Factors affecting defoaming agents in coating formulations
Factor 1: Surface tension
The surface tension of the paint has a great influence on the defoaming agent. The surface tension of the defoaming agent must be lower than the surface tension of the paint, otherwise it will not have defoaming and foam suppression effects. The surface tension of the coating is a variable factor, so when selecting a defoamer, the surface tension must be constant and the surface tension changes must be taken into account.
Factor 2: Influence of other additives
Most of the surfactants used in coatings tend to be functionally incompatible with defoaming agents. In particular, emulsifiers, wetting and dispersing agents, leveling agents, thickeners, etc. will affect the effectiveness of defoaming agents. Therefore, when combining various additives, we must pay attention to the relationship between different additives and choose the best balance point.
Factor 3: baking temperature
When the coating enters high-temperature baking at room temperature, the viscosity begins to drop instantly, and the bubbles can move to the surface. However, due to the volatilization of the solvent, the solidification of the coating, and the increase in surface viscosity, the foam will become more stable and trapped on the surface, causing shrinkage. holes and pinholes, so the baking temperature, fixing speed, and solvent evaporation rate also have an impact on the effectiveness of the defoaming agent.
Factor 4: Solid content, viscosity, and elasticity of the coating
High-solid thick coatings, high viscosity, and high elasticity coatings are all very difficult to defoam. In these coatings, defoaming agents are difficult to diffuse, microbubbles grow slowly, the ability of foam to migrate to the surface is reduced, and the foam has high viscoelasticity, etc. There are many factors that are detrimental to defoaming. Foam in these coatings is quite difficult to eliminate, so it is best to use a defoaming agent and a defoaming agent together.
Factor 5: Coating method and construction temperature
There are many coating construction methods, such as brush coating, roller coating, shower coating, scraping coating, spray coating, screen printing, etc. The degree of foaming of the paint varies depending on the coating method used. Brushing and roller coating produce more foam than spraying and scraping. There are more foams when the temperature is high than when the temperature is low, but the foam is easier to eliminate when the temperature is high.
