Photodegradation of polyolefins

The photodegradation behavior of a propylene/ethylene copolymer has been investigated and compared to the degradation of a polypropylene homopolymer. The materials contained small amounts of thermal stabilizers, but no photo-stabilizers. The development of carbonyl and hydroxyl oxidation species was followed by infrared spectroscopy, but this was not a sensitive detection method in the early stages of degradation. Mechanical measurements indicated that the performance of the copolymer deteriorated after only brief exposures to ultraviolet irradiation in an accelerated weathering cabinet. In contrast, the homopolymer showed no signs of mechanical degradation during a short induction period, but then degraded very rapidly. The induction period corresponded to the disappearance of the thermal stabilizers. Outdoor weathering results confirmed the trends predicted by artificial weathering; however, the predicted service lifetimes were underestimated by about 50%