Tough, Self-Healing Polyurethane Binder Constructed Using Multilevel Hydrogen-Bonded Networks for Composite Solid Propellants

A polyurethane (PU) binder with high mechanical strength and effective self-healing capacity at moderate temperatures is essential for improving the safety of composite solid propellants. Herein, we developed a fluorinated ureido-4-[1H]-pyrimidinone polyurethane (FUPU) binder by functionalizing hydroxy-terminated polybutadiene-based PU with multilevel hydrogen bonds introduced through ureido-4-[1H]-pyrimidinone and fluorinated segments from hexadecyl fluoro-1,10-decanediol. These dynamic hydrogen bonds facilitated bond dissociation/recombination and energy dissipation, imparting FUPU with a tensile strength of 1.14 MPa, an elongation at break of 1066%, and a self-healing efficiency of 93.5% after 8 h at 60 °C. Composite solid propellants (SP-2) prepared using FUPU, ammonium perchlorate, and aluminum powder exhibited enhanced mechanical properties and achieved a self-healing efficiency of 78.11% after 8 h at 60 °C. Furthermore, the fluorinated segments reduced aluminum agglomeration during combustion, increasing the burning rate by 31.6% at 3.0 MPa. Collectively, these results offer a viable strategy for designing high-performance composite solid propellants.