How to choose a defoamers for the formulation system correctly?
What factors affect the defoaming efficiency?
After learn the factors that affect the defoaming efficiency, let's take a look at the impact of our main protagonist today-"defoamer" on the coating system.
So is the defoaming efficiency higher, the defoamer is better?
Generally speaking, the better the antifoaming effect of the defoamer, the worse its compatibility with the system.
Therefore, the best choice of defoamer is to achieve a balance of performance.
There are many factors in the coating formulation that affect the air bubbles and defoaming, so the selection of defoaming agents should be considered comprehensively.
Surface tension
The surface tension of the paint has a greater impact on the defoamer. The surface tension of the defoamer must be lower than the surface tension of the paint, otherwise there will be no defoaming and foam suppression effect. The surface tension of the coating is a variable factor, so when choosing the defoamer, the surface tension must be constant, and then the surface tension variation factor should be taken into account.
The impact of other additives
Most surfactants used in coatings are in a relationship with defoamers that tend to be functionally incompatible. Especially emulsifiers, wetting and dispersing agents, leveling agents, thickeners, etc. will have an effect on the effectiveness of defoamers. Therefore, we must pay attention to the relationship between different additives when choosing various additives, and choose the best balance point.
Baking temperature
When the paint enters high-temperature baking at room temperature, the viscosity starts to drop back instantly, and the bubbles can move to the surface. However, due to the evaporation of the solvent, the solidification of the paint, and the increase in the surface viscosity, the foam will tend to be more stable, trapped on the surface, and shrink. Holes and pinholes, so the baking temperature, fixing speed, and solvent evaporation rate also have an effect on the effectiveness of the defoamer.
The solid content, viscosity and elasticity of the coating
High solids and thick coatings, high viscosity, and high elasticity coatings are very difficult to defoam. In these coatings, the defoamer is difficult to diffuse, the microbubble becomes large, the foaming speed is slow, the foam migration ability to the surface is reduced, and the foam viscoelasticity is large. There are many unfavorable defoaming factors. The foam in these coatings is quite difficult to eliminate. It is best to choose a defoamer and a defoamer together.
Painting method and construction temperature:
There are many coating construction methods, such as brush coating, roller coating, shower coating, blade coating, spray coating, and screen printing coating. Different coating methods have different levels of foaming. Brushing and roller coating have more foam than spraying and scraping. The temperature is higher than that when the temperature is low, but the foam can be eliminated when the temperature is high.
How to choose defoamer for paint and coating?
There are many types of defoamers and different characteristics, so the defoamers selected in different formulas are also different:
Flat coating
Formula characteristics: low viscosity and low defoaming pressure
Suggestion: mineral oil or mineral oil modified polyether
Elastic coatings
Formulation features: high viscosity and high defoaming pressure
Formulation suggestion: Polyether modified silicone
Top-coating and laminating adhesive
Formulation suggestion: Polyethers can effectively prevent surface defects and have little effect on gloss
Colorful water in water:
Formula features: more surfactants, foam stabilization
Formula suggestion: Use polyether or mineral oil modified polyether
After learn how to choose the antifoaming agent, we also prepared the precautions required for the use of the antifoaming agent:
- Before use, it must be fully stirred and mixed evenly;
- Add with mixing of paint;
- Before use, generally do not add water to dilute;
- Dosage should be appropriate. Excessive dosage will cause problems such as shrinkage, edge shrinkage, and poor brushability; too little dosage will result in poor defoaming effect;
- Is best added in two. That is, they are added separately in the grinding stage and the paint adjustment stage, and each time is generally half of the total amount. A defoamer with good foam suppression effect is used in the grinding stage, and a good foam breaking effect is used in the paint adjustment stage.
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