Surfactants in foams

Foam is a disperse system, consisting of gas bubbles separated by liquid layers. Because of the significant density difference between the gas bubbles and the medium, the system quickly separates into two layers with the gas bubbles rising to the top, which may undergo deformation to form polyhedral structures. This is discussed in detail below. 

Pure liquids cannot foam unless a surface active material is present. When a gas bubble is introduced below the surface of a liquid, it bursts almost immediately as a soon as the liquid has drained away. With dilute surfactant solutions, as the liquid/ air interface expands and the equilibrium at the surface is disturbed, a resorting force is set up that tries to establish the equilibrium. 

Several surface active foaming materials may be distinguished - surfactants ionic, nonionic and 2witterionic, polymers (polymeric surfactants), particles that accumulate at the air/solution interface, and specifically adsorbed cations or anions from inorganic salts. 

Many of the above substances can cause foaming at extremely low concentrations (as low as 10 mol dm ). 

In kinetic terms, foams may be classified into (1) unstable, transient foams (lifetime of seconds) and (2) metastable, permanent foams (lifetimes of hours or days). 

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Surfactants in foam forma tionand foam destruction processes... 

Uses Emulsifier in cosmetics surfactant for drug delivery systems bioavailability enhancer, emulsifier, solvent, solubilizer, excipient for pharmaceuticals primary surfactant for microemulsions superfatting agent, decreasing the detatting action of surfactants in foaming products such as shower gels, foam baths, shampoos Features Hydrophilic Manuf/Distrib. Variati Trade Names Labrasol L.A.S. 

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