THE ORIGIN OF THE BETA-TRANSITION AND ITS INFLUENCE ON PHYSICAL AGING

Volume dilatometry was used to explore the origin of the beta transition (T(beta)) and its influence on physical ageing. The results show that volume recovery does occur even at temperatures below T(beta), a phenomenon indicating the existence of molecular rearrangements and cooperative motions below this point. Lowering the ageing temperatures through T(beta) progressively retards short-term molecular rearrangements and cooperatives motions. Nonetheless, the T(beta) quench does not incur any excess free-volume trapping, and its associated change in specific volume follows a linear relationship with respect to temperature. The existence of T(beta) is time-dependent, which leads to the conclusion that the formation of T(beta) has a kinetic origin.