Surfactants emulsion stabilization

Uses Surfactant, emulsion stabilizer, solubilizer, dispersant, wetting agent, antistat, penetrant, plasticizer, defoamer, demulsifier in the petrol., paints, paper, cement, inks, cosmetics, pharmaceutical, plastics, detergent, and metalworking industries rubber activator Features R series for low foaming applies. 

Toxicology May produce contact sensitivity TSCA listed Uses Detergent, thickener, emulsifier, foam booster/stabilizer, wetting agent, solubilizer for cosmetics, pharmaceutical topicals, industrial/ household cleaners, textiles, etc. thickener, conditioner, stabilizer in shampoos surfactant, emulsion stabilizer in cosmetics plastics anti-stat foods (delinting of cottonseed for prod, of cottonseed oil) byprods. for use in animal feeds in cellophane for food pkg. defoamer in food-contact paper/paperboard Features Mild... 

Uses Flocculant (water/effluent treatment) dispersant for calcium carbonate and metal oxides suspending agent scale control for water treatment antistat, hair fixative for setting lotions, conditioners, blow drying aid surfactant, emulsion stabilizer, film-fonner, vise, control agent in cosmetics in food-pkg. adhesives Features Strongly anionic... 

HMIS Health 1, Flammability 1, Reactivity 0 Uses Perfumery surfactants lubricant for plastics processing resins antifoam food additive intermediate in mfg. of food additives surfactant, emulsion stabilizer, emulsifier, emollient, stiffener, astringent in pharmaceuticals cosolvent emulsifier, thickener, emollient, emulsion stabilizer, opacifier, vise, control agent in cosmetics in food-pkg. adhesives in food-contact coatings defoamer in food-contact coatings and paper/paperboard in cellophane for food pkg. food-contact textiles... 

Uses Foam booster/stabilizer, thickener, emulsifier for cosmetics, pharmaceuticals, detergents/cleaners surfactant, emulsion stabilizer in cosmetics surfactant for dry fabric cleaners, carpet shampoos... 

Uses Film-former in cosmetics, hair care, skin care thickener surfactant emulsion stabilizer Features Nontacky substantive to skin and hair Trade Name Synonyms Amercell Polymer HM-1500 t[Amerchol http //www.dow.com] Nonoxynol iodine CAS 11096-42-7 (generic)... 

Uses Low foam surfactant, emulsion stabilizer, dispersant, wetting agent, antistat for rigid PVC, vise, control agent... 

Uses Surfactant, emulsion stabilizer, hydrotrope, and cleanser in cosmetics thickener, detergent, foaming agent for low-irritation shampoos, liq. detergents Manuf/Distrib. Nanjing Chemlin Somerset Cosmetic Co. 

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. 

The inverse emulsion form is made by emulsifying an aqueous monomer solution in a light hydrocarbon oil to form an oil-continuous emulsion stabilized by a surfactant system (21). This is polymerized to form an emulsion of aqueous polymer particle ranging in size from 1.0 to about 10 pm dispersed in oil. By addition of appropriate surfactants, the emulsion is made self-inverting, which means that when it is added to water with agitation, the oil is emulsified and the polymer goes into solution in a few minutes. Alternatively, a surfactant can be added to the water before addition of the inverse polymer emulsion (see Emulsions). 

Emulsions stabilized with a nonionic surfactant and catalyzed with a monomer soluble initiator were found to foUow kinetics dependent on initiator concentration (17). 

Polymers have so far been used comparatively less than the common surfactants to stabilize emulsions in spite of the fact that excellent stabilization by them can be achieved (18—20). AppHcation probably has been limited because the adsorption of polymers to emulsion droplets has displayed some intricate phenomena small changes in polymer stmcture or in solvent properties may lead to drastic changes in adsorption. 

