DSC Study of Solid-Liquid Equilibria for Energetic Binary Mixtures of Methylnitramine with 2,4-Dinitro-2,4-diazapentane
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Section I: Basic and Applied Research
DSC Study of Solid-Liquid Equilibria for Energetic Binary Mixtures of Methylnitramine with 2,4-Dinitro2,4-diazapentane and 2,4-Dinitro-2,4-diazahexane B.V. Farahani, F.H. Rajabi, B. Hosseindoust, and N. Zenooz
(Submitted May 8, 2010; in revised form August 23, 2010) Binary phase diagrams for two mixtures of methylnitramine (1) + 2,4-dinitro-2,4-diazapentane (2) (eutectic temperature TE = 285.1 K, eutectic composition x1 = 0.565) and methylnitramine (1) + 2,4-dinitro-2,4-diazahexane (2) (eutectic temperature TE = 280.3 K, eutectic composition x1 = 0.653) were studied using differential scanning calorimetries (DSC). For both systems simple eutectic behavior was observed. The eutectic compositions were also determined using Gray’s model and the fractional transformation method.
Keywords
binary mixtures, DNDA-6, DNDA-7, DSC, methylnitramine, solid-liquid equilibria
1. Introduction The knowledge of solid-liquid equilibria (SLE) is important in many fields of industrial chemistry such as design of separation processes for isomeric compounds, purification and crystallization of chemicals. SLE data are also very important for designing pipelines and reactors because undesired crystallization can lead to safety risks. Furthermore results of solid-liquid equilibria are used by geologist, chemists, ceramist, metallurgists and other scientists to organize and summarize experimental and observational data. SLE results are also used to make predictions about processes that involve chemical reaction among phases.[1] In the past, conventional methods for determination of SLE data were cooling curves and visual measurements. Recently it has been shown that experimental technique using Differential Scanning Calorimetry (DSC) is useful for more accurate determination of these data than those from traditional methods. The DSC method is able to show heat change during the phase transition and consequently the phase boundaries can be determined.[2-5] Using this method and some mathematical models for DSC such as Gray’s model, eutectic-points composition and temperature can be determined. In this work, solid-liquid phase diagram for two binary mixtures of methylnitramine (CH4N2O2) with 2,4dinitro-2,4-diazapentane and 2,4-dinitro-2,4-diazahexane
were studied using DSC and a fractional transformation method.[6] Methylnitramine is a primary nitramine. It contains acidic hydrogen in the form of -NHNO2 and consequently in the presence of moisture corrodes metals and forms metal salts, some of which are primary explosives. This is the reason why powerful explosives like methylnitramine have not found practical application.[7] However methylnitramine is a useful precursor for synthesis of some methylenedinitramine such as 2,4-dinitro-2,4-diazapentane (DNDA-5) and 2,4-dinitro-2,4-diazahexane (DNDA-6). The mixture of these compounds with 3,5-dinitro-3,5-diazaheptane in given proportion produce DNDA-57 energetic plasticizer. The propellant powders produced by using DNDA-57 plasticizer have combustion behavio
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