Delving into Autocatalytic Liquid-State Thermal Decomposition of Novel Energetic 1,3,5-Triazines with Azido, Trinitroethyl, and Nitramino Groups

Abstract

Thermal decomposition of 1,3,5-triazines with azido, trinitroethyl, and nitramino groups, the three important energetic functionalities, has been studied with a range of thermal analysis tools. The involved compounds melt under heating with the following mass loss and heat and gas release in the course of thermal decomposition. Model-fitting kinetic analysis resulted in formal reaction schemes with two general stages. In case of the least energetic 6-azido-2,4-bis(2,2,2-trinitroethylamino)-1,3,5-triazine, the first reaction is a first-order reaction followed by a thirdorder reaction. Alternatively, for 6-azido-2,4-bis(2,2,2-trinitroethylnitramino)-1,3,5-triazine and 2,4,6-tris(2,2,2-trinitroethylnitramino)-1,3,5-triazine, the first step comprises the autocatalytic reaction. The activation energy for the first decomposition step drops from 141 to 122 kJ mol −1 due to the inductive influence of a β-nitramino group. The second general reaction for all species obeys the third-order reaction model with activation energies in the range 112−126 kJ mol −1 . On the basis of the analysis of the kinetic data and temporal behavior of the evolved gases, a similar primary decomposition channel, the homolytic cleavage of a C− NO 2 bond, has been proposed for all investigated substances.

Thermal stability of emerging N6-type energetic materials: kinetic modeling of simultaneous thermal analysis data to explain sensitivity trends

“…The ratio between the rate constants in the liquid and solid state, also known as the retardation coefficient K T , for a range of compounds is near two orders, i.e., K T = k liq /k sol E 100 AE 50. 47,48 To account for this increase, in previous work 49 we have introduced in the formal kinetic model the triggering temperature T*. This temperature is selected near the minimum of the DSC curve, where the negative signal rapidly changes to a positive one, and for a selected reaction step the preexponential factor below T* is reduced 100 times to imitate the retardation by the crystal lattice.…”

“…It is interesting to probe eqn (5) with the experimental kinetic data obtained in this study. To analyze more compounds, we consider also various energetic compounds for which we have obtained the kinetic data in the melted state, i.e., 6-azido-2,4-bis(2,2,2trinitroethylamino)-1,3,5-triazine (TEAT), 49 6-azido-2,4-bis-(2,2,2-trinitroethyl)nitramino-1,3,5-triazine (NTEAT), 49 tetranitroacetimidic acid (TNAA), 51 bis-(2-difluoroamino-2,2-dinitroethyl)nitramine (B2DFEN), 27 3,5-dinitropyrazole (35DNP), 75 ammonium dinitramide, 16 picric acid (PA), 76 and 1,3,5-trinitro-1,3,5-triazinane (RDX). 77 We analyzed the friction sensitivity data, as they were previously shown to be less disturbed by powder properties and impact and flow conditions, 64 and since it takes less amount of material to test compared to impact tests.…”