Soft-core RMs

The presence of chemical guest species in the water pool of soft-core RMs can modify the organization of the micellar components. The chemical guest species may compete with the surfactant for water molecules to build its own hydration shell. Ions may be specifically bound to the charged groups of the micellar wall resulting in dramatically changed properties of micelles. 

Organic acids may be formed as a result of progressive oxidation of the oil, and these acids may be deactivated (solubilization) by hydrogen bonding complex formation with detergents and dispersants (soft-core RMs). See the detailed discussion in Chapter 3.0 (Denison, 1994 Kreuz, 1970 Salino and Volpi, 1987). 

It is generally accepted that the soft-core RMs contain amounts of water equal to or less than hydration of water of the polar part of the surfactant molecules, whereas in microemulsions the water properties are close to those of the bulk water (Fendler, 1984). At relatively small water to surfactant ratios (Wo < 5), all water molecules are tightly bound to the surfactant headgroups at the soft-core reverse micelles. These water molecules have high viscosities, low mobilities, polarities which are similar to hydrocarbons, and altered pHs. The solubilization properties of these two systems should clearly be different (El Seoud, 1984). The advantage of the RMs is their thermodynamic stability and the very small scale of the microstructure 1 to 20 nm. The radii of the emulsion droplets are typically 100 nm (Fendler, 1984 El Seoud, 1984). 

Effective pH values in soft-core RMs. Characterization of the acidity in the aqueous soft-core is important as ionizable compounds are solubilized in the water pool. The micellar core has a very high degree of organization of water. The water pool within reverse micelles is a different solvent than bulk water. The most interesting range of water content corresponds to rather small water pools (water-to-surfactant ratio of 3 to 10) in which peculiar properties of water cause the largest changes in behavior as compared to their behavior in bulk water. A water to surfactant ratio of 1 1 represents a very small, almost undetectable, quantity of... 

Fig. 3.4. The anionic type soft-core reverse micelles with /7-nitrophenol (ROH) located (a) on the internal wall of the anionic group, there is no "free" water, Wo < 10 (b) internally hydrated by "free water" in the water pool unless Wo > 10 (c) the acidic molecules can be adsorbed externally by soft-core RMs at the interface of an detergent-stabilized water pool, Wo > 30...

Considering these results, the main difference between the antiwear action of the ZDDP soft-core RMs and the hard-core RMs is clear. In the case of ZDDP soft-core RMs, the anti wear film formation requires that chemical reactions occur between the additive and the metallic surfaces. In the case of hard-core RMs, the mineral material (CaC03) is directly introduced to the sliding contact and undergoes small physicochemical changes during the film build-up. Consequently no chemical reaction with the substrate surfaces is required. 

X-ray absorption study of tribofilms generatedfrom a combination of ZDDP and borate-sulfonate RMs was used to determine the chemistry of tribochemical films at the surface and the bulk The calcium phosphate content in the tribofilm generated from either ZDDP + borate-sulfonate RMs or from ZDDP + calcium sulfonate soft-core RMs is similar (Varlot et al., 2001). Calcium sulfonate S(+5) undergoes disproportion reaction to form sulfate S(+6) and sulfite S(+4), and the presence of ZDDP affects the disproportion process. Close to the steel surface, the... 

Surface processes under rubbing conditions Soft-core RMs Hard-core RMs... 

Solubilization By reference to Figure 3.1, The soft-core RMs , explain the solubilization process of carboxylic acids, such as acetic acid and oleic acid by calcium phenolate RMs in engine oil. 

Neutralization and solubilization What are the differences and similarities (if any) in the concepts of neutralization and solubilization of oleic acid and sulfuric acid by soft-core RMs and hard-core RMs in lubrication formulations ... 

Tribofilm composition Explain the polyphosphate chain length in the bulk and on the surface when ZDDP is in the presence of calcium sulfonate and calcium phenolate soft-core RMs (for solution see Table 4.4). 

RFG RME Rust inhibitor Reformulated gasoline. Repassed methyl ester. Lubricant additive minimizes rust by preferential adsorption of polar compounds on metal surface to provide a protective film and/or neutralization of corrosive acids, e.g., fatty acids, nitrogen compounds, carbonate-alkylbenzenosulfonate.RMs. Water is solubilized by soft-core Rms. 

During tribochemical processes, soft-core RMs formed in oil-based fluids and hard-core RMs in water-based fluids transfer additives, forming a copper tribofilm during the... 

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