Shear-dependent Viscosity Research Articles

Influence of molecular weight, temperature, and extensional rheology on melt blowing process stability for linear isotactic polypropylene

In this work, three linear isotactic polypropylenes with different weight-average molecular weights, Mw, and comparable polydispersities were used to produce nonwovens by melt blowing technology at two different temperatures, T. The air/polymer flow rate was changed to maintain the same average fiber diameter, resulting in a different broadness of fiber diameter distribution, which was quantified by the coefficient of variation, CV. The elasticity of the material was evaluated by the reptation-mode relaxation time, λ1, and the Rouse-mode reorientation time, λ2, determined from the deformation rate dependent shear viscosity data. Extensional rheology was evaluated using uniaxial extensional viscosity measured over a very wide range of strain rates (2 × 104 s−1–2 × 106 s−1) using entrance pressure drop and Gibson methods. An obtained plateau value of uniaxial extensional viscosity at the highest extensional strain rates, ηE,∞ (normalized by the three times zero-shear rate viscosity, η0), and the minimum uniaxial extensional viscosity, ηE,min, were related to Mw and T using simple equations. It has been found that the stability of fiber production captured by CV depends exclusively on the extensional properties of the polypropylene melts, namely, ηE,U,∞3η0 and ηE,U,min. These findings are important especially with regard to the stable production of polymeric nanofibers by melt blowing technology.

Investigation of Rheological Behavior of Untreated and Microwave-Assisted Alkaline Pretreated Sugarcane Straw for Biofuel Production

Biomass slurries, such as those subjected to microwave-assisted alkaline (MAA) pretreatment, will become common substrates for the production of biofuels in the future. While the rheology of acid and ionic liquid pretreated biomass is known, the rheology of alkaline pretreated biomass is not yet reported; hence, the goal of this study was to establish the rheological characteristics of untreated and MAA pretreated sugarcane straw (SC). Using rotational rheometry and rheological models, the rheology of SC slurries was assessed as a function of particle size and insoluble solids concentration. In the range of 5–17% insoluble solids concentration, the slurries were consistently pseudo-plastic (n = 0.33 ± 0.02), possessed yield stress with their flow accurately described by the Casson rheological model (R2 = 0.98–0.99). The apparent viscosity and yield stress increased by two orders of magnitude with an increase in insoluble solids concentration. Essentially, MAA pretreated slurries exhibited significantly higher values of apparent viscosity and yield stress than the untreated ones, in the range of 55–80% and 21–63% for particle sizes of < 63 µm (P63) and 90–180 µm (P90), respectively. Pretreated P63 samples exhibited higher apparent viscosity and yield stress than the P90. On the other hand, for untreated samples, P63 samples had a reduced apparent viscosity than P90 samples. The results of this study definitively reveal that MAA significantly increases the shear rate dependent shear viscosity values along with the yield stress of biomass slurries. This will, therefore, serve as a benchmark for characterizing other MAA pretreated biomass slurries to guide the design of industrial-scale production equipment.

Printability of a Cellulose Derivative for Extrusion-Based 3D Printing: The Application on a Biodegradable Support Material

Support material plays a leading role in the application of 3D printing to avoid deformation and enhance stability. This study aimed to fabricate the support structure by using hydroxypropyl methylcellulose (HPMC), which has advantages over conventional material such as low cost, low printable temperature, and high biodegradability. Once dissolved in water over gelling temperature, the HPMC based hydrogel exhibited shear-thinning behavior with decreasing apparent viscosity values at higher shear rates. The shear-dependent viscosity makes the HPMC hydrogel extrudable throughout the printing process and the printed structure stable enough without deformation. As concentration increased, apparent viscosity and storage modulus both subsequently increased. These rheological properties indicated that the concentration of HPMC K4M hydrogel significantly influenced the printability and shape retention ability, which is associated with the mechanical strength of printed filaments. The highest concentration, 12% w/v, should have the best ability to hold the printed shape over time due to the highest G' and lowest loss tangent. The printability test also showed that K4M 12% w/v could be printed into different fill density (100%, 75%, and 50%) with different patterns, i.e., rectilinear and Hilbert curve. The selection of fill density and pattern both have an effect on surface roughness and porosity. The printed support material was compatible with acrylonitrile butadiene styrene (ABS), which is the material to fabricate the main structure for 3D printing. The support material made of HPMC can be easily removed by peeling off from the main structure without visible residual.

