Continuously thermal conductive pathway of bidisperse boron nitride fillers in epoxy composite for highly efficient heat dissipation

Abstract This study presents a combined strategy of bidisperse boron nitride (BN) and surface modification to improve the thermal conductivity (κ) of the BN-epoxy composite. Surface modification of hexagonal BN was carried out with benzoic acid (BA). The optimal weight ratio of large and small BN (BNl and BNs) was 8:2 for their connectivity in the epoxy matrix. For 50 wt% filler content, the BNl8s2-BA composite has a much higher κ of 2.71 W/m·K (out-plane direction), which is 12.3, 1.32, and 1.50 times higher than that of the pure epoxy, and its composite with BNl10s0-BA and BNl8s2, respectively. The chemical-sensitive analyses indicate that carboxyl-carboxylate interaction occurred in partially deprotonated benzoic acid on BN during the epoxy curing process, resulting in in-situ formation of a continuously thermal conductive pathway, which is responsible for the improved κ.