Some pyrotechnic compositions are used in industry and aerospace for generation of large volumes of gas in gas generators (e.g. in airbags), in pyrotechnic fasteners, and in other similar applications. They are also used in military pyrotechnics, when production of large amount of noise, light, or infrared radiation is required; eg. missile decoy flares, flash powders, and stun grenades. A new class of reactive material compositions is now under investigation by military.
Many pyrotechnic compositions - especially involving aluminium and perchlorates - are often highly sensitive to friction, impact, and static electricity. Even as little as 0.1-10 millijoules spark can set off certain mixtures.
When metallic fuels are used, the metal particle size is important. A larger surface area to volume ratio leads to a faster reaction; this means that smaller particle sizes produce a faster-burning composition. The shape also matters. Spherical particles, like those produced by atomizing molten metal, are undesirable. Thin and flat particles, like those produced by milling metal foil, are ideal.
A suitable metal fuel may be dangerous on its own, even before it is mixed with an oxidizer. Careful handling is required to avoid the production of pyrophoric metal powders.
Oxidizers in use include:
Corresponding sodium salts can be substituted for potassium ones.
Colorants, sometimes in combination with sources of chlorine. Usually salts of suitable metals, often barium, strontium, calcium, sodium, copper, etc. The salt may simultaneously serve as an oxidizer.
Chlorine donors. Presence of chlorides increases the volatility of the color-imparting metals and enhances the color intensity. Polyvinyl chloride, polyvinylidene chloride, chlorinated paraffins, chlorinated rubber (e.g. Parlon), hexachloroethane, hexachlorobenzene, and some other organochlorides and inorganic chlorides (e.g. ammonium chloride, mercurous chloride) are used as chlorine donors. Perchlorates and chlorates play this role together with their main use as oxidizers. Chlorine donors are often used also in smoke compositions, e.g. hexachloroethane together with zinc oxide to produce smoke based on zinc chloride.
Catalysts. Propellant formulas often require a catalyst to burn faster and more stable. Certain oxidizers often serve as catalysts. E.g. ammonium dichromate is used as a catalyst in ammonium nitrate based propellant formulas. Other catalysts are e.g. iron(III) oxide, manganese dioxide, potassium dichromate, copper chromite.
Stabilizers. Some mixtures, eg. containing chlorates, tend to degrade and create acidic byproducts. Carbonates (eg. sodium, calcium, or barium carbonate) or other mildly alkaline materials can be added to scavenge such acids. Boric acid can be used to inhibit the sensitivity of aluminium to moisture, and to stabilize mixtures of metals with nitrates (which can otherwise form amides which react exothermically with metals and can cause spontaneous initiation). Many organic nitrated amines are used as stabilizers as well, e.g. 2-nitrodiphenylamine. Petroleum jelly, castor oil, linseed oil, etc. can be used as stabilizers, also to add hydrophobicity to particles and protect metals (especially iron and magnesium) from corrosion.
Binders. Often gums and resins, e.g. gum arabic, red gum, guar gum, copal, carboxymethyl cellulose, nitrocellulose, rice starch, cornstarch, shellac, dextrin. Binders can also serve as fuels. Camphor can be used as a plasticizer. Binders are used in manufacture of compact compositions, e.g. pyrotechnic stars. Polymers like HTPB and PBAN are often used for rocket fuels. Other polymers used are e.g. polyethylene or polyvinyl chloride can be encountered as well.
Publication No. WO/2009/102464 Published on Aug. 20, Assigned to Shocksystem for Detonative Cleaning Apparatus Mounting System (American Inventors)
Aug 24, 2009; GENEVA, Aug. 24 -- Raymond N. Henderson and Kirk R. Lupkes, both of the U.S., have developed a detonative cleaning...
Publication No. WO/2009/137771 Published on Nov. 12, Assigned to SHOCKSYSTEM for Detonative Cleaning Apparatus (American Inventor)
Nov 17, 2009; GENEVA, Nov. 18 -- Kirk R. Lupkes, United States of America, has developed a detonative cleaning apparatus. The patent has...