CHEMICAL EXPLOSIVES: WARHEAD ALLY

Onyenekenwa Cyprian Eneh Institute for Development Studies, Enugu Campus, University of Nigeria, Nsukka; Tel.: +234-803-338-7472, E-mail: [email protected], [email protected]

Abstract Interactions among humans and international communities result in occasional misunderstanding, which may mature into dispute, quarrel, conflict or war. To secure victory, the warhead may inflict damage on the target enemy, mostly by a transfer of mechanical energy, producing shock wave or lethal fragments. This review examines how the warhead may store this energy in form of chemical explosives, which take advantage of exothermic chemical reactions that release energy. It recommends the discouragement of the production and use of chemical explosives in favour of Green Chemistry. Keywords: explosive materials; exothermic reactions; detonation

Introduction In a world, where no man or nation is an If the reaction proceeds slowly, the island, human and international relations are released energy will be dissipated and there indispensable. This is truer for nations in the will be few noticeable effects other than an globalising village, as the entire world has increase in temperature. But, if the reaction become today. Since people have differences proceeds very rapidly, the energy will not be in interests, mental levels and generations, dissipated. Thus, a great quantity of energy misunderstanding frequently occurs. A can be deposited into a relatively small mismanaged misunderstanding matures into a volume. This manifests in a rapid expansion dispute. If not carefully handled, a dispute of hot gases, leading to the explosion of the blossoms into a quarrel. Without a wise relatively small container. This, in turn, management, a quarrel is blown into a creates a shock wave or propels fragments of conflict. And, if not carefully managed, a the shattered container outwards at high conflict breaks into a full-blown war. speed. The fragments may kill or blow down Therefore, misunderstanding needs wise objects, such as houses or bridges (Meyer et management to forestall dispute, quarrel, al, 2007). conflict and full-blown war (Commander, Chemical explosive is a destructive 1972). device against human life and environment Once a war breaks out, victory is (Eneh, 2011 a,b,c,d; Eneh and Agbazue, sought desparately with all strength and tact 2011; Eneh and Agunwamba, 2011). The at the fighter’s disposal. To secure victory, literature on chemical explosives is the main purpose of any warhead is to inflict fragmented and disharmonious. This review damage on the target enemy, mostly by a paper sought to update and harmonise transfer of energy from the former to the resources on the subject. After this brief latter. Typically, the energy is mechanical in introduction, the remainder of the paper is nature and takes the form of a shock wave or structured as follows: the difference between the kinetic energy of fragments, both of chemical explosives and other exothermic which must release a large amount of energy. reactions, chemical explosive materials, Many warheads store this energy in form of classification of explosive materials, barrier chemical explosives, which take advantage of and initiation of explosive reactions, exothermic chemical ractions that release chemical explosives and their uses, and energy (Army Research Office, 1964). implications for development.

31 Eneh, O.C.: Chemical explosives: Warhead ally, Technoscience Review, 3(1&2), Nov., 2012

The difference between chemical produced, then the energy will remain in the explosives and other exothermic reactions products as heat. Most chemical explosions Chemical explosions may be distinguished involve a limited set of simple exothermic from other exothermic reactions by the oxidation reactions (reactions with oxygen extreme rapidity of their reactions. In that release energy) (Urbanski, 2009). addition to the violent release of energy, The total amount of energy released chemical explosions must provide a means to in the reaction is called the heat of explosion. transfer the energy into mechanical work. It can be calculated as the difference between This is accomplished by expanding product the heat of formation of reactants and the heat gases from the reaction. If no gases are of formation of the products:

E = Ef(reactants) - Ef (products)

Table 3.1 shows the heats of formation for (reactants). The heat of explosion is positive the products and many common explosives for the exothermic reaction.

