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    • TATB based PBXs formulations such

    2018-11-12

    TATB based PBXs formulations such as LX-17 and PBX 9502 [18–21] have been developed for nuclear bomb, missiles and space applications. TATB has a high thermal stability, insensitive in terms of impact and friction but poor performance. The performance of formulations has been enhanced either to use new explosive molecule having better performance than TATB or admixture of high energetic materials which has a high performance and comparatively less sensitive to ensure the safety parameters [22–24]. Therefore, PBXs based on HMX and TATB have been formulated with polymer matrices; Estane, Viton A and Kel-F 800 to some extent compromise with insensitivity [25,26]. These formulations have been characterized in terms of density, detonation velocity, ignition temperature and other explosive properties which are covered under few reports and in paper also [27–37]. The thermal decomposition behaviour and kinetics are very important because it ensures safety parameters during handling, processing, production and storage [38–40]. PBXs based on HMX or TATB have been extensively investigated for the thermal decomposition behaviour and its kinetics [41–44] by means of non-isothermal thermogravimetry (TGA) and differential scanning calorimetry (DSC). The kinetic parameters of HMX based PBXs with Viton A [45], C4 [46], Formex [47] and Semtex [48,49] have been investigated and published. Brunham and Weese [50] have investigated the kinetics of PBXs with three buy Anisomycin binders; Estane 5703, Viton A and Kel-F 800 by performing TG measurements at different heating rates, exhibited that Viton A and Kel-F 800 were more thermally stable than HMX and TATB. Craig et al. [51] have been studied thermal behaviour of PBXs based on HMX or TATB with same endothermic binders, exhibited longer times to thermal explosion than those of pure HMX or TATB in the one-dimensional time to explosion and in other thermal experiments [52,53]. Moreover, the decomposition kinetic models with different polymeric matrices have been published as both kinetic parameters and reaction models are the key factor for the prediction of the thermal hazard properties. It has been reported that the effect of the polymer matrices on the decomposition mechanism has been significantly observed and resulting in very different reaction models. Tarver and Tran have also been measured the decomposition models to predict of explosion and the locations within the explosive charges [54]. However, the thermal decomposition behaviour and kinetics of PBXs based on mixture of TATB and HMX with Viton A are less addressed in an open literature. In our previous study [55], the mechanical and explosive properties of PBXs based on mixture of HMX and TATB have been investigated and published.
    Experimental
    Results and discussion
    Conclusions In the present study, the thermal properties such as Tg, Tm and thermal decomposition were investigated for PBXs based on mixture of HMX and TATB with Viton A using STA and DSC. The results indicate that 9–72% weight loss was occurred in the first step due to thermal decomposition of HMX. It was also found that weight loss was increased with increasing HMX amount. TGA indicated that Tonset and Tmax values were slightly increased with increasing HMX amount. These results suggested that the HMX, TATB and Viton A were thermally stable and compatible with each other. The activation energies were ranged from 524 to 1219 kJ/mol, and the natural logarithm of pre-exponential factor were ranged from 104.4 to 261.4 s−1 for a single heating rate measurement under non-isothermal condition. The activation energy was significantly increased with increasing the HMX amount in the first step thermal decomposition. The kinetics were also investigated by using FWO and KAS methods. The TGA indicated that the decomposition of HT4050 was occurred in distinct steps at multiple heating rates under non-isothermal condition. The results indicated that activation energies were 1290 to 1050 kJ/mol at conversion of 0.1–0.45, whereas at conversion of 0.65–0.8, the activation energy was ranged from 81.4 to 156.3 kJ/mol, and the third step decomposition the activation energy was attributed to 130 and 186.1 kJ/mol at conversion of 0.85 and 0.9 respectively by FWO method. The activation energy calculated by both FWO and KAS methods was close to each other. The mean activation energy was also a good agreement with a single heating rate measurement in the first step decomposition.