinning fluids and for fluids exhibiting yield stress this error can become very large. The suitability of the approximate rim shear stress in wall slip determination is then briefly discussed.

Cite this publication as follows:
LeongYeow Y, Leong Y, Khan A: Error Introduced by a Popular Melthod of Processing Parallel-Disk Viscometry Data, Appl. Rheol. 17 (2007) 66415.

The dynamic viscoelastic properties of liquid crystalline polymer (LCP) and polyethylene terephthalate (PET) blends were studied at two different temperatures: 265 oC at which LCP was in solid state and 285 oC at which LCP was in molten state. The PET was in molten state at both the temperatures. The storage modulus, G', loss modulus, G'', dynamic viscosity, η', of blends with different compositions were evaluated and compared. The morphology of these samples was studied using scanning electron microscope, which exhibited composition dependency. A maxima was observed in the viscosity versus composition plot corresponding to 90/10 LCP/PET blend at 285oC. The G' versus G'' plots demonstrated the composition dependency of LCP/PET blends.

Cite this publication as follows:
Hashmi SAR, Kitano T: Effects of State Change of Liquid Crystalline Polymer on Dynamic Visco-elasticity of its Blends with Polyethylene-terephthalate, Appl. Rheol. 17 (2007) 64510.

A newly designed and constructed sliding plate rheometer is used to measure the high frequency (210 Hz) linear viscoelastic properties of two model polymers: polybutene (PB) and polydimethylsiloxane (PDMS). Using well-known rheological models, extrapolations of the viscoelastic measurements obtained on a rotational parallel plate rheometer to a frequency of 210 Hz are used to assess the performance of the high frequency sliding plate rheometer. Good agreement between the extrapolated and measured data demonstrates the ability of the sliding plate rheometer to measure the high frequency rheological properties of both Newtonian and shear-thinning materials.

Cite this publication as follows:
Braybrook CA, Lee JA, Bates PJ, Kontopoulou M: Development of a Sliding Plate Rheometer to Measure the High Frequency Viscoelastic Properties of Polymer Melts, Appl. Rheol. 17 (2007) 62563.

We apply the landmark Paper Index (LPI), calculate and analyze indices for all papers published in rheological journals (`η-journals') between 1991 and 2007. We discuss the effect of formal criteria on the LPI.

Cite this publication as follows:
Kroger M: Landmark paper index: Application to rheological (η) journals, Appl. Rheol. 17 (2007) 66494.

Cite this publication as follows:
Schweizer T: Structure and rheology of molten polymers (J.M. Dealy, R.G. Larson), Appl. Rheol. 17 (2007) 258.

The influence of the molecular structure of the polymer matrix and filler loading on the entrance pressure loss of polyethylene/ wood flour composites has been investigated in this research by means of a capillary rheometer equipped with an orifice die. The entry flow of talc- and glass-filled polyethylene composites has been investigated as well. It was found that the entrance pressure loss of wood filled polyethylene composites greatly increased with increasing the wood flour loading. Talc and solid glass spheres also increase the entrance pressure loss, however not as much as wood flour. It was also observed that composites based on narrow molecular weight distribution (MWD) resins exhibited larger entrance pressure loss than the broad MWD and branched polyethylene based ones. It was concluded that measurements of the entrance pressure loss reveal some interesting features of the polymer-filler interactions and could provide significant insights in the processing of highly filled polymer melts.

Cite this publication as follows:
Hristov V, Vlachopoulos J: A Study of Entrance Pressure Loss in Filled Polymer Melts , Appl. Rheol. 17 (2007) 57191.

Self-Compacting Concrete is a new type of concrete which is more liquid compared to traditional concrete and which does not need any form of external compaction. As a result this type of concrete is suitable for a new placing technique: pumping SCC from the bottom in the formwork and letting it rise in the formwork due to the applied pressure. In order to understand the phenomena occurring during pumping operations, the rheological properties of SCC must be investigated and controlled. Tests have been performed with two different rheometers, which are described in this paper. For the Tattersall Mk-II rheometer, a calibration procedure has been worked out to eliminate secondary flows in the rheometer.Test results indicate that SCC is a thixotropic liquid, having a yield stress, showing shear thickening and having varying properties in time due to the occurring chemical reactions. In this paper, the time dependent effects will not be described. When trying to apply a rheological model to the obtained results, only the modified Bingham model seems appropriate. Applying the Bingham model results in the generation of negative yield stresses while the Herschel-Bulkley model has a parameter with a variable dimension and has a major mathematical restriction. The rheological properties of fresh SCC can be described with the modified Bingham model. A suitable parameter to describe shear thickening is defined as the ratio of the second order term in the shear rate of the modified Bingham model to the linear term (= c/μ).

Cite this publication as follows:
Feys D, Verhoeven R, DeSchutter G: Evaluation of time independent rheological models applicable to fresh Self-Compacting Concrete, Appl. Rheol. 17 (2007) 56244.

The elongational flow of polymethylmethacrylate / nano-clay composites was studied during stressing and creep experiments using a Müt tensile rheometer (MTR). The dispersion of the nano-clay was controlled by means of transmission electron microscopy (TEM) and the layer distance was measured with X-ray diffraction (XRD).With growing volume fraction of the filler an increase of the viscosity is observed under constant strain rate and constant stress conditions. The results for the elongational viscosities for both modes are consistent with each other. Furthermore, a strain softening behavior can be measured, which is the more pronounced the higher the nano-clay content is. As the Trouton rule is not valid, deviations from the linear behaviour are related to an envolope curve for the elongational viscosities instead of the threefold zero shear viscosity.

Cite this publication as follows:
Katsikis N, Koniger T, Munstedt H: Elongational viscosities of polymethylmethacrylate / nano-clay composites, Appl. Rheol. 17 (2007) 52751.

Cite this publication as follows:
Coussot P, Barrat J: Flow in Glassy Systems. European School of Rheology, Appl. Rheol. 17 (2007) 228.

Rheo-optics is a method that allows the analysis of optical properties, like birefringence and dichroism under steady and oscillatory shear. It is possible to correlate macroscopic mechanical responses with induced microscopic changes in the material. We describe how this method was improved several fold and implemented on a commercially available setup. However, the here presented ideas are applicable to any rheo-optical setup, based on modulation of the laser light. Additionally it does not need a lock-in amplifier and therefore reduces the costs of the setup.

Cite this publication as follows:
Klein C, Venema P, Sagis L, vanDusschoten D, Wilhelm M, Spiess HW, vanderLinden E, Rogers SS, Donald AM: Rheo-optical Measurements using Fast Fourier Transform and Oversampling, Appl. Rheol. 17 (2007) 45210.

Rheological and mechanical properties of acrylonitrile-butadiene-styrene polymers (ABS) prepared via bulk polymerization depending on the molecular weight (Mw) of styrene-acrylonitrile copolymer (SAN) have been investigated.The tendencies of attaining the yield stress at steady-state shear flow and approaching to the .plateau. region of storage modulus at low frequencies in oscillatory tests were observed. Both these phenomena are induced by formation of the structural skeleton consisting of polybutadiene (PB) particles arranged in the SAN-matrix. Growth of Mw of SAN leads both to increase of the .plateau. value of storage modulus at low frequencies and the yield stress.This fact can be explained by the influence of Mw of SAN chains grafted onto PB particles on structure formation in ABS melts because of a redistribution of the ratio particleparticle / particle-matrix interactions. The elongational viscosity of ABS melts is a power function of Mw of SAN matrix. The power index of this function increases with the polymer straining that reflects orientation of SAN chains with their length increase. The strain-hardening index of ABS melts increases considerably with increase of SAN matrix Mw. However, it does not depend on presence of PB particles in the material. It means that the value of this index is governed by orientation effect in the SAN matrix.The impact strength of the investigated ABS samples is interrelated with rheological characteristics of ABS melts as well as Mw of SAN. The dependence of impact strength on Mw can be explained by increasing role of orientation effects of SAN chains with Mw increase in the copolymer fibrils connecting the walls of crazes formed at impact action.

Cite this publication as follows:
Dreval VE, Vasilev G, Borisenkova E, Semakov A, Kulichikhin VG: Influence of Molecular Weight of SAN on Rheological and Mechanical Properties of ABS-plastics, Appl. Rheol. 17 (2007) 44745.

Nowadays it is necessary to perform experimental measurements to compare with numerical calculations. In this study we focus on different aqueous solutions which are tested to obtain in the same time a rheological blood like fluid and particular optical properties for laser measurements (particle image velocimetry (PIV) or laser Doppler velocimetry (LDV)). Using viscometric tests we show that the non Newtonian behavior of blood is reached by adding xanthan gum in aqueous glycerol and aqueous potassium thiocyanate solutions. Optical properties are directly achieved by modifying glycerol or thiocyanate potassium concentrations. Indeed we proove using refractometric measurements that the addition of xanthan gum does not affect the value of the refractive indexes. Finally,we can prepare an optical blood like fluid adapted to cardiovascular studies by adjusting the proportion of the different components.

Cite this publication as follows:
Benard N, Jarny S, Coisne D: Definition of an experimental blood like fluid for laser measurements in cardiovascular studies., Appl. Rheol. 17 (2007) 44251.

The concentration and size dependencies of elastic properties of highly concentrated w/o emulsions were studied. The range of weight concentration of the disperse phase was 90 - 96%, the range of the average droplet size was 16 - 20 μm, and the droplet size distribution remained unchanged. The disperse phase consists of droplets of over-cooled concentrated aqueous solutions of inorganic salts. The concentration range being studied lies above the limit of maximal close packing, φ > φm. The droplet size distribution is fairly wide and the shape of droplets is polygonal.These factors alone determine possible new rheological effects, such as the elasticity and visco-plastic behaviour of emulsions, as well as the observed form of concentration and size dependencies of rheological properties of emulsions. The complete flow curves were measured for these fairly new emulsion systems. It emerged that they were similar to the entire concentration and droplet size ranges being studied. The concentration dependencies of the yield stress and storage modules corresponded to the Princen-Kiss theory with critical volume concentration approximately 0.71 - 0.74. However, this theory describes the size dependence of elastic modules incorrectly. A new model is proposed, which correctly describes the dependencies of elastic modules on both determining parameters - those of concentration and droplet size.

Cite this publication as follows:
Masalova I, Malkin AY: Rheology of highly concentrated emulsions - concentration and droplet size dependencies, Appl. Rheol. 17 (2007) 42250.

This paper presents a characterization of the following dry granular materials: soya, colza and rye seeds. The physical properties of the grains and the materials are useful for characterizing the materials behaviour during flow, while the external conditions (consolidation) determine storage and handling conditions. The physical properties of the grains (specific densities) and of the materials as a whole (compacity or porosity, and critical angles) were measured. The flow functions were determined by modified shear box testing. Then the internal friction angles and the flowability index for each granular material were obtained. Indeed, the behaviour of a flowing granular material results from these two groups of factors and is characterized by the flowability, which is the ratio of highest consolidation stress and unconfined yield strength. In practice, the flowability index is used to classify materials, so that the larger the flowability index, the smaller the bulk solids strength will be in relation to the consolidation stress, and therefore the higher the flowability of the bulk solid.

Cite this publication as follows:
Degouet C, Nsom B, Lolive E, Grohens A: Characterization of wood granules, soya, colza and rye seeds, Appl. Rheol. 17 (2007) 36546.

The effects of free surface shape on normal stress difference measurements in cone and plate flow are investigated. The analysis shows that the stress field is significantly altered by deviations of the free surface from an ideal (spherical) shape. For the cone and partitioned plate technique, it is shown how modest deviation from a spherical free surface shape can lead to errors of roughly 10% in the measured normal stress differences.

Cite this publication as follows:
Venerus DC: Free Surface Effects on Normal Stress Measurements in Cone and Plate Flow, Appl. Rheol. 17 (2007) 36494.

Pre-thickened beverages and barium sulfate suspensions are used in the treatment and diagnosis of dysphagia. These liquids are labeled nectar consistency (NC), honey consistency (HC) etc.These labels are rather misleading and do not represent the actual rheological character of the liquids.We carefully investigated the rheology of these liquids to assist both in their formulation and use for dysphagic patients. Steady state flow properties, thixotropy, dynamic response, and creep recovery behavior were investigated for six beverages and two barium sulfate suspensions. All samples exhibited a shear-thinning behavior. The flow curves of all samples followed both Herschel-Bulkley and Casson models. HC barium sulfate suspension exhibited higher yield stress, σ0, and higher storage modulus, G', than their fluid food counterparts. In contrast, NC barium sulfate suspension had lower σ0, and G' than some of the liquid food counterparts. Frequency spectra of NC samples were similar to that of a macromolecular solution with both G' and loss modulus, G'', increasing with frequency; whereas those of HC samples were similar to that of a gel with a little dependency of G' and G'' over frequency. Stress sweep experiments showed that the linear viscoelastic region of fluid foods and barium sulfate suspensions extended up to 1 and 10 Pa, respectively. Thus, significant differences exist in the rheological properties of both pre-thickened and videofluoroscopy fluids currently used for diagnosis and treatment of dysphagia.

Cite this publication as follows:
OuldEleya MM, Gunasekaran S: Rheology of fluid foods for dysphagic patients, Appl. Rheol. 17 (2007) 33137.

We present results from a new approach to the study of multicomponent gels, which allows independent investigation of the effect of phase volume and droplet size of the dispersed phase on the mechanical properties of the mixed gel composites. The method involves preparation of agarose microgels with different sizes, which are then embedded in maltodextrin gel matrices with different gel strengths. The effects of both phase volume and droplet size on composite properties are dependent on the phase modulus ratio. The higher the phase modulus ratio, the larger is the reinforcement effect and the effect of droplet size on mechanical properties of the maltodextrin/agarose composites. The observed behaviour was compared with literature models for the behaviour of composite materials.

Cite this publication as follows:
Loret C, Frith WJ, Fryer PJ: Mechanical and structural properties of maltodextrin/agarose microgels composites, Appl. Rheol. 17 (2007) 31412.

Cite this publication as follows:
Remond Y, Patlazhan S: The EUROMECH Colloquium 487. Structure Sensitive Mechanics of Polymer Materials: Physical and Mechanical Aspects, Appl. Rheol. 17 (2007) 108.

Models of kinetic theory provide a coarse-grained description of molecular configurations wherein atomistic processes are ignored. The Fokker-Planck equation related to the kinetic theory descriptions must be solved for the distribution function in both physical and configuration spaces. When the model involves high dimensional spaces (including physical and conformation spaces and time) standard discretization techniques fail due to excessive computation requirements. In this paper, we revisit some model reduction techniques recently proposed to circumvent those difficulties, exploring other new application areas related to entangled polymer models as well as the use of such reduced models for treating complex flows in which the distribution function involves both the physical and the conformation coordinates.

Cite this publication as follows:
Mokdad B, Pruliere, re E, Ammar A, Chinesta F: On the simulation of kinetic theory models of complex fluids using the Fokker-Planck approach, Appl. Rheol. 17 (2007) 26494.

We describe methodology of laser Doppler forced vibrology (LDFV) applied to texture assessment of soft agricultural products. The method is applied to a melon. The lowest frequency resonant peak (mode M0) is used for corrections of the whole amplitude frequency plot expressed in relation to the forcing deformation level. The main differences between vibrology in vertical and horizontal laser positions are described. Missing and/or degeneration of some modes in the laser horizontal position are explained. Peak analysis of the results obtained reveals the parameters connected with information on internal damping, i.e. internal viscosity. Modulus of elasticity is calculated either from the peak frequency of the M1 mode or by a new method from the M0 peak frequency. The modulus of elasticity of the latter method is nearly one order higher and is more variable than the former probably because the M0 mode is related to physical properties of the surface of the melon in contact with the vibrating table. Fine structure of the skin can lead to possible degenerated forms with more sub-peaks.

Cite this publication as follows:
Blahovec J, Akimoto H, Sakurai N: Laser Doppler Forced Vibrology of Soft Agricultural Products, Appl. Rheol. 17 (2007) 25111.

A specific twin channel slit die was used to measure in-line the viscous behaviour of an extruded wheat starch. This allows to put in evidence the influences of temperature, water content and specific mechanical energy (SME). The proposed rheological law permits to satisfactorily predict the viscosity of a wheat starch for any processing condition. Original results are presented for the behaviour of cationic starches obtained by reactive extrusion.

