Molecular structure and electric breakdown of ethylene/silane copolymers

Crosslinking characteristics and electric breakdown ( F }B) of various kinds of ethylene/silane random copolymers were investigated. The crosslinking rate was found to increase with the reactivity of the silane species, whereas the F B did not significantly differ among the samples with different silane radicals. The F B was measured in a temperature range of 30-160°C using dc and impulse voltages. The results revealed that the dc F B was larger than the impulse one below the critical temperature T c for the crosslinked silane/ethylene copolymers with two different gel contents. The difference was interpreted in terms of space charge effect. T c moved to higher temperature with increasing the degree of crosslinking. X-ray induced TSC measurements allowed observation of new TSC peaks at high temperatures due to the crosslinking giving rise to carrier traps, consistent with the breakdown result.