Synthesis Of Liquid Crystal Additives And Study Of Their Behaviors Based On The Formulation Of Lubricating Oil

Liquid crystal is an ordered intermediate phase which exist in the process of solid to liquid conversion.This paper firstly studies the theoretical explorations and experimental evidences of thermotropic liquid crystals used as lubricating oil additives.Then investigated the effect of liquid crystal phase on the tribological behavior as additives.Designed and synthesized of a series of new liquid crystal compounds with wide mesophase temperature range.Finally the influence of molecular length changes on the phase state of liquid crystals was investigated at the molecular level,which in turn affected the tribological properties as lubricant additives.From the view of the performance of lubricants,the physicochemical properties of oil could be changed with temperature are caused by the phase transition of liquid crystal additives.Innovatively associates the thermodynamic concept of liquid crystal with the properties of the blended lubricant and verifies the mechanism,which will be used for the controllability of temperature for the tribological behavior of lubricant additives.This research provides a new idea and certain theoretical and experimental basis for liquid crystals for lubricating oil additives,and brings a new perspective for the development and application of liquid crystal tribology.This subject involves crossover and application of multidisciplinary.In terms of liquid crystal compounds.The liquid crystal compounds were synthesized using organic synthesis method.The molecular structure was characterized by NMR,IR and MS.The thermodynamic properties of liquid crystal compounds were determined by DSC.The mesogenic phase was analyzed by POM.The microstructure of the liquid crystal was observed using AFM.In terms of evaluation of oil products containing liquid crystal.Four-ball machine,UMT-Tribolab were used for friction test.3D profiler was used to observe the wear surface.Rheometer was used to test viscosity change of oil.The oil film thickness tester was used to measured oil film thickness and 3D infrared imaging was used to the analysis of surface residue.The evaluation of tribological performance and mechanism analysis of liquid crystals used as lubricating oil additives were carried out from various aspects.The details were as followed.The differences in tribological properties of four liquid crystal compounds used as lubricating oil additives were explored.Experiments show that nematic liquid crystal is more conducive to enhancing the strength of the oil film,making the oil film hard to break and the cholesteric liquid crystal is more conducive to reducing wear under the same conditions.The relationship and difference between them are closely related to the characteristics and molecular structure of their liquid crystal phase.Designed and synthesized a series of new liquid crystal compounds with wide mesogenic phase range.The change in molecular length could affect the phase transition temperature and mesogenic phase of the liquid crystal.The friction test shows that the width of the mesogenic phase is related to the lubrication effect.This result is verified in different base oils and different friction modes,which is shown universality.In addition,it can be observed that the addition of the liquid crystal additive can significantly reduce the wear debris and the wear on the friction pair.By introducing fluorine atoms,some liquid crystal compounds were modified to make changes in the liquid crystal phase,which greatly broaden the mesogenic phase range.The friction test shows that the lubricating effect of the liquid crystal additive could be abruptly changed within a specific temperature range.This specific temperature range is closely related to the mesogenic phase range.In summary,this research will facilitate the study of the controllability of temperature for tribological behavior.