Preparation of hyperbranched polymeric ionic liquids for epoxy resin with simultaneous improvement of strength and toughness

The present work is based on a study of methylhexahydrophthalic anhydride (MHHPA) cured diglycidyl ether of bisphenol A (DGEBA) in the presence of a hyperbranched ionic liquid (HBP-Mim). Differential scanning calorimetry studies confirmed that the curing reaction was accelerated by HBP-Mim. The impact strength of DGEBA (17.1 kJ/m2) increased to 39.5 kJ/m2 after the addition of 9 phr HBP-Mim-2. Tensile and flexural properties also showed a significant improvement as the incorporation of 9 phr HBP-Mim-2 resulted in 63.1% and 135.2% increase in the tensile and flexural strengths of epoxy thermosets, respectively, compared with neat DGEBA. Thermal stability and thermomechanical properties of the HBP-Mim modified epoxy thermosets also showed a significant improvement. The simultaneous improvements in the mechanical and thermal properties could be attributed to increased free volume and cross-link density.