Preparation And Properties Of Molybdenum Disulfide Coating For Reducing Surface Friction And Wear Of Fluororubber

Fluororubber?FKM?,with excellent oil resistance and medium resistance,can be applied as high-performance sealing material.Friction and wear behavior between FKM seals and metals under dynamic sealing condition has significant influence on effectiveness and service life of the seals.Molybdenum disulfide?MoS₂?,as an excellent solid lubricant,can be incorporated into FKM matrix as friction reducing filler to improve its tribological properties.However,the mechanical properties of FKM may decrease with addition of a great quality of MoS₂.Therefore,in this study,FKM/MoS₂ coating dispersion was prepared by liquid-phase sonication method,and then fabricated on the surface of FKM matrix by dip coating method.Furthermore,the friction coefficient and wear volume of the matrix surface were significantly reduced with minor addition of MoS₂,and the coating had no negative effect on the mechanical properties of FKM matrix.Firstly,the exfoliation effect of MoS₂ by liquid-phase sonication in different solvents including acetone,ethyl acetate,butyl acetate,dimethylformamide,cyclohexanone and N-methyl pyrrolidone was compared.The exfoliated MoS₂ was characterized by XRD,Raman spectra,UV-Vis and AFM analysis.The results show that N-methyl pyrrolidone has the best exfoliation effect on MoS₂.The average thickness and transverse size of MoS₂ are 3nm and 400 nm,respectively.In order to enhance the interfacial interaction between MoS₂and FKM,MoS₂ was modified by 1-dodecanethiol and L-cysteine,respectively.The modified MoS₂ was characterized by FT-IR,XPS,Raman spectra,XRD and TGA analysis.Secondly,FKM/MoS₂ coating dispersion was prepared and coated on the surface of FKM matrix by dip coating method.The effects of FKM concentration,MoS₂ content,coating times,crosslinking-agent concentration,immersion time and hardness of FKM matrix on the surface morphology,friction coefficient and wear volume of the matrix were studied.The results show that the friction coefficient and wear volume of the FKM matrix with coating are0.38 and 112.1mm³,respectively,which are 71.1%and 20.0%lower than those before coating when the FKM concentration in the coating dispersion is 30mg·ml^-1,and the content of molybdenum disulfide is 4.5wt%,and the number of coating cycles is 4,and the concentration of crosslinking agent is 0.4mg·ml^-1.The wear volume of FKM matrix with coating containing 4.5wt%MoS₂ modified with L-cysteine was reduced by 24.8%compared with the uncoated FKM matrix,indicating the wear resistance of the matrix was significantly improved.In addition,the amount of MoS₂ used by surface coating is much less than that by mechanical blending,however,showing better tribological properties on the surface of FKM matrix.