REJUVENATION AND ANNEALING EFFECTS ON THE LOSS CURVE OF POLYCARBONATE .2. COOLING AND AGING DEPENDENCE

Loss curves at 1 Hz were measured for polycarbonate (PC) samples with various mechanical and thermal histories on heating from -50 to 140°C or on cycling within these limits. The α′ peak, on the left side of the α peak, was found to shift to higher temperatures with decreasing θ values of the samples and even to disappear from the heating loss curve as predicted by the model presented in the first part of this series of papers1. The left side of the α peak is correctly predicted in all cases, but an additional peak, called α″, which was not predicted, appeared to the right of the β peak for samples cooled from temperatures Ta ≧ Tg - 65 K or for quenched samples. The α″ peak was found to vanish on ageing the samples at room temperature and to be erased by plastic deformation. A new definition of ageing and annealing phenomena is advanced using the concept of structural temperature. The α″ and α′ peaks seem to be linked to ageing and annealing, respectively. © 1990.