Photo-oxidative Degradation of Mechanically Stressed Polyolefins

Abstract

The influence of mechanical tensile stress on the photodegradation of commercial drawn polyolefin tapes has been investigated. The degradation was monitored by the time-to-break in creep experiments. Surprisingly, photodegradation had little effect on creep rates of polyethylene and only a small effect on creep rates of polyethylene-propylene copolymer (<10% ethylene content). The stress was shown to accelerate photodegradation. The extent was proportional to the applied stress for polyethylene. With copolymer, the extent was negligible below about 50% of break stress, but important above 50 %. For example, with 90% of break stress applied, the time-to-break in the standard creep test was reduced by 30%. The presence of antioxidant in the copolymer was partially effective in preventing photodegradation, and the stress effect was reduced.