Photooxidation of fire retarded polypropylene

The influence of an aromatic fire retardant (decabromodiphenylether) on the photooxidation of polypropylene is reported. Samples of fire retarded poly propylene were exposed to artificial accelerated weathering. The IR analysi s of the irradiated samples shows that the photooxidation mechanism of poly propylene is not modified by the fire retardant, but that the rate of the o xidation is dramatically enhanced. The global effect of the fire retardant on the photooxidation appears to be the combination of two antagonistic eff ects: an inner filter effect resulting from the strong UV absorption of the fire retardant: and an induction of the oxidation by radical species forme d by photolysis of the bromo compound. The photochemical behaviour of stabi lised fire retarded polypropylene is also reported. A poor stability is obs erved in the case of samples stabilised by a redox antioxidant (HAS). A mod ification of the stabiliser can be observed throughout the irradiation. The inefficiency of the stabiliser in retarding the oxidation of the fire reta rded polypropylene can be tentatively attributed to a deactivation of the s tabiliser by hydrobromic acid generated by the photolysis of the bromo comp ound. (C) 1999 Elsevier Science Ltd. All rights reserved.