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Concerning the shock sensitivity of cyclic nitramines incorporated into a polyisobutylene matrix

Pelikán W., Zeman S., Yan Q. L., Erben M., Elbeih A., Akštein Z.

Central European Journal of Energetic Materials

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2014

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Vol. 11, no. 2

219--235

EN

Two types of plastic bonded explosives (PBXs) based on ε-2,4,6,8,10,12hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (ε-HNIW, CL-20), and PBXs based on 1,3,5-trinitro-1,3,5-triazinane (RDX), β-1,3,4,7-tetranitro-1,3,5,7-tetrazocane (β-HMX) and cis-1,3,4,6-tetranitro-octahydroimidazo-[4,5-d]imidazole (bicycloHMX, BCHMX) were prepared using a polyisobutylene binder with dioctylsebacate (DOS) as plasticizer, i.e. a C4 matrix. One version of the ε-HNIW PBX is a product with reduced sensitivity (RS-ε-HNIW). All these PBXs, referenced respectively as RS-ε-HNIW-C4, ε-HNIW-C4, RDX-C4, HMX-C4 and BCHMX-C4, were tested using the Small Scale Gap Test according to STANAG 4488. The results of the gap test on the PBXs with RDX, β-HMX and BCHMX correspond to the impact sensitivities of the original crystalline nitramines. This is not entirely valid for ε-HNIW. In other words, PBXs with RS-ε-HNIW cannot achieve as low a shock sensitivity as would be expected from the differences obtained from the impact sensitivities between RDX, β-HMX and BCHMX, on the one hand, and RS-εHNIW on the other. It is shown that the morphological stability of RS-ε-HNIW in the C4 matrix is insufficient. However, further development and use of RS-ε-HNIW as a filler of PBXs would seem to be both desirable and beneficial. Despite the relatively high impact sensitivity of crystalline BCHMX, the shock sensitivity of its analogous C4 PBX is already good, and comparable with that of RS-ε-HNIW.

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Some Relationships Among Thermal Properties, Detonation Parameters and Sensitivity of Nitramine Fillers in Formex Based PBXs

Yan Q. L., Zeman S., Elbeih A.

Problemy Mechatroniki : uzbrojenie, lotnictwo, inżynieria bezpieczeństwa

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2013

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Vol. 4, Nr 2 (12)

7-17

EN

Thermal behavior and decomposition kinetics of formex-bonded on some attractive cyclic nitramines (BCHMX, HMX, RDX and CL-20) were investigated by means of nonisothermal Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC). Besides, their detonation parameters have been calculated by EXPLO 5 code. It was found that the effect of formex polymer base on thermal decomposition of HMX is different from other cyclic nitramines, namely, the formex base could increase the activation energy of HMX while decrease that of others. Besides, the logarithm of volume heat of detonation for formex based explosives is linearly dependent on their time constant of initiation. Furthermore, on one hand, except for RDX, the heat of detonation decreases with the increase of activation energy, and the spark energy and impact energy of cyclic nitramine fillers decreases with the increase of the critical temperature of their PBXs. On the other hand, except for HMX, the rate constant of PBXs is linearly dependent on the impact sensitivity of their pure nitramine fillers.

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The Influence of the Semtex Matrix on the Thermal Behavior and Decomposition Kinetics of Cyclic Nitramines

Yan Q. L., Zeman S., Elbeih A., Zbyněk A.

Central European Journal of Energetic Materials

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2013

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Vol. 10, no. 4

509--528

EN

The thermal behavior and decomposition kinetics of Semtex 10 polymeric matrix (Semtex) bonded PBXs containing RDX (1,3,5-trinitro 1,3,5-triazinane), HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane), BCHMX (cis-1,3,4,6tetranitrooctahydroimidazo [4,5-d] imidazole), HNIW (2,4,6,8,10,12-hexanitro2,4,6,8,10,12-hexaazaisowurtzitane) have been investigated by means of nonisothermal TG and DSC techniques. It is shown that only a single decomposition process occurs for RDX-SE and HMX-SE whilst an obvious two-step process occurs for CL-20-SE and BCHMX-SE. The onset of the exotherms were observed at 210.6, 239.7, 279.2 and 229.4 °C with the peak maxima at 232.2, 249.4, 280.4 and 240.2 °C, and energy changes of 1808, 2140, 612 and 1757 J·g-1 for RDX-SE, BCHMX-SE, HMX-SE and CL-20-SE, respectively. It has been found that the Semtex matrix has little influence on the activation energy distribution for RDX, BCHMX and ε-CL-20. The activation energies for BCHMX-SE and CL-20-SE decomposition are almost independent of the degree of conversion, with mean values of 159.6 ±1.9 and 187.3 ±1.8 kJ·mol-1. It has been proved that Semtex and Viton A are better binders than C4 and Formex for ε-CL-20 and RDX based PBXs in terms of their greater thermal stability, and Formex is a poor binder for BCHMX.