Dual dynamic network system constructed by waterborne polyurethane for improved and recoverable performances

The implementation of the dynamic crosslinking network toward the commodity polymers such as polyurethane has been much highlighted for resource conservation and environmental protection. This work demonstrates a feasible dual dynamic network (DDN) construction of waterborne polyurethane (WPU) by using a biobased trifunctional ketose, 1,3-dihydroxyacetone (DHA) serving as the chain extender. The WPU dispersion was compatible well with the post-added adipic acid hydrazide (ADH) as the water soluble crosslinking agent. When the one-pot system of WPU-ADH was cast into films, covalent adaptive network (CAN) was formed through the condensation of ketohydrazine and carbonyl groups driven by the evaporation of water. The produced acylhydrazone groups would also contribute to the strengthen on the H-bonding crosslinking network. The synergism of the two sets of the networks provided not only the improved mechanical performances, but their > 95% recovery efficiencies on the 28 MPa of strength and 750% fracture elongation in the self-healing, reprocessing and welding tests under moderate heating. In addition, the WPU exhibited as an effective adhesive to metal with the adhesive strength sustained after four times of deconstruction-rebonding circles. The all commercially available components, feasible preparation together with the excellent and recoverable performances suggest an industrializable resolution for the sustainability of environmental friendly WPU materials.