Foam formation and foam stability is a very sensitive process. Often there is foam when there shouldn't be foam, or the foam collapses although it should be stable. This is also true for chemical processes or when chemicals are used for a specific purpose. Products based on silicones help to control the foam formation in these situations very efficiently.
Often, foam formation is unwanted - it reduces the density of liquids and increases their viscosity, making transport and stirring difficult, resulting in applicational faults and increased costs and delays. Silicone defoamers cause foam to collapse rapidly; anti-foams prevent the formation of foam. These products are typically formulated from a combination of silicone fluid and activating solids such as pyrogenic (fumed) silica, either in form of a compound or as a readily dispersible emulsion.
Because of their spreading properties and due to their low surface tension down to 22 mN/m, silicone fluids can enter into the foam lamella and displace the foam stablising surfactants from the liquid-air interface. The foam lamellas are thereby destabilised and burst, which lets the foam collapse.
Silicone foam controllers are used in detergents as well as in the separation of crude oil from water and the production of pulp for papermaking. The medical and building industries also use silicone defoamers to, for example, control the quantity of air in cement mixtures.
Silicone antifoam agents
Polyurethane foams are widely used to produce lightweight products. These foams are used for furniture, automotive seats and dashboards, insulation e.g. in refrigerators and houses and many other industries. Typically the foams are formed by allowing liquid components to react while a blowing agent generates the foam cells. The chemical reaction yields a mechanically stable foam structure at the end of the curing process. Silicone-copolymers, mostly silicone-polyethers, are widely used as foam control additives in this application. Due to their adjustable surface activity (structure of silicone backbone, degree and type of incorporation of organic polymer) they can control cell nucleation, cell growth, cell stabilisation and -if wanted- controlled cell opening. Closed cells will result in rigid foams for insulation and construction, whereas open cells will result in flexible foams for furniture and packaging. The high versatility of silicone polyethers make them essential additives for producing PU foams in all sorts of quality, which is needed for thousands of different applications.