Pyrotechnics performance

Another matter of concern in pyrotechnic formulations is the possibiHty of exchange reactions occurring between components. Addition of ammonium salts to compositions containing nitrate oxidizers can produce ammonium nitrate, a very hygroscopic material. The composition then becomes quite prone to pick up water and its performance deteriorates. The addition of an ammonium salt to a chlorate-based formulation can lead to the... 

Pyrotechnics have been used for military purposes for many centuries as propellants, explosive charges, time fuses, and for illumination. There are still many uses of pyrotechnic devices in military appHcations, where they provide portability, storage stability, simplicity of operation, safety, and the reUability required for military scenarios. The devices must be capable of surviving rough handling, weather extremes, and extended storage, yet reUably perform when called on to function. 

A recent review relating the pyrotechnic reaction mechanism, particle size, stoichiometry, temp and compaction density to burning rate is Ref 66, and a study of the effect of multidimensional heat transfer on the rate of flame propagation is Ref 120, which showed that the material of the delay body has no effect on the performance of most delay compns, a finding which agrees with test data... 

Rogers, J. W., Proc. 8th Int. Pyrotech. Seminar, 1982, 556-573 Pyrotechnic properties of blends with 20% boron were studied [1], and the performance of several other blends has been assessed [2],... 

Whenever the operation to be performed involves the potential to cause the initiation of the propellant, explosive or pyrotechnic (PEP) component(s) of a munition item, the APE is either operated by remote control, with the operator behind a protection wall or barrier, or it is enclosed in a protective barricade or operational shield. Barricades or operational shields are designed to protect personnel and assets from the effects of blast overpressures, thermal effects or fireball, and fragments result from the initiation of PEP components, such as the fuze, primer, propelling charge, burster, etc. 

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... 

Tetranitrohexahydropyrimidine (DNNC) (94) has been synthesized from the nitrolysis of the A(iV -di-fert-butylpyrimidine (93). Levins and co-workers reported the synthesis of DNNC (94) from the nitrolysis of the analogous A. V -di-wo-propylpyrimidine (92). DNNC is a high performance explosive with a detonation velocity of 8730 m/s, impact sensitivity lower than RDX and a very favourable oxygen balance. DNNC has been suggested " for use as an oxidizer in propellant compositions. This is also considered as an excellent oxidant for pyrotechnic compositions. ... 

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... 

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. 

The ratio by weight of potassium nitrate and sulfur corresponding to a balanced - or stoichiometric - mixture will be 4(101. 1) 404.4 grams (4 moles) of KNO 3 and 5(32.1) = 160.5 grams (5 moles) of sulfur. This equals 72% KNO 3 and 28% S by weight. An ability to balance oxidation-reduction equations can be quite useful in working out weight ratios for optimum pyrotechnic performance. 

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] ... 

Particle size of ingredients Homogeneity, and pyrotechnic performance, will increase as the particle size of the various components is decreased. The finer the particle... 

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... 

The pyrotechnic chemist always begins with a very small quantity of composition when carrying out initial experiments on a new formula. The preparation of one or two grams of a new mixture enables one to evaluate performance (color quality and intensity, smoke volume, etc.) without exposure to an unduly hazardous amount of material. 

Another matter to consider is whether or not pyrotechnic compositions will burn, and at what rate, at very low pressures. For reactions that use oxygen from the air as an important part of their functioning, a substantial drop in performance is expected at low pressure. Mixtures high in fuel (such as the magnesium-rich illuminating compositions) will not burn well at low pressures. Stoichiometric mixtures - in which all the oxygen needed to burn the fuel is provided by the oxidizer - should be the least affected by pressure variations. 

McLain has proposed that the maximum in performance centered at approximately 15% boron by weight indicates that the principal pyrotechnic reaction for the BaCrO /B system is... 

Pyrodex" is a patented pyrotechnic composition designed to fulfill many of the funetions of blaek powder. It eontains the three ingredients found in blaek powder plus binders and burning rate modifiers that make the material somewhat less sensitive and slower burning. A greater degree of confinement is required to obtain performance comparable to "normal" black powder [6]. 

U.S. Bureau of Mines (BoM) Impact Apparatus Method T 505.1, Department of Defense, USA. (b) Department of Defense (1987) MIL-STD-650, Explosives Research Laboratory (ERL) Type 12 Apparatus Method T 511.1, Department of Defense, USA. (c) Kohler, J., and Meyer, R. (1993) Explosives, 4th edn, Wiley-VCH Verlag GmbH, Weinheim, Germany. (d) McIntyre, L. (1980) A Compilation of Hazard and Test Data for Pyrotechnic Compositions. Contract Report No. ARLCD-CR-80047, US Army Armament Research and Development Command, Dover, NJ. (e) US Naval Weapons Center (1972) Safety and Performance Tests for Qualification of Explosives, NAVORD OD-44811, Naval Weapons Center, China Lake, CA, USA. ... 

Binders increase cohesion between the particles of fuel and oxidizer, facilitating better consolidation and resulting in better mechanical properties of the end products. In addition, an equally important function is to coat and protect metallic or non-metallic fuels (such as metal or non-metal powders) which may otherwise react with moisture and oxygen. They also modify the burning rate and hence the performance, and at the same time reduce sensitivity to impact or friction. A comprehensive list of binders, natural to synthetic resins used for pyrotechnic formulations follows. 

To summarize, the quality and performance of pyrotechnic formulations depend on a number of important factors [6] ... 

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