Thermally stable explosives

L. J. Bement, "AppHcation of Temperature Resistant Explosives to NASA Mission," in Symposium on Thermally Stable Explosives, NOL, White Oaks, Md.,June 1970. 

Surprisingly it is thermally stable to 300°C, (cadmium azide is very heat sensitive) but is hygroscopic and very readily hydrolysed to explosive hydrogen azide. 

Following an explosion dining drying of 2-nitrobenzyl bromide, the thermal stability of all six isomeric nitrobenzyl halides was investigated by TGA, DSC and ARC techniques. All the halides decomposed exothermally with abundant gas evolution, and the 2-nitro chloride is less thermally stable than the 3- or 4-isomers. See 2-Nitrobenzyl bromide... 

Pentaerythritol tetranitrate (PETN) is a colorless crystalline solid that is very sensitive to initiation by a primary explosive. It is a powerful secondary explosive that has a great shattering effect. It is used in commercial blasting caps, detonation cords, and boosters. PETN is not used in its pure form because it is too sensitive to friction and impact. It is usually mixed with plasticized nitrocellulose or with synthetic rubbers to form PBXs. The most common form of explosive composition containing PETN is Pentolite, a mixture of 20 to 50% PETN and TNT. PETN can be incorporated into gelatinous industrial explosives. The military has in most cases replaced PETN with RDX because RDX is more thermally stable and has a longer shelf life. PETN is insoluble in water, sparingly soluble in alcohol, ether, and benzene, and soluble in acetone and methyl acetate. 

Formal sequential addition of amino groups to 2,4,6-trinitroaniline gives 1,3-diamino-2,4,6-trinitrobenzene (DATB, 56) and 1,3,5-triamino-2,4,6-trinitrobenzene (TATB, 57). TATB is more stable than expected from the additivity calculation. The ability to have hydrogen bonding with three amino groups both intra- and inter-molecularly in the crystal stabilizes the molecule. The molecule that results is thermally stable and used as an explosive in situations where a very insensitive explosive is needed. 

Poly(carbon monofluoride) is a white compound, often reported to be explosive and unstable but found in our research results to be stable in air at temperatures up to at least 600°C. In fact, poly(carbon monofluoride) is the most thermally stable fluoropolymer known. It decomposes upon heating at 800°C or under a high vacuum at 580°C to form a series of polyolefinic fluorocarbons. 19 The compounds with compositions in the range of CFo s to CFos are nearly black. The CFos to CF0.95 compounds become gray and the CF095 to CFuj... 

Interest in polynitroarylenes has resumed over the past few decades as the demand for thermally stable explosives with a low sensitivity to impact has increased. This is mainly due to advances in military weapons technology but also for thermally demanding commercial applications i.e. oil well exploration, space programmes etc. Explosives like 1,3-diamino-2,4,6-trinitrobenzene (DATB) (13), l,3,5-triamino-2,4,6-trinitrobenzene (TATB) (14), 3,3 -diamino-2,2, 4,4, 6,6 -hexanitrobiphenyl (DIPAM) (15), 2,2, 4,4, 6,6 -hexanitrostilbene(HNS, VOD 7120 m/s, = 1.70 g/cm ) (16) and A,A -bis(l,2,4-triazol-3-yl)-4,4 -diamino-2,2, 3,3, 5,5, 6,6 -octanitroazobenzene (BTDAONAB) (17) fall into this class. TATB is the benchmark for thermal and impact insensitive explosives and finds wide use for military, space and nuclear applications. 

Similarly, 5-picrylamino-l,2,3,4-tetrazole (PAT) (116) " " and 5,5 -styphnylamino-1,2,3,4-tetrazole (SAT) (117) " have been synthesized by condensing picryl chloride and styphnyl chloride with 5-amino-l,2,3,4-tetrazole in methanol respectively. A comparison of thermal and explosive properties of newly synthesized PAT (calculated VOD 8126 m/s) and SAT (calculated VOD 8602 m/s) reveals that PAT is more thermally stable than SAT but more sensitive to impact and friction. " ... 

The reactions of hexanitrobenzene (55) and 2,3,4,5,6-pentanitroaniline (31) with ammonia have been used to synthesize the thermally stable explosive l,3,5-triamino-2,4,6-trinitrobenzene (TATB). Holmes and Fliirschiem have studied the reactions of 2,3,4,5,6-pentanitroaniline with nucleophiles. 

Warman and Siele reported a high yielding route to l,3-dichloro-2,4,6-trinitrobenzene (106) (styphnyl chloride) which involves treating styphnic acid (5) with two equivalents of pyridine followed by reacting the resulting pyridinium salt (133) with phosphorous oxychloride. l,3-Dichloro-2,4,6-trinitrobenzene is an important precursor to the thermally stable explosive DATE (Section 4.8.1.4). 

Agrawal and co-workers have reported the synthesis of A,A -bis(l,2,4-triazol-3-yl)-4,4 -diamino-2,2, 3,3, 5,5, 6,6 -octanitroazobenzene (17) (BTDAONAB) via nitration-oxidative coupling of 4-chloro-3,5-dinitroaniline (152) followed by nucleophilic displacement of the chloro groups with 3-amino-1,2,4-triazole. BTDAONAB has the unique distinction of being the most thermally stable explosive reported so far (DTA exotherm 550 °C) as compared to well known thermally stable explosives such as TATB ( 360 °C), TACOT ( 410 °C), NONA ( 440 50 °C), and PYX ( 460 °C). 

