As a commonly used additive, defoamers are also widely used in coating production. However, when using defoamers, people often simply think that they only play a role in defoaming. Is that all? Below, the editor of Jianyi Chemical will provide a detailed analysis for everyone!
Defoamers can be divided into three types: defoamers, foam suppressants, and defoamers. Bubble breaker refers to a substance added after the liquid has formed bubbles, which enters the bubble membrane through adsorption and surface tension to thin the base and quickly destroy the bubbles, lowering the liquid level. Foam inhibitor is a substance that can inhibit the production of foam. It is adsorbed on the bubbles together with liquid foaming substances, reducing the surface tension, thinning the foam film, causing damage, and preventing foaming. The defoamer adsorbs onto bubbles in the liquid, gathering the air inside the bubbles. After the bubbles adsorb to each other, they break at the adsorption interface and form a large bubble. The increase in buoyancy accelerates the ascent speed, promoting defoaming. However, defoamers generally have multiple functions such as breaking bubbles, inhibiting bubbles, and defoaming, so it is often difficult to strictly distinguish them.
In addition, defoamers often do not separate into layers. Even if they do not separate into layers, they should be stirred evenly before use. If necessary, they should be diluted with water or cosolvents (due to the poor storage toughness of diluted defoamers, it is recommended to dilute them immediately). When arriving, it is necessary to arrive quickly under stirring, and if necessary, reduce the steps, which will result in unsatisfactory outcomes. For example, defoamers with strong field strength during grinding, and defoamers with weaker defoaming ability that may be reduced during paint mixing, can effectively alert and defend against the drawbacks of shrinkage, pinholes, fish eyes, and other defects in water-based wood coatings during construction. The shear force during stirring is used to ensure good dispersion of the particles of the defoamer, but excessive shear force weakens the defoaming effect by making the defoamer particles too small; Inefficient emulsifiers also have drawbacks, as reducing the relatively low shear force at the end of the attack may result in good outcomes, but in most scenarios, it is insufficient; During the storage process of paint, defoamer particles will form larger droplets, leading to an increase in the tendency of paint foaming and surface defects.
