Explosives primary

Explosives are further divided into primary and secondary explosives. Primary explosives are detonated by heat, spark, flame, or mechanical impact, whereas secondary explosives can only be detonated by an externally applied shock wave such as commonly produced by a primary explosive. 

Secondary explosives when ignited by a flame will normally bum without detonating. However, even low explosives can be made to detonate under suitable conditions depending on the material. 

Some selected primary explosives and their properties are given in Table 14.2. Most of these initiators are toxic as well as tmstable. They are usually combined with other initiators or other substances such as KCIO3, KNO3, Ba(N03)2, Pb02, and SbjSj. 

Roussak and H.D. Gesser, Applied Chemistry A Textbook for Engineers and Technologists, DOI 10.1007/978-l-4614-4262-2 14, Springer Scitaice+Busmess Media New York 2013 

Factors controlling reaction rate Heat transfer Heat transfer Shock transfer  

Primary explosives are substances which unlike secondary explosives show a very rapid transition from combustion (or deflagration) to detonation and are considerably more sensitive towards heat, impact or friction than secondary explosives. Primary explosives generate either a large amount of heat or a shockwave which makes the transfer of the detonation to a less sensitive secondary explosive possible. They are therefore used as initiators for secondary booster charges (e.g. in detonators), main charges or propellants. Although primary explosives (e.g. Pb(Ns)2) are considerably more sensitive than secondary explosives (e.g. RDX), their detonation velocities, detonation pressures and heat of explosions are as a rule, generally lower than those of secondary explosives (Tab. 2.1). 

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 explo- 

HNS is a temperature stable secondary explosive, which is particularly useful for blasting in very hot oil deposits, because it is stable to approx. 320 °C. Problems in this area however relate to the initiator, since HNS is relatively difficult to initiate. The most useful initiator is cadmium azide, Cd(N3)2, ( dec. ca. 295 °C). However, since cadmium is toxic, alternatives are currently being sought after. The two most promising compounds to date to replace Cd(N3)2 are silver nitriminotetrazolate (T ec. = 366 °C) and di (silveraminotetrazole) perchlorate (Idee. = 319 °C) (Fig. 2.3) [10]. 

Primary explosives (also known as primary high explosives) differ from secondary explosives in that they undergo a very rapid transition from burning to detonation and have the ability to transmit the detonation to less sensitive explosives. Primary explosives will detonate when they are subjected to heat or shock. On detonation the molecules in the explosive dissociate and produce a tremendous amount of heat and/or shock. This will in turn initiate a second, more stable explosive. For these reasons, they are used in initiating devices. The reaction scheme for the decomposition of the primary explosive lead azide is given in Reaction 2.2. 

This reaction is endothermic, taking in 213 kJ of energy. According to Reaction 2.2, one atom of nitrogen is expelled from the Nj ion. This nitrogen then reacts with another Nj ion to form two molecules of nitrogen as shown in Reaction 2.3. 

Reaction 2.3 is highly exothermic, producing 657 kJ of energy. The decomposition of one Nj group may involve 2-3 neighbouring Nj  

Lead azide, Lead styphnate, Mercury fulminate, Tetrazene, etc 

Gelatines, Powders, Permitted explosives, ANFO, Emulsion slurries, etc 

M-C Metal bonded with carbon in some organometallic compounds 

Singie-base, Double-base, Triple-base, Blackpowder, etc 

The main focus of this monograph is on the individual primary explosives that have been used or reported as promising candidates for potential use. The only exception we included is nitrogen triiodide, which we believe will never find any use. The priming compositions are covered only briefly in this chapter to give more space to discussing the use of primary explosives in a broader perspective. 

Primary explosives are sensitive mixtures/compounds that can be easily detonated by an SII— nonexplosive means such as flame, heat, impact, friction, electric spark, etc. They are mainly used in apphcations where it is desired to produce shock for initiation of a less sensitive explosive (secondary explosive). The ability to initiate detonation of secondary explosives is the characteristic that makes primary explosives useful in detonators and blasting cups or caps (detonators used for mining). In order for this to work, primary explosives must detonate shortly after the nonexplosive initiation. The fast transition from SII to detmiation (sometimes referred to as acceleration) is the most important distinction between primary and secondary explosives. 

Another important use of primary explosives lies in their application as sensitizers in priming compositions. The purpose of such mixtures is to provide reliable ignition and the role of the primary explosives in such mixtures is to make them sensitive enough to be easily ignited. The detonation of such a mixture is undesirable and must be prevented by careful selection of the ingredients and then-quantities for a particular application. 