A 4D flow MRI evaluation of the impact of shear-dependent fluid viscosity on in vitro Fontan circulation flow.

The Fontan procedure for univentricular heart defects creates a nonphysiologic circulation where systemic venous blood drains directly into the pulmonary arteries, leading to multiorgan dysfunction secondary to chronic low-shear nonpulsatile pulmonary blood flow and central venous hypertension. Although blood viscosity increases exponentially in this low-shear environment, the role of shear-dependent ("non-Newtonian") blood viscosity in this pathophysiology is unclear. We studied three-dimensional (3D)-printed Fontan models in an in vitro flow loop with a Philips 3-T magnetic resonance imaging (MRI) scanner. A 4D flow phase-contrast sequence was used to acquire a time-varying 3D velocity field for each experimental condition. On the basis of blood viscosity of a cohort of patients who had undergone the Fontan procedure, it was decided to use 0.04% xanthan gum as a non-Newtonian blood analog; 45% glycerol was used as a Newtonian control fluid. MRI data were analyzed using GTFlow and MATLAB software. The primary outcome, power loss, was significantly higher with the Newtonian fluid [14.8 (13.3, 16.4) vs. 8.1 (6.4, 9.8)%, medians with 95% confidence interval, P < 0.0001]. The Newtonian fluid also demonstrated marginally higher right pulmonary artery flow, marginally lower shear stress, and a trend toward higher caval flow mixing. Outcomes were modulated by Fontan model complexity, cardiac output, and caval flow ratio. Vortexes, helical flow, and stagnant flow were more prevalent with the non-Newtonian fluid. Our data demonstrate that shear-dependent viscosity significantly alters qualitative flow patterns, power loss, pulmonary flow distribution, shear stress, and caval flow mixing in synthetic models of the Fontan circulation. Potential clinical implications include effects on exercise capacity, ventilation-perfusion matching, risk of pulmonary arteriovenous malformations, and risk of thromboembolism.NEW & NOTEWORTHY Although blood viscosity increases exponentially in low-shear environments, the role of shear-dependent ("non-Newtonian") blood viscosity in the pathophysiology of the low-shear Fontan circulation is unclear. We demonstrate that shear-dependent viscosity significantly alters qualitative flow patterns, power loss, pulmonary flow distribution, shear stress, and caval flow mixing in synthetic models of the Fontan circulation. Potential clinical implications include effects on exercise capacity, ventilation-perfusion matching, risk of pulmonary arteriovenous malformations, and risk of thromboembolism.

Lubrication Approximation for Fluids with Shear-Dependent Viscosity

We present dimensionally reduced Reynolds type equations for steady lubricating flows of incompressible non-Newtonian fluids with shear-dependent viscosity by employing a rigorous perturbation analysis on the governing equations of motion. Our analysis shows that, depending on the strength of the power-law character of the fluid, the novel equation can either present itself as a higher-order correction to the classical Reynolds equation or as a completely new nonlinear Reynolds type equation. Both equations are applied to two classic problems: the flow between a rolling rigid cylinder and a rigid plane and the flow in an eccentric journal bearing.

Rheology and sheet extrusion of Novatein thermoplastic protein/polybutylene adipate‐co‐terephthalate blends

ABSTRACTNovatein is a thermoplastic polymer made from blood meal proteins, but it has rheological properties very different from commodity thermoplastics. Capillary rheometry revealed an apparent time dependent shear viscosity for Novatein, evident from a decreasing pressure drop over time, measured at constant shear rate. However, blending with polybutylene adipate‐co‐terephthalate (PBAT) reduced the time dependence for uncompatibilized blends and virtually eliminated time dependence for compatibilized blends containing 30 wt % PBAT. Novatein's extensional viscosity is three orders of magnitude more than its shear viscosity and explained the difficulty in sheet extrusion. In contrast, 30% compatibilized blends had an extensional viscosity similar to neat PBAT and was also the only blend that could be successfully sheet extruded. Although uncompatibilized blends at the same or lower PBAT content also had a lower extensional viscosity, they could not be sheet extruded and the difference was the 30% compatibilized blends had a fine PBAT phase structure (co‐continuous in this case), which was sufficiently adhered to the Novatein phase. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47977.

