High-pressure DSC study of thermal transitions of a poly(ethylene terephthalate) carbon dioxide system

The thermal transitions of a poly(ethylene terephthalate)/carbon dioxide (P ET/CO2) system were investigated by using a differential scanning calorimet er accessorized with a high-pressure DSC cell. It was found that the glass transition temperature of PET decreases with an increase in the CO2 pressur e due to the plasticization effect,, which is quite noticeable even at rath er low CO2 pressures. The sorbed CO2 enhances the mobility of the chain seg ments and depresses the crystallization temperature of the PET. The CO2-ind uced crystallization of PET at high pressure is attributed mainly to the pl asticization effect, which causes a lower T-g than room temperature for PET , and hence crystallization of PET can occur at room temperature. The sorbe d CO2 was also found to be able to induce the crystallization of PET at tem peratures lower than the glass transition temperature of PET. The results o f high-pressure DSC were supported by measurements of wide-angle X-ray diff raction (WAXD). (C) 1999 Elsevier Science Ltd. All rights reserved.