THEORY FOR THE PLASTIC-DEFORMATION OF GLASSY-POLYMERS

We present a theory to account for how a stress field can induce plast ic flow in glassy polymers. We consider a molecular model in which cha ins are constituted from isotropic oriented elementary links embedded in a deforming continuum. The shear-stress field causes a redistributi on of such links governed by a balance equation in orientation space. After detail calculations of the number of oriented units in certain d irections, the net jump rate of the molecular links is given by an exp onential form, according to the transition state theories of Adam and Gibbs [6]. These considerations are compared with the study of Boyce e t al. [5] that included the effects of deformation rate, pressure and strain softening. The calculation of the plastic properties for polyme thyl methacrylate and polycarbonate for various types of deformation h as been made, and the corresponding results fitted the experimental da ta reasonably well.