Influencing Factors and Selection of Antifoam in Coating Formulations

Mar 06, 2024

Factor 1: Surface tension

The surface tension of the coating has a greater impact on the antifoam. The surface tension of the antifoam must be lower than the surface tension of the coating; otherwise, it cannot have the effect of defoaming and foam inhibition. The surface tension of the coating is a variable factor, so the choice of antifoam should be constant surface tension, and then the surface tension change factor will be taken into account.


Factor 2: The influence of other additives

Most of the surfactants used in coatings tend to be functionally incompatible with antifoams, especially emulsifiers, wetting and dispersing agents, leveling agents, thickeners, etc., which will have an impact on the effect of antifoams. Therefore, when various additives are combined, we must pay attention to the relationship between different additives and choose the best balance.


Factor 3: Baking temperature

When the paint enters high-temperature baking at room temperature, the viscosity will drop instantly, and the bubbles can move to the surface. However, due to the volatilization of the solvent, the curing of the paint, and the increase in surface viscosity, the bubble will be more stable and trapped on the surface, producing shrinkage and pinholes. So baking temperature, curing speed, and solvent evaporation rate also have an effect on the effect of antifoam.



Factor 4: Solid content, viscosity and elasticity of the coating

High-solids, thick coating films, high viscosity, and high-elasticity coatings are very difficult to define. In these coatings, there are many unfavorable defoaming factors, such as difficult diffusion of antifoam, slow change of micro bubble to large bubble, reduced migration ability of bubble to the surface, and large viscoelasticity of bubble. These coatings in foam are quite difficult to eliminate, so the best choice is to use an antifoam agent and a defoaming agent together.


Factor 5: Painting method and construction temperature

There are many coating construction methods, such as brushing, roller coating, dripping, scraping, spraying, screen printing, and so on. The coating methods used are different, and the degree of coating foam is also different. Brushing and roller coating will produce more foam than spraying and scraping. High temperatures produce more foam than low temperatures, but the foam is easier to eliminate when the temperature is high.

Selection of antifoam for different applications

Flat Coating

Formulation characteristics: Low viscosity, low defoaming pressure

Recommendation: mineral oil or mineral oil-modified polyether antifoam


Elasticity-class coating

Formulation characteristics: high viscosity, high defoaming pressure

Recommendation: polyether-modified silicone antifoam


Top coat and laminating adhesive

Recommendation: polyether antifoam, which can effectively prevent surface defects and has less effect on gloss


Water-in-water, colorful coating

Formulation characteristics: more surfactants, stable foam

Recommendation: polyether or mineral oil-modified polyether antifoam

Precautions for the use of antifoam

1. Must be fully stirred and mixed well before use;

2. Add in the case of paint stirring.

3. Usually, do not add water to dilute before use.

4. The amount should be appropriate. Too much dosage will cause shrinkage, poor brushability, and other problems; too little dosage will lead to a poor defoaming effect.

It is better to add it twice, respectively, in the grinding stage and the paint mixing stage. Usually half of the total amount each time. In the grinding stage, use the antifoam with a good foam inhibition effect, and in the paint mixing stage, use the antifoam with a good foam breaking effect.

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