PHYSICAL AGING AND CREEP IN PVC

Tensile creep compliances have been determined for PVC over a wide range of times (t = 10(-8) to 10(6) s) at 23-degrees-C. Results were obtained on samples of different age characterized by the elapsed time t(e) between quenching from 85-degrees-C and the instant of load application, Various empirical functions were employed to model the data from both short-term (t less-than-or-equal-to 0.2t(e)) and long-term (t > 0.2t(e)) tests in terms of compliance contributions from secondary (beta) and glass-rubber (alpha) retardation regions. Results of these analyses suggest that physical ageing produces a decrease in strength of the beta-process, an increase in average retardation time for the alpha-process and negligible changes in the widths of the respective retardation time distributions. Comments are made on the structural significance of the results for the beta-process and on the validity of functions used to describe the creep curves.