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How to Choose Defoamer Correctly
Time:2019-3-6 15:50:14  Read:437
The production and construction of coatings will produce bubbles to varying degrees, which hinders the smooth operation of production and construction, and at the same time brings defects to the finished coatings. Proper selection of defoamer can ensure the normal production and construction of coatings.

The task of defoamer: to destroy the liquid film on the surface of bubbles, to prevent the formation of bubbles and to promote the collapse of bubbles. Defoamers are used for large bubbles. Microbubbles need to be degassed and defoamed together.

Defoaming agent characteristics: defoamer is insoluble in medium, but it can enter and disperse in the form of droplet. The most effective diameter of defoaming droplet is equivalent to the thickness of foam wall.

Composition of defoamers: The defoamers for waterborne architectural coatings are classified as non-silicon and silicon-containing. Conventional defoamers are composed of the following components:

Active substance: It can break and defoam, and has low surface tension. Representatives include animal and vegetable oils, hydrophobic silica, higher alcohols, etc.

Diffusion agent: wetting emulsifier to ensure that defoaming droplets diffuse into the bubble film and spread. Nonyl (octyl) phenol polyoxyethylene ether, soap salt, etc.

Carrier: It is helpful for the combination of active substance and foaming system, and easy to disperse into foaming system. Combining the two, it has low surface tension, helps to suppress foaming and reduces cost.

Defoaming agent must have two conditions: permeability factor: E= gamma 1+ gamma 12- >0 3 >0, to ensure that defoamer penetrates into the foam wall; spreading factor S= gamma 1- gamma 12- 12- 3 >0, to ensure the dispersal and spreading of defoamer droplets in the foam medium.