INHIBITION OF THE SPACE CHARGE OF LLDPE BY CROSSLINKING EFFECT

In this paper, the space charge behaviour of linear low density polyethylene (LLDPE) crosslinked polyethylene (XLPE) materials with different crosslinking degree is investigated by pulsed electro-acoustic (PEA) method. It is found that the distortion of the field strength is mitigated with the increase of the crosslinking degree. But the improvement of distortion is less obvious with the increase of the crosslinking degree when the crosslinking degree reaches 77% (1.4wt.% dicumyl peroxide (DCP)). The conductivity measurement is in accordance with this phenomenon by showing a decreasing trend in the conductivity of samples with the increase of DCP content in the range of 0wt.% to 2wt.% DCP content. Moreover, the crosslinking degree illustrates the mechanism of this phenomenon, for the rate of the increase of crosslinking degree decreases with the addition of DCP, and SEM observation implies an increase of the non-uniformity spherulites and amorphous region due to the crosslinking process. This study may help to understand more of the function of crosslinking and make better choice of the crosslinking degree of HVDC extruded cable insulation materials.