Research on Semi-Conductive Shielding Materials for High-Voltage Cables Based on Compound Resins

Ethylene-vinyl acetate copolymer (EVA)-based semi-conductive shielding materials (SCSM) are widely utilized in low/medium-voltage cables. However, the limited thermal stability of EVA prevents their application in high-voltage cables. In this paper, LDPE is introduced to blend with EVA and carbon black (CB) was used as conductive filler to fabricate high thermal stable CB/EVA/LDPE composites for application as high-voltage SCSM. It is demonstrated that the incorporation of LDPE effectively enhances the thermal stability of the CB/EVA/LDPE composites. The first-stage thermal weight loss of the CB/EVA/LDPE composites is decreased to 10.4%, compared to that (14.7%) of the CB/EVA composites. The incorporation of LDPE also leads to the enhancement of the mechanical properties of the CB/EVA/LDPE composites, with a tensile strength of 17.9 MPa and an elongation at break of 285.9%. Moreover, the electrical properties of the CB/EVA/LDPE composites are well maintained, with a volume resistivity of 73.6 Ω·cm. These findings provide theoretical and experimental basis for the development of EVA-based semi-conductive shielding layer for high-voltage cables.