Pressure‐Induced Flow Fabrication of Anisotropic Thermally Conductive and Insulating CF @ SiC / HDPE Composites

Mesophase pitch‐based carbon fibers (MPCFs) are promising thermally conductive fillers but suffer from high electrical conductivity and significant interfacial thermal resistance. We propose a dual strategy combining interfacial covalent bonding with pressure‐induced flow (PIF) orientation to overcome these limitations. A core‐satellite hybrid filler (CF@SiC) was synthesized by covalently grafting SiC onto oxidized MPCFs using a silane molecular bridge, aiming to enhance interfacial phonon transport while insulating the conductive core. Processed into HDPE composites via PIF, the hybrids exhibited high alignment, yielding significant thermal anisotropy. At a 30 wt% loading, the composite achieved a high in‐plane thermal conductivity of 6.83 W·m −1 K −1 . Crucially, the composite maintained an outstanding volume resistivity of 1.81 × 10 15 Ω, outperforming the percolated control composite by five orders of magnitude. This work effectively resolves the conductor‐insulator paradox, offering a versatile strategy for developing directionally thermally conductive yet electrically insulating polymer composites.