Recent Advances in the Study of the Initiation of Energetic Materials using Characteristics of Their Thermal Decomposition Part I. Cyclic Nitramines

Arrhenius parameters, Ea and log A, of 17 cyclic nitramines, derived from the Russian vacuum manometric method (SMM) and compatible thermoanalytical methods, have been used in this study. The detonation velocity, D, at maximum theoretical crystal density, of the nitramines in this study was taken as a characteristic of their detonation. On the basis of known relationships between their E-a and D-2 values (modified Evans-Polanyi-Semenov equation), the specific influence of some physicochemical properties on their thermal decomposition was shown. A new logarithmic relationship was found between the rate constant k, of the unimolecular thermal decomposition of the nitramines studied at 230 degrees C, and their D values. A fundamental characteristic of this new relationship rests on the equivalency of the primary fission processes in the low-temperature thermal decomposition and on the detonation initiation of the nitramines understudy. Both these relationships confirm the problems encountered in the kinetic specification of the thermal decomposition of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW, CL-20) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX). These problems, and also the possible influence of the pre-decomposition states on the thermal decomposition of the nitramines studied, are discussed.