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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.
Jan Ullsperger, Robert Valek
Properties of polymer solutions intended for formation of hollow fibers membranes by inversion phases process
Appl. Rheol. 28:6 (2018) 65935 (7 pages) ►
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.
Mohsen Javanmard, Mohammad Hasan Taheri, Seyed Mehdi Ebrahimi
Heat Transfer of Third-Grade Fluid Flow in a Pipe Under An Externally Applied Magnetic Field with Convection on Wall
Appl. Rheol. 28:5 (2018) 56023 (11 pages) ►
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.
Arild Saasen, Jan David Ytrehus
Rheological Properties of Drilling Fluids - Use of Dimensionless Shear Rates in Herschel-Bulkley Models and Power-Law Models
Appl. Rheol. 28:5 (2018) 54515 (10 pages) ►
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.
Francisco J. Galindo-Rosales
2nd Summer School on Complex Fluid-Flows in Microfluidics
Appl. Rheol. 28:4 (2018) 49-51 ►
► Cite this publication as follows:
Galindo-Rosales FJ: 2nd Summer School on Complex Fluid-Flows in Microfluidics, Appl. Rheol. 28 (2018) 49.
Abdulwahab S. Almusallam, T.B. Bini
Scaling Law Accomplished through Correlation of Large Amplitude Oscillatory Shear of Immiscible Polymer Blends with Jackson and Tucker Model
Appl. Rheol. 28:4 (2018) 46039 (10 pages) ►
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.
Salaheldin Elkatatny, Muhammad Shahzad Kamal, Fahd Alakbari, Mohamed Mahmoud
Optimizing the Rheological Properties of Water-based Drilling Fluid Using Clays and Nanoparticles for Drilling Horizontal and Multi-Lateral Wells
Appl. Rheol. 28:4 (2018) 43606 (8 pages) ►
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.
Samer Alokaily, Kathleen Feigl, Franz X. Tanner, Erich J. Windhab
Numerical Simulations of the Transport of Newtonian and Non-Newtonian Fluids via Peristaltic Motion
Appl. Rheol. 28:3 (2018) 32832 (15 pages) ►
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.
Alexander Busch, Velaug Myrseth, Paal Skjetne, Milad Khatibi, Stein Tore Johansen
Rheological characterization of polyanionic cellulose solutions with application to drilling fluids and cuttings transport modeling
Appl. Rheol. 28:2 (2018) 25154 (17 pages) ►
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.
S. M. Sohel Murshed, Carlos Nieto de Castro, Jose Enrique Julia
First European Symposium on Nanofluids (ESNf2017)
Appl. Rheol. 28:1 (2018) 45-47 ►
► Cite this publication as follows:
SohelMurshed SM, NietodeCastro C, EnriqueJulia J: First European Symposium on Nanofluids (ESNf2017), Appl. Rheol. 28 (2018) 45.
Mohammad Reza Garmsiri, Hassan Haji Amin Shirazi
The effect of suspension properties on shear yield stress and compressibility of the suspension of copper flotation tailings
Appl. Rheol. 28:1 (2018) 15721 (8 pages) ►
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.
Carlos Eduardo Carbone, Roberto Cesar de Oliveira Romano, Maria Alba Cincotto, Rafael Giuliano Pileggi
Hardening stage evaluation of white Portland cements using oscillatory and compressive rheometry, isothermal calorimetry and the Vicat test
Appl. Rheol. 28:1 (2018) 16396 (9 pages) ►
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.
Mohammadreza Shafiei, Steve Bryant, Matthew Balhoff, Chun Huh, Roger T. Bonnecaze
Hydrogel Formulation for Sealing Cracked Wellbores for CO2 Storage
Appl. Rheol. 27:6 (2017) 64433 (8 pages) ►
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.
Francisco J. Galindo-Rosales
1st Summer School on Complex Fluid-Flows in Microfluidics (2017)
Appl. Rheol. 27:5 (2017) 46-47 ►
► Cite this publication as follows:
Galindo-Rosales FJ: 1st Summer School on Complex Fluid-Flows in Microfluidics (2017) , Appl. Rheol. 27 (2017) 46.
The 3rd Romainan Society of Rheology - Summer School of Rheology
Appl. Rheol. 27:4 (2017) 47-49 ►
► Cite this publication as follows:
Balan C: The 3rd Romainan Society of Rheology - Summer School of Rheology, Appl. Rheol. 27 (2017) 47.
Myoungsung Choi, Robert K. Prudhomme, George W. Scherer
Rheological evaluation of compatibility in oil well cementing
Appl. Rheol. 27:4 (2017) 43354 (9 pages) ►
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.
F.M. Leon-Martinez, P. F. de J. Cano-Barrita
Yield stress of mortars in rotational and oscillatory shear experiments usinag a ball measuring system
Appl. Rheol. 27:4 (2017) 45838 (11 pages) ►
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.
B.A. Macias-Rogriguez, A.G. Marangoni
Bakery shortenings: structure-mechanical function relations
Appl. Rheol. 27:3 (2017) 33410 (8 pages) ►
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.
M. Kowalska, A. Krzton-Maziopa, A. Zbikowska, K. Tarnowska
Rheological Properties and Physical Stability of O/W Emulsions Stabilized by Diacylglycerols Formed During Enzymatic Interesterification
Appl. Rheol. 27:3 (2017) 35118 (9 pages) ►
► Cite this publication as follows:
Kowalska MM, Krzton-Maziopa A, Zbikowska A, Tarnowska K: Rheological Properties and Physical Stability of O/W Emulsions Stabilized by Diacylglycerols Formed During Enzymatic Interesterification, Appl. Rheol. 27 (2017) 35118.
Rheology and stability of lightweight polymer-modified self-consolidating concrete
Appl. Rheol. 27:2 (2017) 25807 (11 pages) ►
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.
Silju-John Kunnkattu, Theresia Gross, Sandra Stoppelkamp, Juvano Knieps, Torsten Remmler, Stefan Fennrich, Hans Peter Wendel, Nicole Rauch
Potential of a piezo-based measuring method (PAV) as a haemostasis monitoring system compared to a rotational rheometer
Appl. Rheol. 27:1 (2017) 13540 (11 pages) ►
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.
Larbi Hammadi, Alain Ponton
Rheological investigation of vase of dam: effects of aging time, shear rate and temperature
Appl. Rheol. 27:1 (2017) 14667 (9 pages) ►
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.