Cite this publication as follows:
Berzin F, Tara A, Tighzert L: In-line measurement of the viscous behaviour of wheat starch during extrusion. Application to starch cationisation., Appl. Rheol. 17 (2007) 21222.

The rheological behaviour of frozen soils depends on a number of factors and is complex. Stress and temperature histories as well as the actual composition of the frozen soil are only some aspects that have to be considered when analysing the mechanical response. Recent improvements in measuring methods for laboratory investigations as well as new theoretical models have assisted in developing an improved understanding of the thermo-mechanical processes at play within frozen soils and representation of their response to a range of perturbations. This review summarises earlier work and the current state of knowledge in the field of frozen soil research. Further, it presents basic concepts as well as current research gaps. Suggestions for future research in the field of frozen soil mechanics are also made. The goal of the review is to heighten awareness of the complexity of processes interacting within frozen soils and the need to understand this complexity when developing models for representing this behaviour.

Cite this publication as follows:
Arenson LU, Springman SM, Sego DC: The Rheology of Frozen Soils, Appl. Rheol. 17 (2007) 12147.

Rheology is commonly used as a tool for analytics and quality control in latex technology. As soon as flow becomes essential for the structure measured in a scattering experiment we call it scattering from shear-ordered dispersions or rheologic scattering. In this paper it is shown that the structure of concentrated dispersions can with advantage be studied by scattering experiments. Theoretical and experimental aspects as well as examples of small-angle synchrotron x-ray and neutron scattering from colloidal dispersions, presented in the paper, are closely related to rheology.

Cite this publication as follows:
Versmold H: Scattering from shear-ordered dispersions, Appl. Rheol. 17 (2007) 11412.

The rheological behavior of a fugitive organic ink tailored for direct-write assembly of 3D microfluidic devices is investigated. Rheological experiments are carried out to probe the shear storage and loss moduli as well as the complex viscosity as a function of varying temperature, frequency and stress amplitude. Master curves of these functions are assembled using time-temperature superposition. The fugitive ink, comprised of two organic phases, possesses an equilibrium shear elastic modulus nearly two orders of magnitude higher than that of a commercial reference ink at room temperature and a peak in the relaxation spectrum nearly six orders of magnitude longer in time scale. The self-supporting nature of extruded ink filaments is characterized by direct video imaging. Comparison of the experimentally observed behavior to numerical predictions based on Euler-Bernoulli viscoelastic beam analysis yield excellent agreement for slender filaments.

Cite this publication as follows:
Therriault D, White S, Lewis J: Rheological Behavior of Fugitive Organic Inks for Direct-Write Assembly, Appl. Rheol. 17 (2007) 10112.

Cite this publication as follows:
Chhabra R, Slatter P: First Conference of the Southern African Society of Rheology (SASOR), Appl. Rheol. 17 (2007) 41.

Cite this publication as follows:
Wagner C: Microrheology and Rheological Phenomena in Microfluidics 2006 Workshop of the German Rheological Society (DRG) , Appl. Rheol. 17 (2007) 42.

Cite this publication as follows:
Cheneler D: Introduction to Polymer Viscoelasticity (M.T. Shaw, W.J. MacKnight), Appl. Rheol. 17 (2007) 10.

In this paper, by means of Advanced Rheometric Expanded System (ARES), oscillatory and steady shear behavior of binary mixtures of a quaternary ammonium based ionic liquid [Me3NC2H4OH]+[Zn2Cl5]- with ethanol (EtOH) were determined at 25 C and 25-50 C, respectively. The effects of shear rate, temperature and concentration on viscosity were elucidated sufficiently. It was found that the solutions show pseudo-plastic behavior at low shear rate and Newtonian property at higher shear rate. The addition of EtOH caused a substantial decrease in viscosity of the ionic liquid and the viscosity of binary mixtures could be described by an exponential equation. Arrhenius Equation and Power law equation were applied to describe the respective effects of temperature and shear rate on viscosity. Activation energy derived from Arrhenius equation decreased with increasing the EtOH fraction in the mixture.

Cite this publication as follows:
Li Q, Wu G, Liu Y, Luo Y: A rheological study of binary mixtures of Ionic Liquid [Me3NC2H4OH]+[Zn2Cl5]- and ethanol, Appl. Rheol. 16 (2006) 334.

We define a landmark Paper Index (LPI), calculate and analyze indices for all papers published in rheological journals ('η-journals') between 1990 and 2006. This paper offers some information about the criteria influencing the impact of publications on the (scientific) community. In opposite to the well known Impact Factor (journal sensitive) or the number of citations (article sensitive, publication year insensitive) the LPI helps to identify established and potential breakthrough contributions by considering the number of citations per year after publication, in a way which does not overestimate the few, highly cited, articles when performing averages. We discuss the effect of formal criteria on the LPI.

Cite this publication as follows:
Kroger M: Landmark Paper Index: Definition and Application to Rheological (η-)Journals, Appl. Rheol. 16 (2006) 329.

In Couette rheometry, most of the current flow-curve recovery algorithms require the explicit numerical differentiation of the measured angular velocity data. The exceptions and popular choices, because it avoids the need for a numerical differentiation, are the parallel plate approximation (cf. Bird et al. [1], Table 10.2-1) and the simplest of the formulas given in Krieger and Elrod [2]. However, their applicability is limited to narrow gap rheometer data. In this paper, equally simple formulas are presented which are exact for Newtonian fluids, do not involve a numerical differentiation and are consistently more accurate than the simple formulas mentioned above. They are based on a generalization of the Euler-Maclaurin sum formula solution of the Couette viscometry equation given in Krieger and Elrod. As well as illustrating the improved accuracy for the recovery of flow-curves for fluids with and without a yield-stress, details about more general and accurate formulas for flow-curve recovery from Couette rheometry data are given. The situation for the recovery of flow-curves from wide gap rheometery measurements is also discussed.

Cite this publication as follows:
deHoog F, Anderssen R: Simple and Accurate Formulas for Flow-Curve Recovery from Couette Rheometer Data, Appl. Rheol. 16 (2006) 321.

The lubricated semi-hyperbolic die has been proposed as a technique for generating uni-axial extensional flow and, hence, as a device for measuring elongational viscosity. Two methods for extracting extensional viscosity data for polymer melts in laminar flow from this device have been proposed and are evaluated here. Following the approach proposed by Collier and coworkers, values of the transient extensional viscosity, ηc+, obtained from a non-lubricated semi-hyperbolic (SHPB) die for several polyethylene (PE) melts were found to be considerably higher than values obtained by means of the Münstedt type device. Furthermore, the values of ηc+ obtained from the SHPB die were considerably higher than the strain averaged values of ηc+ which Everage and Ballman proposed would be obtained from a lubricated SHPB. The pressure drop across a SHPB die was estimated assuming resistance was all due to wall shear (using the lubrication approximation) for two PE resins. In the case of low density PE (LDPE) the values agreed to within 20% of the measured values suggesting that shear effects at the die wall were dominating the pressure drop and not extensional stresses. An analysis was carried out which showed that in the presence of lubrication the conditions for which the values of ηc+ obtained from the SHPB would be relatively accurate (Hencky strains > 5.0).

Cite this publication as follows:
Baird DG, Huang J: Elongational Viscosity Measurements Using A Semi-Hyperbolic Die, Appl. Rheol. 16 (2006) 312.

Since its start in 1970, the international conference on Deformation, Yield and Fracture of Polymers has been held every three years in Churchill College, Cambridge, UK. Amongst the 'mechanical properties of polymers' aficionados these meetings have become known as the 'Churchill' conferences, an event that has been established as the leading conference on its subject world wide. ...

Cite this publication as follows:
Govaert LE, Meijer HEH: DYFP2006, the 13th int. conference on deformation, yield and fracture of polymers, Appl. Rheol. 16 (2006) 290.

The current computer simulation based study aims to elucidate the complex role that the state of aggregation and morphology of the food materials plays in determining their transport behaviour. Using Brownian dynamic simulations, applied to colloidal systems, we simulate the compression of two different dense layers of nanoparticles (with reversible and irreversible bonds), at interface, at three different compression rates. We determine the desired transport coefficient for these structures using a novel technique, originally proposed by Torquato and Kim (1990). This method allows us to consider complex structures in our study, for which calculations of effective transport coefficients using conventional methods, like finite elements and finite difference, would be relatively difficult. We first validate our algorithm by comparing its results with those of exact calculations, for different regular lattices. Our results are in excellent agreement with the theory. The variation in the transport coefficient of nano-particle monolayers during the compression, are also correlated with the build up of stress and changes in the structure of the films.

Cite this publication as follows:
Courtois P, Ettelaie R, Chen J: Numerical Studies of Transport Properties in Heterogeneous Food Systems, Appl. Rheol. 16 (2006) 275.

We provide an overview of transient extensional rheometry techniques for wheat flour doughs in which the deformation and material response is well defined. The behavior of a range of model doughs was explored with a Filament Stretching Extensional Rheometer (FISER). The measurements were also compared to data obtained with a new windup extensional rheometer; the SER universal testing platform. A simple empirical constitutive equation, which allows characterization of the experimental results with a small number of parameters, is presented to describe the resulting measurements. To characterize the relaxation modulus of the doughs, small amplitude shear tests were performed on samples that have been shear-mixed in a mixograph for varying lengths of time. The linear viscoelastic properties were found to exhibit a broad power-law dependence on the imposed oscillatory frequency that is very reminiscent of that exhibited by a critical gel. The critical gel model of Winter and Chambon was used as the basis for constructing a non-linear constitutive equation for the material stress by combining the relaxation modulus for the critical gel with a Lodge rubber-like liquid form for the kinematics. Transient uniaxial extensional data recorded from the FISER and SER instruments were then compared to the predictions of the constitutive equation. The model captures the initial powerlaw response and subsequent strain-hardening; however additional physics is required to describe the rheological phenomena at very large Hencky strains, including finite extensibility effects and filament rupture in extensional flows.

Cite this publication as follows:
Ng TS, McKinley GH, Padmanabhan M: Linear to Non-linear Rheology of Wheat Flour Dough, Appl. Rheol. 16 (2006) 265.

In this paper we describe the rheological behaviour of Ca2+-induced cold-set gels of whey protein mixtures. Coldset gels are important applications for products with a low thermal stability. In previous work [J. Agric. Food Chem. 54 (2006) 4229], we determined the state diagram for whey protein mixtures that were heated for 10 h at pH 2 at 80°C. Under these conditions, the major whey protein, β-lactoglobulin (β-lg), forms fibrils. When whey protein mixtures are heated at protein concentrations in the liquid solution regime of the state diagram, cold-set gels can be formed by adding Ca2+ ions at pH 7. We studied the rheological behaviour of cold-set gels for various sample compositions for whey protein mixtures. When keeping the total whey protein concentration constant, the elastic modulus, G., for the cold-set gels decreased for increasing α-lactalbumin and bovine serum albumin ratios, because less material (blg fibrils) was available to form a gel network. In the cold-set gels the interactions between the β-lg fibrils induced by the calcium ions are dominant. The β-lg fibrils are forming the cold-set gel network and therefore determine the gel strength. α-lactalbumin and bovine serum albumin are not incorporated in the stress-bearing structure of the gels.

Cite this publication as follows:
Bolder S, Hendrickx H, Sagis L, vanderLinden E: Ca2+-induced cold-set gelation of whey protein isolate fibrils, Appl. Rheol. 16 (2006) 258.

When two biopolymers are mixed together, they will normally phase separate to give two distinct phases. If the biopolymers are gelled during this phase separation, for instance by reducing the temperature, one phase is trapped in this other one and an emulsion-like composite structure is obtained. In this study, we investigated the effect of volume fraction and droplet size of this dispersed phase on the mechanical properties of maltodextrin/ agarose gel composites, where agarose is the dispersed phase. Mechanical properties of the different composites were investigated under large deformation using a rheometer with a vane geometry. These composites were also observed by confocal microscopy, allowing conclusions to be drawn regarding the microstructural origins of the observed mechanical behaviour.

Cite this publication as follows:
Loret C, Frith WJ, Fryer PJ: Mechanical and structural properties of maltodextrin/agarose gel composites, Appl. Rheol. 16 (2006) 248.

In this contribution, a brief review is given of the dynamics of emulsions in microconfined shear flow. The interest in confined flow is triggered by the increasing importance of microfluidic applications in the processing industries. In a first part, some important aspects of confinement on single droplet dynamics are highlighted. The validity of the conclusions drawn from this part are subsequently applied to more concentrated systems. It is shown that microconfined emulsions can exhibit rich dynamics, and can display some peculiar morphologies.

Cite this publication as follows:
Vananroye A, VanPuyvelde P, Moldenaers P: Morphology development during microconfined flow of viscous emulsions, Appl. Rheol. 16 (2006) 242.

The measurement of the shear rheology of concentrated particulate suspensions is important to a range of mixing, pumping and flow operations. The use of a four or six bladed vane attached to a rheometer in an open cup is a popular technique to achieve a rheological characterisation. A problem occurs in the use of automated software with a number of rheological devices for yield stress materials. A torque auto zero default causes the torque at the start of a test to be ignored, and can result in significant errors and underestimation of the yield stress or rheological response of the suspension. The potential effect of using a torque auto zero default is demonstrated for a concentrated particulate suspension of nickel laterite.

Cite this publication as follows:
Fisher DT, Boger DV, Scales PJ: Measurement errors in yield stress rheometry that arise from torque auto zero, Appl. Rheol. 16 (2006) 206.

The effect of viscoelasticity on multilayer polymer extrusion is discussed. In these coextrusion processes predetermined patterns are created with a remarkable breadth of complexity even in geometrically simple dies via elastic rearrangements caused by the second-normal stress differences. A computational method is offered, based on the mapping method, which quantitatively describes the flow-induced patterns. Besides that the results are esthetically beautiful, they are also relevant for practice, since process and die design optimization is now possible. Not only to minimize interface distortion, but potentially also to deliberately create new processes and products based on this flow-induced patterning of polymers.

Cite this publication as follows:
Anderson PD, Dooley J, Meijer HEH: Viscoelastic effects in multilayer polymer extrusion, Appl. Rheol. 16 (2006) 198.

This paper deals with a Magnetic Resonance micro-Imaging (MRI) analysis of asymptotic kinematics which is a condition adopted in some rheological characterisations. Asymptotic kinematics (for example the slow shearing ) aim is to evaluate material properties at ''equilibrium'', avoiding structural changes induced by external stimuli. Measured material functions in these mechanical conditions deal with the structure/morphology of materials and can be used to investigate the structure as a function of the state variables only, as temperature, pressure and composition. In this paper MRI experiments were performed to study some shear flow behaviours of surfactant wormy micelles made by lecithin/water and diluted in cyclohexane (reverse micellar phase L2). MRI was used as a non-invasive tool in order to follow the structural responses both during slow shearing and when the sample is stirred outside the linear behaviour range. Relations can be found between the typical NMR parameters, strictly related to the microstructure, and the rheological macroscopic parameters as zero-shear viscosity.

Cite this publication as follows:
Coppola L, Gabriele D, Nicotera I, Oliviero C: MRI Experiments as a Tool to Study Asymptotic-Shear Flow Behaviour of a Worm-Like Reverse Micellar Phase, Appl. Rheol. 16 (2006) 190.

Blends of 30-phr silica filled elastomeric chlorinated polyethylene (CPE) and natural rubber (NR) at the blend composition ratio of 80/20 CPE/NR were prepared with various mixing time from 120 to 600 s. Viscoelastic behaviours of cured and uncured blends were determined using two rheometers with different shear modes, i.e., the oscillatory rheometer (Rubber Process Analyser, RPA2000) and the rate-controlled capillary rheometer (Goettfert Rheotester 2000). Results obtained reveal that the viscoelastic behaviour of blends is influenced by the formation of silica transient network, particularly in cured blends. Mixing time affects viscoelastic properties of vulcanised blends to some extent which is due probably to the high extent of thermal degradation, but plays no significant role in viscoelastic properties of unvulcanised blends. The superimposition of oscillatory and steady shear results is possible when the elastic component is eliminated from the results.

