Photooxidation of fire retarded polypropylene

The influence of an aromatic fire retardant (decabromodiphenylether) on the photooxidation of polypropylene is reported. Samples of fire retarded polypropylene were exposed to artificial accelerated weathering. The IR analysis of the irradiated samples shows that the photooxidation mechanism of polypropylene is not modified by the fire retardant, but that the rate of the oxidation is dramatically enhanced. The global effect of the fire retardant on the photooxidation appears to be the combination of two antagonistic effects: an inner filter effect resulting from the strong UV absorption of the fire retardant: and an induction of the oxidation by radical species formed by photolysis of the bromo compound. The photochemical behaviour of stabilised fire retarded polypropylene is also reported. A poor stability is observed in the case of samples stabilised by a redox antioxidant (HAS). A modification of the stabiliser can be observed throughout the irradiation. The inefficiency of the stabiliser in retarding the oxidation of the fire retarded polypropylene can be tentatively attributed to a deactivation of the stabiliser by hydrobromic acid generated by the photolysis of the bromo compound. (C) 1999 Elsevier Science Ltd. All rights reserved.