Thermo-analytical study of cis-1,3,4,6-tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX) and 1,1-diamino-2,2-dinitroethene (FOX-7) in comparison with a plastic bonded explosive based on their mixture

The thermal behavior and decomposition kinetics of a new plastic bonded explosive (PBX) based on mixture of bicyclic nitramine, cis-1,3,4,6-tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX) with insensitive explosive, 1,1-diamino-2,2-dinitroethene (DADNE or FOX-7) bonded by polydimethylsiloxane (PDMS) binder (44/44/12 wt%) have been investigated. For comparison, the individual materials, FOX-7 and BCHMX in addition to their mechanical mixture have been studied. Nonisothermal TG and DSC techniques were used and the decomposition kinetics were obtained by the isoconversional methods (Kissinger and modified Kissinger-Akahira-Sunose (KAS) methods). Scanning electron microscope (SEM) was used to study the morphology changes of BCHMX and FOX-7 crystals after heating isothermally at 210 °C for 5 min. Regarding to the studied PBX, It was found that the mechanism of thermal degradation of both the individual explosives is changed; the decomposition of pure BCHMX was shifted in the mixture and the second peak of the FOX-7 was merged with the peak of decomposition of their PBX. The thermo-analytical study shows also certain instability of PDMS binder over 190 °C in presence of FOX-7 and decomposition of FOX-7 as a solution in the degradation products of this binder in temperature region typical for thermal decomposition of BCHMX. Nevertheless, the PDMS matrix seems to be a good binder for this mixture, filled by BCHMX and FOX-7, due to its good thermal stability in temperature regions enterable for practical military applications.