Highly thermally conductive flame retardant epoxy nanocomposites with multifunctional ionic liquid flame retardant-functionalized boron nitride nanosheets

The low heat dissipation efficiency and serious security issues related to polymer-based thermal management materials (TMMs) have seriously limited their practical applications. However, simultaneously improving their thermal conductivity (TC) and flame retardancy is still a challenge due to performance limitations and complicated processing. Here, non-covalent ionic liquid flame retardant-functionalized boron nitride nanosheets (ILFR-fBNNSs) were used as a multifunctional nano-additive for fabricating epoxy (EP)-based nanocomposites with both superior TC and flame retardancy. Owing to its structural uniqueness and multifunctionality, the ILFR-fBNNS triggers resin crosslinking at a given temperature, while conferring significant improvements in dispersion and interfacial adhesion, thereby forming a thermally conductive network with reduced interfacial phonon scattering and a high-efficiency nano-barrier network acting synergistically with ILFR-induced char residues during thermal degradation. Therefore, the ILFR-fBNNS not only functions as a curing agent for fabricating the nanocomposites, but also acts as a thermal conductor and flame retardant for the nanocomposites. The optimal comprehensive performances of EP/ILFR-fBNNS nanocomposite are achieved with a 12.1 vol% ILFR-fBNNS content with TC enhancement of 478%, and reductions of up to 68.9% and 42.3% by microscale combustion calorimetry (42.4% and 37.7% by cone calorimeter) in peak heat release rate (PHRR) and total heat release (THR) respectively compared to neat EP.