Trinitropyrazole derivatives: The features of thermal decomposition, combustion behaviors and mechanism

Abstract

The kinetics and mechanism of thermal decomposition of high-energy 3,4,5-trinitro-1H-pyrazole (TNP) and 1-methyl-3,4,5-trinitro-1H-pyrazole (MTNP) and the combustion behaviour of these compounds were investigated. The thermal stability of the nitropyrazoles was determined using both differential scanning calorimetry and an isothermal manometric method. The experiments demonstrated that the isomerisation step of the nitro group, previously hypothesised to play a significant role in the TNP decomposition process, does not have a substantial impact. Based on the burning rate experiments and thermocouple measurements, the decomposition kinetics of TNP and MTNP were obtained over a wide temperature range. The kinetic parameters of TNP and MTNP decomposition (activation energies of 155.4 kJ/mol and 164.2 kJ/mol and log (A, s^-1) values of 13.06 and 14.00, respectively) were found to be more indicative of the nitro group detachment reaction than the intramolecular oxidation of carbon by oxygen of the nitro group. The leading combustion reaction occurs in the molten layer at the boiling point and its rate is consistent with the kinetics of the initial stages of TNP and MTNP decomposition. The temperature dependence of the vapour pressure of the trinitropyrazole derivatives was determined. The kinetic data obtained were used to make thermal safety predictions for the trinitropyrazole derivatives.