Effects of Solvent-induced Crystallization on the Amorphous Phase of Polycarbonate of bisphenol A)

Abstract

By the combined use of DSC, WAXD and pycnometry techniques, it was demonstrated that the increase in free volume and reduction in Tg observed in semi-crystalline poly(carbonate of bisphenol A) (PC), whose crystallization was solvent-induced, are due to the creation of many microvoids, microcavities and crazes in the amorphous fraction of the polymer during the crystallization. Accordingly, the polymer chains and chain-segments present right at the polymer-air interfaces, forming the walls of these micro-cavities, are more mobile than the chains and segments in the bulk amorphous phase, resulting in a commensurate reduction in Tg . Upon annealing at elevated temperatures the microvoids, etc., heal, the polymer-air interfacial specific surface area decreases, and Tg increases toward the Tg of the bulk amorphous PC containing no microvoids, crazes and internal polymer-air interfaces.