From Rigid Thermoset Foam to a Flexible Reprocessable Elastomer: Thermoplasticizing Polyurethane Networks through Strategic Insertion of Soft Segments

Abstract Rigid polyurethane (PU) foams are ubiquitous in engineering applications owing to their excellent performance derived from robust three-dimensional structures. However, the inherent irreversibility of these PU thermosets prohibits recycling via conventional melt processing techniques, resulting in a low end-of-life recycling rate and creating profound environmental challenges. To address this limitation, we have demonstrated the plasticization of cross-linked PU thermosets through the strategic insertion of soft segments (SISS). Triggered by heat and catalyst, polyether soft chains were covalently grafted into the rigid PU matrix through hydroxyl−carbamate metathesis and the architectural rearrangement effectively transforms the initially brittle PU thermoset into flexible, reprocessable elastomers. Moreover, the resulting elastomers exhibited shape-memory and self-healing characteristics. These elastomers retained their structural integrity and mechanical properties even after multiple recycling cycles. By bridging the gap between intractable PU thermosets and malleable thermoplastics, this research establishes a sustainable method for upcycling postconsumer PU thermosets into high-value elastomeric materials.