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A defoamer is an additive that eliminates foam when making, applying, or storing paint. Foam is a difficult problem for formulators that can cause unsightly defects and expensive manufacturing processes. Defects can impact surface appearance, gloss, and adhesion. Entrained air can contribute to foam formation that negatively impacts efficiency in applications like industrial operations.

Modified polydimethylsiloxane (PDMS) and non-silicone solutions from Borchers act as foam control agents for coatings. They help prevent the formation of foam or eliminate existing foam during the production and application of coatings.

 

Why Are Defoamers Important?

Foam Formation in Liquids

Foam forms from entrapped gas in a liquid or solid medium. Macrofoam forms at the surface of a coating while microfoam consists of small air bubbles entrapped within a coating. When a liquid is pure, such as pure water or any liquid without surfactants, it does not generate foam. However, paints are not pure liquids as they contain surface-active substances.

 

Foam generation is more stable in surfactant-containing systems like coatings

 

Causes of Foam Formation in Coatings

Many essential processes throughout the formulation of a coating can result in foam generation.  Defoamers for coatings can help avoid foam-related defects caused by the following processes:

• In the production phase, the grinding or milling of pigments as well as filling paint into cans may cause foaming.
• During the application phase, foam can form when spraying, brushing, or rolling paint onto a substrate.
• Challenging substrates like wood or concrete can also contribute to foam formation.

Foaming can occur at any time and cause less-than-ideal results. Uneven surfaces, reduced gloss, and poor adhesion between the coating and a surface can all result from foam formation. Pinholes, craters, and poor leveling are a few examples of foam-related surface defects.

Defoaming agents work to reduce surface tension in coatings, making foam unstable. This causes the bubble wall in a coating to thin out and eventually burst, releasing air. As a result, foam-related defects are prevented.

 

The mechanism of foam destruction with foam control paint additives

 

 

Borchers AF 1171 foam control agent prevented pinholes in a solvent-free urethane modified medium oil alkyd emulsion formulation by controlling foam formation

 

Types of Defoamers for Paint

Additive manufacturers typically offer mineral oil, silicone-based (PDMS), and silicone-free foam prevention solutions.

 

Mineral Oil

Mineral oil solutions are popular cost-effective additives that may contain wax or silica to boost performance.

Examples include:

• Borchi Burst DFM 100 for waterborne PVC systems as well as some low gloss paints, paper coatings, and plasters.
• Borchi Burst DFM 200 for waterborne PVC paints, automotive spray booth effluent systems, and adhesives.

 

Silicone-Based (PDMS)

Silicone (or PDMS) additives provide excellent long-term defoaming efficiency, broader application, and lower surface tension. They have good chemical inertness and thermal stability and have no impact on gloss or color acceptance.

Examples include:

• Borchers AF 1171 for waterborne and solventborne decorative and general industrial coatings.

 

Silicone-Free

Silicone-free additives contain polymers with very low surface tension. They are easy to incorporate, result in defect-free films, and do not cause color-related issues. These solutions are also low in VOCs and are efficient for use at low surface levels.

Examples include:

• Borchers AF T for waterborne and solventborne coatings and adhesives.
• Borchi Burst DF 300 for waterborne gloss paints, wood coatings, pigment dispersions, and matt and silk paints.

 

How to Select and Evaluate Defoamers from Borchers

Selecting the right foam prevention additive requires considering a coating’s criteria and conducting tests.

 

Selecting Defoamers

Finding the best defoaming additive first involves making note of the content within a formulation.

 

Type of System

Certain defoamers will work better in solventborne formulations and others will work better in waterborne formulations. Some may work well in both.

 

Stage of Production

Understanding the stage of production in which foam-related defects occur also helps narrow down selections. Manufacturers create some additives for the mill base stage, some for the letdown stage, and some for use in various stages.

 

Resin System

Only certain defoamers will be compatible with the resin used in a coating formulation. Options are available for a wide range of resins, including alkyd, acrylic, epoxy, and polyurethane.

 

Formulation

Whether or not a coating is high gloss, semi-gloss, matte, or high solids can all have an effect. Determining if a formulation is silicone-free or already contains a defoamer is also important. The fillers used in a coating are also essential to consider.

 

Application

Foam generation can occur during the brushing, rolling, or spraying of a coating on a substrate. Knowing under which application method foam typically forms in a coating is important.

 

Current Issues

The particular issues taking place in a coating will have a strong impact on the type of defoamer to select.

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A comprehensive foam control offering includes a range of custom defoaming solutions and foam control products to meet the needs of various industries. Borchers’ defoamer selection guide helps narrow down options by specific formulation criteria. Our technical service team can also recommend certain additives based on your formulation content.

Popular Borchers brand defoamers are listed below:

 

Evaluating Defoamers

The Borchers’ team can test defoamer performance in your systems after defining criteria and narrowing down options. These include tests for compatibility, reciprocal of density, and application.

 

 

Borchers’ technical service team has conducted these tests in a variety of formulations, including:

• Waterborne Acrylic Semigloss Architectural Coatings
• Waterborne Polyurethane Clearcoat for Flooring / Clear Varnish for Cabinetry
• Waterborne Styrene-Acrylic Copolymer Latex for Direct-to-Metal Coatings

To check out these case studies, download our short defoamer webinar.

 

Other Foam Control Agents

Other foam control products include deaerators, which allow air bubbles to escape more easily before application. Deaerators also improve substrate wetting and are ideal for coatings used on thin layers and porous surfaces. Anti-foaming agents work to prevent foam formation.

 

Borchers offers a wide range of deaerators, defoamers, and antifoam agents.

 

Contact Borchers for Superior Defoamers Today

Foam can form in various stages throughout the coating formulation process, which can result in defects. Borchers has many defoamers for coating systems that you can test for compatibility.

 

Visit our defoamer product page for information on our full product range.