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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 instantaneous 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.

The melting behavior of bisphenol-A polycarbonate samples plasticized by tritolyl phosphate (TTP), pentaerythritol tetranonanoate (PETN), and trimellitic acid-tridecyloctyl ester (TMDO) has been investigated and discussed on the basis of current theories. Using the Hoffman and Weeks approach modified for finite chain length the variation of the equilibrium melting temperature has been determined as a function of the plasticizer concentration. Extrapolation of these data yields an equilibrium melting temperature of 317 degrees C for the pure polycarbonate of infinite molecular weight. The cryoscopic effect observed is much more pronounced than anticipated on the basis of the Flory-Huggins theory.

The crystallization of bisphenol-A polycarbonate plasticized by trimellitic acid tridecyloctyl ester (Morflex 525) has been studied. A half-crystallization time of 100 min is observed at 170°C with 10% of plasticizer compared with a figure of 18,000 min for the unplasticized material. The kinetic study is limited to the primary crystallization process which can be described by an Avrami equation; however, the Avrami coefficients are much higher than usual. Studies on the effect of the preparation procedure of the samples and of premelting indicate that nucleation is at least partially heterogeneous.

For pt.II see ibid., vol.14, p.1367 (1976). Measurements of the spherulitic growth rates of bisphenol-/b A/ polycarbonate plasticized with pentaerythritol tetranonanoate (PETN), trimetallic acid tri(/b n/-octyl-/b n/-decyl)ester (TMDO), and tritolyl phosphate (TTP) are reported. The incorporation of a plasticizer enlarges the crystallization range, decreases the temperature of maximum growth rate and accelerates the kinetics to a considerable extent. The growth-rate parameters are calculated from a least-squares analysis of the experimental data according to the kinetic theory of Hoffman and Lauritzen (1973). From the growth-rate data given here and the overall crystallization kinetics reported previously, concentrations of seeds inducing the crystallization were determined.