Spectroscopic and Quantitative Chemometric Analysis of the Epoxidised Oil/Amine System

Abstract

The competitiveness between the oxirane functional group and the ester functional group present in a derivative epoxidised oil was studied by monitoring a model system which involved epoxidised oleic oil and aniline (1:1). The reaction was carried out under isothermal conditions at 95°C and monitored in situ by near infrared (NIR) spectroscopy. This system is taken as a model of the curing process in the manufacture of epoxy resins from triglycerides and diamines. Conventional spectroscopic analysis and generalised two-dimensional NIR correlation spectroscopy analysis have led to the conclusion that, even though the formation of secondary amines by ring-opening of the oxirane group as a consequence of the nucleophilic attack of the aniline is prior, the formation of amides as a consequence of the ester group reactivity is a competitive reaction. The presence of the two aforementioned reactions is also in accordance with the significant number of factors found when the spectra data matrix was analysed by evolving factor analysis. By applying multivariate curve resolution–alternating least squares to the NIR spectra obtained during the reaction, it has been possible to obtain the concentration and the spectra profiles of each chemical species involved in the reaction. The performance of the model was assessed by two parameters: alternating least squares lack of fit (lof = 1.67 %) and explained variance ( R2 = 99.68%). The recovered spectra of the generated products have the characteristic bands associated with the two postulated reactions.