Types and selection methods of defoamers

Defoamer is a commonly used coating additive, and currently there are many types of defoamers available. When selecting defoamers in practical applications, it is still necessary to consider the industry.

Types of defoamers:

1. Polysiloxane defoamers have strong defoaming and anti foaming abilities, mainly used in solvent based coatings and high-end latex paints. This type of defoamer neither reduces the gloss of high gloss systems nor changes the color of pigment slurry systems. Fluorine modified polysiloxane defoamers used in solvent based coating systems have very low surface tension and exhibit stronger defoaming ability. When the variety, dosage, and addition amount are correct, the use of polysiloxane defoamers will not cause defects such as shrinkage and poor recoating of the coating film.

2. Non silicone defoamers used in water-based systems are mainly mineral oil-based defoamers, which consist of three parts: a carrier, usually mineral oil; The second is hydrophobic particles, such as gas-phase silica; The third is emulsifier, which makes it easy for defoamers to disperse in foaming media. Of course, other additives such as preservatives and other enhancing ingredients may also be added for different needs. Mineral oil defoamers are mainly used in flat or semi gloss latex paints and plasters.

Factors to consider when choosing defoamers: 

(1) It should have a lower surface tension than the foaming medium; 

(2) It is insoluble in the foaming medium, so it can exist in the system in the form of particles, destroy the elastic film of the foam just to be generated, and inhibit the production of foam; 

(3) It has good diffusivity and can quickly spread on the surface of the bubble film and penetrate into the bubble film wall, replacing the surfactant and other substances that play a stabilizing role in foam, so that the membrane wall of the bubble film gradually thins and breaks.

The ideal defoamer should have good defoaming ability and foam control ability, and be non-toxic or low toxic, with good storage stability and low cost.