Table 3.1: Heats of formation Name Formula MW (g/mol) Ef (kJ/mol)

Carbon monoxide CO 28 -111.80 Carbon dioxide CO2 44 -393.50 Vapour H2O 18 -240.60 Nitroglycerin C3H5N3O9 227 -333.66 RDX C3H6N6O6 222 +83.82 HMX C4H8N8O8 296 +104.77 PETN C5H8N4O12 316 -514.63 Trinitrotoluene, TNT C7H5N3O6 227 -54.39 TETRYL C7H5N5O8 287 +38.91 Source: fas.org, 2011 Notes: 1) CO,CO2 and H2O are assumed to be in gaseous form. 2) Ef for N2, H2, O2 and all other elements are all zero.

Since most of the energy release comes from trinitrotoluene (TNT), 10 moles of gas are oxidation reactions, the amount of oxygen produced for each mole of explosive. This available is a critical factor. If there is fact is exploited in Berthelot approximation insufficient oxygen to react with available to predict the relative explosive strength of a carbon and hydrogen, the explosive is material (as compared to TNT on a mass considered as oxygen deficient. The basis) (Yinon and Zitrin, 1996). converse is considered as oxygen rich. A The relative explosive strength quantitative measure of this is called the calculated in this manner is of limited use. oxygen balance (OB) (Akhavan, 2011). What is really important is the actual The strength of the explosive is strength, which can only be measured by determined by the conversion of the heat of experiment. Standard tests mostly involve a explosion into mechanical work, which is direct measurement of the work performed. dependent upon the amount of produced Examples of measurements for RDX are: gases available for expansion. In the case of

32 Eneh, O.C.: Chemical explosives: Warhead ally, Technoscience Review, 3(1&2), Nov., 2012

Ballistic mortar test 140 % Trauzl block test 186 % Sand crush test 136 %

They all compare favorably with our Berthelot approximation (Fordham, 1980).

Chemical explosive materials tetrazene explosive. Again, there are tetryl, Chemical explosives may be pure chemicals tetrytol, 1,3,5-triazido-2,4,6-trinitrobenzene, or mixtures. Cooper and Kurowski (1996) triethylene glycol dinitrate, trimethylolethane identified and listed alphabetically about 82 trinitrate, 2,4,6-trinitroaniline, trinitroanisole, of them as azides, fulminates, 1'-azobis-1,2,3- and 1,3,5-trinitrobenzene. Yet others are triazole, 4-dimethylaminophenylpentazole, 2,4,6-trinitrobenzenesulfonic acid, acetone peroxide, ammonium azide, and trinitrotoluene, trinitrotriazine, 2,4,6- ammonium chlorate. Others are ammonium tris(trinitromethyl)-1,3,5-triazine, urea dinitramide, ammonium nitrate, ammonium nitrate, and xylitol pentanitrate (Cooper and permanganate, barium azide, 1,2,4- Kurowski, 1996). butanetriol trinitrate, chlorine azide, and Explosive materials must be highly copper(I) acetylide. Again, there are energetic, as characterized by the relative copper(II) azide, diacetyl peroxide, strength, and must also react violently. The diazodinitrophenol, diethylene glycol speed of the reaction is vital to the build up dinitrate, 4,4'-dinitro-3,3'-diazenofuroxan, of a large amount of energy into a small 2,4-dinitrotoluene, erythritol tetranitrate, and volume. The rapidity of reaction is called the ethyl azide. Others are ethylene glycol shattering effect (or potential) or brisance dinitrate, FOX-7, HBT (explosive), (from the French meaning to "break") of the heptanitrocubane, hexamethylene triperoxide explosion. It is a property of the material and diamine, hexanitrobenzene, the degree of confinement. If an explosion is hexanitrodiphenylamine, and restrained initially, it can build up a large hexanitroethane. pressure and achieve the same effect. The Also, there are rapidity of the reaction is used as a method of hexanitrohexaazaisowurtzitane, classification of explosive materials hexanitrostilbene, HHTDD, HMX, lead (Urbanski, 2009). styphnate, lead(II) azide, manganese heptoxide, and mannitol hexanitrate. Again, Classification of explosive materials there are methyl azide, methyl nitrate, Explosive materials, which react very methylammonium nitrate, mononitrotoluene, violently (are brisant) are known as high nitramex and nitramon explosives, explosives. They are used solely for their nitrocellulose, nitrogen triiodide, and destructive power. In contrast, low nitroglycerin. Others are nitroguanidine, explosives are materials that react more nitromethane, nitrostarch, octaazacubane, slowly. They release a large amount of octanitrocubane, pentaerythritol tetranitrate, energy, but due to the relatively slow rate of pentazenium, and pentazole. Yet others are reaction the energy is more useful as a picric acid, picryl chloride, polyvinyl nitrate, propellant where the expansion of the gases potassium picrate, propylene glycol dinitrate, is used to move projectiles. An example RDX, silver acetylide,and silver azide would be gunpowder. It is true that (Cooper and Kurowski, 1996). confinement will increase the brisance of There are silver nitride, sodium azide, gunpowder, but there is a wide variety of styphnic acid, TATB, tetraazidomethane, materials that react much more quickly and tetranitromethane, tetrasulfur tetranitride, and violently than gunpowder (Fordham, 1980).

