Nitrocellulose secondary explosives

Secondary explosives (also known as high explosives) are different from primary explosives in that they cannot be detonated readily by heat or shock and are generally more powerful. Secondary explosives can be initiated to detonation only by a shock produced by the explosion of a primary explosive. Widely used secondary explosives include trinitrotoluene (TNT), tetryl, picric acid, nitrocellulose, nitroglycerine, nitroguanidine, cyclotrimethylenetrinitramine (RDX), cyclotetramethylenetetranit-... 

Pentaerythritol tetranitrate (PETN) is a colorless crystalline solid that is very sensitive to initiation by a primary explosive. It is a powerful secondary explosive that has a great shattering effect. It is used in commercial blasting caps, detonation cords, and boosters. PETN is not used in its pure form because it is too sensitive to friction and impact. It is usually mixed with plasticized nitrocellulose or with synthetic rubbers to form PBXs. The most common form of explosive composition containing PETN is Pentolite, a mixture of 20 to 50% PETN and TNT. PETN can be incorporated into gelatinous industrial explosives. The military has in most cases replaced PETN with RDX because RDX is more thermally stable and has a longer shelf life. PETN is insoluble in water, sparingly soluble in alcohol, ether, and benzene, and soluble in acetone and methyl acetate. 

The chemical structures of some common mifttary explosives are shown in Figure 1. These include the nitrate esters such as nitrocellulose (NC), NG, EGDN, and (PETN) nitroarenes such as trinitrotoluene (TNT, CH3—C6H2(N02)3), picric acid (HO—C5H2(N02)3), and 2,4,6-trinitrophenylmethylnitramine (tetryl) and nitramines such as RDX (C3H6N6O6), HMX (C4H8N8O8), and hexanitrohexa-azaisowurtzitane (CL— 20). Of these, only CL— 20 is new , that is, less than 50 years old [3]. Mixtures of oxidizers and fuels, such as AN and FO (called ANFO), are also secondary explosives. 

Examples of secondary explosives are TNT, tetryl, picric acid, nitrocellulose, nitroglycerine, nitroguanidine, RDX, HMX and TATB. Examples of commercial secondary explosives are blasting gelatine, guhr dynamite and 60% gelatine dynamite. 

Nitroglycerine is a very powerful secondary explosive with a high brisance, i.e. shattering effect, and it is one of the most important and frequently-used components for gelatinous commercial explosives. Nitroglycerine also provides a source of high energy in propellant compositions, and in combination with nitrocellulose and stabilizers it is the principal component of explosive powders and solid rocket propellants. 

Above we presented the question of non-steady combustion applied to secondary explosive materials. With respect to the combustion of smokeless powder, a possible complicating factor is its multicomponent composition. Of interest in this connection is the fact cited by Andreev [15] of steady combustion of nitroglycerin gelated by 1% nitrocellulose. In the case of smoky powders and pipe mixtures the role of condensed combustion products which adhere to the burning surface and accumulate heat may be important. 

The liquid is widely used when admixed with nitroglycerine for cold weather resistant dynamites and blasting compositions, It can be slurried with nitrocellulose, nitro starch, and other secondary explosives for use in blasting dynamites. EGDN is also... 

DNAN forms colorless crystals with a melting point of 120 Celsius. It is fairly soluble in hot water, hot ethanol, methanol, and acetone. It is less soluble in cold water, cold ethanol, and insoluble in chloroform, benzene, ether, and petroleum ether. DNAN is somewhat hygroscopic, and moisture slowly decomposes it—should be stored in a desiccator. A small sample bums leaving a residue of carbon when ignited—a small sample can be detonated by the blow of a hammer. DNAN can be used in explosive compositions when alloyed with TNT, or other low melting secondary explosives, gun propellants with nitrocellulose, nitro starch, or nitroglycerine, and rocket propellants when mixed with ammonium perchlorate. DNAN also demonstrates usefulness for priming mixtures with lead azide, lead styphnate, or diazodinitrophenol, and for use in fireworks. ... 

Nitrocellulose is a very good explosive to use as a booster charge, as it is fairly easy to initiate and will reliably detonate almost any secondary explosive. This material is very spark sensitive when dry. 

MC found primarily at impact areas and tiring lines of U.S. military testing and training ranges often consist of mixtures of residues from several MC. These may include the nitroaromatic explosive compounds 2,4,6-trinitrotoluene (TNT), 2,4- and 2,6-dinitro-toluene (DNT), and trinitrophenylmethylnitramine (tetryl) nitrate esters such as nitrocellulose (NC), pentaerythritol tetranitrate (PETN), and nitroglycerin (NG) and the nitramine compounds, hexahydro-l,3,5-trinitro-l,3,5-triazine (RDX) and octahydro-l,3,5,7-tetranitro-l,3,5,7-tetrazocine (HMX). Most of these MC have been in use for decades, either as primary or secondary explosives or in propellant compositions. 

Secondary explosives, those that do not easily go from deflagration to detonation, do not initiate electrostatically with ease, and require larger shocks to detonate. They include nitrocellulose, PETN, and desensitized nitroglycerine. 

Fidlar patented a flashlegs propellent explosive formed of nitrocellulose, starch, and dinitrotoluene. Grotta patented compound detonators with a priming charge formed of mercury fulminate, a heavy-metal azide, and a secondary charge formed of a mixture of equal amounts of Tetryl and potassium chlorate. 

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