Thermal Decomposition of 1,3,5,5‐Tetranitrohexahydro‐Pyrimidine: A New Type of Autocatalysis that Persists at High Temperatures

Abstract The thermal stability of 1,3,5,5‐ tetranitrohexahydropyrimidine (TNDA) in liquid phase under isothermal conditions was studied. It was established that the TNDA decomposition (kliq=3.1 ⋅ 1021⋅exp(−26865/T), Ea=223.4 kJ mol−1) is accompanied by strong autocatalysis (kcat=9.8 ⋅ 1014⋅exp(‐18056/T), Ea=150.2 kJ mol−1). The mechanism of autocatalysis was proposed. The essence of autocatalysis is the oxidation of TNDA by decomposition products, followed by the destruction of the molecule. An unusual feature of this autocatalysis is that, in contrast to autocatalysis of nitroesters, the process does not disappear at high temperatures, but rather determines the kinetics of heat release in the combustion wave. The surface temperature and combustion mechanism of TNDA were established through thermocouple studies. It was shown that the autocatalysis reaction at the surface temperature controls the burning rate.