Influence of AC ageing on space charge dynamics in LDPE

In the present work efforts have been made to investigate the influence of ac ageing on space charge dynamics in low-density polyethylene (LDPE). LDPE films with 200µm were aged at 50 kV/mm at 50 Hz for various times at ambient temperature. Space charge dynamics in the samples after ageing were monitored using the pulsed electroacoustic (PEA) technique. The results indicate that there is a significant amount of negative charge accumulation in the aged sample due to charge injection. These injected charges are captured by the deep traps originated from the interface between crystalline and amorphous regions in LDPE. The total amount of charge increases with the ageing time. Chemical analysis by infrared spectroscope (FTIR) and Raman microscope reveals little changes taken place in the bulk of the material after ac ageing. The consequence of the accumulation of space charge under ac conditions on the lifetime of the material has been discussed. 1