Online real time determination of free formaldehyde content during polymerization process of phenolic resin by NIR spectra and a free modeling method

Abstract Real time detection of free formaldehyde content during synthesis process of phenolic resins is of great significance for controlling the quality of resin products. In this paper, we proposed a method of Near infrared (NIR) spectroscopy combined with multivariate curve resolution-alternating least squares (MCR-ALS) to online real time detect free formaldehyde content during the synthesis process of phenolic resins. The absorption band of CH bonds in formaldehyde was extracted by MCR-ALS from the overlapped absorption bands of CH bonds in phenol, formaldehyde and intermediate products, and is directly utilized to monitor free formaldehyde content during polymerization process. The calculated results of MCR-ALS are highly consistent with those obtained by the chemical titration method, which indicates this method is accurate. Compared with multivariate calibration commonly used for NIR, this method does not require modeling, and is more labor-saving and easier to spread in industrial production.