Epoxy/p-phenylenediamine functionalized graphene oxide composites and evaluation of their fracture toughness and tensile properties

In an attempt to enhance the mechanical properties of epoxy/graphene-based composites, the interface was engineered through the functionalization of graphene oxide (GO) sheets with p-phenylenediamine; this resulted in p-phenylenediamine functionalized graphene oxide (GO-pPDA). The morphology and chemical structure of the GO-pPDA sheets were studied by spectroscopic methods, thermal analysis, X-ray diffraction, and transmission electron microscopy. The characterization results show the successful covalent functionalization of GO sheets through the formation of amide bonds. In addition, p-phenylenediamine were polymerized on graphene sheets to form crystalline nanospheres; this resulted in a GO/poly(p-phenylenediamine) hybrid. The mechanical properties of the epoxy/GO-pPDA composite were assessed. Although the Young's modulus showed improvement, more significant improvements were observed in the strength, fracture strain, and plane-strain fracture toughness. These improvements were attributed to the unique microstructure and strong interface between GO-pPDA and the epoxy matrix. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43821.