Pyrotechnic effects

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. 

The fireworks industry also benefited from these improvements, which was reflected in the growing popularity of organised displays and the diversity of the pyrotechnic effects so presented. 

In a simplifled form, the firework rocket trajectory can be discussed in terms of basic equations of motion, simplifled even further by the fact that the rocket rises in the air for a few seconds after which the flight is prematurely terminated when the pyrotechnic effects are released. 

Also, for a given oxidiser anion, copper salts yield more heat than lead compounds, which in turn yield more than sodium, potassium, calcium or barium compounds. In practice, copper salts are not commonly used because of the difficulty involved in their ignition. However, the choice of oxidants and fuels for pyrotechnic effects is extensive, as shown in Tables 10.3 and 10.4. 

Part 2 of the British Standard lists all of the main types of firework within Category 1, Category 2 and Category 3, and provides specification requirements by which the construction and performance of these fireworks can be controlled. Aspects that are addressed include means of ignition, projection of burning matter, projection of debris, principal pyrotechnic effects and the angle of flight of rockets. 

COMPOSITION (Explosive) An intimate mixture of fuels, oxidisers and additives of such particle size that, when pressed, it is capable of producing pyrotechnic effects. 

DEVICE An assembly consisting of various types of fireworks, linked together, each producing specific pyrotechnic effects, with a single point of ignition. 

PAYLOAD The total mass of pyrotechnic effects carried by a rocket, etc. 

The desired pyrotechnic effect must be carefully considered when a fuel is selected to pair with an oxidizer for a high-energy mixture. Both the flame temperature that will be produced and the nature of the reaction products are important factors. The requirements for some of flte major pyrotechnic categories... 

Efficient For a particular composition to be of practical interest, it must produce a significant amount of pyrotechnic effect per gram of mixture. Efficiency per unit volume is also an important consideration when available space is limited. 

To produce the desired pyrotechnic effect from a given mixture, the chemist must be aware of the large number of variables that can affect performance. These factors must be held constant from batch to batch and day to day to achieve reproducible behavior. Substantial deviations can result from variations in any of the following [2] ... 

As both weaponry and the use of explosives for blasting developed, the need for a safe, reliable way to ignite these devices became obvious, and the concept of a pyrotechnic "delay" emerged. A variety of terms are used for materials that either ignite or provide a delay period between ignition of a device and the production of the main explosive or pyrotechnic effect. These include... 

Anon, Design of Ammunition for Pyrotechnic Effects , Engineering Design Handbook,... 

Design of Ammunition for Pyrotechnic Effects , AMCP 706-188 (1974), 3-21 4) Anon, draftTechManual, Army Ammunition Data Sheets for Military Pyrotechnics (National Supply Class 1370) , TM 43-0001-37 (1975)... 

The term "pyrotechnics" is defined in the Explosive Control Law in Japan as those items manufactured with propellants or explosives to meet a certain purpose 5). The materials having pyrotechnical effects are called pyrotechnics in general. Pyrotechnical effects refer to the emission of heat, light, flame, sound, gas or smoke. The terms "pyrotechnic compositions" or "pyrotechnic mixtures" are broadly used. These terms refer to the raw materials for the production of pyrotechnics. Recommendations on the Transport of Dangerous Goods of United Nations c defines "pyrotechnic substance" as follows ... 

Anon, EngrgDesHndbk, Design of Ammunition for Pyrotechnic Effect , AMCP 706-188 (May 1974), AD780 673 151) L.J. Hagemann... 

This comprises substances, mixtures and articles which are manufactured with a view to producing a practical, explosive or pyrotechnic effect. 

Both chlorine atoms of 2,3-dichloroquinoxalines are readily displaced by alkoxide and aryloxide ions to give the corresponding dialkoxy- and diaryloxyquinoxalines." Violent reaction, accompanied by pyrotechnic effects, is reported to occur between 2,3-dichloroquinoxaline and the potassium salts of o-nitrophenol and 2,4-dinitrophenol. Quinoxaline-... 

Pyrotechnic Additive — Material added to a composition for achieving a specific pyrotechnic effect or purpose. 

It must be born in mind that much of what is presented here is application of modern theoretical inorganic chemistry and is a deliberate simplification of what is a complex problem. The future holds better data and from that data, better pyrotechnic effects. 

By the use of the Equations One and Two and an understanding of the causes and effects involved, a great degree of control over the pyrotechnic effects of glitter can be achieved. 

Class 1 comprises (a) Explosive substances (a substance which is not itself an explosive but which can form an explosive atmosphere of gas, vapour or dust is not included in Class 1), except those that are too dangerous to transport or those where the predominant hazard is appropriate to another class (b) Explosive articles, except devices containing explosive substances in such quantity or of such a character that their inadvertent or accidental ignition or initiation during transport shall not cause any effect external to the device either by projection, fire, smoke, heat or loud noise and (c) Substances and articles not mentioned under (a) and (b) which are manufactured with a view to producing a practical, explosive or pyrotechnic effect. UN 2.1.1.1, ICAO 2-1.1.1... 

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