Commercial explosives compositions

Both 1,3-DNB and 1,3,5-TNB have been used for their explosive properties (HSDB 1994). 1,3-DNB has been suggested as a possible substitute for the explosive TNT (HSDB 1994). 1,3-DNB has been used as a camphor substitute in nitrocellulose, a compound used in explosive and propellants (HSDB 1994 Sax and Lewis 1987). 1,3-DNB was manufactured during both world wars as a component in the explosive roburite (ERA 1976). 1,3,5-TNB has been classified as a high explosive and has been used in military and commercial explosive compositions (Merck 1989 Sax and Lewis 1987). A more powerful explosive than TNT, 1,3,5-TNB is less sensitive than TNT to impact (Merck 1989). 1,3,5-TNB has also been used as an explosive for oil wells and mining operations (OHM/TADS 1991). 

Some typical compositions of commercial explosives are given in Table 5.1. 

TABLE 5.1 Compositions ofNon-permitted Commercial Explosives... 

Before nitrates and particularly ammonium nitrate were readily available commercially, explosives were developed based on chlorates and perchlorates. These also are still used in some countries. In general perchlorates are considered less dangerous than chlorates and therefore preferred. They are easily sensitised, so that in addition to explosives of this type based on nitroglycerine, others have been based on various organic liquids, particularly nitrobodies. History shows that chlorates and perchlorates must be regarded as temperamental substances, liable in bulk to lead to inexplicable accidents. Particularly when mixtures of chlorates and oxidising materials are allowed to become wet and then dry out, conditions can arise in which there is an appreciable sensitiveness to friction and impact. Explosives of this type have an unfortunate record of accidents. They are used, therefore, to a limited extent only, now that safer compositions are available. 

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. 

PETN was first prepared in 1894 by nitration of pentaerythritol. Commercial production of PETN could not be achieved until formaldehyde and acetaldehyde required in the synthesis of pentaerythritol became readily available about a decade before World War II. During World War II, RDX was utilized more than PETN because PETN was more sensitive to impact and its chemical stability was poor. Explosive compositions containing 50% PETN and 50% TNT were developed and called Pentrolit or Pentolite . This composition was used for filling hand and anti-tank grenades, and detonators. 

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. 

There are many other ingredients that are added to explosive compositions which in themselves are not explosive but can enhance the power of explosives, reduce the sensitivity, and aid processing. Aluminium powder is frequently added to explosive and propellant compositions to improve their efficiency. Ammonium nitrate (NH4N03) is used extensively in commercial explosives and propellants. It is the most important raw material in the manufacture of commercial explosives and it also provides oxygen in rocket propellant compositions. Some of the properties of ammonium nitrate are presented in Table 2.22. 

Nitrocellulose can be quite hazardous if left to dry out completely therefore, it is usually stored and transported in 30% water or ethanol. Nitrocellulose is often dissolved in solvents to form a gel. For example, commercial explosives used for blasting purposes contain nitrocellulose dissolved in nitroglycerine, and some gun propellant compositions contain nitrocellulose dissolved in a mixture of acetone and water. 

Ammonium nitrate prills are often mixed with fuel oil (liquid hydrocarbons) to produce a commercial explosive mixture known as ANFO which is used in quarrying. ANFO can be prepared in a factory by mixing both ingredients in a rotating container and dispensing the product into polyethylene or cardboard tubes. The tubes are then sealed and transported to the place of use. ANFO can also be prepared at the site where the explosive composition is to be used. Fuel oil is poured into a polyethylene bag containing ammonium nitrate and left for some time to allow the oil to soak into the ammonium nitrate. The ANFO mixture is then poured from the polyethylene bag into the hole (i.e. shot-hole) where the explosive mixture is detonated. 

German Commercial Explosives of Nonpermis sible Type (Gesteinsprengstoffe in Ger), used before and during WWII, are listed in Ref 53, PP Ger 29ff Ger 69 and under individual compositions... 

Aromatic nitro compounds are generally stable but are frequently reactive, especially if they contain groups other than nitro groups in the meta position with respect to one another. As a class they constitute the most important of the military high explosives. They are also used as components of smokeless powder, in compound detonators, and in primer compositions. Liquid nitro compounds, and the mixtures which are produced as by-products from the manufacture of pure nitro compounds for military purposes, are used in non-freezing dynamite and other commercial explosives. The polynitro compounds are solvents for nitrocellulose. 

Commercial Solvents Corp Method of Making Nitrocellulose- Nitroglycerin Water-Bearing Explosives Compositions... 

Commercial Solvents Corporation Thickened Aqueous Inorganic Nitrate Salt-Nitroparaffin Explosive Composition Sensitized with an Air Entrapping Material... 

Commercial Solvents Corporation Ceiled Ammonium Nitrate—Nitromethane— Nitropropane Explosive Composition... 

Of these only the 2,4-isomer is used in explosive compositions or as a starting material for the preparation of picric acid by one of the methods described later. The 2,6-isomer on nitration also gives picric acid but it is not used for this purpose on a commercial scale. Both these isomers may be obtained by the nitration of phenol with nitric acid. All the other isomers are prepared by indirect methods. 

A similar test has been developed in the USA (according the deformation of a lead block, using commercial caps with 0.4-0.45 g PETN). It is advisable to classify according to test results and not, as was the custom in the USA, by the classification of NCN according to the explosive composition. As indicated above, ANFO s are not cap sensitive mixtures of finely ground ammonium nitrate containing only 2% instead of 6% of oil or wax can, however, be cap sensitive. 

The most favorable composition for an explosive can be easily calculated from the oxygen values of its components. Commercial explosives must have an oxygen balance close to zero in order to minimize the amount of toxic gases, particularly carbon monoxide, and nitrous gases, which are evolved in the fumes. 

Safety measures to avoid ignition of firedamp uses salt (NaCI) which is included in the usual compositions of commercial explosives. It lowers the -> Explosion Temperature and shortens the detonation flame. Higher safety grades are achieved in ionexchange explosives in which the ammonium and sodium (or potassium) ions are exchanged instead of... 

Even though secondary explosives have a high degree of stability, they are still most often mixed with inert fillers such as plasticizers, dry powders, polymers and/or other ingredients to form what are called explosive compositions . Such compositions include Comp B, C3, C4, and PBX. These compositions have even more stability and are used in military operations, and commercial demolition operations. 

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