Secondary explosives explosive power

Primary explosives differ from secondary explosives in that they undergo a rapid transition from burning to detonation and have the ability to transmit the detonation to less sensitive (but more powerful) secondary explosives. Primary explosives have high degrees of sensitivity to initiation through shock, friction, electric spark, or high temperature, and explode whether confined or unconfined. Some widely used primary explosives include lead azide, silver azide, tetrazene, lead styphnate, mercury fulminate, and diazodinitrophenol. Nuclear weapon applications normally limit the use of primary explosives to lead azide and lead styphnate. 

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. 

Explosives are classed as primary or secondary. Typically, a small quantity of a primary explosive would be used in a detonator (known colloquially as a cap ), whereas larger quantities of secondary explosives are used in the booster and the main charge of a device. This collection of explosives is known as an explosive train in which a signal (mechanical, thermal, or electrical) from the control system is converted first into a small explosive shock from the detonator, which in turn initiates a more powerful explosion in the booster, which amplifies the shock into the main charge. 

Nitric acid-acetic anhydride reagent has been used to synthesize N,N -Amitro-N,N -ethylenebisacetamide (58) from A, A -ethylenebisacetamide (57) the former is a secondary high explosive and a precursor to the powerful explosive ethylenedinitramine (Section 5.10). It is interesting to note that (58) is not formed when (57) is treated with nitric acid alone or with strong mixed acid. 

Values of power index for some primary and secondary explosives are given in the Table 1.7 which shows that the values for power index of secondary explosives are more than the values for primary explosives. 

Tablel.7 Power index values of some primary and secondary explosives (standard-picric acid).

The manufacturing process of BX4 was found to be more favorable than that of BX3. The detonation pressure and test of their ability to initiate a secondary explosive have shown that BX4 is the most powerful of these formulations and therefore, it is considered the most promising booster formulation. Another attribute of BX4 is that it could be converted into a blast formulation by the addition of aluminum powder and this modified formulation may find application as a main-charge blast formulation. 

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. 

Table 5.14 The power index of some primary and secondary explosive substances taking picric acid as the standard...

This book outlines the basic principles needed to understand the mechanism of explosions by chemical explosives. The history, theory and chemical types of explosives are introduced, providing the reader with information on the physical parameters of primary and secondary explosives. Thermodynamics, enthalpy, free energy and gas equations are covered together with examples of calculations, leading to the power and temperature of explosions. A very brief introduction to propellants and pyrotechnics is given, more information on these types of explosives should be found from other sources. This second edition introduces the subject of Insensitive Munitions (IM) and the concept of explosive waste recovery. Developments in explosive crystals and formulations have also been updated. This book is aimed primarily at A level students and new graduates who have not previously studied explosive materials, but it should prove useful to others as well. I hope that the more experienced chemist in the explosives industry looking for concise information on the subject will also find this book useful. 

While Region II can be compared with the hot-wire initiation of primary explosives or pyrotechnic compositions, the laser power densities in region IV also make it possible to directly shock initiate secondary explosives by laser irradiation. The laser power densities of Region IV are achieved by solid-state lasers with laser powers of at least 100 W. In contrast, laser diodes ( 1-10 W) only provide power densities which fall into the regions II and III. However, more powerful laser diodes have been gradually developed and therefore, laser diode initiators (LDI) have be-... 

TNN, which is actually a mixture of 3 isomers (as described above), is a yellowish to light yellowish solid with a melting point ranging from 190 to 215 Celsius (depending on purity). The solid is very stable, and can be melted and alloyed with many other secondary explosives to form thermally stable explosives compositions with a high resistance to shock, friction, heat, and percussion. TNN is freely soluble in chloroform, ether, and carbon disulfide, and is moderately soluble in alcohol, but insoluble in water. TNN is not used in military explosives to an amount that would warrant extreme importance for its existence however, TNN is rather inexpensive to make, and is readily available during times of war. It can be used for filling shells, bombs, and warheads, and has satisfactory power. ... 

There is little information readily available on lead picrate. However, it is a workable primary explosive. This material is not very powerful and should always be used with a booster charge of an easily detonated secondary explosive. Like all primary explosives, this material is very sensitive to impact, friction, and sparks. 

Mercury fulminate detonators were widely replaced due to their extreme sensitivity. Contemporary simple nonelectric detonators contain a small quantity of primary explosive (often lead azide) which, once ignited by a fuse, ignites the more powerful base charge of a secondary explosive (an additional low explosive may be used between the fuse and the primary explosive). 

Ramaswamy, A. L. Mukundan, T. Chaudhri, M. M. Amine sensitization studies of secondary explosives nsing laser-indnced ignition. J. Propulsion Power 2001,17, 163-168. 

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