Thermal degradation of functionally terminated polybutadienes: Pyrolysis gas chromatography and thermogravimetric studies

Thermal degradation of functionally terminated liquid polybutadiene polymers, carboxy‐terminated polybutadiene (CTPB), hydroxy‐terminated polybutadiene (HTPB), and poly(butadieneacrylonitrile‐acrylic acid) terpolymer (PBAN) and their cured analogues were studied by pyrolysis gas chromatography in the temperature range 500–850°C. It was found that CTPB, HTPB, and PBAN could be distinguished from one another by the variation in the composition of their pyrolyzates. The differences in the product composition were rationalized by the relative importance of unzipping and hydrogen transfer reactions in the mechanisms of their degradation. The presence of the OH group was found to favor hydrogen transfer reactions whereas the COOH group has only marginal effect. The cyclization reactions were found to predominate in the thermal degradation of cured PBAN and the pyrolysis results were substantiated by thermogravimetric studies at several heating rates. The activation energy for the decomposition of cured PBAN was estimated to be 259 ± 16 kJ mol−1 by Ozawa's method.