A TEMPERATURE MODULATED DSC STUDY OF GLASS-TRANSITION IN POLY(ETHYLENE-TEREPHTHALATE)

A dynamic heat capacity of poly(ethylene terephthalate) in the tempera ture range of glass transition has been examined by a new technique of temperature modulated differential scanning calorimetry. The shift of glass transition temperature caused by the desorption of water could be monitored by the change in the dynamic heat capacity. Under quasi-i sothermal condition, the increase in the glass transition temperature causes the decrease in the magnitude of the dynamic heat capacity and a negative or positive change in the phase, depending on temperature.