The use of a mathematical model to describe isothermal stress-strain curves in glassy thermoplastics

Abstract

A new model is proposed to describe the large recoverable extensions which can be observed with high polymers below their glass transition points. The model consists of a Hookean spring in series with an Eyring dashpot and rubber elasticity spring in parallel. Conventional stress-strain curves for cellulose nitrate and cellulose acetate sheet and PVC are compared with those predicted by the model. In this way many of the characteristic features of the stress-strain curves of plastics can be illustrated. Differences between the stress-strain curves of a number of polymers are discussed in terms of the model, and the tendency of a polymer to show necking is related to the ultimate network strain (limiting elongation) under the conditions of the test.