Foam, continuous fluorocarbon

In the prepolymer method for one-shot polyether flexible urethane foams the primary role of the silicone surfactant is to lower surface tension and to provide film (cell-wall) resilience. Resilient films prevent the collapse of the foam during foam rise and continue to stabilize it until the foam is self-supporting. A secondary, but nevertheless important role of the silicone surfactant is cell-size control. The silicones can be added to the formulation in any of the 2 to 6 streams usually fed to the mixing head in the one-shot process. Usually, however, the silicone is metered separately, in combination with the polyol, or added as a wa-ter/amine/silicone mixture. It can also be added in the fluorocarbon blowing agent (52). 

Liquid continuous phase. Gas-in-liquid dispersions are the foams or the boiling liquids (Prud homme and Khan 1996, Exerova and Kruglyakov 1998). Liquid-in-liquid dispersions are usually called emulsions. The emulsions exist at room temperature when one of the liquids is immiscible or mutually immiscible in the other, e.g. water, hydrocarbon and fluorocarbon oils and liquid metals (Hg and Ga). Many raw materials and products in food and petroleum industries exist in the form of oil-in-water or water-in-oil emulsions (Shinoda and Friberg 1986, Sjoblom 1996, Binks 1998). The solid-in-liquid dispersions are termed suspensions or sols. The pastes, paints, dyes, some glues and gels are highly concentrated suspensions (Schramm 1996). 

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