Explanation of Common Problems in the Use of Defoamers
The harmful foam produced in industrial production needs to be treated with defoamer. There may be some problems in the use of defoamers. Here is a simple example to illustrate.
1. Turbidity
The main ingredients of defoamers are generally hydrophobic particles, silicone oil and emulsifiers. Hydrophobic particles adsorb silicone oil to maximize the effect of silicone in the case of as little as possible. Silicone oil is the main defoaming medium. Its surface tension is very small. It is neither oil nor hydrophilic. It suspends in the system and defoamer exists in the middle of the foam wall. The oil and water phase dissolves and the silicone oil has a small amount of consumption. When the silicone oil outside the hydrophobic particles is completely consumed, the foaming system will become cloudy. Therefore, the amount and color of hydrophobic particles, silicone oil and emulsifier used in defoamers are different, resulting in different properties of defoamers. When the defoamer has good defoaming effect and long antifoaming time, there is no turbidity in the system.
2. Oil drift
Because defoamers are not dissolved in the system, but dispersed in the system, the dispersion uniformity of Defoamers in the system is very important. When defoamer is evenly dispersed in the system, it has little effect on the transparency of the system, and the time of agglomeration into larger particles is longer, so it can maintain a considerable time in the system. When defoamer is not evenly dispersed in the system, but agglomerated with many small particles, on the one hand, it will affect the transparency of the system, on the other hand, it will make the time of agglomeration of defoamer into larger particles. Short, this will lead to defoamer added to the system after the appearance of turbidity, bleaching oil. In order to avoid oil bleaching, the following methods can be adopted: to move the adding order of defoamer forward; to dilute before adding the system, the diluent can be water or surfactant in the system.
3. Antifoaming time
The properties of silicone oil in defoamer determine the antifoaming time of defoamer, the content of silicone oil determines the consumption period of defoamer in use, too little silicone oil will make the defoaming performance of defoamer less than the required value, too much silicone oil will affect the performance of defoamer, at the same time, it will reduce the defoaming performance of defoamer; the particle size of defoamer determines the filter resistance of defoamer, and the particle size is too large. It may cause defoamer to be filtered easily and produce bleaching oil, which has an effect on foam suppression. Stirring time is also an important index of defoamer's foam suppression ability. Inadequate stirring may result in turbidity, oil bleaching, weakening defoaming ability and shortening foam suppression time.
4. Failure
Acid and alkali stability; silicone oil can destroy the surface tension of the liquid, and eliminate the effect of foam. If the deacidity of the defoamer is poor, it will cause the decomposition of silicone oil, resulting in decreasing or even losing the ability of defoaming. The addition of silicate in the system will inhibit its decomposition. The dissolution of defoamer; some chemical components dissolve silicone oil into the system, so that defoamer no longer has defoaming effect, but as a surfactant in the system, the foam of the system is higher than that without adding defoamer.
What characteristics should a good defoamer possess?
(1) Strong defoaming power, less dosage.
(2) Addition to the foaming system does not affect the basic properties of the system, that is, it does not react with the defoamed system.
(3) Low surface tension.
4. Good balance with the surface.
_Good heat resistance.
_Diffusion and permeability are good, positive spreading coefficient is high.
_Chemical stability, strong oxidation resistance.
_Gas solubility and good permeability.
_Solubility in foaming solution is small.


_No physiological activity, high safety, used in food, cosmetics and pharmaceutical industries, should comply with the relevant provisions.


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