Study On Ionic Liquid As Potential Lubricant Additive

Ionic liquids are often molten salts at room temperature,also known as green solvents.They have the advantages of being stable,difficult to decompose,not easy to volatilize,and strong in designability when being heated.Ionic liquids have attracted the attention of many scientific researchers.However,ionic liquids often show large metal corrosivity as base oil,which makes them affected in tribological applications.Ionic liquids are used as additives for polar base oils.In order to understand the influencing factors of tribology of polar substances,the quantitative structure tribo-ability relationship of ionic liquids in dimethyl sulfoxide was studied.The main results are as follows:(1)The antiwear properties of 23 kinds of ionic liquids in DMSO were tested.Eight physical and chemical structural parameters of 23 kinds of ionic liquids without solvent were simulated using Hartree-Fock(HF)ab initio algorithm and the anti-wear structure-activity relationship model with good prediction performance was constructed.The model result shows that molecular entropy is the main parameter that effects on the wear resistance of the system.The formation of a stable spatial network structure between ionic liquid and dimethyl sulfoxide is the main reason for good anti-wear performance.(2)The anti-wear structure-activity relationship model was constructed between eight physical and chemical structural parameters and anti-wear scales of 23 ionic liquids in dimethyl sulfoxide using HF ab initio algorithm and polarized continuous media model.The model results show that molecular entropy and solvated molecular volume of the ionic liquid are the main structural parameters that effect on the anti-wear of the system.The smaller the molecular entropy value and the molecular volume after solvation,the better anti-wear property.(3)The structure-activity model of eight physical and chemical structure parameters and friction-reducing parameters in dimethyl sulfoxide was constructed.The model results show that molecular specific heat capacity and molecular solvated volume of the ionic liquid are the main structural parameters related with the friction-reducing performance of the system.The larger the molecular specific heat capacity or the smaller the molecular volume of the ionic liquid,the better the friction-reducing performance.(4)Based on the anti-wear data and friction-reducing data obtained from the friction test,the tribological properties of ionic liquids is comprehensively analyzed.The results show that[Bmim]Cl and[Bmmim]PF₆have great anti-wear and frictionreducing properties in dimethyl sulfoxide.