Cite this publication as follows:
Phewthongin N, Saeoui P, Sirisinha C: Comparison of Viscoelastic Behaviour in Silica Filled Cured and Uncured cpe/nr Blends with Various Mixing Time, Appl. Rheol. 16 (2006) 182.

Cite this publication as follows:
Fischer P: Rheometry of Pastes, Suspensions and Granular Materials - Application in Industry and Environment (P. Coussot), Appl. Rheol. 16 (2006) 181.

Liquid crystalline polymer (LCP) and polyethylene terephthalate (PET) were blended in an elastic melt extruder to make samples having different volume fractions of constituent polymers. Shear stress, shear viscosity, first normal stress difference at different shear rates under steady state conditions of these blends were evaluated at two different temperatures 265 and 285°C. The LCP was in solid state at 265° C and in melt state at 285°C and was dispersed in molten matrix of PET at both temperatures. Shear viscosity of blend increased with addition of LCP in PET matrix. A maxima was observed in viscosity versus composition plot. Blends containing more than 50 vol. % of LCP in the blend show higher viscosity as compared to the constituent polymers. First normal stress difference, N1, increased with LCP content in the blend at 285°C when ploted against shear stress whereas at 265°C this trend was opposite. The increased value of N1 with shear rate was explained assuming a tendency of asymmetric particles to rotate under velocity gradient of suspending medium. At 285°C N1 varied with shear stress in two stages. First stage was characterized with high sensitivity of N1 with shear stress, which reduced in second stage on plastic deformation of LCP droplets.

Cite this publication as follows:
Hashmi SAR, Kitano T: Rheology of LCP/PET Blends at Solid and Molten States of LCP, Appl. Rheol. 16 (2006) 152.

In this work we investigate the rheological behaviour of macroscopic buoyant hard spheres dispersed in a shearthinning suspending fluid. We focus on the phenomenological study of the influence of the shear-thinning behaviour of the suspending medium on the effective apparent suspension viscosity at different volume fractions. In the oil industry, the effective viscosity concept is widely used and very useful to quickly characterize a change of viscosity due to an increase of the solid content. Viscosity measurements are compared to the effective viscosity of a suspension of hard spheres in an Ostwald fluid. The power law index of the suspending fluid is shown, both experimentally and theoretically, to influence strongly the volume fraction dependence of the suspension effective viscosity. All experimental results are shown to be quite correctly plotted on a master curve, with only one adjustable parameter, the maximum packing fraction φ_m. The best fit is obtained for φ_m = 0.57, corresponding to the theoretical maximum random packing volume fraction.

Cite this publication as follows:
Peysson Y, Aubry T, Moan M: Phenomenological Approach of the Effective Viscosity of Hard Sphere Suspensions in Shear-Thinning Media, Appl. Rheol. 16 (2006) 145.

The rheological behaviour of PVC plastisols composed of a blend of suspension and micro-suspension resins in different proportions was investigated. The present work was mainly focused on the variation of the zero shear viscosity versus the concentration of the extender resin. Hence, the packing fraction Fm was evaluated using the Krieger-Dougherty equation. These experiments confirmed the major influence of particle size distribution concerning the decrease of viscosity for concentrated suspensions. In addition, a model based on the porosity model developed by Ouchiyama et al. (Ouchiyama N, Tanaka T: "Porosity estimation for random packings of spherical particle", Ind. Eng. Chem. Fundam. 23 (1984) 490-493) to predict the packing fraction in the case of multimodal lattices was successfully applied to our PVC plastisols formulations.

Cite this publication as follows:
Laine C, Cassagnau P: Prediction of Zero Shear Viscosity of Poly (Vinyl Chloride) Plastisols, Appl. Rheol. 16 (2006) 136.

We present a simple methodology for extending linear viscoelastic measurements of crystallizing polymers tothe high-frequency regime, where usually crystallization kinetics represents an obstacle. The idea is to performrapid quenches, below the melting temperature (which corresponds to the high-frequency region), account forthe thermal equilibration and the very slow early stages of crystallization, and perform the measurements beforereally crystallization sets in, in the 'quasi-equilibrium' state. Albeit tedious, when properly done, this methodworks remarkably well, as demonstrated for a particular polybutadiene mixture, and opens the route for obtain-ing rheological master curves in a wide variety of crystallizing polymers.

Cite this publication as follows:
Kapnistos M, Vlassopoulos D: Rheological Master Curves of Crystallizing Polymer Mixtures, Appl. Rheol. 16 (2006) 132.

This paper attempts to investigate the problem for the interaction between a screw dislocation and a piezoelectric circular inhomogeneity with interface cracks in viscoelastic matrix. Utilizing the laplace transform method, we find that the viscoelastic problem is first reduced to an associated elastic one. After solving the associated elastic problem through complex function method, the solution of viscoelastic problem is obtained by using the inverse laplace transformation. The viscoelasticity of material is modeled by the combination of spring and dashpot. Particularly, the boundary value problem for standard linear solid model is solved analytically. The analytical results show that the force acting on the dislocation depends on the piezoelectric properties of inhomogeneity and interfacial crack, and the magnitude of the force evolves toward a constant value as time elapses. However, the viscoelasticity of material cannot alter the equilibrium position of the dislocation. Results presented in this paper are in agreement with the previous solution as special cases.

Cite this publication as follows:
Liu Y, Li B, Fang Q: Interaction Between a Screw Dislocation and a Piezoelectric Circular Inhomogeneity with Interfacial Cracks in Viscoelastic Matrix, Appl. Rheol. 16 (2006) 102.

The purpose of this paper was to re-evaluate the novel rheological method of Crosby et al. [J. Rheol. 46 (2002) 401] to characterise long chain branching (LCB) in polyethylenes (PE) using the rheology of concentrated solutions. The feasibility of this dilution method centred on knowing the class of branched material and the molecular tube theory-based technique for the determination of two topological parameters (n, bU), where n is the number of entanglements between branch points while bU is the probability of meeting a branch point when tracing along the molecule from a random monomer against the direction of polymerisation. This paper proposes new possible approaches to calculate the two topological parameters (n, bU) set for metallocene polyethylenes (mPE), and their ambiguity discussed, as the results are dependent on the approach taken, though the previous authors mentioned only one. In addition, their approach requires an input value of LCB/1000C obtained from the standard analytical solution (SEC-V or SEC-laLLS) methods, hence, until now, without proper demonstration of the potential advantage of the dilution rheology method for LCB characterisation, as the main premise of their published article was to characterise the degree of LCB via rheological measurements without recourse to other methods of LCB characterisation.

Cite this publication as follows:
Chai CK, Ang SC: An Evaluation of Dilution Rheology for the Characterization of Long Chain Branching of Polyethylenes, Appl. Rheol. 16 (2006) 90.

This paper is concerned with a fuzzy model developed for describing the rheological properties of lime pastes and mortars. We have identified the physical parameters on which the flow properties of these materials depend, and whose complex interrelationships make it difficult to model the phenomena using a traditional approach. The basic notions of fuzzy modelling are described, a technique which enables different kinds of variables and other knowledge elements to be handled in a formal context that can be easily computerized. Applying the Fuzzy Approximation Theorem we can develop a model irrespective of whether the correlation functions are expressed in explicit analytical form or not. The definitions of the fuzzy sets for the different variables are provided which, together with IF/THEN rules comprise the knowledge base of the model. The model is then applied to determine the plasticity of lime pastes and consistency of lime-based mortars using ordinary fuzzy inference mechanisms.

Cite this publication as follows:
Atzeni C, Sanna U, Spanu N: A Rheological Fuzzy Model for Lime Plasticity and Mortar Consistency, Appl. Rheol. 16 (2006) 80.

Of the torsional drag-flow experiments, the hands-down winner for simplicity and ease of use is that using parallel- plate fixtures. This geometry is highly flexible, allowing custom modification of plate size and material, and is easily adaptable for optical use and the application of electric fields. However, its nonuniform flow is a major encumbrance for measuring nonlinear response. In 1987, Cross and Kaye offered a simple and clever solution for this problem, which essentially states that one assumes the sample is Newtonian, but the shear rate assigned to the observed ''Newtonian'' viscosity is 3/4ths of the rim shear rate . This shift factor arises from the use of Gaussian integration over radius of the nonlinear stress profile. Recent re-examination of the Cross-Kaye rule indicates that there may be a more accurate rule of thumb with the shift factor being 0.8 instead of 0.75 (4/5 instead of 3/4). However, for complex materials, the real question is how much useful information is covered up by this approach vs. the traditional differentiation of the integral to account for the stress profile. We have attempted to answer this question using a selection of nonlinear measurements on an AB block copolymer solution that is rheologically complex.

Cite this publication as follows:
Shaw MT, Liu ZZ: Single-point Determination of Nonlinear Rheological Data from Parallel-Plate Torsional Flow, Appl. Rheol. 16 (2006) 70.

Rheological properties of food fluids are useful for quality control, texture evaluation, and food structure determination. The rheological behavior is dependent on the size, form and concentration of solids in suspension and the system structure. Star fruit (Averrhoa carambola L.) pulp was obtained from the crude fruit and treated enzymatically, pasteurized and homogenized at 11000 rpm for 2 min and 22000 rpm for 5 min. The pulp presented Newtonian characteristics with R2 values greater than 0.98. Enzymatic treatment under 55 C for 1 h reduced the crude pulp viscosity from 1.84 to 1.22 mPa.s. Pasteurization under 100 C for 10 min increased the viscosity at around 26% in relation to the crude pulp, resulting in a turbid and homogeneous product. To evaluate the influence of the insoluble solids, filtration or concentration to 50% from the initial volume were carried out using laboratory procedures. Filtration of the pasteurized pulp promoted a viscosity decrease of 60% while concentration increased the viscosity from 2.28 to 7.98 mPa.s

Cite this publication as follows:
Vendrusculo AT, Hotza D, Gomes CM, Quadri MGN: Rheology of Star Fruit Pulp (Averrhoa Carambola L.), Appl. Rheol. 16 (2006) 26.

Conventional methods often impose difficulties when measuring the viscosity of fluids containing particles or fibres, e.g. tomato paste or fruit preparations, mainly due to the narrow gaps of the viscometer. In order to solve these problems different geometries have been developed, e.g. different mixer systems and wide gap double concentric cylinders. However, these can not be evaluated assuming a constant shear rate throughout the fluid. In this study, three different kinds of mixer systems have been studied; a small and a large paddle and a helix. For the mixer systems an average shear rate must be determined and a quotient between torque and shear stress must be found. In addition, a wide gap double concentric cylinder (DCC) was examined and evaluated using two different methods. When evaluating the mixer systems a method based on the Couette analogy has been used successfully for a number of complex fluids, including prepared sauces and fruit samples containing particles of different size. The DCC has been evaluated using a numerical as well as an approximate method, both giving results of good accuracy. All systems had the limitation that no consistent results were obtained for tomato paste. However, when starch was added to the diluted tomato paste dispersion, satisfying results were once again obtained.

Cite this publication as follows:
Roos H, Bolmstedt U, Axelsson A: Evaluation of New Methods and Measuring Systems for Characterisation of Flow Behaviour of Complex Foods, Appl. Rheol. 16 (2006) 19.

The yielding behavior of two model electrorheological suspensions of uncoated silica particles and silica coated with polyaniline base in silicone oil using controlled shear rate and controlled shear stress experiments has been analyzed. The results demonstrate that unlike the uncertain dynamic yield stress values estimated from the results obtained in the former mode by extrapolation of the unsteady shear stresses to zero shear rate, the controlled shear stress measurement permits to detect sensitively the region starting from the initial rupture of particle chain structure in the electric field at rest corresponding to a static yield stress and ending in total breakage of suspension structure at a breaking stress. The latter quantity can be detected with a good accuracy and proved to be a reliable criterion of the stiffness of electrorheological (ER) structure.

Cite this publication as follows:
Pavlinek V, Saha P, Perez-Gonzalez J, DeVargas L, Stejskal J, Quadrat O: Analysis of the Yielding Behavior of Electrorheological Suspensions by Controlled Shear Stress Experiments, Appl. Rheol. 16 (2006) 14.

The main aim of the work is to study the physicochemical and rheological behaviour of agar gel extracted from a red seaweed Gelidiella acerosa collected from various locations and seasons in southeast coast and west coast of India. The thesis also deals with the rheological studies of agar gels in presence of various additives including surfactants and fatty acids as well as agar and carrageenan based film-forming dispersions. The observed shear viscosity values were correlated with existing rheological models. It was observed from the shear viscosity studies that agar gel become more gel thinning in presence of non ionic surfactants as well as in presence of fatty acids. Oscillation sweep measurements revealed that the agar gel become liquid like in presence of nonionic surfactants and opposite is true in presence of ionic surfactants. The film forming dispersions prepared from agar and plasticizers had inferior rheological behaviour in comparison to k-carrageenan based thin film forming dispersions. All the agar gel samples collected from various locations displayed different rheological behaviours.

Cite this publication as follows:
Prasad K: Chemical and Rheological Studies on Seaweed Polysaccharides (PhD Thesis), Appl. Rheol. 16 (2006) 32.

Cite this publication as follows:
Boek ES, Padding JT: CECAM Workshop on Structure and Rheology of Self-Assembling and Aggregating Colloidal Suspensions: Theory, Simulation and Experiment, Appl. Rheol. 16 (2006) 35.

Cite this publication as follows:
Fischer P: Physics of Continuous Matter - Exotic and Everyday Phenomena in the Macroscopic World (B. Lautrup), Appl. Rheol. 15 (2005) 369.

The Impact Factor of a journal is a quantitative way of assessing its worth and relevance to the academic community it serves. Many librarians see the ratio between Impact Factor and price as a suitable yardstick by which to measure the value of their collections. In addition, the research assessment exercises which, in many countries, are now being carried out on a more formal basis mean that authors submitting original research must publish it in a journal with the highest perceived worth possible in order to secure future funding, job promotions and peer recognition. It has been suspected [T. Opthof, Cardiovasc. Res. 33 (1997) 1; J. Stegmann, Nature 390 (1990) 550], however, that a particular author's impact is not much related to the journals in which her/he publishes. As will be demonstrated in this letter, the impact of articles published in rheological journals is largely influenced by criteria such as length of article, number of authors, number of cited references.

Cite this publication as follows:
Kroger M: Publication Specific Impact of Articles Published by Rheological Journals, Appl. Rheol. 15 (2005) 406.

Blood flow rheology is a complex phenomenon. Presently there is no universally agreed upon model to represent the viscous property of blood. However, under the general classification of non-Newtonian models that simulate blood behavior to different degrees of accuracy, there are many variants. The power law, Casson and Carreau models are popular non-Newtonian models and affect hemodynamics quantities under many conditions. In this study, the finite volume method is used to investigate hemodynamics predictions of each of the models. To implement the finite volume method, the computational fluid dynamics software Fluent 6.1 is used. In this numerical study the different hemorheological models are found to predict different results of hemodynamics variables which are known to impact the genesis of atherosclerosis and formation of thrombosis. The axial velocity magnitude percentage difference of up to 2 % and radial velocity difference up to 90 % is found at different sections of the T-junction geometry. The size of flow recirculation zones and their associated separation and reattachment point's locations differ for each model. The wall shear stress also experiences up to 12 % shift in the main tube. A velocity magnitude distribution of the grid cells shows that the Newtonian model is close dynamically to the Casson model while the power law model resembles the Carreau model.

Cite this publication as follows:
Shibeshi SS, Collins WE: The Rheology of Blood Flow in a Branched Arterial System, Appl. Rheol. 15 (2005) 398.

We report on the design and implementation of an evaporation blocker for cone-plate and plate-plate geometries. In addition to minimizing sample evaporation by trapping the saturated vapor inside a sample chamber, an important feature of the evaporation blocker is the suppression of solvent transport through condensation. Validation tests with DI-water, hydrogels, and colloidal suspensions demonstrate that the new accessory reduces solvent evaporation significantly more than commercially available environmental control chambers. Experiments were also performed to show that the evaporation blocker enables a variety of experiments on thermoresponsive complex fluids that were previously impossible, and provide new insight into the molecular organization of these materials. The evaporation blocker was specifically designed for an Anton Paar MCR rheometer, but the fundamental principles are widely applicable.

