Effects of oxidation on electrical conduction and breakdown of LDPE films with different densities

The effects of oxidation on electrical conduction and breakdown strength were studied in two kinds of LDPE films with different densities. Oxidation enhanced more the conduction current in the LDPE film with density of 0.9172 g/cm³ (l-LDPE) than that with density of 0.9255 g/cm³ (h-LDPE). This result was attributed to the easier carrier transport in unoxidized region of l-LDPE. Both oxidized specimens had almost the same impulse breakdown strength (F_Bimp) except when the absorbance of C=O groups (A) is higher than 0.6. At 30°C, it was considered that the increase in the number of injected electrons which initiate avalanche decreased F_Bimp for A<0.1, but the carrier scattering due to C=O groups increased F_Bimp for A>0.1. However, thermal or electromechanical breakdown mechanism would take part in the breakdown process at higher temperature´s. The dc breakdown strength (F_Bdc ) decreased with oxidation and h-LDPE showed a higher one. These results suggested a contribution of thermal mechanism to the breakdown