A 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.