Formulation design system of water-based coatings - defoaming agent and anti-foaming agent 1

2019-07-10

Defoamer is one of the most difficult additives in waterborne wood coatings to control the balance between defoaming and leveling.The paint liquid will generate bubbles during the application due to agitation .If the bubbles present in the paint are not removed in time, the film will dry and form an unacceptable flaw.The paint also produces air bubbles during production, pumping and filling.
Defoaming is a non-negligible factor in the formulation design process. The defoaming mechanism of the defoaming agent is to penetrate the foam film produced by the system by wetting and continuously spread on the film, so that the surface tension of the foam film is unbalanced and broken bubble.Generally speaking, the defoaming agent is divided into two types, a suds suppressor and a defoaming agent. The function of the suds suppressor is to inhibit the foaming of the waterborne wood coating under the action of an external force, and the defoaming agent is mainly on the surface of the foamed film. Rapidly spread, destroy the elastic membrane of the bubble, and make it rupture, but often the effect of the two combinations is better, otherwise at least one effective defoamer should be selected.Most antifoaming agents, especially silicone defoamers, will cause shrinkage of the wet paint film when the dosage is too large. Therefore, the amount of defoaming agent can be basically eliminated by the principle of eliminating bubbles, so that the defoaming effect cannot be excessively pursued. Side effects such as shrinkage holes. For waterborne wood lacquers, mineral oil defoamers are more tolerant than silicone defoamers, and adding a little more is not prone to severe shrinkage, which can be preferred.

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