Shear-thickening fluids in biologically relevant agents

BACKGROUND:The rheology of shear thickening fluids is well characterized for many physical applications, however the literature surrounding biologically or cryobiologically compatible shear thickening fluids is less well understood.OBJECTIVE:This study examined fluids consisting of corn-derived hydroxyethyl starch with a variety of sugars and cryoprotectants to characterize their shear-rate viscosity relationship. The objective was to establish if cryobiologically relevant materials could be used to afford biologics protection through shear-thickening.RESULTS:Fluids consisting of 50% hydroxyethyl starch by weight exhibited shear thickening with a variety of cryoprotectants. Lowering the temperature of the fluid both reduced critical shear rates and enhanced thickening magnitude. Starch derived from corn, wheat, and rice all exhibited non-Newtonian shear-dependent viscosity behaviour at 50% by weight in water. Between the starch sources however, the shear-rate viscosity relationship varied widely, with wheat-derived starch shear thinning, and the remaining starches forming shear thickening fluids. Different starch sources had different baseline viscosities, critical shear rates, and rates of viscosity increase.CONCLUSIONS: This study established that shear thickening is compatible with cryobiologically relevant agents, particularly so at lower temperatures. This forms the basis for harnessing these phenomena in biological processes such as cryopreservation.

Shear stress relaxation and diffusion in simple liquids by molecular dynamics simulations: Analytic expressions and paths to viscosity.

The results are reported of an equilibrium molecular dynamics simulation study of the shear viscosity, η, and self-diffusion coefficient, D, of the Lennard-Jones liquid using the Green-Kubo (GK) method. Semiempirical analytic expressions for both GK time correlation functions were fitted to the simulation data and used to derive analytic expressions for the time dependent diffusion coefficient and shear viscosity, and also the correlation function frequency transforms. In the case of the shear viscosity for a state point near the triple point, a sech function was found to fit the correlation function significantly better than a gaussian in the ballistic short time regime. A reformulation of the shear GK formula in terms of a time series of time integrals ("viscuits") and contributions to the viscosity from components based on the initial stress ("visclets") enable the GK expressions to be recast in terms of probability distributions which could be used in coarse grained stochastic models of nanoscale flow. The visclet treatment shows that stress relaxation is statistically independent of the initial stress for equilibrium and metastable liquids, suggesting that shear stress relaxation in liquids is diffusion controlled. By contrast, the velocity autocorrelation function is sensitive to the initial velocity. Weak oscillations and a plateau at intermediate times originate to a greater extent from the high velocity tail of the Maxwell-Boltzmann velocity distribution. Simple approximate analytic expressions for the mean square displacement and the self Van Hove correlation function are also derived.

Influence of long chain branching on fiber diameter distribution for polypropylene nonwovens produced by melt blown process

In this work, linear isotactic polypropylene (L-PP) and long-chain branched polypropylene (LCB-PP) miscible blend, both having comparable weight average molecular weight, zero-shear viscosity, and polydispersity index, were used to produce nonwovens via melt blown technology in order to understand the role of long chain branching in the fiber diameter distribution. Basic morphological characteristics of produced nonwoven samples have been determined using digital image analysis of scanning electron microscope images considering different magnifications to capture nanofibers as well as microfibers. At the same air flow rate, polymer flow rate, and temperature, the average fiber diameters were the same, 1.6 μm, but the coefficient of variation, CV, was greater for the linear PP than for the blend. Material elasticity was assessed by reptation-mode relaxation time, λ, determined by fitting of deformation rate dependent shear viscosity by Cross and Carreau-Yasuda models as well as via fitting of frequency dependent loss and storage moduli master curve by a two-mode Maxwell model. It was found that λ is higher for LCB-PP in comparison with L-PP and the Cross model gives a meaningful relaxation time while the Carreau-Yasuda model does not despite giving a better numerical fit. Extensional rheology was assessed by the strain rate dependent uniaxial extensional viscosity (estimated from the entrance pressure drop using the Gibson method). The infinite shear to zero-shear shear viscosity ratio η∞/η0 (obtained directly from the shear viscosity data measured in a very wide shear rate range) was shown to be proportional to the maximum normalized extensional viscosity at very high extensional strain rates, ηE,∞/(3η0). η∞/η0 was related to temperature and basic molecular characteristics of given polymers via simple equation. It was observed that extensional viscosity for both samples first decreases with increased extensional strain rate to its minimum value at 200 000–400 000 1/s and then increases to plateau value, ηE,∞ (corresponding to the maximum chain stretch) at about 2 ⋅ 106 1/s. At low deformation rates, extensional viscosity is higher for LCB-PP in comparison with L-PP, but the trend is switched at very high deformation rates; ηE,∞ (and also ηE,∞/3η0) becomes lower for LCB-PP in comparison with L-PP. These results suggest that high stability of LCB-PP blend can be explained by its higher stretchability at very high deformation rates (occurring at the die exit where an intensive fiber attenuation takes the place) and its lower stretchability at medium and low deformation rates, at which melt/air inertia driven bending instability called whipping occurs.

