In this work, the possibility of using esters of organic acids as antiwear additives to lubricants has been investigated. Work has two targets. The first of these is the verification of theoretical statements about the mechanism of action of anti-wear additives. According to the authors ideas, the influence of additives on the formation and properties of a polymolecular adsorption layer is the predominant factor. These ideas are based on the general laws of liquids adsorption on the solid surface. In addition, they correspond to the properties of AW/EP additives used in modern lubricants. The second goal is to develop justified approaches to creating AW/EP additives for biodegradable lubricants based on vegetable oils and synthetic esters. Additives to these materials must meet several requirements. In particular, they must be chemically compatible with vegetable oils and not have bactericidal properties. For use in twostroke internal combustion engines, additives must contain a minimum amount of sulfur, phosphorus and ash elements. Esters of dibasic and tribasic organic acids with higher alcohols were chosen as promising objects of study. Studies have been conducted on the example of the monoester of maleic acid, esters of tartaric and aconitic acids with hexadecyl alcohol. The results of measurements of the anti-wear properties of these substances when added to vegetable oil are given. As a result of these tests, a high AW/EP effectiveness of aconitic ester was found. This compound also showed efficacy when it was added to petroleum oil without additives and to standard gear oil. The measurements were simultaneously carried out in the SUSU laboratories, and at Sofia University in several stands under various friction conditions. The results showed that the use of new additives in hydrocarbon petroleum oil without additives gives AW effect, which is slightly lower than ZDDP. The investigated additive can be used in standard compositions of additives to motor and transmission oils. The results of the study indicate the prospects for the use of esters of polyatomic acids as AW/EP additives for lubricants of various origins.
The article presents the results of a study of metal oleates for friction with mixed and boundary lubrication. The objects of study are copper (II), zinc (II), and tin (II) oleates. The boundary friction coefficient in a "steel -steel" friction pair was measured at an II5018 testing machine according to the "roller-block" scheme at different temperatures. The friction coefficient for mixed lubrication was measured in a plain bearing during the transition between hydrodynamic and boundary lubrication. Hersey-Stribeck curves were constructed for the journal bearing. The investigated additives have the most significant effect on the friction coefficient when introduced into the oil without other additives and less significant effect when introduced into the engine oil. The investigated metal oleates affect the conditions for the transition between hydrodynamic and boundary lubrication in a journal bearing. The results show that copper oleate reduces the contact friction coefficient by 7-15 % when added to engine oil. Zinc oleate has a similar effect and reduces the friction coefficient by 5.5-8.5 %. Tin oleate reduces the friction coefficient by 23.5-31 %.
The purpose of this study is to determine the effect of metal ion on the tribological characteristics of metal oleates similar to copper (II) oleate which is the basis of well-known additives such as Valena, Servovit etc. The objects of study are copper (II), zinc (II) and tin (II) oleates. Salts of these metals are selected to clarify the role of such parameters of metal ion, as the active metal and the radius of the ion. Lubricant compositions were prepared with each additive sample. The mass concentration of the additive was 1% in synthetic motor oil of viscosity class SAE 5W-40 (API SN/CF) and in industrial oil I40A. The influence of metal oleates on the friction coefficient of the friction pair of steel 45-steel 10 was investigated. The friction coefficient was measured on the machine friction II5018 according to the scheme "roller-pad" at different temperatures. The investigated additives have the most significant effect on the coefficient of friction when introduced into the oil without additives and less significantly when introduced into the engine oil. The results show that copper oleate reduces the coefficient of friction in contact by 7% -15% when added to the engine oil. Zinc oleate leads to a similar effect and reduces the coefficient of friction by 5.5% -8.5%. Oleate of tin leads to a decrease in the friction coefficient of 23.5%-31%.
Increasing of the environmental requirements to transport and industry poses to tribology a priority task related to the development of environmentally friendly lubricants and technologies. Vegetable oils and synthetic esters are most commonly used as biodegradable base oils. The fundamental constraints associated with their direct application are related to two parameters: stability towards oxidation and their contact characteristics, antifriction, wear and tear resistance. To increase oxidation stability, low unsaturated fatty acids contents are used, and the reduction of friction and wear is achieved by developing compatible composite additives towards the base vegetable oil. The present study presents results from a comparative investigation of friction characteristics and oil temperature in two tribosystems "Rolling Bearings" and "Sliding Bearing" when lubricated with pure rapeseed oil and rapeseed oil containing 4% non-toxic and ashless additive . The new additive is designed for biodegradable base oils. The research was conducted in tribology laboratories in Southern
The possibility of using substances containing only carbon, hydrogen and oxygen as antiwear additives for lubricating oils has been investigated. Studies have been conducted on the example of ethers of aconite acid and hexadecyl alcohol. This compound was chosen as a promising AW/EP additive for biodegradable greases based on vegetable oils. In addition, the anti-wear mechanism of substances that do not contain phosphorus, sulfur, chlorine, metals and other heteroatoms is very interesting. Aconite acid hexadecyl ester was added to rapeseed oil, to petroleum oil without additives, and to standard gear oil. Antiwear properties of the obtained compounds were identified and presented as results. Measurements were carried out both in laboratories of SUSU and at Sofia University at several stands under various friction conditions. It was established that the test additive exhibits anti-wear properties in all three lubricating oils. With the introduction of additives in rapeseed oil, wear is reduced by 25 ... 50% depending on the test conditions. The wear reduction is more significant in steel-bronze contacts than in steel-steel and steel-iron contacts. With the introduction of additives in hydrocarbon oil without additives, anti-wear effect is only slightly lower than with the introduction of ZDDP. Anti-wear effect increases with increasing load (contact pressure), as well as for ZDDP. The most pronounced effect for both vegetable and petroleum oil, obtained by testing the method of four balls according to the technique of ASTM D 4172. When hexadecyl aconite acid is added to gear oil (GL-5 standard) containing ZDDP and EP additives, wear is reduced to the same extent as when it is added to oil without additives. The welding load increases slightly. This suggests that the studied additive does not compete with ZDDP and can be used in mixed composition. The absence of heteroatoms in the studied additive indicates an adsorption mechanism of anti-wear action. The study results indicate the prospects for the use of esters of polyatomic acids as AW/EP additives for biodegradable lubricating oils and oils for food production equipment.
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