| Abstract: | Polycarbonate is known to crystallize thermally, but only slowly and to a limited (25%) extent. The melting points reported exhibit a wide variation. We have found that the melting temperature of polycarbonate may be drastically increased by employing a sequence of vapor-induced crystallization and annealing treatments. The crystals formed by the treatment with organic vapor act as a nucleation or precursor state for further crystallization into larger, more perfect lamellae. An initial peak melting temperature of 195°C has been annealed up to 239°C, and then to 295°C by a double-heat treatment. This sample is 60% crystalline, based on heat-of-fusion calculations. An equilibrium melting point of 335°C has been obtained for PC from an extrapolation of reciprocal lamellar thickness. |