Apart from the already mentioned lead azide and mercury fulmiate, the classic examples of primary explosives include lead styphnate (LS), silver azide (SA), dinol (DDNP), and tetrazene (GNGT). Primary explosives (individual components) are often mixed and used in the form of compositions rather than as single component energetic materials. Mixtures may consist of either individual primary explosives (astryl-MF/SA [2]) or primary explosives plus some nonexplosive additive (LA/LS/ dextrine or ASA composition— LA/LS/Al). 

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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. 

Pentaerythritol may be nitrated by a batch process at 15.25°C using concentrated nitric acid in a stainless steel vessel equipped with an agitator and cooling coils to keep the reaction temperature at 15—25°C. The PETN is precipitated in a jacketed diluter by adding sufficient water to the solution to reduce the acid concentration to about 30%. The crystals are vacuum filtered and washed with water followed by washes with water containing a small amount of sodium carbonate and then cold water. The water-wet PETN is dissolved in acetone containing a small amount of sodium carbonate at 50°C and reprecipitated with water the yield is about 95%. Impurities include pentaerythritol trinitrate, dipentaerythritol hexanitrate, and tripentaerythritol acetonitrate. Pentaerythritol tetranitrate is shipped wet in water—alcohol in packing similar to that used for primary explosives. 

Tetiyl. 2,4,6-Trinitrophenylmethylm tramine (tetryl) was used ia pressed form, mostly as a booster explosive and as a base charge ia detonators and blasting caps because of its sensitivity to initiation by primary explosives and its relatively high energy content. Properties are presented ia Table 11 (173). Batch and continuous processes for the production of tetryl have been developed. Tetryl is no longer used ia the United States and has been replaced by RDX (174-178). 

Numerous explosives are based on hydrazine and its derivatives, including the simple azide, nitrate, perchlorate, and diperchlorate salts. These are sometimes dissolved in anhydrous hydrazine for propeUant appUcations or in mixtures with other explosives (207). Hydrazine transition-metal complexes of nitrates, azides, and perchlorates are primary explosives (208). 

While this book does not cover shock-sensitive powders, such as primary explosives, UN-DOT Class 4.1 Flammable Solids are within its scope. These include thermally unstable powders that can both deflagrate in an oxidant and decompose in bulk. Examples include some nitrogen blowing agents. Should ignition occur at any point, a propagating decomposition... 

Dust explosions are relatively rare but ean involve an enormous energy release. A primary explosion, involving a limited quantity of material, ean distribute aeeumulations of dust in the atmosphere whieh, on ignition, produees a severe secondary explosion. 

High explosives whieh detonate to produee shoek waves. Materials whieh are easily detonated by meehanieal or eleetrieal stimuli are tenued primary explosives . Those requiring an impinging shoek wave to initiate them are seeondary explosives . 

Article containing a primary explosive substance and not containing two or more independent safety features B... 

Secondary detonating explosive substance or black powder or article containing a secondary detonating explosive substance, in each case without means of initiation and without a propelling charge, or article containing a primary explosive substance and containing two or more independent safety features D... 

Detonating explosives are primary or secondary. Primary explosives detonate by flame,... 

Potassium Methylnitraminate. K.CH302N2 fine needles, which expl violently on heating. 1 According to Davis (Ref 2), the heavy metal salts of methylnitramine are primary explosives, but have not been investigated extensively Refs 1) Beil 4, 567, (568) [968]... 

Liquid Sedimentation Techniques for Measuring the Particle-Size Distribution of Primary Explosives , PATR 4387 (1972) 42) Anon, Stan-... 

Primary Explosives. See under Initiating Explosives in Vol 7,1105-L to I106-L... 

Eds, Proceedings of the International Conference on Research in Primary Explosives, Vols 1—3, Explosives Research and Development Establishment (ERDE), Waltham Abbey, Essex, England (17-19 March 1975), AD B013 627, AD B013 628 AD BOB 629 156) Anon,... 

Mass effects due to some ions in salts. It is generally observed that there is a greater instability amongst compounds containing heavy atoms compared with elements in the first periods of the periodic tabie.This can be observed by analysing enthalpies of formation of ammonia, phosphine, arsine and stibine (see previous table for the last three). In the same way, it is easier to handle sodium azide than lead azide, which is a primary explosive for detonators. It is exactly the same with the relatively highly stable zinc and cadmium thiocyanates and the much less stable mercury thiocyanate. 

This is the case with nitrites and alkaline nitrates. Sodium nitrite/potassium cyanide mixture has been suggested as a primary explosive for detonators. 

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