Polyurethane synthesis under high-pressure CO 2 , a FT-NIR study

The effect of CO 2 on the polyurethane synthesis between a polyol and an isocyanate was studied by in situ near infrared spectroscopy in a newly developed instrumented foaming equipment. In particular, first two solutions, namely a polyol/CO 2 solution and an isocyanate/CO 2 solution were formed at high pressure and then, upon mixing, the synthesis was promoted, still under pressure. Near infrared spectroscopy in reflection mode was used to monitor both CO 2 sorption in the polyol and in the isocyanate and the polyurethane synthesis under pressure. Results revealed a significant slowing down effect by the sorbed CO 2 , apparently due to two concurrent mechanisms, namely catalyst deactivation and dilution.