Thermal Degradation of Silicone Sealant

Abstract

The kinetics of thermal degradation of a polyorganosiloxane sealant was studied by the thermogravimetric analysis (TGA) method at three constant heating rates (2, 5, and 20 deg/min). An investigation was also made of the change in shear strength of adhesive joints in the course of heat ageing at temperatures ranging from 250 to 340°C. The data obtained were processed by the non-linear regression method. The process of thermal degradation proceeds in two stages. The first stage has an activation energy of about 140 kJ/mol and is accompanied with increase in the strength of the adhesive layer. The second stage with a higher activation energy (roughly 230 kJ/mol) causes a sharp fall in strength of the adhesive layer. A possible mechanism of the thermal degradation process is discussed.