Lubricants antiwear property

Zinc soaps, which are complexes of long chain fatty acids, find similar applications in the curing and hardening of coatings to other transition metal soaps. A summary is available.123 The more important anions are 2-ethylhexanoate, naphthenate and stearate. Mixtures of zinc and calcium soaps are also effective stabilizers for poly(vinyl chloride).124 The complexes [Zn 0P(0)-(OBun)2 2] and [Zn SP(S)(OBun)2 2] both promote antiwear properties of lubricating oils.125... 

The prediction of antiwear benefits and optimization of the ZDDP dosage has become a very complex task. The chemistry of the mode of action of ZDDP itself is complicated and so the nature of its interactions with other additives needs investigating all the more. Interaction between ZDDP and fatty acids, again in lubricating oil formulations, shows a considerable amount of mechanical test wear. The antiwear property of ZDDP is reduced by fatty acid additive due to the adsorbed layer of fatty acid, and the solubilization process, which disturbs the function of ZDDP (Otsubo, 1975), see Fig. 2.11. 

The differences in antiwear properties of disulfides are related to their ability to be physisorbed about 100 to 1000 times faster than monosulfide on metal surfaces. The differences can be explained in terms of the lower energy needed for the formation of the same number of RS" ions from disulfides (Kajdas,1994). The exposed metal surface is extremely reactive to lubricant components, especially antiwear and extreme-pressure additives resulting the formation of a film on the contact surface. The reaction of emitted electrons of low energy (1 to 4 eV) with molecules of oil additives adsorbed on the friction surface may lead to formation of negative ions and negative ion radicals. The investigator (Kajdas, 1994 and 1985) pointed out the indispensability of the metal oxide film on the rubbing surface from the viewpoint of the theory of sulfide film formation. 

N.N.Loznetsova, K.A.Pavlov, J.P.Toporov, G.G.Shchegolev. A role of micelle formation in displaying antiwear properties in lubricant oils. // Tezisy dokl. II Mezhd.Confer. Colloid-2003 - 2003. -p.184. 

Lubricating-oil consumption in modem engines is generally very low (0.1 liters per 1,(XX) km), and their contribution to catalyst deactivation is small. However, with the requirement for extended catalyst durability and extended drain periods for oils, there is considerable interest about the effect of the oil additives on catalyst life. The chief component of the oil that affects catalyst durability is phosphorus, which is usually present in the form of zinc dialkyl-dithiophosphate (ZDDP). Both combusted and uncombusted forms of ZDDP can reach the catalyst, resulting in different effects on activity depending on the temperature of operation. The level of phosphorus in the oil and the amount of alkaline earth metals present (such as calcium) can dictate the extent to which phosphorus can be deposited on the catalyst. However, studies have shown quite clearly that well-formulated lubricants and well-designed catalysts ensure that the antiwear properties of the oils are maintained and that catalyst-equipped vehicles meet the emission standards required [15,16]. 

Yu et al. [31 ] synthesized and evaluated a, co-diimidazoliumalkylene hexafluoro-phosphate as a lubricant for steel/steel contacts and found that the tribological properties of ILs was superior to those of traditional space PFPE lubricants and L-P106. In particular, high-temperature diimidazolium-based ILs showed very good antiwear properties. 

Generally, however, it was found that ILs provide better lubricalion for aluminum compared to conventional lubrication oils because the former has better friction reduction and antiwear properties compared to the latter. 

In addition to ILs as additives in liquid lubricant, they can also be added in polymer materials. Bermudez et al. [50, 51, 67, 68] performed several studies on the use of ILs as additives for polymer materials. They found that polymers to which ILs had been added produced better friction reduction and antiwear properties than blank polymer. 

Sulphur/nitrogen and sulphur/phosphorus compounds Other multifunctional sulphur/nitrogen, sulphur/phosphorus-based additives have antioxidant and antiwear properties. These additives react with peroxy radicals and hydroperoxides, thus stabilising industrial lubricants and engine oils. Syntheses and generalised chemical structures are as in Reactions (4.67. 69) [64, 72, 73] ... 

The properties of polymers are hardly affected by the incorporation of phosphorus. Diesters of H-phosphonic acid and their inunediate derivatives have found a number of applications in polymer synthesis such as flame retardants, antioxidants, heat and Ught stabilizers, catalysts, degrading agents, and alkylating agents. They are also used as corrosion inhibitors, scale inhibitors, and lubricants (antiwear and load-carrying additives). 

Owing to their lipophilic chains and their very small size, micelles are very easily dispersed in base oils and dispersion is stable for a long time. Overbased micelles, used initially as detergents, also present antiwear properties (see Chapter 4). Overbased micelles can be used in several ways (a) as thin coatings deposited on a solid surface, (b) as a colloidal dispersion in apolar medium (oil, grease, etc.) and (c) in gas phase lubrication. 

Uses Lubricant, antiwear agent for metalworking fluids, sol. oils, semisynthetics, synthetics, syn. cutting and grinding fluids, boundary lubrication, metal removal corrosion inhibitor for ferrous and nonferrous metals wetting agent Features Stable in hard water Properties COF 0.047 Maxiube LA-61 [PCC Chemax]... 

Finally, biolubricants based on canola biodiesel have the potential to substitute petroleum-based automotive lubricants thus they present low cloud and pour point properties, good friction and antiwear properties, low phase transition temperature, and low viscosity (Sharma et al., 2015). 

More recendy, molecular molybdenum-sulfur complexes and clusters have been used as soluble precursors for M0S2 in the formulation of lubricating oils for a variety of appHcations (70). Presumably, the oil-soluble molybdenum—sulfur-containing precursors decompose under shear, pressure, or temperature stress at the wear surface to give beneficial coatings. In several cases it has been shown that the soluble precursors are trifunctional in that they not only display antifriction properties, but have antiwear and antioxidant characteristics as weU. In most cases, the ligands for the Mo are of the 1,1-dithiolate type, including dithiocarbamates, dithiophosphates, and xanthates (55,71). 

Hydraulic Fluids and Lubricants. The use of borate esters in hydrauHc fluids (qv) and lubricants (see Lubrication and lubricants) has been described in numerous patents (40,43,44). A variety of borate esters have been described that can be used as multiflinctional lubricant additives having antiwear and antifriction properties (45). 

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