The mechanism of degradation of polyethylene in a high electrical field

A chemical analysis of LDPE (low-density polyethylene) applied above and below the luminescence inception voltage was performed. The authors also examined the time dependence of the luminescence intensity and the spectrum of the luminescence, considering the mechanism of degradation of LDPE in a high electric field. The luminescence inception stress is about 60kV/mm if the stress mitigating effect due to the space charge is disregarded. It was lower by about 200kV/mm than the electrical tree inception stress. When voltage above the luminescence inception voltage was applied to LDPE, a free radical and an oxide were detected by ESR (electron spin resonance) and XPS (X-ray photoelectron spectroscopy), respectively. The time dependence of the luminescence intensity under constant AC voltage was examined. The luminescence intensity is shown to be stable in the initial stage. However, an intense light was observed after a certain period of voltage application.<>