TEMPERATURE-GRADIENT DIFFERENTIAL THERMAL -ANALYSIS - A METHOD FOR INVESTIGATION OF MELTING AND CRYSTALLIZATION OF POLYMERS

A DTA instrument was designed, in which the variation of temperature i s achieved by moving a cell with a sample and a standard in a tube wit h a specified temperature gradient along its length. The instrument ma kes it possible to measure heat effects in the course of cooling down to -170 degrees C and to achieve fast cooling at a rate up to 200 K/s regardless of thermal history, whether it was heating, isothermal expo sure, or cooling. The instrument makes it possible to resolve the over lapping peaks of crystallization and melting in the systems of polycap roamide-epsilon-caprolactam and polyethylene-decalin. The peaks due to melting acid crystallization for a thermotropic mesomorphic polyester were found to vary depending on the thermal history of samples; for p oly(ethylene terephthalate), these peaks were controlled by preliminar y formation of crystallization nuclei.