Article No : a10_143

Explosives

JACQUES BOILEAU, Consultant, Paris, France

CLAUDE FAUQUIGNON, ISL Institut Franco-Allemand de Recherches de Saint-Louis, Saint-Louis, France

BERNARD HUEBER, Nobel Explosifs, Paris, France

HANS H. MEYER, Federation of European Explosives Manufacturers, Brussels, Belgium

1. Introduction...... 621 3.5. Perforators, Shaped or Hollow Charges . . 634 2. Physical Properties and Chemical Reactions 624 4. Primary Explosives ...... 634 2.1. Detonation ...... 624 5. Secondary Explosives...... 636 2.1.1. Ideal Detonation ...... 624 5.1. Production ...... 636 2.1.2. Deflagration and Detonation...... 625 5.2. Specific Secondary Explosives ...... 637 2.2. Prediction of Detonation Data ...... 625 5.2.1. Nitrate Esters ...... 637 2.2.1. Complete Calculation ...... 625 5.2.2. Aromatic Nitro Compounds ...... 639 2.2.2. Approximation Methods ...... 625 5.2.3. N-Nitro Derivatives ...... 641 2.3. Nonideal Detonation Waves and Explosives 626 6. High Explosive Mixtures ...... 643 2.3.1. Nonideal Explosive Compositions ...... 627 6.2. Desensitized Explosives ...... 643 2.3.2. Detonation of Cylindrical Cartridges ...... 627 6.3. TNT Mixtures ...... 644 2.3.3. Low- and High-Order Detonation Velocity . . 628 6.4. Plastic-Bonded Explosives (PBX)...... 644 2.3.4. The Effect of Confinement...... 628 7. Industrial Explosives ...... 645 2.4. The Buildup of Detonation...... 629 7.1. Dynamites ...... 645 2.4.1. Combustion – Deflagration – 7.2. Ammonium Nitrate Explosives Detonation Transition (DDT) ...... 629 (Ammonites) ...... 646 2.4.2. Shock-to-Detonation Transition (SDT) ..... 629 7.3. Ammonium Nitrate/Fuel Oil Explosives 2.4.3. Shock and Impact Sensitivity ...... 630 (ANFO/ANC Explosives) ...... 647 2.5. Classification of Explosives ...... 630 7.4. Slurries and Water Gels ...... 647 2.6. Functional Groups...... 631 7.5. Emulsion Explosives ...... 647 2.6.1. Nitro Group ...... 631 7.6. Uses ...... 648 2.6.2. Other Groups ...... 631 8. Test Methods ...... 649 3. Application ...... 632 8.1. Performance Tests ...... 649 3.1. Energy Transfer from the Explosive to the 8.2. Safety...... 650 Surroundings ...... 632 9. Legal Aspects and Production ...... 651 3.1.1. Shock and Blast Waves ...... 632 9.1. Safety Regulations ...... 651 3.1.2. Casing and Liner Acceleration ...... 632 9.2. Production of Military Explosives ...... 651 3.2. High Compression of Solids...... 633 10. Toxicology and Occupational Health ..... 652 3.3. Metal Forming and Welding ...... 633 References ...... 652 3.4. Rock Blasting ...... 634

1. Introduction 2. Chemical explosions are caused by decompo- sition or very rapid reaction of a product or a An explosion is a physical or chemical phenome- mixture non in which energy is released in a very short 3. Nuclear explosions are caused by fission or time, usually accompanied by formation and vig- fusion of atomic nuclei orous expansion of a very large volume of hot gas: 4. Electrical explosions are caused by sudden strong electrical currents that volatilize metal 1. Mechanical explosions are caused by the wire (exploding wire) sudden breaking of a vessel containing gas 5. Astronomical explosions are caused by solar under pressure flare activity on most stars

2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/14356007.a10_143.pub2 622 Explosives Vol. 13

6. Natural explosions are caused, e.g., by volca- The distinctions between these three classes nic eruptions when evaporation of dissolved are not clear-cut because most explosives burn gas in the magma results in a rapid increase in smoothly if they are not confined. However, if volume some fine hunting powder burns under certain confined conditions, combustion may become Only chemical explosions are treated in this detonation. Dry nitrocellulose fibers can easily article. detonate, but this tendency is significantly lower For an explosion to occur, the reaction must be in the gelatinized form. Some compositions, such exothermic; a large amount of gas must be pro- as mixtures of cyclotrimethylenetrinitramine duced by the chemical reaction and vaporization (RDX) with a binder, can be used as a propellant, of products; and the reaction must propagate very gunpowder, or high explosive, depending on the fast. For example, gasoline in air burns at a rate of type of initiation. ca. 106 m/s; a solid propellant, at ca. 102 m/s; The third class consists of primary and sec- and an explosive detonates at a rate of ca. 103 – ondary explosives. Primary explosives like lead 104 m/s (detonation velocity). azide (initiator explosives) detonate following The two different modes of decomposition are weak external stimuli, such as percussion, fric- deflagration and detonation. Deflagration exhi- tion, or electrical or light energy. Secondary bits two characteristics: 1) the combustion is very explosives such as pentaerythritol tetranitrate rapid (1 m/s up to a few hundred meters per (PETN) or 2,4,6-trinitrophenyl-N-methylnitra- second) and 2) the combustion rate increases mine (Tetryl) are much less sensitive to shock. with pressure and exceeds the speed of sound in However, they can detonate under a strong stim- the gaseous environment, but does not exceed the ulus, such as a shock wave produced by a primary speed of sound in the burning solid. The materials explosive, which may be reinforced by a booster are often powdered or granular, as with certain composed of a more sensitive secondary explo- pyrotechnics and black powder. Detonation is sive. The various secondary explosives are used chemically the same as deflagration, but is char- militarily or industrially as shown in Figure 1. acterized by a shock wave formed within the decomposing product and transmitted perpendic- Functions and Constraints. Explosives ularly to the decomposition surface at a very high can be either pure substances or mixtures. They velocity (several thousand meters per second) function in such systems as munitions, where independent of the surrounding pressure (see they are a component of a complex firing system, Chap. 2). or as firing devices in mining, quarries, demoli- Explosive substances can be divided into tion, seismic exploration, or metal forming three classes. Members of the first class detonate equipment. With such systems, the ingredients accidentally under certain conditions. These are must fulfill one or more functions, while meeting explosible substances, some of which are used in various constraints arising in manufacture or use. industry as catalysts (e.g., peroxides), dyes, and Therefore, tests that represent these functions fertilizers. This class includes products or mix- and constraints are required. tures whose formation must be avoided or When an explosive detonates, it generates a controlled, e.g., firedamp, or peroxides in ethers. shock wave, which may initiate less sensitive In the second class are products normally used for explosives, cause destruction (shell fragments, their quick burning properties but which may blast effect, or depression effect), split rocks and detonate under some circumstances, e.g., pyro- soils, or cause formation of a detonation wave. A technic compositions, propellants, and some detonation wave of special geometry (hollow- kinds of hunting powder. In the third class are charge effect) may modify materials by very substances intentionally detonated for various rapid generation of high pressure; for example, purposes. shaped charges, metal hardening, metal-powder For reasons of safety, acquaintance with the compaction, or transformation of crystalline first group of materials is necessary. The second forms. Shaped charges can be applied for the group is described elsewhere (! Propellants; destruction and demolition of large obsolete ! Pyrotechnics). Pure substances and mixtures structures by causing inward collapse. Shaped of the third class are described here. charges (so-called perforators) are also used in Vol. 13 Explosives 623

Figure 1. Differentiation of explosible materials the exploitation of petroleum and natural gas throughout Western Europe during the 1600s. wells to perforate the metal casing of the well Ammonium perchlorate was discovered in 1832. and thus allow the influx of oil and gas. A shock The development of organic chemistry after wave may be used to transmit signals, e.g., for 1830 led to new products, although their explo- safety devices or in seismic prospecting. sive properties were not always immediately In general, constraints are related to safety, recognized. These include nitrocellulose and security, stability, compatibility with other ele- nitroglycerin. ments of the system, vulnerability, toxicity, eco- The very important contributions of ALFRED nomics, and, more recently, environmental and NOBEL (1833 – 1896) include the use of mercury disposal problems [21]. fulminate in blasting caps for the safe initiation of explosives (1859 – 1861), the development of History [1, 4, 88]. Explosives were proba- dynamites (by chance NOBEL found that when bly first used in fireworks and incendiary devices. nitroglycerin was mixed in a ratio of 3:1 with an The admixture of saltpeter with combustible absorbent inert substance like Kieselgur (diato- products such as coal and sulfur produced black maceous earth) it became safer and more conve- powder, already known in China in the 4th nient to handle, and this mixture was patented in century A.C., described in 808 A.C. by Qing- 1867 as Dynamite), and the addition of 8 % Xu-Zi, and mentioned as a military gunpowder in nitrocellulose (gun cotton) to nitroglycerin a book published in 1044. The use in shells during (Gelignite or blasting gelatine, 1876). the Mongolian wars around 1270 and a severe Many new products were developed between explosion in a factory in 1280 were described. 1865 and 1910, such as nitrated explosives, The first correct description of the phenomenon mixtures in situ of an oxidizer and a fuel, ex- of shock waves in air seems to be in a book by the plosives safe in the presence of firedamp, chlo- scientist Song-Ying-Xing in 1637. Around 1580 rate explosives, and liquid oxygen explosives. first descriptions in Europe are known (siege of Organic nitro compounds for military uses in- Berg-op Zoom). However, the difficulties of cluded tetryl, trinitrophenol, and trinitrotoluene. initiation upon impact against the target were Between the two world wars, RDX, pentaer- not overcome until 1820 when fulminate caps ythritol tetranitrate (PETN), and lead azide were were developed. In the early 1600s, black powder produced. After 1945 cyclotetramethylenetetra- was used for the first time to break up rocks in a nitramine (HMX), 1,3,5-triamino-2,4,6-trinitro- mine in Bohemia. This technique spread benzene (TATB), and hexanitrostilbene (HNS) 624 Explosives Vol. 13 were developed (see Chap. 5), as well as ‘‘fuel – Stationarity requires the plane corresponding air explosives’’. Ammonium nitrate – fuel oil to the end of the reactions to be locally sonic. This (ANFO/ANC) explosives, slurries, and emulsion condition, termed the Chapman – Jouguet (CJ) explosives were developed for industrial uses; condition [23, 24], yields the relation D ¼ uþc some were improved by adding glass bubbles needed to solve the equations of conservation of (microspheres), micropores, and/or chemical flow (where D ¼ detonation velocity, u ¼ par- gassing. ticle velocity, and c ¼ sound velocity). In the 1880s BERTHELOT described the phe- The structure of the reaction zone of the ID nomenon of detonation. About the same time the plane detonation can be ignored, and the me- hollow-charge effect was discovered, and the chanical and thermodynamic data can be calcu- foundations of the hydrodynamic theory of deto- lated by solving equations between the non- nation were established. In 1906, the first accu- reacted and fully reacted states. The description rate measurements of velocities of detonation of the ideal detonation is given by the model were made. After World War II, the science of [25–27] represented in Figure 3 by the p – V detonation was further developed and perfected plane (Fig. 3 A) and the pressure p vs. distance [17]. x profile at a given instant of time (Fig. 3 B). This Recently, new explosive compositions of low model relates the explosive at rest (V0), the vulnerability (LOVA ¼ low vulnerability am- shocked nonreacted explosive [ZND spike (*)], munitions) are being developed. Major efforts and the end of the reaction zone [CJ plane ð^Þ]. are being made to use predicted properties (e.g., This model has been experimentally ascertained density, DHf, sensitivity, themal stability) to [28]. avoid unnecessary experiments [18, 19, 95, 103]. In Figure 3 A the three states are located on a straight line (Rayleigh line), with slope equal to 2= 0. The loci of the shocked states are D V2 2. Physical Properties and Chemical termed Hugoniot curves: H0 for the unreacted Reactions explosives, and H for the completely reacted explosives. 2.1. Detonation Some relations at the CJ plane can be ex- pressed as a function of D and the polytropic The detonation process needed for most uses is coefficient of the detonation products: characterized by a shock wave that initiates ! q r^ chemical reactions as it propagates through the G ¼ log q V^ explosive charge. The shock wave and reaction log s zone have the same supersonic velocity; a frac- tion of the chemical energy is used to support the shock.

2.1.1. Ideal Detonation

A model of ideal detonation (ID) is shown in Figure 2, with steady flow to the end of the reaction zone.

