Effect of liquid absorption on the treeing resistance of polyethylene

Many investigations have been made of treeing phenomenon in polyethylene and cross-linked polyethylene. Usually, cross-linked polyethylene (CPE) chemically cross-linked with di-α-cumylperoxide (DCP) has a higher resistance to treeing than ordinary polyethylene (PE) when they are tested with the needle-electrode test method. However, it was found that, when CPE is dried, it has the same low resistance to treeing as PE. From this, it was inferred that undried CPE owes its higher resistance to treeing to the presence of acetophenone, a decomposition product of DCP, which, we suggest, exists in tiny voids at the needle tip and suppress discharges in such voids.