The non‐linear viscoelastic properties of molten polymers and concentrated solutions

Abstract

AbstractFor polymer melts and concentrated solutions highly nonlinear effects dominate all aspects of both the transient and steady state mechanical behavior. The first part of this paper will review the salient features of the experimental results and focus attention on those common features which should be understood in a coherent manner. The various constitutive equations, especially the integral representations that have been proposed to describe polymer melts will also be discussed. They fall roughly into three classes: those where the relaxation function depends on the deformation rate, deformation, or stress history. Evidence will be presented which indicates that the stress history rather than the deformation history may be the more relevant variable to account for the non‐linearities. The last part of the paper will briefly review the theories that have been proposed to understand the mechanism for non‐linear behavior at the microscopic level and the influence of molecular weight and concentration.