Crystallization of bisphenol‐A polycarbonate. II. Melting behavior and equilibrium melting temperature of the plasticized polymer

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°C for the pure polycarbonate of infinite molecular weight. This figure greacly exceeds the value so far reported in previous publications. It is also shown that the compatibility of the plasticizer affects the melting temperature just as it controls the glass transition. The cryoscopic effect observed, however, is much more pronounced than anticipated on the basis of the Flory–Huggins theory.