Caroline E. Wagner, Alexander C. Barbati, Jan Engmann, Adam S. Burbidge, Gareth H. McKinley
Apparent shear thickening at low shear rates in polymer solutions can be an artifact of non-equilibration
Appl. Rheol. 26:5 (2016) 54091 (5 pages) ►
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.
Gamze Yazar, Ozlem Duvarci, Sebnem Tavman, Jozef L. Kokini
Non-Linear Rheological Properties of Soft Wheat Flour Dough at Different Stages of Farinograph Mixing
Appl. Rheol. 26:5 (2016) 52508 (11 pages) ►
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.
Dimitri Merger, Mahdi Abbasi, Juri Merger, A. Jeffrey Giacomin, Chaimongkol Saengow, Manfred Wilhelm
Simple Scalar Model and Analysis for Large Amplitude Oscillatory Shear
Appl. Rheol. 26:5 (2016) 53809 (15 pages) ►
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.
Leonid Bulavin, Nikolai Lebovka
7th International Conference, Physics of Liquid Matter: Modern Problems (PLMMP 2016)
Appl. Rheol. 26:4 (2016) 54-55 ►
► 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.
Annika Gram, Johan Silfwerbrand, Bjorn Lagerblad
Particle Motion in Fluid - Analytical and Numerical Study
Appl. Rheol. 26:2 (2016) 23326 (7 pages) ►
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.
Tom C. B. McLeish (Ed.)
Obituary Alexei Likhtman (1971-2015)
Appl. Rheol. 25:6 (2015) 53-54 ►
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.
Magda Nystrom, Waqas Muhammad, Margareta Bulow, Olle Ekberg, Mats Stading
Effects of rheological factors on perceived ease of swallowing
Appl. Rheol. 25:6 (2015) 63876 (9 pages) ►
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.
Tommi Borg, Esko J. Paakkonen
Linear viscoelastic model for different flows based on control theory
Appl. Rheol. 25:6 (2015) 64304 (10 pages) ►
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.
M. Bueno, A. Garcia, M.N. Partl
Applications of Strain-Rate Frequency Superposition for Bituminous Binders
Appl. Rheol. 25:6 (2015) 65980 (12 pages) ►
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 (&gaMMa;. = ω&gaMMa;0) 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.
Markus Hutter, Ger Koper
7th International Workshop and Summer School on Nonequilibrium Thermodynamics (IWNET 2015)
Appl. Rheol. 25:5 (2015) 61-61 ►
► 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.
Florentina Talos, Alain Ponton, Berengere Abou, Alexandre Chevillot, Helene Lecoq, Simion Simon
Multiscale viscoelastic investigation of silica-calcium-phosphate sol-gel materials
Appl. Rheol. 25:6 (2015) 63567 (12 pages) ►
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.
Mercedes Fernandez, Arrate Huegun, Maria Eugenia Munoz, Anton Santamaria
Nonlinear oscillatory shear flow as a tool to characterize irradiated polypropylene/MWCNT nanocomposites
Appl. Rheol. 25:4 (2015) 45154 (12 pages) ►
The relative intensity and phase of the third harmonic, I3/1 and Φ3-Φ1, 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 &gaMMa;o 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 λ of irradiated polypropylene, but this technique is very difficult to be applied for nanocomposites. Face to this shortcoming, an empirical correlation between λ and the value of the I3/1 plateau when &gaMMa;o 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.
Ahmed M. Mostafa, Ammar Yahia
Performance evaluation of different rheometric shearing techniques to disperse concentrated cement suspension
Appl. Rheol. 25:3 (2015) 34337 (9 pages) ►
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.
Rushita Shah, Nabanita Saha, Takeshi Kitano, Petr Saha
Influence of strain on dynamic viscoelastic properties of swelled (H2O) and biomineralized (CaCO3) PVP-CMC hydrogels
Appl. Rheol. 25:3 (2015) 33979 (10 pages) ►
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.
M.R. Garmsiri, H. Haji Amin Shirazi, M.R. Yarahmadi
An analysis of the influence of cylinder dimension ratio and lifting velocity on the slump test results
Appl. Rheol. 25:2 (2015) 23416 (8 pages) ►
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.
Michael A. Nilsson, Jonathan P. Rothstein
Effect of fluid rheology and sandstone permeability on enhanced oil recovery in a microfluidic sandstone device
Appl. Rheol. 25:2 (2015) 25189 (11 pages) ►
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.
Umme Amina Mannan, Md Islam, Mekdim Weldegiorgis, Rafiqul Tarefder
Experimental investigation on rheological properties of recycled asphalt pavement mastics
Appl. Rheol. 25:2 (2015) 22753 (9 pages) ►
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.
Monika Sellerberg, Diego Di Bartolo, Julia Oberrecht, Jörg Tiller, Peter Walzel
Viscometric measurement of protease activities on gelatine substrate
Appl. Rheol. 24:6 (2014) 62660 (10 pages) ►
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.
Haider Dakhil, Andreas Wierschem
Measuring low viscosities and high shear rates with a rotational rheometer in a thin-gap parallel-disk configuration
Appl. Rheol. 24:6 (2014) 63795 (6 pages) ►
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.
Paulo R. de Souza Mendes, Alexandra A. Alicke, Roney L. Thompson
Parallel-plate geometry correction for transient rheometric experiments
Appl. Rheol. 24:5 (2014) 52721 (10 pages) ►
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.
Jeremy N. Fowler, John Kirkwood, Norman J. Wagner
Rheology and microstructure of shear thickening fluid suspoemulsions
Appl. Rheol. 24:4 (2014) 43049 (10 pages) ►
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.
Malgorzata Kowalska, Anna Krzton-Maziopa
pH effect on viscoelastic behavior and physicochemical properties of walnut oil emulsions
Appl. Rheol. 24:4 (2014) 45105 (9 pages) ►
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.
Martin Boisly, Markus Kästner, Jörg Brummund, Volker Ulbricht
Large amplitude oscillatory shear of the Prandtl element analysed by Fourier Transform Rheology
Appl. Rheol. 24:3 (2014) 35478 (11 pages) ►
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'(&gaMMa;) = G''(&gaMMa;) 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.
Hsiao Wei Tan, Misni Misran
Effect of chitosan-modified fatty acid liposomes on the rheological properties of the polysaccharide-based gel
Appl. Rheol. 24:3 (2014) 34839 (9 pages) ►
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.
