Interfacial Tension and Wetting

Interfacial effects are gaining increasing attention today. Although significantly less known than viscosity, the interfadal tension can be a crucial parameter in technical processes. Interfadal tension and contad angles can be determined with the pendant 

---

Polysorbate 80 is widely used as a nonionic surfactant in liquid pharmaceutical products such as inhalation, suspension, and nasal suspension products, due to its properties of solubilization, reduction of surface and interfacial tension, and wetting. Direct analysis of Polysorbate 80 is quite time consuming. Size-exclusion chromatography (SEC) has been reported [5] in which a mobile phase contained the surfactant at concentrations above the critical micelle concentration. Polysorbate 80 appeared as a very broad peak and coeluted with other peaks, which makes quantification in Nasonex impossible. 

Nickel, D., Speckmann, H.D. and von Rybinski, W. (1995) Interfacial tension and wetting as parameters for product characterization. Tenside Surfactants Det. 32(6), 470M. 

Interfacial and capillary phenomena are present in multiple biological processes. Some examples are duck s feathers impermeability, spiders sticky traps, and Lotus leaf s effect. The last subject is considered in a separate chapter due to its important technological applications. The basis to understand all those processes is the focus of the present chapter, divided into three subsections. The first one addresses the fundamentals of interfacial tension and wetting conditions as thermodynamical concepts. In the second, capillarity effects under dynamical conditions are considered. The third section is devoted to liquid films, their stability, and the spontaneous retraction in simple geometries. 

Interfacial phenomena interfacial tension and wetting angles... 

Oily soils are removed by emulsification, solubihzation, or rollover mechanisms. Surface tension, interfacial tension, and wetting properties of a surfactant play important roles in removing oily soil. Again a well-balanced HLB in a particular series of surfactants with similar structure will play an important part in determining the detergency performance of the surfactant on the oily soil. The data show that in the cocoamide MEA series the 5-mole adduct has the best detergency for oily soils, while for tallow, the 10-mole ethoxylate is the best performer, followed by the 15-mole and the 20-mole ethoxylate. 

By virtue of their simple stnicture, some properties of continuum models can be solved analytically in a mean field approxunation. The phase behaviour interfacial properties and the wetting properties have been explored. The effect of fluctuations is hrvestigated in Monte Carlo simulations as well as non-equilibrium phenomena (e.g., phase separation kinetics). Extensions of this one-order-parameter model are described in the review by Gompper and Schick [76]. A very interesting feature of tiiese models is that effective quantities of the interface—like the interfacial tension and the bending moduli—can be expressed as a fiinctional of the order parameter profiles across an interface [78]. These quantities can then be used as input for an even more coarse-grained description. 

In addition to the environmentally benign attributes and the easily tunable solvent properties, other important characteristics such as low interfacial tension, excellent wetting behavior, and high diffusion coefficients also make SCCO2 a superior medium for the synthesis of nanoscale materials [2]. Previous works on w/c RMs showed that conventional hydrocarbon surfactants such as AOT do not form RMs in scCOi [3] AOT is completely insoluble in CO2 due to the poor miscibility of the alkyl chains with CO2, restricting the utilization of this medium. Recently, we had demonstrated that the commonly used surfactant,... 

The computer interface system lends itself well to the determination of interfacial tension and contact angles using Equation 3 and the technique described by Pike and Thakkar for Wilhelmy plate type experiments (20). Contact angles for crude oil/brine systems using the dynamic Wilhelmy plate technique have been determined by this technique and all three of the wetting cycles described above have been observed in various crude oil/brine systems (21) (Teeters, D. Wilson, J. F. Andersen, M. A. Thomas, D. C. J. Colloid Interface Sci., 1988, 126, in press). The dynamic Wilhelmy plate device also addresses other aspects of wetting behavior pertinent to petroleum reservoirs. 

Wettability refers to the preferential spreading of one fluid over solid surfaces in a two-fluid system and is dependent upon the interfacial tension. The wetting... 

Surfactants fulfil many functions, such as detergency, micelle stabilization, interfacial tension reduction, wetting, and so on. In hydrocarbons, however, surfactants are not capable of lowering the surface tension, because these solvents... 

This equation is basic for determination of interfacial tension and for explaining phenomena of wetting and adhesion [iii-v] including electrochemical experiments [vi]. For the work of adhesion between two immiscible liquids see -> Dupre equation. 

The decrease of the column performance is partially caused by longitudinal mixing and insufficient wetting of the packing due to detachment of the liquid film as shown by Blaha [5]. Another disadvantage of columns is the low gas capacity required to avoid flooding because of the low interfacial tension and the low density differences between the phases. 

Non-equilibrium liquid films formed in the process of spreading have been considered in some early works, especially in the test of the theory of interfacial tension and the rule of Antonov [204], A review on the rule of Antonov and its interpretation on the basis of isotherms of disjoining pressure in wetting films is presented in [532]. However, these works do not deal with precise measurement of film thickness and the studies confined only the kinetics of spreading and lens formation. 

The sol, which is a fluid mixture of water (sometimes containing organic solvent), catalyst and oligomerised silanes, turns into a solid, wet gel after some period of reaction time. The wet gel contains open channels, which are precursors to pores in the dried material. The resultant porosity of the dried gel is directly affected by the drying conditions, gel-solvent interfacial tension, and reactivity of... 

Insoluble solids, regardless of particle size, that have a relatively low interfacial tension and are readily wetted by water are called hydrophilic solids. These solids include clays (bentonite, kaolin, talc, magnesium aluminum silicate) bismuth salts, barium sulfate, carbonates, hydroxides, or oxides of calcium, magnesium, zinc, and aluminum and titanium dioxide. The hydro-philicity of a powder surface can be investigated with the help of moisture absorption studies in which the solid particles are exposed to varying relative humidities. Insoluble powders that absorb moisture below relative humidities of 70-80% at room temperature are said to be hydrophilic solids. 

---