Abstract
The production chemist contributes to ure thane foam technology through development of control tests plant and formulation changes. Urethane foams are made by three types of machines but common principles appear to ap ply. Dissolved air is essential to foam forma tion, and cell size is regulated by "cavitation" (extraction of dissolved gases). Greater cavi tation gives faster nucleation and finer cells. Cavitation, controlled by outlet orifice diame ter in the high pressure/low shear mixing head and by rotor speed in the low pressure/ high shear head, does not occur in the low pressure/intermediate shear head so air must be added.
Additional factors influencing cell size are the presence of fluorocarbons or finely di vided solids. Constant surfactant concentra tion is important for foam stability.
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