T. A. Cheema, G. M. Kim, C. Y. Lee, J. G. Hong, M. K. Kwak, C. W. Park
Characteristics of blood vessel wall deformation with porous wall conditions in an aortic arch
Appl. Rheol. 24:2 (2014) 24590 (8 pages) ►
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.
Martin Boisly, Markus Kästner, Jörg Brummund, Volker Ulbricht
General aspects of yield stress fluids - Terminology and definition of viscosity
Appl. Rheol. 24:1 (2014) 14578 (11 pages) ►
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.
Matthias, M. Musialek
The 23rd Stuttgarter Kunststoffkolloquium
Appl. Rheol. 23:3 (2013) 183-184 ►
► Cite this publication as follows:
Musialek MM: The 23rd Stuttgarter Kunststoffkolloquium, Appl. Rheol. 23 (2013) 183.
Hugo Faria, F. M. Andrade Pires, A. Torres Marques
Identification of the Combined Rheology of Mixtures of Epoxy Resins with Different Initial Curing States
Appl. Rheol. 23:4 (2013) 42413 (8 pages) ►
A coMMercial epoxy resin system was tested under several different mixing conditions with viscometer and rheometer apparatuses. In each test, two portions of the same resin, prepared at different times, were mixed and their joint behavior was analysed. The differences between the behavior of this blend and the neat (unmixed) resin after the mixing point were, then, critically assessed. Both the preparation time gap and the mixing ratio of the two portions coherently affected the overall blend behavior. However, the coMMonly accepted linear combination of the contributions of the portions of resin with different degrees of cure, usually employed to describe the joint behavior, was not applicable for the entire time interval after mixture.► Cite this publication as follows:
Faria H, AndradePires FM, TorresMarques A: Identification of the Combined Rheology of Mixtures of Epoxy Resins with Different Initial Curing States, Appl. Rheol. 23 (2013) 42413.
J. David, P. Filip, A.A. Kharlamov
Back extrusion of Vocadlo-type fluids
Appl. Rheol. 23:4 (2013) 45366 (8 pages) ►
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.
Hai Dang Le, Geert De Schutter, El-Hadj Kadri, Salima Aggoun, Jan Vierendeels, Serge Tichko, Peter Troch
Computational fluid dynamics calibration of Tattersall MK-II type rheometer for concrete
Appl. Rheol. 23:3 (2013) 34741 (12 pages) ►
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.
Mayur Tikmani, Jalila Boujlel, Philippe Coussot
Assessment of penetrometry technique for measuring the yield stress of muds and granular pastes
Appl. Rheol. 23:3 (2013) 34401 (10 pages) ►
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.
4th Eurosummer School on biorheology & Symposium on micro and nanomechanics and mechanobiology of cells, tissues and systems
Appl. Rheol. 23:1 (2013) 57-58 ►
► Cite this publication as follows:
Antonova N: 4th Eurosummer School on biorheology & Symposium on micro and nanomechanics and mechanobiology of cells, tissues and systems, Appl. Rheol. 23 (2013) 57.
M. J. Hato, S. K Pillai, H. J. Choi, K. Zhang
The rheology of non-aquoeous suspension of modified eccabond fine (EBF) clay
Appl. Rheol. 23:3 (2013) 34870 (9 pages) ►
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.
D. Konigsberg, T. M. Nicholson, P.J. Halley, T. J. Kealy, P. K. Bhattacharjee
Online process rheometry using oscillatory squeeze flow
Appl. Rheol. 23:3 (2013) 35688 (6 pages) ►
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.
Arsia Takeh, Sachin Shanbhag
A Computer Program to Extract the Continuous and Discrete Relaxation Spectra from Dynamic Viscoelastic Measurements
Appl. Rheol. 23:2 (2013) 24628 (10 pages) ►
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.
► Related Software ReSpect available for free download at mathworks. ►
► 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.
Aaron Goh, David Hassell, Azuraien Jaafar
Institute of Materials Malaysia (IMM) 1st Rheology Symposium 2012
Appl. Rheol. 22:6 (2012) 347-347 ►
► 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.
Helen S. Melito, Christopher R. Daubert, E. Allen Foegeding
Creep and large amplitude oscillatory shear behavior of whey protein isolate/.-carrageenan gels
Appl. Rheol. 22:6 (2012) 63691 (14 pages) ►
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.
Edmundo Brito-de la Fuente, Nadege Staudinger-Prevost, Lida A. Quinchia, Concepcion Valencia, Pedro Partal, Jose M. Franco, Crispulo Gallegos
Design of a new spoon-thick consistency oral nutrition supplement using rheological similarity with a swallow barium test feed
Appl. Rheol. 22:5 (2012) 53365 (8 pages) ►
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.
Reinhardt Kotze, Johan Wiklund, Rainer Haldenwang
Optimization of the UVP+PD rheometric method for flow behavior monitoring of industrial fluid suspensions
Appl. Rheol. 22:4 (2012) 42760 (11 pages) ►
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.
Johan Wiklund, Beat Birkhofer, SAK Jeelani, Mats Stading, Erich J. Windhab
In-line rheometry of particulate suspensions by pulsed ultrasound velocimetry combined with pressure difference method
Appl. Rheol. 22:4 (2012) 42232 (10 pages) ►
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.
Manuel Navarro-Gonzalez, Manfred H. Wagner
Storage stability of bitumen modified by the addition of ground rubber, swollen SBS and polymeric short fibers
Appl. Rheol. 22:2 (2012) 24691 (11 pages) ►
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.
Stephan Laske, Andreas Witschnigg, Hannelore Mattausch, Milan Kracalik, Gerald Pinter, Michael Feuchter, Guenther Maier, Clemens Holzer
Determining the ageing of polypropylene nanocomposites using rheological measurements
Appl. Rheol. 22:2 (2012) 24590 (9 pages) ►
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.
Petr Filip, Petra Svrcinova
Measurement of elongational viscosity of polymer melts using SER Universal Testing Platform
Appl. Rheol. 22:1 (2012) 14776 (5 pages) ►
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.
Yongwoo Inn, David C. Rohlfing
Application of Creep Test to Obtain the Linear Viscoelastic Properties at Low Frequency Range for Polyethylene Melts
Appl. Rheol. 22:1 (2012) 15260 (8 pages) ►
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.
