Solid desensitized explosives

Class 4.1 Flammable solids, self-reactive substances, and solid desensitized explosives... 

Class 4.1 Flammable Solids, Self-reactive Substances and Solid Desensitized Explosives... 

D Solid desensitized explosives without subsidiary risk DT Solid desensitized explosives, toxic SR Self-reactive substances ... 

The heading of Class 4.1 covers flammable substances and articles, desensitized explosives which are solids according to the definition for solids in the CHS regulation and self-reactive liquids or solids. 

According to regulatory definitions, flammable solids include combustible, self-reactive, and desensitized explosive solids. In general, flammable solids decompose at elevated temperatures or, in fire, bum vigorously, decompose in contact with acids or alkalis, and can produce toxic reaction products. 

This class comprises . 1 readily combustible solids, and solids which may cause fire through friction . 2 self-reactive (solids and liquids) and related substances . 3 desensitized explosives. IMO Class 4.1,1.2... 

The following types of substances are classified in Division 4.1 a) flammable solids b) self-reactive and related substances and c) desensitized explosives. ICAO 2-4.1.1... 

Composition D-2, This composition consists of a mixture of desensitizing wax 84, lecithin 2 Nitrocellulose 14%. It is prepared by melting mixing the ingredients in the above amounts When the mixture is uniform and free from any visible impurities, it is cast in the form of slabs not more than 2 inches thick, or in the form of pellets not more than 2 "x 2 " in size. Composition D-2 is used to emulsify desensitize solid explosives or mixtures of explosives. The detailed US Military requirements of Composition D-2 are given in Ref 2, where the tests are also described... 

Acetone-Pis an unstable, white powder or crystalline mass with a melting point of 90 to 93 Celsius. The solid is insoluble in water, but soluble in ether and tetrahydrofuran. It is quite unstable and is rarely used in military or commercial explosives. However it can be utilized as a primary explosive in blasting caps or detonators when desensitized with appropriate materials. To do so, it should be mixed with gum Arabic, carbon black, tri sodium phosphate, chalk, or silicon dioxide powder, and then mixed with a small amount of paraffin s or saturated oils prior to use. Acetone-P can also be slurried with 10% water and 5% hexane for use in blasting caps or detonators. Pure acetone-P should not be used by itself, as it will decay over time potentially leading to explosions. Acetone-P is rather volatile, and a small sample left out in the open will completely evaporate after several days—partly due to decomposition. Acetone-P can also be used in initiating compositions when mixed with sulfur nitride or other primary explosives, and then added to a small amount of a saturated oil. The sulfur nitride and other primary explosives can be replaced by bari urn chromate, copper perchlorate, or lead chromate. Even when acetone-P has been successfully desensitized, it should be used withi n 2 weeks of preparation. ... 

NG has a relatively low molecular mass, 227.1 kg/kmol, is liquid at room temperature, and becomes a solid state below 286 K[1,21. Since NG is shock sensitive and easy to detonate, desensitizers are admixed for practical applications. NG is one the major ingredients used for propellants and explosives. Typical examples are doublebase propellants mixed with nitrocellulose, and dynamites mixed also with nitrocellulose and/or other crystalline materials. The autocatalytic decomposition of NG, occuring at 418 K, is caused by the bond breakage of -0-N02 and evolves N02 with an activation energy of 109 kj/mol. The self-ignition occurs after a critical concentration of N02 is achieved at 491 K. 

Desensitizers are used to reduce hazards in handling or to modify the explosive effect. Camphor is mixed with gunpowder to modify its burning rate. Easily detonated explosives may be mixed with less sensitive explosives resulting in a desensitized mixture. TNT, for example, is used to desensitize octol, even while it supplements its explosive power. These may not be sufficiently desensitized to meet the criteria of flammable solids. 

Certain materials including some explosives, oxidizers, and organic peroxides are subject to violent reaction on exposure to heat, friction, impact, or certain chemicals. This risk may be reduced by the addition of a compatible desensitizer (e.g., water, organic liquids or solids, or inorganic solids) during transportation. Sensitized materials are those that have a reactive substance added to them to make them more sensitive. For example, relatively insensi-... 

The study to determine the mechanism of the explosive desensitization by preshocking used the three-dimensional reactive hydrodynamic code, 3DE, described in Appendix D. A constant velocity piston was applied to the bottom of a TATB explosive cube shocking the explosive to the desired pressure. When a higher pressure second shock was to be introduced, the piston velocity was increased and other piston state values changed appropriately for a multiple shock of the required pressure. The Arrhenius reactive rate law was used for TATB with the constants determined for solid TATB by Raymond N. Rogers shown in Table 3.1 of an activation energy of 59.9 kcal/mole and a frequency factor of 3.18 x 10 t sec T... 

Keep solid material wet or soaked with solvent as long as possible. In mixture with liquids explosives are normally desensitized (phlegmatized). Favoured solvents for this purpose are nonflammable solvents like water or halogenated hydrocarbons. Only highly sensitive compounds like primary explosives can detonate without obvious reason even when they are stored under water. It is supposed that these unexpected explosions are caused by internal stress of larger crystals leading to crystal cracks. 

HMX and RDX are chemically very similar except that HMX is not easily decomposed by alkaline hydroxide. Concentrated sulfuric acid liberates a little more than one third of nitric acid with HMX while with RDX a little more than two thirds is liberated. HMX is used as an explosive charge when desensitized, as a booster charge in admixtures with TNT called octols, and as an oxidizer in solid rocket and gun propellants. 

RDX is a white, crystalline solid with a melting temperature of 204 °C. It attained military importance during World War II since it is more chemically and thermally stable than PETN and has a lower sensitiveness. Pure RDX is very sensitive to initiation by impact and friction and is desensitized by coating the crystals with wax, oils or grease. It can also be compounded with mineral jelly and similar materials to give plastic explosives. Insensitive explosive compositions containing RDX can be achieved by embedding the RDX crystals in a polymeric matrix. This type of composition is known as a polymer bonded explosive (PBX) and is less sensitive to accidental initiation. 

Organic peroxides and hydroperoxides are generally unstable and can decompose spontaneously and explosively under thermal and mechanical stress. Such decomposition may be caused by shock, impact, friction, or the catalytic effect of impurities. To reduce hazards involved during transportation and handling, they are desensitized by the addition of inert inorganic solids or liquids like water, halogenated hydrocarbons. 

Uses are mainly as plasticizer and stabilizer in the production of - cellulose acetate-based cigarette filters (- tobacco industry). Other outlets are binder for solid rocket fuels, desensitizer for - explosives and plasticizer for cellulose nitrate. Mixtures of diacetin and triacetin are used as curing agent for silicate-based core binders in the - foundry industry. 

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