Elastic-Like and Viscous-Like Components of the Shear Viscosity for Nearly Hard Sphere, Brownian Suspensions
The shear properties of Brownian, rigid spheres consisting of sterically stabilized, crosslinked polymethylmethacrylate (PMMA) particles were studied in suspension. Three different volume fractions were used to carry out this study. The suspensions' elastic-like and viscous-like components of the shear stress were measured by a recently developed technique utilizing cessation of steady shear. The elastic-like viscosity component, or the amount of stress retained at the instant of cessation divided by the shear rate, due to Brownian and possible interparticle forces, decreased in magnitude over the entire range of shear rates used (shear thinning). The decay of the elastic-like stress with time after cessation of flow was also analysed and found to fit a power law relation. The viscous-like component, or the amount of stress lost at the instant of cessation divided by the shear rate, is related to hydrodynamic interactions between and drag on particles and remained essentially constant with shear rate. These data are the first of this kind gathered for a model hard sphere system (i.e., mechanical means) and agrees well with results of Bender and Wagner (J. Colloid Interface Sci. 172, 171 (1995) who used an optical technique.
Kaffashi
B
Department of Chemical Engineering, The University of Queensland, Brisbane, Queensland, 4072, Australia
O'Brien
VT
Mackay
ME
Underwood
SM