Functionalization of boron nitride nanosheets by diazonium salt for preparation of nanocomposites with high‐density polyethylene

Functionalization of boron nitride nanosheets (BNNSs) has always been a challenge due to its chemical inertness and anti‐oxidative properties. In a concentrated base environment, the B‐N bonds on the surface of BNNSs were broken to produce a large number of B‐OH and N‐H functional groups. Afterwards, aniline carbocation produced by decomposition of the diazonium salt was utilized to achieve high grafting content of Ph‐NH₂ groups onto the surface of BNNSs. Further, the amide reaction between amino and stearyl chloride verified the reactivity of Ph‐NH₂ groups on the surface of BNNSs, with the result that BNNSs were abundantly decorated by aliphatic chains at 22.9 wt% grafting yield. The surface aliphatic chains of BNNSs strongly improved the interfacial adhesion between the High‐density polyethylene (HDPE) matrix and the filler and provided an excellent dispersion of SC‐BNNSs in the HDPE matrix. Therefore, HDPE/SC‐BNNSs nanocomposites showed improved thermal stability, thermal conductivity, neutron shielding property and flexural modulus with no apparent reduction in tensile strength. When filler content exceeded 5 wt%, the HDPE/SC‐BNNSs nanocomposites showed a higher thermal decomposition temperature than the composites with pristine BNNSs fillers. POLYM. COMPOS., 40:2346–2356, 2019. © 2018 Society of Plastics Engineers