In this study, a waterborne polyurethane (WPU) adhesive with self-healing and self-crosslinking capabilities was developed via an encapsulation-based strategy, exhibiting exceptional chemical and physical properties. The encapsulation system employed in this study utilized a furan-functionalized crosslinker in combination with an unsaturated WPU, enabling uniform dispersion under aqueous conditions. A reversibly cross-linked WPU adhesive was achieved, exhibiting remarkable recyclability and outstanding self-healing performance via the Diels–Alder (DA) reaction. Using dynamic light scattering (DLS) and transmission electron microscopy (TEM), it was confirmed that the crosslinker-containing synthesized WPU particles have a particle size of 150 nm with a narrow size distribution. The thermal and mechanical properties of the resulting films were investigated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile testing. The incorporation of the crosslinker led to a significant enhancement in mechanical performance. Notably, when the three-functionalized crosslinker (WPU3) was employed, the Young’s modulus increased markedly from 23 MPa to 81 MPa. Reversible cross-linked WPUs exhibit remarkable recyclability and a notable self-healing capability, achieving an initial tensile strength of up to 85 %. Due to its rich polar functionality, crosslinked WPU demonstrates robust bonding capabilities across a variety of substrates, including aluminum, steel, carbon steel, and epoxy composites. Thanks to specific structural design, the newly synthesized WPU showed reliable reusability, i.e., retaining 87 % of its original shear strength after multiple repair cycles. This study presents an effective method for self-curing WPU, enabling the development of high-performance, rapidly self-healing, and environmentally friendly adhesives.
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