Cyclic carbonates as building blocks for non-isocyanate polyurethanes

Three different cyclic carbonates (ethylene, propylene, and butylene carbonate) that can be derived from CO₂ were successfully polymerized with hexamethylenediamine to form non-isocyanate polyurethanes (NIPUs) via self-polycondensation route without the use of harmful di-isocyanates. Three different catalysts were compared for their performance in self-polycondensation. Increasing the side chain length in cyclic carbonate increased the amount of urea side reaction and decreased the solubility of the final product. The increased amount of urea lead to a more thermoset behavior as the melting and decomposition took place simultaneously. Furthermore, the extent of urea side reaction and melting behavior were adjustable with the selection of the catalyst or polymerization parameters. With ethylene and propylene carbonate based precursors, it was possible to obtain promising melting temperatures and lap shear strength for the NIPUs when optimized polymerization parameters and catalyst were used.