Space charge distribution in low-density polyethylene (LDPE)/pumice composite

Low-density Polyethylene (LDPE)/Pumice composites with different pumice weight percentage (1 wt%, 2 wt% and 5 wt%) were prepared by melt blending process in torque rheometer. Space charge distribution in composites and pure LDPE were investigated with pulsed electro-acoustic method (PEA). The results indicate that most of the space charge in pure LDPE under high electrical field was homo-polarity space charge which was gathered near both sides of the two electrodes. Oppositely, the space charge distribution in LDPE/pumice composite makes large differences. There was a great amount of hetero-polarity space charges appeared near cathode in LDPE/pumice composites, and the quantity of hetero-polarity space charge increased along with the increasing of pumice content. A great amount of positive charge was injected in LDPE/Pumice composite with pumice 5 wt% near the anode side, and these positive charges moved toward to the cathode of the sample when the electrical field strength increased to 30kV/mm and 50KV/mm. As the circuit was shorted, the decay of space charge vs. time is measured for all the samples. It shows that the space charge in pure LDPE and LDPE/Pumice composite with pumice 1 wt% decayed rapidly, nevertheless the space charge in LDPE/Pumice composite with pumice 2 wt% and 5 wt% decayed more slowly. There was quiet a few of space charges in pumice 5 wt% composite after short-circuited over 60 min.