Tribological properties of oligomeric additives based on oligo-oxypropylene diamines

The findings of studies of the antifrictional, antiwear, and antiscoring properties of oligomeric additives based on oligooxypropylene diamide acids soluble in rapeseed oil are presented. It is established that each of the low-molecular oligomers in question improves considerably one of the three above tribological properties. The high-molecular oligomeric additive improves concurrently the antifrictional, antiwear, and antiscoring properties of rapeseed oil, allowing it to be recommended for use as a polyfunctional additive to technological greases based on vegetable oils for protecting metals against wear.     

Adsorption of heteropolyphosphates of alkaline metals on iron surface

The physical and chemical properties of heteropolyphosphates of alkaline metals are studied as promising antiwear and antiscoring additives to plastic lubricating materials. Quantum-chemical analysis of the interaction of the heteropolyphosphates with iron surfaces provides insight into the processes that evolve in these compounds during friction. The mechanism of opening of the heteropolyphosphatic cycles and their transition into linear structures is studied.     

Investigation of the triboengineering characteristics of plastic railway greases with inorganic polymeric additives

It is proposed to use certain inorganic polymeric phosphates as antiwear and antiscoring additives in plastic greases in heavily loaded units of railway rolling stock. Introduction of sodium molybdophosphate into the plastic greases Buksol and GRO-M considerably reduces the friction coefficient of the steel-steel friction pair and keeps it stable over time. The molecular mechanism of the effect of the additives is considered.     

Zinc Dialkyldithiophosphate Additive Adsorption on Carbon Black Particles

Soot is known to cause high wear in engine components and this is a problem with engine oils between extended drain intervals. Although several wear mechanisms have been suggested, exact soot-induced wear mechanisms are still not fully understood. This study aims to investigate the additive adsorption mechanism (specifically anti-wear additive) on carbon black (CB) particles (as a soot surrogate). This mechanism is one of the main mechanisms responsible for high wear. Base oil (BO) was used to exclude the effect of other additives that are present in fully formulated oil. Zinc dialkyldithiophosphate (ZDDP) anti-wear additive was added to the BO and then the mixture, which will be referred to as the model oil, was aged with CB particles. The resulting oils were then chemically characterised by using ICP and FTIR analysis techniques. Finally, the CB particles were filtered out and analysed using EDX. The results showed that both zinc and phosphorous which are chemical elements from ZDDP anti-wear additive were adsorbed on CB particles in the oil phase. This additive adsorption mechanism can lead to increased wear in the engine components due to lack of additives in the oil. This study highlights the importance of understanding the additive adsorption on soot particles since this mechanism will reduce the engine oil life and increase frequency of oil changes.     

Study of additive‐additive interactions in a lubricant system by NMR,ESCA, and thermal techniques

Engine oil lubricants are formulated with a variety of additive components at different dosages to obtain the desired physico‐chemical characteristics. Antiwear, friction modification/energy efficiency, dispersancy, and detergency properties are normally achieved by the use of zinc dialkyldithiophosphate (ZDDP), molybdenum dithiocarbamate (MoDTC) and ashless alkyl phosphorodithioate, polyisobutylene succinimide (PIBS), and metal sulphonates / phenates, respectively. It has been reported that these additives interact with each other and affect the overall performance of a lubricant system. The additive‐additive interactions have been studied by nuclear magnetic resonance (NMR) and infrared spectroscopic techniques, where attention has been mainly focused on the ZDDP‐PIBS additive system in the presence or absence of other additives. The results have been used to relate the synergistic or antagonistic effects of such interactions to the overall performance of a lubricant. Recently, MoDTC has found wider application in lubricants as a friction modifier and energy‐efficient additive. However, no studies of the additive‐additive interactions of the PIBS‐MoDTC‐ZDDP additive system using analytical techniques have been reported. The present paper covers the fundamental and mechanistic aspects of additive‐additive interactions of ZDDP, MoDTC, PIBS, and sulphonate / phenate additives present in a lubricant system as studied by ³¹P NMR, electron spectroscopy for chemical analysis (ESCA), and thermogravimetric analysis (TGA) techniques. ESCA, which is a surface analytical technique, has been used to provide basic evidence for the formation of various complexes through interactions occurring in the electronic binding energies of orbitals of various atoms of the additives. The ESCA studies have also revealed the actual atomic sites of interaction between the additives responsible for the formation of adducts or complexes. The differential scanning calorimetry profiles of blends have verified the interactions among the additives and shown that the stability of the additive system is quite different from that of the additives alone. The shifts in the ³¹P NMR signals, the changes in the binding energies of the s, p, and d orbitals of additive elements, and the multistage decomposition profiles in the TGA thermograms of interacting systems due to complexion and adduct formation have enabled a mechanism of interaction to be proposed.     

