Abstract
In polyurethane foam formulations, the limited compatibility of water with polyol and isocyanate can lead to liquid-liquid dispersions, but the kinetic consequence of phase separation in these systems has been poorly understood. In the present study, the reagent compatibility and reactivity of model polyurethane formulations have been evaluated through a combination of ATR-FTIR spectroscopy, chemical titration, and optical microscopy. Kinetic experiments have revealed that phase separation reduces substantially the rate of water/isocyanate reaction. Using a reactive polyurethane model system, blowing and gelling reaction profiles for catalysts with and without the presence of surfactant were obtained. Mass loss rate-of-rise experiments on actual foam with and without surfactant were also conducted. Water titration experiments have indicated that silicone surfactants can induce phase separation of water, but do not effect the ultimate water solubility limit in the model formulations. Although the surfactants improve dispersion of reagents in these systems, no increases in reaction rates are observed in either model systems or actual foams.
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