Cite this publication as follows:
Sato J, Breedveld V: Evaporation Blocker for Cone-Plate Rheometry of Volatile Samples, Appl. Rheol. 15 (2005) 390.

We present a one-parameter model that fits quantitatively the mean velocity profiles from experiments and numerical simulations of drag-reduced wall-bounded flows of dilute solutions of polymers and non-Brownian fibers in the low and modest drag reduction regime. The model is based on a viscous mechanism of drag reduction, in which either extended polymers or non-Brownian fibers increase the extensional viscosity of the fluid and thereby suppress both small and large turbulent eddies and reduce momentum transfer to the wall, resulting in drag reduction. Our model provides a rheological interpretation of the upward parallel shift S+ in the mean velocity profile upon addition of polymer, observed by Virk. We show that Virk's correlations for the dependence on polymer molecular weight and concentration of the onset wall shear stress and slope increment on the Prandtl-Karman plot can be translated to two dimensionless numbers, namely an onset Weissenberg number and an asymptotic Trouton ratio of maximum extensional viscosity to zero-shear viscosity. We believe that our model, while simple, captures the essential features of drag reduction that are universal to flexible polymers and fibers, and, unlike the Virk phenomenology, can easily be extended to flows with inhomogeneous polymer or fiber concentration fields.

Cite this publication as follows:
Roy A, Larson RG: A Mean Flow Model for Polymer and Fiber Turbulent Drag Reduction, Appl. Rheol. 15 (2005) 370.

The rheological behaviour of a cement paste used in Self-Compacting Concretes (SCC) formulations is compared to that of an 'ordinary' cement paste (OC) devoid of organic admixtures. In order to mimic the flow conditions experienced by the cement paste in the inter granular space of concretes, the rheological behaviour is investigated in a squeeze flow geometry. By considering the evolution of the squeeze force for different velocities as a function of the instantaneous distance between the discs, it is found that the behaviors of the two cement pastes are qualitatively different. For the OC pastes, the force decreases with increasing squeeze velocity for any given discs separation, indicating that the material is undergoing fluid-solid separation due to filtration of the fluid phase through the porous media made up by the grains. Such behaviour reflects the very poor flowability of the OC paste. The behaviour of the SCC paste is qualitatively different. Above a certain critical value of the speed Uc, the force is an increasing function of the speed for any given disc separation. Under these flow conditions the rheological behaviour of the material is that of a viscous, although highly non-Newtonian, fluid which corresponds to the flowability conditions of the material. For squeeze speeds smaller than Uc, the rheological behaviour of the SCC paste is similar that of OC, indicating that below this critical velocity the material undergoes solid-fluid separation corresponding then to its non-flowability zone.

Cite this publication as follows:
Phan,PH, Chaouche M: Rheology and stability of self-compacting concrete cement pastes, Appl. Rheol. 15 (2005) 336.

The propagation of ultrasonic waves in polymers depends on their viscoelastic behaviour and density, resulting significantly affected by phase transitions occurring with changing temperature and pressure or during chemical reactions. Therefore, the application of low intensity ultrasound, acting as a high frequency dynamic mechanical deformation applied to a polymer, can monitor the changes of viscoelastic properties associated with the glass transition, the crystallization, the physical or chemical gelation, the crosslinking. Thanks to the non-destructive character (due to the very small deformation amplitude), low intensity ultrasound can be successfully used for polymer characterization. Moreover, this technique has a big potential as a sensor for on-line and in-situ monitoring of production processes for polymers or polymer matrix composites. Recently, in the laboratory of Polymeric Materials of Lecce University a custom made ultrasonic set-up for the characterization of polymeric material, even at high temperatures, has been developed. The ultrasonic equipment is coupled with a rotational rheometer. Ultrasonic waves and shear oscillations at low frequency can be applied simultaneously on the sample, getting information on its viscoelastic behaviour over a wide frequency range. The aim of this paper is to present the potential and reliability of the ultrasonic equipment for the ultrasonic dynamic mechanical analysis (UDMA) of both thermosetting and thermoplastic polymers. Three applications of UDMA to different polymeric systems will be reviewed, concerning the cross-linking of a thermosetting resin, the crystallisation from melt of a semicrystalline polymer and the water sorption in a dry hydrogel film. From the ultrasonic velocity and attenuation measurements, the viscoelastic properties of the tested polymers are evaluated in terms of complex longitudinal modulus and compared with the results of conventional dynamic mechanical analysis, carried out at low frequency.

Cite this publication as follows:
Lionetto F, Montagna F, Maffezzoli A: Ultrasonic Dynamic Mechanical Analysis of Polymers, Appl. Rheol. 15 (2005) 326.

Polymer melts can be mixed with many monomers, plasticizers, antistatics or foaming additives. Properties of such mixtures can change during blending because of chemical reactions like polymerization or crosslinking. The process may be carried out either in stirred tanks, extruders or in motionless mixers. In this paper we focused on the mixing time and the diffusion time of reagent, plasticizer and polymer thanks to rheological tools, and on the way how rheological properties can be studied during chemical reaction in polymer blending. The concept of rheoreactor and Couette analogy were introduced since we have a reactor on our disposal that can mix solution and measure rheological properties without taking sample. This apparatus appears to be an appreciable tool in complement of internal mixers that are specific to polymer blending. For example, we show the importance of the competition between mixing time and reaction time for reactive systems.

Cite this publication as follows:
Lacoste C, Choplin L, Cassagnau P, Michel A: Rheology Innovation in the Study of Mixing Conditions of Polymer Blends during Chemical Reaction, Appl. Rheol. 15 (2005) 314.

Cite this publication as follows:
Richtering W: Fundamentals of Interface and Colloid Science: Volume IV: Particulate Colloids and Volume V: Soft Colloids (J. Lyklema), Appl. Rheol. 15 (2005) 310.

Cite this publication as follows:
Peters F: CECAM Workshop on Modeling and Simulation of Entangled Polymeric Liquids, Appl. Rheol. 15 (2005) 240.

Cite this publication as follows:
Stange J: Workshop Rheology and Processing of Polymers, Appl. Rheol. 15 (2005) 238.

The mechanical properties of the lamellar phase, la, of the system C_12 E_4/D_2O were studied along an isoplethal path (30 wt% C_12 E_4) in the temperature range 10 - 60 C. A dynamic analysis was determined by small strain oscillatory rheometry. The multilamellar vesicles (MLVs) (onions) were transformed by shearing the lamellar phase. The micellar phase was investigated by steady and dynamic rheological experiments. The micellar aggregate size increases slightly upon heating and the transition from micelles to lamellae appears to be a first order transition. The mechanical spectra of the lamellar phase show a strong dependence of the moduli on the frequency. This is typical of defective lamellar phases. They are different from MLVs mechanical spectra. The MLVs viscous and storage moduli are almost independent from the frequency and they exhibit the characteristics of a strong gel. The temperature of formation of the MLVs phase influences the mechanical properties of the MLVs. Three different packing states of the MLVs phase were observed in the temperature range 25 - 55 C.

Cite this publication as follows:
Coppola L, Nicotera I, Oliviero C: Dynamic Rheological Analysis of MLVs and Lamellar Phases in the System C_12 E_4/D_2O, Appl. Rheol. 15 (2005) 230.

The correlation between the Bostwick degree and the static rheological properties of yield stress food fuids is first revisited and then reformulated in this work. The role of the yield stress in the free surface flow of the Bostwick test is studied using dimensional analysis. Results from experiments on 48 different samples of yield stress fluids are considered and included to check the adequacy of the proposed correlation. Asymptotic dynamic behaviour is also presented and discussed as a mechanism of complete self similarity with respect of the dimensionless time. This approach would seem to support the opinions in favor of the yield stress as a key parameter, and thus offers an interesting new viewpoint useful to both future experiments on the Bostwick test and studies of 'dam-break' like dynamics.

Cite this publication as follows:
Perona P: Bostwick Degree and Rheological Properties: an Up-to-date Viewpoint, Appl. Rheol. 15 (2005) 218.

Oxide ceramic masses are used for catalysts and catalyst carriers. For a reliable processing hydrocolloids (e. g. cellulose) are usually added in order to decelerate demixing phenomena. Oxide ceramic masses react to simple shearing with hardening (peptisation: increase of the shear stress with the shear deformation) [1]. The present study analyses, if an ultrasonic treatment has also an impact on the structure, the shelf-life (in the green state), the correlated flow behaviour of oxide ceramic masses and presumably (not tested) the mechanical properties in the hardened, sintered state. The idea of using ultrasonic treatment is to change the microstructure (see below) and, therefore, to minimise or even give up the standard addition of stabilizers to minimize demixing in aqueous oxide ceramic suspensions. Besides the additional costs of an extra process unit, stabilisers cause often deteriorated mechanical properties (porosity, crack behaviour) of the ceramics in the hardened state after the sintering. Therefore, pump experiments (apparent viscosity), oscillatory (G´ and G´´) and steady shear experiments (h), particle-size analysis (particle-size distribution, agglomerate strength), light microscopy, decanting experiments and pH-determinations have been performed. The obtained results show, that the hardening of the apparent viscosity (derived from the flow) during pump experiments with simultaneous ultrasonic treatment in a flow cell is combined with an increase of the fine fraction, the formation of enlarged, but smoother agglomerates, the change of the pH-value and the evolution of a three-dimensional network (gelling). All these processes increase both the amount of bound/immobilised (chemically or physically bound by or onto the solidsurfaces) and of retained water (interior of agglomerates and/or the pores of the flowand ultrasonic-induced network). This means that the volume fraction of the rheologically "free" water decreases and simultaneously the effective solid volume fraction increases. With respect to the concept of the rheologically effective solid fraction this is combined with an increasing viscosity. At the same time the tendency of demixing decreases significantly. Thus, by an appropriate combination of shear flow and ultrasonic treatment, the aqueous oxide ceramic suspensions are stabilised and a reliable processing of the initially problematic solid/fluid mixtures can be realised without stabilisers (eluding their negative consequences with respect to the quality of the sintered state).

Cite this publication as follows:
Gotz J, Rewese L, Walch M, Geissler A: Influence of an Ultrasonic Treatment on the Structure and Flow Behaviour of Oxide Ceramic Masses, Appl. Rheol. 15 (2005) 204.

Cite this publication as follows:
Schweizer T: Polymer Viscoelasticity (Yn-Hwang Lin), Appl. Rheol. 15 (2005) 202.

The effect of high ac electric fields upon a liquid crystalline polymer solution, poly(n-hexyl isocyanate) in p-xylene, is examined. The results show that the solutions exhibit an increase in rheological properties proportional to the strength of the field at concentrations well below those exhibiting liquid crystalline behavior. The effects of frequency and field strength are examined as a means to explain this previously unreported phenomenon.

Cite this publication as follows:
Menna TJ, Filisko FE, Lynch RA: Effect of Electric Fields on the Rheological Properties of the Isotropic Phase of phic/p-Xylene Solutions, Appl. Rheol. 15 (2005) 172.

Exponential integral functions were fitted to relaxation data obtained from tensile and shear loading of an asphalt-sand mixture at different temperatures. This approach yields a better fit to the experimental data than the traditional Prony series and provides physical insight into essential characteristics of the relaxation processes that govern the asphalt-sand mixture. We expect that using this model beyond the time range covered by the experimental data would result in a significantly better representation of the material behavior than would extrapolation of the Prony series fit.

Cite this publication as follows:
Koenigsberg W, Selverian JH: Zone Method for Representing Relaxation Characteristics of Viscoelastic Materials, Appl. Rheol. 15 (2005) 160.

A new model for mean velocity profile of turbulent water flow with added drag-reducing surfactants is presented in this paper. The general problem of drag due to frictional resistance is reviewed and drag reduction by the addition of polymers or surfactants is introduced. The model bases on modified Prandtl's mixing length hypothesis and includes three parameters, which depend on additives and can be evaluated by numerical simulation from experimental datasets. The advantage of the model in comparison with previously reported models is that it gives uniform curve for whole pipe section and can be determined for a new surfactant with less necessary measurements. The use of the model is demonstrated for surfactant Habon-G as an example.

Cite this publication as follows:
Krope A, Krope J, Lipus LC: A Model for Velocity Profile in Turbulent Boundary Layer with Drag Reducing Surfactants, Appl. Rheol. 15 (2005) 152.

Cite this publication as follows:
Fischer P: Viscosimetry of Polymers and Polyelectrolytes (W.-M. Kulicke, C. Clasen), Appl. Rheol. 15 (2005) 151.

Magnetorheological fluids (MRFs) show a high but reversible rise of the viscosity upon application of an external magnetic field. This effect can be utilized in controllable friction dampers where the MR fluid flows through a gap with a adjustable magnetic field. The change in the magnitude of the magnetic field leads to a change of the viscosity of the fluid which in turn effects the pressure drop in the system. So the damping force can be controlled by the magnitude of the external magnetic field. This energy dissipation leads to a rise of the damper temperature. For designing those dampers it is vital to know the influence of the geometry, which influences the magnetic field strength, as well as the flow properties and the temperature dependence of the magnetorheological effect. An approach to the solution of this problem is shown by using an Arrhenius relationship, where the fluid viscosity is a function of the shear rate, the magnetic field and the temperature. The aim of the here presented research is to show how the fluid behavior can be simply modeled for use in CFD codes to design dampers or other applications.

Cite this publication as follows:
Zschunke F, Rivas R, Brunn PO: Temperature Behavior of Magnetorheological Fluids, Appl. Rheol. 15 (2005) 116.

The calibration of the temperature control unit of a rotational rheometer with a hood oven is shown. The calibration technique shown for a Paar-Physica rheometer can be adapted to any rheometer with hood oven (indirect heating). The temperature of the bottom fixed plate and the air bearing suspended cone or plate are measured independently. By keeping the amount of venting gas constant, the set temperature of the hood oven is adjusted to reach a minimum gradient across the measuring gap. The calibration procedure is optimized to keep the oven as close as possible to the measuring position.

Cite this publication as follows:
Schweizer T: Temperature Calibration of Rotational Rheometers with Electrically Heated Tools and Hood Oven, Appl. Rheol. 15 (2005) 112.

In order to characterise the structure and flow behaviour of model chocolate systems Nuclear Magnetic Resonance (NMR) and rheometry were used to determine the T1 - and T2 - NMR relaxation times and their corresponding flow functions. T1 and T2 characterise the molecular mobility of fluids and correlate with both the zeroshear- rate and infinity viscosity of various chocolate model systems (determined with rotational rheometry and capillary rheometry). Based on this correlation, NMR provides the possibility to determine characteristic viscosities of chocolate masses by means of NMR-relaxation experiments. The viscosities of chocolate masses are important process parameters, as they are used for quality control of the production process. An online process viscosimetry via T2 relaxation would allow the installation of an efficient process control and, thus, a process automation. This NMR application with comparatively short measuring times is especially interesting for disperse systems where the use of conventional rheometric techniques may cause large errors. The only prerequisite for the measurement of the viscosities using NMR is a previous calibration. This was performed with the help of rotational and capillary rheometry. The NMR self-diffusion experiments are especially appropriate to characterise the influence of emulsifiers on the structure and the flow behaviour of chocolate masses.

Cite this publication as follows:
Gotz J, Balzer H, Hinrichs R: Characterisation of the Structure and Flow Behaviour of Model Chocolate Systems by Means of NMR and Rheology, Appl. Rheol. 15 (2005) 98.

There is often a need to perform rheological tests on dilute polymeric liquids at a time long after their initial preparation, for example if a more sensitive or novel method of measuring a material property (such as uniaxial/ biaxial extensional viscosity or second normal-stress differences) becomes available. An inexpensive method of storing such fluids which prevents any form of deterioration (e.g. bacteriological) would therefore be of great value. This study explores the potential of freezing as that storage process by investigating whether the freezethaw process itself leads to rheological changes. The rheological properties of three polymeric liquids: 0.25 % xanthan gum, 0.125% polyacrylamide and a 0.1 %/0.1 % carboxymethylcellulose / xanthan gum blend commonly used in non-Newtonian fluid flow studies were determined in both shear and oscillation before and after a freeze-thaw process. Within the uncertainty of the rheometer used, the rheological properties of the polymers studied were found to be unaffected by the freeze-thaw process leading to the conclusion that this storage method is indeed a practical possibility.

