The explosive power of a compound can be judged using two criteria, the detonation rate, which describes the spread of the shock wave generated, and the physical density of the material, which is a guide to the energy concentration of the material.

One of the most powerful explosives known is hexanitroisowurztitane also known as 'CL20'. This has a detonation rate of 9380 m s-1, and a density of 1.98 g/cm. The shock wave it produces expands through air at 21,000 miles per hour! (The speed of sound is only 675 miles per hour).

HMX, tetramethylene tetranitramine or octagen is the most powerful commercially available explosive and has a detonation rate of 9110 m s-1, with a density of 1.89 g/cm. TNT has a detonation rate of 6930 m s-1 and a density of 1.63 g/cm.

The cheapest explosive, which has 80% of the market share is simply a mixture of diesel oil and ammonium nitrate an is known as ANFO.

An explosive is a material that decomposes rapidly and spontaneously under influence of thermal or mechanical shock. The decomposition reaction involves the release of large amounts of heat and gas.

One of the earliest explosives, black powder (a mixture of charcoal, sulfur and saltpeter) was already known in China many centuries ago for the manufacture of fireworks. Around 1300, black powder was first utilized as a propellant for missiles. There was little development in explosives until around 1850, with the discovery of nitrated compounds such as nitroglycerine and nitrocellulose, followed by the development of dynamite. World War I and World War II triggered the mass production of cheap explosives, while the space race required the development of more powerful, stable, and uniform propellants. Explosives play an important role industrially, especially for mining purposes.

Explosives are classified into three types: mechanical explosives function by means of rapid changes in the thermodynamic state of a compound, atomic explosives function by means of nuclear fusion or fission processes, and chemical explosives function by irreversible chemical decomposition or reaction of a compound.

Chemical explosives have the largest use industrially. These compounds are further classified in:

Various applications require explosives with a wide range of properties, such as brisance, heat value, rate of combustion and detonation, shattering ability and sensitivity. The tests are largely of an empirical nature. The brisance of an explosive is measured in a standardized soft lead test cylinder. The test measures the expansion of the cylinder wall caused by detonation. The sensitivity of an explosive is simply measured by dropping explosive samples from increasing heights until the point where the explosive detonates upon impact. Explosives for industrial are designed to release minimal amounts of toxic gases, and to have minimal environmental impact. Several important explosives listed by field of application are listed below.

Industrial Explosives

Traditionally, black powder has been used as blasting agent, since it does not shatter as much. It consists of saltpeter, sulfur, and charcoal in a 75:15:10 ratio. Since the products contain about 50% solids, it is an undesirable blasting agent when combustible solids or gases are present (e.g. coal mines.)

Nitroglycerin has been an important industrial explosive. It is made by slowly adding glycerol to a mixture of sulfuric acid, nitric acid and water. However, nitroglycerin is a liquid that is not very easy and safe to handle, and therefore it is usually processed into dynamite. This is done by absorbing the nitroglycerin on a solid support material.

Currently, the major industrial explosives are blasting agents and slurry explosives. These are low-cost, safe explosives with high energy content. They often consist of ammonium nitrate/fuel mixtures.

Rocket Propellants

Typically, rocket propellants are low explosives that include their own oxidant or reactant to induce the explosive reaction. Propellants are used for launching missiles and spacecraft. The reaction needs to proceed at high temperature and pressure, and the product gases must be of low molecular weight. The efficiency of a rocket propellant is defined by its specific impulse, which indicates the amount of thrust on a weight basis.

Liquid propellants are usually bipropellant systems: the fuel and the oxidizer are stored in two tanks and fed separately to the combustion chamber. Typical liquid propellant systems are liquid oxygen/liquid hydrogen, liquid fluorine/liquid hydrogen, boroethane (diborane)/oxygen difluoride, liquid oxygen/hydrazine.

Solid propellants are cheap, simple to handle, and easily stored. Typical solid propellants are ammonium chlorate, and nitrocellulose. These propellants are often used for solid rocket boosters

Pyrotechnics

Fireworks and signal flares are made of relatively simple explosives, and include many additives to obtain proper illuminating and coloring effects. A typical explosive of a signal flare consists of barium nitrate (oxidizer), magnesium (heat), aluminum powder (illumination), sodium oxalate (yellow coloring), and calcium stearate, castor oil and linseed oil as binders. Black powder is used as igniter.

Matches

Strike-anywhere matches are made from phosphorous sesquisulfide, and an oxidizing agent such as potassium chlorate or barium chlorate. Safety matches use antimony sulfide instead of the phosphorous sesquisulfide.

Military Explosives

The main focus of military explosives is on performance and good storage life. Environmental and cost factors play a much smaller role in this type of explosive. Some of the more commonly used military explosives are:
Source:
George Austin (ed.) - Shreve's Chemical Process Industries, 5th edition, McGraw Hill.

Common Sense Disclaimer: content of this writeup are for information purposes only. This is general knowledge from chemical text books that are commonly available. Do not attempt to synthesize explosives since this requires very careful control over processing conditions, and is very dangerous.

Ex*plo"sive (?), a. [Cf. F. explosif.]

Driving or bursting out with violence and noise; causing explosion; as, the explosive force of gunpowder.

 

© Webster 1913.


Ex*plo"sive, n.

1.

An explosive agent; a compound or mixture susceptible of a rapid chemical reaction, as gunpowder, or nitro-glycerine.

2.

A sound produced by an explosive impulse of the breath; Phonetics one of consonants p, b, t, d, k, g, which are sounded with a sort of explosive power of voice. [See Guide to Pronunciation, &root; 155-7, 184.]

 

© Webster 1913.

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