Examining the kinetics of the thermal polymerisation behaviour of epoxy resins initiated with a series of 1-ethyl-3-methylimidazolium based ionic liquids

Abstract An epoxy resin based on the difunctional diglycidyl ether of bisphenol A (DGEBA) is reacted thermally in the presence of a series of 1,3-dialkylimidazolium based ionic liquids comprising the common cation (1-ethyl-3-methylimidazolium) and an anion (acetate, dicyanamide, or thiocyanate). Dynamic differential scanning calorimetry was used to analyse the formulations comprising DGEBA and the ionic liquid where it was revealed that the lowest and highest temperature for the onset of reaction were observed for formulations with 1-ethyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium dicyanamide respectively. Cured glass transition temperatures range from 151 to 175 °C, depending on the anion used. Gelation behaviour is also dependent on the nature of the anion, with the acetate promoting gelation most quickly, whereas the dicyanamide is least reactive. Kinetic analysis of the cure reactions yield consistent results (R 2  > 0.99) using the Ozawa method (E a  = 74–98 kJ/mol) and are in good agreement with previous studies on imidazoles.