Formulations of Pyrolants

The chosen combinations of these chemicals and metals depend on the requirements of the specific application. Gasless combustion prevents pressure increase in a closed combustion chamber. Some combinations of metal particles and metal oxide particles or of metal particles and crystalline oxidizers are chosen as chemical ingredients of gasless pyrolants. On the other hand, hydrocarbon polymers are used to obtain combustion products of low molecular mass, such as H2O, CO, CO2, and H2. High pressure is thus obtained by the combustion of hydrocarbon polymers. Table 10.6 shows the chemical ingredients used to formulate various types of pyrolants. 

---

Hydrocarbon polymers (HCP) are used not only as fuel components but also as binders of crystalline oxidizers and metal powders in the formulation of pyrolants, similar to composite propellants and plastic-bonded explosives. There are many types of HCP, the physicochemical properties of which are dependent on their molecular structures. The viscosity, molecular mass, and functionality of the poly-... 

Al and Mg particles are favored metals in the formulation of pyrolants because of their high potential for ignitability and combustion. However, the combustion products of Al and Mg particles tend to agglomerate to form relatively large metal oxide particles. Since the densities and heats of combustion of Ti and Zr are higher than those of Al and Mg, Ti and Zr are more favorable for use as fuel metals in ducted rockets. 

Table 10.6 Chemical ingredients used to formulate the seven types of pyrolants.

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. 

Table 12.7 Chemical formulations of the pyrolants used to evaluate smoke characteristics (mass fraction).

Nitropolymers composed of -O-NO2 functions and hydrocarbon structures are pyrolants that produce fuel-rich products accompanied by exothermic reaction. Typical nitropolymers are mixtures of nitrocellulose, nitroglycerin, trimethylolethane trinitrate, or triethylene glycol dinitrate, similar to the double-base propellants used in rockets and guns. Mixtures of these nitropolymers are formulated as fuel-rich pyrolants used in ducted rockets. This class of pyrolants is termed NP pyrolants. 

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. 

A mixture of B and AP particles formulates an energetic B-AP pyrolant. A small amount of polymeric material is added to serve as a binder of the B and AP parti-... 

---