Polypropylene/Boron Nitride Insulating Composites With High Thermal Conductivity and Breakdown Strength

ABSTRACT Polypropylene (PP) based high‐voltage direct current (HVDC) cables face challenges due to their inherent poor heat dissipation, leading to heat accumulation during prolonged operation, which seriously compromises their operational stability and service life. In this study, boron nitride nanosheets (BNNSs) surface‐modified with maleic anhydride‐grafted polypropylene (PP‐g‐MAH) were melt‐blended with long‐chain branched copolymer polypropylene (cPP) to fabricate a high‐thermal‐conductivity PP insulating material. The PP‐g‐MAH acted as a compatibilizing interlayer between the BNNS fillers and the polymer matrix, improving filler dispersion and promoting phonon transfer, thereby enhancing the thermal conductivity of the composite. Meanwhile, the two‐dimensional sheet‐like structure of BNNSs effectively prolongs the formation path of electrical breakdown, leading to superior breakdown strength. At a BNNS loading of 30 wt%, the composite achieved a thermal conductivity of 1.5 W/m‧K and a breakdown strength of 409.02 kV/mm. Finite element simulation results demonstrated that using this composite as the insulation layer can significantly increase the ampacity of cables within their operational temperature range. This work provides valuable insight for the design of high‐thermal‐conductivity insulating materials.