Polyurethane synthesis under high-pressure CO2, a FT-NIR study

The effect of CO2 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/CO2 solution and an isocyanate/CO2 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 CO2 sorption in the polyol and in the isocyanate and the polyurethane synthesis under pressure. Results revealed a significant slowing down effect by the sorbed CO2, apparently due to two concurrent mechanisms, namely catalyst deactivation and dilution.