Synthesis and characterization of improved bio-based carbon content thermoplastic polyurethane with bio-aliphatic and petro-aromatic diisocyanate

The study involved producing green thermoplastic polyurethanes (TPUs) that were either partially or fully bio-based. This was achieved through a one-shot polymerization process using a combination of sebacic acid-polyester polyol, 1,4 butanediol derived from renewable sources, and diisocyanate. The diisocyanate used included bio-aliphatic pentamethylene diisocyanate (PDI), petro-aromatic methylene diphenyl diisocyanate (MDI), and a combination of PDI and MDI. Various methods were employed to characterize the newly synthesized TPUs, which had a weight average molecular weight exceeding 120,000 g/mol. Increasing the content of PDI improves the bio-based carbon content up to about 97% and increases the pyrolysis onset temperature. An increase in MDI content results in a rise in the complex viscosity, tensile strength, and strain. However, a PDI-based TPU (P/M_100/0) achieved an excellent phase separation with a tensile strength of 20.7 MPa and elongation of 587.2%, comparable to an MDI-based TPU (P/M_0/100). Overall, this research demonstrates the feasibility of utilizing partially or fully bio-based TPUs as a substitute for conventional MDI, with potential industrial applications.