Thermal degradation of polystyrene, poly(1,4-butadiene) and copolymers of styrene and 1,4-butadiene irradiated under air or argon with 60Co-γ-rays

Co-60-gamma-irradiated samples of polystyrene (PSt), poly(1,4-butadiene), (PBD), and two poly(styrene-co-butadiene)s containing 25 and 75% ED were subjected to thermogravimetric analysis (TGA), in the presence and absence of O-2. In the case of PSt the irradiation caused a significant shift in T-onset the onset temperature for mass loss, to higher temperatures, whereas in the cases of the ED-containing polymers irradiation caused a decrease in T-onset (oxic irradiation) or had little or no effect on T-onset (anoxic irradiation). The amount of non-volatile residue formed in the cases of ED-containing polymers was augmented by gamma-irradiation. The improved thermal stability of PSt is attributed to radiation-generated unsaturations acting as depolymerization retardants and/or agents in thermal crosslinking. Radiation-induced crosslinks do not affect the thermal behavior of PSt. In the cases of ED-containing polymers the thermal behavior is predominated by reactions of the carbon-carbon double bonds (crosslinking and cyclization). Radiation-induced chemical alterations, therefore, play a minor role during the thermal decomposition. (C) 1999 Elsevier Science Ltd. All rights reserved.