Photodegradation of polyethylene: Effect of crosslinking on the oxygenated products and mechanical properties

The photodegradation of three types of polyethylene has been studied by electron spin resonance (ESR), ultraviolet absorption (UV), Fourier transform infrared absorption (FTIR), gel fraction and mechanical properties measurements.

Various types of oxygenated products were detected by FTIR spectrometry in photoirradiated polyethylene. The rate of formation of oxygenated products is greater in the case of photoirradiated crosslinked polyethylene. A detailed photodegradation mechanism for polyethylene is proposed on the basis of the experimental results.

Tensile tests on photoirradiated polyethylene were also carried out. It was found that crosslinking improved the photostability of polyethylene. The relationship between the amount of oxidation products produced and the decrease of mechanical strength gives a measure of the photostability of polyethylene. We have tried to correlate the carbonyl content with the mechanical properties to predict the photostability of the polymer.