In situ reduction and functionalization of graphene oxide to improve the tribological behavior of a phenol formaldehyde composite coating

The development of a phenol formaldehyde/graphene (PF–graphene) composite coating with high performance is desirable but remains a challenge, because of the ultrahigh surface area and surface inertia of the graphene. Herein, we synthesized PF–graphene composites by the in situ polymerization of phenol and formaldehyde with the addition of graphene oxide, resulting in improved compatibility between the graphene and phenolic resin (PF) matrix and endowing the phenolic resin with good thermal stability and excellent tribological properties. Fourier-transform infrared (FTIR) spectra and X-ray diffraction (XRD) patterns demonstrated that the graphene oxide was reduced during the in-situ polymerization. The PF–graphene composites were sprayed onto steel blocks to form composite coatings. The effects of an applied load and of the sliding speed on the tribological properties of the PF–graphene composite coating were evaluated using a block-on-ring wear tester; in addition, the worn surface and the transfer film formed on the surface of the counterpart ring were studied by scanning electron microscopy (SEM). The results show that the PF–graphene composite coating exhibited enhanced tribological properties under all tested conditions.