Abstract
The treeing resistance of low density polyethylene is drastically improved in oxygen free condition such as in vacuum or at 77 K.
In oxygen free condition, the deteriorated region is formed in high field region before tree initiation. The chemical analysis of the deteriorated region by FT-IR and Raman spectroscopy showed that it has excess carbonyl groups (C=O) and double bonds (C=C) than normal polyethylene, and that the amorphous part increases in it.
In the deteriorated region, a number of voids and cracks were observed by scanning electron microscope (SEM). Their size is less than 0.5μm diameter. The observation by transmission electron microscope (TEM) revealed that the lamella of polyethylene tends to disappear in the deteriorated region. These results suggest that chains of polyethylene are scissored in the deteriorated region during high electric field application.