Figure 3. Development of the ideal detonation A) The p–Vplane; B) The pressure vs. distance profile; p pressure; V specific volume; D detonation velocity; H0 Hugoniot curve of nonreacted explosives; H Hugoniot curve of reaction products; (0) explosive at rest; (1) reaction zone of length a, an arbitrary quantity; (2) isentropic release of the Figure 2. Ideal detonation detonation product Vol. 13 Explosives 625

The notation ( )s represents the derivative effectiveness of the explosive on the surround- along the isentrope at the CJ point. ings in a given action. The calculation of these quantities requires the equation of decomposi- D D2 u^ ¼ p^ ¼ r^ tion, the heats of reaction, and an equation of state Gþ1 0 Gþ1 for the reaction products, which may be theoreti- G Gþ1 cal (virial expansion) [30, 31], semiempirical ^c ¼ D r^ ¼ r Gþ1 0 G [32], empirical [33], or a constant G law. In addition, the equilibrium constants for the reac- where r ¼ density tion given as a function of V and T are needed. These relations are valid for most condensed For organic explosives, the distinction between organic explosives G 3, with the assumptions oxygen-positive or weakly oxygen-negative ex- that p0 ¼ 0 and u0 ¼ 0. plosives, which give only gaseous products, and the strongly oxygen negative explosives, which 2.1.2. Deflagration and Detonation also give free carbon, is important. In fact, the assignment to one class or the other is determined In a thermodynamic diagram such as Figure 3 A, by the values of the equilibrium constants for there is another point that satisfies the Chap- (V^; T^) determined after a first calculation. ^ ^ man – Jouguet condition in the region p ^ < p p0 p p0 The thermochemical equations are solved U^ > 0 ^u < 0 ^ ^ V < V0 V > V0 with a priori (V,T) pairs to give gas product composition. The mechanical equations are then applied at the Chapman – Jouguet plane with the Unlike the detonation wave, the deflagration geometric condition represented on Figure 3 A: wave is subsonic, and consequently a precursor at the CJ point, the isentropic and the Hugoniot shock is propagated in front of the reaction zone. curves have the same tangent, with a slope equal to 2= 0. Its intensity and velocity depend on the chemical D V2 energy released and on the boundary conditions; in contrast to detonation, a specific explosive does not provide a unique solution for 2.2.2. Approximation Methods deflagration. A precursor shock that is strong enough can, in A first prediction of the CJ data can be given by addition to compressing the explosive, also heat using methods valid for condensed explosives. it sufficiently to initiate reactions just behind its front; a progressive buildup of a completely Chemical Potential. For many organic ex- stationary process identical with the ZND model plosives, D and p^ can be expressed simply as a of the detonation is observed. Consequently, a function of a parameter F defined as [34]: detonation is equivalent to a shock followed by a qffiffiffiffiffiffiffiffiffiffi deflagration. F ¼ N M Q r

2.2. Prediction of Detonation Data N ¼ number of moles of gaseous products per gram ¼ average molecular mass of these pro- 2.2.1. Complete Calculation [29] Mr ducts, g/mol The quantities D, p^, u^, V^, and T^in the Chapman – Q ¼ enthalpy of the explosive minus the Jouguet state are needed to evaluate further the enthalpy of the products, J/g 626 Explosives Vol. 13

The calculation of F is made under the as- n (O) ¼ number of oxygen atoms sumption that: n (N) ¼ number of nitrogen atoms n (H) ¼ number of hydrogen atoms

OþH!H2O n (F) ¼ number of fluorine atoms n (HF) ¼ number of hydrogen fluoride mo- OþC!CO2 lecules that can form from avail- able hydrogen i.e., the formation of water is considered before n (B/F) ¼ number of oxygen atoms in excess the formation of carbon oxides. of those available to form CO2 and H2O or the number of fluorine The following relations are then proposed: atoms in excess of those available pffiffiffiffi to form HF D ¼ Að þBr Þ F 1 0 n (C) ¼ number of oxygen atoms doubly ^ ¼ K r2F p 0 bonded to carbon as in a ketone or ester A good fit with experimental data is found for n (D) ¼ number of oxygen atoms singly organic explosives by setting bonded to carbon as in C–O–R where R ¼ H, NH4, C, etc. A ¼ : B ¼ : K ¼ : 1 01 1 3 15 58 n (E) ¼ number of nitrato groups existing This method, which requires only knowledge as a nitrate ester or as a nitric of the equation of decomposition, is useful for acid salt such as hydrazine comparing organic explosives. mononitrate

Rothstein Method. An empirical correla- Molecular masses and atomic composition for tion has been found between the detonation explosive mixtures must be derived as sums of velocity D and a parameter F, which is a function mass-average molecular mass and of elemental of the explosive molecule [35]. mole fractions. The prediction of the detonation velocity is ca. 95 % accurate. F : Dðr Þ¼ 0 26 ðr r Þ 0 3 TM 0 0:55 2.3. Nonideal Detonation Waves and Explosives rTM ¼ theoretical density This correlation applies to both organic nitro A detonation wave is nonideal if the geometry and fluorinated nitro explosives. and dimensions of the charge are such that the reaction zone is affected by lateral shock or 0 1 * rarefaction waves. Consequently, the nonideality nðHÞnðHFÞ nðOÞþnðNÞþnðFÞ@ A depends strongly on the dimensions of the charge 2nðOÞ F ¼ and the explosive composition characterized by a 100 M r given reaction zone length. A ð = Þ ð Þ ð Þ ð Þ An explosive composition consisting of com- n B F n C n D n E 3 1:75 2:5 4 5 ponents with different reaction kinetics does not þ G 100 M satisfy the ideal detonation model, which as- r sumes all the exoenergetic reactions to be com- pleted simultaneously in the sonic Chapman – where n (F), n (HF), and n (B/F) are the elemen- Jouguet plane. Such compositions are nonideal tal terms for fluorinated explosives, and where explosives. The ideal detonation model applies G ¼ 0.4 for each liquid explosive component, only as an approximation to most multicompo- G ¼ 0 for solid explosives, and A ¼ 1 if the nent explosives; however, with data on reaction compound is aromatic; otherwise A ¼ 0. * If kinetics under pressure often lacking, calcula- n (O) ¼ 0orifn (HF) > n (H), this term ¼ 0. tions are commonly based on the ideal detonation For 1 mol of composition: model. Vol. 13 Explosives 627

2.3.1. Nonideal Explosive Compositions

An example of an organic explosive with a metallic nonexplosive additive is a dispersion of aluminum grains or flakes in a cast organic explosive. The process sequence is shown in Figure 4. The energy effectively supporting the detonation wave has been delivered at time tA. The absorption of energy by aluminum reduces p^ and D, but the late combustion of the aluminum allows the pressure to be sustained behind the CJ plane, thereby increasing the total impulse trans- mitted to the surroundings. Figure 5. Sequence of reactions: explosive and oxygen-rich binder The possible sequence of an organic explosive a) Negative-oxygen-balance explosive; b) Oxygen-contain- (a) with a negative oxygen balance cast or ing binder pressed with a binder containing oxygen (b) is shown in Figure 5. The relatively slow decom- position of the binder produces oxygen gas, which shifts the reaction of the organic explosive between components, the specific surface areas toward better oxygen balance, thus increasing become important. Moreover, because the total energy production. reaction zone is relatively long, detonation de- A typical example of a mixture of two explo- pends on the dimensions of the charges. sive components with different reaction kinetics is a mixture of trinitrotoluene (TNT) and ammo- nium nitrate (AN). The slower reaction of AN 2.3.2. Detonation of Cylindrical produces energy and an excess of oxygen, which Cartridges shifts the equilibrium of the TNT reaction to a higher energy release. Because the detonation of In the detonation of cylindrical cartridges, the the nonideal explosives involves heat transfer reactive flow is two-dimensional, stationary, and relatively easy to model. Many military or engi- neering applications use cylindrical geometry. The basic phenomenon is the interaction of the inwardly propagating rarefaction fan, origi- nating at the outer surface as it is reached by the shock wave, with the reaction zone. The first consequence of this interaction is freezing of the reactions by cooling, which reduces the released energy. A second effect is a curvature of the detonation front and a loss in energy through a diverging flow. The reaction zone length and the radius of the cartridge are two quantities that play opposite roles in the process. The experimental determination of the deto- nation velocity as a function of the diameter produces a curve limited in two ways:

1. As the diameter increases, the detonation velocity D approaches a constant value Di equal to that of the ideal detonation wave. 2. Below a given diameter d, called the critical Figure 4. Sequence of reactions: explosive and combustible additive diameter, dcr , the detonation is no longer self- a) Cast organic explosive; b) Aluminum grains or flakes supporting and fails. 628 Explosives Vol. 13

Figure 7. Detonation velocity D vs. diameter d for several Figure 6. Detonation velocity D vs. diameter d for two grain sizes of powered TNT densities r of 60 wt % RDX – 40 wt % TNT g

Many analytical expressions D ðdÞ have been shock waves [36]. Conventional examples are the proposed in which the explosiveD isi characterized dynamites and highly porous explosives [38]. by its ideal reaction zone length. The function The high sensitivity to shock waves tends to D (d) and the critical diameter dcr depend on both allow the detonation to be sustained. This is true the length and the structure of the reaction zone, even when the development of the reactions is i.e., on factors that affect this zone, such as the seriously limited by the size of the cartridge. loading density r0, grain size g, initial tempera- Thus, under steady conditions, a state of shock ture t0, and composition, especially in the case of plus reaction would correspond to that appearing mixtures. in a transient regime in the buildup of heteroge- As an example of the effects of these factors neous explosives to detonation. on ideal explosive compositions, the influence of r0 is shown in Figure 6 for the conventional military composition 60 RDX/40 TNT (compo- 2.3.4. The Effect of Confinement sition B) [36]. In the case of energy-rich explo- sives, the effect of the cylinder diameter Confinement usually delays the arrival of the increases with decreasing density, whereas the expansion waves on the axis. A confined charge critical diameter decreases with increasing den- is equivalent to a charge having a large diameter. sity and increasing temperature [37]. The influ- However, two anomalous effects should be not- ence of mean grain size, e.g., that of powdered ed: if the velocity of sound in the confinement TNT, is shown in Figure 7 [29], and most exceeds the detonation velocity for the given nonideal explosive compositions and some pure diameter, a foreshock is propagated ahead of the explosives exhibit a particular behavior (see wave. This foreshock can accelerate the wave Chap. 6). (increase the density) or stop the detonation, i.e., desensitize a porous explosive by compaction, the explosive becoming homogeneous. An anal- 2.3.3. Low- and High-Order Detonation ogous desensitizing effect can be generated if Velocity there is an air gap between the explosive and the container. The expanding reaction products adi- Some explosives exhibit two different detonation abatically compress the porous explosive. This velocities, depending on the diameter of the effect can stop the detonation of mining charges cartridge and the initial ignition energy. Such embedded in boreholes (so-called dead pressing explosives always have a relatively low energy process, especially observed in emulsion and loading density, with great sensitivity to explosives). Vol. 13 Explosives 629

2.4. The Buildup of Detonation

2.4.1. Combustion – Deflagration – Detonation Transition (DDT)

Deflagration can generate a shock wave, which is propagated in the unreacted medium, and if strong enough, can initiate reactions and become a detonation wave. This transition can occur only if the explosive charge is confined or is of such a size that expansion waves do not prevent forma- tion of a shock wave. Accident reports have shown that DDT affects a variety of explosives Figure 8. Detonation buildup (SDT), homogeneous and propellant charges. explosive However, different phenomena, which de- pend on the mechanical properties of the medi- um, may occur [39, 40]: if the explosive is porous completed along the entrance side (b) at time t, or exhibits poor mechanical behavior, the gas the detonation appearing at point A. The detona- formed and subjected to pressure is injected tion wave (c) travels in a compressed medium between the grains or into cracks, increasing the heated by shock wave (a). Therefore, the deto- combustion surface. The resulting acceleration nation wave (c) travels with a velocity exceeding stops only when detonation occurs. The path the normal detonation velocity, which is attained versus time of the observed ionization front is at point B (wave d) as soon as wave c has reached continuous. In the case of explosives stiff enough wave a. to withstand an elastic wave, a steady deflagra- tion develops as soon as the pressure makes the Heterogeneous Explosives. In Figure 9, medium impervious to the gas. The transition to the shock wave (a) is gradually accelerated by detonation occurs as the pressure of the gas the energy released upon its passage. Its acceler- formed behind the deflagration zone becomes ation ends with the appearance of a detonation high enough to generate a shock wave. Detona- wave at point B. This wave is characterized by its tion occurs when the shock wave reaches the luminosity, as seen on optical records. Some- front of the deflagration wave. As a consequence, times a second wave starts from point B and a discontinuity is observed in the path versus time moves backward in the explosive, which has of the ionization front. reacted only partially (retonation wave). The macroscopic analysis can be explained by the

2.4.2. Shock-to-Detonation Transition (SDT)

If the end of an explosive charge is subjected to a shock wave, the steady detonation appears only at a distance s and with a delay t inside the explosive charge [41]. For a given composition, s and t are inversely proportional to the intensity of the shock wave. There are two SDT processes: one for homogeneous (for instance, a liquid) and one for heterogeneous composition.

