Advantages and disadvantages of organosilicon defoamer


Advantage:


1) Wide application: Because of the special chemical structure of silicone oil, it does not dissolve with water or substances containing polar groups, nor with hydrocarbons or organic compounds containing hydrocarbons. Because of the insolubility of silicone oil to various substances, it is widely used in water system defoaming and oil system.


2) Low 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 fluid, and the defoaming efficiency is better.


3) Good thermal stability: Take dimethylsilicone oil as an example, it can withstand 150 C for a long time and over 300 C for a short time, and its Si-O bond does not decompose. It ensures that organosilicon 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 preparation is reasonable, organosilicon defoamer is allowed to 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 semi-lethal dose is more than 34 g/kg. Therefore, organosilicon defoamers (in combination with non-toxic emulsifiers, etc.) can be safely used in food, medical, pharmaceutical and cosmetic 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 usage is very small, as long as adding one millionth of the weight of foaming medium (1 ppm), it can produce defoaming effect. Its common range is 1 to 100 ppm. Not only the cost is low, but also the defoamed 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) Silicone is oil-soluble, which reduces its defoaming effect in oil system.


3) Long time high temperature resistance and poor alkalinity resistance