Formation of Boundary Lubricating Films at Friction in Sunflower Oil with Addition of 1,3-Diketones

— The operation lifetime of friction units depends on properties of boundary layers, formed by lubricants. The highest adhesion to metal surfaces is demonstrated by boundary films formed during tribochemical reactions. The resulting high molecular products, known as friction polymers, protect the co...

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Veröffentlicht in:Journal of friction and wear 2021-07, Vol.42 (4), p.274-280
Hauptverfasser: Boiko, M. V., Sidashov, A. V., Boiko, T. G.
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Sprache:eng
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Zusammenfassung:— The operation lifetime of friction units depends on properties of boundary layers, formed by lubricants. The highest adhesion to metal surfaces is demonstrated by boundary films formed during tribochemical reactions. The resulting high molecular products, known as friction polymers, protect the contacting surfaces against wear. This study analyzes the influence of additives, the molecules of which are characterized by keto-enol tautomerism, on the processes of formation of boundary layers during friction in sunflower oil. It has been assumed that oil modification by additives, which are active in condensational reactions, will accelerate formation of friction polymers. Addition of up to 0.5 wt % of acetoacetic and malonic esters into sunflower oil accelerates formation of boundary layers, which is expressed in improvement of antifriction properties of oil. At higher concentrations of the additives the antifriction properties deteriorate. The obtained data are related with chemical interaction of additive molecules with metal. As a consequence, the surface oxide layer is eliminated. IR spectroscopy has detected chemical bonds between C–O–Fe exclusively in wear particles. With increase in the concentrations of additives in sunflower oil the weight of wear particles decreases after tribological tests. It has been demonstrated that formation of boundary lubricating films occurs upon interaction of molecules of sunflower oil with non-oxidized iron. Activity of added 1,3-diketones is determined by structural peculiarities of their molecules: existence of a mobile (acidic) hydrogen atom and groups of atoms capable of forming complex compounds with iron cations. The established regularities allow selecting the composition of lubricating medium in order to accelerate the formation of boundary lubricating layers closely connected with metal.
ISSN:1068-3666
1934-9386
DOI:10.3103/S1068366621040036