Electrical and mechanical properties of POP-toughening semi-conductive shielding layer for PP cables

Polypropylene (PP) receives significant interests because of environmental friendship and excellent insulation. The development of PP cables depends heavily on the semi-conductive shielding layers that match the PP insulation layers. In this paper, propylene–ethylene copolymer (POP) is used to toughen the PP-based shielding layer. The effects of POP content (40 parts, 50 parts and 60 parts) on the electrical and mechanical characteristics are investigated. Further, the interface matching characteristics and toughening mechanism of the shielding layer are explored. According to the experimental findings, owing to the growth in POP content, the distribution of carbon black (CB) particles becomes more uniform, and the surface roughness decreases from 52.7 nm to 14.7 nm. When the POP content is 60 parts, the charge injected into the insulation layer is the least, which is 0.643 × 10⁻⁷ C, and the maximum electric field distortion decreases to 11.4 kV/mm. All three POP content shielding layers maintain a low resistivity at high temperatures (110 ℃, 80 Ω·cm). Besides, as the POP content increases, the toughness of PP-based shielding layer is improved and the elongation at break of POP-60 semi-conductive shielding layer reaches 420%. This research paves a new way for the development of semi-conductive shielding layer of PP cables.