Molecular dynamics simulation study on the aging process of RDX/HTPB propellants at different temperatures

During the long-term storage of RDX/HTPB propellants, slow aging frequently occurs, resulting in irreversible alterations such as internal structural distortion, diminished stability, impaired mechanical properties, and sudden changes in the burning rate. In extreme cases, unintended ignition or spontaneous combustion might occur, posing safety hazards during use. A deep understanding of the microscopic decomposition mechanisms of RDX/HTPB propellants is key to ensuring operational stability and reliability. Using the ReaxFF/lg reactive force field, molecular dynamics simulations of the RDX/HTPB propellant aging process at different temperatures were conducted. Changes in the potential energy, species evolution, reaction pathways, and product distribution patterns were analyzed. The MD results indicate that the lower the temperature is, the lower the aging rate. When the temperature exceeds 1000 K, the aging rate exponentially increases with increasing temperature. The aging process begins with the cleavage of N−NO 2 bonds in RDX. The reaction products primarily consist of intermediates, final products, and some large carbon-containing clusters. The fitted activation energy was determined to be 85.59 kJ/mol, with a predicted storage life of 23.56 years at 20°C. The storage life of the propellant is negatively correlated with temperature, indicating that low-temperature environments are beneficial for extending the storage duration of the propellant.