Effects of crystallinity and electron mean-free-path on dielectric strength of low density polyethylene

The mean free path of photoinjected hot electrons in LDPE was obtained experimentally, and based on this result the relation between crystallinity and dielectric strength is discussed. The change in X-ray diffraction spectra of 50-μm-thick hot-pressed LDPE films of annealed at various temperatures is shown. The crystallinity of the film is improved as the annealing temperature increases. The relation between the dielectric strength and the annealing temperature of the hot-pressed film is shown. The dielectric strength decreases as the annealing temperature increases, as shown in measurements at room temperature and -50°C. The heat treatment improves the crystallinity and makes the mean free path longer, resulting in a lower dielectric strength.