Explosive

(materials) A substance, such as trinitrotoluene, or a mixture, such as gunpowder, that is characterized by chemical stability but may be made to undergo rapid chemical change without an outside source of oxygen, whereupon it produces a large quantity of energy generally accompanied by the evolution of hot gases.

A substance containing a large amount of stored energy that can be released suddenly, thereby converting the substance into compressed gases or numerous fragments that expand with great force or velocity. An explosion is a sudden expansion of matter into a much larger volume than it formerly occupied, or a sudden increase in the pressure exerted by confined matter.

Uses of industrial explosives include blasting ore, coal, and rock in mining and construction, generating vibrations in seismic prospecting for oil and gas, stimulating and perforating gas and oil wells, bonding sheets of dissimilar metals to each other, and synthesizing industrial diamonds. In contrast to military explosives, industrial explosives tend to have larger critical diameters, lower densities, lower detonation velocities, and lower explosion pressures; and to have more complex compositions and lower cost. Most military explosives are rigid solids, whereas most industrial explosives are formulated to be plastic, pumpable, or free-flowing to permit filling the cross section of deep, rough, and irregular holes in rock.

Industrial explosives usually contain separate fuel and oxidizer ingredients in intimate combination. Usually, they also contain a sensitizer to aid in the initiation and propagation of detonation. Other ingredients may be used to increase or decrease density, to increase explosion energy, to prevent the detonation from igniting methane in coal mines, to provide plasticity, pumpability, or flowability, to prevent setting or stiffening during storage or at low temperature, to prevent separation of ingredients and chemical instability during storage, and to provide resistance to desensitization by water, low temperature, hydrostatic pressure, or transient pressure from explosions in nearby holes. Industrial explosives are usually packaged in bags or cartridges of polymer film or paper, or are carried in bulk form to the blasting site, where they are blown or pumped into the holes through hoses. Sometimes they are mixed at the blasting site.

Most military explosives are simple compositions formulated for high energy density, loading in munitions plant, and long storage life. Most of them are based on explosive chemical compounds that incorporate both oxidizer and fuel components in the same molecule. Many of these compounds are used for special purposes in industrial explosives also.