Viscoelastic properties of concentrated shear-thickening dispersions

The viscoelastic properties of electrostatically stabilized concd. dispersions of silica and of glass particles in a glycerol/water mixt. were studied by oscillatory shear measurements. These dispersions are shear-thickening in steady flow. At most frequencies, the loss modulus dominates the storage modulus. At certain crit. combinations of deformation amplitude and frequency the response signal becomes distorted, contg. higher harmonics. This phenomenon can be ascribed to flow blockage, closely related to shear thickening in steady shear flow. When plotting the crit. deformation against the frequency, 3 different regions can be detected. At low frequencies, there is the steady shear flow limit, at intermediate frequencies double-layer overlap cause nonlinearity in the response signal, and at high frequencies there is a region where the crit. deformation for flow blockage is a system-dependent function of the frequency, but is independent of the vol. fraction. The magnitudes of the storage moduli are in reasonable agreement with theor. predictions. [on SciFinder (R)