Sustainable Polyurethane Networks with High Self-Healing and Mechanical Properties Based on Dual Dynamic Covalent Bonds

Hydroxy-terminated polybutadiene (HTPB) based polyurethanes (PU) networks are broadly applied in industry and aviation, however, their nonrecyclability leads to the waste of petroleum. In this work, a series of novel self-healing, weldable, and recyclable HTPB-based PU networks with dual reversible covalent bonds are fabricated by one-pot polycondensation. To shorten the relaxation time, dual reversible covalent bonds (disulfide bonds and boronic ester bonds) are incorporated into the HTPB-based PU networks. Meanwhile, to promote tensile strength, the rigid isocyanate and cross-link agent are introduced into the networks. Obtained HTPB-based PU network structures are characterized by FTIR, Raman, and DMA measurements. Obtained HHMB-4-20 network shows the best mechanical properties (tensile strength = 6.97 MPa, elongation at break = 302 %), and the mechanical properties almost can be recovered after welding/reprocessing by hot pressing. To satisfy the demands of industrial sustainability, the synthesis of PU networks with capabilities of reprocessing, self-healing, and welding is a feasible approach.