Thermal degradation of polystyrene, poly(1,4-butadiene) and copolymers of styrene and 1,4-butadiene irradiated under air or argon with Co-60-gamma-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 sub jected 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-ons et 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 irra diation). The amount of non-volatile residue formed in the cases of ED-cont aining polymers was augmented by gamma-irradiation. The improved thermal st ability of PSt is attributed to radiation-generated unsaturations acting as depolymerization retardants and/or agents in thermal crosslinking. Radiati on-induced crosslinks do not affect the thermal behavior of PSt. In the cas es of ED-containing polymers the thermal behavior is predominated by reacti ons of the carbon-carbon double bonds (crosslinking and cyclization). Radia tion-induced chemical alterations, therefore, play a minor role during the thermal decomposition. (C) 1999 Elsevier Science Ltd. All rights reserved.