Reactivity of polyaniline composites with attractive cyclic nitramines

Abstract

Composite microcrystals of the nitramines (NAs) viz., RDX, HMX, BCHMX, and CL-20 with electrically conductive polyaniline (PANi) are a charge transfer complexes in coagglomerated composite crystals (CACs). The activation energies of thermolysis, E_a, of the pure NAs and their PANi-CACs were determined using the Kissinger method, and decomposition processes are discussed. Except for the RDX/PANi CACs, all the other CACs show higher E_a values for decomposition compared to their pure NA counterparts. For all CACs, relationships are specified between the E_a values, on the one hand, and the squares of the detonation velocities, enthalpies of formation, spark energy and impact sensitivities, on the other. The relationships between their low-temperature heats of decomposition, ΔH, from DSC, and their enthalpy of formation, logarithm of impact sensitivity, electric spark energy, as well as detonation energy, are described. The PANi favorably influences the density of the corresponding CACs; surprisingly close linear correlations were found, and explained, between these densities and the E_a values. This presence of PANi strongly increased the electrical spark sensitivity of the CACs in comparison to the base NAs. Based on the results obtained, it can be noted in particular the exceptional desensitization of HMX to impact and the increased sensitivity to electrical spark by coating its crystals with polyaniline.