Multi-layer graphene oxide synergistically modified by two coupling agents and its application in reinforced natural rubber composites

Multi-layer graphene oxide (MGO) was co-modified with bis-(P,P-bis-ethylhexyldiphosphato)-ethanediolato titanate triethanolamino chelate solution (NDZ-311w) and bis-(-triethoxysilylpropyl)-tetrasulfide (Si-69). Then the co-modified MGO was incorporated into natural rubber (NR) by conventional two-roll mill mixing to prepare MGO/NR composites. The large macromolecule of NDZ-311w is able to efficiently intercalate the layers and increase the interlamellar space of MGO, subsequently resulting in the exfoliation of MGO into thinner sheets with better dispersity. Moreover, the oxygen-containing polar groups of MGO can be largely consumed by Si-69, which enhances the interfacial interaction between MGO and the NR matrix and improves the mechanical properties of the MGO/NR composites. Compared to pure natural rubber, the tensile strength, the stress at 300% strain, and tear resistance of co-modified MGO/NR composites are increased by 26%, 98% and 15%, respectively.