Aging kinetics and performance degradation mechanisms of poly(glycidyl nitrate) before and after curing

Aging of energetic binders is a key factor limiting the long-term storage reliability of solid propellants. Poly(glycidyl nitrate) (PGN) is widely used in solid-propellant formulations because of its high energy content and compatibility with binder networks. In this study, the isothermal gas-evolution method was used to compare the aging kinetics of a PGN prepolymer and its polyurethane elastomer. Tensile testing, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy were used to examine the evolution of mechanical properties, thermal behavior, morphology, and chemical structure during aging. Model-fitting analysis assigned the PGN prepolymer to a reaction-order model with n = 1/4 and an apparent activation energy of 158.73 kJ·mol -1 . In contrast, the crosslinked polyurethane was better described by the Avrami-Erofeev equation and had an apparent activation energy of 140.33 kJ·mol -1 . The apparent activation energy of PGN-based polyurethane exhibits a conversion-dependent trend, rising to a maximum at α = 0.03–0.04 and subsequently declining, indicating a complex thermal degradation mechanism with overlapping reactions. With a degree of aging of 0.5% as the end-of-life criterion, PGN polyurethane has a storage life of 4.46 years at 25 °C. Thermal aging reduced the tensile strength of PGN polyurethane from 1.15 to 0.18 MPa, the elongation at break from 219.3% to 13.7%, and Tg by 6.4 °C. FTIR and SEM indicated that nitrate ester decomposition triggers urethane hydrolysis, chain scission, and crosslink network destruction, producing surface granules, micropores, cracks, and peeling, and thus severely compromising load-bearing capacity, extensibility, and long-term storage reliability. The results provide a theoretical and experimental basis for formulation optimization, processing control, aging-mitigation strategies, and storage-life assessment of PGN-based propellants, thereby supporting their engineering application.