Polynitropolyphenylene (PNP) (159), which is a polymeric explosive, exhibits high thermal stability and possesses a low sensitivity to friction and impact. This polymeric mixture, synthesized from the reaction of styphnyl chloride (106) with copper powder in nitrobenzene, has found use as a thermally stable binder in pyrotechnic compositions. ... 

Amino-1,2,4-triazole is a useful starting material for the synthesis of many 1,2,4-triazole-based explosives. Jackson and Coburn synthesized a number of picryl- and picrylamino-substituted 1,2,4-triazoles. PATO (99) is synthesized from the reaction of 3-amino-1,2,4-triazole (98) with picryl chloride (67). ° PATO has also been synthesized from the reaction of 3-amino-l,2,4-triazole with A,2,4,6-tetranitromethylaniline (tetryl). PATO has a low sensitivity to impact and is thermally stable up to 310 °C. PATO (VOD 7469 m/s) exhibits lower performance to TATB (VOD 8000 m/s) which is the common benchmark standard for thermal stability and insensitivity in explosives. 

ANTA (114) readily forms a stable anion on reaction with bases like sodium ethoxide and this anion has been used as a nucleophile for the synthesis of many ANTA derivatives. Laval and co-workers synthesizedDANTNP (116) (calculated VOD 8120 m/s, = 1.84 g/cm, m.p. > 330 °C) from the reaction of 4,6-dichloro-5-nitropyrimidine (115) with two equivalents of ANTA (114) in the presence of sodium ethoxide. Agrawal and co-workers studied the thermal and explosive properties of both ANTA and DANTNP and suggested their use for applications in propellant/explosive formulations where insensitivity coupled with thermal stability is of prime importance. The activation energies of ANTA and DANTNP indicate that DANTNP is more thermally stable than ANTA. 

Pagoria and co-workers synthesized a number of thermally stable explosives from the reaction of the sodium salt of ANTA with chloro-substituted arylenes and A-heterocycles. These include the synthesis of (117) from picryl ehloride, PRAN (118) from 2-chloro-3,5-dinitropyridine, IHNX (119) from 2,4-dichloro-5-nitropyrimidine, (120) from 1,5-dichloro-2,4-dinitrobenzene, and (121) from 4-chloro-6-(3-nitro-l,2,4-triazolyl)-5-nitropyrimidine. Coburn and co-workers " reported the synthesis of the tetrazine (122) and the triazine (123) from the reaction of the sodium salt of ANTA with 3,6-dichlorotetrazine and cyanuric chloride respectively. 

Chemists at Los Alamos National Laboratory synthesized a series of picrylamino-substimted pyrimidines as part of a research effort to And new thermally stable explosives. The pyrimidine-based explosive (187) is synthesized via the reaction of 2,4,6-triaminopyrimidine with picryl fluoride followed by subsequent nitration with nitric acid." ... 

The dibenzotetraazapentalene ring system was first discovered by chemists at DuPont and is a planar system with six electrons delocalized over four nitrogen atoms. There are two isomeric arrangements of these four nitrogens which lead to the l,3a,4,6a- (220) and l,3a,6,6a-(91) ring systems. Nitro derivatives of both isomeric dibenzotetraazapentalenes have been explored as thermally stable explosives. 

The use of dinitrogen pentoxide in the Ponzio reaction for the oxidation-iutration of oximes to em-dinitro groups has been reported by Russian chemists. Millar and co-workers extensively investigated these reactions and reported the synthesis of 2,4,5,7,9,9-hexanitrofluorene (2), a thermally stable explosive with an oxygen balance better than TNT. Other energetic materials containing gem-dinitro functionality were synthesized from the oximes of acetophenone, 4-nitroacetophenone, a-nitroacetophenone and 2-hydroxyacetophenone. 

The nitration of l,3,5-trichloro-2-nitrobenzene (8) to l,3,5-trichloro-2,4-dinitrobenzene (9) with dinitrogen pentoxide in absolute nitric acid goes to completion in only 2-4 minutes at 32-35 °C. Further nitration of (9) would yield l,3,5-trichloro-2,4,6-trinitrobenzene (10) which undergoes ammonolysis on treatment with ammonia in toluene to give the thermally stable explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) (11). The same sequence of reactions with l,3-dichloro-2-nitrobenzene provides a route to l,3-diamino-2,4,6-trinitrobenzene (DATE). Such reactions are clean and occur in essentially quantitative yield. 

TATP displayed less reactivity with metals than HMTD, but it was less thermally stable. Sublimation (the direct transition of a material from the solid to the gaseous state) was the main pathway for weight loss in TATP. Even at room temperature, notable weight loss could be witnessed within a day. The high sensitivity and thermal instability of TATP precluded its use in any practical applications. Although of limited academic interest, it never took hold in the explosives community. 

F-A. Baum et al, "Tetmostoykiye VV i Ikh Deystviye v Glubokikh Skvazhinakh (Thermally Stable Explosives and Their Action in Deep Boreholes , Nedra, Moscow (1969)... 

Triamino-2,4,6-trinitrobenzene (TATB) Thermally stable and very insensitive main high explosive. Special fine-grained TATB is used in boosters... 

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