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Radost Ivanova, Rumiana KotsilkovaAuthor index ►
Rheological study of poly(lactic) acid nanocomposites with carbon nanotubes and graphene additives as a tool for materials characterization for 3D printing appLi.Ation
Appl. Rheol. 28:5 (2018) 54014 (10 pages) ►
In the last decades, one of the most critical issues concerning the control on the processing, structure and properties of nanocomposites is related to the dispersion of nanofiller in the polymer matrix and internal interactions resulting in percolation. In this study, we investigate the rheological behavior in oscillatory and steady shear flow of poly(lactic) acid based nanocomposites incorporating 0 - 12 wt% graphene nanoplates (GNP) and multi-walled carbon natotubes (OH-MWCNT). The effect of the filler contents and aspect ratio on the viscosity and viscoelastic response is evaluated. Three rheological techniques are used for estimation of rheological percolation threshold. Due to different aspect ratio and state of dispersion of GNP and MWCNTs the percolation threshold differs significantly for both compositions φ ≤ 1.5 wt% for MWCNT/PLA and φp ≤ 5 wt% for GNP/PLA. The larger the aspect ratio of nanofiller, the lower is the rheological percolation threshold. The visualized structure by TEM analysis confirms the rheological predictions for both type composites. The index of flow was estimated by the power law slope of the flow curves and a better dispersion was assumed for MWCNTs in comparison with GNPs due to the surface modification. Based on the rheological percolation threshold and the flow index, nanocomposites were classified in three groups: Newtonian, percolated composites and elastic solids. Both characteristics are used to select the printing parameters for the three groups of nanocomposites, suitable for fused deposition modeling (FDM).► Cite this publication as follows:
Ivanova R, Kotsilkova R: Rheological study of poly(lactic) acid nanocomposites with carbon nanotubes and graphene additives as a tool for materials characterization for 3D printing application, Appl. Rheol. 28 (2018) 54014.
In 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 appLi.Ation 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.
Concentrated suspensions are very complex in nature and exhibit non-Newtonian flow properties although the suspending fluid might behave as a Newtonian fluid. Among the interesting properties, wall slip will be the main focus of this study. The formation of wall slip layer adjacent to the solid boundary may lead to inaccurate measurement of rheological properties. So, the measured viscosity can be lower than the actual viscosity and thus a basic understanding on wall slip is critical. Concentration, particle size, and temperature are the factors affecting the wall slip mechanism. Therefore, this research study tends to study the relationship between the parameters (concentration, particle size, and temperature) and wall slip. The result shows that the slip velocity increases with shear stress under the conditions where (i) concentration decreases, (ii) particle size increases, and (iii) temperature increases. Two regression models considering the three parameters are proposed and can be used respectively as an alternative to predict slip velocity and true shear rate.► Cite this publication as follows:
Chin RJ, Lai SH, Ibrahim S, WanJaafar WZ: Factors affect wall slip: particle size, concentration and temperature, Appl. Rheol. 28 (2018) 15775.
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Sahlstrom A: Rheology Step 2 training - continuation training in application of rheological concepts and techniques - viscosity, viscoelasticity and measuring techniques, Appl. Rheol. 27 (2017) 45.
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Cheneler D: Biomedical Applications of Polymeric Materials and Composites (Francis and Kumar), Appl. Rheol. 27 (2017) 9.
Limited information exists in literature regarding the effect of styrene-butadiene rubber (SBR) latexes on rheology and stability of lightweight self-consoLi.Ating concrete (LWSCC) intended for repair and precast works. Four series of LWSCC mixtures prepared with various lightweight aggregate (LWA) and SBR concentrations were considered in this project: The free water was adjusted to secure compressive strength of 40 ± 3.5 MPa. The slump flow remained fixed at 700 ± 25 mm, while unit weight varied from 1790 to 2280 kg/m3. Test results have shown that SBR additions lead to reduced concrete flow rate and passing ability. However, improved static stability such as bleeding, segregation, and floating of LWA. The rheological properties including yield stress and plastic viscosity increased for higher SBR additions, reflecting increased cohesiveness resulting from coalescence of water-soluble latexes and binding of cementitious matrix. Three categories of LWSCC classes specified in the European Guidelines were proposed with respect to rheological properties. A Ψ-factor was developed along with series of regression models to predict the combined effect of free water, viscosity-modifier, LWA, and SBR on rheology and stability of polymermodified LWSCC.► Cite this publication as follows:
Assaad J: Rheology and stability of lightweight polymer-modified self-consolidating concrete , Appl. Rheol. 27 (2017) 25807.
The overall objective of this work was to explore the rheology of an advanced performance xanthan gum, which is able to endure the shear and turbulent flows typically found in high-shear mixers or even homogenizers. A further goal was the development of a rheological experimental setup that can be used to gain information about the structural recovery after applying a given shear stress. A fast structural recovery after cessation of shear is essential for a wide range of practical appLi.Ations. The high zero shear viscosity, strong shear thinning response along with a fast drop of viscosity with shear time and structural recovery support the appLi.Ations of this xanthan gum as thickening agent and stabilizer. The rheological characterization focused on the influence of xanthan gum concentration (0.15 – 0.40%(m/m)) on the dynamic viscoelastic properties, steady shear and thixotropic behavior, and kinetics of structural recovery.► Cite this publication as follows:
Carmona JA, Calero N, Ramirez P, Munoz J: Rheology and structural recovery kinetics of an advanced performance xanthan gum with industrial application, Appl. Rheol. 27 (2017) 25555.
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Handge UA: Geesthacht Polymer Days: 'Rheology of Polymers for Research and Application', Appl. Rheol. 27 (2017) 47.
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Fischer P: Fluid dynamics in physics, engineering and environmental applications (Klapp, Medina, Cros, and Vargas), Appl. Rheol. 26 (2016) 10.
