Space charge suppression effect of nano-size fillers added to polymeric materials

Abstract

Space charge suppression mechanism in nano-composite polymer material is studied using experimental results and numerical simulation. Recently, many kinds of nano-composite polymeric materials have been reported to have improved their characteristics under high electric field. For example, LDPE/MgO nano-composite, which is made up of low density polyethylene (LDPE) and nano size filler of magnesium oxide (MgO), exhibits high volume resistivity and high dielectric strength under dc electric field. Authors have investigated the space charge behaviour in LDPE/MgO nano-composite under high electric field using pulsed electro-acoustic (PEA) method. It has been found that, compared to LDPE, the space charge formation is also suppressed in the nano-composite material. As a reason for the suppression, we have suggested that the induced dipole polarization around MgO filler formed by dc stress application might play a role of carrier trap sites. From the numerical calculation, distortion of electric potential around MgO is seen to be much larger than that around naturally included dipole. It means that the MgO acts as a deep trap site as different from some defect or ions included in LDPE. Using the numerical calculation based on such electric potential distortion, we have tried to simulate the space charge distribution in LDPE/MgO under high dc electric field. The simulation results are in good agreement with the experimental results. © 2009 IOP Publishing Ltd.