The tribological behaviour and mechanism of action of sulphur-containing borate esters in rape seed oil

Three sulphur-containing borate esters and one borate ester based on boric acid and n-octanol were synthesised. The antiwear and friction-reducing properties of these synthetic compounds as additives in rape seed oil were examined using a four-ball machine. The relationship between the additive structure and tribological properties was explored, and the lubrication mechanisms of the additives investigated. The worn surfaces of a steel ball lubricated with the additive-containing rape seed oil were analysed using X-ray photoelectron spectroscopy and scanning electron microscopy. The elemental compositions of, and distributions in, the worn steel surfaces were determined with an electron probe micro-analyser. It was found that sulphur-containing borate esters as additives in rape seed oil at appropriate concentrations can be effective in improving antiwear and friction-reducing behaviour. The rape seed oil base stock experiences competitive adsorption and tribochemical reactions with additives on the rubbing steel surface. The introduction of the active element sulphur into the borate ester additives functions to improve the tribological behaviour of the base stock by increasing the rate of formation of a protective layer on the rubbing steel surface. However, the tribological behaviour of the additives is not dependent on the number of sulphur atoms in the additive molecules, and further work is needed to investigate the possible dependence of this behaviour on the ratio of boron to sulphur in the additive molecules.     

Additive interaction and lubrication performance in a polar additive binary system

Additive interactions were studied between polar compounds, one of which decomposes at the frictional surface, on the lubrication performance of a binary system for polar straight chain hydrocarbons and aromatic compounds.As a comparison, an additive single component system was also studied. The lubricant performance of the blended oils was evaluated using a Falex lubricant testing machine and the adsorption characteristics of the additives on an iron surface were analysed.In the single component system, good correlation was obtained between the adsorption isotherm and the anti-seizure characteristics of the additives for both 1-octadecanol and 2-naphthol. In the binary system of 2-naphthol and 1-octadecanol, the lubrication characteristics of 2-naphthol appeared, producing heavy decomposition products of 2-naphthol because 2-naphthol was irreversibly (or chemically) adsorbed while 1-octadecanol was reversibly (or physically) adsorbed.Conversely, in the binary system of β-naphthol and stearic acid, the lubrication performance was poorer than that of the individual additive, since neither the decomposition products of the aromatics nor the adsorption film of stearic acid was sufficient against seizure. This was owing to the comparable adsorbability of the two compounds.     

N-酰基苯丙氨酸的合成及其在水基中润滑和防锈性能研究

将脂肪酸酰氯和苯丙氨酸在碱性溶液中反应得到的N-酰基苯丙氨酸，用红外光谱对其结构进行表征；用四球摩擦磨损试验机考察了N-酰基苯丙氨酸以三乙醇胺为助溶剂时在水溶液中的摩擦磨损性能，并用俄歇电子能谱研究了磨斑表面边界膜的化学组成和元素分布。结果表明：N-酰基苯丙氨酸的水溶液表现出很好的抗磨和减摩特性，这可能是N-酰基苯丙氨酸三乙醇胺盐中的极性基团吸附在钢球的表面，长碳链疏水性的烃基在金属表面形成较厚的保护膜，在较高载荷运行下，发生化学反应形成高强度的摩擦化学反应膜；N-酰基苯丙氨酸三乙醇胺盐还有较好的防锈性。经细菌试验表明其具有较好的抗菌能力。     

Tribochemistry and the development of AW and EP oil additives — a review

The antiwear (AW) and extreme pressure (EP) properties of chlorine, sulphur, phosphorus-containing organic compounds and zinc dialkyldithiophosphate (ZDDP) oil additives are affected greatly by their reactive ability to the metal surface, as well as by the chemical composition, chemical state, physical and mechanical properties of the protective films formed. Over four decades, research has taken place on boundary lubrication, and a much better understanding of the AW and EP action mechanism of one additive by itself in base oil has been obtained, and much more knowledge on the relationship between wear and decomposition of additives, adsorption and reaction of the additive or its decomposed products with metal, has been gained. A series of analytical methods and a great number of modern surface analytical tools have been set up and used for research in this area. The problems and some suggestions for the future study on boundary lubrication of oil additive are proposed.     

