Preparation of epoxy/MCDEA networks modified with ionic liquids

Ionic liquids based on imidazolium, pyridinium and phosphonium with long alkyl chain were used to develop epoxy networked materials cured at high temperature, with 4,4′-methylene-bis 3-chloro-2,6-diethylaniline (MCDEA). Imidazolium- and pyridinium-based ILs decreased the onset curing temperature suggesting an accelerating effect, whereas those based on phosphonium salts exerted only a marginal effect on the curing process. The presence of the ILs resulted in a decrease of the glass transition temperature and this effect was less pronounced in systems containing phosphonium-based IL with [PF6] as the counteranion. The storage modulus below the Tg increased with the addition of ionic liquid suggesting an improvement of stiffness due to the interactions between the ILs and the epoxy matrix. Such interactions were also confirmed by rheological properties. Considering different ionic liquids, those constituted by phosphonium salts were effectively confined inside the epoxy networks and that containing iodide as the counteranion presented the best thermal stability, being indicated for assessing epoxy-based systems with high curing temperature.