Homogeneous Explosives. The shock wave (a) in Figure 8 propagated at constant velocity Figure 9. Detonation buildup (SDT), heterogeneous initiates decomposition reactions that are first explosive 630 Explosives Vol. 13 microscopic heterogeneities of the explosive theory (with initial temperature T * expressed as [42]. a function of pressure p*) accurately reproduces The energy of the shock wave is converted the experimental findings. The critical time t*is into heat energy by the implosion of occluded gas equal, for a given shock pressure, to the time of bubbles, the impact of microjets, or the adiabatic the shock-to-detonation transition (see Fig. 8). shearing of the powder grains. All the observa- Except for primary explosives, the sensitivity to tions allow for two successive phases, ignition shock-wave action and the shock-to-detonation and buildup, that are accommodated by numeri- transition are both dependent on the homogeneity cal models assuming inward or outward combus- of the composition. Sensitivity is affected by tion of the grains [43]. grain size [104] and internal grain defects [105]. The reaction of an explosive to impact loading depends on several factors. If the projec- 2.4.3. Shock and Impact Sensitivity tile is a large plate, the reaction is identical with that observed in the preceding case: the shock The sensitivity of the explosives to an applied wave induced by the impact depends on the load is measured by the maximum load at which velocity and acoustic impedance, whereas the no detonation occurs, or at which there is a 50 % action time is proportional to the plate thickness. occurrence of detonation, i.e., a 50 % chance of In tests of sensitivity to shock-wave action, the failure. The sensitivity to shock loading depends impacting plates are driven by explosives. If the on the pressure p* and its action time t*. Sensi- projectile is a small sphere or cylinder, the inter- tivity is defined with the aid of the curve p*(t*), action with the target becomes complex [41]. If which separates detonation points from failure the shock wave cannot induce a shock-to-deto- points. nation transition, it degenerates into an adiabatic For a variety of explosives and for a certain compression. Frictional and shearing effects can pressure range, the sensitivity is defined by the cause ignition. Finally, a phenomenon analogous relation ðpÞ2t ¼ e, where e is a constant that to the deflagration-to-detonation transition (see depends on the composition and exhibits the Section 2.4.1) is observed, in which the mecha- dimension surface energy per unit area [44]. nical properties of the explosive play a part. Figure 10 shows that the concept of the ener- gy threshold is an acceptable approximation for solid-state compositions [45]. For liquid explo- 2.5. Classification of Explosives sives, which exhibit different behavior, the rela- tion t*(p*), based on an Arrhenius-type kinetic For many years the behavior of cylindrical car- tridges, as described in Section 2.3.2, was re- garded as typical of ideal explosives. A detailed analysis has shown, however, that classification of explosives into two groups is possible, taking into account the influence of the loading density r0 on the detonation velocity as a function of the cartridge diameter and the critical diameter [46]. The first group includes a variety of organic explosives: TNT, RDX, HMX, and their mix- tures (see Chap. 5). The second group includes mixtures of an explosive and a combustible nonexploding constituent (nonideal composi- tion). This group also includes some pure ex- plosives such as hydrazine mononitrate (HN), nitroguanidine (NG), ammonium nitrate (AN), dinitrotoluene (DNT), dinitrophenol (DNP), and ammonium perchlorate (AP). The behavior of the second group is illustrated for ammonium Figure 10. Initiation energy threshold vs. shock pressure a, b) HMX plus binder; c, d) Cast RDX compositions perchlorate in Figure 11. Vol. 13 Explosives 631

nitrates, ammonium nitrate, and the nitrates of methylamine, urea, and guanidine. These are usually low-density, water-soluble, sometimes hygroscopic compounds. With the exception of some salts of hydrazines, e.g., triaminoguanidine and hydrazine nitrates, they are insensitive to impact and friction.

O-Nitro Derivatives, Nitrate Esters (RONO2). The low molecular mass represen- tatives are liquids or low-melting solids. They are sensitive to impact when the number of carbon atoms and ONO2 groups are equal or nearly equal. Densities are in the medium range, except for symmetrical molecules such as pentaerythri- tol tetranitrate (PETN). Heat stability is moder- ate; they are subject to hydrolysis and autocata- lytic decomposition.

C-Nitro Derivatives (CNO2). Aliphatic and cycloaliphatic nitro compounds differ great- ly from the aromatic and heteroaromatic series. Members of the first group have limited explo- sive properties, except when the number of NO2 groups equals or exceeds the number of carbon atoms, as in some gem-dinitro compounds and derivatives of nitroform, HC(NO2)3. The latter are often shock-sensitive, with limited heat sta- bility. The compounds RCF(NO2)2 are stable to heat and rather insensitive [6, 7]. Members of the second group containing two or three NO2 groups per ring are valuable; they are often dense and insensitive to impact, with good hydrolytic and Figure 11. Detonation behavior of ammonium perchlorate; thermal stability. h ¼ percent of the theoretical maximum density

N-Nitro Derivatives (NNO2). N-Nitro de- 2.6. Functional Groups rivatives are often difficult to synthesize. They exhibit high densities and detonation velocities, Certain groups impart explosive potential. with some sensitivity to impact. RDX and HMX are representative.

2.6.1. Nitro Group 2.6.2. Other Groups The nitro group is present in the form of salts of nitric acid, ONO2 derivatives (nitrate esters), Organic chlorates and perchlorates, peroxides, CNO2 derivatives (aliphatic or aromatic nitro metal salts of some organic compounds (acety- compounds), and NNO2 derivatives (N-nitro lides and nitronates), and some organic com- compounds such as nitramines, nitroureas, etc.). pounds with three-membered rings or chains of nitrogen atoms or triple bonds have only limited Salts of Nitric Acid. Salts of nitric acid application, except as primary explosives. Most include the alkali metal and alkaline earth metal are very dangerous to handle. 632 Explosives Vol. 13

Nitroso (NO) compounds are usually unstable. So-called hexanitrosobenzene is an exception; however, it is actually not a nitroso compound but a furoxan derivative (benzotrifuroxan). It is of interest because it is free of hydrogen (zero- hydrogen explosive). Other furoxanes and also furazanes have explosive properties [89]. The difluoroamine group imparts explosive character, increased density and volatility, a lower melting point and detonation velocity, and often much higher impact sensitivity. These compounds resemble primary explosives. Figure 12. Determination of shock pressure p and particle Many metal azides are primary explosives. velocity u induced in an inert material by an explosive; Some organic azido derivatives are being studied PMMA ¼ poly(methyl methacrylate) because of their high density and stability. How- ever, polyazido compounds can be very sensitive. flight. During wave propagation in the surround- ing medium, the intensity of a shock wave de- creases and the pressure profile changes. At a 3. Application given distance from the charge, compression alternates with tension. The mechanical effects 3.1. Energy Transfer from the are a function of the maximum pressure and of Explosive to the Surroundings the positive and negative impulses comprising the so-called blast wave. The maximum and The energy available in the gaseous reaction minimum pressures are represented in Figure 13 products is transferred to the surroundings by as a function of the reduced distance R/m1/3 from shock waves. The mechanical effects depend on the charge. the geometry of the charge and the surroundings, on the distance from the charge, and on the acoustic impedance of the media. The explosive 3.1.2. Casing and Liner Acceleration energy is used either to create compression and tension for engineering applications or to accel- A casing or liner in contact with an explosive erate projectiles for military applications. charge is accelerated by a three-step process:

3.1.1. Shock and Blast Waves

The highest dynamic pressures are produced at the exit end of the charge, where the detonation shock is transferred to the inert material. The shock pressure is a function of the shock imped- ance. It is defined by the so-called shock polar curve of the pressure (p) vs. particle velocity (u). By a graphical method (Fig. 12) the induced pressure can be determined at the intersection of a shock polar curve with the detonation gas- product curve passing through the CJ point. Even higher pressures can be obtained by using converging geometries or, indirectly, by a two-stage device. The explosive accelerates a Figure 13. Front pressure pf and minimum pressure pmin in thin metal plate, which generates an intense air vs. reduced distance R/m1/3 from TNT in air, where R is the shock in the solid specimen as it strikes it in free distance in meters and m the mass in kilograms Vol. 13 Explosives 633

1. u1 given by the shock wave 2. u2 2 u1 given by reflection of the shock wave in a release wave at the free surface 3. u3 given by the further expansion of the gaseous detonation products

The Gurney formula gives an approximate u3 for a casing filled with an explosive characterized by the quantity E, which is given in J/kg [47]:  M 1=2 ð = Þ¼ð EÞ1=2 þa u3 m s 2 C where

M ¼ mass of the casing, kg Figure 14. Setups for metal forming C ¼ mass of the explosive, kg A) Free forming; B) Bulkhead forming a ¼ 0.5 for a cylindrical charge and a ¼ 0.6 for a spherical charge

3.2. High Compression of Solids 3.3. Metal Forming and Welding

Explosives provide the most powerful means for The detonation of an explosive charge is used to compressing solids in spite of the fact that at high form a metal plate; the shock wave is moderated pressure the heating limits the volume reduction. by a liquid transmitting medium (Fig. 14). Tech- niques of free forming (Fig. 14 A) or bulkhead Production of New Crystal Phases. The forming (Fig. 14 B) may be used. high pressure generated by shock waves may be A grazing detonation may weld two metal used to transform one crystal phase into another plates (even different metals such as titanium on (polymorphic transformation). The best-known steel or aluminum on copper) with diffusion of example of this technique is the transformation metal through the interface (Fig. 15) [49]. The of graphite into diamond. Unfortunately, the required collision velocity vc depends on the short duration of the shock limits this technique materials and the types of explosives used. This to the production of small crystals used as process is called explosive welding or metal abrasives. cladding.

Powder Compaction. The compression of powders by shock waves produced by explosives creates high pressures and temperatures simulta- neously, resulting in grain welding. The main problem, which has been solved only recently, is the explosion caused by the interaction of release waves, which follow the shock; special geome- tries are required [48]. Rapidly solidified amor- phous and metastable microcrystalline materials and ultrahigh-strength ceramics are expected to be produced by this technique.

Shock Hardening. The detonation of a thin sheet of explosive covering a piece of steel creates great surface hardness by a sequence of rapid compression, heating, and cooling. Figure 15. Explosive welding or cladding 634 Explosives Vol. 13

3.4. Rock Blasting [36]

In rock blasting the explosive systems are placed in blast holes, which are usually drilled in defined distances and angles into the bench and/or the wall of the quarry. With strong confinement, which is usually achieved by stemming the bore- hole, most of the explosive energy is usefully employed, even though some of it is released by afterburning. Depending on the specific require- ments of the quarry, the geological/petrological conditions, the required rock fragmentation, the cost effectiveness, and the environmental para- meters (ground vibration, dust, noise, air blast), the blasting specialists determine which blasting system should be applied to optimize the overall Figure 16. Projectile formation performance and results. This refers to selection of the correct type of explosives, for example, cartridged products such as dynamites or emul- the liner and can be > 10 times the diameter of sions; bulk emulsion explosives which are man- the charge. ufactured from non-explosive substances on the When the projectile strikes a solid or liquid bench by so-called mobile emulsion manufactur- target, it drills a deep, narrow hole. The hole ing units (MEMUs) and pumped directly into depth is given approximately by the expression blast holes on demand; ANFO in packaged form P sffiffiffiffi or from bulk trucks, and an appropriate initiation r P ¼ L j system (electrical, nonelectrical, or electronic r detonators, detonating cords, and delay relays or t combinations thereof). Various types of wedge where L is the length of the projectile and rj cuts are used for underground blasting ope- and rt are the densities of the projectile and rations. target.

3.5. Perforators, Shaped or Hollow 4. Primary Explosives Charges Under low-intensity stimulus of short duration, An explosive can be used to produce a thin, primary explosives, even in thin layers, decom- high-speed metallic projectile capable of perfo- pose and produce a detonation wave; the activa- rating armor [50]. Nonmilitary applications in- tion energy is low. The stimulus may be shock, clude oil (perforators) and the demolition of friction, an electric spark, or sudden heating. The structures. deflagration – detonation transition occurs with- A cavity in the explosive (Fig. 16) is lined in a distance often too short to be measured. The with a metal, usually copper. The detonation released energy and the detonation velocity of divides the liner into two parts that move along primary explosives are small. Their formation is the axis at different velocities. Most of the mass often endothermic. of the liner forms the so-called slug at a velocity The main function of primary explosives is to of several hundred meters per second. The re- produce a shock wave when the explosive is mainder forms a thin projectile which is elongat- stimulated by percussion, electrically, or optical- ed because of the difference of velocity between ly (laser), thus initiating a secondary explosive. the first formed elements near the apex (ujet Primary explosives are the active detonator in- max. 8000 – 11 000 m/s) and those formed gredients. Some are used in primer mixtures to last (ujet min. ¼ 1500 – 2000 m/s). The ultimate ignite propellants or pyrotechnics. Because of length of the projectile depends on the ductility of their sensitivity, primary explosives are used in Vol. 13 Explosives 635

Table 1. Properties of primary explosives

Property Lead azide, Silver azide DDNP Lead Tetrazene pure styphnate

Crystal density, g/cm3 4.8 5.1 1.63 3.0 1.7 Detonation velocity, km/s 6.1* 6.8* 6.9 5.2 at density 4.8 5.1 1.6 2.9 Impact sensitivity, Nm 2.5 – 4 2 – 4 1.5 2.5 – 5 1 Friction sensitivity, N 0.1 – 1 20 8 10 Lead block test, cm3/10 g 110 115 325 130 130 Explosion temperature,** C 345 290 195 265 – 280 160 * Theoretical. ** After 5 s. quantities limited to a few (milli)grams, and are sitivity of the 92 % lead azide to impact and manufactured under special precautions to avoid friction compared to purer lead azides facil- any shock or spark. To be used in industry, itates detonator loading. Lead azide has good primary explosives must have limited sensitivity stability to heat and storage. Contact with and adequate stability to heat, hydrolysis, and copper must be avoided because copper azide storage. Mercury fulminate, azides, and diazo- is extremely sensitive; aluminum is preferred. dinitrophenol are among the few products that Silver azide is used at high temperature or in meet these requirements and that can detonate a miniaturized pyrotechnic devices. It is pre- secondary explosive. Others, e.g., lead styphnate pared from aqueous silver nitrate and sodium or tetrazene, initiate burning or act as sensitizers. azide. Properties of primary explosives are given in Table 1. Diazodinitrophenol [28655-69-8], DDNP, C6H2N4O5, Mr 210.06, is obtained by diazotizing Mercury Fulminate [628-86-4], Hg(ONC)2, picramic acid and purified by recrystallization Mr 284.65, was first prepared in the 1600s and from acetone. It is sparingly soluble in water, was used by NOBEL in 1867 to detonate dyna- nonhygroscopic, and sensitive to impact, but not mites. It is prepared by the reaction of mercury as sensitive to friction or electrostatic energy. It is with nitric acid and 95 % ethanol, in small quan- less stable to heat than lead azide. It is most often tities because the reaction is difficult to control. used in the United States. Mercury fulminate is a gray toxic powder, which lacks the stability for storage. It reacts with metals in a moist atmosphere; in most industrial countries its use has been abandoned.

