Pronunciation key
( iks-plō′siv )
( ik-splō′siv ) |
ex•plo•sive
adj.
- Pertaining to, having the nature of or causing an explosion.
- Tendency to explode, tendency to burst forth violently.
n.
- A prepared chemical substance that explodes.
- Phonetics. A stop. Pronounced with a sudden release of breath.
A substance or mixture of substances whose chemical composition is designed upon particular stimulation such as detonation to burst with extreme violence, rapidly transforming from a solid or liquid into hot, expanding gas, undergoing a rapid chemical decomposition when acted upon by heat, percussion or by another form of detonation and formation of more stable products. When exploded, the solids and liquids are chemically altered to become and rapidly evolve large quantities of energy in the form of heat and gas at much greater volume than the original explosive. The energy of the expanding gases may be used for various industrial purposes such as mining, excavating, building and engineering construction. Because these gases are hot, they exert tremendous expansive force, or explosion. Hot gas expands rapidly and violently, because they need more space than the chemicals did in their natural state. (See expansion).
Products of the decomposition of explosives are usually gases, such as with nitroglycerin and in some situations gases and solids as is the case with lead azide. Some explosives such as copper acetylide produce only solid by products. Gaseous explosion products typically have much greater volume than that of the explosive itself. Explosions also create a great deal of heat which inadvertently expands the explosive material as well as the surrounding air. The result is a rapid production of heavy gas pressure which can potentially accomplish tasks if manipulated in some manner such as in rock and blast holes. The amount of heat that is produced during the explosion is a major factor in how much work can be accomplished with it. A pressure wave of considerable force that strikes surrounding objects during the explosion. The chemical reaction during rapid chemical decomposition include oxidation of carbon, hydrogen and other easily oxidized elements. All the oxygen that is necessary for this reaction is contained within the material itself. Some explosives decompose without need for an oxidation reaction. One such example is lead azide.
Expansion of molecular and sub-molecular particles subjected to heat.
There are many substances and chemical mixtures capable of exploding, but only those used commonly for commercial and military purposes, specifically for their explosive properties are called explosives. For information on other explosive compounds and mixtures, see EXPLOSION. Explosives are often utilized in civilian and military tasks; in mining, where a trained professional tunnels through mountains, obstacle clearing such as clearing stumps off land, in waterways to remove rock from waterways for ships, open mines or sending out lifelines for shipwreck victims. During wartime, explosives are used by military expeditions to destroy cities, the sinking of ships, and killing the enemy. Explosives are also used as propellants for firearms and rockets, bursting charges for bombs, mines (including production of diamond dust from graphite), artillery projectiles, torpedoes and grenades, general engineering and demolition projects. Small-scale explosives have a vast array of use in industrial settings such as metallurgy, in which metals are pressed into dies, extruded or welded together by means of explosions. The creation of new metal alloys have been designed using such processes.
The chemical makeup of almost all valuable explosives contain elements that include carbon, hydrogen, oxygen and nitrogen. The gases which are typically formed from an explosion are carbon dioxide, steam, nitrogen and some carbon monoxide and hydrogen.
Many substances can be explosive; gasoline vapor, hydrogen and finely dispersed granules of grain or coal are all explosive but only those substances which are specifically designated to produce an explosion are generally labeled as explosives. These are divided into two types.
Image credit: Hercules Powder Co.
An explosives engineer inserts a detonating fuse into a fifty lb. cartridge of semi-gelatin dynamite mixture. The cartridges will be placed in a quarry in blast holes.
- Propellant Explosives
The propellant used to drive shells, or bullets out of a gun must be a low explosive because if the energy that evolves too rapidly it would destroy the gun. Gunpowder, developed by the Chinese in the 10th century, and later independently by the Arabs, was the first explosive to be used in firearms although Greek fire, a prototype of gunpowder, was first used as a liquid flame in a 7th century naval battle. Black powder consisted of sulfur, saltpeter and carbon. Old-fashioned gunpowder was retired from use because solid compounds of potassium were left behind in the barrel and had to be cleaned out. Also, in military it was undesirable because the smoke and bright flash gave away one's position to the enemy. In 1838, a nitrocellulose explosive called Guncotten was developed but proved far too potent for its intended purpose as a firearms propellant. Nitrocellulose (made by treating purified cotton with nitric acid) by itself is an absorbent material. [(In 1847, nitroglycerin was introduced. Both are relatively dangerous but Alfred Nobel (1833-1896), founder of the Nobel Prizes discovered means to make them safer. By using this solution to absorb nitroglycerin Nobel made blasting gelatin, a powerful high explosive which is still safer to use than either material it is derived from.) See High Explosives.] Innovations in the 1880's, mainly by Nobel, resulted in smokeless powders which supplanted black powder as a propellant. Smokeless powders may be derived from nitrocellulose or nitroglycerin, perhaps both, and are compounded in such a way that their rate of reaction place them in the low explosive class. They are made into carefully designed size and shape grains, that they may deliver the necessary energy at a proper rate and complete the reaction before the projectile exits the muzzle, preventing the telltale flash. Innovations on propellents have been developed for reasons other than warfare, such as the space age, devising certain rocket propellants.
