The difference and mechanism between defoamer and deaerator
In daily life, foam is very common. Although some common foams will not cause much harm, they will affect industrial production. In such cases, defoamers or deaerators need to be added for treatment. So, why can’t some defoamers be replaced by deaerators? What is the difference between the two? The following is a detailed introduction by industry experts:
1. The current theory of foam formation distinguishes between defoaming and deaeration. The function of the defoamer is to trap air at the interface. The function of the deaerator is to make the tiny air dispersed in the coating rise to the surface quickly during and after the coating process. However, in practical applications, this distinction is often not made clearly.
2. Defoamers can also eliminate microbubbles to a certain extent. The defoaming mechanism of defoamers in water-based coatings and inks is discussed below. For defoamers to show their effects, they must meet certain requirements. One of them is that they must be able to destroy the above-mentioned foam stabilization mechanism. To this end, the defoamer must have a certain degree of incompatibility in the system and be able to migrate to the air interface. Of course, serious side effects such as shrinkage caused by the use of defoamers should not occur.
In addition, in order for the defoamer to be able to defoam, the defoamer emulsified into tiny droplets in the coating must combine with the surfactant layer that stabilizes the foam and penetrate into the bimolecular film layer of the foam. Next, the defoamer must spread quickly and pass through the cracked surfactant layer.
The elasticity of the film at this time is significantly reduced compared to the surfactant film of the previous stable interlayer.
Finally, this instability causes the bimolecular film layer to rupture, thereby achieving the defoaming effect. Therefore, incompatibility, high spreading ability and low surface tension are important properties that every defoamer must have. Adding fine hydrophobic particles, such as silica, to the defoamer will effectively enhance its defoaming ability.
The mechanism of action of defoamers and deaerators can be explained as a dewetting process. The stable surfactant bimolecular film layer cannot wet the hydrophobic solid particles, resulting in unstable surface tension in the local area, which causes the bimolecular film layer to rupture.
