Interface-driven structural engineering of polypropylene carbonate-modified MgO composites for enhanced thermal conductivity

As electric vehicle (EV) batteries evolve toward higher energy densities, the demand for advanced thermal interface materials (TIMs) with high thermal conductivity (TC), superior mechanical strength, and anti-hydration properties becomes critical. TIMs must effectively dissipate heat while maintaining structural integrity under harsh thermal and humid conditions to ensure long-term reliability. In this study, we developed a high-performance epoxy composite incorporating thermally and chemically engineered magnesium oxide (MgO) fillers. The MgO was modified via thermal treatment and polypropylene carbonate (PPC) surface functionalization, forming a 365 nm hydrophobic coating layer while increasing the average grain size from 0.9 μm to 22 μm. This novel approach significantly mitigated Mg(OH)₂ formation after 120 h in deionized water at 50 °C.Furthermore, the interface engineering between PPC-modified MgO and epoxy enhanced phonon transport while reducing interfacial resistance, leading to a 65 % increase in tensile stress and a TC enhancement from 1.192 W/mK to 2.036 W/mK. By optimizing the high-density packaging (HDP) process, we achieved an unprecedented TC of 9.22 W/mK at a filler content of 75.1 vol%, surpassing conventional epoxy-based TIMs. This study demonstrates a synergistic strategy combining grain boundary engineering, interfacial optimization, and dense filler packing to develop next-generation TIMs.