Alkyl-Cyclens as Effective Sulfur- and Phosphorus-Free Friction Modifiers for Boundary Lubrication

Abstract

Modern automotive engines operate at higher power densities than ever before, driving a need for new lubricant additives capable of reducing friction and wear further than ever before while not poisoning the catalytic converter. Reported in this paper is a new class of molecular friction modifier (FM), represented by 1,4,7,10-tetradodecyl-1,4,7,10-tetraazacyclododecane (1a), designed to employ thermally stable, sulfur- and phosphorus-free alkyl-substituted nitrogen heterocycles with multiple nitrogen centers per molecule. The multiple nitrogen centers enable cooperative binding to a surface which provides strong surface adsorption and lubricant film durability in the boundary lubrication (BL) regime. A 1 wt % loading of the cyclen FM 1a in Group III base oil exhibits strong surface adsorption, leading to excellent reductions in friction (70%) and wear (95%) versus the pure Group III oil across a wide temperature range. The lubricant with the new FM additive also outperforms two commercially available noncyclic amine-based FMs and a fully formulated commercial 5W30 motor oil.

Experimental study of application of molecules with a cyclic head group containing a free radical as organic friction modifiers

“…With E p = E d = 200 GPa, υ p = υ d = 0.29, α = 13.5 GPa -1 (Biresaw and Bantchev, 2013), viscosities of individual lubricants listed in Table 1, and the normal loads and sliding speeds described above, g E and g v were calculated to be in the range of 4.4×10 6 -4.2×10 11 and 8.8×10 7 -2.8×10 13 , respectively. These values correspond to the PE regime based on literature (Esfahanian and Hamrock, 1991) and hence, the following equation for the minimum film thickness in the PE regime was used (Desanker et al, 2017;Hamrock and Dowson, 1976a, 1976b, 1977Li et al, 2017;Liu et al, 2017;Spikes, 2006;Yamamoto and Kaneta, 2010). 8where k is a contact ellipticity parameter (equal to 1 in this study).…”

“…From the environmental perspective, organic friction modifiers (OFMs) that are sulfur and phosphorus-free and contain only carbon, hydrogen, oxygen, and nitrogen atoms are desirable to reduce hazardous emissions (Erdemir, 2005). The effectiveness of OFMs in reducing friction largely depends on their ability to become adsorbed from the lubricant solution on the solid surfaces and form a boundary film separating the opposing solid surfaces (Spikes, 2015;Desanker et al, 2017). Thus, the most typical molecular structure of an OFM consists of a hydrocarbon chain (tail group) and functional head group, such as carboxyl, amide, and glyceryl groups, at one end of the chain (Kenbeek et al, 2000).…”

“…Inheriting the feature of the molecular structure of fatty acids, which were the first OFM successfully used in 1918 (Spikes, 2015), the OFMs used thus far are basically slim molecules with small head groups. To explore the possibility of further performance improvement, a new type of OFM that features a large head group comprising of a nitrogen heterocycle with four nitrogen centers has been developed recently, and experimental results have demonstrated its excellent performance in reducing the friction and wear in the boundary lubrication regime (Desanker et al, 2017). This indicates that the effects of the head groups, including their size and shape, on the performance of OFMs are yet to be completely elucidated, and there is still a possibility to further optimize their design.…”

Sulfur-Doped Alkylated Graphene Oxide as High-Performance Lubricant Additive

“…Since the excessive active sulfur in organic compounds could poison the ternary catalyst of emission reduction system while serving on the piston ring and cylinder wall, which has been resulting to serious environment pollution, the coming mandatory standard from the International Lubricant Standardization and Approval Committee (ILSAC) [3] requires the sulfur content of lubrication oil should be less than 0.5 wt%, for the reason that the higher sulfur content in lubricant could deteriorate the quality of engine exhaust gas [4]. In order to resolve the problem, many strategies including the organic friction modifier such as sulfur-free alkyl-cyclens [5], quinolinium salts [6], and nanomaterial anti-wear additives like BN co-doped graphene [7], SiC@graphene [8], crumpled graphene [9], and graphene nanoscroll [10] have been developing to reduce or remove the sulfur content of lubrication oils. However, the above developing methods still need a long time to verify the practical lubrication effect, environment factor, safety, and other aspects to finally confirm the actual application results.…”

Tetrahydropyrazolopyridines as antifriction and antiwear agents: experimental and DFT calculations

“…Desanker et al have tested the performance of alkyl-substituted cyclen derivative (commercial Group III lubricating oil) as friction modier using pin-on-disk tribometry tests. 27 Several ionic liquids such as di[bis(2-hydroxyethyl)ammonium]succinate, 28 1-acetyl-3-hexylbenzotriazolium benzoate/ sorbate, 29 poly-alkylimidazoliumbis(triuoromethylsulfonyl) imide, 30 alkylimidazolium diethyl phosphates, 31 bis(imidazolium)/bis(ammonium)-di[bis(salicylato)borate] 32 are reported as effective antiwear agents. Quinoline derivatives 33 in polyethylene glycol (PEG) and Schiff bases of 4-aminoantipyrene with substituted benzaldehyde 34 in paraffin oil have been reported as excellent tribological additives from our laboratory.…”