Changes in charge trapping/detrapping in polymeric materials and its relation with aging

In the present paper, characteristics of charge trapping and detrapping in low density polyethylene under dc electric field have been investigated using the pulsed electroacoustic technique. Both normal and gamma-irradiated LDPE samples have been investigated to assess the effect of chemical changes on charge trapping/detrapping dynamics. A simple trapping and detrapping model based on two different trapping levels has been applied to experimental data. It has been found that there are increases in both trap concentration and trap depth, especially deep trap concentration after gamma irradiation, indicating that physical and chemical changes brought by irradiation have caused some changes in trapping characteristics of LDPE. The present findings suggest that the model could be used to describe any physical and chemical changes occurred in a material and number of traps and trap density especially for the concentration of deep traps could be used as ageing markers.