Foam problem in coating system usually appears in the process of production and use, due to the existence of surfactants such as emulsifier used to emulsify hydrophobic substrate, wetting agent used to wet the substrate (coated material) and dispersant used to disperse pigments in the formula, which not only produces a large number of air bubbles, but also makes the bubbles have a tendency to stabilise, and won't disappear for a very long time. In the process of coating film formation, bubbles will cause a lot of disadvantages if they do not disappear, so add coating defoamer to eliminate these bubbles in order to achieve satisfactory results!

The reason of bubble formation:

The generation of bubbles is the dispersion system of gases dispersed in the liquid. In the paint, because of the presence of surfactants, these bubbles rise to the air interface, but it is any surface film containing a layer of surfactants surrounded by a layer of bilayer. The bubbles are aggregated together at the surface of the liquid to form a foam layer. Initially, the foam layer contains a number of individual bubbles, but as the number of bubbles increases, they become compressed and tightly bound together, and the pressure of the air in the bubbles changes, transforming them into more stable polyhedral foams.

The problem is usually caused by the formation of polyhedral foam during the production and filling of these coatings. During mixing and dispersing procedures or during the filling of the coating, the appearance of foam layers can complicate the process, delaying production and reducing plant efficiency.

Defoaming mechanism of paint defoamer:

This defoamer is a combination of n-propyl acetate and methyl ethyl ketone. After use, it can quickly combine with the stable surfactant layer and penetrate into the bubble film, spread rapidly after contact with the foam, forming a very thin double-layer film, with the further diffusion of defoaming active substances, replacing the original foam film wall. And because the surface tension of the antifoam agent is lower than that of the bubble liquid, so the antifoam agent molecules attached to the surface of the bubble film will make the local surface tension decrease, and the other parts of the film still maintain the original surface tension. This difference in surface tension on the bubble film will cause the strong part of the tension to pull the weak part of the tension. Therefore, the whole bubble will appear stress imbalance, which will lead to bubble rupture.

The choice of coating defoamer: Defoamer is very targeted, often in a foaming system in a good effect in another system may be poor or even help the phenomenon of foam. Coating antifoam agent selection is a more complex issue, because in the coating system, the types of additives are more, how to match them with the antifoam agent to produce a good effect, which needs to be tested before indeed.