Synergistic Enhancement of Mechanical and DC Electrical Properties of mPE/IPC HVDC Cable Materials via Dual-Phase Grafting Modification

To address the limitation of traditional elastomer blending methods that often reduce the dielectric strength in toughening polypropylene (PP) cable insulation materials, this study proposes a separately grafted and blended method by grafting maleic anhydride (MAH) onto impact polypropylene compound (IPC) and metallocene polyethylene (mPE). Unlike conventional elastomer-modified systems or single-phase MAH grafting approaches reported previously, the independent grafting of MAH onto each phase significantly enhances the non-bonding energy and interfacial interaction, promoting deep interpenetration of molecular chains. This effectively addresses the problem of poor mechanical properties in the blend system while maintaining low hardness and storage modulus. Simultaneously, MAH optimizes the two-phase distribution and introduces uniformly dense deep traps that act as charge capture sites. The isothermal surface potential decay (ISPD) and simulation results indicate that grafting MAH introduces deeper trap energy levels into the material. The mPE-M/IPC-M exhibits superior DC electrical performance compared, achieving a synergistic improvement in the mechanical and DC electrical properties of IPC. This study breaks through the bottleneck of mutual constraint between mechanical and electrical properties in traditional blending modification, providing important theoretical and technical support for the development of recyclable insulation materials for HVDC cables.