Promising Thermally Stable Energetic Materials with the Combination of Pyrazole–1,3,4-Oxadiazole and Pyrazole–1,2,4-Triazole Backbones: Facile Synthesis and Energetic Performance
Abhishek Kumar Yadav, Vikas D. Ghule, Srinivas Dharavath
Abstract
Thermally stable energetic materials have broad applications in the deep mining, oil and natural exploration, and aerospace industries. The quest for thermally stable (heat-resistant) energetic materials with high energy output and low sensitivity has fascinated many researchers worldwide. In this study, two different series of thermally stable energetic materials and salts based on pyrazole–oxadiazole and pyrazole–triazole (3–23) with different explosophoric groups have been synthesized in a simple and straightforward manner. All the newly synthesized compounds were fully characterized by IR, ESI-MS, multinuclear NMR spectroscopy, elemental analysis, and thermogravimetric analysis–differential scanning calorimetry measurements. The structures of 3, 7, and 22 were supported by single-crystal X-ray diffraction studies. The density, heat of formation, and energetic properties (detonation velocity and detonation pressure) of all the compounds range between 1.75 and 1.94 g cm–3, 0.73 to 2.44 kJ g–1, 7689 to 9139 m s–1, and 23.3 to 31.5 GPa, respectively. All the compounds are insensitive to impact (>30 J) and friction (>360 N). In addition, compounds 4, 6, 10, 14, 17, 21, 22, and 23 show high onset decomposition temperature (Td between 238 and 397 °C) than the benchmark energetic materials RDX (Td = 210 °C), HMX (279 °C), and thermally stable HNS (318 °C). It is noteworthy that the pyrazole–oxadiazole and pyrazole–triazole backbones greatly influence their physicochemical and energetic properties. Overall, this study offers a perspective on insensitive and thermally stable nitrogen-rich materials and explores the relationship between the structure and performance.