Emulsifier mixtures

The phase-inversion temperature (PIT) is defined as the temperature where, on heating, an oil—water—emulsifier mixture inverts from O/W to a W/O emulsion [23]. The PIT correlates very well with the HLB as illustrated in Fig. XIV-10 [72, 73]. The PIT can thus be used as a guide in emulsifier selection. 

By polymerising an emulsified mixture of butadiene and styrene (ca. 25 per cent.) Buna S or OBS rubber is produced ... 

T. Forster, W. Von Rybinski, H. Tesmann, and A. Wadle Calculation of Optimum Emulsifier Mixtures for Phase Inversion Emulsification. Int. J. Cosmet. Sci. 16, 84... 

We have tested this hypothesis in some recent o/w thin film experiments [45]. It was not practical to reduce the protein load per unit area of interface to that found in the emulsion experiments, since the very low concentrations required would have been very slow to reach equilibrium adsorption. We circumvented this problem in a unique way. Rather than adsorb emulsifier mixtures from aqueous solution, we formed the oil droplets and the thin film in a preformed emulsion. Therefore, the adsorbed layers on the captive droplets formed by adsorption of surfactant from the continuous phase of the emulsion. The results are shown in Figure 23, where surface diffusion data of FITC-/8-lg in o/w and a/w thin films as a function of added Tween 20 are summarised. 

Eczema may be so mild that no treatment is required beyond avoiding known irritants and applying a soothing and protective ointment which keeps the skin moist and so reduces inflammation. There are many such over-the-counter remedies based on liquid paraffin and soft white paraffin, both of which are hydrocarbons obtained from refined petroleum and which contain nothing that can irritate the skin. Liquid paraffin is also called mineral oil and is available under a variety of trade names, such as Nujol, while soft white paraffin is better known as Vaseline. Emulsified mixtures of liquid paraffin and soft white paraffin make excellent skin creams. 

Newton, M., Petersson, J., Podczeck, F., Clarke, A., and Booth, S. (2001), The influence of formulation variables on the properties of pellets containing a self-emulsifying mixture,/. Pharm. Sci., 90, 987-995. 

Experiments with benzoyl peroxide show that with the oil-soluble initiator, initiation takes dace solely in the monomer droplets under the same conditions as in Fig. 9. No minimum in the curves is encountered as the degree of homogenization of the monomer-water-emulsifier mixture is reduced. 

The appropriate choice of emulsifier or emulsifier mixture can be made by preparing a series of emulsions with a range of surfactants of varying HLB. It is assumed that the HLB of a mixture of two surfactants containing frachon f of A and (1 - f) of B is the algebraic mean of the two HLB numbers ... 

Microemulsions consist of apparently homogeneous transparent systems of low viscosity which contain a high percentage of both oil and water and high concentrations (15-25%) of emulsifier mixture. They were first described by Schulman as disperse systems with spherical or cylindrical droplets in the size range 8-80 nm. They are essentially swollen micellar systems, but obviously the distinction between a swollen micelle and small emulsion droplet is difficult to assess. 

Stable o/w creams prepared with ionic or nonionic emulsifying waxes are composed of (at least) four phases (Fig. 7.20) (f) dispersed oil phase, (2) crystalline gel phase, (3) crystalline hydrate phase, and (4) bulk aqueous phase containing a dilute solution of surfactant. The interaction of the surfactant and fatty alcohol components of emulsifying mixtures to form these stmctures (body) is critical. It is also time-dependent, giving the name self-bodying to these emulsions. The overall stability of a cream is dependent on the stability of the crystalline gel phase. 

Many different preparations of colloidal barium sulfate for roentgenography are available commercially. The so-called barium meals are not limited to liquid suspensions they also appear as tablets (73). Barium sulfate suspensions containing an effervescent agent have been introduced for use in doublecontrast studies (74,75). Barium sulfate may also be coated with Fe203, MgO, and Al Oa (63,761. The coated material has good dispersibility and very low viscosity in acidic media. Other barium preparations are also useful. A barium titanate suspension was compared with barium sulfate (72). An emulsified mixture containing castor oil and barium sulfate can visualize colon fistula more economically than can iodinated contrast media (77). 

Place about 10 mL of the emulsified mixture (above the bottom few drops) into each of five, 50 mL beakers. 

In the commercial alkylation of isobiitane with the butylenes, temperatures between 0 and 10° are employed because catalyst life is increased with a decrease in temperature. The strength of the makeup acid is 98-100%. Temperatures below 0° are not used because the emulsified mixture of catalyst and hydrocarbons becomes too stiff to flow readily. 

Fig. 6.7 Interfacial tension y (a) and mean droplet diameter d (b), of a decane in water emulsions as a function of the HLB of the emulsifier mixture Span 80/Tween 80 (total 0.5 wt%)...

No explanation has been offered as to why particular emulsifier mixtures produce monodisperse latexes. Latexes produced by emulsifier-ffee emulsion polymerization are monodisperse (although comparatively large in size). Hence it may be inferred that the coalescence rate should be at a maximum for minimal polydispersity. The emulsifier mixture which produces a monodisperse latex is that which is least effective in stabilizing the particles. 

Triangular Phase Diagrams (Gibbs, 1876). The solvent-emulsifier mixtures were then examined using triangular phase... 

At maximum speed the mixer produces shearing forces at such an extent that they emulsify mixtures of water and oil. Only the rotor-stator mixer generates a higher shear force in fluids. During mixing an appreciable rise in temperature will occur, especially at higher speeds. If a mantle is available the contents of the bowl can be heated or cooled. The application of vacuum is relevant if air must be prevented from being whipped into the mixture. 

Various methods have been used to dehydrate the esterification reaction mixture and promote reaction. Azeotropic distillation is usually involved. Once the mixture is anhydrous it is often heated under superatmospheric presure to accelerate the reaction. Water may be removed from the system with a molecular sieve (457). The silica may be in an emulsified mixture of water and immiscible solvent such as mineral oil and cetyl-oleyl glycol ether and an emulsifying agent. This is dehydrated in a climbing-film evaporator (458). Water can be removed by reaction with a ketal according to Ryznar (459). 

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