Ingredients of Pyrotechnic Formulations

The chemical reactivity of the ingredients and their particle size have considerable influence on the ignition characteristics and burning rates of pyrotechnics. Finer particles are easier to ignite, leading to a faster reaction rate because of greater degree of contact between fuel and oxidizer particles. 

Pyrotechnic formulations in general consist of physically intimate mixtures of various combinations of fuels and oxidizers, of which many are in use. The tailoring of the formulation is done by changing the proportions of fuel, oxidizer and other ingredients and also by changing their particle sizes. In addition, additives are used in order to impart special effects to the formulations. 

Charcoal and sulfur were the earliest pyrotechnic fuels. The choice of fuels is very wide, ranging from metallic to non-metallic elements and binary compounds to various types of carbonaceous materials, both natural and synthetic. The main fuels are aluminum and magnesium powders, their alloy, sulfur, lactose, carbon and carbonaceous fuels etc. The fuels listed below are usually powdered materials, which when oxidized provide heat energy. 

In a nutshell, Mg and Al are the most commonly used pyrotechnic fuels to create heat and light. Both have been used in the development of radiation effect. While Mg is the fuel of choice for most illuminating and tracer formulations, Al is still the main ingredient of photoflash and thermite formulations. The pyrotechnic behavior of Mg is due to its low melting and boiling points in comparison to most 

In addition to fuel and oxidizer, other additives are as important to the final formulation as the fuel-oxidizer system, and their role, along with some important examples, is as follows. 

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Red P has been employed as an ingredient of pyrotechnic smoke, delay and safety match formulations (Refs 1,2,3 4). White smoke consisting of small droplets of phosphoric acid have been widely used for military purposes. 

DAATz, having a high positive heat of formation (1032 kj moT1), is considered a potential HEM to be used in rocket propellant and IHE formulations. On the other hand, DHTz may find application as an eco-friendly smoke ingredient in pyrotechnic formulations for special applications. As regards tetrazolates, the tri-aminoguanidinium salt having a heat of formation equal to 560 kj mol 1 and reasonable sensitivity characteristics, these salts compete with DAATz. 

Some of the important properties which are considered when choosing the ingredients for pyrotechnic formulations are density, hygroscopicity, melting and boiling points and decomposition temperatures, oxygen content of oxidizers, thermal conductivity of fuels and containers, nature of combustion products and toxicity etc. 

As mentioned earlier, chlorates are also a major ingredient in various pyrotechnic formulations. Typically potassium chlorate is utilized in this capacity due to the more hygroscopic nature of the sodium analog. Mixed with powdered aluminum and/or sulfur, potassium chlorate produces a mixture commonly referred... 

The oldest and still widely used in pyrotechnics and fireworks "first fire" and "starter" mixture is BkPdr. It belongs to mixts without metallic ingredients. Metallic mixts contain combustible powdered metals, such as Mg, Al, Zr etc. Metalloids B and Si are considered metallic fuels because of their similarity in pyrochemical behavior to metals. Although BkPdrs are described in Vol 2 of Encycl, pp Bl65ff, we are giving here as Table E compns of three formulations used in pyrotechnics, as described by Ellern (Ref 57, p 375)... 

A new area of research and activity in recent years is the development of new explosives based on furazans, furoxans and tetrazines in order to achieve an increase in density, stability, insensitivity and velocity of detonation. As a result, a number of prospective HEMs which are potential ingredients of explosive, propellant and pyrotechnic formulations have been synthesized. 

The knowledge of the important properties of commonly employed oxidizers, fuels, organic and polymeric additives is essential in order to understand their roles in pyrotechnic formulations [5]. The properties of some commonly employed ingredients fuels, oxidizers and organic and polymeric additives are given in Tables 5.2-5.4 respectively. 

In order to achieve the goals of pyrotechnic delay formulation, ingredients are chosen and formulated in an elegant way. The ingredients of a pyrotechnic delay formulation are (i) fuel (carbonaceous materials or inorganic substances) (ii) oxidizer (iii) binder and (iv) retardant, if required. 

The physical integrity of a pyrotechnic formulation may, exceptionally, be threatened by evaporation. This can occur when a rather volatile compound is a necessary component because of unique properties that make it difficult or impossible to replace it with a more stable ingredient. Two such compounds have been described earlier One is metaldehyde of a sublimation point of about 112 C and found only in novelty items such as repeatedly ignitible matches, hence of little concern in commercial practice the other is the HC smoke ingredient hexachloroethane. Its vapor pressure, as eviden d by the odor at room temperature, is sufficient to cause concern. In practice, however, with tightly compressed and sealed mixtures in substantial units, the volatility of HC seems to cause no trouble. 

Mackowiak, H.P. (1991) Recent investigations on gun propellants and formulations for LOVA. Proc. Joint Symposium on Compatibility of Plastics and Other Materials with Explosives, Propellants, Pyrotechnics and Processing of Explosives, Propellants and Ingredients, held at San Diego,... 

Ammonium nitrate finds major applications in explosives and fertilizers, and additional uses in pyrotechnics, freezing mixtures (for obtaining low temperatures), as a slow-burning propellant for missiles (when formulated with other materials, including burning-rate catalysts), as an ingredient in rust inhibitors (especially for vapor-phase corrosion), and as a component of insecticides. 

The newest oxidizer to appear in significant use in pyrotechnics, anunonium perchlorate (AP), has found considerable use in modem solid-fuel rocket propellants and in the firewoiks industry. The Space Shuttle alone uses approximately 2 million pounds of solid fuel per launch the mixture is 70% ammonium perchlorate, 16% almninum metal, and 14% organic polymer/epoxy, with a trace of iron oxide catalyst that can be varied to modify the bum rate. The aluminum powder is a surprising ingredient to find in a propellant, since it generates solid rather than gaseous reaction products, but its substantial heat output as a fuel and its excellent thermal conductivity both contribute to an enhancement of the bum rate of this propellant formulation. 

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