Explosives melt-castable

Explosives such as RDX (hexogen) and HMX (octogen) are important military explosives and generally a binder is used along with these explosives for two reasons  

1) It improves safety in processing, handling, transportation and storage. 

2) It also imparts mechanical integrity to the explosive charge. 

However, the use of such binders (usually inert polymers) brings down the overall energy of the systems this can be improved by the use of an energetic binder such as TNT, which is a low melting explosive and also has the capability of binding explosive particles. 

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Plastic explosives contain one or more of the explosives listed above, moulded in an inert, flexible binder. Because powders do not readily hold a shape and TNT is the only common melt-castable explosive, most of the explosive powders (RDX, HMX, PETN, 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)) are plasticized to make a mouldable material, for example, C-4, Semtex H, PE4, sheet explosive. A variety of plasticizers are added, but the maximum level is usually 10-15% because most plasticizers are inert and would degrade explosive output. Plastic explosives were originally developed for convenient use in military demolitions but have since been widely used in terrorist bombs. For detection techniques that rely on vapour signatures, such as canine olfaction, it is worth considering that the plasticizer is much more volatile than the explosive component. 

The reaction of aziridines and azetidine heterocycles with dinitrogen pentoxide in chlorinated solvents yields 1,2-nitramine nitrates and 1,3-nitramine nitrates respectively. In most cases yields are good to excellent, but, reactions are not as general as with the oxygen heterocycles the outcome of reactions is heavily dependent on the nature of the substituent on the exocyclic nitrogen. Some of the products from these reactions find use as melt-castable explosives i.e. Tris-X (46) and energetic plasticizers e.g. Bu-NENA (48) the latter is a component of some LOVA (low vulnerability ammunition) propellant formulations. 

PBXs have replaced melt-castable explosives in almost all nuclear weapons. The PBX formulations that have been used include PBX-9010, PBX-9011, PBX-9404, PBX-9501, LX-04, LX-07, LX-09, LX-10, LX-11 and insensitive PBXs used for this purpose are PBX-9502 and LX-17. 

A comparison of their properties with PATO reveals that the thermal stability of these derivatives is not as good as that of the parent compound, that is, PATO. Some experimental and predicted properties of the nitro derivative of PATO-I [Structure (2.25)] reported by the Chinese are density 1.92 gem"3, m.p. ca 103 °C, calc. VOD 8590ms"1 and Pc] 34.5 GPa. This compound has also been synthesized [70] in HEMRL, Pune, India and the properties are similar to those reported by the Chinese investigators. Indian scientists determined its impact sensitivity also which is h50% = 28 cm. Further work is needed to evaluate its suitability for practical applications as this explosive possesses high density, respectable performance (comparable to RDX) and low m.p. and may prove to be a melt-castable explosive similar to TNT and TNAZ. The nitro derivative of PATO-II is shown in Structure (2.26). Similarly, a new explosive called l,3-bis(l,2,4-triazolo-3-amino)-... 

The low m.p. indicates its suitability as a melt-castable explosive using steam processing. However, its thermal stability (by DSC and chemiluminescence) is only marginally acceptable suggesbng that this family of explosives is unlikely to be used for munitions. 

Watt, D.S., and Cliff, M.W. (2000) Evaluation of TNAZ-a high performance melt-castable explosive. Australian Aeronautical and Maritime Research Laboratory (AAMRL) Report No. DSTO-TR-IOOO, July. 

Abstract Erythritol tetranitrate (ETN) is a melt-castable explosive with impressive performance, similar to the well-known related nitrate ester, pentaerythritol tetranitrate (PETN). Though ETN has been known since 1849, its properties have not been thoroughly investigated. We report here the first y2" copper cylinder tests of ETN, compared with... 

The melting point of synthesized 1 was measured with DSC (Differential Scanning Calorimeter) and proved to be exactly correspondent with the reported data, 82 °C (Figure 4). This fact means that 1 can be utilized as an ingredient of the melt-castable explosives. 

MTNI (1) was synthesized successfully, its sensitivities were measured, and performance was calculated. Although the performance of 1 appears, at best, to be close to those of RDX, we believe that there are two possible merits to pursue the explosive formulations with 1 (1) insensitiveness and (2) low melting point. If MTNI (1) is significantly less sensitive than RDX, it can be a good ingredient for insensitive explosives. Since the melting point of 1 is quite close to TNT, it also will be a good candidate to be used in melt-castable explosives and to replace TNT We know that 1 is much more powerful than TNT. 

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