Metal–Ceramic AlSiC Hybrid Fillers for Polypropylene Composites: Thermal–Electrical Transport Decoupling for Thermal Interface Applications

Hybrid metal–ceramic fillers offer an effective strategy to overcome the intrinsic trade‐off between thermal conductivity and electrical insulation in polymer composites. Here, aluminum–silicon carbide (Al/SiC) hybrid particles were incorporated into a polypropylene (PP) matrix to achieve thermally conductive yet electrically insulating composites. The hybrid fillers were prepared by ball milling and melt compounded into PP at loadings up to 60 wt%. Thermal, electrical, mechanical, viscoelastic, and morphological properties were systematically characterized. Thermal conductivity increased monotonically with filler content, reaching a threefold enhancement ( k / k PP ≈3.04) at high loading, while electrical insulation was maintained up to 50 wt% without electrically percolated networks. Effective medium theory and percolation‐based modeling revealed a transition from isolated dispersion to thermally connected pathways dominated by phonon transport. Dynamic mechanical analysis showed a significant increase in storage modulus and a pronounced reduction in tan δ above 30 wt%, indicating suppressed viscous dissipation. This behavior is attributed to reduced interfacial damping enabled by the hybrid architecture, where aluminum particles act as localized mechanical and thermal bridges between adjacent SiC particles, enhancing stress transfer while limiting interfacial sliding and phonon scattering. These results demonstrate a viable interfacial engineering strategy for advanced thermal management applications.