Kinetics of volume recovery in amorphous polymers

Constitutive relations are derived for volume recovery in amorphous polymers, which is treated as diffusion of free volume elements (holes) to micro-voids. Due to the presence of a small parameter in governing equations, these relationships are simplified and reduced to nonlinear ordinary differential equations. Unlike conventional phenomenological models, our approach results in different relations for the evolution of free volume at heating and cooling of a specimen. To verify the model, we compare results of numerical simulation with observations. Fair agreement is demonstrated between experimental data and numerical predictions for polystyrene and poly(vinyl acetate).