Synergistic dual dynamic bonds for enhanced self-repair performance in HTPB binders

Energetic materials serve as critical energy sources for weapon systems and equipment. During manufacturing and storage processes, microcracks may form in these materials, posing significant safety risks. Self-healing materials capable of autonomously repairing microstructural damage have emerged as a promising solution to mitigate such hazards. Therefore, this study focuses on the self-healing property of hydroxyl-terminated polybutadiene (HTPB), a widely utilized binder in solid propellants. We develop a self-healing adhesive film (HP-SS) by reacting isocyanate-terminated polybutadiene (IPDI-HTPB-IPDI) with two dynamic chain extenders, bis(4-hydroxyphenyl)disulfide and bis(2-aminophenyl)disulfide. The optimized HP-SS exhibits exceptional healing efficiency of 96.0%. Through systematic optimization of chain extender content, a series of adhesive films with tunable hydrogen bond density and hard segment content are prepared. The synergistic effects of disulfide metathesis and hydrogen bonding on self-healing performance are comprehensively investigated, including the influence of healing duration, temperature, and molecular mobility. This work proposes a novel strategy for regulating HTPB-based self-healing systems by balancing soft/hard segment ratios and hydrogen bond interactions, providing insights for designing high-performance energetic composites. By introducing the chain extenders bis(4-hydroxyphenyl) disulfide and bis(2-aminophenyl) disulfide into the hydroxyl-terminated polybutadiene (HTPB) binder system, a synergistic dual dynamic mechanism, hydrogen bonding coupled with disulfide metathesis, is established, thereby improving self-healing performance. We develop an HTPB self-healing binder that couples disulfide metathesis with hydrogen bonding, delivering markedly improved mechanics over unmodified films and up to 96% healing after 48 h at 80 °C.