Pyrotechnic mixtures

Pyrotechnics is based on the estabflshed principles of thermochemistry and the more general science of thermodynamics. There has been Httle work done on the kinetics of pyrotechnic reactions, largely due to the numerous chemical and nonchemical factors that affect the bum rate of a pyrotechnic mixture. Information on the fundamentals of pyrotechnics have been pubflshed in Russian (1) and English (2—6). Thermochemical data that ate useful in determining the energy outputs anticipated from pyrotechnic mixtures are contained in general chemical handbooks and more specialized pubHcations (7-9). 

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. 

The process of designing a pyrotechnic mixture begins with the selection of oxidizer and fuel, and proceeds to incorporate additional components to achieve the exact pyrotechnic effect and bum rate desired in the end item. It is at this point that pyrotechnics takes on the dual nature of an art and science, and experience is often the only thing that can be reHed upon for the solution of a difficult problem. 

R.H. Martinson, Initiation of Pyrotechnic Mixtures by Shock , Paper No 53, see Ref 154... 

Stability of the Pyrotechnic Mixture Titanium Hydride TiHx/KC104 Report SAND-75-5889... 

Boron and silicon, whether they are on their own or combined, are used with sodium or potassium chromate to make pyrotechnic mixtures. 

A pyrotechnic mixture of sulphide/potassium chlorate/aluminium has led to regular detonations. This sulphide incandesces as soon as it is in contact with chloric acid. Mixtures of antimony trisuiphide with alkaline nitrates, which are probably used for pyrotechnic purposes, also lead to detonations. Bengal lights has been made with this mixture, which was used in small quantities in mixtures and no accidents were experienced. Finally, dichlorine oxide detonates in contact with this sulphide. 

A pyrotechnic mixture of aluminium powder with potassium perchlorate, barium nitrate, potassium nitrate and water exploded after 24 h storage under water. Tests revealed the exothermic interaction of finely divided aluminium with nitrate and water to produce ammonia and aluminium hydroxide. Under the conditions prevailing in the stored mixture, the reaction would be expected to accelerate, finally involving the perchlorate as oxidant and causing ignition of the mixture. 

The mechanism of ignition and combustion of pyrotechnic mixtures of boron with potassium dichromate and/or sodium dichromate in presence or absence of silicon... 

A pyrotechnic mixture containing the powdered ingredients was found dangerously sensitive to frictional initiation and highly explosive. 

A stoicheiometric mixture with sucrose ignites at 159°C, and has been evaluated as a rocket propellant [1], Dry powdered mixtures with glucose containing above 50% of chlorate explode under a hammer-blow [2], Pyrotechnic mixtures with lactose begin to react exothermally at about 200°C, when the lactose melts, and carbon is formed. This is then oxidised by the chlorate at about 340° C. The mechanism was studied by DTA [3],... 

The stability of the pyrotechnic mixture has been studied, including the effect of hydrogen content of the hydride [1]. Presence of moisture and impurities adversely affects stability [2], and remote handling facilities for the mixture have been developed [3],... 

Pyrotechnic mixtures (1 1 wt) attained a maximum temperature of about 1090°C... 

Karlsson N, Cassel G, Fangmark I, et al. 1986. A comparative study of the acute inhalation toxicity of smoke from Ti02-hexaehloroethane and Zn-hexachloroethane pyrotechnic mixtures. Arch Toxicol 59 160-166. 

Karlsson N, Fangmark I, Haggqvist I, et al. 1991. Mutagenicity testing of condensates of smoke from titanium dioxide/hexachloroethane and zinc/hexachloroethane pyrotechnic mixtures. Mutat Res 260 39-46. 

Electric detonators are also used for detonation of high explosive charges. They are similar in design to other types of detonators except for the presence of an electric fusehead consisting of a bridgewire made of chromium and nickel. The bridgewire is covered by a heat-sensitive pyrotechnic mixture protected by varnish insulation. Standard fuseheads have electrical resistance of 1.2 to 1.4 ohms and... 

Uses. Amorphous boron is used as an addictive in pyrotechnic mixtures, solid rockets propellants, explosives, etc. Refractory metal borides are used as addic-tives to cemented carbides. High purity boron is used in electronics as a dopant to... 

With the possible exception of delay fuses, any pyrotechnic mixture represents a hazard worthy of report. Although the cause of frequent accidents reviewed in [2], compositions intended to explode or deflagrate are generally outside the field of this work and few are listed. Numerous reviews and specialist texts exist and hundreds of patents appear yearly. The account [1] of the theory and practice of pyrotechnics contains much useful information on the performance and potential hazards of a great variety of oxidant-fuel combinations which burn very rapidly or explosively. Safety measures are found in [2], Other reviews written from a functional viewpoint are found in [3] and [4], Some hazardously incompatible pyrotechnic mixes are reported [5], Detonability of pyrotechnic compositions has... 

There is some risk of pyrotechnic mixtures containing powders of magnesium, aluminium, their alloy, or zinc, igniting from exothermic reactions of the metal in damp storage. Some study of inhibitors is undertaken. Titanium seems relatively inactive. 

Clearly gunpowder has played a prominent role in the construction of early fireworks but, unless it was used in conjunction with other pyrotechnic mixtures, the range of effects was very limited. However, it continued to be the main performer in fireworks until the introduction... 

The use of pyrotechnic mixtures for military purposes in rifles, rockets, and cannons developed simultaneously with the civilian applications such as fireworks. Progress in both areas followed advances in modern chemistry, as new compounds were isolated and synthesized and became available to the pyrotechnician. Berthollet s discovery of potassium chlorate in the 1780 s resulted in the ability to produce brilliant flame colors using pyrotechnic compositions, and color was added to the effects of sparks, noise, and motion previously available using potassium nitrate-based compositions. Chlorate -containing color-producing formulas were known by the 1830 s in some pyrotechnicians arsenals. 

The element carbon (symbol C) is almost always found in nature covalently bonded to other carbon atoms or to a variety of other elements (most commonly H, O, and N). Due to the presence of carbon-containing compounds in all living things, the chemistry of carbon compounds is known as organic chemistry. Most high explosives are organic compounds. TNT (trinitrotoluene), for example, consists of C, H, N, and O atoms, with a molecular formula of C yH 5N P e. We will encounter other organic compounds in our study of fuels and binders in pyrotechnic mixtures. 

Pyrotechnic mixtures "burn," but it must be remembered that these materials supply their OWTl oj gen for combustion, through the thermal decomposition of an oxygen-rich material such as potassium chlorate... 

Materials that have been used in pyrotechnic mixtures include nitrocellulose, polyvinyl alcohol, stearic acid, hexamethylenetetra mine, kerosene, epoxy resins, and unsaturated polyester resins such as Laminae. The properties of most of these fuels can be... 

Outside container material Performance of a pyrotechnic mixture can be affected to a substantial extent oy the type of material used to contain the mixed composition. If a good thermal conductor, such as a metal, is used, heat may be carried away from the composition through the wall of the container to the surroundings. The thickness... 

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