C.R Singleterry

The adhesion of ice to lubricated surfaces

Abstract The adhesion of ice to lubricated steel has been shown to vary over a wide range depending upon the polar organic additive present in the lubricating oil. The adhesion is least for systems showing contact angles of 170° or larger through water drops on steel submerged in the oil solutions. The extremely low adhesions sometimes observed in such systems arise because water does not readily displace the final thin film of bulk oil from the metal surface to establish true water/solid contact. High water contact angles are associated with strong adsorption of the polar additive at the oil/metal interface and with relatively low adsorption in the oil/water interface.

Effect of the cation on micelle formation by sulfonates in benzene

Abstract The states of aggregation of dinonylnaphthalene sulfonates of ten cations (Li, Na, Cs, NH4, Mg, Ca, Ba, Zn, Al, and H) have been studied in benzene by fluorescence depolarization, cryoscopy, viscometry, and densimetry. The micelles observed by fluorescence depolarization contained 9 to 14 acid residues each. Their aggregation number was usually independent of concentration and almost independent of the water content of the system, although moisture moderately increased the aggregation of the zinc salt. The relative insensitivity of the sulfonate micelle size to influences of the cation and moisture contrasts sharply with the behavior of the phenyl-stearate soaps, whose aggregation depends critically upon these variables. This indicates that the size of the dinonylnaphthalene sulfonate micelles depends primarily on the geometry of the acid residue. However, the apparent volume of the anion was inversely related to the coordinating tendency of the cation, suggesting that coordination forces are a factor in micelle stability. The acid is associated principally to the dimer, but in the presence of water some larger aggregates are formed. Viscosities of the sulfonate solutions exceeded those predicted by the Einstein relation for spherical particles. This anomaly corresponded to an asymmetry of the order of 2, or a solvation of 10% to 20%. It might also have resulted from surface irregularities of the micelles. Present evidence does not justify a choice among these explanations. Cesium dinonylnaphthalene sulfonate was shown cryoscopically to have an aggregation number of 6 or more. It differed from the other micelle-forming sulfonates, however, in not solubilizing enough Rhodamine B to permit determination of micelle size by the fluorescence depolarization technique. The micelle size found cryoscopically for the magnesium salt agreed with that derived from fluorescence depolarization measurements.

Micelle formation by sulfonates in a nonpolar solvent

Abstract The micellar properties of oil-soluble sulfonates in benzene have been studied by the fluorescence depolarization method. In moist benzene, the dinonylnaphthalene sulfonates of barium and sodium aggregate to form micelles of 7 to 8 and 12 to 13 monomers, respectively; the size of these micelles is not sensitive to water concentration. The critical range for micelle formation of these sulfonates is estimated at 1 × 10 −6 to 1 × 10 −7 formula weight per liter. A barium petroleum sulfonate was found to aggregate in micelles of 34 to 35 monomers. The difference between the sizes of micelles of the two types of sulfonates is explained in terms of the geometries of the respective monomers. The formation of Rhodamine B-sulfonate complexes has been observed, requiring a slight revision of previously developed methods for treatment of the data. The micellar nature of these substances in nonpolar solvents supports a previously published explanation of their effectiveness in reducing the corrosion potentials of acids in lubricating oils.

The critical range for micelle formation by an oil-dispersible soap in a hydrocarbon solvent

Abstract Micelle formation by the oil-dispersible soap, calcium xenylstearate, in moist benzene has been studied by fluorescent dye techniques, utilizing Rhodamine B and Acridine Orange. A treatment is presented for the interpretation of fluorescence depolarization data obtained from a system in which the emitting dye is present partly as a component of soap micelles and partly in true molecular solution. This method has special usefulness for identifying the onset of micelle formation in very dilute solutions. The midpoint of the critical range for the formation of micelles in this case is found to be 0.6 × 10 −6 mole/l.; the size of the micelles is essentially constant over the range from 1 × 10 −6 to 7 × 10 −3 mole/l. The data obtained are consistent with a simple mass law equilibrium between molecularly dissolved and micellar soap. A knowledge of this equilibrium provides guidance in the development of improved rust-inhibiting oils.

The distribution of acetic acid between solvent and soap micelles in benzene solutions

Abstract The distribution of acetic acid between benzene and micelles of sodium dinonylnaphthalene sulfonate, magnesium dinonylnaphthalene sulfonate, and magnesium phenylstearate was examined by measurements of the vapor composition in equilibrium with such systems. In each case the initial increments are more firmly bound than later portions, the amount of strongly bound acid ranging from one to two molecules per cation present. The magnesium salts bind the acid more strongly than the sodium compound. The partition coefficient for acid at higher concentrations is one or two orders of magnitude smaller than that for the initial increments. Its magnitude depends on the nature of the anion in the micelle. Water was found to reduce the initial acid-binding capacity of the magnesium salts. The data indicate that the coordinating properties of the cation are a major factor in the initial firm binding of acetic acid by oil-soluble soap micelles, but that significant amounts of acid are more loosely held by forces which may be attributed to the organic anion present.

Rheological properties of a lubricating grease

Abstract The results here described show that when the phenomena of flow in a capillary are separated from accompanying effects such as piston drag, entrance losses, and temperature rise during flow, a shear-stable grease of the 14G8 type behaves substantially as a Bingham plastic whose flow can be specified in terms of yield value and mobility. The yield value so obtained is in reasonable agreement with that measured directly. The reciprocal of the mobility, which can be identified with the limiting apparent viscosity approached at high rates of flow, is from two to five times the viscosity of the diester fluid present in the grease. These magnitudes are reasonable in the light of the volume and particle shape of the suspended soap phase. A graphic method has been developed for the analysis of flow data for Bingham plastics in terms of the Buckingham equation for plastic flow in tubes of circular cross section. This treatment permits direct computation of both the yield value and the mobility of such a plastic from data for flow under two suitable pressures without resort to the trial-and-error operations previously employed for this purpose.