Crystallization of polymers and the rigid amorphous fraction studied by the temperature-modulated techniques TMDSC and TMDMA

Quasi-isothermal temperature-modulated DSC and DMA measurements (TMDSC and TMDMA, respectively) were performed to determine heat capacity and shear modulus as a function. of time during crystallization. Non-reversible and reversible phenomena in the crystallization region of polymers can be observed. The combination of TMDSC and TMDMA yields new information about local processes at the surface of polymer crystals, like reversible melting. Until now we have found only one semicrystalline polymer showing no excess heat capacity during crystallization, namely Bisphenol-A Polycarbonate (PC). This allows study of vitrification and devitrification of the rigid amorphous fraction in PC. For other polymers the fraction of material involved in reversible melting, which is established during main crystallization, keeps constant during secondary crystallization. Simply speaking, polymer crystals are "living crystals."