Preparation Of Graphene/Silane Modified Resin Self-lubricating Coating And The Study On Its Tribological Properties

WPU has a widespread application prospects in the filed of engineering coating preparation due to its good mechanical properties,easy modification and no pollution.However,pure WPU coatings are difficult to meet the application requirements of antifriction and wear resistance under strict condition.By adding molybdenum disulfide,carbon nanotube,polytetrafluoroethylene and other lubricants,the tribological properties of the polymer can be improved.Graphene is widely uesd in the lubrication field because of its extremely low coefficient of friction,atomically smooth surface and extremely low interlayer shear performance,especially as a nano additive to improve the tribological properties of polymers.However,graphene is extremely easy to form agglomeration and difficult to disperse in most solvents,which limits its outstanding performance.Graphene has great dispersion in polymer and good interface compatibility with the polymer can effectively enhance the properties of composite materials.So it is critical to use a suitable method for surface modification of graphene to inhibit its agglomeration in polymers.In addition,graphene is an two-dimensional material with anisotropic,its distribution in the polymer can ensure its excellent mechanical properties in composite materials.Therefore,the graphene oxide(GO)is modified by Fe₃O₄to make modified GO aligned distribution in the coatings under the induction of a magnetic field.The impact of aligned distribution on the tribological performance of the composite coating is studied.In this study,GO and Fe₃O₄are modified by chemical grafting,and the modified GO and Fe₃O₄are connected through covalent bonds to form GO@Fe₃O₄.The GO and GO@Fe₃O₄are characterized by FTIR,XPS and TEM.The dispersibility of GO and GO@Fe₃O₄in WPU are studied respectively.Finally,aligned and non-aligned GO@Fe₃O₄/WPU coatings are prepared,and tribological experiments are carried out on the coatings with different mass fractions.The antifriction and wear resistance mechanism of GO@Fe₃O₄/WPU coatings is analyzed according to the results of friction experiments and the characterization of SEM and EDS.Experimental results are as follows:(1)The modified GO and Fe₃O₄are successfully connected by covalent bonds,and the Fe₃O₄is distributed evenly on the surface of GO.GO@Fe₃O₄has better dispersibility than GO in WPU.(2)GO@Fe₃O₄has played a great role in reducing friction and wear resistance in WPU.As the mass fraction of GO@Fe₃O₄increasing,the coatings have better tribological properties when the addition amount of GO@Fe₃O₄is 0.5wt%.When the mass fraction exceeds 0.5wt%,the friction coefficient and wear rate of the coatings increase gradually,but they are still lower than pure WPU.(3)The trinological properties of WPU can be enhanced by the GO@Fe₃O₄of non-aligned distribution.The reason is that the-NCO functional group on the surface of GO@Fe₃O₄can be chemically combined with the carbamate in WPU,thereby improving the interface interaction between GO@Fe₃O₄and WPU.At the same time,the spherical Fe₃O₄nanoparticles loaded on the surface of GO can fill the worn area of the friction pair surface and play a role of self-repairing in coatings.(4)In comparison to the non-aligned and pure WPU coatings,the friction coefficient and wear rate of aligned GO@Fe₃O₄/WPU coatings are reduced.The tribological properties of composite coatings are the best when the addition of GO@Fe₃O₄is 0.5wt%.When the addition of GO@Fe₃O₄is too high,the coating is easy to peel off on account of the agglomeration of GO@Fe₃O₄during friction process,which makes the tribological properties of the coatings worse.(5)The uniform and aligned distribution of GO@Fe₃O₄in the coatings can extend the internal crack propagation path and delay the formation of worn chips,thus enhancing the wear resistance of the coatings.The excellent tribological performance of the aligned composite coatings come from its ability to promote the formation of uniform and continuous transfer film on the friction counterpair,avoiding direct friction between the friction counterpair and the composite coatings.