DSC studies on the glass transition of poly (ethylene terephthalate) as a relaxation process
Polimery 1997, No 11-12, 674
Glass transition temperatures (Ts) of amorphous PET of various densities, determined by DSC at heating rates ranging from 1 to 20°C/min, showed the glass transition to be a relaxation process (Fig. 2), i.e., a temperature transition of kinetic type, rather than a second-order, transformation. The oscillation period of macromolecular chain segments, which is related to the density-controlled supra molecular structure of the polymer, was found to govern the kinetics of the glass transition process. A simple indicator qg(i) was suggested to describe the transition kinetics, easy to evaluate from appropriate DSC data.