The main function of defoamer is to eliminate harmful foam, and there are also many kinds of defoamers in industrial production today. The defoamers added in different industries are also different. What aspects should be considered when selecting defoamers for coatings? Let's introduce it to everyone below!
1. Insoluble or insoluble in foaming solution
In order to break the foam, the defoamer should be concentrated on the foam film. For defoamers, they should be concentrated and concentrated in an instant, while for foam suppressants, they should be kept in this state regularly. So defoamers are in a supersaturated state in foaming liquids, and only insoluble or poorly soluble ones are prone to reaching supersaturation. Insoluble or difficult to dissolve, it is easy to aggregate at the gas-liquid interface, easy to concentrate on the bubble membrane, and can function at lower concentrations. The defoamer used in water systems, the active ingredient molecules, must be strongly hydrophobic and weakly hydrophilic, with an HLB value in the range of 1.5-3 for the best effect.
2. Surface tension lower than foaming liquid
Only when the intermolecular forces of defoamers are small and the surface tension is lower than that of foaming liquids, can defoamer particles penetrate and expand on the foam film. It is worth noting that the surface tension of the foaming solution is not the surface tension of the solution, but the surface tension of the foaming solution.
3. Has a certain degree of affinity with foaming liquid
Since the defoaming process is actually a competition between the foam collapse speed and the foam generation speed, the defoamer must be able to disperse rapidly in the foaming liquid so that it can quickly play a role in a wider range of foaming liquid. To make the defoamer diffuse quickly, the active ingredient of the defoamer must have a certain degree of affinity with the foaming solution. The active ingredients of defoamers are too close to foaming liquids and will dissolve; Too sparse and difficult to disperse. Only when the closeness is appropriate can the effectiveness be good.
4. No chemical reaction occurs with foaming liquid
Defoamers react with foaming liquids, causing them to lose their effectiveness and potentially produce harmful substances that can affect microbial growth.
5. Low volatility and long duration of action
Firstly, it is necessary to determine whether the system that requires the use of defoamers is aqueous or oily. In the fermentation industry, oil-based defoamers such as polyether modified silicone or polyether based ones should be used. The water-based coating industry requires water-based defoamers and organic silicon defoamers. Select the defoamer, compare the amount added, and based on the reference price, determine the most suitable and economical defoamer product.
