Dispersion foam stability

Ethoxylan . [Henkel/Em /Cosidia] Edioxlyated lanolin emollient, enuilsi-fier, dispersant, foam stabilizer, resin plasticizer for cosmetics and pharmaceuticals. 

Uses Thickener, dispersant, foam stabilizer, coupling agent for emulsion polymerization, pesticides, petrol, prod., h vy-duty liq. detergents, adhesives, coatings, pharmaceutic s film-former in spray bandages complexing agent for sustained-release iron preps. ostomy adhesives denture adhesives/stabilizers dentifrices thickener for aq. or org. solv. sterns... 

Uses Thickener, dispersant, foam stabilizer, coupling agent for emulsion polymerization, pesticides, petrol, prod., heavy-duty liq. detergents, adhesives, coatings... 

Properties Nonionic Toxicology TSCA listed Uses Surfactant, emulsifier, emollient, dispersant, foam stabilizer, plasticizer for cosmetics (antiperspirants, creams, lotions, makeup, hair prods.), pharmaceutical vehicles, textile processing solvent, emollient, superfatting agent, conditioner for hair care, skin care, household detergents solubilizer wetting agent... 

Properties Nonionic Toxicoiogy TSCA listed Uses Surfactant, emulsifier, emollient, conditioner, humectant, wetting agent, dispersant, foam stabilizer, solubilizer, superfatting agent for cleaners, detergents, soaps, cosmetics, pharmaceuticals Trade Name Synonyms Brooksgel 61 f [Arch Personal Care Prods. 

Uses Wetting agent, detergent, emulsifier, dispersant, foam stabilizer solubilizer, penetrant for scouring and dye leveling in textiles, in cleaning and dishwashing compds., cosmetics and personal care applies. 

Uses Wetting agent, detergent, emuisifier, dispersant, foam stabilizer solubilizer,... 

Uses Surfactant blend for use as base for high-foaming bubble baths, liq. soaps hair conditioner permitting easy comb-out lime soap dispersant, foam stabilizer in presence of soap... 

Uses Emulsifier for emulsion polymerization and min. oils detergent, dispersant, foam stabilizer stable to pH and temp. 

Chemically, the preparation of a "stable" foam or emulsion requires the use of a surfactant to aid in dispersion of the internal phase and prevent the collapse of the foam (or emulsion) into separate bulk phases. The selection of a surfactant is made on the basis of severity of conditions to be encountered, the gas to be entrained (N2, C02, LPG, CH, or air), the continuous phase liquid (water, alcohol, or oil), and half-life of foam stability desired. 

As is known, if one blows air bubbles in pure water, no foam is formed. On the other hand, if a detergent or protein (amphiphile) is present in the system, adsorbed surfactant molecules at the interface produce foam or soap bubble. Foam can be characterized as a coarse dispersion of a gas in a liquid, where the gas is the major phase volume. The foam, or the lamina of liquid, will tend to contract due to its surface tension, and a low surface tension would thus be expected to be a necessary requirement for good foam-forming property. Furthermore, in order to be able to stabilize the lamina, it should be able to maintain slight differences of tension in its different regions. Therefore, it is also clear that a pure liquid, which has constant surface tension, cannot meet this requirement. The stability of such foams or bubbles has been related to monomolecular film structures and stability. For instance, foam stability has been shown to be related to surface elasticity or surface viscosity, qs, besides other interfacial forces. 

The first two components are the active surfactants, whereas the other components are added for a variety of reasons. The polyphosphate chelate Ca ions which are present (with Mg ions also) in so-called hard waters and prevents them from coagulating the anionic surfactants. Zeolite powders are often used to replace phosphate because of their nutrient properties in river systems. Sodium silicate is added as a corrosion inhibitor for washing machines and also increases the pH. The pH is maintained at about 10 by the sodium carbonate. At lower pH values the acid form of the surfactants are produced and in most cases these are either insoluble or much less soluble than the sodium salt. Sodium sulphate is added to prevent caking and ensures free-flowing powder. The cellulose acts as a protective hydrophilic sheath around dispersed dirt particles and prevents re-deposition on the fabric. Foam stabilizers (non-ionic surfactants) are sometimes added to give a... 

Additives had substantial effects on the aeration properties of bromelain-modified succinylated fish protein (50). Foam volume was increased with up to 2% sodium chloride in the system however there was a decrease in foam stability when greater than 0.3% salt was used. Sucrose, at concentrations up to 50%, increased foam stability. When fat was added to treated fish protein dispersions... 

A foam is a colloidal dispersion in which a gas is dispersed in a continuous liquid phase. The dispersed phase is sometimes referred to as the internal (disperse) phase, and the continuous phase as the external phase. Despite the fact that the bubbles in persistent foams are polyhedral and not spherical, it is nevertheless conventional to refer to the diameters of gas bubbles in foams as if they were spherical. In practical occurrences of foams, the bubble sizes usually exceed the classical size limit given above, as may the thin liquid film thicknesses. In fact, foam bubbles usually have diameters greater than 10 pm and may be larger than 1000 pm. Foam stability is not necessarily a function of drop size, although there may be an optimum size for an individual foam type. It is common but almost always inappropriate to characterize a foam in terms of a given bubble size since there is inevitably a size distribution. This is usually represented by a histogram of sizes, or, if there are sufficient data, a distribution function. 

The role of surfactants in stabilization/destabilization of foam (air/liquid dispersions) is similar to that for emulsions. This is due to the fact that foam stability/instability is determined by the surface forces operative in liquid films between air bubbles. In many industrial applications, it is essential to stabilize foams against collapse, e.g., with many food products, foam in beer, fire-fighting foam, and polyurethane foams that are used for furniture and insulation. In other applications, it is essential to have an effective way of breaking the foam, e.g., in distillation... 

The stabilizing function of macromolecular surfactants in solid-liquid systems is exercised through protective colloid action. To be effective, they must have a strong solution affinity for hydrophobic and hydrophilic entities. In liquid-liquid systems, surfactants are more accurately called emulsifiers. The same stabilizing function is exercised in gas-liquid disperse systems where the surfactants are called foam stabilizers. 

Three polysaccharide-water interfaces are shown in Fig. 1. The agarose interface is observed to be indifferent to water (Hayashi and Kanzaki, 1987), judging from its distinctly sharp, hydrophobic boundary. The methylcellu-lose and pectin boundaries are diffuse and clearly hydrophilic. The air bubbles on methylcellulose attest to its efficacy as a foam stabilizer. The interfaces depicted in Fig. 1 can be visualized on a macromolecular scale as the interfaces between dispersed polysaccharide molecules and water. 

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