- Detonating Explosives
Detonating explosives are subdivided into initiating and high explosives. Initiating explosives must be handled with great care and are the most sensitive. Materials such as mercury fulminate and lead azide explode when detonated by a slight percussion, ignited or burned making them valuable in smaller quantity for use in blasting caps for larger charges or safer explosives.
High explosives are the less sensitive of the two and can be flammable without producing an actual explosion. They can only detonate with severe shock that is delivered by another explosive device located nearby. Therefore, for the most part it is possible to move and handle these substances relatively safe.
In 1846-1847, Italian Ascanio Soberro invented Nitroglycerin. It was so sensitive that it was deemed virtually unusable. Later on however, it became quite important after the Swedish inventor Alfred Nobel combined it with siliceous earth called kieselguhr (a highly absorbant type of natural earth), and wood pulp to create dynamite. Nitroglycerin is a liquid.
TNT (trinitrotoluene) was first used in the early 20th century and became the standard which all explosives are measured by. TNT still possesses a specifal significance among explosives. It has replaced picric acid (trinitrophenol) which was used during World War I. It is used by itself or mixed with other ingredient to produce various subtypes with varying degrees of characteristic performance.
Permissible explosives as was classified by the U.S. Bureau of Mines were explosive substances permitted for use in coal mines where a risk always presents the danger of igniting a mixture of coal dust and air. One unusual type of industrial explosive is LOX. It is produced by soaking carbon black with liquid oxygen. A prepared cartridge can be exploded either electrically or by using a fuse. A fuse typically is a combustible cord which smolders at a constant rate. However, if the fuse should fail and the oxygen has evaporated, the cartridge is rendered entirely safe.
Image credit: E.I. Dupont De Nemours & Co.
A critical step in producing dynamite is the initial production of nitroglycerin, with the provision of soaking this highly sensitive ingredient with water, when necessary. By comparison, the weighing and adding of ammonium nitrate, make it relatively safe due to its characteristic properties of low sensitivity and stability.
Image credit: E.I. Dupont De Nemours & Co.
There are two distinct types of explosives. Materials belonging to the type called "low explosives" undergo rapid combustion or deflagration. Combustion travels through these substances at rates up to about 400 meters per second. High explosives undergo detonation, a type of chemical decomposition that is nearly instantaneous and rates can range anywhere from about 1000 to 8500 meters per second.
- High Explosives
- Low Explosives
High Explosives: High explosives undergo detonation, a type of chemical decomposition that is almost instantaneous. The reaction travels through these at an extremely high rate, somewhere in the range of 1000-8500 meters per second. These substances change from solids, liquids and gases in a matter of split seconds. The rate of detonation or speed at which the explosion travels through the materials may be as high as 4 miles per second. (Or six kilometers). Some of those which are classed among High Explosives include nitroglycerin, PETN, RDX, TNT, and a combination of TNT and PETN commonly called pentolite. Those which are especially sensitive to hot temperatures which render them unstable, are called primary explosives. These are used in designing devices called detonators, and are utilized in setting off the detonation of less sensitive explosive material. These materials are used industrially for demolition and in military use, for shells, bombs, mines, depth charges and similar devices. This class of explosive is based upon the ease in which they can be detonated. Some are sensitive enough to be exploded by simply heat or an impact and are initiating explosives due to the fact that they are often used to set off less sensitive explosive substances. The remaining high explosives, those considered to be too insensitive to be classed among initiating substances are known as non-initiating high explosives.
Often TNT is mixed with another explosive to produce a binary explosive, such as Amatol with ammonium nitrate and Cyclotol and Cyclonite. These are melted and poured into the shell. Tritonal contains TNT and flake aluminum and is used in bombs. Cyclonite, also called RDX was used during World War II and prepared into a plastic mass to make demolition work convenient.
Such classifications are never exclusive, 100% of the time. Nitrocellulose and some alternative substances can undergo either the deflagration reaction that is characteristic of low explosives or detonated, which is characteristic of high explosives.
