Effect of Phosphonium-Based Ionic Liquid Content in Curing Epoxy Resin/Carbon Nanotubes Systems

Abstract

The effect of varying the content of the ionic liquid based on phosphonium, tributyl (ethyl)-phosphonium diethylphosphate, was studied acting with a dual role as a curing and dispersing agent to obtain multiwalled carbon nanotube nanocomposites (MWCNT) dispersed in epoxy resin (ER). The effect of this ionic liquid in the mixtures was evaluated to obtain a better dispersion of the charge in the epoxy matrix, and consequently the impact on the curing of the nanocomposites. The effectiveness of the dispersion was evaluated morphologically by scanning electron microscopy (SEM). The non-covalent functionalization of nanotube nanocomposites (CNT) with IL resulted in better reinforcing effect and higher conductivity, as well as the use of high-speed speed mixer combined with acetone, culminated in better mixing and processing conditions. Under these conditions, the composite showed high electrical conductivity and good dynamic-mechanical properties. The systems with 10phr of the ionic liquid showed the highest of ΔH (heat of reaction), and these values can be attributed to the better adjustment of the stoichiometry, favoring the crosslinking of the resin. the systems with 10phr of the ionic liquid showed the highest of ΔH (heat of reaction), and these values can be attributed to the better adjustment of the stoichiometry, favoring the crosslinking of the resin. However, the systems prepared with 30phr of ionic liquid showed lower values of ΔH, possibly due to its excess in the mixture, culminating in the imbalance of resin/hardener stoichiometry. This can be seen in the scanning electron microscopy (SEM), whose sample cured with 30phr showed cracks, due to the excess of the crosslinking agent causing incomplete curing, making the material more fragile.