Oxidative crosslinking of polyethylene by ultraviolet light

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Abstract
The mechanism of weathering damage in polyethylene films was studied by measurement of molecular weight (by intrinsic viscosity), content of xylene‐insoluble fraction (gel), and carbonyl group concentration (by infrared analysis) in exposed samples. Results obtained indicate that both chain scission β and crosslinking α occur simultaneously. The effect of thickness and crystallinity of the polyethylene films suggest that the ratio β/α may be dependent upon the oxygen concentration at the site of reaction and, therefore, the rate of penetration of oxygen through the film, at constant intensity of absorbed light. The chain scission reaction appears to be favored in highly crystalline regions.