Lead Azide [13424-46-9], Pb(N3)2, Mr 291.26, discovered by C (1891) [13], was developed URTIUS [ ], lead trinitror- after World War I and is now an important Lead Styphnate 15245-44-0 esorcinate, C HN O Pb, 450.27, is produced primary explosive. It is produced continuously 6 3 8 Mr continuously by the aqueous reaction of the by the reaction of lead nitrate or acetate with magnesium salt with lead acetate, sometimes in sodium azide in aqueous solution under basic the presence of agents that promote the formation conditions to avoid formation of hydrazoic of the correct crystalline form. Especially sensi- acid, which explodes readily. The crystal size tive to electrostatic discharge, it is most frequent- must be carefully controlled, large crystals ly used to sensitize lead azide and in primer being dangerous, by controlling the stirring compositions to initiate burning. andbyusingwettingagents. Demineralized water must be used. With thickeners such as dextrin, sodium carboxymethylcellulose, or poly(vinyl alcohol), purities from 92 % to 99 % are possible, the former containing 3 % dextrin and 4 – 5 % Pb(OH)2.Thelowersen- 636 Explosives Vol. 13

Tetrazene [31330-63-9], C2H8N10O, Mr acetic acid; the reactive species may be þ 188.07, is obtained by the reaction of sodium CH3COONO2H . Mixtures of nitric acid and nitrite with a soluble salt of aminoguanidine in acetic anhydride containing between 30 and acetic acid at 30 – 40 C. It decomposes in 80 wt % HNO3 can detonate [51]. A high con- boiling water. Its greatest value is for the sensiti- centration of acetic anhydride avoids this danger. zation of priming compositions. More recent nitration methods use N2O5 as a solution in pure nitric acid (‘‘nitric oleum’’) or in chlorinated solvents (e.g., CH2Cl2). Three pro- cesses for the production of nitric oleum are in operation or in development [89]:

1. Oxidative electrolysis of a N2O4 – HNO3 A current trend in research on new primary mixture explosives is to replace compounds containing 2. Ozonation of N2O4 lead for environmental problem reasons. 3. Distillation of an oleum (H2SO4 þ SO3)– NH4NO3 mixture [90]

Nitric oleum allows yields to be improved and 5. Secondary Explosives permits some syntheses to be performed that are not possible by other routes; the organic N2O5 5.1. Production solutions allow nitration to be performed under very mild and selective conditions [16, 91]. Common high explosives are usually made by These nitrating agents must be used at their site liquid-phase nitration. The overall mechanism is of production. believed to be ionic, with þ generally the NO2 reactive species. In some cases, N2O4 may be Nitration. Reaction is exothermic. Dilution added to a double bond or to an epoxy group. It is of the nitric and mixed acids with water liberates also possible to nitrate gas-phase hydrocarbons. heat [52]. Normally, nitration is rapid. However, The most important nitrating agent is nitric acid 70 – 85 wt % nitric acid is also an oxidant, and (! Nitric Acid, Nitrous Acid, and Nitrogen for this reason the reaction is best conducted Oxides). continuously to limit the contact time of the Numerous end products of nitration are solu- product with the reactive medium. If the medium ble in concentrated HNO3, and may be recovered is free of solid particles, a tubular reactor can be by dilution. However, dilution below ca. 55 wt % used; otherwise, reactors in cascade with effi- acid is not economic. cient stirring are employed. These reactors are To increase the þ content (3 wt % in pure NO2 made of highly polished stainless steel. Reactors HNO3), lower the solubility of end products, and stirrers must be carefully designed to avoid reduce oxidative side reactions, and facilitate the dead zones and friction with crusts of explosives. treatment of spent acids, mixtures of sulfuric and Reactors are often provided with a valve that nitric acids (mixed acid) are used. The water opens quickly to discharge reactants into a dilu- content of a mixed acid may be reduced by tion vessel in an emergency. adding oleum. In 50 : 50 wt % mixed acid, the nitric acid is ca. 15 % dissociated. Product Isolation. If a precipitate is not However, sulfuric acid is difficult to remove highly sensitive to friction, it may be centrifuged. from products by washing. Furthermore, some For safe continuous filtration, the product must substances (e.g., nitramines, nitriles, etc.) are be stable in its mother liquor, and the filter design decomposed. Orthophosphoric acid or polypho- must avoid introduction of the explosive between sphoric acid may be used instead of sulfuric acid; moving and fixed parts. The precipitate is washed however, these phosphoric acids are more expen- in two stages. The first uses only a small amount sive and more difficult to recover. of water, which is recovered and mixed with Mild nitration or nitrolysis can be conducted spent acid. The acid is recovered from this in mixtures of nitric acid and acetic anhydride or mixture. Vol. 13 Explosives 637

Purification. Treatment with boiling water avoided. Minimum distances between plant and is sometimes sufficient to hydrolyze impurities nearby structures are regulated. and wash out nitric acid. Crystallization elimi- The transmission of detonation by pipes or nates sulfuric acid and produces the desired grain feeding devices must also be prevented by ap- size. The solvent can be diluted with water or propriate arrangements. The danger of detona- removed by steam distillation. Very fine crystals tion by an accidental fire can be mitigated by are obtained by dilution with high-speed stirring limiting vessel size. Detonations by shock and or by grinding in water or an inert liquid. A fluid friction in pipes, pumps, or valves are prevented energy mill may also be used. Size separation can by suitable measures. be effected by sieving under flowing water or in a The following principles apply: partition of classifier. Drying is usually done as late as pos- risks (e.g., specific buildings for specific opera- sible in the process. tions); limitation of risks (limited number of persons present and limited quantities of explo- Recovery of Spent Acids. Acid recovery in sives); and installation of two or three indepen- an explosive plant is of great importance in dent safety devices. Some of these measures are controlling production costs. These acids include taken by the manufacturers under the supervision 55 wt % HNO3, 63 – 68 wt % H2SO4 from nitric of professional organizations following govern- acid concentration, and spent H2SO4 containing ment regulations. some nitric acid and nitration products. To concentrate nitric acid, water is removed by countercurrent extraction with 92 – 95 % 5.2. Specific Secondary Explosives H2SO4. At the top, 98 – 99 % HNO3 is pro- duced. At the bottom, 63 – 68 % H2SO4 is ob- Properties of secondary explosives are given in tained, which can be concentrated to 93 % by Tables 2 and 3. stripping with combustion gases, or to 96 – 98 % by vacuum distillation. Nitric acid can also be concentrated by distillation over mag- 5.2.1. Nitrate Esters nesium nitrate. Sulfuric acid is freed of nitric acid and nitro Nitrate esters RONO2 are prepared from alcohols compounds by heating or steam injection. and nitric acid, which may be mixed with sulfuric or acetic acid. The reaction is reversible:

Pollution Problems. Gaseous pollution þ þ NO þROH RONO þH may occur during nitrations, with evolution of 2 2 red nitrous fumes. These can be absorbed in In an anhydrous medium the equilibrium columns by recycling water or dilute nitric acid shifts to the right; with dilution, hydrolysis oc- to provide 50 – 55 wt % acid. curs. In 60–80 % HNO3, the unreacted alcohol Liquid and solid pollution is created by wash- may be oxidized. Furthermore, a catalytic effect ing. Usually acids are transferred to decanting of the nitrous acids produced causes rapid de- and settling basins, where product and other composition of the reaction medium. This de- solid particles settle and liquids are neutralized. composition either does not occur or occurs very Some liquid wastes require special treatment; for slowly with an acid concentration below 55 %. example, the red liquors from TNT are best Nitrate esters are usually less stable if traces of destroyed by combustion. acid are present. Traces of sulfuric acid are difficult to remove from solid nitrate esters; Safety [9, 11]. Accidents caused by detona- therefore, mixed acid should not be used for their tion are usually very severe. In addition to the preparation. Acetic – nitric acid mixtures are normal precautions required in acid handling, the used with sensitive or oxidizable alcohols. production and use of explosives obviously in- volves special risks. Loss of life and destruction Pentaerythritol Tetranitrate [78-11-5], PETN, of property by an accidental explosion must be C5H8O12N4, Mr 316.15, is scarcely soluble in 82 % prevented at all costs, and the detonation of HNO3 (0.7 wt %). The nitration of pentaerythritol explosives stored near populated areas must be is practically complete in a few seconds and is 638 Explosives Vol. 13 ) Table 3. Impact sensitivity of secondary explosives*

** 9300 Explosive Value

Insensitive TATB > 2.5 TNT 1 Moderately sensitive 2.03 – 2.04 2.04 1 DINGU 0.8 < HNS 0.6 NTO 0.8

d Sorguyl 0.15 – 0.2 CL20 0.15 – 0.2 1.83 4 – 8 Sensitive HMX, RDX 0.3 PETN 0.15 – 0.2*** d NG 0.1 1.91 * Drop-weight impact test [7]. ** Based on TNT ¼ 1. ***

e Values are dependent on particle size 6 – 8 1.98 decomp. decomp.

C conducted continuously. Pentaerythritol and HNO 3 7 b (ca. 1 : 5.5) are fed into a well-stirred, jacketed 10

reactor, with overflow in cascade into a second reactor of the same design. The temperature is

C at 100 maintained below 30 C. PETN precipitates and may be isolated in one of two ways: 1.82 1.907 8850 9100 8450 8520 ca. 3900 9300 0.05 4 480 480 204 283 260 255 92 190 1. In a third reactor the reaction mixture is diluted with water to 55 wt % acid ( C at 110 cPETN 0.1 wt %) and filtered. The PETN is washed

452 with water 0.4 520 explodes > 2. The reaction mixture is filtered immediately C at 175

7 and then the 82 wt % spent nitric acid is

10 concentrated, a cheaper process but less safe 0.4 6 – 8 decomp. decomp. Washed PETN is stable. It can be recrystal- C at 100 C lized by dilution of a hot acetone solution with a water, which removes traces of acid and some 1.654 1.74 1.94 1.47 at 81 14 1.3 organic impurities, and crystals of desirable size and flow properties for continuous feed purposes C at 100

a are obtained. Pentaerythritol tetranitrate is fairly stable above 100 C and in alkaline medium. It is 1.591 a powerful high explosive, with a small critical diameter, easy to initiate, and sensitive to Cat40 impact and friction. But that sensitivity depends on the crystal size: PETN is more insensitive if at 100 1.77 520 520 300 141.3 13.5 80.8 318 0.0011 1 ultrafine or in form of a very big monocrystal.

3 Nanometric PETN was recently obtained by a 3 f sol – gel process. It is used in detonators, com- mercial detonating cord, boosters (with wax), C

sheet explosives (with an elastomeric binder),

Properties of secondary explosives and plastic explosives. In a mixture with TNT, it C x -rays 1.99 is employed in some warheads and in industrial form. form. , max. density, m/s after 5 s, Liquid. b a Calculated in some cases. by explosives. Crystal density, g/cm Table 2. Property PETN NGCritical diameter, mm TNT 0.4 a b HNSc d e TATB RDX HMX DINGU NTO ADN Sorguyl CL20 ( e mp Lead block test, 10 g, cm Detonation velocity at 8340 7700 6960 7120 7970 Explosion temperature 225 220 – 240 470 305 315 decomp. 301 330 Vapor pressure, Pa Vol. 13 Explosives 639

Nitroglycerin [55-63-0], NG, C3H5O9N3, Mr and are usually obtained by nitration. The Ingold 227.09, unlike PETN, is a liquid at room temper- mechanism involves nitronium ion, þ; elec- NO2 ature, totally miscible with HNO3 of higher than trophilic attack occurs with formation of a s- 70 % concentration, sparingly soluble (3 wt %) complex intermediate [22]. in 50 % HNO3, and sensitive to hydrolysis (any The introduction of a second and third nitro contact with hydrolytic medium must be very group requires increasingly severe conditions, in- short) [53]. It is prepared by continuous two- cluding more anhydrous mixed acids and elevated phase nitration of glycerol in anhydrous mixed temperatures (above 100 C for trinitration). acid. The mass ratio of pure anhydrous glycerol Some of these aromatic nitro compounds are (H2O < 0.5 %) and 50 : 50 mixed acid is 1 : 5. not used or are abandoned as explosives: among The product is washed with aqueous sodium them: carbonate or bicarbonate. In the Schmid – Meissner and Biazzi process- 1,3,5-Trinitrobenzene [99-35-4], TNB, ben- es, the reactor is a vessel with overflow and good zite C6H3O6N3, Mr ¼ 213.11 (I, R ¼ H), attrac- stirring and cooling. The reactants are fed con- tive as high explosive, cannot be obtained by tinuously, while the temperature is kept at 10 – direct nitration of benzene, but only by indirect 20 C. The emulsion produced flows into a sep- syntheses giving an expensive product used only arator, which in the Schmid process does not for preparations of fine chemicals. have moving parts. In the Biazzi process, the separator is conical with peripheral feeding, 2,4,6-Trinitrophenol [88-89-1]C6H3O7N3, breaking the emulsion by rotation. The product Mr ¼ 229.11 (I, R ¼ OH) TNP, picric acid, is washed with alkaline water in columns melinite, was extensively used in France during (Schmid) or in mixer – settlers (Biazzi). World War I because of lack of toluene, but was In the Gyttorp process, developed in the later replaced by trinitrotoluene (tolite), cheaper 1950s, the feeding of acid and alcohol can be and nonacidic. In some ammunitions, ammoni- interrupted simultaneously. The key feature is um picrate is still used. the use of an injector with an axial flow of acid; the alcohol is sucked through the neck with 2,4,6-Trinitrophenyl-N-methylnitramine excellent mixing. For good suction and heat [479-45-8] N-methyl-N,2,4,6-tetranitroaniline, absorption, a volume ratio of acid: alcohol of ca. Tetryl, C7H5O8N5, Mr ¼ 287 (I, R¼N(CH3)NO2) 8 is required; it is maintained by recycling part of has been used since 1905, notably for the pro- the spent acid. The glycerol is heated to 48 Cto duction of boosters, after lubrication by graphite reduce viscosity. The emulsion that is formed is or calcium stearate. But it is now practically cooled to 15 C, and centrifuged continuously to abandoned because some allergic incidents of separate the nitroglycerin from spent acid. The dermatosis, and replaced mostly by RDX – wax product is emulsified with alkaline wash water by mixtures. passage through an injector; it is separated and Three nitro-aromatic products with a picryl washed again until neutral. The final emulsion can group remain for use as high explosives: TNT, be safely transmitted through pipes. The quantity HNS, and TATB. of nitroglycerin present at any given time can be kept low, and safety is further increased by pro- 2,4,6-Trinitrotoluene [118-96-7], TNT, to- tective walls and the use of remote control. lite, C7H5O6N3, Mr 227.13 (1,R¼ CH3), is Other liquid nitrates are produced by these produced by successive nitration of toluene, processes; the Gyttorp process requires a liquid producing mono-, di-, and finally trinitroto- alcohol reactant. The spent acid may be purified luenes. The mononitration products are 60 % by heating. Nitroglycerin is used in propellants, ortho,35%para, and 3 – 5 % meta derivative. gunpowder, and dynamites.