The mechanism of iron phosphide formation during boundary friction in the presence of organic phosphates and phosphites

Thermochemical and mechanochemical reactions of tricresyl phosphate, tributyl phosphate, and tributyl phosphite with an iron surface are studied. A possible mechanism of iron phosphide formation under severe boundary friction conditions is proposed. The antiscoring behavior of phosphine in a vaseline oil solution is studied for the first time. It is found that (a) iron powders modified by tricresyl phosphate or tributyl phosphite do not yield iron phosphide at a temperature of 710°C in vacuum but are reduced to iron phosphide by birch coal; (b) at a temperature of 760°C in a flow reactor, tricresyl phosphate produces a much greater amount of solid phosphorous-containing residue than tributyl phosphite; (c) at a temperature of 760°C in a flow reactor, tributyl phosphite produces white phosphorus; (d) phosphine improves effectively the antiscoring properties of vaseline oil.     

Mechanisms of oiliness additives

Ultrathin film interferometry has been used to measure the boundary film-forming behaviour of long chain, carboxylic acid oiliness additives. It has been shown that in dry conditions, these acids form very thin films of around 2–3 nm thickness. However when water is present, some acids form significantly thicker films, around 10 nm in thickness. The behaviour of these films is very similar to that previously seen with metal carboxylate additive films, including thick film collapse at high rolling speeds followed by film reformation at slow speeds. It is suggested thick films formed by long chain carboxylic acid additives result from reaction of the acids at the rolling solid surfaces in the presence of water to form deposits of insoluble iron carboxylate.     

Action mechanisms of boundary lubrication additives — A review,Part I

A wide range of literature has been published in the period 1950–2000 concerning emerging concepts relating to the action mechanisms of boundary lubrication additives. Some of the details of these additives in terms of chemical nature, surface adsorption, surface film generation, thermal stability, thermodynamics of contact surfaces, and rise in surface temperature, as reported in this literature, are reviewed in the present paper. It has been observed that the chemical constituents of boundary lubrication additives, particularly of organosulphur and organosulphur—phosphorus origin, are very complex in nature and no comprehensive details are readily available. Regarding action mechanisms, different researchers have suggested different mechanisms for different conditions. However, information on the thermodynamics of surfaces and thermal stability of additives is not readily available. Other details, such as the effect of sliding speed, operating load, surface roughness, and material design, are not covered in this paper. Overall, the literature reveals that attempts to correlate additive characteristics with boundary lubrication activity have met with limited success, and efforts aimed at achieving ever‐increasing performance levels are continuing. In this first part, the authors examine the chemical nature of boundary lubrication additives, the surface films produced, and surface temperature.     

无机盐对水溶性稀土络合物添加剂性能的影响

本文简述了水溶性极压抗磨添加剂存在的问题，合成了水溶性十二烷基聚氧乙烯醚磷酸酯稀土络合物，考察了该类络合物添加剂在水中的极压抗生，提出一套衡量与比较添加剂抗磨和极压性能优劣的参数，并且针对实际应用中水质的不同，研究了阴阳离子对其在水中的摩擦学性能的影响。     

环境友好水基全合成金属加工切削液的研究

通过对各种环境友好添加剂筛选,选用异构脂肪酸醇胺盐和月桂酸正醇酯作为润滑添加剂,选用能对切削液泡沫有抑制作用的不同种类的聚醚(有效控制EO与PO比例的镶嵌聚醚)作为表面活性剂,选用硼酸醇胺盐作为极压抗磨添加剂和防锈剂,研制出环境友好水基全合成切削液,在不加杀菌剂的情况下,切削液的使用寿命达到一年以上。产品各项性能指标与国外同类高档产品相当,达到了环保、节能、降耗的效果。     

Investigation of Oil Additives for Boundary Lubrication of Railroad Journal Bearings

The boundary friction properties of the lubricated system of steel sliding on lead-base babbitt were investigated as a phase of the Association of American Railroads' sponsored project on freight car hot boxes. A friction pendulum was developed for determining the coefficients of boundary friction as a function of temperature with the specified metals lubricated with various lube oil additive blends.

A group of general relationships dealing with additives for the steel-babbitt system was developed. It is concluded that the extreme pressure agents containing sulfur or chlorine are generally unsuited for railroad journal bearing use. Lubricity additives which function by simple physical adsorption were found to be ineffective at moderate or high temperatures existing in railroad operations. Those lubricity additives which chemisorb to metal surfaces and form a close-packed layer were found to be effective antifriction agents.     

An Adsorption Model for Friction in Boundary Lubrication

A model describing the relationship between friction coefficient and surface adsorption of a two-component lubricant (i.e. base lubricant and one additive) is developed for boundary lubrication. This model relates the coefficient of friction to the extent of metal-metal contact or, inversely, the fractional surface coverage of the lubricant. Using a suitable adsorption isotherm, an expression for friction coefficient is obtained, relating the friction coefficient to the additive concentration and the adsorption energy. The proposed model and the selected adsorption isotherm are experimentally verified by testing several model additives in a petroleum-base lubricant. An excellent correlation is obtained between the adsorption-free energies calculated from the friction coefficient data and the adsorption-free energies determined from adsorption studies. The ranking order of additives based on friction coefficient is explained in terms of the molecular structure and the structural effects on the adsorption-free energy.     

