How to choose water-based coating defoamer

In the coating industry, especially water-based coatings, water-based coating defoamers are used to help eliminate the large amount of foam generated during the production of coatings that may affect the quality of coatings. But there are so many water-based coating defoamers, and different manufacturers produce different water-based coating defoamers, so it is confusing to choose and use. So only after understanding the selection and use of water-based coating defoamer, it may be of some help to you!

The solubility or miscibility of the defoamer and water determines its defoaming ability, and a suitable defoamer should not have good water solubility. Defoamer is to be distributed in the gas-liquid interface to play a role in reducing interfacial tension, and easily soluble in water surfactants to minimize the concentration of aggregation at the gas-liquid interface, it may not be defoamed instead of foam. However, completely insoluble surfactants in water-based systems will produce defects in the paint film such as "shrinkage". A good defoamer should be in the water system with good miscibility and immiscibility of a certain equilibrium point, excessive solubility, and insolubility will not produce the desired defoaming effect, which is the main reason for the difficulty of choosing a defoamer.

To choose those defoamers for water-based coatings with excellent stability, defoaming solid ability and will not affect the gloss of the coating products; to detect whether it affects the recoating performance, it is recommended that you use the method of high-speed stirring. Set the speed of the machine, the amount of stirring time and viscosity, and compare the foam elimination time and foam inhibition time of the same height; the amount of water-based coating defoamer added is generally 0.1~0.3%, and it is not recommended to add too much, because it may cause adverse reactions, such as shrinkage, oil splash, and other problems; you can also judge whether you have chosen the right water-based coating defoamer from the speed and stirring time, adhesion and foam height, etc. Most water-based paint defoamer can not be added directly to the diluted water-based paint, it is best to add when the viscosity of the paint/resin is high and the first time to add when grinding material, the second time in the paint, the amount of 1/2.