Influence of PP‐g‐MAH and POE‐g‐MAH on the High‐Temperature Dielectric Properties of PP/POE Composites for HVDC Cable Insulation

Polypropylene (PP) is recyclable and offers excellent insulation, but it requires elastomer blending for cable applications due to its brittleness. Although polyolefin elastomer (POE) enhances mechanical properties, it degrades dielectric performance, particularly at high temperatures. This study systematically investigates how the type and concentration of maleic anhydride‐grafted compatibilisers (PP‐g‐MAH and POE‐g‐MAH) affect the microstructure and dielectric properties of PP/POE composites for developing eco‐friendly HVDC cable insulation. The grafted material was evaluated for its phase morphology, crystallisation behaviour and dielectric properties within the temperature range of 20°C–60°C. Results show that PP‐g‐MAH improves the dispersion homogeneity of POE and increases the composite crystallinity. The 15 wt% PP‐g‐MAH composite exhibits enhanced deep trap density, suppressing space charge accumulation and attenuating the DC breakdown strength reduction at elevated temperatures. This work provides an effective interface engineering strategy for optimising high‐temperature dielectric performance in thermoplastic PP/elastomer insulation systems.