Deepti Tanjore and Christopher R. Daubert
A vane-in-cup approach to measure viscoelastic properties of gelatin gels through torque-time responses from Brookfield YR-I viscometer
Appl. Rheol. 21:6 (2011) 63172 (11 pages) ►
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.
Nono Darsono, Hiroshi Mizunuma, Hiromichi Obara
Rheological study of the solidification of photopolymer and dispersed nanotube systems
Appl. Rheol. 21:6 (2011) 63566 (15 pages) ►
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.
Arnaud Perrot, Yannick Melenge, Patrice Estelle, Damien Rangeard, Christophe Lanos
The back extrusion test as a technique for determining the rheological and tribological behaviour of yield stress fluids at low shear rates
Appl. Rheol. 21:5 (2011) 53642 (10 pages) ►
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.
Jose Manuel Valverde, M J Espin, M A S Quintanilla, A Castellanos
Jamming and rheology of fluidized beds of magnetized particles
Appl. Rheol. 21:3 (2011) 35179 (9 pages) ►
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.
Stefan Kirchberg, Gerhard Ziegmann
Effect of Spherical Iron Silicon (FeSi) Microparticles on the Viscosity Behaviour of Polypropylene Melt
Appl. Rheol. 21:3 (2011) 35495 (8 pages) ►
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.
Ehssan Nazockdast, Hossein Nazockdast
Rheological Modeling of Polymer/layered silicate Nanocomposites
Appl. Rheol. 21:2 (2011) 25434 (11 pages) ►
This work takes a phenomenological approach to modeling the rheology of polymer/clay nanocomposites in (shear rate) &gaMMa; ≤ 1 / s based on experimental observations . 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, &gaMMa;0ω, at different nonlinear strain amplitudes, a modified Bingham-type constitutive equation proposed by Doiraswamy et. al  was used to model σM+σP while σH was modeled by using constitutive equation proposed by Lipscomb et. al  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 &gaMMa; = &gaMMa;0ω. 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  was employed for modeling σM+σP. Both Coussot and Doraiswamy equations gave a reasonable quantitative prediction of transient stress in simple shear flow up to shear rates as high as &gaMMa; = 0.1 / s.► Cite this publication as follows:
Nazockdast E, Nazockdast H: Rheological Modeling of Polymer/layered silicate Nanocomposites, Appl. Rheol. 21 (2011) 25434.
Pradipta Kumar Senapati, Barada Kanta Mishra, Aparajita Sahu, Vimal Kumar
Effective composition of high concentration fly ash-bottom ash mixture slurry for efficient disposal through pipelines
Appl. Rheol. 21:2 (2011) 23480 (10 pages) ►
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 (λ = 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.
6th DGK Workshop Rheology of Cosmetic Emulsions. 25 Years of Rheology at Beiersdorf
Appl. Rheol. 21:2 (2011) 126-128 ►
► Cite this publication as follows:
Brummer R: 6th DGK Workshop Rheology of Cosmetic Emulsions. 25 Years of Rheology at Beiersdorf, Appl. Rheol. 21 (2011) 126.
Nur Hassan, Masud Khan, Mohammad Rasul, Darryn Rackemann
Bubble Rise Velocity and Trajectory in Xanthan Gum Crystal Suspension
Appl. Rheol. 20:6 (2010) 65102 (13 pages) ►
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.
Marina Neophytou, Stella Pourgouri, Antonis Kanellopoulos, Michael Petrou, Ioannis Ioannou, Georgios Georgiou, Andreas Alexandrou
Determination of the rheological parameters of self-compacting concrete matrix using slump flow test
Appl. Rheol. 20:6 (2010) 62402 (12 pages) ►
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.
Hemaka C.H. Bandulasena, William B. Zimmerman, Julia M. Rees
Rheometry of non-Newtonian polymer solution using microchannel pressure driven flow
Appl. Rheol. 20:5 (2010) 55608 (8 pages) ►
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.
Adina Ghirisan, Diana Broboana, Corneliu Balan
1st SRR - Summer School of Rheology 2010
Appl. Rheol. 20:5 (2010) 305-306 ►
► Cite this publication as follows:
Ghirisan A, Broboana D, Balan C: 1st SRR - Summer School of Rheology 2010, Appl. Rheol. 20 (2010) 305.
Christian Clasen, H. Pirouz Kavehpour, Gareth H. McKinley
Bridging Tribology and Microrheology of Thin Films
Appl. Rheol. 20:4 (2010) 45049 (13 pages) ►
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.
2nd International Workshop on Soft Condensed Matter Physics and Biological Systems (SMPPMM 2010)
Appl. Rheol. 20:3 (2010) 176-176 ►
► Cite this publication as follows:
Mabrouk B: 2nd International Workshop on Soft Condensed Matter Physics and Biological Systems (SMPPMM 2010), Appl. Rheol. 20 (2010) 176.
Claus Gabriel, Christoffer Kieburg, H. Martin Laun
Clutch and brake related testing of magnetorheological fluids using the BASF twin gap magnetocell
Appl. Rheol. 20:4 (2010) 41778 (10 pages) ►
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.
Carlos I. Mendoza, Ivan Santamaria-Holek
Rheology of concentrated emulsions of spherical droplets
Appl. Rheol. 20:2 (2010) 23493 (8 pages) ►
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.
3rd Eurosummer School on Biorheology & Symposium on micro and nanomechanics and mechanobiology of cells, tissues and systems
Appl. Rheol. 20:1 (2010) 55-56 ►
► Cite this publication as follows:
Antonova N: 3rd Eurosummer School on Biorheology & Symposium on micro and nanomechanics and mechanobiology of cells, tissues and systems, Appl. Rheol. 20 (2010) 55.
Aminallah Rabia, Madeleine Djabourov, Francois Feuillebois, Thierry Lasuye
Rheology of wet pastes of PVC particles
Appl. Rheol. 20:1 (2010) 11961 (9 pages) ►
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.► Cite this publication as follows:
Rabia A, Djabourov M, Feuillebois F, Lasuye T: Rheology of wet pastes of PVC particles, Appl. Rheol. 20 (2010) 11961.
Nour el Hou Belkham, Abdelaziz Mehamha, Djafer Benachour
Rheological behavior of alumina ceramic pastes
Appl. Rheol. 19:6 (2009) 64969 (5 pages) ►
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.
