The Fabrication And Study Of Mechanism Of High-performance Reduced-friction,wear-resistant And Anti-corrosion Graphene/Fluorocarbon Resin Composite Coating

The friction,wear,and corrosion of metals has long caused significant economic losses and energy consumption in many fields.Among many protection strategies,the application of organic composite coatings on metal surfaces is an efficient,simple and cost-effective method.Fluorocarbon resins（FEVE）are often used as anti-corrosion coatings because of their strong C-F bonding backbone,excellent chemical resistance,low friction and extra-long weathering resistance.It is widely used in the coating and lining of various high-grade coils,conveying pipelines and precision instruments,etc.However,pores and gaps due to solvent volatilization during FEVE curing limit the growing demand for coating performance.The performance of FEVE coatings can be enhanced by introducing fillers,and graphene is an excellent reinforcing filler with excellent mechanical properties,low interlayer shear and high barrier properties.However,to bring out the excellent wear and corrosion resistance of graphene-enhanced fluorocarbon composite coatings,the challenges of easy agglomeration and poor compatibility of graphene in FEVE due to the intrinsic van der Waals forces of graphene and the low reactivity of FEVE need to be overcome.In this paper,to improve the dispersion and interfacial compatibility of graphene in fluorocarbon coatings,we optimized the preparation process of PS-PVP@r GO and its fluorocarbon composite coatings based on the existing graphene powder（PS-PVP@r GO）with polyvinylpyrrolidone（PVP）as a bridging agent to load polystyrene（PS）on the surface of reduced graphene oxide（r GO）.The nitrogen-containing groups were also introduced into PS-PVP@r GO powder to improve its interfacial interaction with FEVE matrix,thus enhancing the friction reduction,wear and corrosion resistance of graphene fluorocarbon composite coatings.The details and main results are as follows:（1）PS-PVP@r GO powders were prepared by emulsion polymerization and filled with FEVE to obtain PS-PVP@r GO/FEVE composite coatings.The high PS loading PS-PVP@r GO powder was optimized by the preparation process and its physical and chemical properties and its redispersion stability in xylene,the solvent of the coating,were characterized;the high performance PS-PVP@r GO fluorocarbon composite coating was prepared by determining the grinding time of the fluorocarbon coating preparation;the mechanical properties,frictional wear properties and corrosion resistance of the PS-PVP@r GO/FEVE composite coating were investigated.The optimum doping amount of PS-PVP@r GO was obtained by comparing the mechanical properties,frictional wear properties and corrosion resistance of PS-PVP@r GO/FEVE composite coatings.The results showed that the PS polymerization reaction occurred fully when the p H value of the reaction system was stabilized at 9 and the best loading effect on the graphene surface,and the PS-PVP@r GO powder could be uniformly dispersed in xylene and maintained excellent dispersion stability for 160 h.During the preparation of the graphene fluorocarbon composite coating,the fineness of the coating reached the use standard after 3.5 h of grinding time,and the optimum doping amount was 0.5μm.The average friction coefficient and wear rate were reduced by 26.9%and 45%,respectively,compared with FEVE coating;the impedance value and low-frequency impedance modulus of 0.75wt%PS-PVP@r GO/FEVE composite coating were 18 and 20 times higher than those of FEVE coating.（2）Firstly,graphene oxide was modified with polyetheramine（D400）by in-situ grafting method to obtain aminated graphene,and then PS-PVP@NH₂-r GO was loaded on its surface and filled into FEVE to obtain PS-PVP@NH₂-r GO/FEVE composite coating.The physical and chemical properties of PS-PVP@NH₂-r GO were investigated and its redispersion stability in xylene was examined.By comparing the friction reduction,wear and corrosion resistance of PS-PVP@NH₂-r GO fluorocarbon resin coating with PS-PVP@r GO at the same doping amount,the effect of the introduction of nitrogen-containing groups on the interfacial interaction between PS-PVP@-r GO and FEVE was evaluated,and the enhancement mechanism of PS-PVP@NH₂-r GO on FEVE coating was explored.The results showed that the N element content in PS-PVP@NH₂-r GO was enhanced by 34.9%;compared with the PS-PVP@r GO/FEVE composite coating,the average friction coefficient and wear rate of PS-PVP@NH₂-r GO/FEVE composite coating were reduced by 5.06%and 37.24%,respectively,and the impedance value and low-frequency impedance modulus were enhanced by 38 times and 47 times.Mechanistic analysis showed that the improvement of the wear and corrosion resistance of the FEVE composite coating was attributed to the good dispersion of PS-PVP@NH₂-r GO in FEVE and the enhancement of the interfacial interaction between PS-PVP@NH₂-r GO and FEVE by the introduction of nitrogen-containing groups.（3）PS-PVP@N-r GO powder was prepared by introducing nitrogen-containing groups into PS-PVP@r GO using urea-assisted ball milling method and filled into FEVE to obtain PS-PVP@N-r GO/FEVE composite coating.To study the physical and chemical properties of PS-PVP@N-r GO and to examine its redispersion stability in xylene.The thermal evolution of the PS-PVP@N-r GO/FEVE composite coating during curing was monitored by comparing the friction reduction,wear and corrosion resistance performance of the PS-PVP@N-r GO/FEVE composite coating with the same amount of PS-PVP@r GO incorporating DSC technique to evaluate the effect of the introduction of nitrogen-containing groups on the interfacial interaction between PS-PVP@-r GO and FEVE and to explore the enhancement mechanism of PS-PVP@N-r GO on FEVE coating.The results show that the N element in PS-PVP@N-r GO is present on the surface of r GO in the form of graphite N.The average friction coefficient and wear rate of PS-PVP@N-r GO/FEVE were reduced by 2.53%and 31.67%,respectively,compared with the FEVE coating,and the impedance value and low frequency impedance modulus of the 0.75wt%PS-PVP@N-r GO/FEVE composite coating were 37 and 67 times higher than those of the 0.75wt%PS-PVP@r GO/FEVE composite coating,respectively.The DSC results showed that the nitrogen-containing groups introduced in PS-PVP@N-r GO reacted with the curing agent of the fluorocarbon coating.The mechanism analysis showed that the enhancement of the wear and corrosion resistance of the FEVE composite coating was attributed to the good dispersion of PS-PVP@N-r GO in FEVE and the enhancement of the interaction between PS-PVP@N-r GO and FEVE interface by the introduction of nitrogen-containing groups.