Structural aspects of physical aging of polymer glasses

Published data concerning the problem of the physical aging of glassy polymers are surveyed. Basic attention is given to an analysis of structural rearrangements that accompany the physical aging of glassy polymers. The processes of aging (spontaneous change in the properties of polymer glasses during the storage at a temperature below the glass transition temperature) can be classified into the two following categories: first, the aging of undeformed polymer glasses and, second, the mechanical stress-induced aging of a polymer. It is shown that in the former case, the processes occur throughout the entire body of the polymer and, in the latter case, the aging processes is concentrated in microscopic zones (shear bands) that emerge during polymer deformation. The current concepts of the aging of polymer glasses are discussed.