Moderators, pyrotechnics

In devices which can tolerate moderate ignition delay, further development of non-primary initiators (Refs 31, 77, 97 112) will extend the storability, the manufacturing safety, the electromagnetic Held and spark sensitivity and the high temp compatibility of pyrotechnic devices... 

Mixtures of sulfur and potassium perchlorate, used in pyrotechnic devices, can be exploded by moderate impact. All other inorganic perchlorates form such impact-sensitive mixtures. 

The main species responsible for the blue flame from such a composition is cuprous chloride, CuCI hence the use of this salt together with the chlorine producer (hexachloroethane) and a source of extra copper (pyrotechnic copper powder). The cellulose dust acts as a moderator to control the burning rate of the pressed composition. 

The pyrotechnic composition described above will also contain plasticisers, stabilisers and combustion moderators, thus complicating the overall reaction. 

G1 Is generally considered to be moderately toxic, and more toxic than CS. It is used In much the same way as CS—sprayed in a liquid carrier, as a micropulverlzed powder, or In pyrotechnical grenades. 

Some pyrotechnic formulations Ti/KDN/NC and Ti/CsDN/NC were formulated and tested for combustion velocity, sensitivity to impact, friction and electrostatic discharge etc. The data show that both formulations are extremely sensitive to impact (the sensitivity being in the range of pure HMX and PETN ). Further, it is also seen that the Ti/KDN/NC formulation is less sensitive [145] than Ti/ CsDN/NC. On the contrary, the formulations show a moderate sensitivity to friction and electrostatic discharge. The evaluation of such systems as components in ignition formulations appear to be very promising as this may allow replacement of the heavy metal primary explosives which are toxic in nature. 

Deterrents or Moderants, called by the British Modifiers (Also known as Deadeners). The following information may be added to the brief description given in Vol 3, p C381 under Coating of Explosive, Propellant, and Pyrotechnic Compositions... 

SAFETY PROFILE Poison by intravenous and intraperitoneal routes. Moderately toxic by ingestion. Experimental teratogenic and reproductive effects. Questionable carcinogen. Probably a severe eye, skin, and mucous membrane irritant. Mutation data reported. A powerful oxidizer. Explodes on contact with red-hot carbon, cyclopentadienylsodium (at 100-130°C), potassium acetate + heat. Reacts violently with ammonium thiocyanate, carbon, lead hypophosphite. When heated to decomposition it emits very toxic fumes of Pb and NOx. Used as a mordant, a chemical reagent, and in production of matches and pyrotechnics. See also LEAD COMPOUNDS and NITRATES. 

Most commercially available methylaluminoxanes are produced by careful reaction of water with trimethylaluminum (TMAL) in toluene. Reaction must be closely controlled to avoid what renowned organometallic chemist John Eisch called "a life threatening pyrotechnic spectacle" (16). Unfortunately, there have been explosions and injuries reported during MAO preparations. Water must be introduced at low temperature and in forms that moderate the potentially violent reaction. For example, water has been introduced as hydrated salts, ice shavings or atomized spray. Even with these precautions, explosive reactions have occurred. The overall reaction is given in eq 6.1. 

Moderately-sized and simply-built rockets, cardboard mortars, or integral parts of fireworks items that propel such fireworks or military signals into the air are always regarded as pyrotechnic components. Subminiature rocket projectiles and very small control rockets for steering missiles and spacecraft in flight may or may not be considered in this category. 

Highly hydrated salts have been proposed in mixtures where the water is intended to be an essential reactant as oxidizer. Such salts are obviously not stable, but they may form lower hydrates that are stable even at moderately elevated temperature and might be safely used. Undoubtedly, those hydrates that are the normal products of commerce, such as the vitriols, borax, etc., would be dubious candidates for any pyrotechnic formula. 

When the first edition of this book was published in 1985, a widely held opinion among pyrotechnicians was that potassium perchlorate was the ideal oxidizer to use in energetic pyrotechnic compositions, and potassium nitrate was the first choice for moderately energetic systems. Similarly, ammonium perchlorate was viewed as an ideal oxidizer for propellant formulations, producing all gaseous products in its thermal decomposition. 

TITANIUM SPARKS (See color insert following page 112) A titanium fountain uses relatively coarse titanium particles blended into a moderately fast-burning pyrotechnic composition to produce a beautiful spray of white sparks. This type of fountain effect is widely used in the fireworks industry as well as in theatrical pyrotechnical articles (special effects) for stage presentations. (Photo by Tim Wade and Dennis King, courtesy of MP Associates.)... 

The pyrotechnic composition contains an active oxidizer and a significant percentage of metal fuel in fine particle size (usually <270 mesh). Small to moderate amounts of additional chemicals, such as sulfur, may be present. 

In a comparative study five different thermochemical codes were used to calculate the equihbrium composition of five pyrotechnics including a particular MTV formulation described down below in Table 5.4 [17]. The results are given in the following tables (Tables 5.5-5.8). As is evident from the comparative temperature plot in Figure 5.9 all codes but the TANAKA code agree quite well and show only moderate deviation with respect to preferred reaction products. The predicted adiabatic combustion temperature is in good accord with experimental determination reported data (Chapter 9.3) (Figures 5.10-5.13). 

---