Environmentally friendly processing of polyurethane foam for thermal insulation

An environmentally friendly processing method of polyurethane foam was prop osed and evaluated for the application of thermal insulation. For the produ ction of polyurethane foam, chlorofluorocarbon (CFC) gases were eliminated to minimize environmental destruction. Carbon dioxide gas was used as a blo wing agent instead of the CFC gas. Ultrasonic excitation was also applied t o the mixture of polyol and isocyanate,to increase the rate of nucleation a nd decrease the thermal conductivity. Nucleation and growth of bubbles were studied theoretically and experimentally. Water was used as a chemical blo wing agent and carbon dioxide gas as the physical blowing agent. Experiment s were carried out with different saturation pressures, and experimental re sults were evaluated to determine the best foaming conditions. Rate of bubb le nucleation, final bubble sizes, conversion during polymerization reactio n, and other parameters were predicted theoretically with the assumption th at negative pressure is generated by the ultrasonic field and the bubble gr owth is controlled by diffusion of the gas from the resin into the bubble. The best results such as low thermal conductivity and small size of bubbles were obtained when the polyol which has been mixed with water was saturate d with carbon dioxide gas and the ultrasonic excitation was applied to the mixture of polyol and isocyanate right after the impingement mixing.