Goretti Goikoetxeaundia, Mercedes Fernandez, Maria Eugenia Munoz, Anton Santamaria
Rheology applied to investigate roofing membranes: The case of an ecological alternative
Appl. Rheol. 19:6 (2009) 62305 (8 pages) ►
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.► Cite this publication as follows:
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 non-Newtonian Fluid Mechanics of Technical Fibre Suspensions: Compressive Flows
Appl. Rheol. 19:4 (2009) 44290 (24 pages) ►
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.
Katarzyna Niedzwiedz, Oliver Arnolds, Norbert Willenbacher, Rudiger Brummer
Capillary Breakup Extensional Rheometry of Yield Stress Fluids
Appl. Rheol. 19:4 (2009) 41969 (10 pages) ►
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.► Cite this publication as follows:
Niedzwiedz K, Arnolds O, Willenbacher N, Brummer R: Capillary Breakup Extensional Rheometry of Yield Stress Fluids, Appl. Rheol. 19 (2009) 41969.
High performance ceramics by advanced colloidal processing (PhD thesis summary)
Appl. Rheol. 19:2 (2009) 119-120 ►
► Cite this publication as follows:
Sarraf H: High performance ceramics by advanced colloidal processing (PhD thesis summary), Appl. Rheol. 19 (2009) 119.
Reinhardt Kotze, Rainer Haldenwang, Paul Slatter
Rheological characterisation of highly concentrated mineral suspensions using an Ultrasonic Velocity Profiling with combined Pressure Difference method
Appl. Rheol. 18:6 (2008) 62114 (10 pages) ►
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.
Zoran Susteric, Tomaz Kos
Rheological Idiosyncrasies of Elastomer/Clay Nanocomposites
Appl. Rheol. 18:5 (2008) 54894 (10 pages) ►
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.
Vassilios Kelessidis, Roberto Maglione
Shear rate corrections for Herschel-Bulkley fluids in Couette geometry
Appl. Rheol. 18:3 (2008) 34482 (11 pages) ►
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, &GaMMa;HB, and of the three Herschel-Bulkley rheological parameters. The errors made when these rheological parameters are computed using Newtonian shear rates, &GaMMa;N, 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 &GaMMa;HB versus the parameters obtained using &GaMMa;N and this is an outcome of the higher &GaMMa;HB 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.
Methods to characterize electrorheological suspensions in consideration of the temperature influence (PhD thesis summary)
Appl. Rheol. 18:3 (2008) 148-149 ►
► Cite this publication as follows:
Schneider S: Methods to characterize electrorheological suspensions in consideration of the temperature influence (PhD thesis summary), Appl. Rheol. 18 (2008) 148.
Anne Pitkowski, Taco Nicolai, Dominique Durand
Shear flow and large amplitude oscillation shear study of solutions of aggregating micellar casein particles
Appl. Rheol. 18:2 (2008) 23050 (7 pages) ►
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.
P.J. Martin, K.N. Odic, A.B. Russell
Rheology of commercial and model ice creams
Appl. Rheol. 18:1 (2008) 12913 (11 pages) ►
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.
Mostafa Elbakry, Amr Radi
Genetic programming approach for flow of steady state fluid between two eccentric spheres
Appl. Rheol. 17:6 (2007) 68210 (5 pages) ►
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.
Christopher Klein, Paul Venema, Leonard Sagis, Dagmar van Dusschoten, Manfred Wilhelm, Hans Wolfgang Spiess, Erik van der Linden, Salman S. Rogers, Athene M. Donald
Rheo-optical Measurements using Fast Fourier Transform and Oversampling
Appl. Rheol. 17:4 (2007) 45210 (7 pages) ►
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.
The 'Yield stress myth?' paper - 21 years on
Appl. Rheol. 17:4 (2007) 43110 (5 pages) ►
Consideration is given to the reaction to Barnes and Walters' 4-page The yield stress myth? paper published 21 years ago. It has been cited approximately 180 times since then, as either a standard reference for 'yield stress' papers, or to disagree with its sentiment that yield stresses do not actually exist, but are a useful approximation. The references that cite the paper are categorized and coMMented on.► Cite this publication as follows:
Barnes HA: The 'Yield stress myth?' paper - 21 years on, Appl. Rheol. 17 (2007) 43110.
2nd Eurosummer School on Biorheology & Symposium on Micro Mechanobiology of Cells, Tissues and Systems
Appl. Rheol. 17:3 (2007) 167-168 ►
► Cite this publication as follows:
Antonova N: 2nd Eurosummer School on Biorheology & Symposium on Micro Mechanobiology of Cells, Tissues and Systems, Appl. Rheol. 17 (2007) 167.
Mustapha M. Ould Eleya, Sundaram Gunasekaran
Rheology of fluid foods for dysphagic patients
Appl. Rheol. 17:3 (2007) 33137 (9 pages) ►
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.
Rheology essentials of cosmetic and food emulsions (R. Brummer)
Appl. Rheol. 17:2 (2007) 75 ►
► Cite this publication as follows:
Mitarotonda A: Rheology essentials of cosmetic and food emulsions (R. Brummer), Appl. Rheol. 17 (2007) 75.
B. Mokdad, E. Pruliere, A. Ammar, F. Chinesta
On the simulation of kinetic theory models of complex fluids using the Fokker-Planck approach
Appl. Rheol. 17:2 (2007) 26494 (14 pages) ►
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.
Lukas U Arenson, Sarah M Springman, David C Sego
The Rheology of Frozen Soils
Appl. Rheol. 17:1 (2007) 12147 (14 pages) ►
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.
Scattering from shear-ordered dispersions
Appl. Rheol. 17:1 (2007) 11412 (7 pages) ►
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.
Daniel Therriault, Scott White, Jennifer Lewis
Rheological Behavior of Fugitive Organic Inks for Direct-Write Assembly
Appl. Rheol. 17:1 (2007) 10112 (8 pages) ►
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.
Qianmei Li, Guozhong Wu, Yaodong Liu, Yingshe Luo
A rheological study of binary mixtures of Ionic Liquid [Me3NC2H4OH]+[Zn2Cl5]- and ethanol
Appl. Rheol. 16:6 (2006) 334-339 ►
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.
Landmark Paper Index: Definition and Application to Rheological (η-)Journals
Appl. Rheol. 16:6 (2006) 329-333 ►
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.
Peggy Courtois, Rammile Ettelaie, Jianshe Chen
Numerical Studies of Transport Properties in Heterogeneous Food Systems
Appl. Rheol. 16:5 (2006) 275-286 ►
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.
