Curing kinetics of epoxy-deep eutectic solvent mixtures

• A low-cost and biodegradable catalytic curing agent for epoxy resins has been studied.
• A deep eutectic solvent (DES) initiates the epoxy homopolymerization without hardener.
• The concentration of DES significantly affects the cure behavior.
• The maximum Tg and cross-linking density increases with DES content.
• Isoconversional methods have been applied to study nonisothermal reaction kinetics.

A deep eutectic solvent (DES) based on choline chloride and urea (ChCl-U) was used to prepare epoxy compositions based on low molecular weight diglycidyl ether of bisphenol A (DGEBA) resin. Fourier transform infrared (FTIR) spectroscopy, rheometry and differential scanning calorimetry (DSC) were, then, used to investigate the curing mechanism of epoxy mixtures as a function of the DES content. The results confirmed that the eutectic mixture of choline chloride and urea was able to initiate the reaction of chain homopolymerization in the absence of the hardener, thus acting as a biodegradable and sustainable catalytic curing agent for epoxy resins.Nonisothermal reaction kinetics was modeled with the results obtained by ICTAC Kinetic Project confirming the role of the analyzed deep eutectic solvent in accelerating the homopolymerization of epoxy groups.