Pyrotechnical compositions

Table 3. Comparison of Pyrotechnic Compositions with High Explosives ...

Pyrotechnic compositions produce only a mild ignition on impact. 

J. C. Cackett, Monograph on Pyrotechnic Compositions, RARDE, Eort Halstead, UK, 1965. 

A pyrotechnic composition contains one or more oxidizers in combination with one or more fuels. Oxidizers used in pyrotechnics, such as potassium nitrate, KNO, are soflds at room temperature and release oxygen when heated to elevated temperatures. The oxygen then combines with the fuel, and heat is generated by the resulting chemical reaction. Chemicals that release fluorine or chlorine on heating, such as polytetrafluoroethylene (Teflon)... 

Pyrotechnic mixtures may also contain additional components that are added to modify the bum rate, enhance the pyrotechnic effect, or serve as a binder to maintain the homogeneity of the blended mixture and provide mechanical strength when the composition is pressed or consoHdated into a tube or other container. These additional components may also function as oxidizers or fuels in the composition, and it can be anticipated that the heat output, bum rate, and ignition sensitivity may all be affected by the addition of another component to a pyrotechnic composition. An example of an additional component is the use of a catalyst, such as iron oxide, to enhance the decomposition rate of ammonium perchlorate. Diatomaceous earth or coarse sawdust may be used to slow up the bum rate of a composition, or magnesium carbonate (an acid neutralizer) may be added to help stabilize mixtures that contain an acid-sensitive component such as potassium chlorate. Binders include such materials as dextrin (partially hydrolyzed starch), various gums, and assorted polymers such as poly(vinyl alcohol), epoxies, and polyesters. Polybutadiene mbber binders are widely used as fuels and binders in the soHd propellant industry. The production of colored flames is enhanced by the presence of chlorine atoms in the pyrotechnic flame, so chlorine donors such as poly(vinyl chloride) or chlorinated mbber are often added to color-producing compositions, where they also serve as fuels. 

Cost is always a factor in selecting a component for a pyrotechnic composition, as is the water-attracting abiHty of a substance (hygroscopicity). In general, substances that attract water from the atmosphere are avoided in pyrotechnic formulations for a variety of reasons, thereby supporting the centuries-old adage, "Keep your powder dry."... 

Wire sparklers are wires coated with pyrotechnic composition which are hand-held and produce a gende spray of gold sparks from iron filings. Fountains are cardboard tubes filled with chemical mixtures that produce a spray of color and sparks extending 2—5 m into the air. Roman candles are cylindrical tubes which repeatedly fire colored stars distances of 5—20 m into the air. These items typically contain 5—12 stars. 

The air bag industry has become one of the principal users of pyrotechnic compositions in the world. Most of the current air bag systems are based on the thermal decomposition of sodium azide, NaN, to rapidly generate a large volume of nitrogen gas, N2. Air bag systems must function immediately (within 50 ms) upon impact, and must quickly deploy a pulse of reasonably cool, nontoxic, unreactive gas to inflate the protective cushion for the driver or passenger. These formulations incorporate an oxidizer such as iron oxide to convert the atomic sodium that initially forms into sodium oxide, Na20. Equation 1 represents the reaction. 

A water-soluble white crystalline sofld, CS is disseminated as a spray, as a cloud of dust or powder, or as an aerosol generated thermally from pyrotechnic compositions. The formulation designated CSl is CS mixed with an anti-agglomerant when dusted on the ground, it may remain active for as long as five days. CS2 formulated from CSl and a siUcone water repellent, may persist for as long as 45 days (6). 

Anon, EngrDesHdbk, Properties of Materials Used in Pyrotechnic Compositions , AMCP 706-187 (Oct, 1963), 173... 

H.J. Eppig, Stability of Pyrotechnic Compositions Employed in the AN-M53 to M58 Aircraft Signals , PATR 1588 (1946)... 

The US Dept of Defense Mil Spec for K nitrate is MIL-P-156B (18 April 1956) with Amendment 1 (31 July 1974). Three classes are specified Class 1 - for use in black powder and chemical munitions Class 2 - for use in pyrotechnic compositions and Class 3 — for use in propellants. The chemical requirements for these classes are given below ... 

Pyrotechnic Composition For Amber Colored Signal , PATR 596 (1935) 6) Ibid, Modifi-... 

Nichols, Modification of M-8 Flare Composition to Increase Candiepower , PATR 841 (lio /) oj a. atiasser, otuay or use or oj /o Grade of Sodium Oxalate in Pyrotechnic Compositions , PATR 1161 (1942) 9) H.J. Eppig,... 

EngrDesHndbk, Military Pyrotechnics Series, Part Three, Properties of Materials Used in Pyrotechnic Compositions , AMCP 706-187 (1963) 6) Ellem (1968), 136ff 7) R. Lancaster, T. Shimizu, R.E.A. Butler R.G. Hall, Fireworks, Principles and Practice , Chemical Publishing Co, NY (1972), 49... 

Ed, Handbook of Preparative Inorganic Chemistry , Vol 1, Academic Press, NY (1963), 975-6 3) Anon, EngDesHdbk, Properties of Materials Used in Pyrotechnic Compositions , AMCP 705-187, (Oct 1963), 276-8 4) Merck (1968),... 

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