Cite this publication as follows:
Escudier MP, Clement-Evans J, Poole RJ: Freezing as a Storage Process for Aqueous Polymer Solutions, Appl. Rheol. 15 (2005) 90.

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Rheological Societies, Petrie CJS, Mielke W, Coussot P, Kissi NE, Fischer P, Mavrantzas VG, Grizzuti N, Jarvela P, Wanger MH: Society's Site Mar 2005 - Aug 2005 , Appl. Rheol. 15 (2005) 59.

Viscosity measurements of a suspension of cornstarch in silicone oil, at several concentrations and subject to different electrical field strengths, were conducted. An increase in the apparent viscosity, in correlation with the field strength, which is characteristic of the so-called electrorheological fluids (ERF), was observed. For a given field intensity, the value of the viscosity increases rapidly in the first seconds after the application of the electric field, and then it increases slowly until it finally approaches a saturation value. This behaviour of the apparent viscosity has been related to the microstructure formation due to interactions between dipoles induced by the electric field. Characteristic times, related to structure formation after application of an electric field, are investigated by means of diffuse light transmission and speckle-pattern activity measurements. Two characteristic times were found that should be related to the state of aggregation of the suspended particles: orientation of the non-isotropic particles and later chain formation. These results agree reasonably with that obtained from electrorheological measurements. Microscopic observations of structure formation are also reported.

Cite this publication as follows:
Alanis E, Romero G, Martinez C, Alvarez L, Mechetti C: Characteristic Times of Microstructure Formation in Electrorheological Fluids determined by Viscosity and Speckle Activity Measurements, Appl. Rheol. 15 (2005) 38.

Commercially available, blended methylhydroxyethyl celluloses with similar weight-average molar masses but varying molar mass distributions were characterized by different techniques like steady shear flow and uniaxial elongation in capillary breakup experiments. The determined relaxation times t were then correlated with the absolute molar mass distribution acquired via SEC/MALLS/DRI (combined methods of size-exclusion-chromatography, multi angle laser light scattering and differential refractometer). In order to describe the longest relaxation time of the polymers in uniaxial elongation via integral mean values of the molar mass distribution, defined blends of polystyrene standards with varying molar mass distributions were characterized. The obtained data was scaled via different moments of the molecular weight distribution and could be correlated with the results obtained for the methylhydroxyethyl celluloses.

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Plog JP, Kulicke W-M, Clasen C: Influence of the Molar Mass Distribution on the Elongational Behaviour of Polymer Solutions in Capillary Breakup, Appl. Rheol. 15 (2005) 28.

We investigate the dynamics of the capillary thinning and break-up process for low viscosity elastic fluids such as dilute polymer solutions. Standard measurements of the evolution of the midpoint diameter of the necking fluid filament are augmented by high speed digital video images of the break up dynamics. We show that the successful operation of a capillary thinning device is governed by three important time scales (which characterize the relative importance of inertial, viscous and elastic processes), and also by two important length scales (which specify the initial sample size and the total stretch imposed on the sample). By optimizing the ranges of these geometric parameters, we are able to measure characteristic time scales for tensile stress growth as small as 1 millisecond for a number of model dilute and semi-dilute solutions of polyethylene oxide (PEO) in water and glycerol. If the final aspect ratio of the sample is too small, or the total axial stretch is too great, measurements are limited, respectively, by inertial oscillations of the liquid bridge or by the development of the well-known beads-on-a-string morphology which disrupt the formation of a uniform necking filament. By considering the magnitudes of the natural time scales associated with viscous flow, elastic stress growth and inertial oscillations it is possible to construct an .operability diagram. characterizing successful operation of a capillary breakup extensional rheometer. For Newtonian fluids, viscosities greater than approximately 70 mPas are required; however for dilute solutions of high molecular weight polymer, the minimum viscosity is substantially lower due to the additional elastic stresses arising from molecular extension. For PEO of molecular weight 2 · 106 g/mol, it is possible to measure relaxation times of order 1 ms in dilute polymer solutions with zero-shear-rate viscosities on the order of 2 . 10 mPas.

Cite this publication as follows:
Rodd LE, Scott TP, Cooper-White JJ, McKinley GH: Capillary Break-up Rheometry of Low-Viscosity Elastic Fluids, Appl. Rheol. 15 (2005) 12.

Cite this publication as follows:
Schweizer T: Handbook of Ellipsometry (Harland G. Tompkins, Eugene A. Irene, Eds.), Appl. Rheol. 15 (2005) 10.

Cite this publication as follows:
Truscott J: 4th Conference on Modelling and Simulation in Medicine, Appl. Rheol. 14 (2004) 327.

The behaviour of reverse micellar solution and reverse hexagonal and lamellar liquid crystal phases in pluronic L64/water/p-xylene ternary system was investigated by rheological techniques. Samples with an increasing water content along the amphiphilic copolymer-lean side of the ternary phase diagram were analysed at different temperatures and a different behaviour was evidenced by both dynamic and steady tests for each considered phase, depending on the morphology of structure (micellar, lamellar, hexagonal phases). It was observed that the reverse micelles size increases with increasing water concentration and decreases with increasing temperature, without any phase transition. On the contrary the normal micelles become anisometric on temperature, showing a transition to a liquid crystalline phase. The observed mechanical spectra of the liquid crystalline phases are typical of hexagonal and lamellar phases according to the literature. A phase transition with temperature was found for both liquid crystalline phase (lamellar and hexagonal) by rheological tests and was confirmed by ocular inspection.

Cite this publication as follows:
Coppola L, Gabriele D, Nicotera I, Oliviero C: Rheological Properties of the Reverse Mesophases of the Pluronic L64/P-Xylene/Water System, Appl. Rheol. 14 (2004) 315.

The term |G*|/(1-(1/tand sind)) has been suggested as one of the best candidates for the replacement of the Superpave specification parameter |G*|/sind, which has been found to be inadequate in rating polymer-modified binders for high temperature performance grading. This refinement of the Superpave specification parameter evolved through a theoretical derivation based on fundamental concepts. It was shown to be more sensitive to the variations in the phase angle d than the original Superpave specification parameter. It thus described the unrecovered strain in the asphalt binders more accurately, and hence related to actual field performance data. This article provides a comprehensive treatise of the parameter |G*|/(1-(1/tand sind)) giving details of its derivation, salient features that are attributed to its success, comparison with actual field performance data for validation and a one-on-one comparison with the existing parameter |G*|/sind. It is shown that for all available field data, the parameter |G*|/(1-(1/tand sind)) does a better job in correlating with the rutting behavior than the parameter |G*|/sind for unmodified as well as modified asphalts. Since it is obtained in the same manner as the parameter |G*|/sind through the determination of |G*| and d from a stress-controlled or strain-controlled dynamic shear rheometer, it means that no retraining of technicians and staff is required and implementation for the use of this parameter is immediate, thereby saving enormous amount of time and money. This parameter has the further advantage of being in a form easily adaptable to modeling, and thereby directly applicable for pavement design purposes.

Cite this publication as follows:
Shenoy A: A Comprehensive Treatise of the High Temperature Specification Parameter |G*|/(1-(1/tan d sin d)) for Performance Grading of Asphalts, Appl. Rheol. 14 (2004) 303.

A viscosity function for highly-shear-thinning or yield-stress liquids such as pastes and slurries is proposed. This function is continuous and presents a low shear-rate viscosity plateau, followed by a sharp viscosity drop at a threshold shear stress value (yield stress), and a subsequent power-law region. The equation was fitted to data for Carbopol aqueous solutions at two different concentrations, a drilling fluid, an water/oil emulsion, a commercial mayonnaise, and a paper coating formulation. The quality of the fittings was generally good.

Cite this publication as follows:
Mendes PRS, Dutra ESS: Viscosity Function for Yield-Stress Liquids, Appl. Rheol. 14 (2004) 296.

Particle fluid separation is studied in the case of slow squeezing flow of dense clay suspensions. The fluid pressure gradient generated by the test induces heterogeneity in the sample. Experimental water content measurements at different time points through the test allow the quantification of this separation phenomenon. The problem equations are written in the case of purely extensional flow. Based on Terzaghi principle, Darcy.s law and a Cam Clay type constitutive equation, the influence of the permeability function on the predicted void ratio evolution is studied. It is then shown that a certain water amount is strongly linked to the grains and cannot be extracted from the sample using simple compression. This critical water amount is then taken in account in the permeability function in order to predict the compression load through the test.

Cite this publication as follows:
Roussel N, Lanos C: Particle Fluid Separation in Shear Flow of Dense Suspensions: Experimental Measurements on Squeezed Clay Pastes, Appl. Rheol. 14 (2004) 256.

The determination of flow curves and the apparent viscosity curves at 28°C of creams containing human leukocyte alpha interferon as active principle is presented in this paper. These creams are used for the treatment of papiloma virus and herpes simplex. It is demonstrated that their behaviour corresponds to a thixotropic fluid. The Herschel-Bulkley model parameters are presented and discussed as an indicator of the grade of thixotropy. Apparent viscosity plotted as a function of shear rate and storage time allows defining the time period in which the samples recover their initial structure. Additionally it was concluded that for determining the quality of the product, the acceptance limit of the viscosity should be specified for a given shear rate.

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Zumalacarregui L, Vazquez M, Estevez T, Aguilera A, Hardy E: Rheological Studies of Interferon Creams, Appl. Rheol. 14 (2004) 251.

An orifice flowmeter was used to measure the extensional viscosity of several non-pigmented fluids and paper coating colors containing calcium carbonate as pigment in the context of a jet coating application. The orifice flowmeter was first calibrated in terms of a dimensionless Euler number versus Reynolds number curve with Newtonian fluids. The calibration curve was then used to determine the apparent extensional viscosity of coating colors. In the strain rate range investigated, all the fluids were found to exhibit strain-thinning and the Trouton ratio of the coating colors was in the range 5 to 20. Jet coating tests were also carried out in order to evaluate the effect of the extensional viscosity on the jet performance. The extensional viscosity was shown to be a key parameter determining the configuration of the downstream meniscus in the web contact region.

Cite this publication as follows:
Arzate A, Ascanio G, Carreau PJ, Tanguy PA: Extensional Viscosity of Coating Colors and its Relation With Jet Coating Performance, Appl. Rheol. 14 (2004) 240.

The performance of tests with elastic liquids at high shear rates is cumbersome due to viscous dissipation heating, high normal forces, and - above all - edge fracture. This paper shows how such measurements can be improved and simplified over the conventional cone-plate technique by using a partitioned plate. For a polystyrene melt with zero shear viscosity 44.5 kPas at 190.C, steady state viscosities can be obtained up to 100 s-1. For samples with twice the diameter of the sensing area of the tool, the strain beyond which disturbances can be noticed is about 2 - 3 times higher than for conventional cone-plate. As a consequence of the design, precise viscosity measurements can be made without knowing the exact radius of the sample and without well centring it. This geometry is ideal for quick and dirty loading. Drawbacks are that the tool requires regular cleaning of the ring gap, that it can only be fitted to rheometers with a non-displacing force measuring cell (force rebalance transducer), and that it is not suited to measure low viscous systems such as polymer solutions.

Cite this publication as follows:
Schweizer T: A Quick Guide to Better Viscosity Measurements of Highly Viscous Fluids, Appl. Rheol. 14 (2004) 197.

Rheological properties of xerographic liquid inks of different concentrations of solid particles have been tested. Generally we have found that viscosity decreases with increasing shear rate, i.e. the system is pseudoplastic as corresponds to the break down of aggregated particles by the applied shear. The viscosity of inks may vary in orders of magnitude depending on solids concentration, reaching up values of ~ 108 Pas for solids concentration of 40 wt%. The existence of a yield critical stress has been discussed and we estimate that it increases exponentially with solids concentration. We have looked for possible differences in the rheological behavior of ink samples obtained either diluting more concentrated inks or drying less concentrated ones. Concentration and dilution of xerographic inks do not change their rheological properties meaning that the microscopic structure of the concentrated dispersion is broken (when diluting) and recovered (when drying) reversibly. On the other hand processed ink (previously subjected to high mechanical and electrostatic stresses) behaves differently than non-processed ink. The properties of processed inks are not totally recovered when diluting, manifesting itself in a higher effective apparent viscosity. This result should be of main concern to liquid ink based printing technologies, for which elimination of waste by recycling processed ink is a major goal.

Cite this publication as follows:
Valverde JM, Perez AT, Castellanos A, Viturro RE: Rheological Testing of Xerographic Liquid Inks: A Need for Printing Technology, Appl. Rheol. 14 (2004) 190.

Frequency sweep experiments were performed on poly(vinyl chloride) (PVC) and acrylonitrile butadiene rubber (NBR) as well as their miscible blends PVC/NBR (70/30), PVC/NBR (50/50), and PVC/NBR (30/70) in oscillatory shear. The samples were prepared by mechanical blending at 160.C. In order to investigate the validity of time temperature superposition (TTS) principle the loss angle d versus the logarithm of the absolute value of the complex modulus, G*, were plotted. It was shown that the TTS principle is not valid for the above-mentioned polymer materials and therefore they are not thermorheologically simple. Master curves of PVC, NBR, and PVC/NBR (50/50) blend were therefore obtained approximately. Using a nonlinear regression method, discrete relaxation spectra were determined for PVC, NBR, and PVC/NBR (50/50). To study non-linear viscoelasticity behavior, the experiments of steady shear, start up steady shear, and step strain were carried out. The damping function was determined by the step strain experiments. Using K-BKZ constitutive equation, the shear viscosity and the shear stress growth function were calculated from the discrete relaxation spectra and the damping function and then compared to experimental data. The K-BKZ constitutive equation provides very good prediction over the entire range of experimental results.

Cite this publication as follows:
Sodeifian G, Haghtalab A: Discrete Relaxation Spectrum and K-BKZ Constitutive Equation for PVC, NBR and Their Blends, Appl. Rheol. 14 (2004) 180.

Cite this publication as follows:
Kroger M: Ferrofluids: Magnetically Controllable Fluids and Their Applications (Stefan Odenbach), Appl. Rheol. 14 (2004) 178.

A detailed analysis of the dynamic flow properties of chitosan in solution at different temperatures (25 - 45 C), chitosan concentration (0.5% - 2.0%), solvent type (acetic, lactic, and hydrochloric acid), and ionic strength (0 and 0.2M NaCl) has been undertaken. The storage modulus, G', loss modulus, G'' and complex viscosity, h* have been determined over a wide range of frequencies and the results are presented using master curves. For the conditions studied, at low frequencies chitosan solutions show a constant complex viscosity which decreases as frequency increases. Likewise, storage modulus, G' and loss modulus, G'' increase as frequency increases with G'' being always greater than G' indicating that viscous effects are more important than elastic effects. For modelling the oscillatory-shear results we used the generalized Maxwell model. Two empirical equations were used to correlate the data: Cox-Merz rule for viscosity and laun's rule for primary normal stress difference. Both relations were found to represent our data for the experimental conditions studied.

Cite this publication as follows:
Martinez-Ruvalcaba A, Chornet E, Rodrigue D: Dynamic rheological properties of concentrated Chitosan solutions, Appl. Rheol. 14 (2004) 140.

The steady and dynamic shear viscosity of fish muscle protein paste obtained from Alaska pollock surimi at 95%, 90%, 85%, 80%, and 75% of moisture contents were measured in the temperature range of 5°C to 20°C. To estimate the steady shear viscosity at high shear rate from dynamic shear viscosity, the modified Cox-Merz rule was applied by introducing a frequency shift factor. The concentration dependence of zero-shear viscosity showed power-law dependence with an exponent of 3.5, and the universal behavior of viscosity at different protein concentrations was observed by a introducing reduced variables. The Carreau model was applied to describe the shear- thinning behavior of the surimi paste, and the model parameters estimated empirically showed moisture content dependence. The viscous flow behavior was independent of temperature (5°C to 20°C), and addition of starch decreased the flow index and viscosity of the paste, compared to the pure surimi paste.

Cite this publication as follows:
Yoon WB, Gunasekaran S, Park JW: Evaluating viscosity of Surimi paste at different moisture contents, Appl. Rheol. 14 (2004) 133.

