PHOTOREACTIONS OF RADICALS DURING POLYOLEFIN PHOTO-OXIDATION

Data are presented which show that polypropylene (PP) and polyethylene (PE) peroxy radicals undergo photoreactions, but under commonly encountered photodegradation conditions these reaction rates are much lower than those of conventional radical reactions. At lower temperatures ( less than minus 10 degree C) or when more intense radiation is used, however, peroxy radical photolysis becomes a proportionately more important source of alkyl radicals. In addition, occurrence of photoinduced radical combination is confirmed but is shown to be important only when photolysis generates an alkyl radical sufficiently close to a peroxy radical that termination can occur before oxygen reconverts the alkyl radical to a peroxy radical. This termination mechanism therefore becomes more important for radicals generated at lower temperatures when the average separation of a radical pair is lower.