Thermally stimulated discharge in filled LDPE films

To understand how the chemical structure of fillers affects space charge formation and storage in filled polymeric insulation, the authors have investigated the carrier traps in LDPE (low-density polyethylene) films filled with different types of zeolites by the measurement of thermally stimulated current. The characteristics of trapped carriers are examined, and the relaxation time and activation energy are calculated by computer simulation based on a single relaxation time model. Other thermal analysis methods are also employed to elucidate molecular relaxation behavior. It is shown the charges injected from electrodes will accumulate in the boundaries of crystalline and amorphous region in unfilled LDPE film. Impurity-vacancy dipoles are formed in the LDPE filled with zeolites. Those dipoles act as shallow traps for carriers and prevent the accumulation of space charge in the LDPE. The dielectric property of filled LDPE is strongly dependent on the structure of fillers