Investigating Linear and Nonlinear Viscoelastic Behavior Using Model Silica-Particle-Filled Polybutadiene

Abstract

We explore filler reinforcement (i.e., increase of elastic modulus G‘ due to incorporation of fillers) and Payne effect (i.e., decrease of G‘ at large strain amplitudes) in terms of the matrix molecular weight, filler loading, and time scales used to probe the viscoelasticity of filled melts. Use of monodisperse non-cross-linked 1,4-polybutadiene (PBD) along with a silica filler allows illustration of different mechanisms of filler reinforcement in the elastic and liquid regimes. The greater filler reinforcement for matrices of higher molecular weight indicates the filler association through chain adsorption and bridging. The role of matrix-mediated filler−filler interactions is explicitly illustrated in terms of the increased elastic modulus in the terminal region due to replacement a fraction of the matrix chains with longer chains of the same kind. The Payne effect is seen to be time-dependent and comprised of an instantly recoverable and a slowly recovering component. Measuring G‘ at both high and low...