Fabrication and characterization of graphene-reinforced waterborne polyurethane nanocomposite coatings by the sol–gel method

Functionalized graphene-reinforced polyurethane nanocomposite coatings were prepared using the sol–gel method. This method not only provides a “green” strategy for fabricating the graphene-based nanocomposites, but also realizes the covalent functionalization of graphene nanosheets with polymer matrix. The functionalization of graphene with conjugated organosilanes is favorable for improving mechanical and thermal properties of the nanocomposite coatings, which is mainly attributed to the homogeneous dispersion of functionalized graphene in the polymer matrix and strong interfacial interactions between the two components. A 71% increase in tensile strength and a 86% improvement of Youngʹs modulus are observed by the addition of 2.0 wt.% of functionalized graphene. The experimentally determined Youngʹs modulus corresponds well with the theoretical simulation under the hypothesis that the graphene sheets are randomly dispersed in the polymer matrix.