Insight into HTPB pyrolysis mechanism under high-temperature: A reactive molecular dynamics study

Hydroxyl-terminated polybutadiene (HTPB) is widely utilized in solid and hybrid rocket propellants due to its mechanical properties and combustion performance. Insight into its pyrolysis process is key to enhancing combustion efficiency in rocket engines. This study employs ReaxFF molecular dynamics (MD) simulations to explore the pyrolysis mechanism of HTPB under extreme conditions, with temperatures ranging from 1000 K to 2000 K. The results identify the primary degradation products and elucidate their formation mechanisms. The simulation reveals that C-C bond cleavage at polymerization sites is the initial step, followed by the formation of linear oligomers and butadiene. Subsequent reactions, including hydrogenation and dehydrogenation, lead to the generation of smaller molecular species. The kinetic analysis confirms that HTPB pyrolysis follows first-order reaction kinetics, with an activation energy of 8.12 kcal/mol. The findings are compared with existing experimental data, highlighting the influence of thermal environments on pyrolysis mechanisms and product distributions.