The measurement and the investigation of the errors in a Couette rheometer have been a topic of considerable interest in many rheometric studies. In the present study, a more accurate predictor-corrector method based on CFD and the analytical solution of the problem is described. Comparing to the previous CFD-based method, in addition to considering the effect of the end parts, the presented correction factors also take into account the effect of the wide gap into a single coefficient. The correction factors are computed for both Newtonian and non-Newtonian fluids in wide and narrow gap rheometry. Results showed that the shear rate distribution across the gap is highly non-linear in non-Newtonian wide gap rheometry. Moreover, for very shear thinning fluid i.e. n < 0.4 in narrow gap rheometry, there is a need to apply correction factor to the calculated fluid properties. Comparing the presented CFD approach and the current approach, the correction factor can be enhanced up to 16% depending on the fluid behavior and the gap distance.► Cite this publication as follows:
Hamedi N, Revstedt J, Tornberg E, Innings F: Application of CFD–based Correction Factors to Increase the Accuracy of Flow Curve Determination in a Couette Rheometer, Appl. Rheol. 26 (2016) 35341.
This paper represents the rheology of screen printing pastes based on BaTiO3 nanopowder. It is found that the pastes are shear thickened fluids with subsequent shear thinning under high shear rates. Different concentrations of plasticizer in organic binder lead to various conformations of ethyl cellulose molecules that influence the type of adsorption between polymer molecules and nanoparticles. The flow loop shows intervals of shear rate corresponding to rheopexy, pseudoplasticity and thixo - tropy. The appearance of rheopexy indicates that the added amount of plasticizer may be insufficient to bind the majority of free functional groups of the polymer and the remaining groups are bound with BaTiO3 nanoparticles forming a strong structural network. But in the case of pseudoplastic structures, the polymer molecule exists in the conformation where almost all free functional groups are bound with the nanoparticle surfaces. The pseudoplastic properties of the system are caused by the structural polymer-polymer links. SEM and optical profilometry of the obtained films shows that plasticization lead to the formation of thin (less than 1 μm) smooth (Ra is equal to the size of individual BaTiO3 nanoparticle) prints.► Cite this publication as follows:
Umerova SO, Dulina IO, Ragulya AV, Konstantinova TE, Glazunova VA: Rheology of plasticized screen printing pastes based on BaTiO3 nanopowder, Appl. Rheol. 26 (2016) 33274.
DLS Microrheology involves tracking the time dependent motion or mean square displacement of dispersed tracer particles of known size using Dynamic Light Scattering (DLS) in order to determine viscoelastic properties of the dispersion medium. The viscoelastic moduLi.Are calculated using a generalised form of the Stokes-Einstein equation which requires Fourier Transformation of the MSD. An alternative approach for estimating the viscoelastic moduli uses a modified algebraic form of the generalized Stokes-Einstein equation, which employs a power law expression to describe the local change in MSD with time. Since the mean square displacement is linearly related to the creep compliance, it can be shown that the same algebraic approach can also be applied to creep measurements made on a rotational rheometer, giving access to the low frequency moduli in a fraction of the time required for oscillatory testing. Furthermore, the quality of the conversion process can be improved by fitting a Burgers model to the time domain data prior to conversion thus minimising errors associated with local differentiation, which is fundamental to the conversion approach.► Cite this publication as follows:
Duffy JJ, Rega C, Jack R, Amin S: An algebraic approach for determining viscoelastic moduli from creep compliance through application of the Generalised Stokes-Einstein relation and Burgers model, Appl. Rheol. 26 (2016) 15130.
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 appLi.Ation of high strain amplitudes. The strain-rate frequency superposition (SRFS) is an analogous technique that can experimentally determine the flow behavior from nonlinear oscillatory shear experiments. This method was originally applied to soft materials in order to study the slow relaxation process of particular systems by shifting to higher frequencies the behavior usually found at very low frequencies during conventional measurements. In this work, the feasibility of the SRFS method for assessing the rheological properties of bituminous binders has been evaluated. Oscillatory shear measurements accomplished at different constant shear strain ampliture rates (γ. = ωγ0) and test temperatures allowed analysing the influence of the nonlinear behavior of unmodified and polymer modified bitumen on their viscoelastic responses. The results showed that displacements in the responses due to different strain rates were not so significant as to extend the frequency range further than in conventional measurements. Differences in responses between both techniques were mainly observed for polymer modified binders, especially to high strain amplitudes which usually involve nonlinear behaviour. In addition, master curves obtained with constant strain rates, i.e. taking into account nonlinear response of the material, showed similar results to those constructed by using conventional methods with constant strain amplitude. From these results, a closer comprehension of the large deformations generated in asphalt pavements can be achieved by studying the nonlinear viscoelastic properties of the bituminous binder.► Cite this publication as follows:
Bueno M, Garcia A, Partl M: Applications of Strain-Rate Frequency Superposition for Bituminous Binders, Appl. Rheol. 25 (2015) 65980.
The sol-gel transition of homogeneous biocomposites synthesized using tetraethyl-orthosiLi.Ate 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.
A Sentmanat Extension Rheometer represents one out of a few experimental devices for the measurement of elongational viscosity of polymer melts. However, the appropriateness of this technique for individual polymer materials is not sufficiently apparent and in some case is disregarded or ignored. The proposed visuaLi.Ation technique is based on imprinting painted pattern from the inner surface of the studied polymer samples onto the counter-rotating drums. Digitization of the imprinted pattern gives a possibility to evaluate a degree of sagging, incorrect fixing of rectangular polymer samples to the drums, possible appearance of sample inhomogeneity (variance in thickness, bubbles, etc.). The presented visuaLi.Ation technique is demonstrated using branched LDPE Escorene. Two various imprinted patterns are applied. First, the upper and lower contours are charted on a prepared sample with the aim to determine the sample shapes during stretching and to compare them with the theoretical ones. Second, the inclined rectangular grid pattern is charted for evaluating possible inhomogeneity of the sample.► Cite this publication as follows:
Pivokonsky R, Filip P, Zelenkova J: Visualization of elongation measurements using an SER universal testing platform, Appl. Rheol. 25 (2015) 13636.
