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Fascinating Silicone™ Chemistry Corner – Antifoams and Defoamers

How silicone defoamers work
 

Silicone antifoams prevent foam from forming. Silicone defoamers cause existing foam to rapidly collapse. The generic term "antifoam" is often used to describe both types of foam-control products.

Foam is difficult to break down because it is stabilized by the surface elasticity and surface viscosity of its film. Silicones have low surface and interfacial tensions. This enables them to flow easily over the film. They seek out openings between the foam-stabilizing surfactants at the liquid-air interface and occupy them. Silicones’ low surface tension and interfacial properties combined with their lack of foam-stabilization properties cause the foam wall to thin and collapse.

A single drop of silicone antifoam quickly destroys process foam


Controlling foam in nonaqueous vs. aqueous systems

For nonaqueous systems, invading the spaces between the foam-stabilizing surfactants is generally all that is required to collapse the foam. This can be accomplished by a simple silicone fluid, such as polydimethylsiloxane.

For aqueous systems, the addition of finely dispersed hydrophobic solids, such as polydimethylsiloxane-treated silica, is needed. These fluid/solid combinations are called antifoam compounds. The hydrophobic solids help break down the "pseudo-emulsion" film that forms between the antifoam droplet and the surface of the foaming solution. Antifoam compounds are often prepared as emulsions for easy dispersal in water-based systems.

Antifoam and defoaming benefits of silicone

  • Lower surface tension, compared to organic antifoams
  • Insoluble in most systems
  • Tends to react less with process ingredients
  • Persistence – generally performs longer
  • Can cost less to use due to its effectiveness and persistence at low use levels

Typical silicone antifoam and defoamer applications

Foam reduces processing speed and capacity. It limits the cleaning capability of detergents, limits formulations, and can lead to environmental concerns. Silicone antifoams effectively control process foam in many different processes, including:

Learn how other types of silicones work.

Did you know ... silicones not only destroy foam. They can also help stabilize it! Learn how silicone foam stabilizers work.

Expand your understanding

Silicone economics:
Why a silicone antifoam that costs more can actually cost less to use

Technical articles:
Silicones in the Food Industries (PDF size 105 KB)
Silicones in the Pulp and Paper Industry (PDF 59 size KB)
Silicones in the Textiles Industry (PDF 98 size KB)
Silicones in Household Cleaning Applications (PDF size 114 KB)
Silicones in Coatings (PDF size 285 KB)
Silicones in Medical Applications (PDF size 146 KB)

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