Lubricity of metals

This discussion refers to external plasticization only. Several theories, varyiag ia detail and complexity, have been proposed ia order to explain plasticizer action. Some theories iavolve detailed analysis of polarity, solubiHty, and iateraction parameters and the thermodynamics of polymer behavior, whereas others treat plasticization as a simple lubrication of chains of polymer from each other, analogous to the lubrication of metal parts by oil. Although each theory is not exhaustive, an understanding of the plasticization process can be gained by combining ideas from each theory, and an overall theory of plasticization must include all these aspects. 

Review of the Lubrication of Metallic Surfaces by Zinc Dialkyldithiophosphates. 

Lubrication of sliding under extreme pressure. Lubrication of metal stamping, pressing, drawing, etc. 

Ren, D., Gellman, A.J. Reaction mechanisms in organophos-phate vapor phase lubrication of metal surfaces. Tribol. hit. 34, 353-365 (2001). doi 10.1016/S0301-679X(01)00025-l... 

An important discovery by the author in the early sixties was the strong affinity of the basal planes for n-paraffins and the fact that the affinity increases markedly with their chain length. This work was fully documented by the author [8, 11, 12] and led to a number of applications in selective adsorption and lubrication of metal surfaces. The normal paraffins were postulated to lie flat in the basal plane surface with their methylene gi oups falling neatly into the centres of carbon hexagons in the basal planes [11]. This was later confirmed by STM microscopy [38] and x-ray diffraction studies [39]. 

Chan FW, Bobyn JD, Medley JB, Krygio- JJ and Tanzer M (1999). The Otto Aufranc Award - Wear and lubrication of metal-on-metal hip implants. Clinical Orthopaedics and Related Research, 369, 10-24. 

Jagatia M and Jin ZM (2001) Elastohydrodynamic lubrication of metal-on-metal hip prosthesis unde steady-state Entraining Motion, Proc. Instn. Mech. En s., J. Eng. in Med., 215, 531-541. 

Smith, S. L., Dowson, D. and Goldsmith, A. A. J. (2001), The lubrication of metal-on-metal total hip joints A slide down the Stribeck curve, , Proceedings of the Institution of Mechanical Engineers, Part J, Engineering Tribology, Volume 215, No. J5, pp 483-484. 

Chan, F.W., Medley, J.B., Bobyn, J.D. and Krygier, J.J. Time-varying fluid film lubrication of metal-metal hip implants in simulator tests. Alternative Bearing Surfaces in Total Joint Replacement, (Eds. J.J. Jacobs and T.L. Craig), 1998, ASTM STP 1346, ASTM, West Conshohocken, PA, U.S.A., 111-128. 

Long-chain esters of pentaerythritol have been used as pour-point depressants for lubricant products, ranging from fuel oils or diesel fuels to the high performance lubricating oils requited for demanding outiets such as aviation, power turbines, and automobiles. These materials requite superior temperature, viscosity, and aging resistance, and must be compatible with the wide variety of metallic surfaces commonly used in the outiets (79—81). 

Typically, soHd stabilizers utilize natural saturated fatty acid ligands with chain lengths of Cg—C g. Ziac stearate [557-05-1/, ziac neodecanoate [27253-29-8] calcium stearate [1592-23-0] barium stearate [6865-35-6] and cadmium laurate [2605-44-9] are some examples. To complete the package, the soHd products also contain other soHd additives such as polyols, antioxidants, and lubricants. Liquid stabilizers can make use of metal soaps of oleic acid, tall oil acids, 2-ethyl-hexanoic acid, octylphenol, and nonylphenol. Barium bis(nonylphenate) [41157-58-8] ziac 2-ethyIhexanoate [136-53-8], cadmium 2-ethyIhexanoate [2420-98-6], and overbased barium tallate [68855-79-8] are normally used ia the Hquid formulations along with solubilizers such as plasticizers, phosphites, and/or epoxidized oils. The majority of the Hquid barium—cadmium formulations rely on barium nonylphenate as the source of that metal. There are even some mixed metal stabilizers suppHed as pastes. The U.S. FDA approved calcium—zinc stabilizers are good examples because they contain a mixture of calcium stearate and ziac stearate suspended ia epoxidized soya oil. Table 4 shows examples of typical mixed metal stabilizers. 

When the operating temperature exceeds ca 93°C, the catalytic effects of metals become an important factor in promoting oil oxidation. Inhibitors that reduce this catalytic effect usually react with the surfaces of the metals to form protective coatings (see Metal surface treatments). Typical metal deactivators are the zinc dithiophosphates which also decompose hydroperoxides at temperatures above 93°C. Other metal deactivators include triazole and thiodiazole derivatives. Some copper salts intentionally put into lubricants counteract or reduce the catalytic effect of metals. 

Workers in the metals treatment industry are exposed to fumes, dusts, and mists containing metals and metal compounds, as well as to various chemicals from sources such as grinding wheels and lubricants. Exposure can be by inhalation, ingestion, or skin contact. Historically, metal toxicology was concerned with overt effects such as abdominal coHc from lead toxicity. Because of the occupational health and safety standards of the 1990s such effects are rare. Subtie, chronic, or long-term effects of metals treatment exposure are under study. An index to safety precautions for various metal treatment processes is available (6). As additional information is gained, standards are adjusted. 

Table 8 summarizes domestic consumption by use for amyl alcohols. About 55% of the total 1-pentanol and 2-methyl-1-butanol production is used for zinc diamyldithiophosphate lubrication oil additives (150) as important corrosion inhibitors and antiwear additives. Amyl xanthate salts are useful as frothers in the flotation of metal ores because of their low water solubiUty and miscibility with phenoHcs and natural oils. Potassium amyl xanthate, a collector in flotation of copper, lead, and zinc ores, is no longer produced in the United States, but imports from Germany and Yugoslavia were 910 —1100 t in 1989 (150). 

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