In this work, the viscosity of soybean oil subjected to thermal degradation has been determined and related to the chemical composition of the oil. In particular, it is found a linear relationship between the viscosity value and the triglycerides content during the degradation process (an increase of the former is associated to a decrease of the latter). Thus, it is shown that viscosity provides us a reliable way of measuring oil degradation and, insofar as proportional to flow time, it allows for the design of simple devices to control the oil quality. Besides, the study of the viscosity behavior along with the changes in composition during the cooking time, i.e. the period of time that the oil is being heated, give us valuable information about the type of chemical reactions occurring within the oil.► Cite this publication as follows:
Olivares-Carrillo P, PerezdelosRios A, Quesada-Medina J, HernandezCifre JG, DiazBanos FG: Viscosity as a measure of oil composition changes due to thermal degradation, Appl. Rheol. 24 (2014) 53667.
Large amplitude oscillatory shear (LAOS) rheology is often performed in order to complement steady simple shear (SSS) rheology, i.e., probe rheological properties of materials that cannot be not observed with SSS alone. However, it is difficult to measure the SSS rheology of some problematic materials due to fracture and ejection, and LAOS may alleviate these issues, at least partially. Therefore, it is of interest to obtain SSS rheology information from LAOS measurements. We show that a constitutive modeling approach may be used to unify the analysis of LAOS data obtained from different viscometric geometries and modes of control and that the LAOS data may be used to predict SSS profiles. A model elastoviscoplastic material, a Carbopol solution, was used to vaLi.Ate the approach experimentally. LAOS rheometry of problematic biomass slurries was also performed, and the SSS profiles for the slurries were predicted with more confidence than could be obtained from SSS measurements directly.► Cite this publication as follows:
Stickel JJ, Knutsen JS, Liberatore MW: Connecting large amplitude oscillatory shear rheology to unidirectional shear rheology and application to biomass slurries, Appl. Rheol. 24 (2014) 53075.
This paper is concerned with the numerical solution of polymer melt flows of both extrudate-swell and tube-tooling dieextrusion coatings, using a hybrid finite element/finite volume discretisation fe/fv. Extrudate-swell presents a single dynamic free-surface, whilst the complex polymer melt coating flow exhibit two separate free-surface draw-down sections to model, an inner and outer conduit surface of the melt. The interest lies in determining efficient windows for process control over variation in material properties, stressing levels generated and pressure drop. In this respect, major rheological influences are evaluated on the numerical predictions generated of the extensional viscosity and Trouton ratio, when comparing solution response for an exponential Phan-Thien Tanner (EPTT, network-based) model to that for a single extended Pom-Pom (SXPP, kinematic-based) model. The impact of shear-thinning is also considered. Attention is paid to the influence and variation in Weissenberg number We, solvent-fraction β (polymeric concentration), and second normal stress difference N2 (ξ parameter for both EPTT, and α anisotropy parameter for SXPP). The influence of model choice and parameters upon field response is described in situ through, pressure, shear and strain-rates and stress. The numerical scheme solves the momentum- continuity-surface equations by a semi-implicit time-stepping incremental Taylor-Galerkin/pressure-correction finite element method, whilst invoking a cell-vertex fluctuation distribution/median-dual-cell finite volume approximation for the first-order space-time hyperbolic-type stress evolution equation.► Cite this publication as follows:
Al-Muslimawi A, Tamaddon-Jahromi H, Webster MF: Numerical computation of extrusion and draw-extrusion cable-coating flows with polymer melts, Appl. Rheol. 24 (2014) 34188.
This paper presents the development of a vane rheometer to estimate mortar plastic viscosity and yield stress. The rheological parameters were developed from measurements using a procedure to convert the vane torque and rotational velocity data into shear stress versus shear rate relationships. The used procedure considered the locally sheared material as a Bingham fluid and computed the characteristic shear rate from Couette analogy. The apparatus was tested with three experimental programs in which many rheological parameters of mortar compositions were calculated. The obtained results vaLi.Ated the rheometer test procedure and confirmed that the test results are reproducible.► Cite this publication as follows:
Soualhi H, Kadri E, Ngo T, Bouvet A, Cussigh F, Kenai S: A new vane rheometer for fresh mortar: development and validation , Appl. Rheol. 24 (2014) 22594.
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Madsen CG, Abo J, Featherston DW, Baldursdottir S: Rheology: A cross-disciplinary technology evolving to take on new challenges (22nd Nordic Rheology Conference 2013), Appl. Rheol. 23 (2013) 309.
The shear thickening behavior of concentrated suspensions can be exploited to dissipate energy during impact or shear loading. To preserve the consistency of the thickening behavior in practical appLi.Ations, particle concentration, and dispersion should be kept within very close bounds over time. In this article, we analyze the influence of the processing methods and storage conditions on the rheological properties of shear thickening fluids (STF) based on monodisperse suspensions of siLi.A particles in polyethylene glycol. Particle dispersion linked to processing method and time strongly influences the value of the critical shear rate and storage in contact with air and humidity is responsible for a change in particle concentration. Encapsulating the suspensions in silicone is proposed as a solution to preserve their rheological properties over time.► Cite this publication as follows:
Soutrenon M, Michaud V, Manson JAE: Influence of processing and storage on the shear thickening properties of highly concentrated monodisperse silica particles in polyethylene glycol, Appl. Rheol. 23 (2013) 54865.
Currently more and more researches have been performing concerning the numerical simulation of the behavior of fresh concrete during pumping or formwork filling. Adequate implementation of the rheology properties of fresh concrete is a determinant key to obtain realistic simulations. However, in many cases, the rheological parameters of the fresh concrete as determined by rheometers are not sufficiently accurate. The common principle of all the rheometers is not to measure directly the rheological parameters of concrete but to measure some basic physical parameters (torque, velocity, pressure, ...) that that in some cases allow the calculation of the rheological parameter in terms of fundamental physical quantities. Errors can be caused by undesired flow phenomena which are not taken into the prediction formulas and by the inaccurate prediction formulas themselves. This is directly related to the poor calibration of the rheometer that cannot cover all ranges of materials. This paper investigates the calibration of the Tattersall MK-II rheometer by performing the numerical simulation for a tremendous range of concrete flowing in the rheometer, using computational fluid dynamics (CFD). This allows to quickly and accurately obtain the rheological properties of fresh concrete, which can then be used consistently for further flow simulations. This method can be applied for all types of rheometer.► Cite this publication as follows:
Le HD, DeSchutter G, Kadri E, Aggoun S, Vierendeels J, Tichko S, Troch P: Computational fluid dynamics calibration of Tattersall MK-II type rheometer for concrete, Appl. Rheol. 23 (2013) 34741.
