Thermal behavior of 1,3,5-trinitroso-1,3,5-triazinane and its melt-castable mixtures with cyclic nitramines

Abstract Mixtures of 1,3,5-trinitroso-1,3,5-triazinane (TMTA) with 1,3,5-trinitro-1,3,5-triazinane (RDX), cis-1,3,4,6-tetranitro-octahydroimidazo-[4,5-d]imidazole (BCHMX) and ε-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), respectively, have been investigated by DSC and TGA techniques. It has been found that there are two endothermic peaks at about 96 °C and 107 °C, due to polymorphic transition and melting of TMTA, whereas only small endothermic peaks were observed in the temperature region of 92.8-95.0 °C for mixtures of RDX-TMTA, BCHMX-TMTA and CL-20-TMTA. These differences in exothermic temperatures of the pristine TMTA versus its mixtures could be a result of co-crystals formation. Moreover, only one complex step for decomposition of TMTA and RDX-TMTA was observed, while at least two steps were found for BCHMX-TMTA and CL-20-TMTA mixtures. TGA measurements showed that a mass loss of TMTA begins at 89.3 °C and has a peak temperature of 185.9 °C. In contrast, the mass loss of RDX-TMTA mixture begins at 142.9 °C and has a peak temperature of 227.6 °C, evidently showing a behavior of a single compound. On the other hand, the activation parameters for the first step decomposition of the BCHMX-TMTA (2.355 J g^-1) and CL-20-TMTA mixtures were found to be very close to that of TMTA (1.320 J g^-1), strongly indicating that most probably TMTA undergoes decomposes during the first decomposition steps of these mixtures.