3D Printing Tough, Isotropic, and Sustainable Polythiourethanes for Fused Filament Fabrication

3D printing, especially fused filament fabrication (FFF), has captivated the imagination of thinkers, hackers, doers, makers and manufacturers alike for its ability to rapidly convert digital designs into tangible objects.. Many industries such as biomedical, aerospace, and automotive have been early adopters of the technology because of FFF's ability to print complex geometries, its cost-saving ability for custom parts, prototypes and low lot manufacturing runs, and its potential to be a more sustainable manufacturing practice. However, despite these benefits, FFF is still limited to prototyping and non-functional parts in these industries because of its limited selection of engineering-grade filaments and its typically weak mechanical properties. It also shows limited ability to be recycled and reused multiple times, similar to other plastics. Past research has explored various ways to widen the material selection, improve the mechanical properties of FFF filament, and make it more recyclable, but research has yet to show a material with these properties in an easy-to-use filament. This work leverages a thiol-isocyanate click chemistry that produces tough, isotropic, and sustainable FFF filaments. These filaments are comparable to many polymers used in traditional manufacturing, and widely outperform common 3D printed materials in all print directions. This filament also retains its mechanical properties when recycled multiple times without significant changes to the polymer's mechanical or materials properties. While further development is needed for FFF printing to flourish across all industries, this work shows the potential of polythiourethane filaments to offer solutions to some of the most significant drawbacks of FFF technology.