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Some Remarks on the Safety of Methane Penthrite Detonating Cords against the Inflammability of a Methane-Air Mixture

Zawadzka-Małota Iwona, Sałaciński Tomasz

Central European Journal of Energetic Materials

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2022

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Vol. 19, no. 2

181--203

EN

After analysing literature data some topics related to the properties and testing methods of detonating cords (DCs) are presented. The main attention is paid to the 2,2-bis[(nitrooxy)methyl]propane-1,3-diyl dinitrate (penthrite, PETN)-based DCs. In a case study of methane PETN DC, it is shown that the problem of DCs being able to fulfil safety precautions as permitted explosives is very complex, i.e. to determine their ability to ignite a methane-air atmosphere in coal mines. The tests have shown that the relationships between safety and the performance properties of methane PETN DC are not obvious. For example, an increase in the outer thickness coating of this methane PETN DC, causes the inflammability of a methane-air mixture to be decreased. Moreover, an increase in the amount of crystalline PETN in the cord’s core caused an increase in its velocity of detonation, but had no impact on its ability to ignite a methane-air mixture in the experimental gallery.

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The Effect of Detonator Shell Materials on Detonation Calorimetry Results

Němec Ondřej, Musil Tomáš, Künzel Martin

Central European Journal of Energetic Materials

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2020

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Vol. 17, no. 4

552--565

EN

Detonation calorimetry is a method for the determination of the heat released by the detonation of an explosive charge. Compared to classical combustion calorimetry, detonation calorimetry requires an inert atmosphere, a large sample mass and a detonator for its initiation. This detonator releases some energy for which the results must be corrected. Four types of detonator have been tested in the calorimeter alone and also in combination with explosive charges of PETN. It was found that the aluminium shell of the detonator considerably increases the apparent heat of detonation of the PETN samples in a vacuum, while the presence of combustible (polymeric) components has the opposite effect. Pressurization of the calorimetric vessel with nitrogen gas only partially suppresses these effects. The preferred technique is to use copper or glass confinement in a high pressure inert atmosphere.

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Dislocation - Assisted Initiation of Energetic Materials

Armstrong R. W.

Central European Journal of Energetic Materials

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2005

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Vol. 2, nr 3

21-37

EN

The role of dislocations in assisting initiation of (explosive) chemical decomposition of energetic materials has connection with the known influences for crystals and polycrystals of dislocations facilitating permanent deformations and phase transformations. X-ray topographic observation of relatively few dislocations in solution-grown crystals relates to the influence of large Burgers (displacement) vectors that are characteristic of molecular crystal bonding. Both model evaluations of the load dependence of cracking at hardness indentations and the derived hardness stress-strain behaviors show that dislocation movement is difficult whether in the indentation strain fields or at the tips of indentation-induced cracks. Thus, energetic crystals are elastically compliant, plastically hard, and relatively brittle [1]. Nevertheless, cracking is shown to be facilitated by the shear stress driven, normally limited, dislocation flow that, on molecular dynamics and dislocation pile-up model bases, is shown to be especially prone to producing localized hot spot heating for explosive initiations. Such model consideration is in agreement with greater dropweight heights being required to initiate smaller crystals. The crystal size effect carries over to more difficult combustion occurring for compaction of smaller crystals. The total results relate to dual advantages of greater strength and reduced mechanical sensitivity accruing for the development of nanocrystal formulations. In consequence, also, several levels of dislocation-assisted modeling are described for initiation mechanisms under shock wave loading conditions.