5.2.2. Aromatic Nitro Compounds

The most common nitro-aromatic explosives contain the picryl (2,4,6-trinitrophenyl) group 640 Explosives Vol. 13

The o- and p-nitro compounds give 2,4- and nomical treatment of the red spent water 2,6-dinitrotoluenes and then 2,4,6-trinitrotolu- from selliting is concentration followed by ene (meta-directing effect of NO2). However, combustion. m-nitrotoluene does not give the 2,4,6-trinitro Trinitrotoluene is used alone or mixed with derivative; other products are formed that reduce PETN, RDX, or ammonium nitrate. It is also used the stability or lower the melting point of the in some industrial explosives. TNT. These impurities can be removed by the so- called selliting process or by fractional distilla- Hexanitrostilbene [20062-22-0], HNS, tion of the mononitration products. The m- and p- C14H6O12N6, Mr 450.24, is formed by oxidation nitrotoluenes are used as chemical intermediates, of TNT in methanol – tetrahydrofuran solution and the o-nitrotoluene is further nitrated to TNT. with aqueous NaOCl [58]: This method gives a product that is more easily purified. For reasons of safety, quality, and cost, mod- ern high-capacity plants use a continuous pro- cess. The solubility of organic products in mixed acids can be quite low, 0.5 – 15 wt %, depending on temperature and sulfuric acid concentration. Yields of 40 – 50 % are obtained in a contin- Nitration is believed to occur in the acid phase. uous tubular reactor [59, 60]. Hexanitrostilbene Consequently, the rate of interphase transfer and can be crystallized from HNO3 or acetone. the intensity of stirring are important. Hexanitrostilbene has the following unusual The plant employs a series of 8 – 16 mixer – properties: the presence of 1 % HNS in molten settlers. The organic phase is transferred from the TNT prevents the formation of cracks and crazes preceding settler together with the acid phase during solidification. With its low critical diam- from a following or preceding settler (counter- eter (0.4 mm) it can be used as the core in silver current or parallel nitrators) into a mixer main- or other metallic explosive cords. It remains tained at a constant temperature (50 C for stable and explosive over a very wide tempera- mono-, 80 C for di-, and 100 C for trinitration). ture range (200 to 250 C) and is thus usable in Acids may be added to adjust the composition. space [61]. From the last settler, molten TNT overflows into other mixer – settlers that are used for washing 1,3,5-Triamino-2,4,6-trinitrobenzene and selliting. [3058-38-6], TATB, C6H6O6N6, Mr 258.15, is The spent sulfuric acid can be concentrated to obtained by the following sequence: ca. 96 % but not to oleum. Using oleum in the process leads to a higher yield, a shorter starting time, and a more rapid reaction; consequently, fewer mixer – settlers are required for a given output, but a use or customer must be found for the spent acid. The proximity of nitro groups favors the Selliting is a process of washing with aque- displacement of chlorine by ammonia. The reac- ous Na2SO3. A preferential reaction with the tion is conducted under pressure at 150 Cin unsymmetrical TNT isomers gives deep-red wa- toluene containing a little water. The product is ter-soluble products. Selliting is applied to crude washed with water to remove NH4Cl. It has low molten TNT above 80 C, but with some losses. solubility and is difficult to recrystallize [62, 63]. A continuous process may also be employed at Although discovered in 1887, it first attracted 50 C, with TNT suspension produced by cool- attention after World War II. Since the 1950s ing an aqueous emulsion with vigorous stirring interest has increased because of its thermal [54]. The resulting spherules contain pure 2,4,6- stability and outstanding insensitivity. Mixed TNT at their center, and a mixture of isomers in with HMX and a fluorinated binder, it is used the outer layer. The use of MgSO3, rather than as a booster. It is, however, expensive (ca. 65 $/ Na2SO3, has been proposed [55]. The most eco- kg in the mid-1980s in the USA) because of the Vol. 13 Explosives 641 high cost and low availability of trichloroben- along with water. The process must be continu- zene. Therefore, alternative synthetic routes have ous with careful control of temperature and flow been developed. An extensive review of TATB is conditions. The plant consists of three groups of given in [9]. stainless steel cascade-type reactors with effi- cient stirring and cooling devices (jacket or coil). Nitric acid and hexamine are fed into the first 5.2.3. N-Nitro Derivatives group at a temperature of 20 – 50 C. The ho- mogeneous mixture overflows from the last re- N-Nitro derivatives include primary nitramines actor into the first one of the second group (the 0 RNHNO2, secondary nitramines RR NNO2, decomposers); this reactor is equipped with a nitramides, nitroureas, nitrourethanes, and nitro- large pipe for the escape of gases and a water guanidines. There are no general synthetic meth- feeder. The temperature is maintained between ods. Sometimes it is possible to nitrate the 75 and 82 C, and water is continuously added to precursor with HNO3 alone as with tetryl. Often maintain a HNO3 concentration of 55 wt %. The an N-acetyl, N-tert-butyl, or N-nitroso derivative gases evolved are condensed in towers, produc- is used as starting material. In some cases, nitric ing 50 – 55 wt % HNO3, which is reconcen- oleum is effective. The nitration of hexamethy- trated. This first decomposer is the key to the lenetetramine (hexamine) to RDX and HMX is operation. Foam must be avoided as well as thick more complicated. crusts on which the stirrer could scrape, causing an explosion. In the third group of reactors, the 1,3,5-Trinitro-1,3,5-hexahydrotriazine suspended product is cooled and then continu- [121-82-4], C3H6O6N6, Mr 222.12, cyclotri- ously filtered and washed. The resulting RDX methylenetrinitramine, Hexogen, RDX. contains HMX (1 % max.) and some nitric acid, which can be removed by heating with water at 135 C for 3 h in an autoclave. The yield based on hexamine is 78 – 80 %. The RDX can be recrystallized or used direc- tly, after desensitizing by wax or 10 % TNT to permit drying and transportation. Recrystalliza- tion from cyclohexanone or methyl ethyl ketone Both RDX and HMX are stable in nitric acid removes traces of acidity (required, for example, over a wide temperature and concentration range, for use with aluminum powder) and produces but are destroyed by aqueous sulfuric acid and are crystals of the desired size. attacked by alkaline substances. Sulfuric acid A process without acetic anhydride was also should not be present during the synthesis. developed in Germany in 1940 (KH process). A 1,3,5-Trinitro-1,3,5-hexahydrotriazine was modification is the addition of NH4NO3 to react first described by the German chemist and phar- with all CH2 groups of hexamine (K process). macist G. F. HENNING [64]. It is manufactured by The KA process was developed during World nitrolysis of hexamine with nitric acid alone or War II in Germany, and the Bachman process with acetic anhydride. was developed and is used in the United States. The main process, called the Woolwich pro- Both processes use acetic anhydride, and the cess, which does not use acetic anhydride, was reactions are very complex. developed in the United Kingdom and is used To a solution of hexamine (1 part) in glacial there and in France. The raw materials are hex- acetic acid (1.65 parts) are added a solution of amine and 98 – 99 % HNO3 free of sulfuric acid. NH4NO3 (1.5 parts) in concentrated HNO3 (2 The reaction is complex and not completely parts) and acetic anhydride (5.2 parts) at ca. 65 – understood. 72 C. The mixture is maintained at that temper- Hexamine dinitrate is probably formed first, ature for at least 1 h, diluted with water, and followed by intermediates that are oxidized or heated to hydrolyze impurities. The yield is ca. decomposed, exothermically and often violently, 80 – 85 %; nitrous fumes are not evolved. to produce RDX, which precipitates. Large The product contains ca. 8 – 15 % HMX, amounts of nitrous gases and CO2 are evolved depending on the reaction conditions. An 642 Explosives Vol. 13 adequate source of acetic anhydride must be ever, since demand for HMX is now very low, nearby, where acetic wastes can be dealt with. production by this route has ceased. This process is easier to carry out than the process The price of HMX is usually 3 – 5 times that employing nitric acid alone, but its environmen- of RDX. It is used when high performance is tal problems are more difficult to solve. The same required (e.g., shaped charges). Both RDX and plant can be adapted to HMX production. HMX are also used in propellants. Both RDX and TNT are the basic components of almost all modern high explosives. They are Other High Explosives. Numerous nitra- mixed together, alone or with wax, or formulated mine derivatives have been studied. For with plastic binders. For a powerful and heat- example: stable explosive, RDX is preferred. Dinitroglycoluril [55510-04-8] (DINGU or DNGU ; ,R¼ H) has a high density (1.99 g/ 1,3,5,7-Tetranitro-1,3,5,7-tetraazacyclooc- 4 cm3, X-ray) [101] and explosive properties close tane [2691-41-0], C4H8O8N8, Mr 296.16 (2,R to those of TATB [71, 72], but at a much lower ¼ NO2), octahydrotetranitrotetrazocine, cyclote- tramethylenetetranitramine, octogen, HMX, was price. It can replace part of the RDX in mixtures discovered shortly before World War II as a with TNT and can be introduced as a component byproduct of RDX synthesis by a Bachman-type in gunpowder. Some comparative thermodyna- process. It exists in four crystalline forms [4, 67, mic properties are studied [73]. 68]. The b form has the highest density (r ¼ 1.907 g/cm3) and a shock sensitivity similar to that of RDX. Large crystals of the a form are shock sensitive, but microcrystals are not.

It is prepared by continuous nitration of gly- coluril with 98 wt % HNO3 at 30 – 60 Cin cascade-type reactors.

Tetranitroglycoluril (sorguyl ; 4,R¼ NO2) prepared by nitration of DINGU with a mixture 3 HNO3 –N2O5, has a high density (2.01 g/cm ), HMX is now obtained directly by a modified and detonation velocity (9300 m/s). Only one Bachman process. In this batch process, acetic crystalline form is known. It must be coated or plastic bonded because it is sensitive to hydroly- anhydride and a mixture of NH4NO3 and HNO3 are added simultaneously at 44 1 C to hex- sis [71, 73, 75]. amine dissolved in glacial acetic acid. After 15 min, the operation is repeated. The reaction Hexanitrazaisowurtzitane (HNIW, CL-20). mixture is aged at 45 – 60 C, diluted with hot One way to obtain explosives of high crystal water, and refluxed for up to several hours. The density is the synthesis of cage compounds such suspended HMX is filtered off and washed until as HNIW, which was discovered in 1986 by A. neutral. The HMX is obtained as small crystals of NIELSEN [99]. the a form, which are transformed into the b form by recrystallization from acetone or DMSO. HMX can also be obtained via dinitropenta- methylenetetramine (DPT, 3,R¼ NO2) [69]. In another process starting from hexamine, the dia- cetyl intermediates DAPT (3,R ¼ COCH3) [70] and DADN (2,R¼ COCH3) are isolated, and this is followed by nitration with nitric oleum. How- Vol. 13 Explosives 643