We discuss the possibility of using penetrometry technique for measuring the yield stress of concentrations made of grains immersed in a colloidal phase, such as concrete or muds. In that aim we used model materials made by suspending glass beads at different concentrations in a kaolin-water paste. We then show that a uniform shear stress develops along the object (plate or cylinder) beyond the entrance length. This shear stress plotted versus the object velocity exhibits a shape similar to the flow curve of the material determined from rheometry. For materials exhibiting the typical flow curve of a simple yield stress fluid, i.e. at bead concentrations smaller than 30 %, the stress associated with an inflection point located at low velocities of this curve appears to correspond to the material yield stress. At larger concentrations of beads the suspensions have a more complex behaviour likely affected by its granular nature at a local scale and the possibility of migration or frictional effects, so that neither conventional rheometry nor penetrometry provide relevant data. We conclude by describing two practical penetrometry techniques for precisely measuring the yield stress of simple pastes.► Cite this publication as follows:
Tikmani M, Boujlel J, Coussot P: Assessment of penetrometry technique for measuring the yield stress of muds and granular pastes, Appl. Rheol. 23 (2013) 34401.
In this work, bentonite suspension and mixtures containing 5 wt% of bentonite and 0.1 and 0.5 wt% of carboxymethyl cellulose (CMC) were investigated in terms of their rheology and hydrodynamic behaviour in pipe flow. All fluids exhibited non- Newtonian rheological behaviour that can be well described by the three parameters Herschel-Bulkley model. The axial velocity distribution was determined using ultrasonic pulsed Doppler velocimetry technique. In the laminar regime the flow parameters were predicted by integration of the constitutive rheological model used. In the turbulent flow, the Dodge and Metzner model was applied to fit the experimental data. The measurements of the friction factor showed a small amount of drag reduction for the pure bentonite suspension, whereas for the polymer.clay blend the drag reduction was more important.► Cite this publication as follows:
Benslimane A, Bekkour K, Francois P: Effect of addition of Carboxymethylcellulose (CMC) on the rheology and flow properties of bentonite suspensions, Appl. Rheol. 23 (2013) 13475.
The rheological properties of polyethylene oxide (PEO) solutions were investigated, at different temperatures, using small and large deformation rheological methods. Steady-state flow measurements showed that the flow behavior of the PEO solutions is well described by the Cross model, which yields the critical concentrations c* (from the dilute regime to semidilute regime) and c** (from the semi-dilute regime to the concentrated regime). In the range of the temperatures investigated here, the apparent viscosity is found to obey the Arrhenius equation below a critical temperature we believe corresponds to the cloud point temperature. Above the cloud point temperature, the viscosity increased with temperature. Similarly below the cloud point, both transient and dynamic tests showed that PEO solutions exhibit viscoelastic behavior, where both the elastic G' and viscous G'' modules increased with the increase in concentration and with the decrease in temperature. The Cox-Merz rule was found to apply to the PEO solutions at temperatures lower than the cloud point temperature, whilst divergence was reported after phase separation. The frequencies at which G' = G'', i.e. the reciprocal of the relaxation times of the temporary polymer network, was found to increase (the relaxation times decline) with decreasing polymer concentration, in agreement with the relaxation times, derived from the Cross model. In essence, this study demonstrates that it is possible to monitor accurately the cloud point temperature of PEO solutions by viscometric analysis.► Cite this publication as follows:
Bahlouli MI, Bekkour K, Benchabane A, Hemar Y, Nemdili A: The effect of temperature on the rheological behavior of polyethylene oxide (PEO) solutions, Appl. Rheol. 23 (2013) 13435.
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Fischer P: Polymer Physics - Applications to Molecular Association and Thermoreversible Gelation (F. Tanaka), Appl. Rheol. 22 (2012) 235.
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.
Measurements of the viscosity of non-Newtonian fluids and suspensions having a solid volume fraction of about 30% or more is of major interest from an industrial point of view. Cement paste and cement grouts for injection grouting appLi.Ations, with water to cement ratios typically in the range of 0.4 and 0.6 - 0.8 by weight, are two examples of industrial fluid systems. Few in-line techniques are available on the market that can be used for these fluid systems and under realistic field conditions. The so-called UVP+PD in-line rheometry method combining the Ultrasound Velocity Profiling (UVP) technique with Pressure Difference (PD) measurements is a promising new tool for industrial appLi.Ations. This paper presents an initial pre-study that aims to demonstrate the feasibility of the UVP+PD method using cement grouts for process monitoring and control of grouting appLi.Ations under realistic field conditions. The UVP+PD method was tested and found successful for continuous in-line measurements of concentrated micro cement-based grouts with water/cement ratios of 0.6 and 0.8. The test set-up consisted of a combination of an experimental .flow loop. and a conventional field grouting rig - UNIGROUT, from Atlas Copco. The rheological properties were determined, directly in-line and the parameters obtained were subsequently compared with off-line measurements using a conventional rotational rheometer.► Cite this publication as follows:
Wiklund J, Rahman M, Hakansson U: In-line rheometry of micro cement based grouts . a promising new industrial application of the ultrasound based UVP+PD method, Appl. Rheol. 22 (2012) 42783.
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 stabiLi.Ation with anti-oxidation packages to allow one to obtain useful data. The time for the sample relaxation from mounting and trimming in the parallel plate geometry of the controlled-stress rheometer prior to initiation of a creep test was also considered. The issue of what stress level to use in the linear viscoelastic region was addressed as was the issue of signal to noise. The creep test was performed within 4 hours for practical use, and the frequency range was extended down 10-4 rad/s. We tested several polyethylene samples as examples taking account of above variables and showed that the data obtained by the creep method overlapped well with low frequency end of the dynamic frequency sweep data. By testing several high molecular weight resins having broad molecular weight distribution and/or long chain branching, we demonstrated the utility of this methodology.► Cite this publication as follows:
Inn Y, Rohlfing DC: Application of Creep Test to Obtain the Linear Viscoelastic Properties at Low Frequency Range for Polyethylene Melts, Appl. Rheol. 22 (2012) 15260.
