Rheological Behavior of Filled Polymeric Systems I. Yield Stress and Shear-Thinning Effects

A fundamental investigation of the influence of particulate and matrix properties on the shear viscosity, primary normal stress coefficient, dynamic viscosity, and storage modulus of composite systems was undertaken. As expected, all four rheological properties were observed to increase upon addition of solid particulates and some of the composite systems exhibited a yield stress. The present re-search showed that a new equation obtained by a phenomenological modification of the Tanaka and White model allowed the a priori prediction of suspension viscosity for shear-thinning systems as a function of matrix properties, volume fraction of particulates, and shear rate. It also provided the flexibility of describing suspension viscosity of systems exhibiting an apparent yield stress. Investigation of the other rheological properties showed that a form of the Kitano et al. expression could describe the relative primary normal stress coefficient and the relative storage modulus; whereas, a form of the Chong et al. expression could describe the relative dynamic viscosity of the various composite systems.