Surface Modification Of Graphene And The Properties Of Graphene / Epoxy Resin Composites

As a new carbon material, graphene has unique mechanical, optical, thermal and electrical properties, and it has broad application prospects in the biological, electronics and new energy fields. Graphene oxide (GO) is similar as graphene in structure, so it is often considered as the precursor of graphene. GO’s surface includes a plurality of hydrophilic oxygen-containing functional groups. However, GO is poor dispersed in some organic solvent, which limits its application in composites. The surface modification of GO has became one of the significant challenges. This paper focuses on the surface modification of GO sheets, preparation and study the behavior of graphene/epoxy composites.Firstly, carboxylated-GO (GO-COOH) was prepared using various methods, in order to increase the chemical reactivity and sites of the GO. In addition, we quantitatively detect the content of carboxyl groups of GO surface using two different approaches, titration and gravimetric method, respectively, in order to obtain GO-COOH material with the highest-COOH content. P-toluidine was covalently introduced onto the surface of GO sheets using direct and indirect amidation processes to obtain the amine-modified GO (MGO-1 and MGO-2). Successful grafting of p-toluidine to the graphitic framework of GO was confirmed using infrared spectroscopy (FT-IR) and ultraviolet-visible spectroscopy (UV-Vis). The X-ray photoelectron spectroscopy (XPS) showed the simultaneous reduction and modification. In addition, MGO-2 has greater thermostable and hydrophobic properties than MGO-1, with a water/air contact angle of～126.4°.Finally, graphene/epoxy composites were prepared by solution mixing method. The effect of different graphene (GO and MGO) and graphene loading on mechanical property and wear behavior of composites were studied. The effect of applied load on wear behavior of composites was investigated, and the observed morphology of tensile fracture and wear surface of composites were showed using a scanning electron microscope. These results show that MGO/epoxy composites obtained the improvement mechanical property and wear resistance.