Calculation of Decomposition Products from Components of Gunpowder by using ReaxFF Reactive Force Field Molecular Dynamics and Thermodynamic Calculations of Equilibrium Composition

Abstract

The major combustion products from munitions containing nitro‐based propellants are water, carbon monoxide, carbon dioxide, hydrogen, and nitrogen. In addition, compounds including hydrogen cyanide, ammonia, methane, nitrogen oxides, benzene, acrylonitrile, toluene, furan, aromatic amines, benzopyrene, and various polycyclic aromatic hydrocarbons are detected in minor concentrations. The literature shows that the thermodynamic prediction of the major decomposition products agrees fairly well with the measurements. However, poor agreement is found for the minor species. We have studied the thermal decomposition products of the main gunpowder ingredients. Each of the components nitrocellulose, nitroglycerine, and the nitrate ester stabilizers diphenylamine and ethyl centralite were thermally decomposed with ReaxFF reactive force field molecular dynamics and equilibrium thermodynamics. The molecular dynamics results for the major decomposition products from nitrocellulose were partly consistent with measurements. Compared to the thermodynamic calculations, the molecular dynamics simulations agreed considerably better with experimental results for minor species like hydrogen cyanide. The nitrate ester stabilizers are the main sources for ammonia and aromatic combustion products, whereas hydrogen cyanide is produced from nitrocellulose as well as from the stabilizers when gunpowder is combusted.

Pyrolysis/GC/MS as a Method to Rapidly Profile Pyrotechnic Formulations for Objectionable Gaseous Emissions

“…Of further note, low combustion temperature formulations which use such polymeric ingredients (e.g., smoke formulations) may produce more of these VOCs than other higher combustion temperature formulations . Thus, it may be concluded that these calculations are useful but inadequate when considering these nonequilibrium products, such as volatile organic compounds (VOCs), which are known to be produced via the thermal degradation of common polymeric ingredients in pyrotechnic compositions …”

“…42 Thus, it may be concluded that these calculations are useful but inadequate when considering these nonequilibrium products, such as volatile organic compounds (VOCs), which are known to be produced via the thermal degradation of common polymeric ingredients in pyrotechnic compositions. 43 It is clear that a tremendous molecular diversity results from the thermal degradation of polymeric materials within a pyrotechnic reaction. This work demonstrates that new pyrotechnic development should consider utilizing analytical techniques that can capture and assess new byproducts that are…”

The adsorption characteristics and degradation mechanism of tinidazole on an anatase TiO2 surface: a DFT study

“…Then we adopted the ReaxFF force field for molecular dynamics simulations. 30 The system is first heated to 300 K with repeated velocity rescaling methods and then followed by a 10 ps NVE molecular simulations. 31 The time step and the total simulation time are 0.1 fs and 10 ps respectively.…”

Transformation of Combustion Nanocatalysts inside Solid Rocket Motor under Various Pressures

“…For the same AP/HTPB system, three different reaction mechanisms have been proposed and simulated, which are based on the global chemistry using symbolic species for the three flames, a 12-species mechanism, and a 72-step reaction mechanism with 39-species, respectively [11]. Except for the numerical simulations, the chemical structure of the propellant flame could be predicted by ReaxFF reactive force field molecular dynamics and equilibrium thermodynamics simulations [12]. It has been found that the ReaxFF agrees considerably better with experimental results for minor species than the thermodynamic simulations.…”