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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.

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

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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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

Chemical manufacturing and formulating

Textiles

Food production and processing

Household cleaning

Pulp and paper manufacturing

Paints and coatings

Pharmaceuticals for healthcare

Open the silicone

toolbox for more

information.

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materials from Dow

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Fascinating Silicone™ Chemistry – How Silicone Antifoams & Defoame... http://www.dowcorning.com/content/discover/discoverchem/si-defoamer...

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Fascinating Silicone™ Chemistry – How Silicone Antifoams & Defoame... http://www.dowcorning.com/content/discover/discoverchem/si-defoamer...

2 of 2 5/4/2014 8:18 AM