Defoaming is the ability of a coating to eliminate the foam generated during the production and coating process. Defoamers are a type of additive used to reduce the foam generated during the production and/or application of coatings. So what factors affect the defoaming of coatings?

1. Surface tension
The surface tension of the coating has a great influence on the defoamer. The surface tension of the defoamer should be lower than that of the coating, otherwise it will not be able to defoam and inhibit foam. The surface tension of the coating is a variable factor, so when selecting a defoamer, both the constant surface tension and the surface tension variation of the system should be considered.

2. Other additives
Most surfactants used in coatings are functionally incompatible with defoamers. In particular, emulsifiers, wetting and dispersing agents, leveling agents, thickeners, etc. will affect the effect of defoamers. Therefore, when combining various additives, we must pay attention to the relationship between different additives and choose a good balance point.

3. Curing factors
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 foam in the paint will become more stable, thus being trapped on the surface, resulting in shrinkage holes and pinholes. Therefore, the baking temperature, curing speed, solvent volatilization rate, etc. also affect the defoaming effect.

4. Solid content, viscosity, and elasticity of coatings
High-solid thick coatings, high-viscosity coatings, and high-elasticity coatings are all very difficult to defoam. There are many factors that are not conducive to defoaming, such as the difficulty of defoamers to diffuse in these coatings, the slow rate of microbubbles turning into macrobubbles, the reduced ability of foams to migrate to the surface, and the high viscoelasticity of foams. The foam in these coatings is quite difficult to eliminate, and it is necessary to select defoamers and deaerators for use in combination.

5. Coating method and construction temperature
There are many coating application methods, including brushing, roller coating, pouring, scraping, spraying, screen printing, etc. The foaming degree of coatings using different coating methods is also different. Brushing and roller coating produce more foam than spraying and scraping. In addition, the construction environment with high temperature produces more foam than that with low temperature, but the foam is also easier to eliminate at high temperature.