Catalytic Effect of Eutectic Hardeners to Polymerize Epoxidized Vegetable Oil for the Synthesis of Fully Biobased Thermosets at Low Temperatures

Abstract

Four different eutectic hardeners (EH) were used to polymerize epoxidized linseed oil. The study highlights very different rate-limiting steps for systems with and without EHs resulting in different final properties. The reaction starts at a much lower temperature in the presence of EH (around 50–80 °C lower), and one system (CATEC-ELO) starts to react at a temperature around 30–40 °C below that of the other EH systems. The different reactivities and final properties of this system are explained by the presence of a hydroxyl group, a more hindered structure, and hydrogen interactions. The reactivity of CATEC-ELO can be parametrized with a two-step competing mechanism (TSC), while the other systems are described by an autocatalytic step, followed by diffusion control of short polymer chains. The four methods proposed in this study, TSC, SVM, VSD(n), and SD(n,p), enable a very good modeling of the polymerization rate. The method of SVM is quite fast and gives very accurate results. The methods SVM, VSD(n), and SD(n,p) combine an autocatalytic step and a term that accounts for diffusion. A new method (SD(n,p)) is presented in this study. It appears that the procedure proposed using several steps yields meaningful kinetic parameters, even in the more complex case where 10 parameters are determined (SD(n,p) method).