What to Do About Foam in Solvent-Based Coatings During Application

Solvent-based coatings often go through high-speed dispersion, grinding and letdown in production. When the equipment runs fast, air is drawn into the liquid. Some large bubbles rise to the surface quickly, but fine bubbles stay in the coating and only show up during application or even after film formation.

Besides ordinary foam, some coatings may also pop or boil during spraying, baking or temperature change, leaving bubbles and similar defects on the film surface.

A defoamer is not better the more is added. If the additive and the resin system match poorly, the film surface can be affected and defects such as craters can occur. So a defoamer for solvent-based systems should be judged on three points: defoaming, air release and compatibility.

Foam and microbubbles are not the same state. Large bubbles seen in production usually break easily, while small bubbles can stay dispersed inside the coating and flow along with it into application.

After the coating is sprayed onto the workpiece, solvent begins to evaporate and the film thickens, so trapped bubbles escape more slowly. If they do not leave the film in time, pinholes and similar surface problems can form after drying.

So a defoamer should not be judged only by whether foam remains on the liquid surface after stirring. Air release inside the coating and the final film state must be checked too.

A defoamer is itself an interfacial additive. Once in the coating it has to work inside the system while keeping a suitable interaction with the resin, solvent and other additives.

If its compatibility with the formula is insufficient, local surface tension differences can arise during film formation, which raises the chance of craters. Defoaming effect and compatibility must be evaluated together, especially in high-gloss coatings and screen printing inks where appearance requirements are high; foam-breaking speed alone is not a sound basis.

DH-2022A is a fluorocarbon vinyl propylene polymer defoamer. Its component content is 12%±1, the solvent is a naphthenic solvent, and the water content is below 0.01%. Its application focus is foam in solvent-based systems:

1) it can be used for foam suppression and air release in production, reducing foam brought in by high-speed dispersion and grinding; 2) for systems prone to boiling-type popping, its effect on film bubbles can be observed through formula tests. The data also mention use in screen printing inks, with air release and leveling performance both considered, so systems that care about printed surface can be tested specifically.

DH-2022A is mainly for solvent-based systems and can be applied in coatings, electronic materials, sealants, floor coatings and cutting fluids.

For solvent-based coatings, watch foam after high-speed mixing, air release speed at rest and film state after application. For screen printing ink, add a printing test and check surface flatness, bubbles and ink spreading. For floor coatings, combine scraping or rolling application and see whether bubbles easily remain inside the film. Test methods differ between systems, so the dosage must be reconfirmed for each formula.

The reference dosage in the DH-2022A data is 0.1%-1.0% of the total formula. In testing, set several dosage levels for comparison:

first observe foam suppression in the production stage, then air release after standing; then apply the coating and check the film for bubbles, craters and other surface problems. For screen printing ink, compare the surface state at different dosages directly on printed sheets. This shows the defoamer's effect on both production and the final film, so the dosage is not decided by the amount of liquid-surface foam alone.