Effect of Secondary Crosslinking Time on the Interfacial Insulation Performance of Crosslinked Polyethylene/Semiconductive Shielding Layer

To investigate the influence of secondary crosslinking time on the interfacial insulation performance between crosslinked polyethylene (XLPE) and a semiconductive shielding layer, XLPE sheets and semiconductive EVA pellets were selected. XLPE/semiconductive shielding layer interfacial specimens with secondary crosslinking times of 10 min, 15 min, 30 min, 45 min and 60 min were prepared. Polarization and depolarization current (PDC) measurements, breakdown voltage tests, peel adhesion strength evaluation and scanning electron microscopy (SEM) observations were systematically performed. The interfacial polarization current, characteristic breakdown voltage and interfacial peel adhesion strength of the specimens were obtained and analyzed. The experimental results indicate that, with increasing secondary crosslinking time, the interfacial polarization current showed an initial decrease followed by an increase, and the characteristic breakdown voltage and the interfacial peel adhesion strength showed an initial increase followed by a decrease. Further analysis suggests that an excessively long secondary crosslinking time reduces the area of the interfacial interpenetration region between XLPE and the semiconductive shielding layer, which is the primary factor responsible for the deterioration of interfacial insulation performance. The results provide experimental evidence and theoretical support for optimizing flexible joint manufacturing processes and improving their operational reliability and service lifetime.