Falecki, Mint, Slebodziliski and T. Urbanski, [185a] have also found that paraffin hydrocarbons dissolved in dinitrogen tetroxide are nitrated at 28°C when they are subjected to irradiation with gamma rays. The yield for n-hexane was up to 15% of non-gaseous products of both nitration and oxidation. The charac- teristic feature of the reaction differentiating it from nitration at elevated tempera- ture described above (p. 94) is the fact that no pyrolysis of the hydrocarbon occurs, and therefore long chain paraffins are not so readily split into shorter fragments as it occurs at high temperature. The authors also found that n-hexane reacts with dinitrogen tetroxide at 28°C without irradiation. However, the yield of non-gaseous products is lower (ca. 8%) and the products containing nitrogen are mainly nitrous esters. This would suggest that N 2 O 4 probably forms ions NO 2
Picric acid, or 2,4,6-trinitrophenol is a sensitive compound that can be used as a booster charge for moderately insensitive explosives, such as T.N.T. It is seldom used for explosives anymore, but it still has applications in many industries, including leather production, copper etching, and textiles. Picric acid is usually shipped mixed with 20% water for safety, and when dried it forms pale yellow crystals. In small quantities picric acid deflagrates, but large crystals or moderate quantities of powdered picric acid will detonate with sufficient force to initiate highexplosives (or remove the experimenter's fingers). Picric acid, along with all of it's salts, is very dangerous, and should never be stored dry or in a metal container. Contact with bare skin should be avoided, and ingestion is often fatal.
A variation of this approach is the “molecular wire” config- uration, in which the absorption of a single photon of light by any chromophore will result in a chain reaction, quenching the fluorescence of many chromophores and amplifying the sensory response by several orders of magnitude (Figure 1b) (6). One example of this is a polymer used by Nomadics (6–8), which was originally developed by Swager’s group at the Massachusetts In- stitute of Technology (9–11). The polymer reacts with aromatic nitrocompounds, and thin films of it display high-fluorescence quantum yield and stability for the vapors of TNT and 2,4-dini- trotoluene (2,4-DNT), in particular. This conjugated polymer consists of three-dimensional pentiptycene groups. The back- bone of the polymer acts as a molecular wire, enabling the prop-
a. The fundamental principle for protecting life and property against lightning is to allow a lightning discharge to enter or leave the earth without resulting damage or loss. A low impedance path should be offered, which the discharge current will follow in preference to all alternative high impedance paths offered by building materials such as wood, brick, tile, stone, or concrete. When lightning follows the higher impedance paths, damage may be caused by the heat and mechanical forces generated during the passage of the discharge. Most metals, being good electrical conductors, are virtually unaffected by either heat or the mechanical forces if they are large enough to carry the current that can be expected. The metal path must be continuous from the earth electrode system to the air terminal. Care should be exercised in selecting metal conductors (Table 12–1) to ensure the integrity of the lightning conductor for an extended period. A nonferrous metal such as copper or aluminum will provide, in most atmospheres, a lasting conductor free of the effects of rust or corrosion.
A major complication is due to melting. On the micro-second time scale of shock initiation, the burn rate is only significant above the melting temperature. But when a material melts the yield strength vanishes and the shear viscosity is greatly diminished. Hence melting limits the dissipation from plastic work and frictional heating. Moreover, the simulations have neglected the crystal anisotropy of the HMX grains. In addition, the resolution of the simulations is limited. Half the mass of a grain is within 2 cells of its interface. With higher resolution the dissipative energy is likely to be more concentrated. This would result in hot spots having a higher peak temperature but a smaller area. Consequently, the temperature distribution in these simulations should be regarded as qualitative in nature. They do show that compressive waves in a granular bed lead to hot spots with sufficiently high temperature for reaction.
A chemical change or decomposition, accompanied by the liberation of heat is described as ‘exothermic or heat liberating. This occurs when Iron rusts (or oxidises) but so slowly that the heat is dissipated before it has any effect on Its surroundings. Other substances. such as wood or coal ‘burn’ more quickly, that is to say they com- bine with the oxygen in the atmosphere to the accom- paniment of flame and smoke and the heat liberation is more apparent. The process is further speeded up when an explosive substance is induced to undergo a similar change; but the effects now become so rapid that vast quantities of heat-expanded gas are liberated in such a way as to produce sudden high pressures. Moreover, most explosive substances contain their own ‘built-in’ oxygen so that they can be initiated when confined. See Fig 2 for the definition of explosion
Beside crack formation, the detachment of the polymeric matrix can lead to failures of the system. The detachment of the matrix occurs in two steps. The first step is the stress concentration at filler particles producing high local stress values. The values can reach up to the double of the applied stress. If the stress level reaches a critical value, a cavity is formed. The cavity propagates if the stress is increased until it reaches the polymer matrix. In the second step, the stress field at the filler binder interface is modified, leading to “peeling”.  The voids resulting from a detachment of the polymer increase the impact sensitivity, due to a heating up of the gases inside the voids in case of rapid compression (impact). Therefore, not only cracks but also detachment or dewetting of the polymeric matrix from the explosive can lead to unexpected accidents. [55,54] In order to prevent the cavities to be formed, three possibilities were reported by Oberth and Bruenner.  The first possibility is the formation of chemical bonds between the
The mechanical properties of propellants are important to the formulation of the desired propellant grains. During the pressure build-up process in a rocket motor such as during the ignition transient or unstable burning in the chamber or very high pressure (> 1 GPa) in gun tubes, very high mechanical stresses act on the grains. If the internal grain shape is complicated, increased chamber pressure causes a crack in the grain and increases the burning surface area. The increased burning surface area due to an unexpected crack increases the chamber pressure, which can cause a catastrophic explosion of the rocket motor or the gun tube. In general, mechanical properties of propellants are dependent on the environmental temperatures. Elongation properties of propellants become poor at low tempera- tures (approximately below 200 K). This causes in-depth crack formation when a mechanical stress acts on the grain at low temperatures. On the other hand, strength properties become poor at high temperatures (approximately above 330 K). This causes deformation of the grain when an external force such as acceleration force or gravitational force acts on the grain. Accordingly, the selection of propellant ingredients to form the propellant grain shape is not only dependent on the com- bustion performance but also the mechanical properties of the formed propellant grain. The design criteria of gun propellants are different from those of rocket pro- pellants. The size and mass of each grain of gun propellants are much smaller than those of rocket propellants. The burning surface area per unit mass of propellant is much larger for gun propellants. Furthermore, the operational combustion pressure is in the order of 1 GPa for gun propellants and 1 ± 10 MPa for rocket propellants.
