Annealing effects on the tree initiation voltage of polyethylene at high temperature

Annealing effects on the tree initiation voltage of high density polyethylene (HOPE) are studied. Three annealing methods with different cooling velocity were used in preparation of the samples. The samples cooled in high velocity were reheated and recooled. The crystallinity of these samples was measured. Recrystallization process was found. Put samples in oil with high temperature. For the samples cooled in low velocity and normal velocity, tree initiation voltage decreases with temperature increases. For samples cooled in high velocity, when the heating temperature is higher than 90 °C, tree initiation voltage increases abnormally and then decreases with heating duration in high temperature. In addition, tree initiation voltage of samples increase and then decrease with heating temperature increases. We presumed that the morphological microstructure and the recrystallization processes in samples are responsible for above phenomena.