33 Eneh, O.C.: Chemical explosives: Warhead ally, Technoscience Review, 3(1&2), Nov., 2012

Barrier and initiation of explosive electricity. The ease of which an explosive reactions may be detonated is its sensitivity (Cooper The oxidation reactions that release energy in and Kurowski, 1996). explosive reactions do not occur For safety considerations, explosive spontaneously. There is usually some small materials are separated into three categories: barrier that must be overcome by the input of those which will detonate easily, called energy that will start the reaction, which then sensitive or primary explosives; those which will continue by itself until completion. The require slightly more energy to detonate, input of energy to overcome the barrier is called intermediate explosives; and those known as initiation (or detonation). which require relatively more energy to Sometimes, only mechanical force is detonate, called insensitive or secondary required, like in the case of nitroglycerin. explosives (Cooper, 2001). Other cases require heat, like from a match or

Chemical explosives and their uses Table 3.2 shows common explosives and their uses.

Table 3.2: Common explosives and their uses Primary H.E. Intermediate H.E. Secondary H.E. (detonators) (boosters) (main charges) Mercury fulminate Tetrytol RDX Lead azide PETN Comp-A,B,C Lead styphnate Tetryl Cyclotol Tetracene TNT HBX-1,3 DDNP H-6 MINOL 2 Ammonium picrate Source: Fas.org, 2011

Primary explosive materials are used to up of secondary (insensitive) material and detonate the entire explosive device. That is, cannot be detonated (Ledgard, 2004). they are usually connected to some external Once the fuse is installed, the entire device, which starts the detonation. In this device requires great care in handling to capacity, the primary explosive is called the prevent inadvertent detonation. Often, the fuse. The energy from the explosive device is configured so that the explosive detonation of the primary material is used to train must pass through a small physical port set off the booster which, in turn, sets off the that connects the fuse to the main charge. main charge, which is made up of secondary This port can be blocked until the device will (insensitive material). This combination of a be used. As an example, the port may consist small quantity of sensitive material used to of two rotating plates with off-centre holes. set off a large amount of secondary material When the plates are aligned, the two holes is known as the explosive train. It is called a will line up and permit operation. This is train because the events occur in sequence. called arming the device. Otherwise, the The main charge must be made up of holes will not be aligned and the device will insensitive material for the safety of those be safe. The mechanism with plates is called handling the device. In practice, the fuse is the safing and arming device. Other rarely stored with the device until it is configurations exist, but they all accomplish required for use. In this manner, the device the same function: to prevent inadvertent remains relatively safe, since it is only made detonation and permit detonation when authorized (Zukas et al, 1998).

34 Eneh, O.C.: Chemical explosives: Warhead ally, Technoscience Review, 3(1&2), Nov., 2012

Another type of initiation is During the 19th century, black powder was deflagration, in which the decomposition of replaced by nitroglycerine, nitrocellulose, the explosive material is propagated by a smokeless powder, dynamite and gelignite flame front, which moves slowly through the (the last two were invented by Alfred Nobel). explosive material. Deflagration is a World War II saw an extensive use of new characteristic of low explosive material, such explosives. In turn, these have largely been as gunpowder (Yinon and Zitrin, 1996). replaced by modern explosives, such as TNT. Early thermal weapons, such as Greek The increased availability of chemicals has fire, have existed since ancient times. But, allowed the construction of improvised the first widely used explosive in warfare and explosive devices (Carlucci, 1986). mining was black powder, invented in 9th century China. This material was sensitive to water, and evolved lots of dark smoke.

