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How to evaluate defoaming efficiency and compatibility of defoamer in paint？

How to evaluate defoaming efficiency and compatibility of defoamer in paint？

Defoaming efficiency test

Foam height method

When defoaming agents are added, the defoaming rate of defoamers is a concern of
many engineers. When testing the defoaming efficiency, we took the foam height
method.
Method: Take a certain amount of the defoamer-containing paint into the measuring
cup with the marking line, use the micro air compressor to introduce the air into the
coating system, observe the height of the coating inside the cup, the higher the liquid
level, the more the defoaming effect difference.
It can be used for rapid screening of initial defoamers, and needs to be combined with
other test methods such as specific gravity method and roll coating method.

Defoaming efficiency test

Specific gravity method

The high-speed agitated paint is poured into a density cup, the density of the paint is measured, and then the paint is sealed and stored, and the density is measured after a certain period of time to check whether the density changes.

Defoaming efficiency test

Spray coating experiment
The coating agent containing the antifoaming agent which was stirred at a high speed was immediately poured onto the polyester film in which the frame was placed at an angle of 25°, and the surface state of the dry film was observed.

Defoaming efficiency test

Roll coating experiment

Take a certain amount of paint, apply a coating film of the same area on a non-pervious, non-porous substrate with a sponge roller, and observe the surface state of the dried coating film.

Evaluation grade/Evaluation grade:

5-No bubbles, 4- very small bubbles, 3 - a small amount of bubbles, 2 - more
bubbles, 1 - no bubbles

Defoamer and system compatibility test

Scrape film test

Procedure: The coating preparation was equilibrated for 24 hours and then coated on a glass plate with a 75 um wet film thickness paint. Observe the wet film and dry film surface conditions.

Paint film defects:

Shrinkage: the phenomenon of a number of circular pits with different sizes and different distributions after the paint film is dried.
Fisheye: There are particles in the circular pits on the surface of the paint film, which is like a "fisheye".
Pinhole: A morbidity in the paint film that resembles a pinhole. It is caused by the air
bubbles mixed in the wet paint film and other air bubbles generated, which cannot be leveled before the paint film dries.
Orange peel: The paint film has a surface-like appearance of orange peel.
Rating / 0 ~ 5 :
0 = no film defect
5 = serious paint film defects, such as local shrinkage of the paint film, pits, shrinkage holes,orange peel and other defects.
https://www.ywlchemical.com/industries/paints-coatings/
https://www.linkedin.com/company/china-defoamer



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