Non-isocyanate polyurethane thermoset based on a bio-resourced star-shaped epoxy macromonomer in comparison with a cyclocarbonate fossil-based epoxy resin: A preliminary study on thermo-mechanical and antibacterial properties

Abstract

This study focued on the synthesis and investigation of a bio-based non-isocyanate polyurethane (NIPU) introduced as st-NIPU in comparison with a fossil-based NIPU. First, a star-shaped macromonomer was synthesized through bulk condensation reaction of glycerol and succinic acid using microwaves. Second, the star-shaped macromonomer was epoxidized using epichlorohydrin. Finally, the attained macromonomer was converted to cyclocarbonate star-shaped macromonomer (C-st-G-SA) via CO2 fixation reaction. All of the abovementioned macromonomers were characterized by 1H NMR and FTIR spectroscopies. The st-NIPU network containing 47% bio-resourced part was obtained by the reaction of C-st-G-SA and the amine curing agent. A commercial diglycidylether bisphenol A (DGEBA) epoxy was also CO2 fixed to obtain cyclocarbonate DGEBA (C-DGEBA) and after amine curing a NIPU was achieved (DGEBA-NIPU). The amine curing trends of C-st-G-SA as well as C-DGEBA were studied by differential scanning calorimetry (DSC) to adjust the curing conditions. Also, DSC was utilized to investigate the thermal transitions of the st-NIPU and DGEBA-NIPU networks and the results presented two glass transition temperatures (Tg) for st-NIPU. The appearance of these two Tgs were confirmed by dynamo-mechanical thermogram. Thermal degradation trend of st-NIPU displayed a degradation pattern similar to other polyurethanes. St-NIPU network showed a significant potential of film formation and it could be used in the surface coating applications. The antibacterial activity of st-NIPU films against E.coli and S.aureus bacteria was evaluated and the results showed an acceptable and significant antibacterial property especially against S. aureus bacterium.