Term: Defoamer
**Defoamer Properties**:
– Defoamer is insoluble in the foaming medium and has surface active properties.
– It has low viscosity and spreads rapidly on foamy surfaces.
– Defoamer destabilizes foam lamellas on air-liquid surfaces.
– It causes rupture of air bubbles and breakdown of surface foam.
– Entrained air bubbles are agglomerated, and larger bubbles rise quickly to the liquid surface.
**History of Defoamers**:
– Early defoamers used kerosene, fuel oil, and vegetable oils.
– Fatty alcohols were effective but expensive antifoams.
– Silicone-based defoamers were experimented with in the 1950s.
– Hydrophobic particles in light oil were patented in 1963.
– Water-based and water-extended defoamers emerged due to the oil crisis in 1973.
**Classification of Defoamers**:
– Oil-based defoamers: Have an oil carrier, such as mineral or vegetable oil, and are best at reducing surface foam.
– Powder defoamers: Are oil-based defoamers on a particulate carrier like silica, used in powdered products to reduce foam.
– Water-based defoamers: Contain oils and waxes dispersed in a water base, best at releasing entrained air.
– Silicone-based defoamers: Are polymers with silicon backbones, good at reducing surface foam and releasing entrained air.
– Alkyl polyacrylates: Suitable for use as defoamers in non-aqueous systems, focusing on air release rather than surface foam breakdown.
**Industrial Problems and Applications**:
– Industrial problems caused by foam include liquid level issues, process speed reduction, and equipment availability.
– Testing defoamers can be done by observing surface foam, testing entrained air, and drainage time through a filter.
– Applications of defoamers include detergents, food preparation, industrial processes, and more.
**Foam and Foaming Agents**:
– Foam is a substance formed by trapping pockets of gas in a liquid or solid.
– Foaming agents help produce foam in various industries.
– Understanding the chemistry of foams is crucial for controlling their formation.
– References for further reading on foams and foam control are provided.
– The importance of defoamers and antifoams in different industries is highlighted.
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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. Strictly speaking, defoamers eliminate existing foam and anti-foamers prevent the formation of further foam. 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.