Friction modifier additives

The other surface-active chemical components include antiwear additives, friction modifiers, and antifoam additives [15]. The functions of these other lubricant additives, as their names imply, are quite different from these two surfactants. For example, antiwear additives, such as zinc dial-kyldithiophosphates, are used to prevent wear on engine parts friction modifiers, such as glycerol monooleate, are used to reduce boundary friction in engine operation to improve fuel economy antifoam additives such as polymethylsiloxane are used to inhibit foam formation. Excessive foam formation in lubricants can cause inadequate oil supply to certain parts of the engine and a high rate of oil loss. 

It can be seen that with 10W40, the valve train friction rises with oil temperature but with 5W30 it can be seen that the friction decreases and then increases. In order for valve train fiiction to decrease with rising temperature the lubrication regime must be mostly hydrodynamic. The benefit of 5W30 can be clearly seen at higher lubricant temperatures due to the presence of the temperature sensitive additive, friction modifier. 

A) Surface protective additives (i) antiwear (AW)/extreme-pressure (or temperature) improver (EP), (ii) anticorrosion and rust inhibitor, (iii) detergent and dispersant, and (iv) friction modifier. Examples of protective additives are listed in Table 2.4. 

One oil contained a soluble molybdenum friction modifier additive while the other did not. The IR bands in the 1200 to 1100 cm 1 and 650 to 600 cm 1 regions have been assigned to the symmetric PO 2 stretching and symmetric bending modes, respectively, observed in divalent cations in metaphosphate glasses. 

Both XPS and Auger analyses were performed for tribofilm. The Auger results revealed higher concentration of Fe, Zn, Mg and P, but lower levels of carbon relative to XPS. Phosphorus is present in phosphate form and sulfur as sulfide in unmodified oil. The oil containing a soluble molybdenum friction modifier additive formed films which were thinner and less continuous than films formed from the unmodified oil. The film was dominated by magnesium phosphate which was identified by AES, and by the combination of XPS and IR. Sulfur was present as sulfate and sulfide while molybdenum was present as Mo+4 and Mo+6, as shown in Fig. 4.8 (Lindsay et al., 1993). 

Fig. 4.8. XPS Mo3d spectra from the film produced from engine oil containing a soluble molybdenum friction modifier additive from the outer ring region (A), the middle ring region (B), and the center ring region (C), as well as the spectrum of the agent, M0S2 (D), (Lindsay et al., 1993)...

The lubrication system is extremely complex. The mechanism of lubrication is partly dictated by the nature of interactions between the lubricant and the solid surface. Additives blended into lubricating oil formulations either adsorb onto the sliding surfaces, eg., fatty alcohols, fatty amines, amides, phosphoric acid esters (friction modifiers), or react with the surface, eg., ZDDP, MoDTC, MoDDP organic phosphates (extreme pressure). Some interactions affecting the surfaces of metals include adsorption, chemisorption, and tribochemical reactions-these form new compounds on the surface and lubrication by reaction products (Bhushan and Gupta, 1991 Briscoe et al., 1973 Briscoe and Evens, 1982 Heinicke, 1984 Hsu and Klaus, 1978 and 1979 Klaus and Tewksbury, 1987 Lansdown, 1990 Liston, 1993 McFadden et al., 1998 Studt, 1989). 

Phosphorus is present in zinc dialkyldithiophosphate and deactivate platinum catalysts in engine exhaust systems. Using zinc, antimony and oxothiomolybdate dialkyl-dithiocarbamate (MoDTC) complexes alone or in combination with other lubricating oil additives appears to solve this problem. Antimony complexes are used also as extreme pressure agents while molybdenum ones as friction modifier additives (Hill et al., 1994). Analyses of Zn(dtc)2 decomposition using the thermogravimetric method, flash vacuum pyrolysis, and four-ball machine... 

Sensitivity of exhaust - after treatment devices. It is clear that excessive deposition of phosphorus and sulfur on the catalyst can cause the reduction in system efficiency. Oil phosphorus contaminant comes from the oil additive ZDDP. The reduction in its use adversely affects both antiwear and antioxidation performance. Sulfur comes from the base oil, antiwear additives, detergents, organomolybdenum friction modifiers, and from the fuel. There is strong pressure from OEMs to reduce the sulfur level of the fuel, and to reduce the sulfur contamination of the catalyst, which results from presence of sulfur in oil. 

As for all additives, interactions with other additives in solution, Fig. 3.16, and competition for surface reaction sites together with the effect of environmental factors such as temperature, blow-by gases, water and fuel dilution have variable effects on the formation of the film. Because ZDDPs are much more widely used as antiwear performance additives compared to other classes of compounds, these additive effects will now be discussed in greater detail than has been the case for other classes of anti-wear/friction additives. In particular the influence of structure, concentration, dispersant, detergent, antioxidancy and friction modifier on friction and wear will be discussed. In addition the influence of NO c and H2O will be briefly illustrated. 

Both low friction and low wear can be achieved if these films of friction modifier are laid down on thicker films of, say, ZDDP. The anti-wear and friction properties of several classes of additives have been described together with the influence of... 

In addition to being good friction modifiers with anti-wear performance, organomolybdenum compounds are also excellent antioxidants at low concentrations, at or below 100 ppm Mo. In fact, over 50% of ILSAC GF-4 engine oils contain organomolybdenum compounds at or above 60 ppm Mo. 

Antagonisms Between Friction Modifiers and Other Additives... 

Surface modification of nanoparticles in some cases allow the formation of stable dispersions in liquid hydrocarbons [57], If molybdenum sulphide nanoparticles are considered as friction-modifying additives for liquid lubricants, then a whole range of new possibilities appears. The action of tribologically active additives as nanoparticles has been proposed as in Fig. 8.6. 

Typical manual transmission fluids additive packs contain 6-10 components, many being the same components used for modern automatic transmission fluids. The key differences are the treat levels of components, e.g. dispersants and friction modifiers, and the type and level of antiwear components. A typical manual gearbox standard operating temperature of 90 C is not as thermally challenging as that of a modern automatic transmission in excess of 120°C. This is usually reflected in the superior oxidative stability exhibited by modern automatic transmission fluids compared with manual transmission fluids. Table 10.3 shows the generic composition of a manual transmission fluid, with the component(s) that differ from an automatic transmission fluid highlighted. 

The dependence was re-derived 42 years later for a telescopic flow of two polymers through a pipe [HeitmUler et al., 1964]. The two liquids formed a large number of concentric layers, each of the same crossectional areas. The fundamental condition that leads to the fluidity additivity relation was the continuity of the shear stress across the multi-stratified structure. Lin [1979] followed this derivation with an additional assumption that the shear stress of each layer can be modified by the presence of an additional frictional stress, Z = (P-1)(RAP/2L), where R is the capillary radius, AP is the pressure drop, and P is a characteristic material parameter in ... 

Chem. Descrip. Glyceryl oleate CAS 37220-82-9 EINECS/ELINCS 203-827-7 Uses Emulsifier for cosmetics and industrial applies. in mold release agents anti-icing fuel additive rust preventive vehicle for agric. insecticides lubricant in syn. fiber spin finishes (textiles) friction modifier for engine, hydraulic, and transmission fluids Regulatory EPA exempt... 

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