Effect of metal‐free phosphorus anti‐wear compounds on passenger car emissions and fuel economy

Devlin, Mark T.; Guevremont, Jeffrey M.; Sheets, Roger M.; Loper, J.D.; Guinther, Greg H.; Thompson, Karen; Jao, Tze‐Chi

doi:10.1002/ls.44

Cited by 10 publications

(7 citation statements)

References 23 publications

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“…6 Alkyl phosphates, such as tri(n-butyl)phosphate (TNBP), are already used as additives in gear lubricants and industrial lubricants. 7 Moreover, aryl phosphates, such as tri(m-cresyl) phosphate (TCP), are included in most aviation lubricant formulations. 8 Both TNBP and TCP have also been used as vapour phase lubricants (VPLs) for tribological systems that operate at very high temperature (> 700 K).…”

Section: Introductionmentioning

confidence: 99%

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Substituent Effects on the Thermal Decomposition of Phosphate Esters on Ferrous Surfaces

et al. 2020

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Phosphate esters have a wide range of industrial applications, for example in tribology where they are used as vapour phase lubricants and antiwear additives. An atomic-level understanding of phosphate ester tribofilm formation mechanisms is required to improve their tribological performance. A process of particular interest is the thermal decomposition of phosphate esters on steel surfaces, since this initiates polyphosphate film formation. In this study, reactive force field (ReaxFF) molecular dynamics (MD) simulations are used to study the thermal decomposition of phosphate esters with different substituents on several ferrous surfaces. The ReaxFF parameterisation was validated for a representative system using density functional theory (DFT) calculations. During the MD simulations on Fe3O4(001) and α-Fe(110), chemisorption interactions between the phosphate esters and the surfaces occur even at room temperature, and the number of molecule-surface bonds increases as the temperature increases from 300 to 1000 K. Conversely, on hydroxylated, amorphous Fe3O4, most of the molecules are physisorbed and some desorption occurs at high temperature. Thermal decomposition rates were much higher on Fe3O4(001) and particularly α-Fe(110) compared to hydroxylated, amorphous Fe3O4. This suggests that water passivates ferrous surfaces and inhibits phosphate ester chemisorption, decomposition, and ultimately polyphosphate film formation. For the alkyl phosphates, thermal decomposition proceeds mainly through CO and C-H cleavage on Fe3O4(001). Aryl phosphates show much higher thermal stability, and decomposition on Fe3O4(001) only occurs through P-O and C-H cleavage, which require very high temperature. The onset temperature for CO cleavage on Fe3O4(001) increases as: tertiary alkyl < secondary alkyl < primary linear alkyl ≈ primary branched alkyl < aryl. This order is consistent with experimental observations for the thermal stability of antiwear additives with similar substituents. The simulation results clarify a range of surface and substituent effects on the thermal decomposition of phosphate esters on steel that should be helpful for the design of new molecules with improved tribological performance.

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Section: Introductionmentioning

confidence: 99%

“…Some promising examples include phosphate esters and thiophosphate esters . Alkyl phosphates, such as tri- n -butyl phosphate (TNBP), are already used as additives in gear lubricants and industrial lubricants . Moreover, aryl phosphates, such as tri- m -cresyl phosphate (TCP), are included in most aviation lubricant formulations .…”

Section: Introductionmentioning

confidence: 99%

Substituent Effects on the Thermal Decomposition of Phosphate Esters on Ferrous Surfaces

et al. 2020

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“…The current issue and full text archive of this journal is available on Emerald Insight at: https://www.emerald.com/insight/0036-8792.htm content of ZDDP additives in lubricants, as well as a mixture of solutions based on ZDDP, have been investigated regarding their action to form protective films (Devlin et al, 2008;Spikes, 2008;Rastogi, et al, 2013). Neville and Morina studied the friction coefficient behaviour by replacing base oil (PAO6), ZDDP and molybdenum dialkyldithiocarbamate with a combination of these lubricants along a tribotest (Morina and Neville, 2007).…”

Section: Introductionmentioning

confidence: 99%

Effect of engine oil additives reduction on the tribofilm structure of a cylinder liner model surface

