Interfacial tension factors that affect

It is well established that ultralow interfacial tension plays an important role in oil displacement processes [16,18]. The magnitude of interfacial tension can be affected by the surface concentration of surfactant, surface charge density, and solubilization of oil or brine. Experimentally, Shah et al. [23] demonstrated a direct correlation between interfacial tension and interfacial charge in various oil-water systems. Interfacial charge density is an important factor in lowering the interfacial tension. Figure 6 shows the interfacial tension and partition coefficient of surfactant as functions of salinity. The minimum interfacial tension occurs at the same salinity where the partition coefficient is near unity. The same correlation between interfacial tension and partition coefficient was observed by Baviere [24] for the paraffin oil-sodium alkylbenzene sulfonate-isopropyl alcohol-brine system. 

Water Uptake. There is evidence to suggest that water uptake caused by capillary forces is the crucial factor in the disintegration process of many formulations. In such systems the pore structure of the tablet is of prime importance and any inherent hydrophobicity of the tablet mass will adversely affect it. Therefore, disintegrants in this group must be able to maintain a porous structure in the compressed tablet and show a low interfacial tension towards aqueous fluids. Rapid penetration by water throughout the entire tablet matrix to facilitate its breakup is thus achieved. Concentrations of disintegrant that ensure a continuous matrix of disintegrant are desirable and levels of between 5 and 20% are common. 

Emulsification is a stabilizing effect of proteins a lowering of the interfacial tension between immiscible components that allow the formation of a protective layer around oil droplets. The inherent properties of proteins or their molecular conformation, denaturation, aggregation, pH solubility, and susceptibility to divalent cations affect their performance in model and commercial emulsion systems. Emulsion capacity profiles of proteins closely resemble protein solubility curves and thus the factors that influence solubility properties (protein composition and structure, methods and conditions of extraction, processing, and storage) or treatments used to modify protein character also influence emulsifying properties. 

Literature data is almost entirely for small equipment whose capacity and efficiency cannot be scaled up to commercial sizes, although it is of qualitative value. Extraction processes are sensitive because they operate with small density differences that are sensitive to temperature and the amount of solute transfer. They also are affected by interfacial tensions, the large changes in phase flow rates that commonly occur, and even by the direction of mass transfer. For comparison, none of these factors is of major significance in vapor-liquid contacting. 

Figure 13. Electrophoretic mobility (Fen Kem 3000) of the emulsion from Figure 12 after cationic polymer addition (A). The cationic polymer has neutralized the oil droplet surface charge and electrostatically destabilized the emulsion. The photomicrograph (B) shows this destabilized emulsion that has begun to flocculate or a lomerate but that is not coalescing. This electrostatic destabilization is not the only factor affecting emulsion stability. Factors such as interfacial tension and film strength can prevent coalescence of the emulsion droplets, even though they can now closely approach each other and ag omer-...

The utility of liquid-liquid extraction as a separation tool depends upon both phase equilibria and transport properties. The most important physical properties that influence transport properties are liquid-hquid interfacial tension, liquid density, and viscosity. These properties influence solute diffusion and the formation and coalescence of drops, and so are critical factors affecting the performance of hquid-liquid contactors and phase separators. 

The reduction of the tension at an interface by a surfactant in aqueous solution when a second liquid phase is present may be considerably more complex than when that second phase is absent, i.e., when the interface is a surface. If the second liquid phase is a nonpolar one in which the surfactant has almost no solubility, then adsorption of the surfactant at the aqueous solution-nonpolar liquid interface closely resembles that at the aqueous solution-air interface and those factors that determine the efficiency and effectiveness of surface tension reduction affect interfacial tension reduction in a similar manner (Chapter 2, Section IIIC,E). When the nonpolar liquid phase is a saturated hydrocarbon, both the efficiency and effectiveness of interfacial tension reduction by the surfactant at the aqueous solution-hydrocarbon interface are greater than at the aqueous solution-air interface, as measured by pC2o and IIcmc, respectively. The replacement of air as the second phase by a saturated hydrocarbon increases the tendency of the surfactant to adsorb at the interface, while the tendency to form micelles is not affected significantly. This results in an increase in the CMC/C2o ratio. Since the value of rm, the effectiveness of adsorption (Chapter 2, Section IIIC), is not affected significantly by the presence of the saturated hydrocarbon, the increase in the... 

It is also seen that there are great differences between systems, both in the preexponential factor—which primarily affects the overall level of the nucleation rate—and in the exponential factor—which primarily determines the steepness of the curve with respect to temperature. The difference Teq — Thom roughly equals 40 K for ice, 28 K for sucrose, and 26 K for tristearate in paraffin oil. In natural fats, where triglycerides crystallize from a triglyceride oil, the temperature difference is only about 20 K, presumably because the interfacial tension between oil and crystal is far smaller (about 4 rather than lOmN-m-1). 

In Section 3.3 we have briefly indicated that there are various factors that can affect water solubilization in reverse micelles. The importance of the oil-water interface in the context of water solubilization cannot just be overemphasized, and the entity that first comes to the forefront is the surfactant film that separates the two immiscible phases. At the very beginning, therefore, some basic and relevant points on the surfactant film are described below in brief [113, 114, 124, 125, 3]. The interfacial surfactant film can be described as a two-dimensional system in which one can consider a pressure term n [113] this term, characteristic of the film, defines the difference in the oil/water interfacial tension before and after addition of the surfactant to form an interfacial film ... 

It was shown that the surfactant adsorption decreased the interfacial tension between the stationary and mobile phases. In the absence of micelles (ion-pair chromatography), the nonionic solute retention factor was affected by this interfacial tension change according to eq. 4.7 [32] ... 

The interplay between these various factors is complex and often requires experimental measurement under as realistic conditions as possible to appropriately determine the impact of surfactant on wettability. It is the migration to, and the adsorption of, the surfactant at the fluid and solid interfaces along with the orientation and density of the adsorbed surfactant molecules that modifies the fluid-surface interfacial tension/ wettability. Surfactant adsorption at an interface is a necessary, but not a sufficient condition for wettability alteration. Although details of adsorption will be covered in Chapter 4, this section includes a brief treatise on it with the other known variables that can affect wettability modification with surfactants. 

In manufacturing and processing polymer blends, it is important that the viscosity ratio be within the optimal range in the actual processing conditions. Thus, not only the polymers to be blended but also the temperature and shearing conditions should be carefully selected. Other factors, such as interfacial tension and elasticity of the blended polymers, affect the blend morphology as well. 

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