1 Insoluble or poorly soluble in the foaming liquid means the foam is broken, and the defoamer should be concentrated and concentrated on the foam film. For the defoamer, it should be concentrated and concentrated instantly, and for the defoamer, it should always be kept in this state.
Therefore, the defoamer is in a supersaturated state in the foaming liquid, and it is easy to reach a supersaturated state only if it is insoluble or poorly soluble. Insoluble or poorly soluble, it is easy to gather at the gas-liquid interface, easy to concentrate on the foam film, and can play a role at a lower concentration. For defoamers used in water systems, the molecules of the active ingredients must be strongly hydrophobic and weakly hydrophilic, and the HLB value must be in the range of 1.5-3 to work best.
2 The surface tension is lower than that of the foaming liquid. Only when the intermolecular force of the defoamer is small and the surface tension is lower than that of the foaming liquid, can the defoamer particles be immersed and expanded on the foam film. It is worth noting that the surface tension of the foaming liquid is not the surface tension of the solution, but the surface tension of the foaming solution.
3. A certain degree of affinity with the foaming liquid. Since the defoaming process is actually a competition between the speed of foam collapse and the speed of foam generation, the defoamer must be able to disperse quickly in the foaming liquid so that it can quickly play a role in a wider range of the foaming liquid. To make the defoamer diffuse faster, the active ingredients of the defoamer must have a certain degree of affinity with the foaming liquid. If the active ingredients of the defoamer are too close to the foaming liquid, they will dissolve; if they are too distant, they will be difficult to disperse. Only when the affinity is appropriate, the effect will be good.
4. No chemical reaction with the foaming liquid. The defoamer reacts with the foaming liquid. On the one hand, the defoamer will lose its effect, and on the other hand, harmful substances may be produced, affecting the growth of microorganisms.
5. Low volatility and long action time. First, determine the system in which the defoamer needs to be used, whether it is a water-based system or an oil-based system. For example, in the fermentation industry, oil-based defoamers such as polyether-modified silicone or polyether should be used. The water-based coating industry should use water-based defoamers and silicone defoamers. Select the defoamer, compare the addition amount, and refer to the price to get the most suitable and economical defoamer product.
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Post time: Oct-26-2024