The linear viscoelastic regions (L.V.R.) of suspensions of zirconium oxide particles were determined and characterized through the so-called 'critical parameters'. These are the values of shear-stress and strain at the crossover between the linear and the non-linear viscoelastic responses. From these magnitudes, the cohesive energy between the particles is calculated as a function of volume fraction of solids and at different electrolyte concentrations. The oscillatory measurements were carried out using a constant-stress rheometer at a fixed frequency of 1 Hz and increasing shear-stress. The suspensions cover a volume fraction range between 3% - 25% with electrolyte (sodium chloride) concentrations of 10-1 M, 10-2 M, 10-3 M and 10-5 M. Two different kinds of ZrO2 particles were used: commercially obtained -with no defined geometry- and spheres synthesized by us following the method described by Aiken, Hsu and Matijevic.

Cite this publication as follows:
Megias-Alguacil D: Characterization of the linear viscoelastic region in suspensions of zirconium oxide: Cohesive energy obtained from the critical parameters, Appl. Rheol. 14 (2004) 126.

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vonSeggern E: Lackeigenschaften messen und steuern (Meichsner, Mezger, Schröder), Appl. Rheol. 14 (2004) 104.

Changes in the rheological properties of hair shampoo samples differing in the content of Dead Sea (DS) salt were studied. The rheological properties were tested during a 28-day storage period at three different storage temperatures (cold, room temperature and accelerated conditions). Steady rheological tests were performed and the conductivities of the shampoo samples were determined. The parameters of the power law model; the consistency coefficient and the flow behavior index were used to quantify the effect of storage time and temperature on the rheological behavior of hair shampoo in the presence of DS salt. The consistency coefficient of the salt free shampoo samples stored at 8°C and at room temperature decreased with storage time, and the rheological behavior changed from shear thinning to Newtonian. On the other hand, the samples stored at 45°C exhibited a shear thinning behavior, which did not change with storage time. Shampoo samples with 1.5 wt% DS salt content, showed the maximum viscosity and the rheological behavior of the samples did not change with the storage time. An exception were the samples stored at 45°C, which behaved like the salt free samples stored at room temperature. The conductivity of hair shampoo increased linearly with storage time and salt concentration. A discontinuity at a salt concentration of 1.5% was observed. However, the conductivity of hair shampoo increased with increasing the storage temperature.

Cite this publication as follows:
Abu-Jdayil B, Mohameed H, Snobar T, Sa'id A: Rheology and Storage Tests of Dead Sea Shampoo, Appl. Rheol. 14 (2004) 96.

The answer to this provocative question is .no.! This is demonstrated by experiment and analysis for two very different materials . a highly concentrated emulsion and an 8%v/v Kaolin clay suspension. The flow curves of both materials clearly showed a low shear Newtonian asymptote and a pseudoplastic domain. The difference in the accuracy of the fitting equations relates mainly to the low shear rate domain. While the Cross equation is adequate over the full flow curve, the power law and the Herschel-Bulkley equations are clearly inadequate for the low shear rate range. These equations as well as the direct numerical method (using the Rabinowitsch- Weissenberg integral) were used for the calculation of the laminar pipe flow transport characteristics and the results were compared with experimental pipe flow data. It was shown that in all cases the maximum error did not exceed 5%, which is quite acceptable for engineering design, indicating that the choice of the flow curve fitting equation was unimportant.

Cite this publication as follows:
Malkin AY, Masalova I, Pavlovski D, Slatter P: Is the Choice of Flow Curve Fitting Equation Crucial for the Estimation of Pumping Characteristics?, Appl. Rheol. 14 (2004) 89.

The aim of this paper is to present a new phenomenological rheological model suitable for the description of a wide class of viscoelastic fluids. Classical phenomenological models predict the relation shear viscosity vs. shear rate (or shear stress) for shear-thinning (or thickening) materials exhibiting smooth monotonous passage from the first - upper (lower) - Newtonian plateau to the second - lower (upper) - one. However, present state of non- Newtonian materials used in practice (ranging from aqueous surfactant solutions, bituminous materials, associative polymers, polymer thickeners, lacquers and gels, to some special disperse systems, etc.) evokes the need to describe this - for many materials non-monotonous - relation in the corresponding way, i.e. through the sufficiently simple phenomenological model with a moderate number of parameters. A six-parameter model enabling description of not only monotonous but also non-monotonous course of shear viscosity function against shear rate (stress) is proposed including physical characterisation of the parameters. This model describes not only extreme points (maximum or minimum) but also a possible appearance of intermediate Newtonian plateau or its indication. The meaning and influence of the individual six parameters is documented on the experimental data published in the literature. There is a good agreement of the model proposed with many different experimental data representing different rheological behaviour. The applicability of this model for a wide class of viscoelastic materials is its principal advantage over the hitherto published phenomenological models.

Cite this publication as follows:
David J, Filip P: Phenomenological Modelling of Non-Monotonous Shear Viscosity Functions, Appl. Rheol. 14 (2004) 82.

The yield stress has, since its conception, been a source of fierce and often acrimonious debate. This review article deals with the issue, looking at problems related to the meaning of the definition, timescale of the observation, whether the yield stress is a property of concentrated suspensions or is linked to the strength of coherent network structures. We discuss the problematic nature of how to measure the yield stress, directly or indirectly, and examples of the vane geometry are given. Throughout, absolutist and realist theories and evidence are presented and a consensus is finally drawn. Rheologists should embrace the consequences of the absolutist and realist theories and apply them to their everyday world - whatever the timescale!

Cite this publication as follows:
Watson JH: The Diabolical Case of the Recurring Yield Stress, Appl. Rheol. 14 (2004) 40.

A creeping squeeze flow apparatus [1 - 2] was modified with a Fizeau interferometer optical motion transducer and equipped with a high-temperature, high-vacuum enclosure. Long-term squeeze flow experiments were done on a broad-MW, 1 melt-flow index commercial HDPE at 190.C, with runs covering about a week. Over this period, no thermal degradation of the polymer was observed, and the geometry of the apparatus was stable. Low-shear-rate viscosities were measured within the maximum shear rates from 1.7 ¥ 10-5 to 7.6 ¥ 10-5 1/s (stress ~ 1.7 to 8 Pa), resulting in an two-decade expansion in the experimental window for this difficult-to-characterize HDPE resin with long relaxation times.

Cite this publication as follows:
Cua EC, Shaw MT: Creeping Sphere-Plane Squeeze Flow to Determine the Zero-Shear-Rate viscosity of HDPE Melts, Appl. Rheol. 14 (2004) 33.

A short synopsis of the recently proposed reptation models based on the Doi and Edwards. tube concept is provided. Specifically, a critical examination of a number of theories like the .simplified. Mead-larson-Doi model, the Ötinger model and the .Double Convection Reptation. model of Marrucci and coworkers has been performed. These models have been chosen due the fact that are computationally tractable as they mimic the chain dynamics in the tube using unconnected portions of the chain in a mean field way. Overall, we find each of these models to be equally competitive barring a few exceptional cases, where it is suspected that certain critical assumptions, made during the formulation of the model could lead to inaccurate predictions under transient or lagrangian unsteady settings.

Cite this publication as follows:
Gigras PG, Khomami B: An Evaluation of Single-Segment Reptation Theories for Linear Entangled Polymeric Systems, Appl. Rheol. 14 (2004) 22.

It is shown that the combined use of a mesoscopic lattice Boltzmann solver with finite-volume techniques, both enriched with local-refinement (multiscale) capabilities, permits to describe transport phenomena at fluid-solid interfaces to a degree of detail which may help dispensing with empirical correlations.

Cite this publication as follows:
Rotondi R, Succi S, Bella G: Direct Simulation of Fluid Transport at Solid Interfaces with a Multiscale Lattice-Boltzmann Finite-Volume Method, Appl. Rheol. 14 (2004) 12.

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Vilgis T: An Introduction to Elastomer Molecular Network Theory (Arthur L. Lodge), Appl. Rheol. 14 (2004) 11.

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VanPuyvelde P, Moldenaers P: Sunny Rheology School in Leuven, Appl. Rheol. 13 (2003) 317.

Red blood cell aggregation (RBCa) is a sensitive inflammation marker. RBCa determination from erythrocyte sedimentation rate, ESR, is used since long, but is unspecific unless corrected for hematocrit, Ht. Whole blood viscosity measurement at low shear rate is also sensitive to RBCa but is cumbersome to apply. To investigate whether electrical blood impedance, being sensitive to spatial red cell distribution, can be a good alternative to determine RBCa in low shear conditions. Blood was collected from 7 healthy volunteers. From each 16 different samples were prepared with 4 different Ht.s and with 4 different fibrinogen concentrations. Viscosity was measured at low shear rate (4.04 s-1) with a rotational viscometer at 37.C. Electrical blood impedance was measured during similar shear conditions and temperature in a specially designed cuvette. ESR was determined according to Westergren. A logarithmic increase of viscosity as well as of capacitance, Cm, is seen when fibrinogen rises and an exponential increase when Ht rises. However, ESR shows a logarithmic decrease with increasing Ht and an exponential increase when fibrinogen rises. The viscosity could be accurately described using an exponential model. Under similar low shear conditions and temperature in-vitro, either whole blood viscosity or electrical blood capacitance reflect red blood cell aggregation due to fibrinogen and Ht variation in a similar way.

Cite this publication as follows:
Pop GAM, Hop WJ, Moraru L, vanderJagt M, Wuak J, Dekkers D, Chang Z, Gijsen FJ, Duncker DJ, Slager CJ: Blood Electrical Impedance Closely Matches Whole Blood Viscosity as Parameter of Hemorheology and Inflammation, Appl. Rheol. 13 (2003) 305.

The effects of composition and resulting morphology on the rheology of thermoplastics filled with different talc platelets were studied in the 0-22% range of volume fraction, F. The sufficiently filled polymer composites exhibit a rheological behavior which significantly differs from the pure polymers used in this work, a linear low density polyethylene, a low density polyethylene and a polyamide 12. The changes in the rheological behavior are influenced by the size, the concentration and the surface treatment of plate-like talc particles. They also depend on the chemical nature and viscous and elastic characteristics of the polymer matrix. In particular, the effect of platelet orientation on the viscoelastic properties of reinforced composites was pointed out. For sufficiently filled systems, a low frequency response indicative of a pseudo solid-like behavior is obtained only during the first frequency sweep. In fact, the low frequency storage modulus, G., is constant. With repeated frequency sweeps, more platelets were aligned in the flow direction, thus the low frequency storage modulus gradually decreases.

Cite this publication as follows:
Mederic P, Moan M, Klopffer M-H, Saint-Gerard Y: Talc filled thermoplastic composites: Melt rheological properties, Appl. Rheol. 13 (2003) 297.

Novel approach to rheological modelling of a fly ash-water mixture is proposed. The model is first tested against the available experimental data for a corn starch-water, a glass beads-water and a fly ash-water mixture and then used taking the advantage of available CFD code for a calculation of major and minor losses. Numerical results for Quadratic model are compared with results for Power law.

Cite this publication as follows:
Marn J, Ternik P: Use of Quadratic Model for Modelling of Fly Ash-Water Mixture, Appl. Rheol. 13 (2003) 286.

Cite this publication as follows:
Schweizer T: Flow of polyolefine melts through dies,investigated by laser Doppler anemometry (Martin Schwetz), Appl. Rheol. 13 (2003) 284.

Cite this publication as follows:
Schweizer T: Influence of the molecular structure on the rheological properties of polystyrene and polycarbonate melts (Jens Hepperle), Appl. Rheol. 13 (2003) 284a.

This book covers extensively the topic of rotational spectroscopy of diatomic molecules which include closed shell systems as well as molecules with open shell electronic states. Starting with a general introduction into the field (Chap. 1), the main portion of the book (Chap. 2-7) is dedicated to theoretical descriptions, comprising the presentation of exact and effective Hamiltonians, angular momentum theory, fine and hyperfine structures, and other topics. The remainder of the book (Chap. 8-11) contains descriptions of various experimental techniques and results on diatomic molecules. In summary, this books gives a state-of-the-art description of most of the theoretical and experimental aspects concerned with rotational spectroscopy of diatomic molecules, not including however weakly bound diatomics such as rare gas dimers. Its high scientific standard recommends it for interested graduate students as well as for researchers in the field of molecular spectroscopy or related disciplines.

Cite this publication as follows:
Mä, der H: Rotational Spectroscopy of Diatomic Molecules (John Brown, Alan Carrington), Appl. Rheol. 13 (2003) 265.

Recently a new theory of viscosity of concentrated emulsions dependency on volume fraction of droplets (Starov V, Zhdanov G: J. Colloid Interface Sci, 258, 404 (2003)) has been suggested that relates the viscosity of concentrated emulsions to formation of clusters. Through experiments with milk at different concentrations of fat, cluster formation has been validated using optical microscopy and their properties determined using the mentioned theory. Viscometric studies have shown that within the shear rate range studied, both the packing density of fat droplets inside clusters and the relative viscosity of milk (viscosity over skim milk viscosity) are independent of shear-rate, but vary with volume fraction. Comparison of the experimental data with previous theories that assumed that the particles remained discrete shows wide variation. We attribute the discrepancy to cluster formation.

Cite this publication as follows:
Kyazze G, Starov V: Influence of Cluster Formation: Viscosity of Concentrated Emulsions, Appl. Rheol. 13 (2003) 259.

A general constitutive relation describing the change of viscoelastic behavior during the liquid - solid (sol - gel) transition which takes place in preceramic polymers is derived on the basis of Jeffrey.s 3-constants model with time dependent viscosities and elasticity. It is postulated that the sol - gel - transition can be analyzed analogous to the solutions of the Avrami equation used for modeling crystallization processes. Two different polymer systems used as precursor for the production of ceramic materials are investigated here: i) a mixture based on polysiloxane, alumatrane and isopropanol; ii) a non-oxidic carbodiimide gel based on the reaction of chlorosilanes with bis(trimethylsilyl)carbodiimide. Continuous measurements of the dynamic moduli versus reaction time, as well as creep tests at constant shear stress, evidenced both qualitative similarities and quantitative differences associated with the sol - gel transition of the two polymer systems. The shear rate and viscosity dependence of reaction time in creep tests, respectively the evolution of Lissajous figures associated with oscillatory experiments, are found to be consistent with the numerical simulations of the proposed constitutive relation.

Cite this publication as follows:
Balan C, Riedel R: Sol-Gel Modelling Associated with the Rheology of Polymeric Precursors of Ceramic Materials, Appl. Rheol. 13 (2003) 251.

Self-sensing is the technique of using a transducer to both actuate and sense concurrently, therefore eliminating the need for separate sensors. A sensorless rheometer could be much smaller, simpler and more robust than traditional designs. One application where such a rheometer would be desired is the in-situ measurement of curing bone cement in orthopaedic surgery. A set of equations was developed that models the relationship between force, motion and back-e.m.f. generation for a class of electromagnetic actuators. This enables velocity, displacement and force to be self-sensed from voltage measurements only. This self-sensing was validated on a conventional linear electromagnetic actuator, and a small rotary moving magnet device, which was designed to be a small self-sensing rheometer. The accuracy of the estimation was assessed and shown to compare favourably with measured data. The actuators were then used to construct simple rheometers to measure bone cement. Rheological models were used to calculate storage and loss moduli and dynamic viscosity from the self-sensed values of displacement, velocity and torque. The accuracy of these self-sensing rheometers was verified against a traditional rheometer using a silicone fluid and a polyethylene oxide solution. The self-sensing rheometers were used to characterise acrylic bone cements during curing, reinforcing and extending upon previous results. The elimination of sensors meant that it was possible to produce a small, inexpensive rheometer with a very simple structure. This indicates there is potential to develop small rheo-transducers for certain applications.

Cite this publication as follows:
Hanson B, Levesley M, Fisher J: Using Self-Sensing Techniques to Produce a Small, Robust, Inexpensive Rheometer, Appl. Rheol. 13 (2003) 242.

Cite this publication as follows:
Friedrich C: Understanding Viscoelasticity (N. Phan-Thien), Appl. Rheol. 13 (2003) 240.

