Bio-based thermo-healable non-isocyanate polyurethane DA network in comparison with its epoxy counterpart

Abstract

Degradability, reusability or healability of polymer networks have significant importance in features of the environmental, economic and materials application. This study deals with synthesis of a reversible non-isocyanate polyurethane (NIPU) network in comparison with its epoxy counterpart. First, furfuryl cyclocarbonate ether (FCE) was synthesized by a green method of CO2 fixation (carbonation reaction) on furfuryl glycidyl ether (FGE; a bio-based compound). Afterwards, Diels-Alder (DA) adducts were synthesized by the reaction between a bismaleimide and FGE or FCE. The DA adducts were characterized by 1H NMR and FTIR. Amine-curing of the adducts produced two different networks. According to dynamic mechanical thermal analysis, the existence of the cyclocarbonate ring resulted in the formation of a more flexible network having less cross-link density in comparison with its epoxy counterpart. Thermal behavior of the DA adducts were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis. The results showed a retro-DA process occurred at ∼130°C. Unlike the epoxy network, molecular disconnection of the NIPU network occurred completely at this temperature after 25min. Disconnected moieties of both networks were re-casted and DA re-structuring of networks was confirmed by solubility test and DSC. Finally, the NIPU showed superior thermo-healing behavior comparing with its epoxy counterpart.