Comparative Study of the Decomposition Mechanism and Kinetics of Biimidazole-Based Energetic Explosives

It is well known that imidazoles, possessing two or more nitro substituents, are potential candidates for highly energetic explosives with detonation parameters comparable to those of 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) and 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane. 4,4',5,5'-Tetranitro-2,2'-bi-imidazole (TNBI) is a typical imidazole explosive with energy equivalent to that of RDX but suffers from low sensitivity (impact sensitivity 7 J). 1,1'-Diamino-4,4',5,5'-tetranitro-2,2'-biimidazole (DATNBI), a derivative of TNBI, possesses two -NH₂ groups and has a higher detonation velocity (9063 m s^-1) and lower impact sensitivity of 15 J, which indicates great potential for future applications. Examination of the thermal decomposition mechanism and kinetics of TNBI and DATNBI gives a more comprehensive view of the influence that the -NH₂ group has on the sensitivity and storage safety of the energetic explosive-based TNBI molecular skeleton. Herein, the thermal decomposition mechanism is studied, showing that detachment of -NH₂ groups from DATNBI generates 1-diamino-4,4',5,5'-tetranitro-2,2'-biimidazole (ATNBI) and TNBI and induces self-decomposition. Although the decomposition peak temperature of DATNBI is significantly lower than that of TNBI at the same heating rate; its self-accelerating decomposition temperature (50 kg) is only 4 K lower. Therefore, the -NH₂ group displays good ability of reducing sensitivity but has no influence on storage safety of DATNBI.