What is antifoam?

Antifoam agents Chemical agents commonly used to deal with harmful foam in industrial production are very versatile. The main function of the antifoam is to reduce the surface tension of the liquid. That is, the antifoam diffuses in the foam and forms a double-layer film on the foam wall during the diffusion process. During this diffusion process, the stabilizing surfactant is pushed away. , and reduce the local surface tension of the foam, destroy the self-healing effect of the foam, and cause the foam to burst. Generally, the faster the antifoam spreads on the liquid surface, the faster the liquid film becomes thinner, and the stronger the antifoam effect is. Liquids that can spread on the surface and have a antifoam effect have relatively low surface tension and are easily adsorbed on the liquid surface. Such substances are mainly surfactants such as ethers and alcohols. There are many types of antifoam and their working principles are also different.

When choosing a antifoam, we must first confirm the following points:

1. Whether the antifoam is insoluble in the foaming liquid: In order to burst the foam, the antifoam should be concentrated and concentrated on the bubble film. In the case of foam breakers, it should be concentrated and concentrated in an instant, and in the case of foam suppressors, it should always be maintained in this state. Therefore, the antifoam is in a supersaturated state in the foaming liquid. Only insoluble or poorly soluble antifoam can easily reach the supersaturated state. Only when it is insoluble or difficult to dissolve can it easily gather at the air-liquid interface, be easily concentrated on the bubble membrane, and can it function at a lower concentration. For antifoam used in water systems, the molecules of the active ingredients must be strongly hydrophobic and weakly hydrophilic, with an HLB value in the range of 1.5-3 for the best effect.

2. The surface tension is lower than that of the foaming liquid: Only when the intermolecular force of the antifoam is small and the surface tension is lower than that of the foaming liquid, can the antifoam particles be able to immerse and expand on the foam. It is worth noting that the surface tension of the foaming liquid is not the surface tension of the solution.

3. Have a certain degree of affinity with the foaming liquid: Since the antifoam process is actually a competition between the foam collapse speed and the foam generation speed, the antifoam must be able to disperse quickly in the foaming liquid so that it can be quickly dispersed in the foaming liquid. play a role in a wider scope. To make the antifoam diffuse quickly, the active ingredient of the antifoam must have a certain degree of affinity with the foaming liquid. If the active ingredient of the  antifoam is too close to the foaming liquid, it will dissolve; if it is too sparse, it will be difficult to disperse. Only when the distance is appropriate can the effect be good.

4. No chemical reaction with the foaming liquid: If the antifoam reacts with the foaming liquid, on the one hand the antifoam will lose its effect, and on the other hand it may produce harmful substances that affect the growth of microorganisms.

5. Low volatility and long action time: First, determine the system that requires the use of antifoam, whether it is a water-based system or an oil-based system. For example, in the fermentation industry, oil-based antifoam, such as polyether modified silicone or polyether, must be used. The water-based coating industry requires water-based antifoam and silicone antifoam. Select the antifoam, compare the added amounts, and get the most suitable and economical antifoam product based on the reference price.