Primary explosives manufacture

Figure 3. Full-scale production (60-liter) kettle of British design as installed at Picatiimy Arsenal. Used at Royal Ordnance Factories for primary explosives manufacture in 2%-5-kg batches.

Only relatively few compounds can act as primary explosives and still meet the restrictive military and industrial requirements for reflabiUty, ease of manufacture, low cost, compatibiUty, and long-term storage stabiUty under adverse environmental conditions. Most initiator explosives are dense, metaHoorganic compounds. In the United States, the most commonly used explosives for detonators include lead azide, PETN, and HMX. 2,4,6-Triamino-l,3,5-triuitrobenzene (TATB) is also used in electric detonators specially designed for use where stabiUty at elevated temperatures is essential. 

Lead Azide. The azides belong to a class of very few useflil explosive compounds that do not contain oxygen. Lead azide is the primary explosive used in military detonators in the United States, and has been intensively studied (see also Lead compounds). However, lead azide is being phased out as an ignition compound in commercial detonators by substances such as diazodinitrophenol (DDNP) or PETN-based mixtures because of health concerns over the lead content in the fumes and the explosion risks and environmental impact of the manufacturing process. 

Despite the fact that LA, LS and tetrazene suffer from serious drawbacks, they are still being used in detonators and cap compositions for military and civil applications. Thus LA, LS and tetrazene are the most commonly used primary explosives at present and research is in progress in order to find out suitable substitutes free from such drawbacks. The aim of research in initiatory explosives has all along been to get less sensitive, more compatible, more stable and more efficient material so that safety in manufacture and handing is ensured. 

McGuchan, R. (1979) Improvements in primary explosive compositions and their manufacture. Proc. 10th Symp. on Explosives and Pyrotechnics, San Francisco, California, Feb. 14-16, pp. 

Fig. 49. Diagram of the design and operation of a reactor for the manufacture of lead azide and other primary explosives (tetrazene, lead styphnate and lead picrate).

Curtius added lead acetate to a solution of sodium or ammonium azide resulting in the formation of lead azide. In 1893, the Prussian Government carried out an investigation into using lead azide as an explosive in detonators, when a fatal accident occurred and stopped all experimental work in this area. No further work was carried out on lead azide until 1907 when Wohler suggested that lead azide could replace mercury fulminate as a detonator. The manufacture of lead azide for military and commercial primary explosives did not commence until 1920 because of the hazardous nature of the pure crystalline material. 

Manufacture of primary explosives is very hazardous and accidents such as explosions can occur during the preparation. Therefore strict safety procedures are always adhered to. 

Figure 96. Manufacture of Detonators. (Courtesy Hercules Powder Company.) The safe mixing of the primary explosive charge for blasting caps is accomplished mechanically behind a concrete barricade by lifting slowly and then lowering first one corner of the triangular rubber tray, then the next corner, then (lie next, and so on. In the background, the rubber bowl or box in which the mixed explosive is carried to the building where it is loaded into caps.

Secondary explosives, or high explosives, are generally less sensitive to heat and shock than primary explosives and are therefore safer to manufacture, transport, and handle. Most secondary explosives will simply burn rather than explode when ignited in air, and most can be detonated only by the nearby explosion of a primary initiator. Among the most common secondary explosives are nitroglycerin, trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), and RDX. 

Home manufacture of primary detonators has always been a mystery, whereas explosive manufacture is relatively straightforward. Now, readers have the information to do the whole process from start to finish. They can, if they must, home-manufacture explosives and detonators that are effective and somewhat predictable. 

Organic peroxides may be explosive. They are usually not manufactured for blasting purposes, but rather as catalysts for polymerization reactions. They are utilized in a safely phlegmatized condition. They will not be discussed in this book, except for two substances displaying properties of primary explosives -< Tricycloacetone Peroxide and -> Hexamethylenetriperoxide Diamine. 

Devices using lead primary explosives - from primers for bullets to detonators for mining - are manufactured in the tens of millions every year in the United States. In the US alone, over 750 lbs. of lead azide are consumed every year for military use. 

Styphnic acid is a yellow crystalline solid with a melting point of 176 Celsius. It is insoluble in water, but soluble in alcohol, ether, and acetic acid. Styphnic acid turns deep yellow on contact with air, so it should be stored in tightly sealed bottles in a cool place. The compound is corrosive and readily forms salts with metal hydroxides and carbonates—many of which are primary explosives, i.e., lead styphnate. Styphnic acid bums rapidly and violently when ignited. For safety reasons, styphnic acid should be stored wet with 10% water. It is used primarily in the manufacture of lead styphnate, but is used with outstanding results in explosives compositions when mixed with nitrocellulose, sodium nitrate, or ammonium perchlorate and... 

Tetrazene is a relatively weak primary explosive. It should always be used with a sensitive booster charge such as PtTN. When used in the manufacture of detonators, tetrazene should be freely poured into a capsule. Tetrazene loses much of its effectiveness when pressed. 

Explosive, primary Explosive substance manufactured with a view to producing a practical effect by explosion which is very sensitive to heat, impact or friction and which, even in very small quantities, either detonates or bums very rapidly. It is able to transmit detonation (in the case of initiating explosive) or deflagration to secondary explosives close to it. The main primary explosives are mercury fulminate, lead azide and lead styphnate. UN App. B, ICAO A2, lATA App. A... 

There is a vast array of energetic materiald that falls mder the sensitivity classification of primary explosives. When the complexity and extent of primer explosives are multiplied by all the different ways manufacturers use initiation devices, the subject becomes extremely voluminous. Rather than cover all these materials and their applications, we noil concentrate on only those most commonly used in the construction of such initiation systems as blasting caps and primers. Figure 13 contains some of the physical attributes of common primary explosives. 

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