Advantage:            1) Wide application: due to the special chemical structure of silicone oil, it is neither soluble with water or substances containing polar groups, nor with hydrocarbons or organic substances containing hydrocarbon groups. Due to the insolubility of silicone oil to various substances, it has a wide range of applications. It can be used not only in water system defoaming, but also in oil system.            2) Small surface tension: the surface capacity of silicone oil is generally 20-21 dyne / cm, which is smaller than that of water (72 dyne / cm) and general foaming liquid, and has good defoaming effect.            3) Good thermal stability: take the commonly used dimethylsilicone oil as an example, it can withstand 150 ℃ for a long time and 300 ℃ for a short time, and its Si-O bond does not decompose. The silicone defoamer can be used in 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 react with other substances. Therefore, as long as the formulation is reasonable, the silicone defoamer can be used in the system containing acid, alkali and salt.            5) Physiological inertia: silicone oil has been proved to be non-toxic to humans and animals, and its half lethal dose is more than 34 g / kg. Therefore, organosilicon defoamer can be safely used in food, medical treatment, medicine, cosmetics and other industries.            6) strong defoaming power: silicone defoamer not only can effectively break the foam that has been generated, but also can significantly inhibit foam and prevent foam formation. Its use amount is very small, as long as one millionth (1ppm) of the weight of the foaming medium is added, the defoaming effect can be produced. Its common range is 1 to 100 ppm. Not only the cost is low, but also the defoaming substance is not polluted.            Disadvantages:            1) the dispersion of polysiloxane is more difficult: polysiloxane is insoluble in water, hindering its dispersion in the water system, adding dispersants and dispersing agents, and stabilizing the emulsion. The defoaming effect will be worse. The emulsifier must be used less, so that its defoaming effect will be good, and the emulsion will be stable.            2) Organosilicon is oil soluble, which reduces its defoaming effect in oil system.            3) Long time high temperature and strong alkaline resistance