The intention of the paper is to illustrate the ability of the Brownian dynamics simulation technique applied to mesoscale polymer models in order to reproduce light scattering experiments of dilute polymer solution under flow. After suitable parameterization of a real polymeric system, polystyrene solved in a oligostyrene/toluene mixture at 299 K (good solvent conditions), a bead-spring model of the polymer chain is built and used to generate molecular trajectories on a computer. Such trajectories will capture the deformational and orientational processes experienced by the real polymer chain under flow. Then, from the set of molecular conformations generated, several polymer properties as well as typical scattering patterns can be reproduced quite accurately. FENE springs were used and excluded volume and non-preaveraging hydrodynamic interaction were taken into account in order to build a chain model as realistic as needed.

Cite this publication as follows:
HernandezCifre JG, delaTorre J: Radiation Scattering by Dilute Polymer Solutions in Shear Flow: An Example of Mesoscale Modeling and Brownian Dynamics Simulation, Appl. Rheol. 13 (2003) 200.

Rutting is a primary reason of premature deterioration of asphalt highway pavements. Pavements constructed with polymer and other modifiers are showing improved performance. The virgin asphalt and modified asphalt binders and mixes used on several test sections of the I-55 highway rehabilitation project in northern Mississippi are compared. The laboratory creep compliance data for these binders were measured at low temperatures using a modified test procedure adapted for the Bending Beam Rheometer device. Dynamic Shear Rheometer was used at high service temperatures. The creep compliance data of the binder was used as an input to simulate creep compliance behavior of the mix using a micromechanical model. The field evaluation confirms the relatively poor performance of the virgin asphalt section with respect to rutting, compared to modified binder sections.

Cite this publication as follows:
Uddin W: Viscoelastic Characterization of Polymer-Modified Asphalt Binders of Pavement Applications, Appl. Rheol. 13 (2003) 191.

Apparent viscosity, ha, and first normal stress coefficient, y1, of six different concentrations of cross-linked waxy maize (CWM), 3.5-5 % w/w, and tapioca, 2.8-4 % w/w, starch dispersions (SDs) showed power law relationships with shear rate, g·, and increased with starch concentration. In both ha and y1, volume fraction of the granules, f, played a more important role than the amylose content of the continuous phase. Slope of ha - g· curves increased mildly with starch concentration, while slope of y1 - g· curves was almost the same for CWM at all concentrations and 4 % tapioca SDs. Values of ha and y1 predicted from dynamic rheological and apparent viscosity data based on the Goddard-Miller model were in reasonable agreement with experimental values.

Cite this publication as follows:
Genovese DB, Rao MA: Apparent Viscosity and First Normal Stress of Starch Dispersions: Role of Continuous and Dispersed Phases, and Prediction with the Goddard-Miller Model, Appl. Rheol. 13 (2003) 183.

Stagnation flow studies form a key research area in numerous applications dealt with industry. When a fluid approaches a solid boundary, it undergoes severe deceleration along the axis of impingement. We present the experimental findings of the effects of stagnation point on polymeric flow systems. While coating metal sheets or wires with a polymer melt, the metal sheet forms a moving plane on which a steady flow of the melt is maintained. Further in the process the polymer melt cools down and forms a coating. Stagnation region exists around the point where the polymer melt first touches the metal sheet. We try to simulate this situation except in our experiments the solid plane is not moving. The polymer solution flows down the inverted T-channel and strikes the base where we obtain the stagnation region. laser Doppler technique is used to analyze the flow profile in this region. Initial analysis includes the analysis of a Newtonian fluid which is compared to theoretical predictions. Polyisobutadiene solution with three different concentrations, 0.1%, 1% and 3%, was tested for observing the effect of the change in concentration on the flow patterns around the stagnation point. In the stagnation region the fluid is not completely stagnant but follows a non-streamwise motion.

Cite this publication as follows:
Joshi K, Wedgewood L: Stagnation Flow Studies of Polymer Solutions in 2D System, Appl. Rheol. 13 (2003) 174.

In this paper, the linear and non-linear rheological properties of estuarine cohesive sediments were investigated. The density of the sediments has been determined by pycnometry. Creep and oscillatory shear measurements have been performed in order to determine i) the transitions in mechanical response to creep and oscillatory shear and ii) the material properties of these natural fluids as a function of their density. For all samples tested, four different rheological transitions have been determined and all material properties have been shown to be satisfactorily fitted by exponential functions of the density.

Cite this publication as follows:
Aubry T, Razafinimaro T, Jacinto RS, Bassoulet P: Rheological Properties of a Natural Estuarine Mud, Appl. Rheol. 13 (2003) 142.

In this paper after a presentation of the compression test and its classical references in the rheological literature a behaviour parameter identification method is introduced using simple compression tests on concentrated geo-suspensions with a plastic fluid behaviour. The obtained theoretical test response is validated for several materials (natural soils, Kaolin clay .). It is also compared with previous solutions obtained by other authors to show that most existing solutions miss one or more terms. Elements are also given on two types of test response perturbations: the induced heterogeneity in the case of slow tests (consolidation phenomena) and the fragmentation of the outer part of sample (granular paste breakings). Finally, compression test results for a nano silica paste are presented as a example and treated as an application of the test exploitation method.

Cite this publication as follows:
Roussel N, Lano C: Plastic Fluid Flow Parameters Identification Using a Simple Squeezing Test, Appl. Rheol. 13 (2003) 132.

A novel method to continuously measure the rate of build-up of an immobilised layer (apparent filter cake) was demonstrated for three mineral suspensions containing carboxymethyl cellulose and polymer latex. These suspensions were designed to be similar to those normally used as coating colours within the paper industry. The instrumentation was based on a rheometer equipped with units for controlling (and measuring) the normal forces acting on the rotating upper plate and precise measurements of the gap height in parallel.plate geometry. The bottom plate in the measurement cell was perforated and connected to vacuum, giving the driving pressure for flow through the filter. The technique should so far be taken as a qualitative, but is an attractive method for measuring filtration in thin films under controlled shear rate. The technique enables the apparent filter cake height to be calculated at any time during dewatering of the coating colours.

Cite this publication as follows:
Jä, der J, Jarnstrom L: The Influence of Thickener Addition on Filter Cake Formation During Dewatering of Mineral Suspensions, Appl. Rheol. 13 (2003) 125.

Polymer modified asphalt is an highly temperature sensitive material. To obtain the master curves of dynamic material functions, for this material, it is necessary to perform the testing over the temperature interval from - 30.C to at least 90.C. Since in this temperature range the polymer modified asphalt undergoes the transition from a glass-like to a Newtonian-like material, the benefit of using three testing geometries is studied here. The geometries used were: torsion bar (for the low temperatures), plate-plate (for the mid range temperatures) and bob and cup (for the high temperatures). The advantage of the combination of these three geometries is discussed. Stress and strain controlled rheometers were used to conduct all dynamic experiments. Master curves obtained by these geometries cover up to 20 decades of the reduced frequency.

Cite this publication as follows:
Polacco G, Vacin OJ, Biondi D, Stastna J, Zanzotto L: Dynamic Master Curves of Polymer Modified Asphalt from Three Different Geometries, Appl. Rheol. 13 (2003) 118.

The present work is concerned with the study of the rheology of polymer solutions spanning different concentration regimes and originates from a former round-robin research programme on this subject, the S1 project, involving a number of research groups and institutions. The base fluid for this programme was the so-called S1 fluid, which is a 2.5% w/w solution of Polyisobutylene (PIB) in a solvent consisting of a mixture of polybutene oil and dekalin. In this paper a set of solutions having different concentrations of PIB are studied in steady shear, oscillatory shear and in axi-symmetrical contraction flows. The focus of the study is on the possibility of finding concentration scaling laws for polymer solutions spanning each or several of the concentration regimes. The results in shear flows show that it is possible to find scaling laws both for temperature and concentration in all regimes. Extensional results show that the curves superimpose within each concentration regime, but not over the whole range of concentrations. Accordingly, concentration scaling laws were then found for both shear and extension, the latter depending on the concentration regime: dilute, semi-dilute or concentrated.

Cite this publication as follows:
Nogueiro AJ, Maia JM: On the Influence of Concentration on the Rheology of Polymer Solutions:Can Scaling Laws Be Found?, Appl. Rheol. 13 (2003) 87.

A fluid dynamic analysis package, PolyFlow, based on the finite element method is used to study the sharkskin phenomenon. A stick-slip mechanism is used as the basis for the simulations. This study is aimed at illustrating how fluctuations in the stress at the exit from the die cause similar fluctuations in the extrudate swell ratio, resembling the sharkskin phenomenon. Such fluctuations in the stress at the exit from the die are produced by implementing a stickslip boundary condition at the die wall, mimicking a mechanism of molecular entanglement/disentanglement at the wall. We use a superposition of stress relaxation/stress growth and a periodic change in extrudate swell governed by the die exit stress level to depict sharkskin. Three relatively monodisperse polybutadienes were used in this study. The simulated sharkskin time period was found to be in good agreement with experimental findings. We found that the simulated pictures of sharkskin are similar for all three molecular weight samples. A comparison between the simulated sharkskin and experimental results show qualitative resemblance. The main problems preventing us from generating more quantitative sharkskin results mainly reside in the model limitations in depicting stress singularity, limitations in mesh design refinement and the constitutive model employed. In spite of these limitations, the qualitative agreement between simulation results and experimental data is good.

Cite this publication as follows:
Nithi-Uthai N, Manas-Zloczower I: Numerical Simulation of Sharkskin Phenomena in Polymer Melts, Appl. Rheol. 13 (2003) 79.

The focus of this paper will be on the modelling and simulation of contraction flow, with marked aspect ratio b = 6, 9, 12. Two fluid families are considered: a glycerol Newtonian solution and carboxy-methyl-cellulose (CMC) solutions which present particular rheological properties. Their shear thinning character are modelled by a Cross formula over a large scale of shear rates. The elongational properties are taken via a simplified Ericksen model into account. Experimental velocity profiles are determined using the laser Doppler Anemometry (L.D.A) technique. They are found to be in good agreement with numerical velocity profiles obtained using a finite volume method with extra source terms traducing the particular rheological behaviour proposed here. The simulations allow to determine the different values of an elongational parameter m3. Then, some numerical results concerning the total energy losses are presented using the usual concept of the equivalent length.

Cite this publication as follows:
Devienne R, Corvisier P, Lyazid A: Flow of Some Carboxymethylcellulose Solutions Through Abrupt Axisymmetric Contractions.Experimental Study and Modelling of Shear Thinning and Elongational Effects, Appl. Rheol. 13 (2003) 70.

Cite this publication as follows:
DeAngelis E: Plasma and Fluid Turbulence:Theory and Modelling (Akira Yoshizawa), Appl. Rheol. 13 (2003) 69.

We present new non-linear data in extension and two different shear histories. These data are used to compare the effectiveness of using exponential shear data and uniaxial extension data to characterise the non-linear response of an industrial LDPE melt with the pom-pom molecular model. We conclude that extension and exponential shear both allow good predictions to be made in simple shear. However, the characterisation spectrum obtained from exponential shear data fails to predict the correct degree of strain hardening at low extension rates. From this study we are able to suggest circumstances under which exponential shear provides a useful characterisation of branched polymer melts.

Cite this publication as follows:
Suneel , Graham RS, McLeish TCB: Characterisation of an Industrial Polymer Melt Through either Uniaxial Extension or Exponential Shear Data: An Application of the Pom-Pom Model, Appl. Rheol. 13 (2003) 19.

The flow behaviour of colloidal dispersions is largely influenced by the interactions between the dispersed particles. We studied the influence of either natural or synthetic polyelectrolytes solutions on flow patterns within colloidal clay dispersion. For this purpose, highly diluted aqueous polymer solutions were intruded into a radial Hele-Shaw cell filled with montmorillonite dispersions. The developing flow patterns were recorded with a high resolution digital camera. The morphological parameters: fractal dimension, total number of branching, branching density of the patterns, compactness and form were obtained by digital image analysis. The results show that the patterns are largely affected by the different polymers.

Cite this publication as follows:
Beckmann S, Niemeyer J: Flow Patterns of Polymer Solutions Injected into Dispersions of Bentonite, Appl. Rheol. 13 (2003) 14.

A mathematical model for the transient pressure response in a capillary rheometer is implemented and validated with experimental data for both a natural rubber compound and a silicone rubber compound. The pressure decay curve after the cessation of motion of the instrument piston is shown to be consistent with the extrapolation of the power law model to shear rates two decades lower than experimentally attainable in the instrument employed. The model is useful for extending the range of the instrument in question by approximating material properties at shear rates lower than attainable in a steady flow experiment.

Cite this publication as follows:
Warley R: Modeling the Pressure Decay Cure of a Capillary Rheometer, Appl. Rheol. 13 (2003) 8.

The traditional methods of measuring viscosity with rotational viscometers, i.e. cone-plate and concentric cylinder systems, are often not suitable for suspensions. To be able to measure viscosity on suspensions mixer viscometers have been developed. In this study a new design of a helical ribbon impeller has been evaluated and the Metzner-Otto approach has been used to calibrate the impeller. Different kinds of food products were studied. The Metzner-Otto parameter obtained from tomato products was lower than those obtained from starch products. The study showed that the Metzner-Otto parameter varied but seemed rather to be dependent on the composition of the food material than on the flow behaviour index. The impeller could handle high concentration of quite large particles. This type of helical ribbon impeller viscometer is thus recommended for rheological studies of suspensions with high concentration of particles.

Cite this publication as follows:
Ericksson I, Bolmstedt U, Axelsson A: Evaluation of a helical ribbon impeller as a viscosity measuring device for fluid foods with particles, Appl. Rheol. 12 (2002) 303.

The rheological behavior of model suspensions with the silicone oil M20000 and different concentrations of Cab-o-sil TS 720 resp. Durcal 5 are compared. The increase of the Cab-o-sil concentration changes the flow behavior of the suspension from shear-thinning, to pseudoplastic, and to plastic flow behavior. The first normal stress difference rises at the same time at certain shear rate. The disperse systems with Durcal 5 keep the structural viscous behavior of the silicone oil even with a filler concentration of 40.5 wt%. The dependence of the first normal stress difference on shear rate represents for suspensions with Durcal 5 only one straight line with a slope of n = 2. The normal stress has double the amount of the silicone oil M20000 at given shear rate and is independent of the used Durcal 5 concentration. It was established that suspensions with the silicone oil M20000 have a first normal stress difference that can, depending on the filler type, either increase (with Cab-o-sil TS 720) or decrease (with Durcal 5) at certain shear stress with increasing filler concentration. It is to be supposed that the decrease of the normal stress at a given shear stress, with increasing Durcal concentration, is a softening effect, caused by the filler.

Cite this publication as follows:
Hadjistamov D: Viscoelastic Behavior of Disperse Systems with Silicone Oil and Different Fillers, Appl. Rheol. 12 (2002) 297.

New compounds, called inhibitors, provide anti-yellowing effect for mechanical pulps and papers, when added to the coating formulation. The rheology of coating mixtures, which contain clay, ground calcium carbonate, starch, latex, inhibitors and other minor additives, affects to a certain extent the final quality of the coated paper. The purpose of this work is to investigate the effect of the total weight charge of inhibitors, when present between coating color ingredients, on the thixotropy and visco-elasticity of the mixture and other rheological properties. We also study the degree of interaction between inhibitor and coating ingredients using Transmission Electron Microscope (TEM) and water retention measurements. For the industrially preferred inhibitor system of low RS/UVA ratio and high total charge the coating formulation will have a significant increase in the general value of viscosity and a clear and profound shear-thinning behavior. Under the desired conditions of higher total charge the coating formulation acquires significant thixotropic behavior. A higher level of energy is required to coat such formulation. The elastic modulus increases with frequency. This rise in the elastic modulus reveals the increasing interaction between particles in the coating formulation. The total charge does not affect the resistance of a coating color to the applied stress. The coating color with low total charge has the strongest water holding capability decreasing with increasing total charge.

Cite this publication as follows:
El-Sadi H, Esmail N: The Effect of Yellowing Inhibitor Total Charge on The Rheology of Paper Coating, Appl. Rheol. 12 (2002) 289.

Cite this publication as follows:
Pearce MAD, Bellmer DD: Data Variability in Rheological Measurement of Semi-Solid Foods: Effects of Loading Normal Force, Appl. Rheol. 12 (2002) 282.

Cite this publication as follows:
Spevacek J, Ilavsky M: 4th International Conference on Polymer - Solvent Complexes and Intercalates , Appl. Rheol. 12 (2002) 260.