It is prepared by the reaction of benzylamine ously through a funnel to form a flowing stream with glyoxal, followed by debenzylation and that is wrapped in a thin plastic band. Thread is nitration. It exists in six crystalline forms [93, immediately woven on the plastic-enclosed ex- 94]; the e form has a density of 2.04 g/cm3. plosive, and this is again encased with plastic by Production has begun in pilot plants [89]. It can drawing through a die, which also helps adjust be used as a high explosive and in propellant the loading density. formulations. For metallic cords, the high explosive (PETN, RDX, HMX, or HNS) is introduced into a metal- Oxynitrotriazole [932-64-9], ONTA, NTO, lic tube (lead, copper, or silver), which is drawn 3-nitro-1,2,4-triazol-5-one, was first reported in through dies until the desired size and cross 1905, but its use as a low-vulnerability explosive section are obtained. was only discovered in 1979 [97, 74]. It has a high density (1.91 g/cm3), good detonation velocity, Loading Processes. In casting processes, the low sensitivity to impact and friction, and good explosive is employed as a solution or a liquid thermal stability (> 200 C) [98]. suspension; it is cast into the shell or in the mold, where it crystallizes on cooling (physical pro- cess) or solidifies by the cross-linking of a poly- mer (chemical process). In pressing processes, the explosive is introduced in granular form into a mold or shell and pressed with a piston at a pressure of 10 – 300 MPa; conditions depend on It is manufactured in two steps: reaction of the the munitions size, the binder, and the required semicarbazide hydrochloride with formic acid to mechanical properties. Special shapes are pre- give the triazolone, which is nitrated with nitric pared by laminating or calendering. acid. The NTO is recrystallized from water. NTO Flexibility is increased by the use of blends, is used in LOVA formulations, some of which which can enhance explosive performances were tested in a joint LOVA programme of the while preserving safety and reducing cost. Spe- USA, UK, Germany, and France. cial effects, such as delayed detonation, are possible with improved safety and high-temper- (ADN), þ Ammonium Dinitramide NH4 N ature stability. ð Þ, r 1.83 g/cm3, 92 C, is a carbon- NO2 2 mp free ammonium salt that was discovered and developed in the former Soviet Union in the 6.2. Desensitized Explosives 1960s and has in the mid-1990s been disclosed [100]. ADN is almost as hygroscopic as ammo- Because of their sensitivity and high melting nium nitrate and very insensitive. It is of interest points, RDX, PETN, and HMX must be desen- as a component of certain explosive mixtures and sitized before casting or pressing. This is as a clean propellant. achieved by coating the particles with wax, sometimes with addition of graphite as a lubri- cating and antistatic agent. The beeswax used in 6. High Explosive Mixtures the past has been replaced by paraffin or synthetic waxes, which give more reproducible results. Explosives are used for global or directed de- The wax content in the explosive mixture is struction (bombs, torpedoes, mines, reactive ar- usually 2 – 10 wt %. mors, and warheads) or for pyrotechnics. Among In the simplest process, the particles are coat- pure compounds, only TNT and trinitrophenol ed in hot water. The explosive (RDX, for exam- are sufficiently insensitive to be loaded in large ple) is vigorously stirred in water and heated quantities by casting. Small quantities of other slightly above the melting point of the wax, pure compounds are sometimes used for detona- which is introduced and dispersed on the parti- tors or cutting or transmitting cords. cles. The mixture is cooled by the rapid intro- For flexible wrapped cords (detonating cords), duction of cold water, without formation of crusts the pure explosive (e.g., PETN) flows continu- on the vessel walls. The suspension is filtered and 644 Explosives Vol. 13 dried. Coating agents melting above 100 C are cooling can be controlled by the addition of applied in a solvent (e.g., butyl acetate), which is 1 % HNS. removed by steam distillation. If the explosive is Explosive performance is restricted by the sensitive to hot water, the solvent is removed by condition that the mixture must be pourable; for filtration, possibly preceded by evaporation un- example, for a blend of RDX: TNT of 70: 30 der vacuum. These processes are also used to (wt %), D ¼ 8060 m/s at r ¼ 1.73. (Since rtheor prepare ternary mixtures of explosive aluminum 1.765, the porosity is ca. 2 %.) and wax. For blends with higher RDX or HMX content, Detonation velocities can be obtained close to a special apparatus such as a porous piston is those of the pure explosives; e.g., for a mixture of used. Because of the danger of detonation by fire, 94.5 % RDX, 5 % wax, and 0.5 % graphite, D ¼ mixtures of RDX with TNT are now forbidden on 8600 m/s at r ¼ 1.76 g/cm3 (D ¼ 8850 m/s at ships by some countries. r ¼ 1.82 g/cm3 for pure RDX). However, large loadings are difficult to carry out because of problems with homogeneity, brittleness, 6.4. Plastic-Bonded Explosives (PBX) porosity, and cost. The process is very useful for automatic filling of press-loaded small Two different procedures are followed which munitions. improve the performance of new munitions.

Desensitized Explosives. Some new war- 6.3. TNT Mixtures heads require improved mechanical properties and stability at high temperature. Waxes are Molten TNT (mp 80 C) is compatible with replaced by thermoplastics or by other plasti- many explosives and other products, providing cized polymers (nitrocellulose). a castable melt above 80 C. Among the products The manufacture of these plastic-bonded ex- most frequently added are ammonium nitrate, to plosives resembles the use of waxes dissolved in obtain very cheap munition loadings (amatols), a solvent immiscible with water. The molding and nitramines (RDX or HMX) or other high powder is pressed, often in a heated and evacu- explosives (PETN, NTO), to improve perfor- ated mold; for large charges, machining is nec- mance. Mixtures containing 50 – 75 wt % RDX essary to obtain homogeneous charges of com- are used in bombs and warheads such as shaped plex shapes with good mechanical properties at charges. Some castable blends contain aluminum high temperature. powder (tritonals, ammonals, Torpex, and Examples include RDX or HMX boosters HBX 1 and 3). bonded with polyamide and mixtures of HMX Wet and dry processes are employed. The and TATB containing 10 wt % fluorinated poly- former, the same as that used for desensitizing mer [96]. Use is limited by the high cost of the with low-melting wax, has cost and safety ad- pressing machines and the length of the proces- vantages. Almost the entire process is carried out sing cycle, especially for large charges. under water. In France, RDX coated with 10 wt % TNT is produced in this manner, be- Castable Explosives [76, 77]. For larger cause its transportation as a dry product is al- charges, mixtures are used of an explosive with lowed. However, air bubbles on the RDX crystals a liquid binder, which is then cross-linked (com- can create difficulties in loading. posite explosives). A similar process is used for In the dry process, the components are added composite propellants. Composite explosives are dry to molten TNT with stirring, and the mixture being developed for uses requiring high accuracy is cast in shells. Wet RDX can be added to TNT at and low vulnerability (LOVA explosives). ca. 95 – 100 C; the water is removed by decan- The liquid binder is introduced first into a tation and evaporation. mixer equipped with S-blades. A mixture of a Blends of TNT are used in the large-scale diisocyanate and a diol (hydroxy-terminated production of munitions. Shaped charges can be polyether or polybutadiene) is usually employed obtained by controlled sedimentation of the mol- in a precise ratio, with a precise quantity of a ten mixture. Crack formation in TNT during cross-linking agent such as a triol. The dry solid Vol. 13 Explosives 645 explosive (RDX, HMX, or PETN) is then added mixing of explosives from non-explosive com- and mixed under vacuum with additives (e.g., ponents and the commercialization of electronic surfactants) and a catalyst providing a pot life, i. initiation systems. The search continues for less e., the mixture remains pourable, of a few hours. expensive products and safer techniques for pro- During this time the mixture is cast, sometimes duction and field use in mines, quarries, and road, under pressure or by injection, in vibrating and tunnel, and dam construction. At the same time, evacuated molds or shells. The molds are cured in the introduction of new products is restrained by an oven for a few days. Two different composi- the cost of existing investments and by safety, tions may be cast, one over the other (bicomposi- security, and environmental regulations. tions), to produce special detonation waves. The main advantage of these formulations is their low sensitivity, especially against bullets, 7.1. Dynamites impact, and friction, and the difficulty of the transition from combustion to detonation. The Gelatine dynamites are powerful explosives mechanical properties can be excellent, and ther- whose main ingredients are nitroglycerin and/or mal stability is fair. nitroglycol, ammonium nitrate, and nitrocellu- Among the drawbacks are the slow curing and lose. They were invented opportunely to replace high cost when a multimodal particle-size distri- black powder in the construction of railroad and bution is used to increase the explosive content. tunnels and gave great impetus to the use of The detonation velocity is diminished by the inert explosives. Although diminished in importance character of the binder; it can be estimated by the since the 1950s and progressively replaced Urizar formula [7, pp. 8 – 10], [78]. Energetic by new types of explosive, dynamites are still binders improve the detonation velocity, but widely used because of their excellent qualities increase sensitivity. A review of energetic bin- and high performance. In 2007 dynamites ac- ders is given in [15, 80]. The use of thermoplastic counted for 11 % of total European explosives elastomers as binders is of interest for environ- consumption. mental reasons since they facilitate the disman- A detonation velocity range from 4300 to tling of ammunition. 7500 m/s provides high brisance. Sensitivity to initiation by cap or detonating cord is very good, as is the flashover coefficient. Density (ca. 1.4 g/ 7. Industrial Explosives cm3), water resistance, and detonation pressure are high. For more than 350 years explosives have been The composition of dynamites has changed employed to mine ores and minerals, as well as only slightly since their origin. Nitroglycerin, for quarrying, construction, dam building, gelatinized by nitrocellulose, has been totally or tunneling, seismic exploration, metal forming partially replaced by nitroglycol to reduce costs and cladding, and demolition. The annual con- and permit lower operating temperatures. How- sumption of commercial explosives in Europe ever, nitroglycol is more toxic than nitroglycerin, (EU 27 þ Norway and Switzerland) in 2008 and its use is limited in some countries. Oxidizers amounted to 550 000 t (which were initiated by such as ammonium nitrate reduce the cost of low- 65 106 detonators). Each of the largest West- energy formulas. Combustible components ern European countries used between 40 000 t (wood meal, peat, silicon, and aluminum) and and 60 000 t. World annual consumption of other additives (sodium nitrate, ammonium chlo- industrial explosives is at least 5 106 t, 75 % ride, and sodium chloride), provide formulations of which is ammonium nitrate–fuel oil (ANFO). with specialized properties. During the first 250 years of this period, only The consistency of such mixtures varies ac- black powders were known and used, but funda- cording to the nitroglycerin – nitroglycol con- mental changes occurred in the 1860s (invention tent. Gelatin dynamites containing 20 – 40 wt % of dynamite and blasting caps by NOBEL), 1950s of nitroglycerin – nitroglycol form a plastic (ANFO), 1980s (emulsion explosives) and 1990s paste that may be made into paper-wrapped with the introduction of mobile emulsion (Rollex process, small calibers up to 50 mm) or manufacturing units (MEMUs) for the on-site plastic film (large caliber, over 50 mm) 646 Explosives Vol. 13 cartridges after cutting or extrusion. Dynamites 7.2. Ammonium Nitrate Explosives containing 10 – 20 wt % nitroglycerin – nitro- (Ammonites) glycol are powdery, and tampers are required to make cartridges. They have been largely re- Ammonium nitrate (AN) explosives were devel- placed by the new explosives, except for use in oped in European countries to replace explosives coal mines, where the potential presence of dan- made with chlorates. They appeared later in the gerous dust and gas means that only very safe United States (Nitramon, DuPont, in 1935). explosives with the lowest possible detonation AN explosives are made with ammonium temperature should be used. Permissible explo- nitrate (ca. 80 wt %) sensitized with a nitro com- sives for these applications usually contain a pound (TNT, PETN, or their mixtures, called large amount of ammonium nitrate and sodium Pentolite). Formulas can include aluminum pow- chloride as cooling salts, the endothermic melt- der and other additives. These products are char- ing of which absorbs much of the energy released acterized by their good production safety and low by the detonation. Historically, there are no production cost. They show good sensitivity harmonized standards for permitted explosives when initiated by detonators and detonating in Europe. Degrees of safety in coal mines are cords. However, they are sensitive to humidity. defined by national regulations. In Germany Properties of a typical Ammonite are as follows: there are three safety classes. Class three is the safest group with reduced detonation tempera- ture and energy and which is safe against coal Composition, wt % dust and methane mixtures. In France the classes Ammonium nitrate 81.5 High explosive 16 are rocher, couche, and couche amelior ee . The Aluminum 0 first refers to less safe explosives, permitted for Mass energy, kJ/g 3.51 underground use only. In Great Britain, an Detonation velocity, m/s 4800 explosive is approved by the Minister of Power Flashover coefficient, cm 2 Detonating pressure 6.34 and placed on the Permitted List after it has Density, g/cm3 1.10 passed the official gallery tests prescribed for the particular class of explosives to which it belongs. These tests are carried out at the Safety Ammonium nitrate explosives made in the in Mines Research Establishment Testing Station United States may contain dinitrotoluene (DNT) at Buxton. The safety classes are P1 to P5 with P5 but no nitro high explosive. They are produced by or P4/P5 being the safest class which is used in blending and as a result are not cap sensitive. The coal mines to reduce the hazard of firedamp or U.S. Government, followed by other govern- coal-dust ignitions which might occur in gassy or ments, has established a category with relaxed dusty mines. rules for the transport and storage of these ex- Dynamites are marketed in cylindrical paper, plosives. This category was first called NCN cardboard, or plastic cartridges. The character- (nitrocarbonitrate) and is now known as blasting istics of a standard composition are given in agents. They have been progressively replaced Table 4. by water gels and emulsion explosives.

