Temperature dependent trap level characteristics of graphene/LDPE nanocomposites

The trap level characteristics are attracting much attentions in electrical and electronic engineering, which are closely associated with electrical properties of insulating materials. This paper try to modify the trap level characteristics of Low-density Polyethylene (LDPE), by incorporating graphene nanofillers into polymer with a filler content of 0.001, 0.003, 0.005, 0.007 and 0.01 wt%. The effects of filler content and ambient temperature on the trap level distributions are investigated, based on the isothermal surface potential decay (ISPD) method under 30, 50 and 70 °C. The experimental results show that the deep trap level and density increase with the filler content from 0 to 0.005 wt%, and then decrease with the further increase to 0.01 wt%. The increases of deep trap level and density affect the detrapping processes and suppress the electron injection into polymer bulks and cause a much slower downward trend in ISPD curves, especially at ambient temperature of 70 °C. Additionally, the apparent deep trap levels increase as temperature increases, since deeper and deeper traps are involved in the charge-release mechanism. It is concluded that the graphene nanofiller loading with a content of 0.005 wt% introduces large quantities of deep charge traps in the polymer-filler interfacial regions, which reduce the detrapping rate of charges and suppress the charge injection into polymer.