Effects of surface-modified silica nanoparticles attached graphene oxide using isocyanate-terminated flexible polymer chains on the mechanical properties of epoxy composites

3-Aminopropyltriethoxysilane (APTES) surface-modified silica nanoparticles were attached to graphene oxide (GO) using isocyanate group-terminated flexible chains in order to synthesize silica nanoparticles with GO attached (SATPGO). The SATPGOs of various compositions were used as reinforcing fillers to prepare epoxy composites. Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy analyses confirmed the surface modification of silica nanoparticles after surface grafting with the silane coupling agent, 1,2,4-benzenetricarboxylic anhydride, followed by crosslinking of the surface-modified silica nanoparticles to GO. X-ray diffraction analysis confirmed the attachment of silica nanoparticles to fully exfoliated GO sheets. Transmission electron microscopy images revealed that the silica nanoparticles were introduced uniformly onto the GO sheets. The mechanical properties (impact and tensile properties) of the SATPGO/epoxy composites were dramatically enhanced with the addition of small amounts of SATPGO. The storage modulus of the SATPGO filled epoxy composites was higher than that of pure epoxy. The impact strength of the SATPGO (0.5 wt%)/epoxy composite improved by 154% at room temperature and by 92% at 77 K without any sacrifice of the tensile properties. Moreover, the tensile strength and modulus of the epoxy resin improved with SATPGO loading. The improvements of the thermal stability and mechanical properties were attributed to the synergistic effects of the silica nanoparticles, flexible polymer chains, and GO ternary system.