Igniter pyrolants

Acryhc elastomers are normally stable and not reactive with water. The material must be preheated before ignition can occur, and fire conditions offer no hazard beyond that of ordinary combustible material (56). Above 300°C these elastomers may pyrolize to release ethyl acrylate and other alkyl acrylates. Otherwise, thermal decomposition or combustion may produce carbon monoxide, carbon dioxide, and hydrogen chloride, and/or other chloiinated compounds if chlorine containing monomers are present ia the polymer. 

Pyrolants deflagration detonation gas generators, igniters, fireworks, squibs, safety fuses detonators, primers, initiators, detonating fuses... 

The selechon of fuel components to be mixed with oxidizer components is also an important issue in the development of pyrolants for various applications. Metal particles are used as fuel components to develop small-scale pyrolant charges as deployed in igniters, flares, and fireworks. Non-metal particles such as boron and carbon are used to formulate energetic pyrolants. Polymeric materials are commonly used as fuel components to develop relatively large-scale pyrolant charges, such as gas generators and fuel-rich propellants. 

Boron is an important ingredient of pyrolants. A mixture of boron and potassium nitrate particles forms a pyrolant used as an igniter in rocket motors. The stoichiometric mixture of B and KNO3 reacts according to ... 

When a metallized energetic material is burned as a propellant igniter in a rocket chamber, a consequence of the aforementioned production of metal oxides as hot condensed particles is that there is very tittle associated pressure increase. However, the surface of the propellant grain in the chamber is ignited by the hot particles and a stable burning pressure is established. Typical metallized pyrolants used as igniters are shown in Table 11.1. 

Table 11.1 Chemical compositions of metallized pyrolants used as igniters.

The results of thermochemical experiments reveal that an exothermic reaction of GAP occurs at about 526 K and that no other thermal changes occur. When Mg or Ti parhcles are incorporated into GAP to formulate Mg-GAP or Ti-GAP pyrolants, two exothermic reactions are seen the first is the aforementioned exothermic decomposihon of GAP, and then a second reachon occurs at 916 K for the Mg-GAP pyrolant and at 945 K for the Ti-GAP pyrolant There is no reaction between either Mg or Ti and GAP at the temperature of the first exothermic reaction. Both Mg and Ti particles within GAP are ignited by the heat generated by the respechve second exothermic reactions. 

The ignition temperature of a mixture of Ti and C is relatively high compared with those of other pyrolants. When a small amount of polytetrafluoroethylene (Tf) is added to a Ti-C pyrolant, the ignition temperature is significantly lowered due to the exothermic reaction between Ti and Tf Since Tf consists of a -C2F4- chemical structure, the oxidizer gas, F2, is formed by thermal decomposition of Tf according to ... 

Fig. 11.21 shows the results of TG and DTA measurements on mixtures of AP particles and catalysts. The endothermic peak observed at 513 K is caused by the crystal structure transformation of AP from orthorhombic to cubic. A two-stage exothermic decomposition occurs in the range 573-720 K. The decomposition of the AP is seen to be drastically accelerated by the addition of catocene. The exothermic peak accompanied by mass loss occurs before the AP crystal transformation. Although the AP is sensitized by the addition of carborane, no effect is seen on the AP decomposition. The results indicate that carborane acts as a fuel component in the gas phase but does not catalyze the decomposition of AP. Thus, the critical friction energy is lowered due to the increased reaction rate in the gas phase. The results imply that the initiation of ignition by friction is caused by the ignition of the gaseous products of the AP pyrolants.PI... 

The smoke characteristics of three types of pyrolants, namely nitropolymer pyrolants composed of NC-NG with and without a nickel catalyst, and a B-KNO3 pyrolant, have been examined in relation to the use of these pyrolants as igniters of rocket motors. Though nitropolymer pyrolants are fundamentally smokeless in nature, a large amount of black smoke is formed when they burn at low pressures below about 4 MPa due to incomplete combustion. Metallic nickel or organonickel compounds are known to catalyze the gas-phase reaction of nitropolymer pyrolants. 

The projectile acquires a specified supersonic flight speed after burn-out of the booster propellant. The booster nozzle is then ejected to the outside and the port cover is opened. The compressed air resulting from the aforemenhoned shock wave is then introduced through the air-intake. The booster chamber becomes a ramburner and the gas-generating pyrolant is ignited to produce fuel-rich combushon products. 

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