Effect of nanosilica grain size on the trap density distribution in LDPE/silica nanocomposite

In this paper, the effect of nano-additive grain size on trap density distribution in low-density polyethylene (LDPE) and LDPE/silica nanocomposites was investigated with depolarization current. The concentration of hydrophobic nanosilica was from 1.0 to 5.0 wt% and the average particle size was 7 nm and 16 nm, respectively. The depolarization current of pure LDPE acquired from 0.1 to 3600 s is associated with deep trap depth from 0.71 to 0.98 eV. Three trap peaks are obviously observed in trap distribution evaluated from isothermal relaxation current theory (IRC). It indicates that depolarization relaxation current measured is originated from detrapping of charge in these three types of deep traps. The density of deep trap significantly reduces after introduction of nanofiller, evaluated by the IRC theory and the ε" proportional to trap density. It means that the introduction of nanofiller could suppress the formulation of deep trap. Moreover, the density of deep trap is smaller in nanocomposite filled with 7 nm nanofiller, compared with that filled with 16 nm nanofiller. It indicates that the suppression of deep trap is more effective for nanofiller at smaller particle size.