Covalently bonded interface in polymer/boron nitride nanosheet composite toward enhanced mechanical and thermal behaviour

This experimental study aimed to enhance the mechanical and thermal properties of BN (hexagonal boron nitride) nanosheet-reinforced high-density polyethylene by functionalizing its interface. The challenges associated with this nanocomposites are its poor dispersion and weak interface. Accordingly, to improve the load transfer at the interface, BN nanosheets were chemically modified with silane functional groups ((3-aminopropyl)tri-ethoxy silane), making it possible to form covalent bonds between the maleic anhydride-grafted polyethylene and nanosheet. Consequently, three different types of nanocomposite samples were fabricated based on the covalently bonded or non-bonded interface. Two nanocomposite configurations featured a non-bonded interface between the nanofiller and PE matrix (p-BN/PE and (silane functionalized) s-BN/PE). In contrast, the third configuration had a covalently bonded interface (silane-functionalized h-BN + maleic anhydride-grafted PE, i.e., PE-g-BN). According to the zeta potential analysis, the silane-functionalized BN nanosheets were stable suspensions and uniformly dispersed in the polymer matrix. The tensile and flexure strength of the nanocomposites showed over 100% improvement due to the covalently bonded interface. The lamellae structure of PE in the bonded interface samples was responsible for achieving higher mechanical strength in the nanocomposites. Furthermore, the thermal conductivity of the nanocomposites was significantly affected by the type of interfacial bonding, BN wt%, and operating temperature.