Comparative thermal research on chlorodinitromethyl and fluorodinitromethyl explosophoric groups based insensitive energetic materials

The introduction of highly oxidative explosophoric groups is an efficient strategy to enhance the detonation properties of energetic materials due to its improvement effect of oxygen balances. Chlorodinitromethyl and fluorodinitromethyl groups are widely applied as oxygen-rich building blocks for the construction of energetic materials and their combinations with FOX-7 derived 1,3,5-tetrahydrogentriazine backbone provide perfect structures for a systematic and comparative thermal study of these two similar explosophoric groups. Decomposition behaviors of the obtained insensitive energetic materials were investigated through DSC-TG approaches and chlorodinitromethyl based one exhibited sharper exothermic peak shape and higher heat release rate. Non-isothermal kinetics of the thermal decomposition was achieved based on DSC experiments under different heating rates, showing an observable melting process which could only be observed from the chlorodinitromethyl group based energetic structure under high the heating rates. Possible mechanism of the thermal decomposition was proposed by exploring the intermediates during the heating process through the combination of in-situ FTIR spectroscopy technology with calculation methods, which proved that the decompositions were triggered by the cleavage of nitro groups in chlorodinitromethyl and fluorodinitromethyl moieties. Despite their effectiveness to improve the energy density levels, this study showed the chlorodinitromethyl and fluorodinitromethyl explosophoric groups can also interact with the backbones under high temperatures, especially with the ones with active N-H moieties, and result in low decomposition temperatures which may greatly limit their applications.