Miranda-Medina

Tomastik

Truglas

et al. 2019

ILT

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Purpose The purpose of this paper is to provide a general picture for describing the formed tribofilm, including chemical and physical aspects in the micro-scale and the nano-scale. In a previous study, the durability of zinc dialkyl dithiophosphate (ZDDP) tribofilms on cylinder liner samples has been investigated in a tribometer model system by using fresh and aged fully formulated oils and replacing them with PAO8 without additives. Analyses of the derived tribofilms by means of X-ray photoelectron spectroscopy and scanning electron microscopy could give some hints about the underlying mechanisms of the tribofilm build-up and wear performance, but a final model has not been achieved. Design/methodology/approach Thus, characterisation of these tribofilms by means of focused ion beam-transmission electron microscopy (FIB-TEM) and energy dispersive X-ray spectroscopy is presented and a concluding model of the underlying mechanisms of tribofilm build-up is discussed in this paper. Findings For tribotests running first with fresh fully formulated engine oil, a rather homogeneous ZDDP-like tribofilm is found underneath a carbon rich tribofilm after changing to non-additivated PAO8. However, when the tests run first with aged fully formulated engine oil, no ZDDP-like tribofilm has been found after changing to non-additivated PAO8, but a wear protective carbon rich tribofilm. Originality/value The obtained results provide insights into the structure and durability of tribofilms. Carbon-based tribofilms are built up on the basis of non-additivated PAO8 because of the previously present ZDDP tribofilms, which suggests an alternative way to reducing the consumption of antiwear additives.

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“…Recently, attempts to replace ZnDTP by other additives have been carried out from the viewpoint of restrictions on lubricant phosphorus and sulphur content in engine oils, caused by concern for exhaust catalyst poisoning. Devlin et al [15] examined alkyl phosphate (sulphur-free) type antiwear additive in catalyst emission and fuel economy tests, and found that the performance improved when alkyl phosphates were used in the place of ZnDTPs. Katafuchi and Shimizu [16] found that several synthesized compounds having an ester group near the sulphur atom in the molecule achieved an excellent antiwear performance, equivalent to ZnDTP.…”

Section: Introductionmentioning

confidence: 99%

Boundary lubrication film formation from phosphorus antiwear additives with application to metal V-belt type continuously variable transmission lubricants

Narita

Priest

2008

Proceedings of the Institution of Mechanical Engineers, Part J:

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This study has focused on the application of sulphur-free phosphorus antiwear additives in metal V-belt pushing type continuously variable transmission fluids to achieve higher friction coefficient plus excellent antiwear performance between the metal -metal contacting surfaces. The metal -metal tribological characteristics of phosphorus compounds were experimentally investigated using a reciprocating ball on plate tribometer, enabling film formation to be monitored during reciprocating sliding tests by an electric resistance method. As a result, sample with acid phosphate possessing C8 alkyl chain gave 20 per cent higher friction coefficient between metal contacting interfaces than C18 alkyl acid phosphate. Notably, an additive formulation composed of C8 acid phosphate with shorter alkyl chain, amine compound, and over-based calcium sulphonate demonstrated a synergism with 9 per cent higher friction and better antiwear performance than acid phosphate alone, which would give a positive outcome in the belt and pulley system of the continuously variable transmission. From surface analysis such as optical interferometry and X-ray photoelectron spectroscopy, it is hypothesized that the variation of tribofilm species produced by a chemical reaction between these additives plays a role in reducing corrosive wear and inhibiting the entrainment of lubricant into interfaces, resulting in higher friction. Moreover, the post-test rubbing tracks still possessed a longitudinally oriented surface pattern, which seemed to contribute to a reduced fluid film effect, giving a higher friction coefficient during rubbing tests.

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Effect of metal‐free phosphorus anti‐wear compounds on passenger car emissions and fuel economy

Cited by 10 publications

References 23 publications

Substituent Effects on the Thermal Decomposition of Phosphate Esters on Ferrous Surfaces

Substituent Effects on the Thermal Decomposition of Phosphate Esters on Ferrous Surfaces

Effect of engine oil additives reduction on the tribofilm structure of a cylinder liner model surface

Boundary lubrication film formation from phosphorus antiwear additives with application to metal V-belt type continuously variable transmission lubricants

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