Covalent hybrid of graphene and silicon dioxide and reinforcing effect in rubber composites

For developing high performance graphene and silicon dioxide (SiO2)-based green rubber nanocomposites, dispersal of graphene nanosheets and SiO2 particles in rubber hosts and precise interface control are challenging due to their strong interlayer cohesive energy and surface inertia of graphene and the poor interaction with the organic matrix of SiO2. Here we report an efficient method to hybrid graphene nanosheets and SiO2 paticles. The SiO2 molecules were covalently bonded to the graphene surface via functionalized graphene, using plant polyphenol tannic acid (TA) as stabilizer and functional reagent, followed by further covalent derivatization through the Michael addition reaction between phenolic hydroxyl group on TA and primary amine on silane coupling agents modified SiO2. Through covalent hybridization, the SiO2 particles are uniformly decorated on the surface of graphene. The improved dispersion state of hybrid filler was attested by XRD, TEM and FTIR. SEM, DMA, mechanical analysis, thermal conductivity measurements and applied to characterize the hybrid nanocomposites. The results imply that the strategy of using hybrid fillers with covalent interactions has been established to be an efficient way to achieve high-performance rubber nanocomposites. The prominent confinement effect arising from nanosheets resulted in nearly 7.0% increase in the thermal conductivity of the highly synergistic hybridization graphene-SiO2 nanocomposites than that of the composite of graphene and SiO2 mixtures. The former possesses 45.4% increase in tensile strength and 32.6% in tear strength and 35.4% in compression set. The covalent hybridization nanocomposites exhibit excellent abrasive resistant capacity with nearly 36.6% increase than that of the composite of graphene and SiO2 mixtures. These results suggest that SiO2 and graphene covalent hybrid fillers have a high potential to be used in engineering composits.