A high torque vane rheometer is used to measure the yields stress of cement-based materials. It is shown that this apparatus is suitable for the evaluation of the yield stress of various concretes and mortars in the fresh state in comparison with slump tests realized with ASTM Abrams cone. Then, the rheological properties (yield stress and shear flow behaviour) of a homogeneous kaolin clay suspension are studied with the apparatus and favourably compared with other rheometers and geometries.► Cite this publication as follows:
Estelle P, Lanos C: High torque vane rheometer for concrete: principle and validation from rheological measurements, Appl. Rheol. 22 (2012) 12881.
Concentrated gypsum slurries used for wallboard production are studied using shear and elongational rheometers. It is shown that the rheological behavior of different slurry compositions can be sufficiently accurately described in the framework of the Ostwald-de Waele power law, which reproduces both shear and elongational experimemtal data with sufficiently close values of the consistency and flow behavior indexes for each slurry composition studied.► Cite this publication as follows:
Sinha-Ray S, Srikar R, Lee CC, Li A, Yarin AL: Shear and elongational rheology of gypsum slurries, Appl. Rheol. 21 (2011) 63071.
Rheological behaviour of culture broth stands as a fundamental parameter in bioprocess performances because it affects simultaneously the heat and mass transfer as well as the flow pattern. On-line measurements of rheological behaviour are hardly compatible with the operating condition with respect to accurate and stringent conditions imposed by cell culture strategy. Our scientific and technical objectives are (i) to develop and identify an experimental device enabling on-line rheometry and (ii) to discuss and compare on-line and off-line measurements. In this aim, a bioreactor was equipped with a derivation loop including a specific on-line rheometric device as well as additional physical and biological measurements (specific density, mass flow rate, electrical conductivity, pH,pO2 and temperature) during microbial cell cultures. In a first time, friction curves of calibrated ducts were established with Newtonian and non-Newtonian shear-thinning fluids. In a second time, axenic cultures with two microorganisms (bacteria and yeast exhibiting different sizes) were investigated in pure oxidative culture in order to produce biomass under high cell concentrations: ~ 40 to 110 gCDW/l for E. coli (bacteria) and ~ 75 to 105 gCDW/l for Y. lipolytica (yeast). Cell broths exhibited Newtonian behaviour for E. coLi.And shear-thinning behaviour for Y. lipolytica, which were both dependant on biomass concentration. On-line and off-line rheological measurements are consistent for E. coLi.And Y. lipolytica, but significantly differed. On-line estimated viscosity appears higher than off-line apparent viscosity. Several assumptions in relation with microorganism physiology and metabolism (size, morphology, surface properties, concentration, biological activity) could be formulated in agreement with scientific literature. On-line rheology brings new insight to investigate complex interaction between physical and biological phenomena.► Cite this publication as follows:
Manon Y, Anne-Archard D, Uribelarrea J, Molina-Jouve C, Fillaudeau L: Physical and biological study of cell cultures in a bioreactor: on-line and off-line rheological analyses, Appl. Rheol. 21 (2011) 35167.
This work takes a phenomenological approach to modeling the rheology of polymer/clay nanocomposites in (shear rate) γ ≤ 1 / s based on experimental observations [10]. The total stress was divided to three contributions: Matrix stress, σM, inter-particle (matrix/particle) stress, σP, and hydrodynamic stress σH. Based on the superposition of complex viscosities, η*, plotted against strain rate amplitude, γ0ω, at different nonlinear strain amplitudes, a modified Bingham-type constitutive equation proposed by Doiraswamy et. al [16] was used to model σM+σP while σH was modeled by using constitutive equation proposed by Lipscomb et. al [25] for ellipsoidal particles. The comparison between experimental and modeling results showed that steady hydrodynamic stress in simple shear flows scales with complex viscosities in oscillatory experiments when compared at γ = γ0ω. On the basis of this observation, the network-like behavior of the polymer nanocomposite was attributed to retarded chain dynamics as a result of polymer/clay interactions. In order to take into account the thixotropic behavior of network structure, the constitutive equation proposed by Coussot [18] was employed for modeling 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 γ = 0.1 / s.► Cite this publication as follows:
Nazockdast E, Nazockdast H: Rheological Modeling of Polymer/layered silicate Nanocomposites, Appl. Rheol. 21 (2011) 25434.
This paper presents an experimental facility that allows simultaneous viscosimetric and Particle Image Velocimetry measurements on concentrated suspensions in a wide-gap Couette rheometer. The experimental procedure is detailed: the optical characteristics of the index-matched suspension are carefully studied, the bottom end effect on both the viscosimetric measurements and the recorded velocity profiles are analysed. First the experimental procedure is tested on a Newtonian fluid whose viscosity is known. The spatial and time resolutions of our device are shown to be 200 μm and 100 ms. The precision of the local viscosity measurement is evaluated to better than 4 %. Then we show that the device can be used to characterize the rheological behaviour of a 47 %-concentrated suspension of 30 μm spheres. According to the particles large size, the Brownian motion can be neglected. However, colloidal interaction are still noticeable.► Cite this publication as follows:
Blanc F, Peters F, Lemaire E: Particle Image Velocimetry in concentrated suspensions : Application to local rheometry, Appl. Rheol. 21 (2011) 23735.
The effects of particle concentration, particle size and temperature on the shear rheology of suspensions of siLi.A nanoparticles are studied. Sterically or electrostatically stabilized siLi.A nanoparticle dispersions with sizes ranging from 5 - 75 nm and particle volume fractions ranging from 0.22 - 25 % exhibited a constant viscosity within the shear rate range of 1 - 200 s-1. There is a non-linear relationship between the concentration and the viscosity of these dispersions that depends on the radii and surface energy of these nanoparticles.We propose an effective maximum packing fraction model based on the concept of an effective particle radius, which takes into account the thickness of the electrical double layer and the surface coating material. The viscosities of all the dispersions collapse onto a universal curve as a function of the volume fraction normalized by the effective maximum packing fraction.► Cite this publication as follows:
Metin C, Bonnecaze R, Nguyen Q: Shear Rheology of Silica Nanoparticle Dispersions, Appl. Rheol. 21 (2011) 13146.