Implications for development Chemical explosives destroy lives and use of chemical explosives negates property. They also pollute and destroy the sustainable development. Therefore, life-sustaining environment. Whatever production and use of chemical explosives reasons and benefits they avail cannot justify ought to be discouraged in favour of Green the damage they occasion. Worse still, the Chemistry.

References Akhavan, J., 2011, The chemistry of Items in Nigeria,” Journal of Applied explosives, 3rd Edition, Royal Society Sciences, 11(2): 397-400. of Chemistry, Great Britain. Eneh, O.C. (2011b), “Environmental Army Research Office, 1964. Elements of Significance of the Combustion of Armament Engineering (Part One). Liquid Petroleum Fuels – A Review,” Washington, D.C.: U.S. Army Material Journal of Applied Sciences, 11(15): Command 2680-2685, DOI: 10.3923/jas.2011. Carlucci, D.E., 1986. Ballistics: Theory and Eneh, O.C. (2011c), “Enhancing Africa’s Design of Guns and Ammunition. Environmental Management: Integrated Available at: Pest Management for Minimization of http://www.amazon.com/Ballistics- Agricultural Pesticides Pollution,” Theory-Design-Guns- Research Journal of Environmental Ammunition/dp/1420066188 Accessed, Sciences, 5 (6): 521-9, DOI: January 26, 2012. 10.3923/jas.2011.521.529. Commander, Naval Ordnance Systems Eneh, O.C. (2011d), “A Review on Command, 1972. Safety and Petroleum: Source, Uses, Processing, Performance Tests for Qualification of Products, and the Environment,” Explosives. NAVORD OD 44811. Journal of Applied Sciences, 11 (12): Washington, D.C.: GPO. 2084-91. Cooper, P.W. and Kurowski, S.R., 1996. Eneh, O.C. and Agbazue, V.C. (2011), Introduction to the technology of “Protection of Nigeria’s Environment: explosives. Available at: A Critical Policy Review,” Journal of http://www.isee.org Accessed, January Environmental Science and 25, 2012. Technology, 4 (5): 490-497, DOI: Eneh, O.C. (2011a), “Recyclability Potentials 10.3923/jest, 2011. of Beryllium Oxide from E-Waste

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Eneh, O.C. and Agunwamba, J.C. (2011), 1812-5654 / DOI: “Managing Hazardous Wastes in 10.3923/jas.2011.3215.3220. Africa: Recyclability of Lead from E- Fas.org, 2011. Chemistry. Available at: Waste Materials,” Journal of Applied http://www.fas.org/man/dod- Sciences, 11(17): 3215-3220, ISSN 101/navy/docs/es310/chemstry/chemstr y.htm Accessed, November 11, 2011. Fordham, S., 1980. High explosives and http://www.amazon.com/Introduction- propellants. Oxford: Pergamonpress. Technology-Explosives-Paul- Ledgard, J., 2004. The preparatory manual of Cooper/dp/047118635X explosives, 3rd Edition. Available at: Yinon, J. and Zitrin, S. Modern Methods and http://www.rapidlibrary.com/file/the- Applications in Analysis of Explosives, preparatory-manual-of-explosives- 2nd Edition. New York: John Wiley third-edition-14 Accessed, November Inc. 14, 2011. Zukas, J.A., Walters, W. and Walters, W.P., Meyer, R., Köhler, J. and Homburg, A., 1998. Explosive Effects and 2007. Explosives. New York: Wiley- Applications. Available at: VCH. http://www.findpdf.net/about- Urbański, T., 2011. Chemistry and explosives-effects-and-applications- technology of explosives, Volume 3. download-html Accessed, January 26, Available at: 2012.

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