S.A.R. Hashmi, T. Kitano
Rheology of LCP/PET Blends at Solid and Molten States of LCP
Appl. Rheol. 16:3 (2006) 152-160 ►
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.
Publication Specific Impact of Articles Published by Rheological Journals
Appl. Rheol. 15:6 (2005) 406-409 ►
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.
Jun Sato, Victor Breedveld
Evaporation Blocker for Cone-Plate Rheometry of Volatile Samples
Appl. Rheol. 15:6 (2005) 390-397 ►
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.
J. Götz, L. Rewesa, M. Walch, A. Geissler
Influence of an Ultrasonic Treatment on the Structure and Flow Behaviour of Oxide Ceramic Masses
Appl. Rheol. 15:4 (2005) 204-217 ►
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) . 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.
M.P. Escudier, J. Clement-Evans, R.J. Poole
Freezing as a Storage Process for Aqueous Polymer Solutions
Appl. Rheol. 15:2 (2005) 90-97 ►
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.
Harro Bauer, Elke Fischle, Lothar Gehm, Wolfgang Marquardt, Thomas Mezger, Michael Osterhold
Modern rheological test methods: Fundamentals and comparative testing programme for the determination of the yield point
Appl. Rheol. 15:2 (2005) 122-123 ►
► Cite this publication as follows:
Bauer H, Fischle E, Gehm L, Marquardt W, Mezger T, Osterhold M: Modern rheological test methods: Fundamentals and comparative testing programme for the determination of the yield point, Appl. Rheol. 15 (2005) 122.
J.P. Plog, W.-M. Kulicke, C. Clasen
Influence of the Molar Mass Distribution on the Elongational Behaviour of Polymer Solutions in Capillary Breakup
Appl. Rheol. 15:1 (2005) 28-37 ►
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.► Cite this publication as follows:
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.
A Comprehensive Treatise of the High Temperature Specification Parameter |G*|/(1-(1/tan d sin d)) for Performance Grading of Asphalts
Appl. Rheol. 14:6 (2004) 303-314 ►
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.
Paulo R. Souza Mendes, Eduardo S.S. Dutra
Viscosity Function for Yield-Stress Liquids
Appl. Rheol. 14:6 (2004) 296-302 ►
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.
Characterization of the linear viscoelastic region in suspensions of zirconium oxide: Cohesive energy obtained from the critical parameters
Appl. Rheol. 14:3 (2004) 126-132 ►
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.
Edwin C. Cua, Montgomery T. Shaw
Creeping Sphere-Plane Squeeze Flow to Determine the Zero-Shear-Rate viscosity of HDPE Melts
Appl. Rheol. 14:1 (2004) 33-39 ►
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.
G.A.M. Pop, W.J. Hop, M. van der Jagt, J. Quak, D. Dekkers, Z. Chang, F.J. Gijsen, D.J. Dunncker, C.J. Slager
Blood Electrical Impedance Closely Matches Whole Blood Viscosity as Parameter of Hemorheology and Inflammation
Appl. Rheol. 13:6 (2003) 305-312 ►
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.
Rotational Spectroscopy of Diatomic Molecules (John Brown, Alan Carrington)
Appl. Rheol. 13:5 (2003) 265 ►
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.
Jerker Jäder, Lars Järnström
The Influence of Thickener Addition on Filter Cake Formation During Dewatering of Mineral Suspensions
Appl. Rheol. 13:3 (2003) 125-131 ►
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.
Rheological Characterization of Polymers (PhD thesis summary)
Appl. Rheol. 13:2 (2003) 93-94 ►
► Cite this publication as follows:
Thimm W: Rheological Characterization of Polymers (PhD thesis summary), Appl. Rheol. 13 (2003) 93.
A.J. Nogueiro, J.M. Maia
On the Influence of Concentration on the Rheology of Polymer Solutions:Can Scaling Laws Be Found?
Appl. Rheol. 13:2 (2003) 87-92 ►
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.
Reni Devienne, Philippe Corvisier, Abdel Lyazid
Flow of Some Carboxymethylcellulose Solutions Through Abrupt Axisymmetric Contractions.Experimental Study and Modelling of Shear Thinning and Elongational Effects
Appl. Rheol. 13:2 (2003) 70-78 ►
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.
I. Eriksson, U. Bolmstedt, A. Axelsson
Evaluation of a helical ribbon impeller as a viscosity measuring device for fluid foods with particles
Appl. Rheol. 12:6 (2002) 303-308 ►
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.
Melissa J.Daniels Pearce, Danielle D.Bellmer
Data Variability in Rheological Measurement of Semi-Solid Foods: Effects of Loading Normal Force
Appl. Rheol. 12:6 (2002) 282-288 ►
Previous studies involving rheological measurement of semi-solid foods have reported a large amount of data variability, but have focused little on understanding the cause of such variability. This project examined whether differences in normal force have an effect on the variability of rheological measurements. Experimental methods focused on error introduced during sample loading; specifically whether normal force application during loading influenced the storage (G.) and loss (G.) moduli of semi-solid and liquid foods. Samples were loaded to 5 or 20 N between the parallel plates of a TA-1000N rheometer and tested iMMediately. For all semi-solid products tested, normal force application during sample loading did significantly affect oscillatory parameters, with G. and G. measurements increasing up to 50 % with greater normal force. However, loading normal force did not significantly influence the parameters measured for the liquid sample. This suggests that differences in normal force during loading could be a significant source of data variability during rheological measurement of semi-solid products.► 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.
Tim Kealy, Carlos Tiu
Calibration of a Commercial Kneader for Rheological Applications
Appl. Rheol. 12:5 (2002) 241-251 ►
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.
T.N. Nguyen, K. Geiger, H.-G. Fritz
Rheological properties and shear induced texture development of thermotopic liquid crystalline polymer melts
Appl. Rheol. 12:3 (2002) 142-150 ►
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.
M.Zatloukal, J. Vlcek, A. Slanik, A. Lengalova, J. Simonik
Experimental and numerical investigation into metallocene polymer melt flow in film blowing dies
Appl. Rheol. 12:3 (2002) 126-132 ►
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.
J. Marn, M. Delic, Z. Zunic
Non-Newtonian Fluid Flow Analysis with Finite Difference and Finite Volume Numerical Models
Appl. Rheol. 11:6 (2001) 325-335 ►
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.► Cite this publication as follows:
Marn J, Delic M, Zunic Z: Non-Newtonian Fluid Flow Analysis with Finite Difference and Finite Volume Numerical Models, Appl. Rheol. 11 (2001) 325.