► Cite this publication as follows:
Kubyshkina G: The 7th International Conference on Mechanics of Time-Dependent Materials, Appl. Rheol. 21 (2011) 48.
The effect of shear viscosity on taste and mouthfeel perception has been extensively studied; however, the effect of extensional viscosity on sensory perception has been mostly neglected. This may be important as in-mouth processing is complex and probably best described as a superposition of shear and extensional flow characteristics. Fluid mechanics researchers interested in separating elastic effects from viscous effects use Boger fluids and this approach was adopted here to investigate the effect of fluid elasticity on sensory perception. For the first time, two food grade Boger fluids based on glucose syrup and aqueous solutions of maltodextrin as solvents and xanthan gum as high molecular weight polymer were formulated. The elasticity of the Boger fluids was characterised in rotational shear rheometry, in a filament break-up device and in microcontraction flow. Saltiness perception and mouthfeel of the Boger fluids and samples corresponding to the respective solvent were analysed. Surprisingly, there were no significant differences. Hypotheses attributing this finding to the intrinsic properties of the samples are discussed. A major study would be required to gain in-depth understanding of the sensory properties of these fluids as their flow properties are very different from typical liquid foods.► Cite this publication as follows:
Koliandris A, Rondeau E, Hewson L, Hort J, Taylor AJ, Cooper-White JJ, Wolf B: Food grade Boger fluids for sensory studies, Appl. Rheol. 21 (2011) 13777.
This article reports viscosity data on a series of colloidal dispersions collected as part of the International Nanofluid Property Benchmark Exercise (INPBE). Data are reported for seven different fluids that include dispersions of metal-oxide nanoparticles in water, and in synthetic oil. These fluids, which are also referred to as 'nanofluids,' are currently being researched for their potential to function as heat transfer fluids. In a recently published paper from the INPBE study, thermal conductivity data from more than 30 laboratories around the world were reported and analyzed. Here, we examine the influence of particle shape and concentration on the viscosity of these same nanofluids and compare data to predictions from classical theories on suspension rheology.► Cite this publication as follows:
Venerus DC, Buongiorno J, Christianson R, Townsend J, Bang I, Chen G, Chung S, Chyu M, Chen H, Ding Y, Dubois F, Dzido G, Funfschilling D, Galand Q, Gao J, Hong H, Horton M, Hu L-W, Iorio CS, Jarzebski AB, Jiang Y, Kabelac S, Kedzierski MA, Kim C, Kim J-H, Kim S, McKrell T, Ni R, Philip J, Prabhat N, Song P, VanVaerenbergh S, Wen D, Witharana S, Zhao X-Z, Zhou S-Q: Viscosity measurements on colloidal dispersions (nanofluids) for heat transfer applications, Appl. Rheol. 20 (2010) 44582.
The effect of classical compatibilizers and siLi.A fillers, which are a new potential type of compatibilizers, on the rheological properties of PP/LCP blends was investigated.The frequency sweep, shear stress growth and stress relaxation upon cessation of steady shear were performed to probe the effect of the interfacial modification and the role of siLi.A, on the rheological behaviour of the blend. It was found that SEBS-g-MA improves the interfacial interaction more than SEBS due to the possible chemical bonding between maleic anhydride groups and LCP chains. The results showed while the hydrophilic siLi.A fills both matrix and the LCP dispersed phases, the hydrophobic siLi.A has some compatibilizing effect on PP/LCP blend samples.► Cite this publication as follows:
Foudazi R, Nazockdast H: Rheology of Polypropylene/Liquid Crystalline Polymer Blends: Effect of Compatibilizer and Silica, Appl. Rheol. 20 (2010) 12218.
Nanoclay dispersions in organic solvents are widely used in cosmetics for a variety of gels and creams, whose properties depend on the powder content and the processing method. The control of the shear applied during processing is therefore essential for achieving the required properties.This study demonstrates the utility of applying rheological measurements for characterizing cosmetic products based on nanoclays and relating their viscoelastic properties to end-use performances. In particular, a rheological characterization of bentonite dispersions in isododecane at different clay content and shear history is presented. For each inorganic content, both mixed samples and samples subjected to several calendering runs were studied. The effect of shear and clay content on the viscoelastic properties was investigated by a combination of oscillatory shear experiments under small-deformation conditions and by X-Ray diffraction. The tested samples showed a gel-like behaviour with a final structure depending on the applied shear stress. By increasing the inorganic content in the dispersion, a reduction in the gel stability to a further shear appLi.Ation was observed. Two models, developed for colloidal gels,were used to fit the rheological results enabling to evaluate the microstructure and the degree of dispersion of the tested samples and to relate the colloidal structure to the elastic properties.► Cite this publication as follows:
Lionetto F, Maffezzoli A: Rheological characterization of concentrarted nanoclay dispersions in an organic solvent, Appl. Rheol. 19 (2009) 23423.
It is observed that, although consisting on very different formulations, the rheological properties of filled polyurethane adhesives may be rescaled onto simple master curves, and described with a small number of parameters: a yield stress, a low frequency elastic modulus and a characteristic time of flow. As a consequence, very simple and quaLi.Ative measurements of their deformations, such as the Dog Tail Test, may be used to deduce these parameters. By comparing the values obtained from Dog Tail Test measurements to well-controlled rheological measurements and to finite element computation, we show that such a simple and quaLi.Ative test may be used as a tool to measure both the yield stress and the elastic modulus of highly viscoelastic systems► Cite this publication as follows:
Lootens D, Jousset P, Dagallier C, Hebraud P, Flatt R: The ''Dog Tail Test'': a quick and dirty measure of yield stress. Application to polyurethane adhesives, Appl. Rheol. 19 (2009) 13726.
