Tailoring Recyclability of Cross-Linked Polyurethane Formulations: Impact of Diels–Alder Adduct Purity on Thermal and Mechanical Behavior

Abstract

Dynamic covalent bonds are revolutionizing the design of recyclable polymer networks, offering transformative solutions to the challenges of waste and sustainability. This study reports the synthesis and purification of triol cross-linkers at varying purity levels featuring furan–maleimide adducts and their incorporation into partially biobased cross-linked polyurethanes via a hydroxyl–isocyanate reaction. The cross-linkers enable reversible decoupling through a retro-Diels–Alder (r-DA) reaction at elevated temperatures, thereby facilitating efficient reprocessing and network reformation upon cooling. Systematic investigations demonstrate that increasing cross-linker purity enhances recyclability and stiffness but also influences the balance between strength and ductility, as higher purity leads to increased brittleness. Notably, a moderate purity of 93% delivers performance nearly equivalent to that of 99% while maintaining better overall performance, offering a cost-effective alternative for industrial applications. These findings offer critical insights into the interplay between cross-linker purity and polymer recyclability, establishing a robust platform for next-generation sustainable materials within a helicoidal economy framework.