Defoaming agent

Ross, Sydney. Chemical Defoaming Agents. Chemical Industries. Maclean-Hunter Publishing Corporation, USA, May 1949. 

Fluid loss additives Antigas migration agents Antifoam and defoaming agents... 

Foam cement is a special class of lightweight cement. The gas content of foamed cement can be up to 75% by volume. The stability of the foam is achieved by the addition of surfactants, as shown in Table 10-9. A typical foamed cement composition is made from a hydraulic cement, an aqueous rubber latex in an amount up to 45% by weight of the hydraulic cement, a latex stabilizer, a defoaming agent, a gas, a foaming agent, and a foam stabilizer [359,362]. Foamed high-temperature applications are based on calcium phosphate cement [257]. 

At high bulk viscosity, lowering the surface tension is not relevant for the mechanism of stabilization of foams, but for all other mechanisms of foam stabilization a change of the surface properties is essential. A defoaming agent will change the surface properties of a foam upon activation. Most defoamers have a surface tension in the range of 20 to 30 mNm . The surface tensions of some defoamers are shown in Table 21-2. 

Silicone Defoaming Agent A few drops of the silicone-defoaming agent sometimes help in breaking an emulsion, and... 

Antiflatidents (carminatives) serve to alleviate meteorism (excessive accumulation of gas in the gastrointestinal tract). Aborad propulsion of intestinal contents is impeded when the latter are mixed with gas bubbles. Defoaming agents, such as dimethicone (dimethyl-polysiloxane) and simethicone, in combination with charcoal, are given orally to promote separation of gaseous and semisolid contents. 

Precipitated silica is used to produce molecular sieves, as an anti-caking agent, and as filler for paper and rubber. Hydrophobic silica is a defoaming agent. 

Sucrose (20) was also used for the reaction of telomerization with 1 [19, 49, 50]. Applying specific conditions, sucrose octadienyl ethers were obtained with an average degree of substitution of 4.7-5.3. These products are practically insoluble in water, clear or almost colorless, and present a viscosity of 1500-2000 cPs at 25°C [39]. These properties confer to these products the possibility of being employed as emulsifiers or defoaming agent [49]. Minimum surface tension of solution of substituted sucrose in water is 25-28 mN/m whatever the degree of substitution... 

If possible, media should be sterilized in situ. In-line sterilizing filters for routine addition of gases, media, acids or alkalis, defoaming agents, etc., to fermenters should be used where possible. 

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