ON THE RHEOLOGY OF FILLED POLYMERS

This paper develops a rheological model for flow of polymer compounds highly filled by small interacting (attractive) particles. The properties of the particle phase in the compound are described by introducing a viscoelastic “particle mode” with an additional kinetic equation which describes the processes of rupture and restoration of flocs of particles. The elastic deformations in the particle mode are assumed to be small enough to consider the geometrical nonlinearities as second-order effects. The rheological behavior of the polymer matrix is modeled by means of nonlinear viscoelasticity, as in the case of pure polymer melts. It was shown that all the basic features of the yield-like and thixotropic behavior of the filled polymer compounds, including the appearance of yield values in steady state flows, stress overshoots in start up flows and effects of “frozen memory” during relaxation could be described by this approach without using the mathematical yield criteria. Some preliminary comparisons of the theory with steady state data are also demonstrated. © 1990, The Society of Rheology. All Rights Reserved.