Engineering self-healing and flame-retardant polyurethane elastomers via phosphaphenanthrene functionalization and hydrogen bond network design

Self-healing polymers, polyurethane (PU) elastomers, demonstrate immense application potential due to their remarkable ability to prolong material lifespan and conserve resources. Nevertheless, resolving the conflict between self-healing capacity, mechanical strength, and high flammability remains a pressing challenge for these materials. Furthermore, the inherently high flammability of PU materials poses serious fire hazards, severely limiting their practical applications. To address these challenges, a novel flame-retardant and self-healing PU elastomer was developed by incorporating a bio-based monomer, GVD containing phenolic hydroxyl groups and phosphaphenanthrene moieties and adipic dihydrazide into the PU backbone. The resulting elastomer exhibited excellent tensile strength (12.11 MPa) and high toughness (58.56 MJ/m³), attributed to the multiple extensive hydrogen bonding interactions within the molecular chains. Following thermal healing at 80 °C for 5 h, the material achieved a healing efficiency exceeding 95 %. Additionally, compared to the non-flame-retardant IPDG-0, the flame-retardant IPDG-0.5 displayed a 50.6 % reduction in peak heat release rate and a 16.3 % decrease in peak carbon monoxide emission rate, confirming its improved flame retardancy. This research not only advances the synthesis of multifunctional PU elastomers but also provides a valuable strategy for developing self-healing materials with intrinsic flame retardancy, thereby expanding their potential applications.