A room temperature self-healing and thermally reprocessable cross-linked elastomer with unprecedented mechanical properties for ablation-resistant applications

High-performance ablative composites demonstrate promising applications in the field of aerospace for thermal protection. In this work, a mechanically strong, fast room temperature self-healing and thermally recyclable crosslinked elastomer was prepared by constructing high-density hydrogen bonds and dynamic disulfide bonds. The tensile strength of the prepared poly(urea-urethane) elastomers (PIDA) reached as high as 31.0 MPa after self-healing for 48 h at room temperature, exhibiting a self-healing efficiency of 93.6%. The PIDA-based composite with 10 wt% hollow phenolic microspheres possessed a tensile strength of 8.67 MPa and exceptional ablative performance with a line ablation rate of 0.0643 mm/s. The extraordinary mechanical properties of PIDA-based materials were related to the presence of reversible disulfide bonds, meticulously engineered hydrogen bonds and chemical cross-linking sites consisting of 2,4-diamino-6-hydroxypyrimidine (DAHP) and urethane moieties that linked by flexible alicyclic hexatomic spacers. Incorporating DAHP allowed the rapid formation of hydrogen bonds at the crosslinking sites, which increased the interaction force of the repair surface during the initial stages of self-healing and provided support for further exchange reactions of disulfide bonds. This work opens an avenue toward developing ultra-robust room temperature self-healing materials for potential thermal protection in aerospace industry.