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

Volume dilatometry was used to explore the origin of the beta transiti on (T(beta)) and its influence on physical ageing. The results show th at volume recovery does occur even at temperatures below T(beta), a ph enomenon indicating the existence of molecular rearrangements and coop erative motions below this point. Lowering the ageing temperatures thr ough T(beta) progressively retards short-term molecular rearrangements and cooperatives motions. Nonetheless, the T(beta) quench does not in cur any excess free-volume trapping, and its associated change in spec ific volume follows a linear relationship with respect to temperature. The existence of T(beta) is time-dependent, which leads to the conclu sion that the formation of T(beta) has a kinetic origin.