Molybdenum disulfide, effect

Dry lubricants are usually added to the powder in order to decrease the friction effects. The more common lubricants include zinc stearate [557-05-17, lithium stearate [4485-12-5] calcium stearate [1592-23-0] stearic acid [57-11-4] paraffin, graphite, and molybdenum disulfide [1317-33-5]. Lubricants are generally added to the powder in a dry state in amounts of 0.25—1.0 wt % of the metal powder. Some lubricants are added by drying and screening a slurry of powder and lubricant. In some instances, lubricants are appHed in Hquid form to the die wall. 

Titanium disulfide has been proposed as a soHd lubricant. The coefficient of friction between steel surfaces is 0.3, compared to only 0.2 for molybdenum disulfide. However, because it does not adhere strongly to metal surfaces, TiS2 is generally less effective than molybdenum sulfide. 

The coefficient of friction increases with increasing sliding speed up to about 150 ft/min, while beyond this point, the sliding speed has very little effect. Polytetrafluoroethylene filled with molybdenum disulfide has a coefficient of friction lower than for pure polymer under the same conditions. The decrease is attributed to the increased hardness of the... 

The shape of molecules and the types of bonding between them have significant effects on properties of materials. Examples include the wide variety of molecular shapes of silicates and the planar structures of talc, mica, clay, molybdenum disulfide, and graphite. 

Molybdenum disulfide is dispersed in greases and oils for lubrication in volatile carriers it is used to form dry coatings of lubricant. Sodium molybdate is an especially effective corrosion inhibitor on aluminum surfaces and is dissolved in cooling solutions to protect aluminum motor blocks in automobiles. 

Haltner, A.J. and Oliver, C.S., Effects of Chemical Properties of Molybdenum Disulfide on Frictional Behaviour, Symp. on Chem. of Friction and Wear, Divn. of Petroleum Chem., Am. Chem. Soc., (1958). 

Jamison, W.E., Electronic Effects on the Lubricating Properties of Molybdenum Disulfide and Related Materials, Proc. 2nd. Inti. Conf. on Solid Lub., 115-18 August, 1978), ASLE SP-6, p.1. 

Godfrey, D. and Nelson, E.C., Oxidation Characteristics of Molybdenum Disulfide and Effect of Such Oxidation on its Role as a Solid-Film Lubricant, NACA TN No. 1882, (May, 1949). 

Matsunaga, M. and Nakagawa, T., Effect of Various Vapors on Coefficient of Friction of Clean Molybdenum Disulfide, ASLE Trans., 19, 216, (1976). 

Tsuya, Y., Saito, K. and Suzuki, H., Effect of Viscosity of Oil Containing Molybdenum Disulfide on its Load-Carrying Capacity, Lubric. Eng., 31, 619, (1975). 

Bartz, W.J., Influence of Extreme Pressure and Detergent-Dispersant Additives on the Lubricating Effectiveness of Molybdenum Disulfide, Lubric. Eng. 33, 139, (1977). 

Bartz, W.J. and Oppelt, J., Lubricating Effectiveness of Oil-Soluble Additives and Molybdenum Disulfide Dispersed in Mineral Oil, ASLE Preprint No. 79-LC-1C-3. 

Godfrey, D. and Bisson, E.E., Effectiveness of Molybdenum Disulfide as a Fretting-Corrosion Inhibitor, NASATN-2180, (Sept. 1950). 

The specific reaction ( activation ) conditions for the conversion of catalyst precursors to unsupported catalysts have a direct effect on the catalytic activity and dispersion. The importance of reaction intermediates in decomposition of ammonium heptamolybdate and ammonium tetrathiomolybdate, and the sensitivity of these intermediates to reaction conditions, were studied in coal liquefaction systems. Recent results indicate that optimization of activation conditions facilitates the formation of a highly dispersed and active form of molybdenum disulfide for coal liquefaction. The use of the catalyst precursors ammonium heptamolybdate, ammonium tetrathiomolybdate, and molybdenum trisulflde for the conversion of coal to soluble products will be discussed. 

Risdon T J, Loban R D, Effect of Molybdenum Disulfide on the Wear Rates of Polymer Composites. Climax Molybdenum Company, Ypsilanti, MI, USA. 

Polytetrafluoroethylene, molybdenum disulfide, graphite, and aramid fibers reduce the frictional coefficient. These may be used as single friction additive, in combination with other fillers, and in combination with silicone oil. Table 5.17 illustrates effect of PTFE on the frictional properties of different polymers. 

Typical fillers used for reduction of wear include PTFE, silicone, graphite powder, molybdenum disulfide, and aramid fibers. Good results were also reported with mica and zirconia combination. Figure 8.36 shows the effect of mica and mica in combination with zirconia on the wear resistance of an epoxy resin. ... 

Molybdenum disulfide is known to stabilize polyarylate. It was postulated that two mechanisms may be responsible for this process the formation of coordination complexes between carboxyl groups and molybdenum disulfide and the reaction with oxygen (antioxidative effect). 

Figure 19-3. Effect of water vapor on the friction of molybdenum disulfide. Data by Matsunaga and Nakawaga [28].

Figure 19-4. Effect of relative humidity on the static friction of molybdenum disulfide films. Data by Pritchard and Midgley [32].

Figure 19-5. Effect of load and sliding speed on the lubricating action of molybdenum disulfide. From data by Haltner and Oliver [36].

Figure 19-7. Effect of vapors on the frictional behavior of molybdenum disulfide. (a) n-Butanol. (b) Water. (c) Benzene. (d) Heptane. (e) Dry air. Vapors at saturation pressure, 20 C. Data by J. Gansheimer [41].

Figure 19-16. Comparison of the effect of temperature on the durability and the friction of films of graphite fluoride and molybdenum disulfide. 440 C stainless steel riders against burnished films on 440 C stainless steel disks. Load 4.6 N. Sliding speed 1.6 m/s. Atmosphere dry air. A Friction of unlubricated metal. B Onset of thermal decomposition of (CF 12 n Fusaro and Sliney [73].

In plastics, wear depends on adhesion and deformation of soft material. Frictional forces are proportional to velocity rather than load as in the case of metals. A number of additives can improve wear and slip properties. PTFE has lower friction coefficient than any other material. Additionally, its particles form a film on shearing surfaces thus decreasing friction. Its addition is very effective in high-pressure applications. Optimum additions are 20% in crystalline polymers and 15% in amorphous ones. Molybdenum disulfide is primarily used in PA compounds. It works as a nucleating agent, promoting increased crystallinity in PA, thus providing harder, more wear... 

Hydrogen sulfide can react with M0O2 to produce molybdenum disulfide and water. The stabilities of the dioxide and disulfide depend upon the relative partial pressures of hydrogen sulfide and water vapor. Estimates of the effect of temperature upon the equilibrium are summarized in Fig. 7. 

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