It is noteworthy to add that many explosives include the prefix "nitro" or "nitrate" in their name. The N in PETN stands for nitrate. Nearly all explosives in discussion, except LOX, contain nitrogen in combination with other elements as many of the compounds of nitrogen are readily decomposed, releasing a substantial volume of energy. Many explosives are designed with the action of nitric acid on some other material. Glycerin for nitroglycerin, toluene for trinitrotoluene, and so forth. Naturally, this is a dangerous operation and creates hazardous working conditions which must be carefully controlled. Manufacture of explosives are usually carried out in small, widely scattered structures.
Annual consumption of industrial explosive materials are measured in tons. Military consumption, especially during wartime is tremendous. In such a case, it is important to obtain sufficient quantity of raw materials. TNT formerly was derived from coal tar, but now can be obtained from petroleum.
Image credit: E.I. Dupont De Nemours & Co.
High explosives proving their value as time saving with large-scale excavations. This picture features dynamite carefully tamped into place with a wood stick to prevent sparks.
See Initial Detonating Agents, Non-Initiating High Explosives, High-Explosive Compositions, Liquid-Oxygen Blasting Explosives.
Low Explosives: Used as propellent charges in firearms as priming compositions for igniting propellants and detonating agent as well as blasting materials. These substances possess a lower rate for detonation. One substance is gunpowder. Its explosion rate travels at about 3-300 ft per second but depends on other factors such as the pressure that surrounds the explosive. In actuality, it is more of a rapid burning. This combustion creates waves of pressure called shock waves that if becoming intense, can increase the rate of detonation. Low explosives are sub-divided into their compositions and purpose for which they are used.
Gunpowder is a mixture of seven to eight parts of potassium nitrate (saltpeter) one to two parts of charcoal, and one part sulphur. Gunpowder was invented centuries ago, by the Chinese. Today it is used primarily for fireworks. A composition quite similar to gunpowder was described by Roger Bacon (1214?-1294) and firearms were used in 14th century Europe. "Black powder" was the only explosive known until the latter 19th century. Military use of black powder are confined to saluting charges and black blasting powder (prepared with sodium nitrate vs. potassium nitrate) is still used in coal mining.
Black powder is classed among low explosives because the rate at which the explosive reaction travels in it is never more than about 1200 ft. per second. High explosives in contrast travel anywhere in the range of 3000 to 20,000+ ft. per second. Some explosive substances characteristically can behave as either a low or high explosive.
Modern detonating explosive devices include PETN (pentaerythrite tetranitrate) that is used in blasting caps and a detonating cord; RDX (known as cyclonite) is combined with other substances that are volatile and waxes that are called plastic explosives; ammonium nitrate, which is of low detonation velocity, used when a slow push or heave is preferred over a shattering effect. Amatol, a mixture of ammonium nitrite and TNT which is used as a bursting charge. Ammonium nitrate is a constituent of many military high explosive compositions. Other explosives include Tetryl.
See also acetylene handling dangers, aftershocks of nuclear explosion, ballistic explosive projectile design, black powder, blasting cap, chemical industry's nitrogen production, dynamite, dynamite use in tunneling, explosion and detonation theories, gunnery technology, gunpowder development, gunpowder in history of ammunition, gun propellant detonation, lead detonator production, mercury fulminate synthesis, nitrocellulose, military engineering history, mining explosives technology, missile warhead armament, nitroglycerin,nuclear fission bombs and energy, PETN, picric acid, piezoelectric grenade detonation, primer, Priming Compositions rare-earth ignition cautions, RDX, river-ice thawing by blasting, safe-cracking use, smokeless powders, technical development in the 1900's, trinitrotoluene, tunneling methods and equipment.
References
Webster's New World Dictionary of the American Language (College Edition) ©1955
The New World Family Encyclopedia ©1955
The American Peoples Encyclopedia ©1960
Encyclopedia International ©1966 (Grolier Inc.)
The World Book Encyclopedia ©1981
Encyclopedia Britannica Micropedia ©1984
The American Heritage Dictionary, Second College Edition ©1985
Grolier Encyclopedia of Knowledge ©1991
Related Terms
explode
explosion
Further Reading
Hercules Powder Company, Commencing operations in 1881, the principal activity at the Hercules powder works was the manufacture of dynamite and later black powder and TNT.
Alcohol, Tobacco and Firearms Federal Website
Chemistry of Explosive Powders
Explosive (Definition) Business Dictionary
Explosive (Definition)
Explosive (Definition
Explosive (Definition)
Intermittent Explosive Disorder
Explosive Thesaurus
Explosive (Definition)
