Study on the effect of confined environment on thermal hazard potential of composite propellants and quantitative evaluation method

The thermal decomposition and combustion characteristics of solid composite propellants can vary significantly under different environmental pressures; however, a quantitative method for assessing their thermal hazards is lacking. This study investigates the thermal decomposition mechanisms of hydroxyl-terminated polybutadiene/ammonium perchlorate/aluminium powder (HTPB/AP/Al) and hydroxyl-terminated block copolyether/AP/Al (HTPE/AP/Al) propellants in varying environments. Using an accelerating rate calorimeter, the adiabatic decomposition characteristics of the two propellants were analysed. Laser ignition and closed bomb experiments were conducted to examine ignition and combustion under different pressures. A quantitative method for evaluating thermal hazard potential (THP) was established based on delay temperature and reaction intensity. Results indicate that the sealing conditions mainly change the nucleation factors of the two propellants in the third decomposition stage, making the nucleation factors of HTPB/AP/Al and HTPE/AP/Al propellants in the third stage change from 3/2 and 5/2–4 and 4/3, respectively. The lower T_start (264.16 ℃) and higher P_max (1.97 MPa) of HTPB/AP/Al compared to HTPE/AP/Al (280.31 ℃ and 1.21 MPa) suggest a higher thermal hazard for HTPB/AP/Al. A THP safety threshold of 0–20 % was identified. These findings provide essential insights for improving the thermal safety of propellants in practical applications.