The Effect of Absorbed Oxygen on Electrical Treeing in Polymers

This paper describes the effect on electrical treeing of oxygen absorbed in physical spaces such as microvoids or free volume in polyethylene. The ac tree initiation and growth were investigated at room temperature using untreated samples and also samples degassed by a vacuum pump. The tree starting voltage of the degassed samples is much higher than that of untreated samples. The experimental results show that this improvement can be attributed to the removal of oxygen from PE. We also observed in detail the processes of tree initiation and growth in the degassed samples. The observations, with other results, led us to conclude that the charge carriers injected from the point electrode play a dominant role in the tree initiation.