A defoamer or an anti-foaming agent info Chemical Man

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 and prevent the efficient filling of containers. A variety of chemical formulae are available to prevent formation of foams.

Applications

Detergents

Anti-foams are added in certain types of detergents to reduce foaming that might decrease the action of the detergent. For example, dishwasher detergents have to be low foaming for the dishwasher to work properly.
Food

When used as an ingredient in food, antifoaming agents are intended to curb effusion or effervescence in preparation or serving.The agents are included in a variety of foods such as chicken nuggets in the form of polydimethylsiloxane (a type of silicone).

Silicone oil is also added to cooking oil to prevent foaming in deep-frying

Industrial use

Defoamers are used in many industrial processes and products: wood pulp, paper, paint, industrial wastewater treatment, food processing, oil drilling, machine tool industry, oils cutting tools, hydraulics, etc.

Pharmaceuticals

Antifoaming agents are also sold commercially to relieve bloating. A familiar example is the drug Simethicone, which is the active ingredient in drugs such as Maalox, Mylanta, and Gas-X.

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.