Graphite infused ionic liquid greases

Abstract

Electrically conductive lubricating greases are vital in improving the efficiency of electric motors as they can reduce friction and wear as well as avoiding electrical arcing at the same time. In this study, electrically conductive greases were produced using two ionic liquids (ILs), namely, 1-ethyl-3-methylimidazolium acetate ([EMIm] [Ac]) and 1-ethyl-3-methylimidazolium trifluoromethansulfonate ([EMIm][TFMS]) in combination with solid lubricants, i.e. polytetrafluoroethylene and graphite. The electrical and thermal conductivities as well as lubricities of these two IL based greases were measured and compared to conventional mineral oil based greases of the same compositions. Results show that the electrical conductivities of IL based greases produced in this study are comparable to commercially available conductive greases, which are two orders of magnitude higher than mineral oil based greases of the same compositions. The friction and wear resistances of IL based greases are also improved compared to mineral oil based greases. Among the three base liquids for greases, [EMIm][TFMS] performs best; it produces greases that have lower friction coefficients, smaller wear scars as well as higher electrical and thermal conductivities.