FT-NIR monitoring of a scattering polyurethane manufactured by reaction injection molding(RIM): univariate and multivariate analysis versus kinetic predictions

Near InfraRed (NIR) spectroscopy was used to monitor in situ a polyurethane synthesis during a RIM process. Univariate and multivariate analysis of transmittance spectra were used to calculate the reaction extent. A very good agreement was observed between multivariate analysis (PCA), univariate (Beer-Lambert) analysis and kinetic predictions. It was demonstrated that, in this case, PCA methods can provide a good estimation of the reaction extent versus time, without time-consuming calibration. The spectral range of PCA has to be carefully chosen.