STRAIN, BIREFRINGENCE, AND VOLUME RELAXATION AND RECOVERY IN POLYMER GLASSES

Stress and volume relaxation, creep, strain recovery and thermally activated strain recovery measurements have been made on bisphenol-A polycarbonate, a polyetherimide, and poly(2,6-dimethyl-1,4-phenylene oxide) as functions of thermal history, room temperature aging, strain, hold time and temperature. It was observed that as the temperature was increased, the amount of persistent strain not only increased, but also affected the stress relaxation behavior, and was observed to be partially recoverable at the test temperature. These data are interpreted in terms of a network model wherein it is proposed that the motion of defects between and past entanglements, their loss at chain ends, and the disentanglement of chain ends from other segments serve as the primary mechanisms of relaxation in the glassy state. © 1990.