The defoaming mechanism of defoamers can vary depending on the defoaming system. In general, commonly used defoamers have low solubility in the foaming liquid and exhibit low surface tension. When these defoamers are introduced into the foam system, their droplets penetrate into the foam film. Since the surface tension of the part of the film that the defoamer contacts is significantly reduced, while the surface tension of the surrounding remains unchanged, this causes the liquid film to drain quickly and become thinner. As the defoamer droplets cross the liquid film and extend and break due to the shrinkage of the film, the foam eventually breaks, thus achieving the defoaming effect.
Next, we will explore the unique advantages of silicone defoamers in this process.
Wide application
Silicone defoamers are highly regarded for their unique chemical structure. This structure makes it neither soluble in water or liquids containing polar groups, nor compatible with hydrocarbons or organic matter containing hydrocarbon groups. Because of this, silicone defoamers can play an excellent defoaming effect in a variety of systems, whether it is a water system or an oil system, and its application is extremely wide.
Extremely low surface tension
The surface tension of medium-viscosity silicone oil is about 20 to 21mN/m, which is significantly lower than water (72mN/m) and many other common liquids. This property enables silicone defoamers to quickly reduce the surface tension of the system, thereby achieving efficient defoaming effects.
Strong defoaming ability
Silicone defoamers can not only effectively remove the foam that has been formed, but also significantly inhibit the further generation of foam. Surprisingly, it only needs to be added to one millionth of the weight of the foam system to immediately show the defoaming effect.
Detailed explanation of the characteristics of emulsion defoamers
Emulsion silicone defoamers are usually water-in-oil type. This structure makes them easy to disperse in aqueous systems and become an ideal choice for defoaming aqueous systems. Although silicone oil is more difficult to emulsify than other oils, the use of non-ionic emulsifiers can effectively solve this problem, although its easy foaming characteristics need to be controlled.
Studies have shown that the smaller the silicone emulsion particles, the stronger its defoaming ability. However, this requires an increase in the amount of emulsifier, and the viscosity of the emulsion will also increase, thus affecting the defoaming performance. Therefore, choosing an emulsion particle size of 1 to 10 μm is the key to balancing the defoaming ability and the viscosity of the emulsion.
When using an emulsion defoamer, it should be added directly to the aqueous foaming system to obtain the best defoaming effect. To ensure the defoaming effect and the accuracy of the metering, it is recommended to use a concentrated silicone oil emulsion diluted to less than 10%. Please note that the stability of the diluted emulsion may decrease, and stratification may occur during storage, so it is recommended to use it as soon as possible.
In addition, the temperature, alkaline or acidic conditions of the foaming system are important factors to consider when using an emulsion defoamer. Usually, the dosage range of the emulsion is (10 to 100) × 10-6 (calculated as silicone oil) of the weight of the foaming liquid, and the specific dosage needs to be determined by experiment.
