Surface Potential Decay in Polyethylene

Abstract

Both thermally-stimulated and isothermal surface potential decay have been investigated in both high- and low-density polyethylene (HD-PE and LD-PE) charged by two different methods, i.e. corona- and DC potential-chargings. A clear cross-over phenomenon was observed for the V _s-T characteristics in HD-PE, but not for LD-PE. Similar decay characteristics were obtained for corona- and DC potential-charging. Estimation of the amount of space charge in the DC potential-charged polyethylene gave direct evidence for the charging-potential-dependent occupancies of deep surface states and shallow bulk ones. The ratio of surface charge to bulk space charge for HD-PE decreased rapidly with the charging potential, while most charges were still in the surface states for LD-PE charged at 2000 V. This is why a clear cross-over appears in HD-PE.