Mechanisms of oiliness additives

Ratoi, Monica; Anghel, Veronica; Bovington, C. H.; Spikes, H. A.

doi:10.1016/s0301-679x(00)00037-2

Cited by 99 publications

(60 citation statements)

References 10 publications

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“…The liquid cell can be heated and this showed reversible loss of the adsorbed islands above about 40°C. The technique of ultrathin film interferometry can study boundary films in actual rubbing contacts and this confirmed that stearic, oleic and isostearic acid solutions form 2 nm thick films in dry conditions [67] [83]. However exposure to water vapour for an extended period resulted in stearic acid forming a significantly thicker film ( Fig.…”

Section: Ofm Research 1990s To Presentsupporting

confidence: 54%

“…These include the surface forces apparatus (SFA) [58][59][60][61], atomic/lateral force microscope (AFM/LFM) [62][63][64][65], quartz crystal microbalance (QCM) [66], ultrathin film interferometry (UTFI) [67], neutron reflectometry [68,69] and various surface-specific vibrational spectroscopies [70][71][72]. Methods were also developed to generate model close-packed monolayers by chemical grafting of self-assembled alkylthiols and alkyl siloxanes on solid surfaces [73][74].…”

Section: Ofm Research 1990s To Presentmentioning

confidence: 99%

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Friction Modifier Additives

2015

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The need for energy efficiency is leading to the growing use of additives that reduce friction in thin film boundary and mixed lubrication conditions. Several classes of such friction modifier additive exist, the main ones being organic friction modifiers, functionalised polymers, soluble organo-molybdenum additives and dispersed nanoparticles. All work in different ways. This paper reviews these four main types of lubricant friction modifier additive and outlines their history, research and the mechanisms by which they are currently believed to function. Aspects of their behaviour that are still not yet fully understood are highlighted.

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Section: Ofm Research 1990s To Presentsupporting

confidence: 54%

Section: Ofm Research 1990s To Presentmentioning

confidence: 99%

Friction Modifier Additives

2015

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“…It is believed that mechanical rubbing associated with the initial rolling contact under no boundary film provides situations needed to initiate some chemical reactions of fatty acid molecules with the metal surface, leading to a monolayer film adsorbed strongly on the surface [5,19]. Similar experiments with no rolling contact periods confirmed that the stationary contact alone is insufficient to initiate boundary film formation.…”

Section: Discussionmentioning

confidence: 78%

“…In the presence of water, thick boundary films were formed, suggesting that the friction modifiers react chemically with the surfaces to produce insoluble iron carboxylate, which generates thick boundary films (e.g., 10-20 nm thick) [19]. The ultrathin-film interferometry has also been used to monitor the survival of multilayer Langmuir-Blodgett (LB) films of stearic acid in rolling contacts [20].…”

Section: Introductionmentioning

confidence: 99%

Process of Boundary Film Formation from Fatty Acid Solution

Nakano

Spikes

2012

Tribology Online

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Ultrathin-film interferometry was used to investigate the developing process of boundary films in a steel-on-silica contact lubricated by a solution of n-hexadecanoic acid dissolved in n-hexadecane. Immersion of the surfaces in the solution is not sufficient to initiate boundary film formation. However, upon a nominally pure rolling contact, boundary film formation is initiated, and, once initiated, the boundary film develops spontaneously. It is believed that the initial monolayer film adsorbed strongly on the solid surface induces subsequent molecular stacking from the solution. The developed boundary film can be partially destroyed by the rolling contact, although the nominally identical rolling contact acts as the trigger of boundary film formation. These findings reveal that the immobile boundary films to reduce friction of solids under high pressure result from the equilibrium of two competing processes: spontaneous development by molecular stacking and mechanical destruction by relative motion of the contact surfaces.

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“…Several such techniques do exist. Ultrathin film interferometry has shown that some OFMs can form quite thick films in water-contaminated or elevated temperature conditions [14] [15]. Unfortunately this method operates in quite gentle contact conditions, with negligible solidsolid contact so as to preclude damage to the optical coatings on the transparent surface.…”

Section: Introductionmentioning

confidence: 99%

In Situ Study of Model Organic Friction Modifiers Using Liquid Cell AFM: Self-Assembly of Octadecylamine

et al. 2015

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Liquid cell AFM has been applied to study in situ the formation and properties of selfassembled films formed on mica surfaces by octadecylamine from alkane solution.Mica surfaces immersed in hexadecane or dodecane at room temperature show no identifiable surface films. However when octadecylamine solution is injected into the cell a boundary film forms almost immediately. This film takes the form of irregular islands of mean diameter approximately 1 to 3 µm and thickness typically 1.5 nm when measured in contact mode. These islands are believed to correspond to patches of vertically-oriented but tilted octadecylamine or ammonium salt held together primarily by van der Waals forces between adjacent alkyl chains. These films are quite labile in that during scanning of the tip in both tapping and in contact mode changes to the shape of the islands takes place, including consolidation of the island density in the scanned region and depletion from around this area.In situ experiments in which the temperature of the cell is varied over time show that the initially-formed islands disappear at a temperature of ca. 35ºC but are reformed when the cell is re-cooled. Similar tests on samples that remain immersed in solution for extended periods show more stable films, with islands being lost only above about 50-60ºC.The work shows that liquid cell AFM has great promise for studying the formation and properties of the boundary films formed by organic friction modifiers.

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Mechanisms of oiliness additives

Cited by 99 publications

References 10 publications

Friction Modifier Additives

Friction Modifier Additives

Process of Boundary Film Formation from Fatty Acid Solution

In Situ Study of Model Organic Friction Modifiers Using Liquid Cell AFM: Self-Assembly of Octadecylamine

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