Surface tension analysis

Figure 20 A schematic figure showing how to find critical micelle concentration (CMC) from surface tension analysis at varying emulsifier concentrations.

Increased fat and increased protein content in the mix delay adsorption of emulsifiers to air. Low temperature also has an inhibiting effect on this phenomenon. Surface tension analysis may be used to measure dosage effect in low-fat ice cream mixes. Such studies show that on a weight basis emulsifier is bound 10 times more strongly to fat than to milk protein in the mix49. 

Materials used for the case study included PEDOT PSS poly(3,4-ethylenedioxythiop hene) poly(styrenesulfonate) 1.3 %wt in water (Sigma Aldrich), Dimethyl Sulfoxide (Fischer Scientific) and Surfynol (AirProducts). For drop cast conductivity and surface tension analysis, PEDOT PSS/DMSO(0-5 wt%) and PEDOT PSS/DMSO(0-5 wt%)/Surfynol mixtures were prepared at ambient conditions and allowed to mix in a sonication bath for 24 hours Samples were drop spread onto cleaned glass slides between the ends of conducting aluminium tapes. All samples were allowed to anneal in ambient conditions for 30 minutes at 130 °C. 

In the remainder of this chapter, experimental work on the soluble surfactant sodium dodecyl sulfonate is presented along with suggested interpretations of the peak intensities and firequencies. In addition, the infrared results are compared with a surface tension analysis. 

It is important to point out that the Zisman critical surface tension analysis is only limited to low surface energy surfaces and alkane solvents, where van de Waals force is the prime interaction. Many exceptions were found with polar andH-bonding solvents. Despite this limitation, the Zisman analysis remains as one of the useful tools to estimate the surface tension of low surface energy material to date [13]. 

The type of behavior shown by the ethanol-water system reaches an extreme in the case of higher-molecular-weight solutes of the polar-nonpolar type, such as, soaps and detergents [91]. As illustrated in Fig. Ul-9e, the decrease in surface tension now takes place at very low concentrations sometimes showing a point of abrupt change in slope in a y/C plot [92]. The surface tension becomes essentially constant beyond a certain concentration identified with micelle formation (see Section XIII-5). The lines in Fig. III-9e are fits to Eq. III-57. The authors combined this analysis with the Gibbs equation (Section III-SB) to obtain the surface excess of surfactant and an alcohol cosurfactant. 

Another approach to measurement of surface tension, density, and viscosity is the analysis of capillary waves or ripples whose properties are governed by surface tension rather than gravity. Space limitations prevent more than a summary presentation here readers are referred to several articles [123,124]. 

One fascinating feature of the physical chemistry of surfaces is the direct influence of intermolecular forces on interfacial phenomena. The calculation of surface tension in section III-2B, for example, is based on the Lennard-Jones potential function illustrated in Fig. III-6. The wide use of this model potential is based in physical analysis of intermolecular forces that we summarize in this chapter. In this chapter, we briefly discuss the fundamental electromagnetic forces. The electrostatic forces between charged species are covered in Chapter V. 

The foregoing is an equilibrium analysis, yet some transient effects are probably important to film resilience. Rayleigh [182] noted that surface freshly formed by some insult to the film would have a greater than equilibrium surface tension (note Fig. 11-15). A recent analysis [222] of the effect of surface elasticity on foam stability relates the nonequilibrium surfactant surface coverage to the foam retention time or time for a bubble to pass through a wet foam. The adsorption process is important in a new means of obtaining a foam by supplying vapor phase surfactants [223]. 

Static mixing of immiscible Hquids can provide exceUent enhancement of the interphase area for increasing mass-transfer rate. The drop size distribution is relatively narrow compared to agitated tanks. Three forces are known to influence the formation of drops in a static mixer shear stress, surface tension, and viscous stress in the dispersed phase. Dimensional analysis shows that the drop size of the dispersed phase is controUed by the Weber number. The average drop size, in a Kenics mixer is a function of Weber number We = df /a, and the ratio of dispersed to continuous-phase viscosities (Eig. 32). 

Spray Correlations. One of the most important aspects of spray characterization is the development of meaningful correlations between spray parameters and atomizer performance. The parameters can be presented as mathematical expressions that involve Hquid properties, physical dimensions of the atomizer, as well as operating and ambient conditions that are likely to affect the nature of the dispersion. Empirical correlations provide useful information for designing and assessing the performance of atomizers. Dimensional analysis has been widely used to determine nondimensional parameters that are useful in describing sprays. The most common variables affecting spray characteristics include a characteristic dimension of atomizer, d Hquid density, Pjj Hquid dynamic viscosity, ]ljj, surface tension. O pressure, AP Hquid velocity, V gas density, p and gas velocity, V. ... 

