Ionic liquids with ammonium cations as lubricants or additives

Abstract

A new class of more effective lubricants could lead to huge energy savings. Limited recent literature has suggested potential for using room-temperature ionic liquids as lubricants, however, only a few out of millions (or more) of species possible have been evaluated. In this study, a series of new protic alkylammonium ionic liquids were synthesized by neutralization and metathesis reactions, and have demonstrated promising lubricating properties as neat lubricants or lubricant additives, particularly for use with difficult-to-lubricate metals like aluminum. More than a 30% friction reduction was observed with ammonium-based ionic liquids compared to conventional hydrocarbon oils in reciprocating sliding tests of 52100 bearing steel on aluminum alloy 6061-T6511. The inherent polarity of ionic liquids is believed to provide strong adsorption to contact surfaces and can form a boundary lubricating film leading to friction and wear reductions. Other advantages of ionic liquids include (1) negligible volatility, (2) high thermal stability, (3) non-flammability, and (4) better intrinsic properties that may eliminate the need for more complex and expensive additive packages. With very flexible molecular structures, this new class of lubricants, particularly ammonium-based ionic liquids, can be tailored to fit a variety of applications.

Ionic liquids as an additive in fully formulated wind turbine gearbox oils

“…Material pairs such as steel/steel, steel/SiO 2 , steel/aluminium, steel/copper, steel/Si(100), steel/sialon, steel/titanium, sialon/Si 3 N 4 and steel-PVD coatings (TiN, DLC and CrN) have been explored using pyridinium, imidazolium, phosphonium or ammonium as cation combined with anions such as hexafluorophosphate (PF 6 ), tetrafluoroborate (BF 4 ), CF 3 SO 3 , (C 2 F 5 ) 3 PF 3 (or FAP) and (CF 3 SO 2 ) 2 N (or NTf 2 ) [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. The most common anions examined in the tribology literature are BF 4 and PF 6 , but their hydrolytic instability and tendency to produce corrosive HF have been reported [27]. Merck KGaA has developed a new category of ILs using the FAP anion, which has an improved hydrolytic stability [28].…”

“…The friction and wear behaviour of ILs as additive or as pure lubricant have been studied using synthetic and mineral oils, or even fully formulated oils, as base oils or reference samples [27,[33][34][35] . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 The additivation value of fully formulated oils with ILs needs further consideration and research.…”

Ionic Liquids Then and Now: From Solvents to Materials to Active Pharmaceutical Ingredients

“…ILs are evolving from electrochemical and general solvents, 17,18 to novel materials in diverse applications such as specialized solvents, 19 lubricants, [20][21][22] thermal fluids, 23 magnetic fluids, [24][25][26] optical fluids, 27 propellants, 28,29 etc. Interdis- 36 Bioniqs, 37 etc.).…”

Assessing Boundary Film Forming Behavior of Phosphonium Ionic Liquids as Engine Lubricant Additives

“…Since 2001, many studies have reported on the tribological properties of ionic liquids (ILs) as an additive in mineral and/or synthetic base oils [3,[6][7][8][9][10], and others on their use as engine lubricants [3,4,7,11,12]. ILs have some key inherent properties that make them suitable for an engine environment, such as high thermal stability, very low volatility, non-flammability, detergency in being a solvent, they are non-corrosive, have good wettability, and excellent tribological performances [3,7].…”

“…ILs have some key inherent properties that make them suitable for an engine environment, such as high thermal stability, very low volatility, non-flammability, detergency in being a solvent, they are non-corrosive, have good wettability, and excellent tribological performances [3,7]. In this article, the authors present their recent experimental work on the assessment of boundary film forming behavior of two phosphonium-based ILs as additives in an engine-aged lubricant.…”