Pyrylium- and pyridinum-based ionic liquids as friction modifiers for greases

The use of ionic liquids as lubricants or lubricant additives has been studied extensively over the past few decades. However, the ionic liquids considered for lubricant applications thus far have been part of a limited structural class of phosphonium- or imidazolium-type compounds. Here, new pyrylium- and pyridinium-based ionic liquids bearing long alkyl chains were prepared and evaluated as friction and wear-reducing additives in naphthenic greases. The physical properties of the synthetic ionic liquids and additized-naphthenic grease were measured. The tribological performance of the greases was measured using standard benchtop tests and shown, in some cases, to decrease friction compared to the base grease. The compatibility of the synthetic ionic liquids with the naphthenic greases is tentatively proposed to be a result of molecular structure and its potential influence on miscibility and tribological performance.