Scalable Fabrication of a Tough and Recyclable Spore-Bearing Biocomposite Thermoplastic Polyurethane

Abstract

Thermoplastic polyurethanes (TPUs) are a class of versatile thermoplastic elastomers where most of their products lack a proper recycling strategy or have no end-of-life solutions. To pursue a sustainable end-of-life solution for TPU based products, self-disintegrating biocomposite TPUs have recently been developed by embedding spores of TPU-degrading bacteria into TPUs using melt extrusion. Herein, we improve upon spore-bearing biocomposites and demonstrate industrially-relevant manufacturing conditions for the fabrication of biocomposite TPUs. Spore production was modified to reduce the innate brown color of the resulting materials and, effectively minimize the coloration of biocomposite TPUs. Reduction of FeSO4 in a sporulation media generated white spores without compromising spore productivity, viability, morphology or heat-shock tolerance. Biocomposite TPUs containing white spores displayed a 45% increase in toughness compared to TPUs without spores, while retaining [~]90% spore viability post processing. Furthermore, biocomposite TPU fabrication was demonstrated using a scalable continuous extruder followed by injection molding. Biocomposite TPUs generated by these industry-relevant processes exhibited comparable toughness improvement and spore viability to biocomposite TPU prepared using a lab scale microcompounder, while enhancing productivity by 30-fold. Finally, spore addition improved biocomposite TPUs recyclability, enabling 80% toughness retention after 5 rounds of iterative melt processing. Additionally, no negative effect on the lifespan of the generated TPUs was observed over a duration of 1 year of storage. Overall, this study confirmed that spore-bearing biocomposite TPUs are promising for practical applications, offering an accessible method to enhance toughness and sustainability of commercial TPUs through the incorporation of spore-based living fillers.