Analysis of surface trapping parameters of solid insulation dielectrics

In order to investigate the relationship between the surface trap and insulation performance of polymers. The theory of isothermal currents proposed by J.G. Simmson etc in 70 s last century was introduced in this paper and a set up of measurement device was designed to measure the trapping parameters of the surface layer of polymers. 3 kinds of polymer material films were used. The needle-plane corona discharge was employed to charge the samples. The upper side of each sample was subjected to a dc corona discharge in atmosphere, and the other side was grounded. The applied voltage was ± 4 kV and the charging time was set as 2 min. After charging, all needle electrodes were taken away, and the two sides of the sample were short-circuited for 1 minute to remove the free charges. Then the surface potential of samples was measured without contacting a surface potential meter (S2001A, Kawaguchi), and the surface trapping parameters could be calculated by the theory of isothermal currents. The electrons and holes traps shape of LDPE and PTFE was similar but not similar to PP. Results show that density of electrons and holes traps and energy distribution are related with the macromolecular chain structure, the different atom attached to the main chain affects the traps distribution heavily.