Molecular Structure Design of Dynamically Bonded Recyclable Commercial Polyurethane Foams for Enhanced Reprocessing Performance and Upcycling

Although commercial polyurethane foam (PUF) possessed significant recycling value, its permanently cross-linked structure made reprocessing and recycling highly challenging. This study utilized biosourced vanillin (VAN) and 4,4'-dithiodianiline (4-DTDA) to design a dual dynamic bond cross-linker (APDV) containing both S-S bonds and C═N bonds for the recycling and reprocessing of commercial PUF. Under hot-pressing conditions, the hydroxyl groups in APDV underwent exchange reactions with the urethane bonds in the polyurethane chains, enabling the one-step conversion of commercial PUF into high-performance plastics and adhesives. The recycled polyurethane plastic achieved a tensile strength of up to 81.50 MPa, while the presence of dual dynamic bonds resulted in a short relaxation time (τ = 15.6 s), endowing the material with excellent recyclability for multiple reuse cycles. Furthermore, the commercial PUF can be transformed into a high-strength adhesive with a lap-shear strength of 16.34 MPa, which was capable of easily lifting an 80 kg adult. This study provided a sustainable and implementable strategy for the recycling and reprocessing of commercial PUF.