HNF Hydrazinium Nitroformate

N2H5C(N02)3, melts at 397 K and completely decomposes at 439 K, accompanied by an energy release of 113 kJ moTk DTA and TG analyses reveal that the thermal decomposition of HNF occurs in two steps. The first step is an exothermic reaction accompanied by 60% mass loss in the temperature range 389-409 K. The second step is another exothermic reaction accompanied by 30% mass loss in the temperature range 409-439 K. These two steps occur successively and the decomposition mechanism seems to switch at 409 K. 

As in the case of AN, the thermal decomposition process of HNF varies with the temperature of decomposition. Deflagatory decomposition of HNF produces ammonium nitroformate, which decomposes to hydrazine, nitroform, and am-monia.[2 l These products react to generate heat in the gas phase and the final combustion products are formed according to  

The combustion wave structure for HNF consists of two gas-phase zones, similar to that for ADN. However, the melt layer zone observed for ADN is not seen for HNF. 

The temperature increases rapidly in the gas phase just above the decomposing surface of HNF. It then increases relatively slowly in the first gas-phase zone. It increases rapidly once more at the beginning of the second gas-phase zone, with formation of the final combustion products. Thus, the second reaction zone stands some distance above the decomposing surface of the HNF. The second reaction zone is considered to involve the reaction between the 2NO and I/2H2 produced in the first reaction zone, as represented by 

This reduction of NO is highly exothermic but relatively slow at low pressure, because it appears to be a third-order reaction, similar to the dark-zone reaction of nitropolymer combustion. The overall reaction of HNF is represented by 

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Hydrazinium nitroformate (HNF) contains a relatively high concentration of oxidizer fragments, as shown in Table 2.6. When GAP is used as a binder of HNF particles, HNF-GAP composite propellants are made. The maximum of 285 s and the maximum Tf of 3280 K are obtained at (HNF) = 0.90 with an optimum expansion from 10 MPa to 0.1 MPa, as shown in Figs. 4.20 and 4.21, respectively. Since a... 

Composite propellants consist of an oxidizer (AP/AN/ADN), a metallic fuel such as Al, Mg etc and a binder, usually a polymer which also serves as a fuel. Vacuum stability tests (VSTs) suggest that composite propellants are intrinsically more stable than SB, DB and propellants. However, use of more exotic ingredients such as oxidizers (ADN and hydrazinium nitroformate, HNF), binders [poly([NiMMO)] and poly([GlyN)] are likely to introduce severe compatibility-related problems [30, 31]. Some recent research in this direction indicates that stability of such propellants is largely determined by the chemical and mechanical properties of propellants. However, early evidence of deterioration generally comes from a change in their mechanical properties rather than from chemical investigations [32]. 

In search of a high performance and eco-friendly oxidizer, extensive research has been going on in this area for more than two decades and as a result, two oxidizers ammonium dinitramide (ADN) and hydrazinium nitroformate (HNF) have emerged as strong contenders of AP in composite propellants and their important aspects are as follows. 

Ammonium dinitramide (ADN) and hydrazinium nitroformate (HNF) are potential high performance and eco-friendly replacements for AP in composite propellants and efforts are being made all over the globe in this direction. Similarly, there is a need to study these high performance oxidizers and their salts for pyrotechnic applications. Some groups of researchers have already initiated research in this direction and several alkali dinitramide salts have been synthesized and characterized for their elemental content, solubility, thermal behavior and crystal structures. 

The research into energetic molecules which produce a large amount of gas per unit mass, led to molecular structures which have a high hydrogen to carbon ratio. Examples of these structures are hydrazinium nitroformate (HNF) and ammonium dinitramide (ADN). The majority of the development of HNF has been carried out in The Netherlands whereas the development of ADN has taken place in Russia, USA and Sweden. ADN is a dense non chlorine containing powerful oxidiser and is an interesting candidate for replacing ammonium perchlorate as an oxidiser for composite propellants. ADN is less sensitive to impact than RDX and HMX, but more sensitive to friction and electrostatic spark. 

Fig. 1.19 Molecular structures of ammonium dinitramide (ADN), hydrazinium nitroformate (HNF) and triaminoguanidinium nitroformate (TAGNF).

The synthesis of hydrazinium nitroformate (HNF) occurs best through the reaction of anhydrous hydrazine with trinitromethane (nitroform) in methanol or diethyl ether ... 

The currently most promising chlorine-free oxidizers which are being researched at present are ammonium dinitramide (ADN), which was first developed in Russia (Nikolaj Latypov) and is being commercialized today by EURENCO, as well as the nitroformate salts hydrazinium nitroformate (HNF, APP, Netherlands) and triaminoguanidinium nitroformate (Germany) (Fig. 1.19) [8]. The salt hydroxyl ammonium nitrate, HO—NH3 NO3 (HAN) is also of interest. However, all four compounds possess relatively low decomposition temperatures and TAGNF only has a positive oxygen balance with respect to CO (not to CO2). 

Hydrazinium NitroFormate (HNF), was mainly developed as a substitute for ammonium perchlorate for solid propulsion, but has been also proposed as a more energetic oxidizer than HAN for monopropellant, when combined with reductants (Pick et al., 2001 ... 

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