Direct observation of space charge distribution in polyethylene

Abstract

The space charge behavior in PE (polyethylene) was investigated using the laser-induced pressure pulse (LIPP) technique and the piezoelectrically induced pressure step (PIPS) wave technique. Specimens used were 25- mu m-thick films and 0.6- and 1-mm-thick plates of low-density PE nominally free from additives. The LIPP measurement was carried out on a spectrum which was polarized at 333 K for 15 min and subsequently short-circuited at room temperature. The PIPS measurement was carried out on a 25- mu m-thick specimen under an applied field. Positive space charge was found to exist in the PE bulk, and negative space charge due to electron injection was dominant at high fields. Oxidation of PE was found to enhance electron and hole injection.<>