Combustion behavior and physico-chemical properties of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50)

• TKX-50 enthalpy of formation proved to be much less than published values.
• TKX-50 is not an extremely powerful energetic material, surpassing common explosives.
• Decomposition of TKX-50 is determined by decomposition of constituent hydroxylamine.
• The burning of TKX-50 obeys the condensed-phase combustion mechanism.

The physico-chemical characterization (thermal decomposition under non- and isothermal conditions, enthalpy of formation, burning behavior and flame structure) of a new explosive dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate is detailed. Combustion studies have shown that TKX-50 burns slightly faster than HMX and approaches the burning rate of CL-20. The combustion of TKX-50 has been shown to obey mechanism with the leading reaction in the condensed phase. The rates of TKX-50 decomposition in both solid and liquid phases proved to be slightly higher than the corresponding rates of decomposition of RDX. Decomposition of TKX-50 is determined by decomposition of free hydroxylamine formed in the reaction of dissociation of the salt. An intermediate decomposition product is ammonium salt of 5,5′-bis(2-hydroxytetrazole), which further decomposes in the second stage at elevated temperatures. The enthalpy of formation of TKX-50 has been measured with the help of bomb calorimetry, however the resulting value is quite different from the enthalpy reported earlier.