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A combination of 20th century warfare alongside the storage of and frequent testing of munitions by various national armed forces has contributed to a legacy of unexploded ordnance, munitions, and explosives of concern (MEC). The presence of such latent munitions has potentially debilitating or even fatal effects upon a generally unsuspecting stakeholders where communities may be unaware of the risks posed by buried shells, bombs, and other ordnance on both public and privately held properties. As such, various governments have undertaken differing initiatives to assess, mitigate, and manage the risks associated with these munitions. MEC remediation is generally tailored to each nation's unique historical experience with munitions and ordnance and is highly dependent not only on the type and quantity of MEC but also on the existing or proposed land use of the parcel as well. This paper compares the MEC management efforts of the United States, the United Kingdom, Germany, and Canada with regard to their MEC monitoring, detection, and removal methods in order to identify successful policies and procedures that can inform international MEC management.
b. External Charges. To be most effective, external charges should be rectangular, 1 to 2 inches thick, and twice as wide as they are high. Remove the bark to place the explosive indirect contact with solid wood and to reduce air gaps between the charge and the wood. If the timber is not round or if the direction of fall is not important, place the explosive on the widest face. Doing this will concentrate the force of the blast through the least dimension of the timber. Trees will fall toward the side on which the explosive is placed, unless influenced by wind or lean of the tree (Figure 3-3). If the tree is leaning the wrong way or a strong wind is blowing, place a l-pound kicker charge on the side opposite the main charge, about two-thirds of the way up the tree. Fire the kicker charge at the same time as the main charge. For best results when using C4, orient the charge’s longest dimension horizontally. Orienting the charges vertically tends to allow gaps to develop between the charges. Example A-2
Recrystallization, product recovery, and filtration page 17 Washing liquid and solids page 20 Drying agents, and drying liquids page 21 Distillation page 22 Final lesson: A tutorial on explosives page 24 The dynamics of detonation page 25 Detonation verses deflagration and combustion page 26 Primary, and secondary explosives page 27 Initiation of explosives page 28 The power of explosives page 29 The physical effects of explosives page 30 Section III:
Since polymer bonded explosives such as PBX 9501 contain two widely separated particle sizes, a number of manually generated microstructures of PBX 9501 have been simulated. The models were designed to contain a few large particles and a larger number of smaller interstitial particles while avoiding particle-particle contact. Such models have been found to underestimate the Young’s modulus of PBX 9501 considerably when discretized with triangular elements. However, when the same models are discretized with square elements, considerably different estimates of Young’s modulus are obtained depending on the degree of discretization. Hence, it is extremely difficult to determine an appropriate RVE for high modulus contrast and high volume fraction particulate composites that has the optimal size, number of particles, particle shapes and size distributions. The RVE also has to be such that it can be easily discretized using elements that are accurate and relatively computationally inexpensive.
The organization of this paper is as follows. Section 2 discusses the rationale behind using RSRG approaches for high volume fraction particulate composites. The RCM is described in Section 3 and homogenization techniques appropriate to this method are presented. Section 4 provides background in- formation on PBXs and PBX 9501, bounds and analytical estimates of the eﬀective properties of PBX 9501, followed by a brief discussion of the diﬃculties associated with direct ﬁnite element and generalized method of cells analyses of PBX microstructures. Predictions from the RCM using diﬀerent homogenizers are discussed in Section 5. Finally, the results are summarized and conclusions presented in Section 6.
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General. Caution: TNT and picric acid are high explosi V es and should be handled only in small quantities. Picric acid also forms shock sensiti V e compounds with hea V y metals. All synthetic manipulations were carried out under an atmosphere of dry argon gas using standard vacuum-line Schlenk techniques. All solvents were degassed and purified before use according to standard literature methods: diethyl ether, hexanes, tetrahydrofuran, and toluene were purchased from Aldrich Chemical Co. Inc. and distilled from sodium/benzophenone ketyl. Spectroscopic grade toluene from Fisher Scientific was used for the fluorescence measurements. NMR grade deuteriochloroform was stored over 4 Å molecular sieves. All other reagents (Aldrich, Gelest) were used as received or distilled before use. NMR data were collected with Varian Unity 300, 400, or 500 MHz spectrometers (300.1 MHz for 1 H NMR, 75.5 MHz for 13 C NMR and 99.2 MHz for 29 Si NMR).