Manufacturing of Bio-Based TPU/CNT Composites Using Solvent-Free In-Situ Polymerization for 3D Printing Filament Applications

Thermoplastic polyurethane (TPU) is a highly favored polymer for 3D printing materials due to its excellent impact and abrasion resistance, superior mechanical properties, and flexibility at low temperatures. Enhancing TPU with conductivity considerably broadens its application range, paving the way for its use in advanced flexible electronics, wearable technologies, and improved industrial components. The addition of electrically conductive fillers such as multi-wall carbon nanotubes (MWCNTs) can improve the conductivity of TPU. In this study, we synthesized TPU with a bio-based polyol (polytrimethyleneether glycol) and chain extender (1,3 propanediol) and improved its conductivity by adding a small amount of CNTs via in situ polymerization without using any harmful solvents. The CNT content was varied from 0.75 to 3.75 wt% and to achieve a tensile strength of 13.45 ± 0.3 MPa, a maximum elongation at break of 859% ± 6%, a hardness of 77 ± 2 Shore A, and the highest conductivity (2.26 × 10⁻⁴ S/cm) with 3.75 wt% of CNTs. Because these physical properties are sufficient for 3D printing, the TPU/CNT composites developed herein can be promising in applications requiring conductive materials.