Anti‐friction,anti‐wear and load‐carrying characteristics of environment friendly additive formulation

The extreme pressure (EP), anti‐wear and friction‐reducing characteristics of some of the commercial additive formulation and individual components on which these formulations are based have been studied and compared to characteristics of the components synthesised from naturally available non‐traditional vegetable oils and cashew nut shell liquid that have been refined and partially hydrogenated to improve stability. It has been shown that individual components from sulphurised and phosphosulphurised vegetable oils, esters and hydrogenated cardanol (derived from cashews) have better anti‐wear and friction‐reducing characteristics than the sulphurised olefins and alkylaryl phosphorothioates normally used as EP and anti‐wear additives, while the load‐carrying characteristics of a number of the combination of these derivatives are comparable. It has been shown that all these formulations are rapidly biodegradable and non‐toxic in nature as compared to traditional EP, anti‐wear and friction‐reducing additives, which fill in the category of slightly toxic to harmful. It is possible to formulate energy‐efficient EP gear oils that are fully biodegradable and non‐toxic by a combination of vegetable oil‐based additives of sulphurised vegetable oils, phosphosulphurised methyl recinoleate and phosphosulphurised hydrogenated cardanol amine borate, which meet all the performance characteristics of US steel 224 eg 52100, M‐50 AISI 1010 requirements. Copyright © 2007 John Wiley & Sons, Ltd.     

Sulphur-phosphous components in gear oils: part 1, oxidation stability studies by P-NMR spectroscopic techniques

In the present investigations, the mechanism of oxidation stability of sulphur and phosphorus-based additives such as S-alkyl O,O-dialkyl phosphorodithioate, alkyl amine salt of dialkyl dithiophosphoric acid, dialkyl hydrogen phosphite and zinc dialkyl dithiophosphate used in lubricants has been studied by liquid and solid state ³¹P/^lH-NMR spectroscopic techniques. These techniques have enabled to monitor the complex changes that occur during oxidation at different intervals during long duration oxidation tests and provide qualitative and quantitative information of products formed during degradation of S–P based additives. The nature of both soluble and insoluble products of decomposition has been /determined. The studies have revealed few important aspects regarding thermal stability of these additives. The ashless S-alkyl O,O-dialkyl phosphorodithioate have better thermal oxidative stability and retain their identity for longer period compared to other similar ashless additives and zinc dialkyl dithiophosphates. The loss of additives during oxidation is 12% in case of S-alkyl O,O-dialkyl phosphorodithioate compared to other mentioned additives (40–100%) during 64 h of heating at 165 °C in the presence of air and catalyst. The decomposed products are also solublised in case of S-alkyl O,O - dialkyl phosphorodithioate and dialkyl hydrogen phosphite, and small amount of solids are formed compared to other additives. During oxidation the main components are being converted into more complex insoluble polyphosphates. The nature of soluble and insoluble products of decomposition as a result of thermal degradation are similar irrespective of the types of additive used. The mechanism of degradation and subsequent composition and structure of products formed has been discussed in detail. These studies will facilitate correlation of the structure and performance of these additives in lubricants.     

The study and application of an anti-adhesive wear lubricant for use in deep drawing

This paper reports on an anti-adhesive wear lubricant (NL2) used in deep drawing, containing as additives B, N compounds and zinc (cyclic) polymethylenedithiophosphate. It covers the synthesis of these additives, their properties, and the friction and wear mechanism of NL2 in the deep-drawing process. These are studied by means of a strip bending drawing tester, a four-ball tester, and IR, SEM, and EDAX analysis. The results show that the new additive gives good adhesive wear protection in deep drawing.     

Role of Additive Adsorption in the Mitigation of Wear

The mathematical model of adhesive wear and its control by surface adsorption of a single-component lubricant has been expanded to include an additive as a second component. The model has been tested with experimental wear rate results as a function if additive concentration for both liquid and vapor phase lubricants. A satisfactory fit of the data to the model is observed, and the calculated values for the equilibrium constant and the heat of adsorption for long-chain polar compounds from cetane solution on steel surfaces are amine > acid > alcohol, the same trend as observed in adsorption studies. The ratio of the effective molecular size of the adsorbed molecules can be calculated and used as a parameter in testing the model, or for gaining understanding about the nature of the active antiwear specie.