Research on the performance enhancement effect of plasma-modified octavinyl- sesquioxane on polypropylene insulation materials for power cables

Polypropylene (PP), as a green and environmentally friendly material, is a potential material for power cable insulation. To improve the dielectric properties of PP cable insulation, octavinyl- sesquisiloxane (OV-POSS) was modified with the silane coupling agent KH550 and dielectric barrier discharge plasma treatment. PP nanocomposites containing elastomer-hydrogenated styrene–butadiene block copolymers (SEBS) were prepared by a melt blending method to investigate the effect of plasma-modified OV-POSS on the physicochemical and dielectric properties of the materials. The results show that the addition of OV-POSS nanoparticles, particularly after plasma treatment, significantly enhances the melting point and crystallinity of the composites. At room temperature, the DC breakdown strength of PP/30% SEBS/POSS nanocomposites with 1% mass fraction of plasma-modified OV-POSS reached 330.77 kV mm⁻¹, representing a 19.2% improvement over PP/30% SEBS. The DC conductivity was reduced by 7.3 times, 3.5 times and 3.14 times at electric field strengths of 10 kV mm⁻¹, 20 kV mm⁻¹ and30 kV mm⁻¹. The average charge density growth rate reduced from 28% to 12.3% compared with PP/30% SEBS. Plasma treatment of OV-POSS at an optimal power of 94 W further improved the DC breakdown strength to 297.31 kV mm⁻¹, a 3.6% increase over the untreated sample, while reducing the DC conductivity at 10 kV mm⁻¹, 20 kV mm⁻¹ and 30 kV mm⁻¹ by 1.85, 1.71 and 1.4 times, respectively. The plasma-modified OV-POSS effectively inhibits the accumulation of space charge, with the average charge density growth rate being reduced from 25.3% to 5.7%. These findings provide a robust foundation for the development of advanced PP power cable insulation materials with enhanced dielectric properties.