Coran and Patel [33] selected a series of TPEs based on different rubbers and thermoplastics. Three types of rubbers EPDM, ethylene vinyl acetate (EVA), and nitrile (NBR) were selected and the plastics include PP, PS, styrene acrylonitrile (SAN), and PA. It was shown that the ultimate mechanical properties such as stress at break, elongation, and the elastic recovery of these dynamically cured blends increased with the similarity of the rubber and plastic in respect to the critical surface tension for wetting and with the crystallinity of the plastic phase. Critical chain length of the rubber molecule, crystallinity of the hard phase (plastic), and the surface energy are a few of the parameters used in the analysis. Better results are obtained with a crystalline plastic material when the entanglement molecular length of the... 

Hole size is as important in perforated plates without downcomers as far the sieve tray. Published data limits a full analysis of the relationships however, the smaller holes, Ys-in., Me-in., 4-in. appear to give slightly higher efficiencies for the same tray spacing [47]. Unfortunately the data [69] for the larger %-in. holes was not evaluated for efficiencies. Experience has indicated efficiencies equal to or only slightly, 10-15%, less for M-in. holes w hen compared to Me-in. holes for some systems. Holes as small as Mfrin., %2-in. and Me-in. were considered unsatisfactory for high surface tension materials such as water [47]. 

Molten salt investigation methods can be divided into two classes thermodynamic and kinetic. In some cases, the analysis of melting diagrams and isotherms of physical-chemical properties such as density, surface tension, viscosity and electroconductivity enables the determination of the ionic composition of the melt. Direct investigation of the complex structure is performed using spectral methods [294]. 

The results were presented in the form of isotherms, in which the properties are plotted versus the concentration. Nevertheless analysis of the isotherms was made based on available melting diagrams approach that the melts consist of TaFg3 and TaF7Cl3 complex ions. However, according to this general conception [312-314], the isotherm of the surface tension must, in such a case, have either a minimum or at least display prominence of the dependence in the direction of the concentration axis. 

As gas flows with fixed volumetric flow rate through an orifice gas sparger, bubbles are formed with diameter Analysis of bubble formation is based on the balance of buoyant force, as the bubbles leave the orifice and rise through the media (irApgDl)/6 with rest of the forces resulting from the surface tension, Trad. 

In their analysis, however, they neglected the surface tension and the diffusivity. As has already been pointed out, the volumetric mass-transfer coefficient is a function of the interfacial area, which will be strongly affected by the surface tension. The mass-transfer coefficient per unit area will be a function of the diffusivity. The omission of these two important factors, surface tension and diffusivity, even though they were held constant in Pavlu-shenko s work, can result in changes in the values of the exponents in Eq. (48). For example, the omission of the surface tension would eliminate the Weber number, and the omission of the diffusivity eliminates the Schmidt number. Since these numbers include variables that already appear in Eq. (48), the groups in this equation that also contain these same variables could end up with different values for the exponents. 

In another study of the physical behavior of soap-LSDA blends, Weil and Linfield [35] showed that the mechanism of action of such mixtures is based on a close association between the two components. In deionized water this association is mixed micellar. Surface tension curves confirm the presence of mixed micelles in deionized water and show a combination of optimum surface active properties, such as low CMC, high surface concentration, and low surface concentration above the CMC. Solubilization of high Krafft point soap by an LSDA and of a difficulty soluble LSDA by soap are related results of this association. Analysis of dispersions of soap-LSDA mixtures in hard water shows that the dispersed particles are mixtures of soap and LSDA in the same proportion as they were originally added. These findings are inconsistent with the view that soap reacts separately with hard water ions and that the resulting lime soap is suspended by surface adsorption of LSDA. The suspended particles are responsible for surface-active properties and detergency and do not permit deposits on washed fabric unlike those found after washing with soap alone. 

Aqueous standard solutions are a source of certain difficulties In electrothermal atomic absorption spectrometry of trace metals In biological fluids The viscosities and surface tensions of aqueous standard solutions are substantially less than the viscosities and surface tensions of serum, blood and other proteln-contalnlng fluids These factors Introduce volumetric disparities In pipetting of standard solutions and body fluids, and also cause differences In penetration of these liquids Into porous graphite tubes or rods Preliminary treatment of porous graphite with xylene may help to minimize the differences of liquid penetration (53,67) A more satisfactory solution of this problem Is preparation of standards In aqueous solutions of metal-free dextran (50-60 g/llter), as first proposed by Pekarek et al ( ) for the standardization of serum chromium analyses This practice has been used successfully by the present author for standardization of analyses of serum nickel The standard solutions which are prepared In aqueous dextran resemble serum In regard to viscosity and surface tension Introduction of dextran-contalnlng standard solutions Is an Important contribution to electrothermal atomic absorption analysis of trace metals In body fluids. 

The appreciation of the importance of adsorption phenomena at liquid interfaces is probably as old as human history, since it is easily recognized in many facets of everyday life. It is not surprising that liquid interfaces have been a favorite subject of scientific interest since as early as the eighteenth century [3,4], From an experimental point of view, one obvious virtue of the liquid interfaces for studying adsorption phenomena is that we can use surface tension or interfacial tension for thermodynamic analysis of the surface properties. The interfacial tension is related to the adsorbed amount of surface active substances through the Gibbs adsorption equation. 

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