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 in the medical and construction industries.
Silicones used as defoaming agents
Silicone defoamers can also serve to control the quantity of air in cement mixtures.
Often, foam formation is unwanted – it reduces the density of liquids and increases their viscosity, making transport and stirring difficult, resulting in operational failures 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 stabilising surfactants.
The foam lamellas are thereby destabilised and burst, which lets the foam collapse.
Silicones used as foam stabilising 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.
The addition of small amounts of silicone-based additives helps manufacturers of polyurethane foams control the foam structure and development of their products. The high versatility of these additives makes them essential for producing polyurethane foams of all qualities, which are needed for thousands of different applications.
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.