Deakin University
Browse

Towards phosphorus free ionic liquid anti-wear lubricant additives

Download (3.47 MB)
Version 2 2024-06-03, 23:14
Version 1 2017-04-06, 21:24
journal contribution
posted on 2024-06-03, 23:14 authored by Anthony SomersAnthony Somers, R Yunis, MB Armand, Jenny PringleJenny Pringle, DR MacFarlane, Maria ForsythMaria Forsyth
The 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.

History

Journal

Lubricants

Volume

4

Article number

ARTN 22

Location

Basel, Switzerland

Open access

  • Yes

eISSN

2075-4442

Language

English

Publication classification

C1 Refereed article in a scholarly journal

Copyright notice

2016 by the authors

Issue

2

Publisher

MDPI