Advancing Sustainability in FDM 3D Printing: Development and Characterization of Bio-based TPU

Three-dimensional (3D) printing is a sustainable technology with diverse applications. This study synthesized bio-based TPUs (up to 92% bio content) using 1,5-pentamethylene diisocyanate (71% bio-based), polytrimethylene ether glycol (100% bio-based), and 1,4-butanediol (100% bio-based) by varying the OH/NCO molar ratio to create three filaments: PPB 3, PPB 4, and PPB 5. Melt-extrusion at 160–180 °C was used to optimize the filaments for FDM 3D printing, with rheological analysis ensuring consistent production. Auxetic designs, including auxetic struts, rotating squares, and star re-entrants, were 3D-printed to evaluate flexibility, energy absorption, and durability for high-performance garment applications. PPB 3 exhibited the best mechanical properties. The auxetic strut reached 100 ± 2.5%, strain at a stress of 0.60 ± 0.03 MPa, the rotating square design achieved 95 ± 2.1% strain at a stress of 0.20 ± 0.08 MPa, and the star re-entrant structure attained 170 ± 4.0% strain at a stress of 0.17 ± 0.03 MPa during the tensile test. The rotating square structure withstood more than 90 ± 2% strain under a 2.5 kN load in the compression test, highlighting its excellent deformability and resilience, demonstrating exceptional flexibility and durability for advanced textile applications.