Nitropolymer Pyrolants

Physical mixtures of nitropolymers are known as smokeless propellants, as used in rockets and guns. The -O-NO2 chemical bonds contained within the nitropolymer-sact as oxidizer components and the remaining hydrocarbon structures act as fuel components. The major combustion products are CO2, H2O, Nj, and CO, and additional small amounts of radicals such as OH, H, and CH are also formed. These products are fundamentally smokeless without solid particles. 

Several types of nitrate esters are used to formulate smokeless nitropolymers. Nitrocellulose (NC) is mixed with nitroglycerin (NG), trimethylolethane trini- 

Since the reaction involving NO is termolecular in nature, the oxidation of gaseous fuel species by NO is very slow at low pressures and the reaction only occurs when the temperature is well above 1000 K. It is for this reason that flameless burning of nitropolymer pyrolants occurs in the low-pressure region. 

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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. 

When AN powder is mixed with a polymeric material, the oxygen gas produced by the decomposition of the AN powder reacts with the hydrocarbon fragments of the thermally decomposed polymeric material. The major combustion products are GO2 and H2O. Nitropolymers are not used as fuel components of AN pyrolants because of the reaction between the NO2 formed by their decomposition and the AN powder. This reaction occurs very slowly and damages the physical structure of the AN pyrolant. Instead, polymeric materials containing relatively high mass fractions... 

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. 

Tq, of gas-generating pyrolants such as fuel-rich AP-HTPB and fuel-rich nitropoly-mer pyrolants are lower than those of rocket propellants such as AP-HTPB and nitropolymer propellants. The gas-phase temperature is low and hence the heat flux feedback through the wires is low for the gas-generating pyrolants as compared with propellants. However, r /ro appears to be approximately the same for both pyrolants and propellants. The obtained burning-rate augmentations are of the order of 2-5. 

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