'Product Blog'

Part 1: CYPHOS® IL 109

In a recent blog [1] we reviewed some electrochemical applications of room-temperature ionic liquid (RTIL) trihexyl(tetradecyl)phosphonium bis(trifluoromethanesulfonyl)amide 1 aka CYPHOS® IL 109 (CAS # 460092-03-9, Strem Catalog No: 15-6370, Strem Catalog No: 96-6520, Ionic Liquid Kit 3: CYPHOS® IL Phosphonium Salt Kit):

The focus of this blog is to briefly review some literature results on the testing of 1 in lubrication.

Thus, the effect of IL lubrication for aluminum/steel systems was shown to be highly dependent on the applied load and the IL structure. Up to a load of 30 N the lowest wear coefficient was observed for trihexyl(tetradecyl)phosphonium diphenylphosphate IL while 1 was able to form a more tenacious tribolayer above 30 N resulting in the lowest wear [2].

In a study aimed at comparison of some phosphorus and fluorine containing IL lubricants for steel on aluminum [3] it was shown that the chemistry of both the anion and cation are critical in achieving maximum wear protection. The wear data indicated that 1 was one of the two best performing IL lubricants.

In another interesting study [4] the halogen-free ionic liquids showed inferior lubricity compared with the halogen-containing ionic liquids for steel-on-steel sliding contacts, though they did not cause any remarkable corrosion. In comparison, 1 exhibited anti-wear AND corrosion-inhibition effects outperforming N-methyl-N-propyl-piperidinium-bis (trifluoromethanesulfonyl)imide ([PP13][TFSI]).

The miscibility and antiwear performance of various phosphonium (including 1), imidazolium, and pyrrolidinium ionic liquids in a range of polar and nonpolar base oils for steel on aluminum was determined [5]. It was observed that the fluorine-containing IL blends might be interacting with some base oils (VO, TMP, and PE) and this observation might explain why, although the fluorine-containing IL perform as well or better than P_6,6,6,14 DPP, P_6,6,6,14 (iC₈)₂PO₂, or P_6,6,6,14 BEHP as neat lubricants, when added into above-mentioned particular oils, even at 0.20 mol/kg, they had little effect on the wear of the steel on aluminum system. If the IL is interacting strongly with the base oil it will not be available to preferentially migrate to and segregate at the aluminum surface to form a protective IL film, which would lead to a reduction of the wear rate.

In another study [6] three out of five phosphonium ILs, including 1, showed corrosion activity, likely related to water presence as an impurity leading to radical formation and HF generation. It was noted, however, that two of those ILs, including 1, would be very interesting if a conductive lubricant was desired. In that case addition of corrosion inhibitors would be required.

We have briefly reviewed just a handful of publications on the testing of phosphonium ionic liquids, including 1, in lubrication. Many more publications of interest on this subject matter were published after 2016 and we will make an effort to review those publications as well in subsequent blogs. Stay tuned!

References

1.     CYPHOS® IL 101 in electrochemical applications
2.     Tribol. Lett. 2010, 40, 2, 279-284.
3.     Phys. Chem. Chem. Phys. 2012, 14, 22, 8224-8231.
4.     Proc. IME J. J. Eng. Tribol. 2012, 226, 11, 991-1006.
5.     ACS Appl. Mater. Interfaces 2013, 5, 22, 11544-11553.
6.     Tribol. Int. 2016, 95, 118-131.

Featured Products

15-6370 Trihexyl(tetradecyl)phosphonium bis(trifluoromethanesulfonyl)amide, min. 97% CYPHOS® IL 109 (460092-03-9)

96-6520 Ionic Liquid Kit 3: CYPHOS® IL Phosphonium Salt Kit