Towards Phosphorus Free Ionic Liquid Anti-Wear Lubricant Additives
AbstractThe development of improved anti-wear additives would enable the use of lower viscosity oils that would lead to improved efficiency. Ionic liquids have the potential to be this type of new anti-wear additive. However, currently the best performing ionic liquids that are miscible in non-polar base oils, the phosphonium phosphates, contain phosphorus on both the cation and anion. Manufacturers are seeking to reduce the presence of phosphorus in oils. Here, as a first step towards phosphorus-free anti-wear additives, we have investigated ionic liquids similar to the phosphonium phosphates but having either a phosphorus-free cation or anion. Two quaternary ammonium phosphates (N6,6,6,14)(BEHP) and (N8,8,8,8)(BEHP) and a phosphonium silyl-sulfonate (P6,6,6,14)(SSi) were compared to a phosphonium phosphate (P6,6,6,14)(BEHP) and a traditional zinc dithiophosphate (ZDDP) as anti-wear additives in mineral oil. The change from a phosphonium to a quaternary ammonium cation drastically reduced the miscibility of the Ionic liquid (IL) in the oil, while the change to a smaller silicon containing anion also resulted in limited miscibility. For the pin-on-disk wear test conditions used here none of the ionic liquids outperformed the ZDDP except the (P6,6,6,14)(BEHP) at a relatively high loading of 0.10 mol·kg−1 (approximately 8 wt%). At a more moderate loading of 0.025 mol·kg−1 the (P6,6,6,14)(SSi) was the best performing ionic liquid by a significant amount, reducing the wear to 44% of the neat mineral oil, while the ZDDP reduced the wear to 25% of the mineral oil value. Electron microscopy and energy dispersive X-ray spectroscopy showed that the presence of a silicon containing tribofilm was responsible for this protective behaviour, suggesting that silicon containing ionic liquids should be further investigated as anti-wear additives for oils. View Full-Text
Share & Cite This Article
Somers, A.E.; Yunis, R.; Armand, M.B.; Pringle, J.M.; MacFarlane, D.R.; Forsyth, M. Towards Phosphorus Free Ionic Liquid Anti-Wear Lubricant Additives. Lubricants 2016, 4, 22.
Somers AE, Yunis R, Armand MB, Pringle JM, MacFarlane DR, Forsyth M. Towards Phosphorus Free Ionic Liquid Anti-Wear Lubricant Additives. Lubricants. 2016; 4(2):22.Chicago/Turabian Style
Somers, Anthony E.; Yunis, Ruhamah; Armand, Michel B.; Pringle, Jennifer M.; MacFarlane, Douglas R.; Forsyth, Maria. 2016. "Towards Phosphorus Free Ionic Liquid Anti-Wear Lubricant Additives." Lubricants 4, no. 2: 22.
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.