Types of organosilicon defoamers
Organosilicon defoamer can be divided into four main categories: oil, silicone oil, emulsion and solid. According to their product form, emulsion silicone oil defoamer is the most widely used and the most consumption.
Oily silicone defoamer
Dimethyl silicone oil is used as the main component of defoamer because of its good chemical inertia, thermal stability, low surface tension, insoluble in water, easy spreading on the surface, etc. Low viscosity silicone oil has good defoaming effect, but poor sustainability; high viscosity silicone oil has slow defoaming effect, but good sustainability. The general rule is that the lower the viscosity of foaming fluid is, the higher the viscosity of silicone oil should be. On the contrary, the higher the viscosity of foaming fluid is, the lower the viscosity of silicone oil is. Simple organic silicon, such as dimethyl silicone oil, has no defoaming effect, but after emulsification, the surface tension decreases rapidly, and the use of a small amount can achieve strong defoaming and anti-foaming effect, becoming an important defoamer component. Usually, a certain proportion of hydrophobically treated silica assistants are mixed in silicone oil to form an oil compound defoamer and silica as filler. Because of its large amount of hydroxyl groups on the surface, it can help to enhance the dispersing ability of silicone oil in the foaming system, increase the stability of the emulsion, and improve the defoaming performance obviously.
Solution Silicone Defoamer
Solution-type silicone defoamer is silicone oil dissolved in some specific solvents, so that the silicone defoamer particles become smaller, the dispersion performance is improved, and can be better dispersed in defoaming objects. The selected solvent must be able to dissolve both silicone oil and foaming medium. Silicone can be dissolved in polychloroethane, toluene, xylene and other organic solvents. The silicone oil solution can be used for defoaming in non-aqueous system. Silicone oil can also be dissolved in organic solvents such as ethylene glycol, glycerol and other alcohols to make defoaming solution suitable for aqueous system. Silicone oil solution defoamer is carried by solvent and dispersed in the foaming liquid. Solvent diffuses and silicone oil condenses into droplets to play defoaming role.
Emulsion type organosilicon defoamer
Silicone emulsion is generally milky white with good fluidity of liquid, has a higher chemical stability, better heat resistance and physiological inertia, can effectively improve the dispersion of silicone oil in the water phase, not only can be applied to the non aqueous phase, but also can be applied to the water phase, has a wide range of applications.  Because silicone oil is difficult to emulsify, if the emulsification is incomplete, the defoaming performance will be seriously affected when demulsification occurs during reuse. The stability of emulsion is an important index of defoaming agent quality, so the choice of emulsifier is the key. Emulsifier is a surfactant, which can form a single molecular layer on the silicone oil and water interface, reduce the surface tension and form a solid composite membrane, so that the emulsion system can achieve a stable effect. At the same time, adding silica aerosol to defoamer can enhance its defoaming ability.
Solid Silicone Defoamer
The existence of emulsifier in emulsion defoamer makes the emulsifier play a role of vesicle when the defoaming component disappears, so the content of emulsifier is one of the problems to be considered in emulsion defoamer. Solid defoamer is to attach the active ingredients of defoamer to the surface of the dispersion system of solid particles, and solve the problems of defoaming ingredients and emulsifiers. Solid silicone defoamer has good storage stability, convenient transportation and use. By changing its carrier or additives, it can be used not only in water phase, but also in oil phase, and has good medium dispersion. Therefore, solid organosilicon defoamer has good application prospects in many industries.
Polyether Modified Silicone Defoamer