Non-isothermal melt crystallization of poly(tetramethylene succinate) under high pressure: Characterization and kinetics

The non-isothermal melt crystallization behavior (characterization and kinetics) of poly(tetramethylene succinate) (PTMS) under high pressure was investigated using high pressure differential thermal analysis (HP-DTA). Wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), polarized optical microscopy (POM), and density measurement were used to study the crystal structure, the melting temperature and the morphology of the samples crystallized under various pressures. No new crystal structure or formation of extended chain crystals were found in the pressure crystallized samples. Optical micrographs revealed nucleation density decreased and spherulite morphology changed (presence of banding pattern) above 300 MPa. DTA crystallization curves showed a single exothermic peak at all pressures which shifted to higher temperatures with increasing pressure and became broad above 300 MPa. The kinetics was studied using the Ozawa model. A change in the nucleation pattern was predicted from the Ozawa exponent, instantaneous at low pressures and sporadic above 300 MPa. From kinetic and morphological results it was found that a critical pressure region existed around 300 MPa.