Two phosphonium cation-based ionic liquids (ILs) were studied as additive to a mineral oil. Solubility tests and TGA of neat samples were performed. Three concentrations of the ILs were used in the tribological tests. Base oil-ZDDP mixtures were used as comparison samples. Tribological tests were made using a reciprocating ball-on-disc configuration. Load ramp and Stribeck curve tests were also performed. The worn surface was studied by different techniques. The results showed similar and better friction reduction properties for ILs-or ZDDP-containing mixtures than the neat base oil. The [P 66614 ][(iC8) 2 PO 2 ] -containing mixtures outperformed the antiwear behavior of the other samples. XPS results showed different mechanisms of lubrication when using ILs or ZDDP.

This paper studies physicochemical properties (density, viscosity, corrosion, thermogravimetry, and conductivity) and tribological behavior of five phosphonium cation-based ionic liquids ([P 66614

This paper studies the wetting properties of seven phosphonium cation-based ionic liquids: trihexyltetradecylphosphonium bis (2,4,4-trimethylpentyl)

Tribological behavior of trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl) imide [P66614][NTf2] ionic liquid (IL) used as additive in a diester oil at concentrations of 0.25, 0.5 and 1 wt% was studied in this research. The IL solubility in the base oil was measured using the inductively coupled plasma mass spectrometry (ICP-MS) technique and corrosion analysis was done at room temperature at relative humidity of 49 77%. Tribological tests were conducted for 30 minutes at room temperature, 15 Hzfrequency, 4 mm of stroke length, a load of 80 N (corresponding to 2 GPa of maximum contact pressure) and relative humidity of 35-53%. Friction coefficient was recorded during tests and the wear scar was measured by confocal microscopy. Worn surface was also analyzed by SEM, EDS and XPS. Results showed that a saturated solution of [P66614][NTf2] in the base oil contains about 30 wt% of IL and corrosion activity for the highest concentration of IL (1 wt%) was not found after a 20-day test. Although the base oil and the mixtures had similar friction behavior, 1 wt% sample exhibited slightly lower wear volume than the base oil. Regarding surface analysis, SEM images exhibited similar wear track width (707-796 µm) and wear mechanism (adhesive) for all samples tested. In addition, the EDS spectra only showed the elements present in the steel. Finally, XPS study could not detect differences regarding iron chemical state. This mentioned similitude among the samples is consistent with the tribological behavior obtained.

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This paper studies the tribological performance of two phosphonium cation-based ionic liquids: trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl) phosphinate ([P6,6,6,14][(iC8)2PO2]) and trihexyltetradecylphosphonium bis(2-ethylhexyl) phosphate ([P6,6,6,14][BEHP]), as lubricant additive at 1 wt% to a polyalphaolefin. A comparison of their tribological behavior was made to that of one type of zinc dialkyldithiophosphate (ZDDP). Stribeck curve tests were made in a Mini Traction Machine (MTM) tribometer at entrainment speeds ranging from 2000 to 10 mm/s, 30 N-load, slide-to-roll ratio (SRR) of 50%, and temperatures of 40, 60, 80 and 100 ºC. Tribofilm formation tests were also conducted in the MTM at 100 ºC, load of 50 N, entrainment speed of 150 mm/s, SRR of 50%, and duration of 60 min. Additionally, reciprocating 60-min wear tests at 60 N-load, frequency of 15 Hz, stroke length of 4 mm and temperature of … were performed with IL-containing mixtures at 0.5 and 1 wt%. Coefficient of friction was recorded during the tests, and wear on the discs surface was measured using confocal microscopy. SEM and EDS were also used for studying the lubricant-surface interactions after these tests. Lubricants including [P6,6,6,14][(iC8)2PO2] exhibited better tribological performance than [P6,6,6,14][BEHP] ones and close to the ZDDP results. SEM images of worn surfaces exhibited evidence of plastic deformation and adhesive wear and EDS analysis showed that only active elements (P, S, Zn) were detected for mixtures containing ZDDP. XPS analysis indicated a different lubrication mechanism of the blends with ionic liquids compared with the ZDDP ones.

Two new ionic liquids ([N 6,6,6,6 ][C 8:0 ] and [N 6,6,6,6 ][C 16:0 ]) synthetized from fatty acids through a salt metathesis reaction were both characterized from a physicochemical and tribological point of view. Density, viscosity, corrosion activity and thermal stability tests were performed before making tribological tests under ball-on-disc both unidirectional (with fixed and variable slide-to-roll ratio) and reciprocating configuration. The main results of this work were the following: the longer the length of the alkyl chain of the anion the lower both viscosity and density and higher both viscosity index and thermal stability; these ionic liquids (ILs) are not corrosive; the [N 6,6,6,6 ][C 16:0 ] behaved better changing from elastohydrodynamic to mixed lubrication regime at lower speeds; their antiwear behavior at high load seems depend on their viscosity (for tests made at room temperature) and thermal stability and IL-surface interaction (for tests made at high temperature).

Thermal degradation of five phosphonium cation-based ionic liquids ([P 66614 outperforming the other ones in both pyrolytic and oxidising conditions. Although the thermal degradation mechanism is affected by atmospheric conditions, the degradation trend remains practically constant. As the dynamic methodology usually overestimates the long-term thermal stability, an isoconversional methodology is better for predicting the long-term thermal stability of these ionic liquids in order to be used as base oil or additive in lubricants formulation. Finally, the model-free methodology can predict at lower costs the ILs performance in isothermal conditions. Highlights• Weakly coordinating anions provoke good thermal stability of ILs.• • Isoconversional methods are better than dynamic ones for long-term thermal studies.• Activation energy behavior at low conversions is related to a single reaction.• Model-free methodology can predict the ILs performance in isothermal conditions.