The application of heating rate to studies of polysiloxanes with cyanoethyl substituents and silazane polymers

Thermal behaviour of polysiloxanes containing cyanoethyl side groups was studied by differential scanning calorimetry (DSC). Samples were quenched to −165 °C and then reheated at different heating rates. The glass transition, an exothermal crystalline formation (cold crystallization) and endothermal melting of crystalline formations were detected. A broad cold crystallization peak and a melting peak were observed at a heating rate of 20 K/min. However, the samples gave a sharp cold crystallization peak and three endothermal peaks using a heating rate of 5 K/min. The DSC traces obtained were thus sensitive to heating rates. Thermal degradation of silazane polymers was studied by a thermogravimetric method. Three stages of degradation occur in the course of thermal decomposition. It was shown that the yields of pyrolytic product increased with the heating rate decreasing.