In practice, while placing concrete in a formwork by pumping, the pressure generated by the pump is not controlled. In order to enhance the safety on the worksite, and in view of the current economic and ecologic arguments, it would be useful to dispose of an equation able to predict pressure losses based on the rheological properties of the concrete and the pipe configuration. This paper describes the derivation of an extended version of the Poiseuille formula, for shear-thickening materials with a yields stress, described by the modified Bingham equation. This formula is applied to flow-tests with self-compacting concrete. The results prove the appLi.Ability of this extended Poiseuille formula, showing that the flow is occurring in laminar regime, with no significant wall slip.► Cite this publication as follows:
Feys D, Verhoeven R, DeSchutter G: Extension of the Poiseuille formula for shear-thickening materials and application to Self-Compacting Concrete, Appl. Rheol. 18 (2008) 62705.Christophe Ancey
Visco-plastic fluids: from Theory to AppLi.Ation
Appl. Rheol. 18:1 (2008) 48-50 ►
► Cite this publication as follows:
Ancey C: Visco-plastic fluids: from Theory to Application, Appl. Rheol. 18 (2008) 48.
We apply the Landmark Paper Index (LPI), calculate and analyze indices for all papers published in rheological journals (`η-journals') between 1991 and 2007. We discuss the effect of formal criteria on the LPI.► Cite this publication as follows:
Kroger M: Landmark paper index: Application to rheological (η) journals, Appl. Rheol. 17 (2007) 66494.
Self-Compacting Concrete is a new type of concrete which is more liquid compared to traditional concrete and which does not need any form of external compaction. As a result this type of concrete is suitable for a new placing technique: pumping SCC from the bottom in the formwork and letting it rise in the formwork due to the applied pressure. In order to understand the phenomena occurring during pumping operations, the rheological properties of SCC must be investigated and controlled. Tests have been performed with two different rheometers, which are described in this paper. For the Tattersall Mk-II rheometer, a calibration procedure has been worked out to eliminate secondary flows in the rheometer.Test results indicate that SCC is a thixotropic liquid, having a yield stress, showing shear thickening and having varying properties in time due to the occurring chemical reactions. In this paper, the time dependent effects will not be described. When trying to apply a rheological model to the obtained results, only the modified Bingham model seems appropriate. Applying the Bingham model results in the generation of negative yield stresses while the Herschel-Bulkley model has a parameter with a variable dimension and has a major mathematical restriction. The rheological properties of fresh SCC can be described with the modified Bingham model. A suitable parameter to describe shear thickening is defined as the ratio of the second order term in the shear rate of the modified Bingham model to the linear term (= c/μ).► Cite this publication as follows:
Feys D, Verhoeven R, DeSchutter G: Evaluation of time independent rheological models applicable to fresh Self-Compacting Concrete, Appl. Rheol. 17 (2007) 56244.
► Cite this publication as follows:
Gahleitner M: 8th Austrian Polymer Meeting 2006. The Chain of Knowledge. From Catalyst to Application, Appl. Rheol. 17 (2007) 107.
A specific twin channel slit die was used to measure in-line the viscous behaviour of an extruded wheat starch. This allows to put in evidence the influences of temperature, water content and specific mechanical energy (SME). The proposed rheological law permits to satisfactorily predict the viscosity of a wheat starch for any processing condition. Original results are presented for the behaviour of cationic starches obtained by reactive extrusion.► Cite this publication as follows:
Berzin F, Tara A, Tighzert L: In-line measurement of the viscous behaviour of wheat starch during extrusion. Application to starch cationisation., Appl. Rheol. 17 (2007) 21222.
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 pubLi.Ations on the (scientific) community. In opposite to the well known Impact Factor (journal sensitive) or the number of citations (article sensitive, pubLi.Ation year insensitive) the LPI helps to identify established and potential breakthrough contributions by considering the number of citations per year after pubLi.Ation, 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.
► Cite this publication as follows:
Schweizer T: Rheology. Concepts, Methods, and Applications (A. Ya. Malkin, A.I. Isayev), Appl. Rheol. 16 (2006) 240.
Blends of 30-phr siLi.A filled elastomeric chlorinated polyethylene (CPE) and natural rubber (NR) at the blend composition ratio of 80/20 CPE/NR were prepared with various mixing time from 120 to 600 s. Viscoelastic behaviours of cured and uncured blends were determined using two rheometers with different shear modes, i.e., the oscillatory rheometer (Rubber Process Analyser, RPA2000) and the rate-controlled capillary rheometer (Goettfert Rheotester 2000). Results obtained reveal that the viscoelastic behaviour of blends is influenced by the formation of siLi.A transient network, particularly in cured blends. Mixing time affects viscoelastic properties of vulcanised blends to some extent which is due probably to the high extent of thermal degradation, but plays no significant role in viscoelastic properties of unvulcanised blends. The superimposition of oscillatory and steady shear results is possible when the elastic component is eliminated from the results.► Cite this publication as follows:
Phewthongin N, Saeoui P, Sirisinha C: Comparison of Viscoelastic Behaviour in Silica Filled Cured and Uncured cpe/nr Blends with Various Mixing Time, Appl. Rheol. 16 (2006) 182.
► Cite this publication as follows:
Fischer P: Rheometry of Pastes, Suspensions and Granular Materials - Application in Industry and Environment (P. Coussot), Appl. Rheol. 16 (2006) 181.
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.
