Rigid Amorphous Phase and Low Temperature Melting Endotherm of Poly(ethylene terephthalate)Studied by Modulated Differential Scanning Calorimetry

摘要

The rigid amorphous phase, the low temperature melting endotherm, and their development with thermal treatment in poly(ethylene terephthalate) (PET) were investigated by means of modulated differential scanning calorimetry. The differential of the reversing heat capacity and nonreversing heat flow signals were used to analyze the behavior of the glass transition and the low temperature melting endotherm. With increasing annealing time, the increment of the heat capacity at the glass-transition temperature decreased and the increment of heat capacity at the annealing tempera-ture increased. It was suggested that the origin of the low temperature melting endotherm mainly resulted from the transition of the rigid amorphous fraction for the PET used. The glasslike transition of the rigid amorphous fraction occurred between the glass transition and melting.