Electrical properties of polypropylene/ethylene-propylene-diene monomer blend compatibilized with polypropylene-graft-maleic anhydride

Cross-linked polyethylene (XLPE) remains the de-facto insulation for high-voltage power cables, but its complex peroxide cross-linking presents sustainability challenges. Polypropylene (PP) blends have thus far been identified as a highly potential insulation alternative to XLPE. Nevertheless, inter-phase dielectric heterogeneity arising from different material phases in PP blends have impeded the practical use of PP blends in power cable insulation. As such, appropriate compatibilization of PP blends is crucial in obtaining desirable electrical properties. Herein, we report on the effects of polypropylene-graft-maleic anhydride (PP-g-MAH) compatibilization on a PP blended with ethylene-propylene-diene monomer (EPDM) through microstructural evolution and electrical properties quantifications. The results show that PP/EPDM compatibilized with 5 wt% PP-g-MAH yields a fine and uniform PP/EPDM morphology, with notably reduced space charge density and 18% enhanced breakdown performance over uncompatibilized PP/EPDM. Nevertheless, a higher PP-g-MAH content (9 wt%) re-introduces charge migration effects, elevating charge accumulation and lowering the breakdown strength. These results demonstrate that an appropriately tuned PP-g-MAH compatibilization simultaneously optimizes structural compatibility and charge trap mechanisms, thus enhancing the breakdown strength. These findings provide important insight into the compatibilization of thermoplastic PP/elastomer blends as future power cable insulation materials.