Nitramine Decomposition

Organic Solids A few organic compounds decompose before melting, mostly nitrogen compounds azides, diazo compounds, and nitramines. The processes are exothermic, classed as explosions, and may follow an autocatalytic law. Temperature ranges of decomposition are mostly 100 to 200°C (212 to 392°F). Only spotty results have been obtained, with no coherent pattern. The decomposition of malonic acid has been measured for both the solid and the supercooled liquid. The first-order specific rates at 126.3°C (259.3°F) were 0.00025/min for solid and 0.00207 for liquid, a ratio of 8 at II0.8°C (23I.4°F), the values were 0.000021 and 0.00047, a ratio of 39. The decomposition of oxalic acid (m.p. I89°C) obeyed a zero-order law at 130 to I70°C (266 to 338°F). 

This powerful but relatively insensitive explosive decomposes violently at 202° C, and gives lead and silver salts which are highly impact sensitive [1], Though not endothermic (AH°f —103.3 kJ/mol), as a bis-nitramine it has a rather high heat of decomposition (3.91 kJ/g) which it is calculated would attain an adiabatic decomposition temperature over 2250°C, with a 60-fold pressure increase in a closed system [2],... 

Some explosives are not volatile enough to be analyzed via GC the relatively high temperatures required can cause decomposition of some explosives (e.g., nitrate esters, nitramines) excessive contamination often present in hand swabs from postexplosion debris can interfere with optimum performance of some detectors... 

Melius, C. F., and Binkley, J. S., Thermochemistry of the decomposition of nitramines in the gas phase., in 21st Symposium (Inti) Combustion. The Combustion Institute, Pittsburgh, 1986, p. 1953. 

Secondary nitramines have been prepared from the metathesis of dialkylcarbamyl chlorides with silver nitrate in acetonitrile followed by the spontaneous decomposition of the resulting dialkylcarbamyl nitrates.Yields of nitramine are low and accompanied by nitrosamine impurities. 

When some portion of the AP particles contained within an AP composite propellant is replaced with nitramine particles, an AP-nitramine composite propellan-tis formulated. However, the specific impulse is reduced because there is an insufficient supply of oxidizer to the fuel components, i. e., the composition becomes fuel-rich. The adiabatic flame temperature is also reduced as the mass fraction of nitramine is increased. Fig. 7.49 shows the results of theoretical calculations of and Tf for AP-RDX composite propellants as a function of Irdx- Th propellants are composed of jjxpb(0-13) and the chamber pressure is 7.0 MPa with an optimum expansion to 0.1 MPa. Both I p and T)-decrease with increasing Irdx- The molecular mass of the combustion products also decreases with increasing Irdx due to the production of Hj by the decomposition of RDX. It is evident that no excess oxidizer fragments are available to oxidize this H2. 

Since nitramine pyrolants are fuel-rich materials, the flame temperature decreases with increasing hydrocarbon polymer content The polymers act as coolants and generate thermally decomposed fragments as a result of the exothermic heat of the nitramine particles. The major decomposition products of the polymers are H2, HCHO, CH4, and When AP particles are incorporated into nitramine pyrolants, AP-nitramine composite pyrolants are formed. AP particles produce excess oxidizer fragments that oxidize the fuel fragments of the polymers that surround them. Thus, the addition of AP particles to nitramine pyrolants forms stoichiometricaUy balanced products and the combustion temperature increases. 

Heat of decomposition. Since the products of a relatively slow ( low temp) decomposition of an explosive will often be quite different from deton products, it is not surprising that AHdecomp f AHdet- Hall (Ref 8) measured the decomposition of solid nitramines in the temp range of 365-540°K. In the following tabulations some of his data are compared with AHdet taken from Table 1... 

A study was conducted to find out the effect of addition of these nitroplasticizers on ballistic properties of AP and RDX/HMX filled CMDB propellants. The data generated clearly indicated that the incorporation of nitroplasticizer, that is, 1 1 mixture of BDNPF and BDNPA in place of diethyl phthalate (DEP) for AP and nitramine based CMDB propellants improved the burn rates as well as /sp and thermal decomposition behavior of these propellant formulations [193]. 

One of the characteristics of nitramines is the ease with which they decompose in sulphuric acid. Primary nitramines undergo decomposition with particular ease alcohol is formed and NzO is evolved on boiling in dilute (2%) sulphuric acid (van Erp [14], Backer [15]) ... 

Secondary nitramines are more stable towards sulphuric acid and decomposition rarely occurs until 40% or more sulphuric acid is used at a temperature of 100°C. 

With primary nitramine sulphuric acid may promote the separation of nitric acid, which results in extensive decomposition of the substance. This will be discussed in more detail when dealing with nitroguanidine (p. 26). 

Most nitramines are fairly resistant to alkalis. Some of the primary amines, e.g. the simple aliphatic ones, are not susceptible to decomposition even under the influence of a hot, 20% solution of potassium hydroxide (van Erp [14]). On the other hand, Hantzsch and Metcalf [19] found that N-nitraminoacetic acid is decomposed by sodium hydroxide. According to Barrott, Gillibrand and Lamberton [20] most primary amines undergo decomposition on treatment with a solution containing 0.8-8% of NaOH at a temperature of 95°C. The reaction proceeds according to the formula ... 

This is one of the simplest nitramines obtained by Thiele and Lachman [1] by the decomposition of nitrourethane ... 

Davis and Abrams [8] report the following experimental observations in support of this supposition. On heating a solution of ammonium nitrate in sulphuric acid to 150°C, nitric acid cannot be distilled, but nitrous oxide is evolved, probably from the decomposition of nitramine. If, however, the solution is kept for a long time between 90 and 120°C, nitric acid can be obtained by distillation. The authors ... 

Nitramine has explosive properties but it is not of any practical value for many reasons, primarily because of its high reactivity which impairs its chemical stability. It decomposes at a temperature as low as its melting point. At room temperature it decomposes slowly, to form nitrous oxide and water. On heating to 60-65°C decomposition occurs in an aqueous solution. It decomposes explosively on contact with concentrated sulphuric acid. ... 

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