Effect of nano-filler grain size on space charge behavior in LDPE /MgO nanocomposite

The dielectric properties of nanocomposite can be affected by the concentration, surface modification and grain size of the nano-filler. This paper presents the pulsed electro-acoustic (PEA) measurement results of space charge distribution in pure low-density polyethylene (LDPE) and LDPE/MgO nanocomposite with different nano-filler size. The results show that a large amount of heterocharge accumulates near both electrodes in pure LDPE. After nano-MgO is adopted, the amount of heterocharge apparently decreases, and homocharge is observed and increases when the grain size of nano-MgO increases. Besides, under the suitable concentration of 1wt%, smaller MgO of 30 to 100nm has a greater effect on suppressing the space charge accumulation than that of 500nm. This is probably because nano-MgO filled in LDPE can reduce the potential barrier of interfaces between nanocomposite and electrodes effectively. Furthermore, the potential barrier decreases with the increasing of nano-MgO size.