PolyFlow, a software package based on the finite element method was employed to simulate the extrudate swell for polybutadiene of various molecular weight (Mw) and molecular weight distribution (MWD). We calculated the relaxation spectra for the different samples and then inserted the spectra into a standard K-BKZ constitutive model used in the numerical simulations. Accurate predictions of MWD confirm the completeness of frequency range in the oscillatory shear experimental data. In turn, the wholeness of relaxation spectra as substantiated by MWD predictions, sustain the level of confidence when using constitutive models based on these spectra. We demonstrate the importance of using the full range of relaxation spectrum rather than a short range around typical shear rates for the accuracy of the numerical predictions. We found extrudate swell ratio (ESR) to be strongly dependent on MWD and stress conditions at the die exit.

Cite this publication as follows:
Nithi-Uthai N, Manas-Zloczower I: Numerical Studies of the Effect of Constitutive Model Parameters as Reflecting Polymer Molecular Structure on Extrudate Swell, Appl. Rheol. 12 (2002) 252.

In the case of some highly viscous fluids, or thick pastes (such as those exhibiting high yield stress and/or high plastic viscosity), neither rotational nor tube type viscometers are suitable for rheological characterisation. Due to their capacity for generating and maintaining high torque or high rates of rotation, kneaders and mixers can often engender shear rates in excess of those of conventional rotational viscometers. Often these devices are instrumented, to measure and record the rate of rotation of the mixing blades and the related torque on the shaft turning the blades. The major problem facing users of these mixers lies in data interpretation, specifically in relating rate of rotation and torque data to shear rate and shear stress respectively. If it were possible to obtain such relationships, useful rheological data could be generated with instrumented mixers. This work outlines the experimental and analytical techniques required to convert pertinent data from the Ika Visc MKD 0.6-H60 instrumented kneader into useful rheological quantities. The kneader is calibrated using a Newtonian fluid and the calibration successfully tested with other Newtonian fluids, as well as on shear thinning solutions. The possibility of using a constant factor, a, which accounts for both the geometric complexity of the mixing chamber, and non-ideal fluid flow properties, is examined. It is shown that a is not constant, but depends on the non-Newtonian flow indices. At moderate and high rates of kneading blade rotation, calibration was not reliable and results are based on rates of rotation from 0 - 8rpm for the slower of the two mixing blades (0-16rpm for the quickly rotating blade). A number of assumptions and empirical relationships are utilised for this technique. The approximate nature of the technique necessitated by their use is more than offset by providing us with a potentially important outcome in that the capacity for collecting rheological data available to the interested scientist or engineer has been enhanced. A robust calibration technique has been developed, which is not, in principle limited to the specific equipment utilised for our analysis.

Cite this publication as follows:
Kealy T, Tiu C: Calibration of a Commercial Kneader for Rheological Applications, Appl. Rheol. 12 (2002) 241.

Bentonite are extensively used materials in a wide range of applications. Creep and oscillatory shear experiments in the linear viscoelastic domain were carried out on bentonite-water suspensions at different solid fractions. It was found that bentonite dispersions exhibit important viscoelastic behavior which could be represented by the generalized Kelvin-Voigt mechanical model. It is well known that an exhaustive study of colloidal dispersions may require the determination of its viscoelastic properties over a wide frequency scale. Unfortunately, due to microstructure changes, the experiments are limited in time. In order to avoid such limitation, oscillatory data were deduced from creep curves - without actually vibrating the clay dispersions - because a periodic experiment at frequency w is qualitatively equivalent to a creep test at time 1/w. That is, it was possible to complete the dynamic response in the low-frequency range using data obtained from the transient response in creep.

Cite this publication as follows:
Bekkour K, Kherfellah N: Linear Viscoelastic Behavior of Bentonite-Water Suspensions, Appl. Rheol. 12 (2002) 234.

Cite this publication as follows:
Stieger M: The rheology handbook - for users of rotational and oscillatory rheometers (T. Mezger), Appl. Rheol. 12 (2002) 232.

Cite this publication as follows:
Karttunen M, Vattulainen I, Lukkarinen A: SoftSimu 2002 -Novel Methods in Soft Matter Simulations, Appl. Rheol. 12 (2002) 200.

The rheological behaviour of hydrated maize starch is investigated by means of a Haake internal mixer equipped with a sealed chamber. Results were obtained at temperatures between 89 and 115°C with water content between 25 and 30%. Through a proper calibration torque measurements and rotation speeds are converted to shear stress and shear rate data and this leads to the plot of a flow curve in the 10 - 1000 s-1 range. The data are compared with results of capillary rheometer and show that the mixer enables a reproducible plastification of the maize starch. The viscosity of the maize starch in the high shear rate range can be described by an apparent power law taking into account the moisture and temperature effects. On a larger range of shear rate, a Carreau law is preferred but the dependence on the temperature can only be described with shift factors that require a moisture dependent activation energy. Finally, this later discrepancy can be avoided by using a reference temperature to fulfil the iso-free volume condition by taking a constant temperature difference towards the glass transition of the samples. The glass transition is calculated by the Couschman and Karasz equation.

Cite this publication as follows:
Brouillet-Fourmann S, Carrot C, Mignard N, Prochazka F: On the Use of an Internal Mixer For the Rheological Characterizattion of Maize Starch, Appl. Rheol. 12 (2002) 192.

A numerical study is conducted on the behaviour of yield stress fluids in a mixing vessel equipped with anchor agitator in laminar regime. It is shown that extending a standard Carreau model of shear thinning fluid is a suitable practice. Validations versus Couette flow analytical solution are satisfactory. Main features of local hydrodynamics and global power consumption are described for a 2D flow. Significant changes in the flow pattern are observed for low inertia and high yield stress and the results are considered as guidelines for further laboratory experiments.

Cite this publication as follows:
Marouche M, Anne-Archard D, Boisson HC: A Numerical Model of Yield Stress Fluid Dynamics in a Mixing Vessel, Appl. Rheol. 12 (2002) 182.

The structural development undergoing during the cure of a latex polymer is accompanied by viscoelastic changes, so that this process can be investigated using a rheological approach. We present in this paper the results of a study carried out on one of the most widely used chemical binders in the field of textile nonwovens: acrylic latexes. The rheological measurements have been performed on the latex films in a rectangular torsion and dynamic oscillatory mode, and the observations are discussed in terms of crosslinking. The results obtained show that the zone where crosslinking occurs in the polymer can be clearly identified by the investigation method used.

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Lewandowski M, Rochery M, Bellayer S, Fourdrin S: Rheology of the Curing Process of Acrylic Latexes Used as Chemical Binders, Appl. Rheol. 12 (2002) 174.

The flow behavior of two commercial liquid crystalline polymers (LCPs), trade name Vectra B 950 and Vectra L 950 supplied by Ticona, was investigated using a capillary rheometer with a special double slit die. The pressure drops in convergent and divergent wedge passage between the two slit sections, which are influenced by the curvature strains in nematic melts, were determined and compared with the pressure drops of a conventional polystyrene (PS) with flexible polymer chains. Furthermore the extensional viscositiy was determined from the pressure drop in convergent wedge passage. The development of the shear induced texture as a function of shear rate was investigated by use of a rapidly coolable double slit die with the same gap design as the double slit die used for viscosity measurement. The structural analysis was performed using polarized light microscopy.

Cite this publication as follows:
Nguyen TN, Geiger K, Fritz H-G: Rheological properties and shear induced texture development of thermotopic liquid crystalline polymer melts, Appl. Rheol. 12 (2002) 142.

We examine the validity of the slump test for predicting the yield stress of polymeric suspensions and mineral suspensions. First we propose a modification of this test: in order to make measurements on fluids with high yield stress (of the order of several hundreds of Pascal) we add a mass at the sample top. From detailed observations of the slump in time we show that, for polymeric suspensions (hair gel and sewage sludges), two critical stresses can be distinguished which almost exactly correspond to the two critical stresses (respectively corresponding to a regime change and to the asymptotic slump) observed in rheometry during creep tests. Thus the slump test appears as a practiceful and relevant means to determine the intrinsic properties of these fluids. For mineral suspensions it is shown that the flow abruptly stops after a short time, a behaviour in agreement with the results of rheometrical tests carried out by progressively decreasing the applied stress. In that case the slump also appears to significantly depend on the procedure and cannot be related to a single property of the material.

Cite this publication as follows:
Baudez J-C, Chabot F, Coussot P: Rheological Interpretation of the Slump test, Appl. Rheol. 12 (2002) 133.

A frequent problem in the production of metallocene linear low-density polyethylene (mLLDPE) films is the occurrence of flow instabilities, e.g. sharkskin, or degradation of material, which limit the production rate and decrease the product quality. If such problems arise, the question is what causes these phenomena and how they can be avoided. With the aim of understanding these problems and providing some guidelines for their suppression, rheological measurements together with modelling of these melt flows are often employed. In the present study, flow behaviour of two commercially available mLLDPEs was determined and used for the process simulation. The paper shows that the capillary-rheology data together with 2D finite element method can be used for the prediction of sharkskin phenomenon as well as degradation of mLLDPE melts in film blowing dies. It also reveals that the degradation of the materials in these dies can be quantified through wall shear stress. Finally, the paper describes how these findings can help optimize the flow channel in the film blowing die to avoid the undesirable flow phenomena.

Cite this publication as follows:
Zatloukal M, Vlcek J, Slanik A, Lengalova A, Simonik J: Experimental and numerical investigation into metallocene polymer melt flow in film blowing dies, Appl. Rheol. 12 (2002) 126.

Cite this publication as follows:
Kroger M: Fluid dynamics: theory, computation, and numerical simulation (C. Pozrikidis), Appl. Rheol. 12 (2002) 105.

The objective of this study is mainly to review recent work concerning the numerical modeling of the stick-slip and gross melt fracture polymer extrusion instabilities. Three different mechanisms of instability are discussed: (a) combination of nonlinear slip with compressibility; (b) combination of nonlinear slip with elasticity; and (c) constitutive instabilities. Furthermore, preliminary numerical simulations of the time-dependent, compressible extrudate-swell flow of a Carreau fluid with slip at the wall, using a realistic macroscopic slip equation that is based on experimental data for a high-density polyethylene, are presented.

Cite this publication as follows:
Achilleos E, Georgiou GC, Hatzikiriakos SG: On numerical simulation of polymer extrusion instabilities, Appl. Rheol. 12 (2002) 88.

The vane geometry with a large gap is used to determine the Newtonian, non-Newtonian and viscoelastic properties of complex fluids. We show that when this geometry is carefully characterized, it can be used for precise rheometry. A novel effective cylinder approximation is used to obtain the shear rate and shear stress factors. The effective radius is found to be close to the height of the triangle formed by joining the tips of adjacent blades. This result differs significantly from that of previous work. Flow visualization has been used to confirm that the stream lines bend towards the centre between the blades. These factors can be used to determine the flow curves of non-Newtonian liquids, using Krieger.s power law expansion. The standard procedure for using the vane to determine the yield stress is also carefully investigated and alternative procedures are suggested.

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Baravian C, Lalante A, Parker A: Vane rheometry with a large, finite gap, Appl. Rheol. 12 (2002) 81.

The temperature dependent flow properties of highly filled polymer compounds intended for production of hard-metal parts by powder injection moulding (PIM) technology were studied. The pure binder based on polyethylene, ethylene and butyl acrylate block copolymer and paraffin, and its compounds with hard-metal carbide powder (up to 55 vol. %) were prepared by melt mixing at 180.C. The flow properties were investigated at the temperature range from 140.C to 200.C using capillary rheometer operating flow at a constant piston speed. The measure of temperature sensitivity of PIM compounds, activation energy of shear flow, decreases with powder loading and shear rate. The Arrhenius relation for these materials is only valid in the stable flow region. At the temperatures above 170.C the compounds filled with 45 vol. % carbide powder and higher exhibit an unstable flow of pressure oscillations type at the shear rates above 103 s-1. The onset of pressure oscillations is strongly affected by temperature. The relation between critical shear stress for the onset of pressure oscillations and temperature is non-linear.

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Honek T, Hausnerova B, Saha P: Temperature dependent flow properties of powder injection moulding compounds, Appl. Rheol. 12 (2002) 72.

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Mavrantzas VG, Tsamopoulos J: The 3rd International Conference of the Hellenic Society of Rheology (HSR), Appl. Rheol. 12 (2002) 35.

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Eischen JC, Windhab EJ: Viscosity of Cocoa and Chocolate Products, Appl. Rheol. 12 (2002) 32.

The viscoelastic properties of a magneto-rheological fluid can be variably controlled using a magnetic field. A new measuring method is introduced which is based on oscillatory tests. In contrast to flow curves from experiments at steady shear rate, the new method allows an exact determination of a magneto-rheological fluid.s viscoelastic properties as a function of the preset magnetic field strength. The .Magneto Sweep. is an oscillatory test method, each with constant amplitude and constant frequency while logarithmically increasing the magnetic field strength (Magneto Sweep). For typical magneto-rheological fluids (MRF) three characteristic regions and two significant transition points can be determined. These transitions mark the corresponding change in material behavior resulting from an increasing magnetic field strength.

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Wollny K, Lä, uger J, Huck S: Magneto Sweep - A Method for characterizing the Viscoelastic Properties of Magneto-Rheological Fluids, Appl. Rheol. 12 (2002) 25.

Due to a number of practical difficulties, both in- and on-line measurements of the rheological properties of complex systems during extrusion are usually performed at the end of the extruder, under very specific experimental conditions. This makes this type of instruments more useful for quality control than for process optimisation, since information about the influence of the geometry and/or processing conditions on the evolution of the material characteristics inside the extruder is not easily gathered. Recently, however, the authors have developed an on-line capillary rheometry system that overcomes most of the existing problems and allows small amounts of sample to be tested in very near real time, along the extruder. The present work aims at illustrating the usefulness of this concept for the study of physical compounding processes and some reactive systems. Two very different systems will be used for that purpose: a reactive extrusion process (the peroxide-induced thermal degradation of polypropylene) and the dispersive mixing involved in the preparation of thermoplastic/carbon fibre composites.

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Maia JM, Carneiro OS, Machado AV, Covas JA: On-Line Rheometry for Twin-Screw Extrusion (Along the Extruder) and its Applications, Appl. Rheol. 12 (2002) 18.

The grouts are suspensions containing cement used in the technique of prestressing by post-tension. Cement, from its chemical nature, protects the wire ropes (strands) from corrosion. To be able to play correctly this protective role, the grout must remain homogeneous and must entirely cover the strands. The lack of stability of the grouts, which results in packing or sedimentation, is a major problem. In this article, we try to correlate the rheological properties of the grout with its capacity to remain homogeneous. We show that an increase in the concentration of superplasticizer, a polymer solution, decreases the thixotropic behavior of the grout, but on the other hand, increases the effects of sedimentation. We explain this phenomenon by the modification of the structure of a three-dimensional network in relation to the interparticle interactions.

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LeRoy R, Boucenna I, Flaud P: Stability of Cement Grout: Study of Sedimentation Phenomena, Appl. Rheol. 12 (2002) 12.

Suitability of finite difference method and finite volume method for computation of incompressible non newtonian flow is analyzed. In addition, accuracy of numerical results depending of mesh size is assessed. Both methods are tested for driven cavity and compared to each other, to results from available literature and to results obtained using commercial code CFX 4.3.

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Marn J, Delic M, Zunic Z: Non-Newtonian Fluid Flow Analysis with Finite Difference and Finite Volume Numerical Models, Appl. Rheol. 11 (2001) 325.

A method has been proposed for quantitative characterization of the flow behaviour of fluids, which is an important problem of applied rheology. Particle Image Velocimetry technique has been used for visualization and measurement of the velocity field. The rheometric study of the fluid is aimed at determining the character of the flow and its dynamic viscosity. It is shown that the experimental data obtained for the velocity field and the viscosity are necessary and sufficient for determining the shear stress field at each point of the flow bulk. The major part of the investigations are performed using a Newtonian fluid (epoxy resin), but some data for the non- Newtonian fluid (solution of xantan) are shown too. The flow is produced by gravity in a system of tubes (a barrel and a capillary) with different round crossections. The possibility of further improvement of the combined rheo-optical method is shown.

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