Read about paint defoamer in one article
In addition to being beautiful, paint also forms a strong solid film, which is a protective coating. However, it often encounters a problem, that is, foam. Water-based paints and solvent-based paints use various additives in the formula, such as wetting dispersants to make pigments and fillers easy to wet, disperse and stabilize, as well as additives to improve the storage stability of finished paint products, and to adjust the appearance of the paint film to be smooth. Auxiliaries, and some additives that achieve special functions. Most of these additives are surfactants, which can change the surface tension of the paint, which is an internal factor that causes the paint to easily foam. In addition, the stirring and high-speed dispersion when manufacturing coatings, and the shear during spraying, rolling and brushing during application construction will also increase the free energy of the coating system to varying degrees and produce foam, which is an external factor that generates foam.
If the large amount of foam produced by the paint is not eliminated in time, when it is painted on an object, it will cause various defects such as pinholes, shrinkage holes, fish eyes, and orange peel on the surface, which will affect the coating and protective properties. The following serious hazards will also occur:
1. Foam can easily cause volume expansion, resulting in reduced equipment utilization.
2. Foam limits the stirring speed and prolongs the mixing time of the paint.
3. Foam affects the wetting of pigments and fillers.
4. A large amount of foam affects the packaging of the production line and interferes with the packaging operation.
The bursting of bubbles requires three processes, namely bubble redistribution, film thickness reduction and film rupture. It takes a long time to achieve natural defoaming through these three processes. To solve the problem of paint bubbles, adding paint defoamer is the key. Paint defoaming agent is a chemical additive added to the production and use of paint to add a protective shield to the paint, protect the paint from foam, and quickly eliminate foam. The defoaming agent always penetrates into the foam system in the form of particles. After contacting the foam, it captures the hydrophobic chain ends on the foam surface. After rapid spreading, it forms a very thin double film layer, which further spreads and invades. Since liquids with low surface tension always flow to liquids with high surface tension, the low surface tension of the defoaming agent itself causes the surface tension of the bubble film to locally decrease, and the film wall gradually becomes thinner and is strongly pulled by the surrounding film layers with high surface tension. An imbalance in stress occurs, eventually causing the bubble to burst.
According to the ingredients, coating defoaming agents are divided into mineral oil, polyether, silicone, polyether modified silicon, etc. You can choose a defoaming agent according to the defoaming requirements of the product. If you want fast defoaming, then silicone type Defoaming agents are more suitable. If you want better foam suppression effect, you can choose polyether defoaming agent. According to their performance, they can also be divided into high temperature resistant, waterproof, anti-corrosion and other types of coating defoaming agents. From the perspective of form, coating defoaming agents are divided into solid, liquid, and powder. According to the current general view, there are three major categories of defoaming agents for coatings: mineral oil defoaming agents, silicone defoaming agents, and polyether defoaming agents. Polyether defoamer is characterized by strong defoaming and foam suppression capabilities, low dosage, and does not affect the basic properties of the bubble system. It also has good heat resistance, chemical stability, non-corrosive, non-toxic, no adverse effects, non-flammable and non-explosive. Compared with imported products, the performance is not much different and the price is more advantageous. Silicone defoamer has the advantages of easy dispersion, strong defoaming ability, strong versatility, and long-lasting foam suppression. It has a small amount of addition and a relatively wide range of applications. It can be used in both water-based and oil-based systems. The surface tension is small,It has good chemical stability and is difficult to react chemically with other substances. It has strong defoaming ability. It can not only effectively break the foam that has been generated, but also significantly inhibit the foam and prevent the formation of foam. It is an ideal choice for paint defoaming. Mineral oil defoamer has the characteristics of rapid defoaming, high efficiency, long-lasting defoaming and good economy. Can be dispersed in water to form an emulsion with moderate stability. Can be used under both acidic and alkaline conditions. When selecting coating defoaming agents, you should pay attention to the following properties:
1. Pay attention to whether the defoaming agent has strong defoaming ability and stability. A high-quality paint defoamer should not only have good defoaming effects, but also have long-lasting foam suppression effects.
2. Whether it has characteristics that do not affect the gloss and appearance of the paint.
3. During the transportation and construction process, whether it can be well compatible with the coating system, and will not affect the surface film formation, produce surface defects, avoid shrinkage holes and fish eyes, etc. Coating defoaming agents are not universal, so the types of coating defoaming agents used in different emulsions or water dispersions are also different.
4. Whether foam can be suppressed for a long time during production, packaging and use. During the storage process, any defoaming agent will gradually fail as the environment changes and time prolongs. Therefore, it is important for the performance of the coating defoaming agent to be stable so that it does not fail quickly.
On the basis of maintaining good defoaming properties, high-quality coating defoaming agents will not produce shrinkage cavities and other phenomena when the dosage is slightly larger. Because only in this way can we avoid the gradual failure of the defoaming agent over time after adding a larger amount of defoaming agent in the initial stage. For general coatings, you can choose a lower-cost mineral oil defoamer, which can reduce the cost of the defoamer; for high-performance coatings, you need to consider whether the use of defoamer will affect the performance of the coating. In addition, this type of coating emulsion uses a large amount and is prone to foaming, so a high-performance coating defoamer should be selected.