Silvara Junus, Jenni L. Briggs
Vane sensor system in small strain oscillatory testing
Appl. Rheol. 11:5 (2001) 264-270 ►
To overcome difficulties (slip, sample disturbance) associated with traditional sensors, a semi-empirical method was developed to allow the use of a 4-bladed vane sensor in small strain oscillatory testing. It was assumed that the vane sensor acted as a bob with an acting radius, RV, different from the actual radius of the vane (0.02005 m). To solve for RV, the complex modulus obtained using a concentric cylinder sensor from reference viscoelastic fluid, was set equal to the complex modulus equation for vane sensor. RV values were grouped into three phase shift ranges from 5° to less than 16°, from 16° to less than 60°, and from 60° to 90° and they were 0.01883, 0.01869, and 0.01850 m, respectively. These values were used in the calculation of viscoelastic properties of eight coMMercial food products, which resulted in complex modulus values within 15% of those obtained using a concentric cylinder sensor. Results showed that this particular vane and cup system can be used to directly measure the storage and loss moduli of viscoelastic material and phase shift within the upper frequency value of 6.28 rad/s. Above 6.28 rad/s, there is an inconsistency in phase shift angles measured using vane method. This method is ideal for testing thixotropic food systems because disturbance is minimal during sample loading, giving more accurate viscoelastic measurements.► Cite this publication as follows:
Junus S, Briggs JL: Vane sensor system in small strain oscillatory testing, Appl. Rheol. 11 (2001) 264.
New Rheological Test Method to Determine the Dewatering Kinetics of Suspensions
Appl. Rheol. 11:4 (2001) 197-202 ►
Rheology plays an important role in dewatering processes. It is therefore interesting to analyze the dewatering process and the rheological behavior of a suspension simultaneously. An exact determination of the iMMobilization point at the maximum of the loss factor as well as the iMMobilization time can be attained using an oscillatory time test with preset strain. The degree of dewatering is determined via normal force controlled gap setting. This report offers an insight into the theory of the dewatering of liquid supersaturated suspensions and shows how the kinetics of dewatering can be determined using paper coating as an example.► Cite this publication as follows:
Wollny K: New Rheological Test Method to Determine the Dewatering Kinetics of Suspensions, Appl. Rheol. 11 (2001) 197.
R. Muller, M. Bouquey, F. Mauguiere, G. Schlatter, C. Serra, J. Terrisse
Rheology of reactive polymer blends: separation of mixing and reaction steps
Appl. Rheol. 11:3 (2001) 141-152 ►
The crosslinking reaction in various types of polymer blends was followed by rheological measurements. Miscible polymers with controlled glass transition temperature, chain length and number of functional units per chain were synthesized by bulk radical copolymerization. Other experiments were carried out on iMMiscible systems based on coMMercial polymers. Blends were either prepared in a batch mixer or directly in the parallel-plate geometry of a rotational rheometer. Due to the low glass transition or melting temperature of most blend components, it was usually possible to separate the mixing step which was carried out at low temperature from the crosslinking reaction which was followed by small amplitude dynamic measurements at higher temperatures. The influence of several parameters on the reaction was studied, in particular : the reaction temperature, the amount of shear during the mixing step (or mixing time), the number of functional units per chain in each blend component and the blend composition. For the miscible blends, a master curve for the dependence of the elastic modulus G as a function of reaction time could be drawn for different functionalities and blend compositions.► Cite this publication as follows:
Muller R, Bouquey M, Mauguiere F, Schlatter G, Serra C, Terrisse J: Rheology of reactive polymer blends: separation of mixing and reaction steps, Appl. Rheol. 11 (2001) 141.
Chenxu Yu, Sundaram Gunasekaran
Correlation of dynamic and steady viscosities of food materials
Appl. Rheol. 11:3 (2001) 134-140 ►
Eight coMMercial foods representing a wide range of viscosities (i.e. honey, condensed milk, mayonnaise, tomato ketchup, cream cheese, yogurt, process and Mozzarella cheeses) were investigated. Their steady shear viscosity and dynamic complex viscosity were determined by rheological measurements at two temperatures using a Bohlin-CVO rheometer. Based on experimental data, shear rate dependence of steady flow apparent viscosity and frequency dependence of dynamic viscosity was established and compared. It was determined that for condensed milk, tomato ketchup and mayonnaise, a modified Cox-Merz relation could be established. For cream cheese, a generalized Cox-Merz relation was proposed; and for yogurt, a deviation from the Cox-Merz rule was found. For Mozzarella and process cheeses a sharp drop in steady shear viscosity was noticed between 1~10 s-1 shear rate range. The Cox-Merz rule was not applicable for these cheese samples.► Cite this publication as follows:
Yu C, Gunasekaran S: Correlation of dynamic and steady viscosities of food materials, Appl. Rheol. 11 (2001) 134.
Howard A. Barnes
An examination of the use of rotational viscometers for the quality control of non-Newtonian liquid products in factories
Appl. Rheol. 11:2 (2001) 89-101 ►
A frequent task undertaken by quality-control personnel in typical consumer-goods factories is the measurement of the viscosity of liquid products. The problem often faced in this task is how to strike the correct balance between the complete rheological characterisation of the non-Newtonian properties of the liquid of interest which requires expensive, sophisticated equipment and can be quite time-consuming and the dictates of production pressures that demand, as near as possible, an instant decision, and one usually based on a single number. Here we consider the rheological issues that arise in such a debate, which is aimed at finding what adequate characterisation would require. We will investigate the implications of liquids products being non-Newtonian for two of the most coMMonly encountered viscometers in factory quality laboratories, i.e. the simple dip-in rotating spindle viscometer of the Brookfield type (with its different forms and many imitations) and the more sophisticated concentriccylinder- type device typified by the Haake Rotovisco VT 550 range. Each is capable of giving a single-number answer for viscosity, but the implications of understanding this single number are different in each case, with the dip-in viscometer being in an infinite sea of liquid and the concentric-cylinder situation being narrow gap. We also investigate when the infinite sea of the dip-in viscometer is effectively infinite and when is a concentric- cylinder geometry really narrow gap? We will use the power-law model throughout our discussions.► Cite this publication as follows:
Barnes HA: An examination of the use of rotational viscometers for the quality control of non-Newtonian liquid products in factories, Appl. Rheol. 11 (2001) 89.