Table 4. Properties of dynamites

Property F16 F19 GDC 16

Nitroglycerin/nitroglycol, wt % 32 40 12 Classification gelatin gelatin powder Application general and underground general and underground permissible Mass energy, kJ/g 3.97 4.15 1.78 Detonation velocity, m/s 6000 6500 2200 Flashover coefficient*, cm 8 10 10 Cartridging density, g/cm3 1.45 1.45 1.10 Detonation pressure** 13.05 15.32 13.31 * Maximum distance at which a cartridge of diameter 30 mm and weight 50 g has a 50 % probability of initiating another cartridge. ** 1 2 Calculated with the formula /4 AD . Vol. 13 Explosives 647

7.3. Ammonium Nitrate/Fuel Oil Table 6. Properties of water gel and slurry explosives for general applications Explosives (ANFO/ANC Explosives) Property Hydrolite AP, Gelsurite 3000, Ammonium nitrate/fuel oil (ANFO/ANC) explo- in bulk in cartridges sives have been developed since 1955. They are Composition, wt % manufactured from porous prills of ammonium Nitrates 46 61.6 nitrate (ca. 94 wt %) soaked in mineral oil, usu- Water 15 13 ally domestic fuel oil (ca. 6 wt %) or native oils Aluminum 0 15 High explosive 27 0 like rapeseed oil methyl ester. In some cases, Mass energy, kJ/g 2.70 3.87 aluminum powder is added to increase the ex- Detonation velocity, m/s 5100 4000 plosive strength. ANFO accounted for 41 % of Flashover coefficient, cm 0 5 total European explosives consumption in 2007. Detonating pressure 9.75 4.80 Density, g/cm3 1.50 1.20 Ammonium nitrate/fuel oil explosives are usually delivered in packaged or bulk form. They can be made on-site in a mobile mixing unit, often mounted on a truck (ANFO truck). Relative Water gel explosives are supplied in car- to their lower inherent energy they are inexpen- tridges or in bulk form. The bulk explosives are sive and safe to handle, but lower in strength, poured or pumped into the blast holes. Cartridges performance, detonation velocity, and detonat- are formed with a continuous through-circulation ing pressure in comparison to dynamites or device (CHUBPACK) in cylindrical plastic car- emulsion explosives. In addition, they cannot be tridges closed by metal clips. used in the presence of water. Because of their Slurries and water gels are made of aqueous very low sensitivity, they require powerful prim- solutions of ammonium nitrate and sodium or er charges, powerful detonating cords, dynamite calcium nitrate gelled by the addition of guar relay cartridges, and boosters. The densities are gum or cross-linking agents. They are sensitized low. Properties are listed in Table 5. by nitro explosives, organic amine nitrates, or by aluminum powder. Combustible materials, such as aluminum, urea, sugar, or glycol, are mixed 7.4. Slurries and Water Gels with these solutions either continuously or discontinuously. A new class of industrial explosives, known as The presence of reactive aluminum, water, water explosives has been developed since 1956; and ammonium nitrate requires careful control to they contain no nitroglycerin and are based on a avoid chemical side reactions. The typical prop- solution of nitrates, thus containing considerable erties of water gel explosives and slurries are water (10 – 15 wt %). During the 1970s and listed in Table 6. 1980s, water explosives have taken over much of the market, at the expense of dynamites and AN powders, because of their lower production 7.5. Emulsion Explosives and raw material costs and improved safety during production and handling. Since the cost of sensitizer for slurry explosives is high, other formulas based on nitrate solutions containing cheaper raw materials have been in- Table 5. Properties of ANFO explosives for general applications vestigated. This led in 1962 to the development of ‘‘water-in-oil’’ and ‘‘oil-in-water’’ emulsion Property N 135 D7 fuel explosives, whose sensitivity is due to the pres- Composition, wt % ence of air bubbles; these are most efficiently Ammonium nitrate 91 94.3 introduced by means of hollow glass bubbles Fuel oil 4 5.7 (microspheres) or chemical gassing techniques. Aluminum 5 0.0 Mass energy, kJ/g 3.43 2.74 Emulsion explosives are produced, similar to Detonation velocity, m/s 3900 3700 water gels, by a continuous or a batch process. Detonating pressure 3.42 2.84 They can be supplied in cartridges of various 3 Density, g/cm 0.9 0.83 diameters (25 to 120 mm), lengths, and weights, 648 Explosives Vol. 13

Table 7. Properties of explosive emulsions used for general and underground applications

Property Iremite 1000 in Iremite 4000 in Iremite 2500s in Gemulsite 100 for cartridges cartridges cartridges pumping

Mass energy, kJ/g 3.34 3.92 3.51 3.49 Detonation velocity m/s 5300 5300 5500 5100 Flashover coefficient, cm > 5 > 55 Detonating pressure 8.43 8.43 9.08 7.80 Density, g/cm3 1.20 1.20 1.20 1.20 or in bulk form. Bulk emulsion explosives are These applications are governed by extensive manufactured from nonexplosive components safety and security regulations and is subject to (emulsion matrix plus gassing agents and/or glass competition from increasingly powerful me- microspheres plus optionally ammonium nitrate chanical means of extraction, such as mining prills or ANFO) on the quarry bench by mobile machines, rippers, and tunnel-boring machines. manufacturing units (MMU) and are pumped Although the use of explosives entails such draw- directly into blast holes on demand. Once inside backs as noise, vibration, dust, and smoke, the the blast hole they start the sensitizing reaction technique is flexible, effective, easy to use, and due to the specific weight decreasing from about low in capital and material cost. 1.4 to 1.1 g/cm3 due to the development of gas When using bulk explosives, production costs bubbles (chemical gassing process). Although the are reduced because the process of loading into emulsions are neither gelled nor reticulated, their cartridges and the labor-intensive filling of the storage life has been considerably improved by blast holes become unnecessary. In addition, using sophisticated emulsifiers. since the entire blast hole is completely filled, Emulsions differ from nitrate/fuel oil, nitrate, the filling grade is much better compared to and water gels in their higher detonation velocity. cartridged explosives, allowing the possibility The properties of typical emulsion-type products of enlarging the drilling pipe. The bulk explo- are listed in Table 7. The emulsions are sensi- sives (ANFO and EMS) make up 70 % of those tized by a chemical gassing process, apart from used in Europe, and over 80 % of those used in the Iremite 2500s, the formulation of which includes United States. They can be produced on-site in microspherical glass bubbles. Since the emulsion mobile emulsion manufacturing units (MEMUs, bulk explosives are usually sensitized just before ANFO trucks, pump trucks). filling the components into the blast holes the The introduction of improved blasting sys- unsensitized substances are not classified as an tems nowadays allows for a relatively exact explosive (class 1) and are not entirely subject to forecast of the blasting results by evaluating all the regulations for producing, handling, trans- relevant blasting parameters, such as bench and porting, and storing dangerous materials. wall dimensions, type of rock, required fragmen- About 70 % of the EMS consumed in Europe tation, avoidance of fines, reduction of noise and comes in bulk form. In 2007 emulsion explosives vibrations, and the avoidance of fly rock. These accounted for 48 % of the total European explo- systems use specific software, computerized la- sives consumption. sers, vibration-measuring equipment, electronic devices for measuring the inclination of the bore holes, and computer programs to calculate the 7.6. Uses ideal placement of the drill holes and the correct combination of delay times of the detonators for The energy provided by explosives is used in a the initiation of the explosive charges. Electronic number of ways, including explosive cladding detonators can be incorporated into such systems (see Section 3.3), metal working (forming, weld- by selecting the optimal delay time by the milli- ing, and cutting), and shearing by pyrotechnics second, whereas conventional initiation systems systems. However, the principal nonmilitary use such as electric or nonelectric detonators have of explosives is in mining, quarrying, tunneling, fixed delay intervals such as 25 ms (short period) dam building, demolition, and construction. or 250/500 ms (long period). Vol. 13 Explosives 649 8. Test Methods cartridge made with the test sample. The detona- tion wave fronts run in opposite directions in the Tests of secondary explosives are designed to two segments and collide at a precise point study detonation phenomena, to approve a prod- [82]. uct, and to verify that manufactured lots meet the More sophisticated electrical or optical requirements (i.e., quality control). methods are also available. For example, elec- Detonation phenomena (109 to 1012 s) are trical wires (switches), inserted into a cylindri- observed by laser interferometry, streak cameras, cal cartridge at precise locations, are short- and X-ray flashes, all electromagnetic methods. circuited by the passage of the detonation wave, The very high instantaneous pressures (10 – giving a signal that is recorded on a chrono- 40 MPa) are measured, e.g., with low-impedance graph. Other methods use streak cameras. The piezoresistive manganin gauges (Cu–Mn–Ni al- detonation wave is built up at a distance from loy) [79] or with fluorinated piezo polymers as the initiation point, and this occurs only if the shock sensors [102]. Phenomena are modeled on cartridge diameter is large enough. Therefore, the basis of the Becker – Kistiakowsky – Wil- this test requires an adequate quantity of son (BKW) [32] or Jones – Wilkins – Lee explosive. (JWL) [33] equations developed in the United States at the Los Alamos Scientific Laboratories Energy Output [5, 82]. In the lead block (LASL) and the Lawrence Livermore National test, strength or CUP (coefficient d’utilisation Laboratory (LLNL). pratique) is measured by the expansion of a Tests to approve a product measure detona- cavity in a lead block caused by the detonation tion velocity and pressure, energy released, of a sample of explosive, in comparison with a ability to initiate or transmit detonation, and standard (PETN, picric acid, or TNT). critical diameter. They also determine the In the ballistic mortar test, the energy released safety characteristics in use, storage, and by detonation gases is measured in a steel mortar transportation. consisting of two cavities: the first contains the The verification of a lot is usually based on the explosive, and is connected to the second, which determination of physical properties (melting contains a projectile. The assembly is suspended point, particle size, specific area) and chemical by a pendulum, and when the projectile is driven analysis. Safety and storage characteristics must out by the detonation, the recoil moves the mortar match those of the approved product. to an angle that is compared to that given by a Codified tests for military use are published in standard explosive. the United States as military specifications The Kast method is used to evaluate explosive 2 (MIL), in France as Manuel des modes brisance, a value related to the product r D operatoires , in the Federal Republic of Germany where r ¼ density and D ¼ detonation velocity. as VTL, in the United Kingdom as DEF. STAN, The crushing of a copper cylinder by the detona- and at NATO as STANAG. Japan issues Japa- tion is compared to that obtained with a standard nese Industrial Standards [81]. Unified and stan- explosive. dardized European explosives tests (EXTEST) The cylinder test has been studied at the are published in Explosifs (Belgium, 1960 – Lawrence National Laboratory, Livermore, 1970), in Explosivstoffe (FRG, 1971 – 1973), in California, [83]. The velocity transmitted by a Propellants and Explosives (FRG, 1977 to 1981), cylindrical rod of explosive to a tightly fitting and in Propellants, Explosives, Pyrotechnics copper tube is measured by a streak camera. (1982 to date) (see also [7, 10]). For more routine measurements, the Defourneaux test can be used (push-plate test). A metal plate lies on an explosive plate, which is 8.1. Performance Tests detonated by a linear wave generator. During the detonation, the metal plate is continuously bent Detonation Velocity. The Dautriche me- to an angle, which is observed, for example, by thod is based on a comparison of the velocity in X-ray flash [84]. Among other tests is underwater two parts of a circuit, composed in one section of explosion, with measurements of the bubble a known detonating cord and in the other of a produced. 650 Explosives Vol. 13

Other Performance Tests. In one of the followed visually, aurally, audiometrically, or by critical-diameter tests, the detonation propaga- examination of gas evolution. tion of metal cords (copper or silver) filled with Tests are prescribed by the U.S. Bureau of an explosive of known density is observed as a Mines, Picatinny Arsenal (United States), Ex- function of the inner diameter. In another meth- plosives Research Laboratory (United States), od, a conical charge is used. BAM (Federal Republic of Germany), Julius Other tests include the determination of the Peters (Federal Republic of Germany, France), coefficient of transmission of detonation, the Rotter (United Kingdom, Canada), and Auber- sensitivity to initiation, the self-excitation coef- tein (France). Another test is the Susan projectile- ficient (maximum distance between two car- impact test, where a projectile containing ca. tridges loaded with the same explosive, allowing 450 g of explosive is directed against a hard the initiation of one by the other), and the plate- target at selected velocities. dent test. The friction sensitivity test is even more diffi- cult to reproduce than the impact sensitivity test. A thin layer of sieved explosive on a fixed surface 8.2. Safety is rubbed by a hard or abrasive surface moved by translation (Julius Peters apparatus) or by rota- Stability. Aging effects are frequently de- tion (U.S. Bureau of Mines) under adjustable termined by the vacuum stability test, in addition pressure. to the usual chemical methods. It can be used to Impact and friction are combined in the skid study the compatibility between explosives and test (Pantex) and the Popolato test; an explosive other materials. sphere is projected against a sand-coated target The sample is placed in a test tube fitted plate at defined impact angles. with a manometric capillary glass tube; the In the electrostatic sensitivity test, a small other end of the tube dips into a cup of quantity of explosive is placed between two mercury. The tube is evacuated and the sample electrodes. A capacitor discharge causes a spark is heated, usually between 80 and 130 C. The to pass between the electrodes through the ex- variation of the inner pressure in the tube is plosive. The sensitivity is expressed by the mini- shown by the mercury level. Pressure usually mum energy required to decompose the sample. increases during the first few hours with the In addition to differential thermal analysis release of traces of moisture and volatile sub- (DTA) and thermogravimetric analysis (TGA), stances. Afterward, during a period of 100 h, the the following heat sensitivity tests are employed: rise in pressure can be linear (constant decom- position rate) or more rapid (autocatalytic 1. The sample is subjected to a constant increase decomposition). of temperature and the decomposition or ig- nition temperature is noted; the result depends Sensitivity. The impact sensitivity of an ex- on the quantity of explosive and the rate of plosive is the minimum energy that causes quick heating. decomposition [5, 13, 85]. The test conditions 2. The sample placed in a small bulb is dipped strongly influence the results, which (given in into a Wood’s metal bath maintained at a fixed Joules) are only orders of magnitude. The clas- temperature. The time to decomposition is sification of explosives depends on the apparatus noted, or the temperature at which a decom- and the test conditions. position occurs after 5 s. In the Bruceton test for impact sensitivity, the 3. The sample is ignited in a gutter and the stimulus after a positive result is lowered by one burning rate measured. unit and raised after a negative result. The value 4. The sample is externally heated in a closed or of the sensitivity is obtained as the mean of 30 – half-closed vessel. The tendency to burn or to 50 trials. Probabilistic values are also deter- detonate is observed (steel-sleeve test). mined. 5. The sample is heated at a given rate in a closed The procedures differ in the size and place- vessel. The time of detonation or the temper- ment of the sample and the use of tools exposed ature at which the sample detonates after a or covered with sandpaper. The reaction may be given time is noted (cook-off test). Vol. 13 Explosives 651

