advantage:
1) Wide application: Due to the special chemical structure of silicone oil, it is neither compatible with water or materials containing polar groups, nor with hydrocarbons or organic materials containing hydrocarbon groups. Due to the insolubility of silicone oil to various substances, it has a wide range of applications. It can be used for defoaming in water systems and oil systems.
2) Low surface tension: The surface capacity of silicone oil is generally 20-21 dyne / cm, which is lower than that of water (72 dyne / cm) and general foaming liquid, and has good defoaming performance.
3) Good thermal stability: Take the commonly used simethicone as an example, it can withstand 150 ℃ for a long time and 300 ℃ or higher for a short time, and its Si-O bond does not decompose. This ensures that the silicone defoamer can be used in a wide temperature range.
4) Good chemical stability: Since the Si-O bond is relatively stable, the chemical stability of the silicone oil is very high, and it is difficult to chemically react with other substances. Therefore, as long as the formulation is reasonable, the silicone defoamer is allowed to be used in the system containing acid, alkali and salt.
5) Physiological inertness: Silicone oil has been proven to be non-toxic to humans and animals, and its half-lethal dose is greater than 34 g / kg. Therefore, silicone defoamers (with suitable non-toxic emulsifiers) can be safely used in food, medical, pharmaceutical and cosmetic industries.
6) Strong defoaming power: The silicone defoaming agent can not only effectively break the foam that has been formed, but also significantly suppress the foam and prevent the formation of foam. It is used in very small amounts, as long as one part per million (1 ppm) of the weight of the foaming medium is added, it can produce a defoaming effect. Its usual range is 1 to 100 ppm. Not only is the cost low, but it does not contaminate the defoamed material.

Disadvantages:
1) Polysiloxane is difficult to disperse: Polysiloxane is difficult to dissolve in water, which hinders its dispersion in the water system. A dispersant must be added. If more dispersant is added, the emulsion is stable and the defoaming effect will change. Poor, it is necessary to use less emulsifier to make the defoaming effect good and the emulsion stable.
2) Silicone is oil-soluble, which reduces its defoaming effect in oil systems.
3) Long-term high temperature resistance and poor alkali resistance