Concentration Reduction and Dilatant Flow Behavior in Suspensions of Hardened Human Red Cells

The steady shear viscosity η(k) and the stress decay function \documentclass{article}\pagestyle{empty}\begin{document}$ \tilde \eta \left({t,k} \right)$\end{document} (the shear stress divided by the rate of shear k after cessation of steady shear flow) were measured for concentrated solutions of polystyrene in diethyl phthalate. Ranges of molecular weight M and concentration c were 7.10 × 105 to 7.62 × 106 and 0.112–0.329 g/cm3, respectively. Measurements were performed with a rheometer of the cone‐and‐plate type in the range 10−4 < k < 1 sec−1. The Cox–Merz relation η(k) = |η*(ω)|ω=k was tested with the experimental result (|*(ω)| is the magnitude of the complex viscosity). It was found to be applicable to solutions of relatively low M or c but not to those of high M and c. For the latter η(k) began to decrease at a lower rate of shear than |η*(ω)|ω=k did; the Cox–Merz law underestimated the effect of rate of shear. The stress decay function was assumed to have a functional form \documentclass{article}\pagestyle{empty}\begin{document}$\tilde \eta \left( {t,k} \right) = \sum {\eta _p \left( k \right)e^{ - t/\tau p\left( k \right)} } $\end{document} where τ1 > τ2 > …, and the values of τ1, τ2 η1 and η2 were determined for some solutions. The relaxation times τ1 and τ2 were found to be independent of k and equal to the relaxation times of linear viscoelasticity. At the limit of k → 0, η1 and η2 were approximately 60 and 20–30%, respectively, of η and the non‐Newtonian behavior was due to large decreases of η1 and η2 with increasing k. It was shown that η1(k) may be evaluated from the relaxation strength G1(s) for the longest relaxation time of the strain‐dependent relaxation modulus with a constitutive model for relatively high c–M systems as well as for low c–M systems.

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Mechanisms and equations for shear thinning and thickening in dispersions

Chaffey

1977

Colloid Polymer Sci

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Concentration Reduction and Dilatant Flow Behavior in Suspensions of Hardened Human Red Cells

Cited by 6 publications

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Rheology of fiber‐ or flake‐filled plastics

Rheology of fiber‐ or flake‐filled plastics

Nonlinear viscoelasticity of polystyrene solutions. II. Non‐Newtonian viscosity

Mechanisms and equations for shear thinning and thickening in dispersions

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