Three-Dimensional, Non-Isothermal Simulations of the Effect of Speed Ratio in Partially-Filled Rubber Mixing

Abstract Three-dimensional, transient, non-isothermal calculations have been carried out using a commercial computational fluid dynamics (CFD) software in a two-wing rotor-equipped chamber partially-filled (75% fill factor) with rubber, to analyze the mixing efficiency for three different rotor speed ratios of 1, 1.125 and 1.5. The moving mesh technique has been used to incorporate the motion of the rotors. The Eulerian based volume of fluid (VOF) method has been used to track the interface between the two fluids, which are rubber and air. To assign the highly viscous and non-Newtonian properties of rubber, the Carreau-Yasuda model along with an exact Arrhenius formulation that accounts for the shear and temperature dependent viscosity, has been used here. Governing equations including the continuity, momentum and energy equations have been solved to characterize the flow field and various mixing parameters. Eulerian-based fields such as velocity magnitude, viscous heat generation, and average temperature and viscosity are compared between cases with different speed ratios. Dispersive and distributive mixing behaviour are assessed through a Lagrangian approach that tracks the paths of a set of massless particles. Statistical quantities such as cumulative distribution of maximum shear stress, cluster distribution index, and axial and inter-chamber particle transfer rates are calculated and presented as well. Results showed that the speed ratio of 1.5 displayed the best dispersive and distributive mixing characteristics in comparison to the other cases.

On Navier–Stokes–Korteweg and Euler–Korteweg Systems: Application to Quantum Fluids Models

In this paper, the main objective is to generalize to the Navier-Stokes-Korteweg (with density dependent viscosities satisfying the BD relation) and Euler-Korteweg systems a recent relative entropy [proposed by D. Bresch, P. Noble and J.–P. Vila, (2016)] introduced for the compressible Navier-Stokes equations with a linear density dependent shear viscosity and a zero bulk viscosity. As a concrete application, this helps to justify mathematically the convergence between global weak solutions of the quantum Navier-Stokes system [recently obtained by I. Lacroix-Violet and A. Vasseur (2016)] and dissipative solutions of the quantum Euler system when the viscosity coefficient tends to zero. This selects a dissipative solution as the limit of a viscous system. Our results are based on the fact that Euler-Korteweg systems and corresponding Navier–Stokes-Korteweg systems can be reformu-lated through an augmented system as the compressible Navier-Stokes system with density dependent viscosities satisfying the BD algebraic relation. This was also observed recently [by D. Bresch, F. Couderc, P. Noble and J.–P. Vila, (2016)] for the Euler-Korteweg system. As a by-product of our analysis, we show that this augmented formulation helps to define relative entropy estimates for the Euler-Korteweg systems in a simplest way compared to recent works [See D. Donatelli, E. Feireisl, P. Marcati (2015) and J. Giesselmann, C. Lattanzio, A.-E. Tzavaras (2017)] and with less hypothesis required on the capillary coefficient: no concavity assumption needed in our result.

A discussion of Arana, A., Larrañaga, J., &amp; Ulacia, I. (2019). Partial EHL friction coefficient model to predict power losses in cylindrical gears. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, Vol. 233(2) 303–316

There is presently a heated debate within the field of elastohydrodynamic lubrication (EHL). Some have attributed this to a controversy regarding the shear dependence of viscosity. However, the real nature of the debate is, as it has been for more than 40 years, whether or not to correctly describe the piezoviscous effect. If real pressure dependence of viscosity were to be employed in all EHL analyses, then the true nature of shear dependence would become apparent and the debate would end.

