Effects of Crosslinking Agentsand Carbon Black Content on the Performance of Semi-Conductive Shielding Materials

To investigate the effects of the cross-linking agent and carbon black (CB) content on the characteristics of semi-conductive shielding materials for high-voltage cable, a blend was prepared by incorporating conductive CB as the filler, ethylene butyl acrylate copolymer as the matrix and 2,4-di-tert-butylcumyl peroxide (BIBP) as the cross-linking agent via melt blending and crosslinking. The influences of BIBP and CB content on the thermal elongation, volume resistivity, mechanical properties and rheological performance of the semi-conductive shielding materials were studied. With EBA at 70 phr and CB at 30 phr, as the BIBP content increases, the thermal elongation and permanent deformation rate of the semi-conductive shielding material decrease, while the volume resistivity increases and the tensile strength gradually improves. The elongation at break initially rises and then declines, and the melt flow index increases. When the BIBP addition amount is 1.0 phr, the overall performance is optimal. With EBA at 70 phr and BIBP at 1.0 phr, as the CB content increases, the volume resistivity of the semi-conductive shielding material gradually decreases. When the CB content increases to 25 phr, reaching its percolation threshold, the volume resistivity of the semi-conductive shielding material drops sharply. When the CB content is 35 phr, the volume resistivity of the semi-conductive shielding material is 4.3 Ω·cm and 16.2 Ω·cm at 25 ℃ and 90 ℃, respectively. Simultaneously, the positive temperature coefficient (PTC) is 0.82, indicating the best suppression effect on PTC. As the CB content increases, the tensile strength remains relatively stable, while the elongation at break gradually decreases. When the CB content is in the range of 20-35 phr, the mechanical properties meet the national standard requirements.