New epoxy systems based on ionic liquid

The present paper describes for the first time the use of ionic liquid based on trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate (IL104), as catalytic curing agent for bisphenol A – based epoxy prepolymer (DGEBA). The curing process was investigated by DSC, rheometry and FTIR analysis, indicating an increasing on the curing rate as the amount of IL in the system increased. The final dynamic mechanical properties of the DGEBA/IL networks are strongly dependent on the curing cycle. As the amount of IL is as low as 2.5 phr, no polymerization of the epoxy prepolymer occurs as the curing is done directly at high temperature. On the other hand, when the curing is performed after a long staying time at room temperature followed by a post curing protocol at relative high temperature, i.e.80 and 125 °C, high crosslink density is achieved with even 2.5 phr of IL, which corresponds to a IL/epoxy molar ratio of 0.007. Moreover, high values of glass transition temperatures, i.e.140–150 °C, are reached by using 10–20 phr of IL. No exudation of the IL was observed indicating that the IL displays strong interactions with the epoxy network Epoxy systems cured with this phosphonium – based ionic liquid display higher thermal stability than those cured with conventional aliphatic amines.