Water-in-oil macroemulsions have been proposed as a method for producing viscous drive fluids that can maintain effective mobility control while displacing moderately viscous oils. For example, the use of water-in-oil and oil-in-water macroemulsions have been evaluated as drive fluids to improve oil recovery of viscous oils. Such emulsions have been created by addition of sodium hydroxide to acidic crude oils from Canada and Venezuela. In this study, the emulsions were stabilized by soap films created by saponification of acidic hydrocarbon components in the crude oil by sodium hydroxide. These soap films reduced the oil/water interfacial tension, acting as surfactants to stabilize the water-in-oil emulsion. It is well known, therefore, that the stability of such emulsions substantially depends on the use of sodium hydroxide (i.e., caustic) for producing a soap film to reduce the oil/water interfacial tension. 

A reduction in the electrical charge is known to increase the flocculation and coalescence rates. Sufficient high zeta potential (> — 30 mV) ensures a stable emulsion by causing repulsion of adjacent droplets. The selection of suitable surfactants can help to optimize droplet surface charges and thus enhance emulsion stability. Lipid particles with either positive or negative surface charges are more stable and are cleared from the bloodstream more rapidly than those with neutral charge [192, 193]. 

B Lundberg. Preparation of drug-carrier emulsions stabilized with phosphatidylcholine-surfactant mixtures. J Pharm Sci 83(1) 72—75, 1994. 

Y Sela, S Magdassi, N Garti. Release of markers from the inner water phase of W/O/W emulsions stabilized by silicone based polymeric surfactants. J Control Release 33(1) 1-12, 1995. 

N Garti, A Aserin. Double emulsions stabilized by macromolecular surfactants. Advances in colloid and interfaces science 65 37-69, 1996. 

In emulsion polymerization, a solution of monomer in one solvent forms droplets, suspended in a second, immiscible solvent. We often employ surfactants to stabilize the droplets through the formation of micelles containing pure monomer or a monomer in solution. Micelles assemble when amphiphilic surfactant molecules (containing both a hydrophobic and hydrophilic end) organize at a phase boundary so that their hydrophilic portion interacts with the hydrophilic component of the emulsion, while their hydrophobic part interacts with the hydrophobic portion of the emulsion. Figure 2.14 illustrates a micellized emulsion structure. To start the polymerization reaction, a phase-specific initiator or catalyst diffuses into the core of the droplets, starting the polymerization. 

Surfactants such as sulfated fatty alcohols may be hydrated to a higher extent than the fatty alcohols alone and thus stabilize o/w emulsions. The eombination of an anionic and a nonionic srrrfactant has proved to be partieularly effeetive, sinee the electrostatic repulsion forces between the ionie surfaetant moleeules at the interface are reduced by the incorporation of nonionic molecules, thus improving the emulsion stability. The combination of cetyl/stearyl sulfate (Lanette E) and eetyl/ stearyl alcohol (Lanette 0) to yield an emulsifying eetyl/stearyl aleohol (Lanette N) is an example of this approach. The polar properties of this srrrfactant mixtrrre are dominant, and o/w creams are formed. In contrast to w/o systems, the stabilizing effect of the surfactant mixtirre is not mainly due to adsorption at the interfaee. Instead, the mixed surfactants are highly hydrated and fonn a lamellar network, whieh is... 

M.P. Aronson and H.M. Princen Contact Angles in OU-in-Water Emulsions Stabilized by Ionic Surfactants. Nature 286, 370 (1980). 

The first observation of depletion flocculation by surfactant micelles was reported by Aronson [3]. Bibette et al. [4] have studied the behavior of silicone-in-water emulsions stabilized by sodium dodecyl sulfate (SDS). They have exploited the attractive depletion interaction to size fractionate a crude polydisperse emulsion [5]. Because the surfactant volume fraction necessary to induce flocculation is always lower than 5%, the micelle osmotic pressure can be taken to be the ideal-gas value ... 

Many different types of interaction can induce reversible phase transitions. For instance, weak flocculation has been observed in emulsions stabilized by nonionic surfactants by increasing the temperature. It is well known that many nonionic surfactants dissolved in water undergo aphase separation above a critical temperature, an initially homogeneous surfactant solution separates into two micellar phases of different composition. This demixtion is generally termed as cloud point transition. Identically, oil droplets covered by the same surfactants molecules become attractive within the same temperature range and undergo a reversible fluid-solid phase separation [9]. 

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