Annealing effect on semi-crystalline materials in creep behavior

Abstract

Three glass reinforced polymers of Nylon 66, PET and HT-Nylon with glass transitions of 58, 72, and 132°C are selected for checking the necessity of high temperature annealing and degree of its impact on creep strains. The improvement after annealing depends on the polymer type of whether it is fast or slow crystallizing at molding process and whether it has hydrogen bonded sheets. The physical property changes observed of these materials before and after annealing support the explanation of crystal reorganization through crystallization, free volume reduction through densification and crystal perfection through better chain packing. The prediction of long-term creep strains up to 10 years using time-temperature superposition technique has been the practice for last 13 years in our laboratory. The accuracy of the prediction are shown in confidence level of about 90%.