The determination of the degree of cure in epoxy paints by infrared spectroscopy

The goal of this paper is to present a method to determine the time evolution of epoxy conversion for epoxy/amine and epoxy/amide formulations in heterogeneous systems such as paints by means of near infrared (NIR) spectroscopy. The cure reaction involves a simple addition mechanism between the oxirane ring and the amine/amide hydrogen functional groups. The extent of the reaction was calculated from the NIR absorption band at around 4530 cm−1 which depends on the oxirane rings concentration. The NIR spectroscopic method, which has the advantage of real time analysis over other techniques such as chemical titration, can be employed with most of the usual, modern FTIR spectrometers.