A comparative study of the effects of UV- and gamma-radiation on copolymers of acrylonitrile/butadiene

The radiolysis of nitrile rubbers with different acrylonitrile/butadiene co mposition and the homopolymers, poly(butadiene) (PBD) and poly(acrylonitril e) (PAN) has been investigated and compared with the photolysis of the same polymers. A significantly different mechanism of degradation was found for the two types of radiation. The results obtained by ESR, FTIR and measurem ents of soluble fractions of irradiated samples, indicated that the acrylon itrile units of the nitrile rubbers are more sensitive units to gamma-radia tion, with the effects of irradiation increasing with the acrylonitrile con tent. The reactions observed were consumption of double bonds, crosslinking , and cyclization with the formation of conjugated double bonds. No chain-s cission reactions were detected. In contrast to gamma-irradiation, the effe cts of photolysis were centred at the butadiene units, and increases in the acrylonitrile content resulted in a proportional decrease in the sensitivi ty of the copolymers. Crosslinking and chain scission were identified as th e main effects of photolysis of NBR rubbers. (C) 1999 Society of Chemical I ndustry.