Emulsions and surfactants

Fluid colloidal system of two or more components. (Gold Book online, 1972 entry [2].) Note Examples of colloidal sols are protein sols, gold sols, emulsions and surfactant solutions above their critical micelle concentrations. 

Gluadin AGP Partial wheat protein hydrolysate (Hydrolysed Wheat Protein and Hydrolysed Wheat Gluten) min. 94 Active ingredient, care and protective additive. Emulsions and surfactant preparations... 

Gluadin Almond Partial protein hydrolysate from almond (Hydrolysed Sweet Almond Protein) ca 20 Active ingredient, additive. Emulsions and surfactant preparations, additive for alcoholic/ aqueous preparations... 

Whether an emulsion is 0/W or W/0 depends on a number of variables like oihwater ratio, electrolyte concentration, temperature, etc. For most of this centiuy, emulsion chemists have known that surfactants more soluble in water tend to make 0/W emulsions and surfactants more soluble in oil tend to make W/0 emulsions. This is the essence of Bancroft s rule, which states that the continuous phase of an emulsion tends to be the phase in which the emulsifier is preferentially soluble. The word soluble is misleading, however, for two reasons. Firstly, a surfactant may be more soluble in, say, oil than in water in a binary system, but in the ternary system of oil -I- water + surfactant it may partition more into water. A good example of this is with the anionic surfactant Aerosol OT (sodium bis-2-ethylhexylsulfosuccinate) which dissolves in heptane at 25 C up to at least 0.5 m but has a solubility limit in water of only 0.03 M. An emulsion made from equal volumes of water and heptane at 25 °C is 0/W, however. Secondly, no distinction is made between the solubility of monomeric or aggregated surfactant in oil or water. We will see that this is an important omission. 

Uses Pearlescent, opacifier for emulsions and surfactant preps., shampoos, body cleaners, hand dishwashing detergents, rinses, cosmetics and creams Properties Flake HLB 1 100% solids Ablunol EGMS [Taiwan Surf ]... 

M. Ueno, K. Shioya, T. Nakamura, and K. Meguro, in Colloid and Interface Science, Vol. II, p. 411. Aerosols, Emulsions, and Surfactants, ed., M. Kerker, International Conference on Colloids and Surfaces, San Juan, Puerto Rico, Academic Press, Inc., New York (1976). 

In the building industry, emulsifiers are widely used for the preparation of bitumen emulsions, and surfactants are used in the production of foamed concretes. Concrete emulsions contain high proportions of paraffins or mineral oils. The boards or plates required in forming are prepared using this emulsion, and they are then less sensitive to dirt and are more readily released [44]. In the chemical industry, in turn, surfactants are frequently added for reasons of reaction kinetics, in order to enlarge the interfaces of the substances which are not miscible with one another [45]. 

One may rationalize emulsion type in terms of interfacial tensions. Bancroft [20] and later Clowes [21] proposed that the interfacial film of emulsion-stabilizing surfactant be regarded as duplex in nature, so that an inner and an outer interfacial tension could be discussed. On this basis, the type of emulsion formed (W/O vs. O/W) should be such that the inner surface is the one of higher surface tension. Thus sodium and other alkali metal soaps tend to stabilize O/W emulsions, and the explanation would be that, being more water- than oil-soluble, the film-water interfacial tension should be lower than the film-oil one. Conversely, with the relatively more oil-soluble metal soaps, the reverse should be true, and they should stabilize W/O emulsions, as in fact they do. An alternative statement, known as Bancroft s rule, is that the external phase will be that in which the emulsifying agent is the more soluble [20]. A related approach is discussed in Section XIV-5. 

Many different combinations of surfactant and protective coUoid are used in emulsion polymerizations of vinyl acetate as stabilizers. The properties of the emulsion and the polymeric film depend to a large extent on the identity and quantity of the stabilizers. The choice of stabilizer affects the mean and distribution of particle size which affects the rheology and film formation. The stabilizer system also impacts the stabiUty of the emulsion to mechanical shear, temperature change, and compounding. Characteristics of the coalesced resin affected by the stabilizer include tack, smoothness, opacity, water resistance, and film strength (41,42). 

