Effects of functionalization and silane modification of hexagonal boron nitride on thermal/mechanical/morphological properties of silicon rubber nanocomposite

Hexagonal boron nitride (h-BN) nanoparticles could induce interesting properties to silicone rubber (SR) but, the weak filler-matrix interfacial interaction causes agglomeration of the nanoparticles and declines the performance of the nanocomposite. In this work, h-BN nanoparticles were surface modified using vinyltrimethoxysilane (VTMS) at different concentrations. Before silane modification, h-BN nanoparticles were hydroxylated using 5 molar sodium hydroxide. The nanoparticles were characterized to assess success of silane grafting. The pure and modified h-BN nanoparticles were applied at 1, 3 and 5 wt% to HTV silicon rubber (SR). The curing, thermal, mechanical and morphological properties and hydrophobicity of the nanocomposites were evaluated. The morphology of the SR nanocomposites was characterized using AFM and FE-SEM analysis. It was found that silane grafting on the h-BN nanoparticles improves crosslink density but declines curing rate index (CRI) of the SR nanocomposite (at 5 wt% loading content) by 0.7 (dN m) and 3.5%, respectively. It also increased water contact angle of the nanocomposites from 97.5° to 107°. The improved nanoparticle-rubber interfacial interactions caused better dispersion of h-BN nanoparticles in SR matrix (at 5 wt%) that enhanced the elongation at break, modulus at 300% and Tg of the SR nanocomposites.