The effect of particle concentration on the rheology of polydimethylsiloxane filled with fumed silica

摘要

AbstractThe effects of particle concentration on the shear‐rate‐dependent viscosity, stress relaxation, and stress growth function were investigated for various molecular weight polydimethylsiloxane (PDMS) fluids filled with colloidal fumed silica. Shear‐rate‐dependent stress relaxation was observed for all dispersions, and a significant stress growth overshoot was observed when the PDMS molecular weight was just greater than the entanglement molecular weight. The rate of stress—relaxation and the type of stress growth are primarily determined by the previous shear rate history and the PDMS molecular weight, while particle concentration only affects the quantitative details of the filled fluid's rheology. The observed effects of particle concentration are consistent with a molecular deformation process, where the silica particles interact via the entanglements of the polymer adsorbed on the surface of the fum