Lead azide explosive power

In general terms, PETN can be characterized as a sensitive , brisant, and powerful high expl. Explosive sensitivity is a rather nebulous quantity, but there can be no doubt that PETN is a much more sensitive material than TNT, but rather less sensitive than Lead Azide. In particular, PETN requires very little priming i charge (less than 1 mg LA) to initiate its detonation. This is the characteristic that makes PETN so widely used in blasting cap base charges, in detonating cord and in boosters... 

Mechanical treatment alone may be sufficient to induce significant decomposition such processes are termed mechanochemical or tribo-chemical reactions and the topic has been reviewed [385,386]. In some brittle crystalline solids, for example sodium and lead azides [387], fracture can result in some chemical change of the substance. An extreme case of such behaviour is detonation by impact [232,388]. Fox [389] has provided evidence of a fracture initiation mechanism in the explosions of lead and thallium azide crystals, rather than the participation of a liquid or gas phase intermediate. The processes occurring in solids during the action of powerful shock waves have been reviewed by Dremin and Breusov [390]. 

It is less sensitive and a less powerful explosive than silver azide or lead azide. It explodes on heating in air to above 270°C, or after an induction period at 140°C in the dark under vacuum. 

Primary explosives differ from secondary explosives in that they undergo a rapid transition from burning to detonation and have the ability to transmit the detonation to less sensitive (but more powerful) secondary explosives. Primary explosives have high degrees of sensitivity to initiation through shock, friction, electric spark, or high temperature, and explode whether confined or unconfined. Some widely used primary explosives include lead azide, silver azide, tetrazene, lead styphnate, mercury fulminate, and diazodinitrophenol. Nuclear weapon applications normally limit the use of primary explosives to lead azide and lead styphnate. 

Primary explosives are sensitive to modest stimuli such as heat, spark, or friction application of the correct stimulus will lead to a detonation. The primary explosives used in detonators are typically extremely sensitive but not particularly powerful common examples are mercury fulminate, lead azide, and lead styphnate. In principle, the heavy metals present in most primary explosives should be a good cue for detection however, there are primary explosives that do not contain such elements. 

Nevertheless, examination of the response of explosives to more or less controlled impacts did provide qualitative information about the safety of handling these explosives. There is no question that Lead Azide is much more impact sensitive than TNT, and that TNT is much safer to handle than Lead Azide. It is the quantitative meaning of the much more" that creates confusion and indeed it may have no quantitative meaning at all. Presumably some of the immense effort devoted in past years to impact testing is excusable because it was based on the fond hope (unfortunately unrealized) of finding the ideal explosive—one that is powerful but insensitive ... 

The erstwhile Explosives Research and Development Laboratory (ERDL), now High Energy Materials Research Laboratory (HEMRL), Pune, had undertaken a study on primary explosives with a view to synthesizing a series of new explosives, which are safer, powerful and free from the drawbacks of lead azide and MF. As a result of these sustained efforts, HEMRL has successfully synthesized and developed a new and safer initiatory explosive called basic lead azide (BLA). 

Aluminium detonators with lead azide and other explosives were used in the mining industry for some time, e.g. a No. 8 detonator, contained 1 g of tetryl and 0.3 g of a mixture of lead azide and lead styphnate. These were more powerful than those with a fulminate-tetryl charge, but the use of detonators with aluminium sheathing was soon forbidden in coal-mines due to the danger created by the burning of the aluminium. 

Resorcinol nitrates readily to the trinitro compound, yellow prisms from water or alcohol, m.p. 175.5°. Styphnic acid is more expensive and less powerful than picric acid. Liouville67 found that styphnic acid exploded in a manometric bomb, at a density of loading of 0.2, gave a pressure of 2260 kilos per sq. cm., whereas picric acid under the same conditions gave a pressure of 2350 kilos per sq. cm. It did not agglomerate to satisfactory pellets under a pressure of 3600 kilos per sq. cm. It is a fairly strong dibasic acid, and its salts are notably more violent explosives than the picrates. Lead styphnate has been used to facilitate the ignition of lead azide in detonators. 

Clark reports experiments with diazodinitrophenol, mercury fulminate, and lead azide in which various weights of the explosives were introduced into No. 8 detonator capsules, pressed under reenforcing caps at 3400 pounds per square inch, and fired in the No. 2 sand test bomb. His results, tabulated below, show that diazodinitrophenol is much more powerful than mercury fulminate and lead azide. Other experiments by Clark showed... 

Properties of Ag-salts of 1-(iV-nitramino)-, 2-(Wnitramino)-, 5-(W-nitramino)tetrazole, and l-methyl-5-(fV-nitramino)-tetrazole have been examined. The initiation power of these salts was estimated from minimal blasting charge in RDX. Silver salts of l-(W-nitramino)- and 2-(iV-nitramino)tetrazole have a DDT (deflagration-to-detonation transition) period shorter than the salts of 5-(W-nitramino)tetrazole and l-methyl-5-(W-nitramino)tetrazole. The salt of 2-(fV-nitramino)te-trazole is a more powerful initiative explosive than lead azide <2006MI39>. 

If small amounts of copper and hydrochloric acid are added to the reaction mixture, a white product is obtained. Mercury fulminate is stored under water. It is dried at 40 °C (104 °F) shortly before use. Owing to its excellent priming power, its high brisance, and to the fact that it can easily be detonated, mercury fulminate was the initial explosive most frequently used prior to the appearance of lead azide. It is used in compressed form in the manufacture of blasting caps and percussion caps. The material, the shells, and the caps are made of copper. 

Typical primary explosives are lead azide and lead styphnate (see Fig. 1.17). The latter one is less powerful than LA but easier to initiate. Tetrazene (Fig. 2.2) is often added to the latter in order to enhance the response (sensitizer). (N.B. mercury fulminate used to be used as a sensitizer). Tetrazene is an effective primer which decomposes without leaving any residue behind. It has been introduced as an additive to erosion-free primers based on lead trinitroresorcinate. Unfortunately, tetrazene is hydrolytically not entirely stable and in long term studies decomposes at temperatures above 90 °C. Diazodinitrophenol (Fig. 2.2) is also a primary explosive and is primarily used in the USA. However, the compound quickly darkens in sun-... 

CDNTA form a white to bluish white powder, crystals, or granules. The crystals are sensitive to shock, friction, and percussion. CDNTA is a powerful primary explosive that demonstrates outstanding potential as a future replacement for mercury fulminate, lead styphnate, lead azide, and diazodinitrophenol for use in blasting caps and detonators. It should not be stored dry, and should be desensitized with dextrose, sulfur, starch, wood pulp, dextrin, or gum Arabic after preparation... 

In the USA, this diazo compound is used as an initiating explosive. It is more powerful than mercury fulminate and slightly less so than lead azide. 

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