Polypropylene-based blend with enhanced breakdown strength under gamma-ray irradiation for cable insulation

This study focuses on the electrical properties and microstructure of polypropylene(PP)-based blends used for cable insulation in nuclear power plants(NPPs). The PP-based blend, comprising isotactic PP and propylene-based elastomer(PBE) at concentrations ranging from 0 to 50 wt%, underwent a melt blending process and subsequent cobalt-60 gamma-ray irradiation with doses ranging from 0 to 250 kGy. Electrical conductivity, trap distribution, and alternating(AC) breakdown strength were chosen to assess the insulation performance. These results indicate that the addition of PBE significantly improves the electrical properties of PP under irradiation. For PP, the electrical conductivity increased with irradiation, whereas the trap depth and breakdown strength decreased sharply. Conversely, for the blend, these changes initially exhibit opposite trends. When the irradiation was increased to 250 kGy, the AC breakdown strength of the blend improved by more than 21%compared to that of PP. The physical and chemical structures of the samples were investigated to explore the improvement mechanisms. The results offer insights into the design of new cable-insulation materials suitable for NPPs.