Modeling of Complex Viscosity Changes in the Curing of Epoxy Resins from Near-Infrared Spectroscopy and Multivariate Regression Analysis

The present study investigates the relationship between the changes in complex viscosity and near-infrared spectra. Principal component regression analysis is applied to a near-infrared data set obtained from the in situ monitoring of the curing of diglycidyl ether of bisphenol A with the diamine 4,4′-diaminodiphenylmethane. The values of complex viscosity obtained by dynamic mechanical analysis during the cure process were used as a reference. The near-infrared spectra recorded throughout the reaction, unlike the univariate data analysis at some wavelengths of the spectra, contain a sufficient amount of information to estimate the complex viscosity. The relationship found was high and the results demonstrate the quality of the fitted model. Also, a simple user-friendly procedure for applying the model, focused on the user, is shown.