The advantages and disadvantages of silicone defoamer


Advantages:


1) Wide application: Due to the special chemical structure of silicone oil, it is neither soluble with water or substances containing polar groups, nor is it soluble with hydrocarbons or hydrocarbon-based organic compounds. Because of the insolubility of silicone oil to various substances, it is widely used, which can be used for water system defoaming and oil system.






2) Small surface tension: the surface capacity of silicone oil is generally 20-21 dyne/cm, which is smaller than the surface tension of water (72 dyne/cm) and general foaming liquid, and the antifoam effect is good.


3) Good thermal stability: Taking the commonly used dimethyl silicone oil as an example, it can withstand 150 ° C for a long time, and can withstand more than 300 ° C for a short time, and its Si-O bond does not decompose. This ensures that the silicone defoamer can be used over a wide temperature range.


4) Good chemical stability: Because the Si-O bond is relatively stable, the chemical stability of silicone oil is very high, and it is difficult to chemically react with other substances. Therefore, as long as the preparation is reasonable, the silicone defoamer is allowed to be used in the system containing acid, alkali and salt.


5) Physiological inertia: silicone oil has been shown not to be toxic to humans and animals, and its semi-lethal dose is greater than 34 g/kg. Therefore, silicone defoamer (in the combination of suitable non-toxic emulsifiers, etc.) can be safely used in food, medical, pharmaceutical and cosmetics industries.


6) Strong defoaming power: silicone defoaming agent can not only effectively break the foam that has been generated, but also significantly inhibit the foam and prevent the formation of foam. Its use is very small, as long as the weight of the foaming medium is added one millionth (1ppm), that can produce defoaming effect. Its common range is 1 to 100 PPM. Not only the cost is low, but also does not pollute the defoaming material.


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Cons:


1) Polysiloxane dispersion is more difficult: polysiloxane is difficult to dissolve in water, hindering its dispersion in the water system, dispersant must be added, dispersant added more, the emulsion is stable, the defoaming effect will become worse, it is necessary to use less emulsifier, so that the defoaming effect is good, and the emulsion is stable.


2) Silicone is oil-soluble, reducing its defoaming effect in the oil system.


3) Long-term high temperature resistance and strong alkaline resistance