Nitroformate, hydrazinium

Another high energy and environment friendly oxidizer which has recently come to prominence as a result of painstaking research at the European Space Agency (Aerospace Propulsion Products Division) and its sub-contractors (TNO-PML, 

Delft University of Technology and the University of Delaware) is hydrazinium nitroformate [N2H5.C (N02)3 Structure (4.2)] a salt of hydrazine (N2H4) and nitro-form or trinitromethane [HC(N02)3], reported to have been discovered in 1951. Of course, this is made without the use of N205. It is prepared as a precipitate [74] by acid-base reaction between nitroform and hydrazine, Equation 4.18. 

Since the reaction is highly exothermic, it is carried out under controlled temperature of 5 °C in ethylene dichloride as the reaction medium. HNF is a yellow-orange needle-shaped crystalline material with monodinic packing. The crystallographic results indicate that [N2H5]+ ions are hydrogen bonded to neighboring [C(N02), ions. It is a water soluble salt at elevated temperatures. It may also be in an equilibrium state with its pre-dissociated form. 

The most crucial step in the synthesis of HNF is the production of nitroform where a number of accidents have been reported. Almost all aspects relating to HNF synthesis, characterization, properties (physical, chemical and explosive), thermal behavior and toxicity etc., have been reported in the literature [75-81] as a result of extensive research of ESA, TNO-PML and FOI. 

of HNF lies in the range of 115-124 °C depending on its purity and it is suitable for processing of propellant formulations. The m.p. of an oxidizer is important because curing of composite propellants is usually done at elevated temperature. Further, there is no measurable moisture uptake for HNF. 

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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... 

Military propellants are based on relatively powerful oxidisers and fuels of high calorihc value in order to develop an improved thrust or impulse. Thus the most commonly-used oxidisers are potassium perchlorate, ammonium perchlorate or more esoteric compounds such as hydrazinium nitroformate. Metallic fuels include aluminium, magnesium and beryllium, while binders are mainly hydrocarbons such as polybutadiene, polyisobutylene, polyurethane or poly(vinyl chloride) (PVC) as presented in Table 3.2. 

Binary explosive Hydrazine nitroform Hydrazinium nitroformate Hexanitrotetrachloroazobenzene Ammonium dinitramide... 

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. 

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