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defoamer
A defoamer or an anti-foaming agent is a chemical additive that reduces and hinders the formation of foam in industrial process liquids. The terms anti-foam agent and defoamer are often used interchangeably. 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.
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.〔Rainer Höfer, Franz Jost, Milan J. Schwuger, Rolf Scharf, Jürgen Geke, Josef Kresse, Herbert Lingmann, Rudolf Veitenhansl and Werner Erwied "Foams and Foam Control" Ullmann's Encyclopedia of Industrial Chemistry, 2000, Wiley-VCH, Weinheim. 〕
==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. Entrained air bubbles are agglomerated, and the larger bubbles rise to the surface of the bulk liquid more quickly.〔(【引用サイトリンク】 author = Martin Hubbe, NC State University )〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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