Asphalt emulsions are dispersioas of asphalt ia water that are stabilized iato micelles with either an anionic or cationic surfactant. To manufacture an emulsion, hot asphalt is mixed with water and surfactant ia a coUoid mill that produces very small particles of asphalt oa the order of 3 p.m. These small particles of asphalt are preveated from agglomerating iato larger particles by a coatiag of water that is held ia place by the surfactant. If the asphalt particles agglomerate, they could settle out of the emulsion. The decision on whether a cationic or anionic surfactant is used depends on the appHcation. Cationic stabilized emulsions are broken, ie, have the asphalt settle out, by contact with metal or siHcate materials as weU as by evaporation of the water. Siace most rocks are siHcate-based materials, cationic emulsions are commonly used for subbase stabilization and other similar appHcations. In contrast, anionic emulsions only set or break by water evaporation thus an anionic emulsion would be used to make a cold patch compound. 

It should be noted that Cypridina luciferin emits a fairly strong chemiluminescence in aqueous solutions in the presence of various lipids and surfactants, even in the complete absence of luciferase. The luminescence is especially conspicuous with cationic surfactants (such as hexadecyltrimethylammonium bromide) and certain emulsion materials (such as egg yolk and mayonnaise). Certain metal ions (especially Fe2+) and peroxides can also cause luminescence of the luciferin. Therefore, great care must be taken in the detection of Cypridina luciferase in biological samples with Cypridina luciferin. 

Some detergents and surfactants are used as emulsifying agents. An emulsifier keeps oil droplets and water droplets from joining together, so a thick mixture of oil and water will not separate. Examples of emulsions are mayonnaise, butter, cream, homogenized milk, and salad dressings. 

Fig. 18. Comparison of results from various particle systems for stirred vessel with baffles and bubble columns Activity a/ao of Acylase resin after t = 300 h, equilibrium drop diameter dg of silicon oil-water-surfactant emulsion and reference floe diameter dpv of floe system in dependency on specific power P/V H/D = 1 D = 0.15 m 0.4 m...

Drain the aqueous acetonitrile (lower) phase into a 500-mL round-bottom flask, and save the separatory funnel for extraction. Extract the hexane-fat mixture by transferring the mixture back to the polypropylene centrifuge bottle and adding 100 mL of acetonitrile-water (4 1, v/v) solution. Balance the duplicate centrifuge bottles, and cap and shake the bottles for 10 min on the shaker. Centrifuge the second extract at 11 000 rpm for 15 min. Decant this second extract into the 250-mL separatory funnel as before. After phase separation, combine the aqueous extracts in the 500-mL round-bottom flask, and discard the top hexane-fat layer. Add 10 drops of Dow Coming Antifoam B emulsion and 3 mL of 10% aqueous Igepal CO-660 (nonionic surfactant) to the flask. 

Milk. Shake the sample vigorously, and immediately weigh 25 g of milk into a 500-mL round-bottom Aask. Add 10 drops of Dow Corning Antifoam B emulsion and 3 mL of 10% aqueous Igepal CO-660 (nonionic surfactant) to the Aask. Fortify the sample in the Aask. 

Emulsions and Emulsion Technology (in three parts), edited by Kenneth J. Lissant Anionic Surfactants (in two parts), edited by Warner M. Linfieid see Volume 56) Anionic Surfactants Chemical Analysis, edited by John Cross Stabilization of Colloidal Dispersions by Polymer Adsorption, Tatsuo Sato and Richard Ruch... 

ThF Tadros. Polymeric surfactants , stabilization of emulsions and dispersions. In E Desmond Goddard, JV Gruber, eds. Principles of Polymer Science and Technology in Cosmetics and Personal Care. New York Marcel Dekker, 1999, pp 73-112. 

A surfactant is a surface-active agent that is used to disperse a water-insoluble drug as a colloidal dispersion. Surfactants are used for wetting and to prevent crystal growth in a suspension. Surfactants are used quite extensively in parenteral suspensions for wetting powders and to provide acceptable syringability. They are also used in emulsions and for solubilizing steroids and fat-soluble vitamins. 

The anhydrous petrolatum base may be made more miscible with water through the use of an anhydrous liquid lanolin derivative. Drugs can be incorporated into such a base in aqueous solution if desired. Poly-oxyl 40 stearate and polyethylene glycol 300 are used in an anti-infective ointment to solubilize the active principle in the base so that the ointment can be sterilized by aseptic filtration. The cosmetic-type bases, such as the oil-in-water (o/w) emulsion bases popular in dermatology, should not be used in the eye, nor should liquid emulsions, owing to the ocular irritation produced by the soaps and surfactants used to form the emulsion. 

Surfactants are used to stabilize water-in-oil emulsions and to promote rapid return of injected fluids and a faster return of the well to hydrocarbon production. Although they are expensive, water-soluble fluorochemicals have been shown to be effective in this application (97,98). 

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