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Defoamers, anti-foam and air-release agents

A defoamer or an anti-foaming agent is a chemical additive that reduces and hinders the formation of foam in industrial process liquids. Commonly used agents are insoluble oils, polydimethylsiloxanes and other silicones, certain alcohols, stearates and glycols. The additive is used to prevent formation of foam or is added to break a foam already formed. We can make a distinction between macro- and micro-foam. Macro-foam is often formed at the surface of the coating and micro-foam is entrapment of air bubbles what is not able to rise fast enough to the surface. For micro foam you need a so-called air release agent to coagulate the micro bubbles to bugger air bubbles so they can rise faster to the surface to be destroyed. In industrial processes, foams pose serious problems. They cause defects on surface coatings. They prevent the efficient filling of containers. A variety of chemical formulae are available to prevent formation of foams. Properties: Generally a defoamer is insoluble in the foaming medium and has surface active properties. An essential feature of a defoamer product is a low viscosity and a facility to spread rapidly on foamy surfaces. It has affinity to the air-liquid surface where it destabilizes the foam lamellas. This causes rupture of the air bubbles and breakdown of surface foam. Entrapped air bubbles are agglomerated, and the larger bubbles rise to the surface of the bulk liquid more quickly.