Thermal Decomposition Characteristics and Thermal Safety of Dihydroxylammonium 5,5′-Bistetrazole-1,1′-diolate Based on Microcalorimetric Experiment and Decoupling Method

A microcalorimeter (C600) was used to conduct dynamic heating experiments on dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50), and the results were compared with those of differential scanning calorimetry (DSC). The effect of mass scale on the thermal decomposition characteristics of TKX-50 was also analyzed. The thermal decomposition curves were decoupled by mathematical method, and the kinetic parameters of each step were obtained. The thermal decomposition characteristics of TKX-50 were further analyzed by thermal history and isothermal experiment, and the thermal safety parameters were calculated by thermal analysis software (AKTS). The decomposition temperature and decomposition enthalpy of TKX-50 in the microcalorimetric experiment were higher than the corresponding parameters in the DSC experiment, and the apparent activation energy was lower than the one in the DSC experiment. When the times to maximum rate under adiabatic conditions were 2.0, 4.0, 8.0, and 24.0 h, the corresponding temperatures were 198.5, 189.6, 181.0, and 168.0 °C, respectively. After decoupling, the range of exothermic peak temperature and decomposition enthalpy of the first and second stages of TKX-50 were 226.9–245.3 and 276.3–295.7 °C and 1300.7 and 727.7 J g^–1, respectively, and the apparent activation energy of the second stage was higher than that of the first stage. The thermal history reduced the decomposition temperature and the apparent activation energy of TKX-50, the safety was reduced, and this had a great influence on the thermal decomposition kinetics of TKX-50. Thermal history and isothermal experiment showed that the first stage decomposition reaction of TKX-50 has autocatalytic properties. Therefore, it should be prevented from being placed in an adiabatic environment, and it is necessary to avoid the storage of a large mass of TKX-50 and keep the heat source off the storage location in the process of industrial production and storage, so as to prevent the formation of adiabatic environments and thermal history in the interior and further reduce the risk of explosion in TKX-50.