Interfacial tension unsaturation

The effect of mutual saturation on the L-V and L-L interfacial tensions is effectively illustrated by considering the spreading coefficient of one liquid on another using both the initial (unsaturated) and equilibrium values of 7. Use the following data to calculate Se/, (equilibrium) and S B/A (nonequilibrium) ... 

Transport in unsaturated porous media is sufficiently complex when only two fluid phases, air and water, are present flow becomes even more complicated when a third fluid phase, such as an immiscible organic fluid, is involved. This third fluid phase (NAPL) arises when liquid hydrocarbon fuels or solvents are spilled accidentally on the ground surface or when they leak from underground storage tanks. The resulting subsurface flow problem then involves three fluids, air, water, and NAPL, each having different interfacial tensions with each other, different viscosities, and different capillary interactions with the soil. The adequate description of three-phase flow is still a topic of active research, but a few qualitative generalizations can be drawn. 

In other words, snrface tension may be considered to arise because of a degree of unsaturation of bonds that occurs when a molecnle resides at the surface and not in the bnlk. The term surface tension is used for solid-vapor or liquid-vapor interfaces. The term interfacial tension is more generally used for the interface between two liqnids, two solids, or a liqnid and a solid. 

Effect of Unsaturation. Alkane scans for C g carboxylic acid salts are compared in Figure 6. The alkane position of minimum interfacial tension (nm) increases with the degree of unsaturation. Increasing interfacial tensions are found in the order oleate, linolenate, linoleate. Sodium stereate, the corresponding... 

In view of the fact that one would expect interference with surfactant action by Ca(ll), Mg(ll), and other multivalent ions to be more severe with carboxylates than with sulfonates, the high interfacial tensions observed are discouraging from a practical point of view. However, there are interesting effects of structure between the salts studied, in particular between the cis and trans isomers, elaidate and oleate, and between compounds of different degrees of unsaturation. We are now preparing derivatives of these acids, in order to get more information on the effect of minor structure modifications. In addition, the possibilities of beneficial effects of cosurfactants have been as yet little explored. We believe it premature to conclude that carboxylate surfactants are of no utility. 

Several micellar-polymer flooding models as applied to the EOR are discussed in [237]. It is noted that the co-solvent ordinarily used in this process considerably influences not only the microemulsion stabilisation, but also the removal of impurities in the pores of the medium. The idea of using an alkali in micellar-polymer flooding is discussed in [238] in detail. The alkali effect on the main oil components was studied aromatic hydrocarbons, saturated and unsaturated compounds, light and heavy resin compounds and asphaltenes. It is demonstrated that at pH 12 surfactants formed from resins allow to achieve an interfacial tension value close to zero. For asphaltenes, such results are achieved at pH 14. In the system alkali solution (concentration between 1300 to 9000 ppm)/crude oil at 1 1 volume ratio a zone of spontaneous emulsification appears, which is only possible at ultra-low interfacial tensions. 

The acidic amino acids D,L-aspartic acid and L-glutamic acid also produced only small changes in the interfacial tension. On the other hand, the basic amino acids L-arginine and L-lysine as well as the unsaturated, neutral amino acids L-histidine, L-phenylalanine, and D,L-tyrosine produce large decreases in the interfacial tension [91]. 

The largest decrease in the interfacial tension is exhibited by the unsaturated amino acid L-tryptophan [91]. Tryptophan is adsorbed at full coverage in the perpendicular position except at the lowest concentration, whereas histidine is adsorbed planar at concentration below 0.05 M and flips up as molecules pack in at higher concentrations. Tyrosine, cystine, lysine, and methionine adsorb in the planar configuration [92]. 

As already mentioned, one outstanding property of microemiflsions is their excellent solubilization capacity. This can be explained in terms of very good efficacy of suitable emulsifier combinations resulting in an extremely low interfacial tension between the oil and the aqueous phase. A potential application is, e.g., the solubilization of perfume oils. Perfume oils are rather polar as compared with oils that are usually used in cosmetic formulations, e.g., paraffin or ester oils. This is validated by both the dielectric coefficients and the interfacial tension between oil and aqueous phase (Table 1). In particular, the relatively low interfacial tension without addition of a sinfac-tant indicates that the perfume oil may act, at least partially, as a lipophilic cosurfactant. A similar result was found for geraniol, a doubly unsaturated monoterpene alcohol, which is one of the most used perfume chemicals [24]. It plays a role both as cosurfactant at the interface and as cosolvent in the oil phase in a system consisting of octyl monoglycoside/geraniol/cyclohex-ane/water. 

The good wettability between the polymer matrix and the filler will help improve the interface of the composite strength, but infiltration is not the only condition of the interfacial bond. For example, the surface tension of vinyl silane is 33.4 mN/m, and it is an effective coupling agent for an unsaturated polyester the surface tension of ethyl silane is similar to that of vinyl silane, but it is not valid for an unsaturated polyester. ... 

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