Space Charge Dynamics in LDPE Films Subjected to Dc Step Voltage under High Pressure

This paper describes an experimental study of space charge dynamics in low-density polyethylene subjected to dc step voltage under high pressure. A film with or without a small amount of additive was set in a pressure-chamber in a measurement system based on pulsed electro-acoustic method. Temporal changes in the space charge distribution in the film with semi-conduction anode and evaporated Al-cathode were observed under 0.1MPa and 1.5MPa. Positive charges penetrated from the anode into the bulk of the film in most cases. In the case of the film without any additives, carrier transport in the film was activated by the high pressure. However, the velocity of the carrier transport in the high pressure was lower than that in the atmospheric pressure when a small amount of stearic acid was added into the film as an ion component. These results indicated that the mechanism of the carrier transport in the additive-free film was different from that in the compounded film.