Viscoelastic behavior of concentrated spherical suspensions

Abstract

Experimental results on the linear viscoelastic behavior of concentrated suspensions are presented. The materials studies were prepared by dispersing submicron silica spheres at volume fractions φ ranging from 0.3 to 0.6, in a highly viscous liquid. The response to oscillatory shearing was determined over a wide range of frequency, ω. The zero frequency viscosity η0 and the limiting high‐frequency viscosity η’∞ for all particle radii studied were essentially identical to results previously obtained for suspensions having hard sphere interactions. In this range of concentrations, the frequency dependence of the dynamic moduli, G’ and G‘−ωη’∞, appears to be described by universal functions of ωτw where τw is the mean longest relaxation time proportional to a characteristic (Peclet) time defined as τp=a2/6Ds(φ). Herein a denotes the particle radius and Ds(φ) is a φ dependent short‐time self‐diffusion constant. We also found that at sufficiently high frequencies, G’ has a plateau, G∞, that is given by kT/a3 t...