Mechanochemistry–Reactive Extrusion: A Solvent-Free, Scalable Strategy for Multifunctional Thermoplastic Polyurethane Composites

Thermoplastic polyurethane (TPU) is a versatile, melt-processable elastomer valued for its flexibility and durability. However, expanding its application to advanced industries requires enhanced multifunctionality, such as improved flame retardancy and thermal conductivity, without compromising its intrinsic mechanical properties. In this study, we present a fully dry, solvent-free strategy that integrates mechanochemistry (MC) with reactive extrusion (REX) to fabricate multifunctional TPU composites. Unlike conventional methods that rely on solution-based processing or hard segment interactions, this approach leverages MC to pre-establish a bonded filler network, which is then grafted onto the TPU soft segments via reactive coupling during REX. This sequential MC–REX process enables uniform filler dispersion and enhanced interfacial compatibility, while eliminating the need for solvents or additional compatibilizers. Characterization results demonstrate that composites prepared via MC–REX exhibit improved flame retardancy, enhanced thermal conductivity, and minimized deterioration in mechanical properties compared to conventional composites. Moreover, the composites retain their mechanical performance after multiple reprocessing cycles, indicating improved recyclability. This work offers a scalable, eco-friendly processing platform for designing next-generation TPU composites with tunable multifunctionality through controlled soft segment–filler interactions.