A novel method for toughening epoxy resin through CO2 fixation reaction

For the first time, toughening of epoxy resin by CO2 fixation reaction, through a new mechanism has been investigated. Completely CO2 fixed modified epoxy resin was synthesized at different amounts of carbonation content under ambient condition. Increasing cyclic carbonate content led to an increase in the toughness of modified epoxy resin which was evaluated using the critical stress intensity factor (K-IC) calculated by the results obtained from the fracture toughness test. Fracture enhancement was achieved without scarifying the strength. Toughening was obtained through three mechanisms; (I) cross-link density reduction, (II) uncured carbonate groups and (III) formation of the urethane bonds as a result of reaction between cyclic carbonate and amine curing agent. The characteristic of beta-relaxation peaks were studied by dynamic mechanical thermal analysis (DMTA) test and confirmed the toughening effect in the modified resins. The correlation between carbonation content and toughness was provided and an innovative strategy for toughening epoxy resin, called molecular structure modification (MSM) was proposed. As a green technology, toughening by CO2, a greenhouse gas, has a potential for producing high performance polymers with economic benefits. (C) 2016 Published by Elsevier Ltd.