Explosives: their classification and characteristics. Pt. 1

Many factors, such as sensitivity, power, and shattering effect, must be considered in evaluating an explosive for a specific application. Equally important are the degree of toxicity of raw materials and intermediates that must be handled during production and use, hygroscopicity, water repellence, stability in storage, and cost of manufacture. As illustrated, explosives are broadly classified as mechanical, chemical or nuclear. In mechanical explosions, inert materials are caused to vaporize very suddenly by the introduction of extremely hot matter. Chemical explosives are of 2 main types: high and low. High explosives are characterized by very high rates of reaction (one to 6 miles per sec) and high pressures (50,000 to 4 million psi). High explosives are subdivided into primary explosives, which are reliably detonated by spark, flame, and impact, and secondary explosives, which require a detonating wave of considerable magnitude for successful initiation. Low (or deflagrating) explosives are characterized by much slower rates of reaction (a few inches or a few feet per second) and much lower pressures (up to 50,000 psi). Nuclear explosives consist of plutonium, uranium-235 or similar materials that are atomically active.