INFLUENCE OF AGING AND CRYSTALLINITY ON THE MOLECULAR MOTIONS IN BISPHENOL-A POLYCARBONATE

Thermally Stimulated Depolarization Current technique, Differential Sc anning Calorimetry, and Dynamic Mechanical Analysis have been applied to amorphous and semicrystalline bisphenol-A polycarbonate with crysta llinity degrees up to 21.8%, in a temperature interval covering the al pha and beta relaxations. The secondary beta transition is found to be the sum of three components whose variations in aged and annealed spe cimens have shown the cooperative character of the beta(1) and beta(2) modes, contrary to the localized nature of the beta(3) component. A T -g decrease was observed by both TSDC and DSC as a function of X(C) an d has been related to the possible confinement of the mobile amorphous phase in regions whose sizes are smaller than the correlation lengths of the cooperative movements that characterize the motions occurring at T-g. The at relaxation intensity variations with crystallinity show the existence of an abundant rigid amorphous phase in the semicrystal line material. The relaxation parameters deduced from the Direct Signa l Analysis of the or relaxation for the mobile amorphous phase do not show significant deviations from those found for the amorphous materia l. The existence of the rigid amorphous phase has been associated to t he ductile-to-brittle transition experienced by the material at low cr ystallinity levels. (C) 1996 John Wiley & Sons, Inc.