Homogeneous dispersion and a good interface between polymer and filler is crucial to obtain high-performance polymer composites. In this work, we use a novel method employing organic aminopropyl-functionalized nanosilica sols (OAS-sols) to functionalize graphene oxide (GO) and thereby synthesize OAS covalently grafted graphene hybrid nanosheets (OAS-graphene). The spherical OAS covalently attached on the two-dimensional (2D) nanosheet GO surfaces creates OAS-graphene hybrids, which have large surface areas and homogeneous amino active sites distributed on the nanosheets. The OAS-graphene gave an improved dispersion and interface compatibility as well as a decreased thermal interfacial resistance. As a result, the thermal conductivity and mechanical properties of the epoxy nanocomposites were significantly improved at low loading while maintaining high electrical insulative properties.

Octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) was synthesized using three-step method and used to modify o-cresol-novolac epoxy resin (ECN) for printed circuit board. The influence of OAPS on the reactivity and the final properties of the hybrid networks were evaluated. The intercrosslinking reaction between ECN and OAPS was confirmed by Fourier transform infrared spectra. The ECN/OAPS hybrids have better impact strength, higher electrical resistivity and thermal stability, lower water absorption than the unmodified ECN. The volume resistivity and surface resistivity of the hybrids increase by an order of magnitude or more compared to the neat epoxy. The thermal stability of the hybrids improves by the incorporation of OAPS; the initial decomposition temperature and char yield show an increasing tendency up to 4 wt% loading of OAPS. The hybrids exhibit higher storage modulus and glass transition temperature (T_g) than the neat epoxy. The T_g of the hybrids greatly improves up to 153.3°C at 3 wt% content, much higher than 119.4°C of the neat epoxy. POLYM. COMPOS., 34:1753–1760, 2013. © 2013 Society of Plastics Engineers

Al₂O₃ nanoparticles were introduced to natural rubber (NR) to investigate its reinforcement effect on filled NR vulcanizates. The results show that Nano-Al₂O₃/NR nanocomposites exhibit significantly improved tensile strength, elongation at break, modulus, and tearing strength. Scanning electron microscopy analyses indicate that nanoparticles dispersed in NR matrix at nanoscale and show nano-reinforcement effect on NR vulcanizates. The aging resistances of filled NR vulcanizates improve. After aging test, tensile strength, tearing strength, and modulus improved, and elongation at break decreased. These attribute to the crosslink maturation reactions, which result in the conversion of polysulfidic linkages into disulfidic and monosulfidic ones. The acid and alkaline resistances of nano-Al₂O₃-filled NR vulcanizates improve compared with that of unfilled NR systems. After acid and alkaline test, tensile strength and elongation at break improve, and modulus decrease. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers