(4) Squibs. Squibs for military use are caused to function by heat developed by an electrical resistance wire. This may ignite a charge of either potassium nitrate or sodium nitrate black powder, or an ignition composition, and, in turn, the main charge of black powder. In some cases, the black powder charge is ignited by a matchhead composition.
d. Precautions. Black powder, which is very sensitive to friction, heat and impact, is one of the most dangerous explosives to handle. It will deteriorate rapidly on absorption of moisture but retains its explosive properties indefinitely if kept dry. Black powder may be desensitized by placing it in water. Discarding the water separately from the residue, however, permits wet black powder to dry out and regain some of its explosive properties. Combustible materials which have absorbed liquids leached from black powder constitute a severe fire hazard and may become explosive.
2-13. Black Powder Substitutes a. Benite. Benite is used in igniter compositions of artillery primers or in base igniter bags for separate-loading ammunition. Benite takes the form of extruded strands of black powder (KNO3, charcoal, sulfur) embedded in nitrocellulose.
b. Eimite. Eimite is another substitute for black powder in artillery primers. When used in initiating type elements, delays and similar components, eimite takes the form of solid granulation.
c. Boron-Potassium Nitrate. Boron-potassium nitrate is used in many ignition applications. As an igniter composition, it is used in granular form, or as pellets. Its function in a delay element is to ignite and set off the rest of the explosive train at a predetermined time.
d. Mox-Type Mixtures. Mox-type mixtures are filler explosives, not igniter materials. Although classified as explosives, these mixtures are used for specialized applications. The most common mixture, MOX 2B, is used as a spotting charge in place of black powder. Unlike other filler explosives, MOX 2B was developed commercially.
2-14. Pyrotechnic Compositions a. General. Standard military pyrotechnic compositions consist of such compounds as perchlorates and nitrates to provide oxygen; powdered metals for fuel; salts of sodium, barium or strontium for ccqor; and binding and waterproofing materials. These compositions are sensitive to heat, flame, static electricity discharges and, particularly, to friction. Those containing chlorates are especially hazardous as regards to fires and explosions. Because they contain powdered metals, pyrotechnic compositions may become hazardous in the presence of moisture.
b. Main Charge Pyrotechnic Compositions.
(1) The earliest pyrotechnic compositions consisted of varying constituents of black powder: charcoal, sulfur and niter (potassium or sodium nitrate). Other materials, such as iron filings, coarse charcoal or realgar (arsenic sulfide), were added to produce special effects. Many other materials were added or substituted as additional knowledge was acquired.
(2) Present-day pyrotechnic compositions generally consist of various chemicals. In some cases, a single material may perform more than one of the functions in (a) through (f) below.
(a) Oxidizers, such as chlorates, perchlorates, peroxides, chromates and nitrates, provide oxygen for burning. Additional oxygen may be obtained from the air. Nongaseous powders, such as barium chromate-boron mixtures, which do not require oxygen from the air, are used in delay columns.
(b) Fuels, such as aluminum and magnesium powder, their alloys, sulfur, lactose and other easily oxidizable materials.
(c) Combustible binding and waterproofing agents, such as shellac, linseed oil, resins, resinates and paraffin.
(d) Color intensifiers, such as polyvinyl chloride, hexachlorobenzene or other organic chlorides, mixed with barium and copper salts to produce green, or with strontium salts to produce red.
(e) Dyes, such as methylaminoanthraquinone to produce red, and auramine to produce yellow.
(f) Coolants, such as magnesium carbonate and sodium bicarbonate.
(3) Pyrotechnic smoke compositions are of two general types:
(a) Those that burn with practically no flame but give off a dense, colored smoke as a combustion product.
(b) Those that burn at a temperature so low that an organic dye ((2)(e), above) in the composition will volatilize instead of burn and, therefore, color the smoke.
(4) A friction igniter consists of a primer cup and a ripple wire. The primer cup contains a mixture of potassium chlorate, charcoal and dextrin binder. The ripple wire is coated with red phosphorus in shellac and has a nitrocellulose coating. The wire extends through the primer cup.
(5) Quickmatch is a term applied to strands of cotton soaked in a mixture of black powder and gum Arabic and coated with mealed powder. It is used as an initiator to transmit flame to igniting, priming or pyrotechnic charges.
(6) The priming charge is a dried black powder paste in intimate contact with the firstfire composition. Newer pyrotechnic items use a special nonhygroscopic priming paste containing barium nitrate, zirconium hydride, silicon, tetranitrocarbazole and a plastic binder.
(7) The first-fire composition is generally a mechanical mixture of illuminant charge and black powder. However, for certain items, it may be a special nonhygroscopic, easily ignitable composition that burns with a higher temperature.
c. Characteristics. Pyrotechnic compositions are generally compressed into definite shapes or forms. On ignition and combustion, these compositions produce considerable light and decompose or burn by a process known as deflagration. Functional characteristics of pyrotechnic compositions include candlepower, burning rate, color, color value and efficiency of light production. Other important characteristics are sensitivity to impact and friction, ignitibility, stability and water absorption. Table 2-1 shows burning performance characteristics of black powder, nitrocellulose composition and pyrotechnic compositions.
d. Uses. Pyrotechnic compositions are used in items of ammunition to produce, through chemical reaction, a desired effect or combination of effects, such as light (instantaneous or continuous), smoke, heat, noise, delay timing and gas pressure. These items are used for such purposes as signaling, illumination, simulation of battlefield effects, warning, marking, tracking, screening, igniting, and incendiary effects. Pyrotechnic items produce their effect by burning and are consumed in the process. The effect produced generally falls into one of the following pyrotechnic classes:
(1) Photoflash cartridges. These produce a single flash of light for photographic purposes.
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