To test the sensitivity to initiation through a by the UN was first published in 1984 in the spacer (card-gap test), a sample in a steel tube is so-called Orange Book (Recommendations on subjected to the detonation of a standard booster the Transport of Dangerous Goods – Model explosive separated from the sample by a barrier Regulations and Manual of Tests and Criteria) of cellulose acetate cards of 0.19 mm thickness [86]. Substances are classified according to the [8]. The minimum number of cards that prevent type of risk involved, unless they are too danger- transmission of detonation fixes the legal class of ous to ship. Explosives are in Class 1, which the explosive for transportation and other contains six subdivisions [86]: regulations. To obtain a LOVA agreement (MURAT in Division 1.1: Substances and articles which have France), the following tests must be carried out a mass explosion hazard on ammunitions: bullet and fragment impact, Division 1.2: Substances and articles which have slow and fast cook-off tests, reaction towards a a projection hazard but not a mass explosion shaped-charge jet, and sympathetic reactions. hazard The results depend on storage of the ammuni- Division 1.3: Substances and articles which have tions, their design, and on the properties of the a fire hazard and either a minor blast hazard or propellants and explosives they contain [95, 20]. a minor projection hazard or both, but not a These investigations are supported by the NATO mass explosion hazard Insensitive Munitions Information Center (NI- Division 1.4: Substances and articles which pres- MIC, Brussels). ent no significant hazard Division 1.5: Very insensitive substances which have a mass explosion hazard 9. Legal Aspects and Production Division 1.6: Extremely insensitive articles which do not have a mass explosion hazard European Directives and national legislation strictly regulate the possession, production, stor- Class 1 is restricted, containing only regis- age, packaging, shipping, handling, use, export, tered substances; for new substances, test results import, transfer, and trading of explosives. Peri- must be presented. Simultaneous transport and odic inspections and labeling prevent theft. Tag- storage are permitted for ‘‘compatibility ging the explosive permits tracing its origin. In groups’’. cases where unauthorized explosives are found, The transportation regulations specify there is an absolute necessity to identify the last packaging and labeling instructions, an identify- official owner of these explosives as quickly as ing insignia on vehicles, compatibilities, and possible. For this reason an EC Directive on the maximum load and safety devices on vehicles. identification and traceability of explosives for Manufacture and storage are governed by the civil use was passed in 2008. Under the Directive TNT equivalency, which is defined as the quan- all explosives articles would be marked with a tity of TNT producing the same effects as 100 kg unique identification both in human-readable and of the explosive [87]. in bar-code or matrix-code format. Implementa- The expression d ¼ kQ1/3 gives the safe tion of the scheme should be taken forward by the distance from a load Q of explosive (expressed EC member states in 2012 at the latest. The ADR as TNT equivalent), where the constant k de- regulations regulate the transport, packaging, pends on the presence of walls or other and labeling of hazardous goods such as explo- protection. sives on the road. Other organizations like the IMO and ICAO regulate transport by sea and air accordingly. 9.2. Production of Military Explosives

High explosives are manufactured by private 9.1. Safety Regulations companies in many countries, e.g., Russia, United States, China, India, United Kingdom, Originally, each country established its own Germany, Norway, Sweden, Switzerland, and regulations; the standardization recommended Japan. 652 Explosives Vol. 13

In the United States, research and develop- their toxicity is very low. However, there have ment involving high explosives are often under- been reports of epileptiform convulsions, with- taken in military laboratories. Production is con- out liver involvement, or carcinogenic or muta- ducted by arsenals or by private companies under genic effects. Dust formation should be avoided the GOCO system (Government owned – con- and masks should be worn. tractor operated), in which investments and fac- tories are owned by the government. The product is government property and cannot be sold by the operating company. References Since 1990 the production and consumption volumes in the EU of explosives for defense General References purposes have reduced to a few thousand tonnes 1 Ullmann’s Encyklopadie€ der Technischen Chemie,4thed., annually. 21, 637 – 697, Verlag Chemie, Weinheim 1972–1984. 2 T. Urbanski: Chemistry and Technology of Explosives, Pergamon Press, Oxford 1983 – 1985. 10. Toxicology and Occupational 3 A. Marshall: Explosives, 2nd ed., P. Blakiston’s Son and Co., Philadelphia 1917. Health 4 B. T. Fedoroff et al.: Encyclopedia of Explosives and Related Items, U.S. Army and National Technical Infor- Raw Materials. Both acids (HNO3 and mation Service, Springfield, Va., 1960 – 1983. H2SO4) and benzene derivatives (toluene and 5 R. Meyer: Explosives, 2nd ed., Verlag Chemie, Wein- chlorobenzene) are of concern [4]. The usual heim-New York 1981. safety measures must be followed to protect eyes, 6 Kirk-Othmer, 9, 561 – 620, and 15, 841 – 853. skin, and respiratory tract. Red fumes of nitrogen 7 B. M. Dobratz: LLNL Explosives Handbook, UCRL Report 52 997, Livermore, Calif., 1981. B. M. Dobratz: oxides, formed normally or by accident, can induce lung edema two days after exposure; the LLNL Explosives Handbook, UCRL Report 52 997, Change 2, Livermore, CA 1985. use of a gas mask is recommended. 8 J. Quinchon et al.: Les explosifs, 2nd ed., Technique et Documentation, Paris 1987. Explosives. Some primary explosives are 9 J. Quinchon, R. Amiable, P. Chereau: Securit e et hygiene toxic (mercury fulminate and certain lead salts), du travail dans l’industrie des substances explosives, but the toxic hazards are far below those arising 2nd ed., Technique et Documentation, Paris 1985. from high sensitivities to detonation. Among the 10 L. Medard: Les explosifs occasionnels, Technique et secondary explosives, nitroglycerin and other Documentation Paris 1979, (engl. Transl.: Accidental liquid nitrates exhibit hypotensive action accom- Explosives), Ellis Horward Ltd (Distrib. J. Wiley & Sons) 1987. panied by headaches and, in chronic cases, by 11 J. Calzia: Les substances explosives et leurs nuisances, methemoglobinemia. A tolerance to nitroglycer- Dunod, Paris 1969. in can be developed. These substances are usu- 12 S. Fordham: High Explosives and Propellants, 2nd ed., ally absorbed through the skin rather than by Pergamon Press, Oxford 1980. inhalation. For nitroglycerin and glycol dinitrate, 13 H. D. Fair, R. F. Walker: Energetic Materials. Inorganic TLV ¼ 1.5 mg/m3. PETN, which like nitroglyc- Azides, Plenum Press, New York 1977. erin is prescribed for heart diseases, has a very 14 Houben-Weyl, XI and XI2, 99 – 116. low vapor pressure and is not readily absorbed by 15 Structure and Properties of Energetic Materials, Symp. , Materials Research Society 1992. the skin. Proceedings, vol. 296 Composition, Combustion and Detonation Chemistry of The toxic effects of TNT include blood Energetic Materials, Symp. Proceedings, vol. 418, Ma- changes, cyanosis, methemoglobinemia, and terials Research Society, Pittsburgh, USA, 1995. toxic hepatitis. It is introduced by inhalation, 16 J. E. Field, P. Gray, Energetic Materials, The Royal ingestion, and skin absorption; at inhalation Society, London 1992. level, TLV ¼ ca. 1 mg/m3. Dust in the plant is 17 Approches microscopique et macroscopique des deto- er to be avoided. nations, Journ. de Physique, Suppl., 1 atelier int. (31. can induce an allergic dermatitis, there- May — 07. June 1987). Approches microscopique et Tetryl macroscopique des detonations, Journ. de Physique, fore its use is practically abandoned. Suppl., 2e atelier int. (02. — 07. October 1994). Both RDX and HMX have negligible vapor 18 Proc. Int. Symp. Energetic Materials, Paris, May 1994; pressures. They do not penetrate the skin and International Defense et Technologie, Sept. 1994. Vol. 13 Explosives 653

19 Europyro, 5e Congres Int. de Pyrotechnie, 1993. Euro- 43 C. M. Tarver, J. O. Hallquist, Symposium (International) pyro, 6e Congres Int. de Pyrotechnie, 1995. Europyro, 7e on Detonation, 7th, Office of Naval Research Report Congres Int. de Pyrotechnie, 1999. NSWC MP 82 – 334 (1981). 20 Insensitive Munitions Technology Symposium, ADPA 44 F. E. Walker, R. J. Wasley, Explosivstoffe 17 (1969) 9. (American Defense Preparedness Association) 1996. 45 Y. de Longueville, C. Fauquignon, H. Moulard, Sympo- 21 Life Cycle of Energetic Materials, Conferences Pro- sium (International) on Detonation, 6th, Office of Naval ceedings (1993, 1994, 1996), Los Alamos Lab. Research Report ACR-221 (1976). 22 G. A. Olah et al., Nitration. Methods and Mechanisms, 46 D. Price, Symp. (Int.) Combust. 11th (1967) 963. VCH Publishers 1989. Useful periodicals treating 47 S. J. Jacobs, Naval Ordnance Laboratory Technical explosives include ICT Intern. Jahrestg. (1970 to date); Report 74 – 86. 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76 G. Roche, ICT Intern. Jahrestg. 1978, 235 – 242. bility of Plastics with Explosives, Proceedings, San 77 L. R. Rothstein, ICT Intern. Jahrestg. 1982, 245 – 256. Diego 1991, 69 – 79. 78 C. Gaudin, ICT Intern. Jahrestg. 1978, 243 – 254; 98 A. Becuwe, A. Delclos, Prof. Exp. Pyro. 18, 1993, 1–10. 1981, 541 – 551. 99 A. Nielsen, J. Org. Chem. 55 (1990) 1459 – 1466. 79 M. J. Ginsberg, A. R. Anderson, J. Wackerle, Symposium 100 V. A. Tartakowsky, O. A. Lukyanov, ICT Int. Jahrestg. sur les jauges et materiaux piezoresistifs, 1st, Arcachon, 1994, 13, 1 – 9. A. Davenas, [18], 69 – 71. H. Hatano, France, 1981. L. M. Erickson et al., ibid. et al. Europyro (AFP), 6e Congres Int. Pyrotechnie 80 J. Boileau, MRS Symposium Proceedings 418 (1996) Tours, 1995, 23 – 26. 91 – 102. 101 J. Boileau et al., Acta Cryst. Sect. C 44 (1988) 696. 81 I. Fukiyama, Propellants Explos. 5 (1980) 94 – 95. 102 F. Bauer, H. Moulard, 4e Symposium Hautes Pressions 82 H. Ahrens, Propellants Explos. 2 (1977) 7 – 20. Dynamiques (AFP), 1995 333 – 340. R. A. Graham, L. 83 J. W. Kury et al., Symposium on Detonation, 4th (1965) M. Lee, F. Bauer, Proceedings of Shock Waves in 3. Condensed Matter, Elsevier SC Publ. 1988, 619. 84 M. Defourneaux, Sciences et Techniques de l’Armement 103 B. Blaive et al., Europyro (AFP), 6e Congres Int. Pyro- 47 (1973) 723 – 814, 847 – 930. technic Tours, 1995, 413 – 419. 85 K. N. Bascombe, R. M. H. Wyatt, ICT Intern. Jahrestg. 104 H. Moulard, 9th Int. Symposium on Detonation (OCNR 1976, 211 – 231. 113291–7), 1989, 18 – 24. 86 United Nations Organization: Transport of Dangerous 105 L. Borne, 10th Int. Symposium on Detonation (ONR Goods, 14th ed., 2005. 33395–12), 1993, 286 – 293. 87 D. M. Koger, ICT Intern. Jahrestg. 1980, 549 – 560. 88 J. Ding, The discovery of gunpowder and shockwaves in China — CETR rep. A 12–89, New Mexico Tech., Soccoro, 1989. Further Reading 89 A. B. Sheremetev, T. S. Pivina, ICT Int. Jahrestg. 1996, 30, 1 – 11. J. Akhavan: Explosives and Propellants, ‘‘Kirk Othmer En- 90 FR 1060425, 1952 (C. Frejacques). J. P. Passarello, cyclopedia of Chemical Technology’’,5th edition, vol. 10, Thesis (ENSTA-Paris), 1996. p. 719–744, John Wiley & Sons, Hoboken, 2005, online:. 91 R. W. Millar et al., ICT Int. Jahrestg. 1996, 26, 1 – 14. J. Fraissard, O. Lapina: Explosives Detection using Magnetic 92 R. B. Wardle, et al., ICT Int. Jahrestg. 1996, 27, 1 – 10. and Nuclear Resonance Techniques, Springer, Dordrecht 93 M. F. Foltz, Prop. Exp. Pyro. 19, 1994 63–69 and 133– 2009. 144. N. Kubota: Propellants and Explosives, 2nd ed., Wiley-VCH, 94 N. V. Chugehov, F. Volk, ICT Intern. Jahrestg. 2001, Weinheim 2007. 101, 1–9. C. L. Mader: Numerical Modeling of Explosives and Pro- 95 A. Sanderoon (NIMIC-NATO), ICT Int. Jahrestg. 1996, pellants, 3rd ed., CRC Press, Boca Raton 2008. 18, 1 – 8, and references given in this paper. M. Marshall, J. C. Oxley: Aspects of Explosives Detection, 96 B. M. Dobratz, TATB, Development and Characteriza- Elsevier Science, Amsterdam, 2008. tion 1888 to 1994, LA 13014 H, Aug. 1995, UC 741, Los R. L. Woodfin: Trace Chemical Sensing of Explosives, Wiley, Alamos Nat. Lab. (NM 87545). NJ 2007. 97 K. Y. Lee et al., J. Energ. Mat. 5 (1987) no. 1, 27 – 33. J. Yinon: Counterterrorist Detection Techniques of Explo- A. Becuwe, A. Delclos, ITC Int. Jahrestg. 1987, 27, 1 – sives, Elsevier Science, Amsterdam, 2007. 14. M. Piteau, A. Becuwe, B. Finck, ADPA, Compati-