The propagation of ultrasonic waves in polymers depends on their viscoelastic behaviour and density, resulting significantly affected by phase transitions occurring with changing temperature and pressure or during chemical reactions. Therefore, the appLi.Ation of low intensity ultrasound, acting as a high frequency dynamic mechanical deformation applied to a polymer, can monitor the changes of viscoelastic properties associated with the glass transition, the crystalLi.Ation, the physical or chemical gelation, the crosslinking. Thanks to the non-destructive character (due to the very small deformation amplitude), low intensity ultrasound can be successfully used for polymer characterization. Moreover, this technique has a big potential as a sensor for on-line and in-situ monitoring of production processes for polymers or polymer matrix composites. Recently, in the laboratory of Polymeric Materials of Lecce University a custom made ultrasonic set-up for the characterization of polymeric material, even at high temperatures, has been developed. The ultrasonic equipment is coupled with a rotational rheometer. Ultrasonic waves and shear oscillations at low frequency can be applied simultaneously on the sample, getting information on its viscoelastic behaviour over a wide frequency range. The aim of this paper is to present the potential and reliability of the ultrasonic equipment for the ultrasonic dynamic mechanical analysis (UDMA) of both thermosetting and thermoplastic polymers. Three appLi.Ations of UDMA to different polymeric systems will be reviewed, concerning the cross-linking of a thermosetting resin, the crystalLi.Ation from melt of a semicrystalline polymer and the water sorption in a dry hydrogel film. From the ultrasonic velocity and attenuation measurements, the viscoelastic properties of the tested polymers are evaluated in terms of complex longitudinal modulus and compared with the results of conventional dynamic mechanical analysis, carried out at low frequency.► Cite this publication as follows:
Lionetto F, Montagna F, Maffezzoli A: Ultrasonic Dynamic Mechanical Analysis of Polymers, Appl. Rheol. 15 (2005) 326.
► Cite this publication as follows:
Kroger M: Ferrofluids: Magnetically Controllable Fluids and Their Applications (Stefan Odenbach), Appl. Rheol. 14 (2004) 178.Dr. J.H. Watson
The DiaboLi.Al Case of the Recurring Yield Stress
Appl. Rheol. 14:1 (2004) 40-45 ►
The yield stress has, since its conception, been a source of fierce and often acrimonious debate. This review article deals with the issue, looking at problems related to the meaning of the definition, timescale of the observation, whether the yield stress is a property of concentrated suspensions or is linked to the strength of coherent network structures. We discuss the problematic nature of how to measure the yield stress, directly or indirectly, and examples of the vane geometry are given. Throughout, absolutist and realist theories and evidence are presented and a consensus is finally drawn. Rheologists should embrace the consequences of the absolutist and realist theories and apply them to their everyday world - whatever the timescale!► Cite this publication as follows:
Watson JH: The Diabolical Case of the Recurring Yield Stress, Appl. Rheol. 14 (2004) 40.
► Cite this publication as follows:
Boger DV: Introduction to The Diabolical Case of the Recurring Yield Stress, Appl. Rheol. 14 (2004) 40a.
Rutting is a primary reason of premature deterioration of asphalt highway pavements. Pavements constructed with polymer and other modifiers are showing improved performance. The virgin asphalt and modified asphalt binders and mixes used on several test sections of the I-55 highway rehabiLi.Ation project in northern Mississippi are compared. The laboratory creep compliance data for these binders were measured at low temperatures using a modified test procedure adapted for the Bending Beam Rheometer device. Dynamic Shear Rheometer was used at high service temperatures. The creep compliance data of the binder was used as an input to simulate creep compliance behavior of the mix using a micromechanical model. The field evaluation confirms the relatively poor performance of the virgin asphalt section with respect to rutting, compared to modified binder sections.► Cite this publication as follows:
Uddin W: Viscoelastic Characterization of Polymer-Modified Asphalt Binders of Pavement Applications, Appl. Rheol. 13 (2003) 191.
► Cite this publication as follows:
DeAngelis E: Plasma and Fluid Turbulence:Theory and Modelling (Akira Yoshizawa), Appl. Rheol. 13 (2003) 69.
We present new non-linear data in extension and two different shear histories. These data are used to compare the effectiveness of using exponential shear data and uniaxial extension data to characterise the non-linear response of an industrial LDPE melt with the pom-pom molecular model. We conclude that extension and exponential shear both allow good predictions to be made in simple shear. However, the characterisation spectrum obtained from exponential shear data fails to predict the correct degree of strain hardening at low extension rates. From this study we are able to suggest circumstances under which exponential shear provides a useful characterisation of branched polymer melts.► Cite this publication as follows:
Suneel , Graham RS, McLeish TCB: Characterisation of an Industrial Polymer Melt Through either Uniaxial Extension or Exponential Shear Data: An Application of the Pom-Pom Model, Appl. Rheol. 13 (2003) 19.
The 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 heLi.Al 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 heLi.Al 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.
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.
Due to a number of practical difficulties, both in- and on-line measurements of the rheological properties of complex systems during extrusion are usually performed at the end of the extruder, under very specific experimental conditions. This makes this type of instruments more useful for quality control than for process optimisation, since information about the influence of the geometry and/or processing conditions on the evolution of the material characteristics inside the extruder is not easily gathered. Recently, however, the authors have developed an on-line capillary rheometry system that overcomes most of the existing problems and allows small amounts of sample to be tested in very near real time, along the extruder. The present work aims at illustrating the usefulness of this concept for the study of physical compounding processes and some reactive systems. Two very different systems will be used for that purpose: a reactive extrusion process (the peroxide-induced thermal degradation of polypropylene) and the dispersive mixing involved in the preparation of thermoplastic/carbon fibre composites.► Cite this publication as follows:
Maia JM, Carneiro OS, Machado AV, Covas JA: On-Line Rheometry for Twin-Screw Extrusion (Along the Extruder) and its Applications, Appl. Rheol. 12 (2002) 18.
► Cite this publication as follows:
McKinley GH: 72nd annual meeting of the society of rheology (Hilton Head Island, South Carolina/U.S.A) , Appl. Rheol. 11 (2001) 153.
► 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.
► Cite this publication as follows:
Krusteva ED, Radoslavov SY, Diankov ZI: Modelling the Seepage of Groundwater: Application of the Viscous Analogy, Appl. Rheol. 9 (1999) 165.K Geiger
DiscLi.Ations in Liquid Crystalline Polymer Melts
Appl. Rheol. 6:4 (1996) 172 ►
► Cite this publication as follows:
Geiger K: Disclinations in Liquid Crystalline Polymer Melts, Appl. Rheol. 6 (1996) 172.A Dengel
The Non-Newtonian Flow Behavior of a Lead SiLi.Ate Glass Melt
Appl. Rheol. 4:3 (1994) 133 ►
► Cite this publication as follows:
Dengel A: The Non-Newtonian Flow Behavior of a Lead Silicate Glass Melt, Appl. Rheol. 4 (1994) 133.
► 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.
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