Electrical Breakdown of Ethylene Copolymers

co was found that the electric strength FB of ethylene co-polymers containing optimum content of halogen compouns copigher than that of LDPE over a wide temperature range from -196 to 90°C, and that their conduction current was suppressed at the higher fields. It is thought that the introductioned comonomers with halogen groups into polyethylene suppresses the electron acceleration due to an increase of the scattering of conduction electrons, leading to an increase of FB which is determined by the electron avalanche breakdown. However, the reason for a fall of FB with halogen content at high content level is not yet clear. A tentative explanation is presented: Existence of high halogen content in the amorphous part of the ethylene chain gives rise to some kind of defects which arise, for example, from locally brittle structures or stereo hindrance due to strong dipole-dipole interaction, leading to a decrease of FB.