Formation of expanded percolation network via interfacial modification in BN/epoxy composites

Polymer composites incorporating high thermal conductivity fillers are widely used as thermal interface materials, yet their heat dissipation capability is still limited by interfacial thermal resistance. In this work, boron nitride was surface-modified with 3-aminopropyltriethoxysilane (APS) and incorporated into an epoxy matrix. Thermal conductivity measurements revealed that APS modification nearly doubled the composite thermal conductivity at higher filler loadings, attributed to the enhanced interfacial thermal conductance achieved through APS grafting. More importantly, further analysis showed that interfacial modification improves the overall thermal conductivity primarily by thermally connecting adjacent fillers through thin layers of polymer, strengthening the contribution of the expanded percolation network. Collectively, these findings verify APS grafting as an efficient interfacial engineering strategy and provide mechanistic insight into the design of high-performance polymer composites for advanced electronic thermal management.