Construction of a novel GAP/PCL energetic self-healing blend adhesive system for propellants based on the synergistic effect of hydrogen bond reorganization and disulfide bond exchange reactions

Abstract

Solid propellants are essential for rocket engine efficiency and safety. The introduction of energetic self-healing adhesives can improve its energy density, mechanical properties, and safety, while extending its service life. Therefore, this paper proposes a novel energetic self-healing adhesive that utilizes asymmetric alicyclic isophorone diisocyanate (IPDI) and 2-(aminophenyl) disulfide (2-AFD), which has a bent biphenyl ring structure, as hard segments, combined with semicrystalline polymer polycaprolactone (PCL) and energetic adhesive glycidyl azide polymer (GAP) as soft segments to synthesize a series of self-healing adhesives. By adjusting the hard segment content, a balance between mechanical properties and self-healing performance is achieved. Results show that increasing the hard segment content enhances toughness (from 26.60 MJ·m⁻³ to 58.54 MJ·m⁻³), but decreases self-healing efficiency (from 90 % to 58 %). GPPU-2 exhibits 38.95 MJ·m⁻³ toughness and recovers 86 % of its toughness within 90 min at 80 °C via dynamic disulfide and hydrogen bond interactions. The GPPU-2-based propellant, GPPU80, recovers 88.22 % of tensile strength after 24 h at 80 °C, demonstrating effective crack propagation inhibition. Compared to inert adhesive-based propellants, GPPU80 shows superior combustion performance and energy release. This study offers insights for designing high-performance self-healing adhesives to enhance propellant safety and energy density.