Synthesis and fabrication of biobased thermoplastic polyurethane filament for FDM 3D printing

Abstract This study describes a soft‐actuator grade thermoplastic polyurethane (TPU) with 73 ~ 86 shore A, the method of its fabrication and selected properties. The TPU was produced using bio‐based synthesized TPU (HP 2.5, HP 3.0, HB 2.5, and HB 3.0) pellets with bio‐based polyether‐biol (PO3G‐1000), and dicyclohexylmethane diisocyanate (H 12 MDI) and bio‐based 1,3 propanediol (PDO) and 1,4 butanediol (BDO) as a chain extender. The TPU was formed into a filament for fused deposition modeling (FDM) 3D printers during a melt‐extrusion process at 180 ~ 220°C. The manufactured TPU filaments were characterized by rheological, chemical, thermal, and mechanical analyses. The equivalence ratio 3.0 with a relatively large amount of HS with BDO as a chain extender, more hydrogen‐bonding peaks occurred. The transition temperature and mechanical properties increased depending on the [NCO]:[OH] ratio, and for BDO as the chain extender. However, it was found that when PDO derived from natural material was used, the thermal stability was better. From these results, samples of auxetic re‐entrant TPU were printed with the filaments with reference to the melt flow index. The results showed that the bio‐synthesized HP 3.0 with a hardness of (82 ± 1) shore A was most suitable for FDM 3D printing.