Ming Long Yao, Jayesh C. Patel
Rheological characterization of body lotions
Appl. Rheol. 11:2 (2001) 83-88 ►
This study is attempted to demonstrate the application of rheological measurements in characterization of cosmetics products. As part of this study, several rheological tests were carried out on three coMMon, coMMercially available body lotions to analyze their complex properties. The tests described in this study were simple and predictive in which the viscoelastic properties were successfully related with the end-use performance properties such as applicability, processing behavior, temperature sensitivity and storage and thermal stability.► Cite this publication as follows:
Yao ML: Rheological characterization of body lotions, Appl. Rheol. 11 (2001) 83.
D. Jaros, J. Petrag, H. Rohm, F. Ulberth
Milk fat composition affects mechanical and rheological properties of processed cheese
Appl. Rheol. 11:1 (2001) 19-25 ►
Laboratory-scale experiments were carried out to explore the influence of the composition of the fat phase on mechanical and rheological properties of processed model cheeses. Cheeses made from caseinates, emulsifying salts and a milk fat fraction liquid at 24°C, which was achieved by thermal separation, showed much lower moduli than processed model cheeses manufactured with a fat fraction solid at 30°C. Processed model cheeses made from caseinates, emulsifying salts and a hard butter with a low amount of unsaturated fatty acids were significantly higher in firmness than cheeses made with soft butter with a higher amount of unsaturated fatty acids. In experiments using mature Gruyè and emulsifying salts, processed cheeses made from suMMer Gruyè were less firm than processed winter Gruyè. The results indicate that fat composition strongly affects mechanical properties of processed cheese, and a model is provided to explain structural changes during deformation.► Cite this publication as follows:
Jaros D, Petrag J, Rohm H, Ulberth F: Milk fat composition affects mechanical and rheological properties of processed cheese, Appl. Rheol. 11 (2001) 19.
M. Mehmet Ak and Sundaram Gunasekaran
Simulation of lubricated squeezing flow of a Herschel-Bulkley fluid
Appl. Rheol. 10:6 (2000) 274-279 ►
► Cite this publication as follows:
Ak MM, Gunasekaran S: Simulation of lubricated squeezing flow of a Herschel-Bulkley fluid, Appl. Rheol. 10 (2000) 274.
Fluid immobilization - a structure-related key mechanism for the viscous flow behavior of concentrated suspension systems
Appl. Rheol. 10:3 (2000) 134-139 ►
► Cite this publication as follows:
Windhab EJ: Fluid immobilization - a structure-related key mechanism for the viscous flow behavior of concentrated suspension systems, Appl. Rheol. 10 (2000) 134.
F. Hetzel, J. Nielsen, S. Wiesner, R. Brummer
Dynamic mechanical freezing points of cosmetic O/W emulsions and their stability at low temperatures
Appl. Rheol. 10:3 (2000) 114-118 ►
► Cite this publication as follows:
Hetzel F, Nielsen J, Wiesner S, Brummer R: Dynamic mechanical freezing points of cosmetic O/W emulsions and their stability at low temperatures, Appl. Rheol. 10 (2000) 114.
The rheology of cosmetic emulsions (DGK)
Appl. Rheol. 9:6 (1999) 272-273 ►
► Cite this publication as follows:
Brummer R: The rheology of cosmetic emulsions (DGK), Appl. Rheol. 9 (1999) 272.
Return to Mecca: a brief summary of the 71st annual society of rheology meeting
Appl. Rheol. 9:6 (1999) 270-271 ►
► Cite this publication as follows:
Tuminello WH: Return to Mecca: a brief summary of the 71st annual society of rheology meeting , Appl. Rheol. 9 (1999) 270.
Wolfgang Thimm, Christian Friedrich, Dieter Maier, Michael Marth, and Josef Honerkamp
Determination of Molecular Weight Distributions from Rheological Data: An
Appl. Rheol. 9:4 (1999) 150-157 ►
► Cite this publication as follows:
Thimm W, Friedrich C, Maier D, Marth M, Honerkamp J: Determination of Molecular Weight Distributions from Rheological Data: An, Appl. Rheol. 9 (1999) 150.
R. Brummer, F. Hetzel, C. Harder
Correlation of Polymer Properties with Dynamic Mechanical Measurements
Appl. Rheol. 7:4 (1997) 173 ►
► Cite this publication as follows:
Brummer R, Hetzel F, Harder C: Correlation of Polymer Properties with Dynamic Mechanical Measurements, Appl. Rheol. 7 (1997) 173.
G Hamer, R Brummer
Rheological Methods to Characterize Cosmetics
Appl. Rheol. 7:1 (1997) 19 ►
► Cite this publication as follows:
Hamer G, Brummer R: Rheological Methods to Characterize Cosmetics, Appl. Rheol. 7 (1997) 19.
G Reinhard, A Moll, U Rammelt
Thixotropy at the Pigmentation of Waterthinnable Polymer Dispersions
Appl. Rheol. 6:3 (1996) 124 ►
► Cite this publication as follows:
Reinhard G, Moll A, Rammelt U: Thixotropy at the Pigmentation of Waterthinnable Polymer Dispersions, Appl. Rheol. 6 (1996) 124.
M Schmidt, AJ Franck
Comments on the Application of Stress Controlled and Strain Controlled Rheometers
Appl. Rheol. 4:1 (1994) 23 ►
► Cite this publication as follows:
Schmidt M, Franck AJ: Comments on the Application of Stress Controlled and Strain Controlled Rheometers, Appl. Rheol. 4 (1994) 23.
S Bschorer, W Schierholz
Simulation Programms for Non-Newtonian Fluids
Appl. Rheol. 3:3 (1993) 198-201 ►
► Cite this publication as follows:
Bschorer S, Schierholz W: Simulation Programms for Non-Newtonian Fluids, Appl. Rheol. 3 (1993) 198.
Some Comments on the Flow Properties of Pigment Dispersions
Appl. Rheol. 2:1 (1992) 40 ►
► Cite this publication as follows:
Schrö, der J: Some Comments on the Flow Properties of Pigment Dispersions, Appl. Rheol. 2 (1992) 40.
Conditions for Viscosity Tests
Appl. Rheol. 1:1 (1991) 24 ►
► Cite this publication as follows:
Schramm G: Conditions for Viscosity Tests, Appl. Rheol. 1 (1991) 24.
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