Volatility, military explosives

The requirements of a military explosive are very stringent and very few explosives meet all the characteristics necessary to make them acceptable for military applications. In order to determine suitability of an explosive for military applications, explosives are first investigated for properties described in the previous section followed by their study from the point of view of volatility, toxicity, hygro-scopicity and density which are considered of paramount importance because of field conditions and optimal performance requirement. 

Volatility or readiness with which a substance vaporizes, is an undesirable characteristic for military explosives. Explosives must be no more than slightly volatile at the temperature at which they are loaded or at the highest storage temperature. Excessive volatility often results in the development of pressure within the rounds of ammunition and separation of mixtures into their constituents. Volatility also affects chemical composition of the explosive resulting in the marked reduction in stability leading to an increase in the danger of handling. 

MX Schwarz, The Mass Spectra of Volatile Constituents in Military Explosives , 18 pp... 

TNT is the most widely used military explosive in history. The reasons for its popularity are its low cost and simplicity of preparation, safe handling (low sensitivity to impact and friction), relatively high explosive power (yet good chemical and thermal stability), low volatility and toxicity, compatibility with other explosives, and a low melting point, allowing for melt-casted formulations. 

Military and ammunition sites contaminated with explosives can cover substantial areas (Gerth et al. 2005). Soil contamination in these sites is often heterogeneous. Explosives are relatively non-volatile, and have low aqueous solubility. Sampling from sites within a few decimetres of one another can result in concentration differences of up to one hundredfold (Jenkins et al. 1996). For example, the coefficients of variation across samples taken from 11 abandoned sites in the USA were 248% for TNT and 137% for Hexogen (Crockett et al. 1998). As a result, sampling error greatly exceeds measurement error. Thus to obtain representative results... 

Plastic explosives contain one or more of the explosives listed above, moulded in an inert, flexible binder. Because powders do not readily hold a shape and TNT is the only common melt-castable explosive, most of the explosive powders (RDX, HMX, PETN, 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)) are plasticized to make a mouldable material, for example, C-4, Semtex H, PE4, sheet explosive. A variety of plasticizers are added, but the maximum level is usually 10-15% because most plasticizers are inert and would degrade explosive output. Plastic explosives were originally developed for convenient use in military demolitions but have since been widely used in terrorist bombs. For detection techniques that rely on vapour signatures, such as canine olfaction, it is worth considering that the plasticizer is much more volatile than the explosive component. 

Vincennite. Poisonous mixt used by the Fr in WWI in chemical shells. It consisted of hydrogen cyanide 50, As trichloride 30, Sn tetrachloride 15, and chloroform 5%. There was difficulty in obtaining toxic concns in field use because of the extreme volatility of the hydrocyanic acid Ref J. Bebie, Explosives, Military Pyrotechnics and Chemical Warfare Agents , Macmillan Co, NY (1943), 160... 

Two tests are current in the USA for the determination of moisture and volatiles in expls. They are contained in Military Standard-Explosive Sampling, Inspection and Testing , MIL-STD-650 (3 Aug 1962), and are reproduced below verbatim ... 

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. ... 

It si ton Id also be realized that the military gas mask docs not supply or make air or oxygon and bonce should never be used in an atnu s diere deficient in oxygen. TuimelK and shafts of mine> following an explosion, the liolds of. hipK, and tanks and tank car containing volatile liquids are places likely to be dangerou.s in this respect. 

The lower volatility of JP-8 is a significant factor in the U.S. Air Force conversion from JP-4, since fires and explosions under both combat and ordinary handling conditions have been attributed to the use of JP-4. In examining the safety aspects of fuel usage in aircraft, a definitive study (15) of the accident record of commercial and military jet transports concluded that kerosene-type fuel is safer than wide-cut fuel with respect to survival in crashes, in-flight fires, and ground fueling accidents. However, the difference in the overall accident record is small because most accidents are not fuel-related. 

In this section, some of the operational experiences and recent developments for explosives detection are discussed. Most of the data in this section were published by law enforcement agencies or supplied by manufacturers of commercial IMS devices. Thus, there is an emphasis on practical aspects and field tests. The descriptions are based mainly on the manufacturers claims and brochures, except if objective reports on comparative evaluations and field tests were available. The common or conventional explosives that contain nitro functional groups can be divided into two categories relatively volatile substances such as NG and EGDN and low-vapor-pressure materials such as RDX, PETN, and HMX. The vapor pressure of TNT is between these two groups. There are several commercial and military composites that are mixtures... 

In an early work [30], CI-MS of explosives was studied, using methane as reagent gas. Some of the explosives were introduced into the mass spectrometer by a packed column GC and some via a solid probe. The compounds analyzed by GC MS included simple nitroaromatic derivatives of benzene, toluene, aniline, and phenol and the explosives TNT, EGDN and NG. The less volatile explosives PETN and RDX as well as the thermally labile tetryl, were introduced via a solid probe. The military plastic explosive Composition C-3 and the commercial dynamite Hi-drive were extracted with acetone and the extracts were analyzed by GC-CI-MS. Mononitrotoluenes, 2,4-DNT, 2,6-DNT, TNT and RDX were identified in the plastic explosive, while NG and EGDN were identified in the dynamite. 

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