The role of anelasticity in high stress mechanical response and physical properties of glassy polymers

Non-elastic deformation of amorphous polymers is studied from strain recovery tests. In particular, a strain recovery master curve is built. It allows one to estimate recovery times necessary to recover the whole non-elastic deformation. On such a curve, two non-elastic deformations, namely anelastic (nonlinear) and plastic deformations, are distinguished by their range of recovery times. The evolution of these two components is followed during a constant strain rate test. This clearly shows the importance of the anelastic deformation for the understanding of the nonlinear response of glassy polymers. Moreover, the structural modifications induced by non-elastic strain of glassy polymers were studied by mechanical spectroscopy, differential scanning calorimetry and density measurements. These modifications appear to result from the anelastic part of the strain. Lastly, a consistent description of the mechanical response of amorphous solid polymers, and subsequent recovery processes, is proposed. The polymers tested were poly(methyl methacrylate), atactic polystyrene, and polycarbonate.