Effects of shear-dependent viscosity and hematocrit on blood flow

In this paper, we have proposed a new non-linear constitutive model for blood with a viscosity which depends on the shear rate and the volume fraction of red blood cells or RBCs (hematocrit). The viscosity correlation is obtained from the experimental data reported in the literature. The governing equations for flow between two flat plates are made dimensionless and solved numerically. A parametric study is performed to study the effect of the four non-dimensional numbers K1 (a relative measure of the pressure gradient to viscous forces), K2 (a relative measure of gravitational force to pressure gradient in the direction of the gravity), N (dimensionless average hematocrit of blood), and ϕm (maximum packing fraction of RBCs). The results show good qualitative agreement with other studies.

Rotational and axial flow of pseudoplastic fluids

Effects of a controllable axial flow on the stability of rotational flow of pseudoplastic fluids in the gap between concentric cylinders are studied. It is assumed that the outer cylinder is fixed while the inner one has simultaneous and independent rotational and translational motions. The fluid follows the Carreau model and mixed boundary conditions are imposed. The four-dimensional low-order dynamical system resulting from Galerkin projection of the conservation of mass and momentum equations includes highly non-linear terms in the velocity components originating from the shear-dependent viscosity. In the absence of the axial flow as the pseudoplasticity effect increases, the critical Taylor number at which the rotational flow loses its stability to the vortex structure decreases. The emergence of the vortices corresponds to the onset of a supercritical bifurcation which is also seen in the flow of a Newtonian fluid in rotation. The existence of an axial flow, induced by the translational motion of the inner cylinder, appears to further advance the emergence of the vortex flow. Complete flow analysis together with viscosity maps are given for the entire flow field.

Influence of temperature and alkyl chain length on physicochemical properties of trihexyl- and trioctylammonium based protic ionic liquids

A series of trialkylammonium cation and carboxylate anion based room temperature protic ionic liquids (PILs) were synthesized by varying cation alkyl chain length to hexyl, octyl and anion chain length to butanoate, hexanoate, and octanoate. The corresponding ILs are named as trihexylammonium butanoate ([THA][But]), trihexylammonium hexanoate ([THA][Hex]), trihexylammonium octonoate ([THA][Oct]), trioctylammonium butanoate ([TOA][But]), trioctylammonium hexanoate ([TOA][Hex]), and trioctylammonium octonoate ([TOA][Oct]). The thermophysical properties such as density (ρ), speed of sound (u), viscosity (η) and refractive index (nD) were measured over a wide temperature range. The calculated parameters from experimental data such as thermal expansion coefficient, isentropic compressibility decreased linearly with the number of carbon atoms in cation or anion, whereas they increased with the temperature. Thermogravimetric analysis revealed an increase in the thermal stability of the ILs with the increase in total chain length. The shear-dependent viscosity measurements suggest that all the studied PILs showed fluid nature and Newtonian behavior at 298.15 K. The effect of alkyl chain length of cation or anion and temperature on the physicochemical properties were discussed with respect to the structure of ILs and in correlation with the reported structurally similar ILs.

Novel Endotype Xanthanase from Xanthan-Degrading Microbacterium sp. Strain XT11.

Under general aqueous conditions, xanthan appears in an ordered conformation, which makes its backbone largely resistant to degradation by known cellulases. Therefore, the xanthan degradation mechanism is still unclear because of the lack of an efficient hydrolase. Here, we report the catalytic properties of MiXen, a xanthan-degrading enzyme identified from the genus Microbacterium MiXen is a 952-amino-acid protein that is unique to strain XT11. Both the sequence and structural features suggested that MiXen belongs to a new branch of the GH9 family and has a multimodular structure in which a catalytic (α/α)6 barrel is flanked by an N-terminal Ig-like domain and by a C-terminal domain that has very few homologues in sequence databases and functions as a carbohydrate-binding module (CBM). Based on circular dichroism, shear-dependent viscosity, and reducing sugar and gel permeation chromatography analysis, we demonstrated that recombinant MiXen efficiently and randomly cleaved glucosidic bonds within the highly ordered xanthan substrate. A MiXen mutant free of the C-terminal CBM domain partially lost its xanthan-hydrolyzing ability because of decreased affinity toward xanthan, indicating the CBM domain assisted MiXen in hydrolyzing highly ordered xanthan via recognizing and binding to the substrate. Furthermore, side chain substituents and the terminal mannosyl residue significantly influenced the activity of MiXen via the formation of barriers to enzymolysis. Overall, the results of this study provide insight into the hydrolysis mechanism and enzymatic properties of a novel endotype xanthanase that will benefit future applications.IMPORTANCE This work characterized a novel endotype xanthanase, MiXen, and elucidated that the C-terminal carbohydrate-binding module of MiXen could drastically enhance the hydrolysis activity of the enzyme toward highly ordered xanthan. Both the sequence and structural analysis demonstrated that the catalytic domain and carbohydrate-binding module of MiXen belong to the novel branch of the GH9 family and CBMs, respectively. This xanthan cleaver can help further reveal the enzymolysis mechanism of xanthan and provide an efficient tool for the production of molecular modified xanthan with new physicochemical and physiological functions.

