Theoretical Approaches to the Rheology of Concentrated Dispersions

Abstract

Suspensions of submicron particles in a liquid respond to flow in a variety of ways depending on the size, concentration, and shape of the particles and the nature and magnitude of the interparticle potentials. The most dramatic phenomena occur when one of the interparticle forces dominates, e.g., strong van der Waals forces for aqueous latices at high ionic strengths¹ or carbon black particles in mineral oil², long range electrostatic repulsions for colloidal crystals^3,4, and the interactions between adsorbed polymer layers in sterically stabilized suspensions near closest packing^5,6. Even with hard sphere interactions though, the rheology is significantly shear-thinning at moderate concentrations^7,8. In each case the non-Newtonian phenomena, whether elastic or pseudoplastic, derive from many-body interactions involving both hydrodynamic and interparticle forces.