Preparation and performance of a HNIW/TNT cocrystal explosive

A novel cocrystal explosive composed of 2,4,6,8,10,12-hexanitrohexaazaiso- wurtzitane (HNIW) and 2,4,6-trinitrotoluene (TNT) in a 1: 1 molar ratio was effectively prepared by solvent/nonsolvent cocrystallization adopting dextrin as modified additive. The structure, thermal behavior, sensitivity, and detonation properties of HNIW/TNT cocrystal were studied. The morphology and structure of the cocrystal were characterized by scanning electron microscopy (SEM) and single crystal X-ray diffraction (SXRD). SEM images showed that the cocrystal has a prism type morphology with an average size of 270μm. SXRD revealed that the cocrystal crystallizes in the orthorhombic system, space group Pbca, and is formed by hydrogen bonding interactions. The properties of the cocrystal including sensitivity, thermal decomposition, and detonation performances were discussed in detail. Sensitivity studies showed that the cocrystal exhibits low impact and friction sensitivity, and largely reduces the mechanical sensitivity of HNIW. DSC and TG tests indicated that the heterogeneous exothermic decomposition of the cocrystal occurs in the temperature range from 170 °C to 265 °C with peak maxima at 220 °C and 250 °C and significantly increases the melting point of TNT by 54 °C. The cocrystal has excellent detonation properties with a detonation velocity of 8426m s^-1 and a calculated detonation pressure of 32.3MPa at a charge density of 1.76g cm ^-3, respectively. Moreover, the results suggested that the HNIW/TNT cocrystal not only has unique performance itself, but also effectively alters the properties of TNT and HNIW. Therefore, the cocrystal formed by HNIW and TNT could provide a new and effective method to modify the properties of certain compounds to yield enhanced explosives for further application.