On the existence, uniqueness and regularity of solutions for a class of micropolar fluids with shear dependent viscosities

On the existence, uniqueness and regularity of solutions for a class of micropolar fluids with shear dependent viscosities

Non-Newtonian fluid–structure interactions: Static response of a microchannel due to internal flow of a power-law fluid

We study fluid–structure interactions (FSIs) in a long and shallow microchannel, conveying a non-Newtonian fluid, at steady state. The microchannel has a linearly elastic and compliant top wall, while its three other walls are rigid. The fluid flowing inside the microchannel has a shear-dependent viscosity described by the power-law rheological model. We employ lubrication theory to solve for the flow problem inside the long and shallow microchannel. For the structural problem, we employ two plate theories, namely Kirchhoff–Love theory of thin plates and Reissner–Mindlin first-order shear deformation theory. The hydrodynamic pressure couples the flow and deformation problem by acting as a distributed load onto the soft top wall. Within our perturbative (lubrication theory) approach, we determine the relationship between the flow rate and the pressure gradient, which is a nonlinear first-order ordinary differential equation for the pressure. From the solution of this differential equation, all other quantities of interest in non-Newtonian microchannel FSIs follow. Through illustrative examples, we show the effect of FSI coupling strength and the plate thickness on the pressure drop across the microchannel. Through direct numerical simulation of non-Newtonian microchannel FSIs using commercial computational engineering tools, we benchmark the prediction from our mathematical theory for the flow rate–pressure drop relation and the structural deformation profile of the top wall. In doing so, we also establish the limits of applicability of our perturbative theory.

Vortex breakdown in swirling pipe flow of fluids with shear-dependent viscosity

Laminar pipe flow with a controllable wall swirl has been studied both numerically and experimentally to explore the behavior of inelastic shear-dependent fluids. The pipe consists of two smoothly joined sections that can be rotated independently about the same axis. The circumstance of flow entering a stationary pipe from a rotating pipe (decaying swirl) has been investigated. Numerical parametric studies using both a power-law model and a simplified Carreau model are conducted to investigate the effect of shear-thinning and shear-thickening on the flow structure and the critical swirl ratio required to induce the breakdown at a range of Reynolds numbers. A new method of scaling (i.e., a new Reynolds number) is presented that accounts for the shear-dependent viscosity. Using this Reynolds number, the data for all fluids (shear-thickening, Newtonian, and shear-thinning) approximately collapses. Experimental visualisations using an aqueous solution of xantham gum confirm the conclusions drawn from the numerical results.

Oscillatory and steady shear rheological properties of aqueous polyacrylamide solutions

Abstract Dynamic and steady shear data representing the flow behaviour of aqueous solutions of Polyacrylamide, in the concentration range of 0.25–0.6% wt./vol. and temperature range of 5–45 °C, have been reported. Maxwell model, Carreau model and power law model were used to represent the present experimental data. Rheological parameter such as fluid relaxation time (λ), representative of fluid elasticity, was evaluated by fitting the oscillatory shear data to the four element Maxwell model. Other rheological parameters such as flow behaviour index (n) and flow consistency index (K) were evaluated by fitting the steady shear data to the power law model in the relevant shear rate range. The shear dependent viscosity data are well represented by Carreau model. Predictive equations for λ, n and K are proposed by incorporating the combined effect of temperature and concentration. Presented data could be of great use in various engineering applications such as enhanced oil recovery.