Crystallization of bisphenol-A polycarbonate induced by organic salts; physical aspects. I. Crystallization rate,melting behavior,and morphology

The presence of organic acid salts in bisphenol-A polycarbonate (PC) completely modifies the crystallization mechanism, the melting behavior, and the morphology of the polymer. Organic salts are not ordinary nucleating agents for PC since they react with the polymer, producing metal phenoxide chain ends. On reaction, abundant instaneous nucleation is induced. The seeds are likely to be polymer crystalline fragments preexisting in the melt. The phenoxide chain ends significantly increase the growth rate of the crystalline phase. Melting points and enthalpies of fusion are unusually high, suggesting a high degree of crystalline perfection. Thick multilamellar crystals, which are likely to contain chains in extended configuration, are observed by electron microscopy. No trace of spherulitic morphology is found. The chemical instability of PC containing ionic chain ends is also shown to seriously affect the crystallization rate, the maximum degree of crystallinity, and the melting point.