The viscoelastic properties of concentrated suspensions

The viscoelastic properties of concentrated, well dispersed, sterically stabilised polymethyl methacrylate particles were studied using a specially developed low frequency, controlled shear stress rheometer. The experimental results show a well defined viscoelastic transition over a narrow frequency range. Evidence is produced to show that the particles act as hard, non-interacting spheres. It is argued that the transition represents a change from a randomly packed assemblage with particle motion dominated by Browniandiffusion processes to a lower packing density shear flow regime.