Mechanical and thermal properties of POSS-g-GO reinforced epoxy composites

Polyhedral oligomeric silsesquioxane (POSS) was synthesized via the hydrolytic condensation of gamma-aminopropyltrimethoxysilane in the tetrahydrofuran solution catalyzed by concentrated hydrochloric acid and was further used as the grafting agent to react with graphite oxide (GO). The grafted product, which referred to as POSS-g-GO, was used to modify epoxy resin (EP) matrix. The epoxy/POSS-g-GO nanocomposites were fabricated using ultrasonication and the cast molding method and confirmed by Fourier transform infrared spectroscopy, X-ray diffraction, dynamic mechanical analysis (DMA), and thermogravimetric analysis techniques. The results revealed that the incorporation of a small amount of POSS-g-GO caused a significant improvement in ultimate tensile strength, impact strength and roughness. With 2 wt% POSS-g-GO ultimate tensile strength and flexural strength of the composites were improved by 24.8 and 56.6 %, respectively. The impact strength was 42.97 kJ/m(2), which is 2.5 times higher than that of the pure EP (17.49 kJ/m(2)). The DMA results showed that the moduli of the nanocomposites in glass and rubbery states were significantly higher than those of the control epoxy. It indicated that incorporation of POSS-g-GO into epoxy networks was the efficient load transfer between the POSS-g-GO additives and epoxy matrix through covalent links. Morphological structure of the impact fracture surface of the epoxy/POSS-g-GO composites was observed by scanning electron microscope, as well.