3, 4-2 Nitro Pyrazole Synthesis And Performance Research

Melt-pour explosive based on TNT has been widely used in conventional weapons for its excellent comprehensive performance since the World War Ⅱ. However, the melt-pour explosive based on TNT has a disadvantage that it is not safe enough. Many incidents with great loss have been caused when there is an attack or an accident. In addition, the detonation energy of TNT isn’t high enough which will decrease the power of the ammunition. As a result, more and more researchers begin to focus on the research of TNT replacements.It has been repoeted that the impact sensitivity and detonation performance of3,4-dinitropyrazole(DNP), which has a low melting point as TNT, are superior to those of TNT, and it is a candidate of TNT replacements. In this paper, DNP was synthesized with pyrazole as initial material by three steps:nitration, rearrangement and nitration. The structure of DNP was characterized by IR,1H NMR, MS and EA. The influences of reaction temperature, reaction time and the dosage of fuming nitric acid on the third step reaction were studied by orthogonal experiment. The preferable reaction conditions are as follow:the ratio of3-nitropyrazole(3-NP) and fuming nitric acid is1g:1.1ml, the reaction temperature is held at80℃, and the reaction time is1.5h. Under these conditions, the yield of DNP from3-NP can reach44.3%.Until now, the thermal properties of DNP which are basic physical and chemical properties of explosives have been reported rarely. In this paper, the thermal properties of DNP were discussed. The first step thermal decomposition of DNP and its non-isothermal kinetics were studied by the TG-DSC techniques and the kinetic parameters were obtained: Eα=91.6kJ/mol, lnA=42.7/s, g(α)=[-ln(1-α)]3,f(α)=(1/3)(1-α)[-ln(1-α)]-2. Under the condition that tempreture rose and fell at5℃/min, the supercooling degree of DNP was18.8℃. Compared with that of TNT (21.4℃), DNP has the advantage to improve the quality of the melt-cast. Under the same condition, the melting enthalpy of DNP was91.1J/g and the crystalline enthalpy was-87.6J/g. When the tempreture rose at5℃/min, the initio decomposition tempreture of DNP was207.8℃, compared with that of TNT(292℃) and RDX (210℃), the thermal stability of DNP was a little worse than TNT, but is close to that of RDX. With the Zhang-Hu-Xie-Li method, the critical temperature (Tb) of thermal explosion of DNP was obtained (224℃). The vacuum stability tests showed that DNP has a good vacuum stability and compatibility with RDX.The experimental results of mechanical sensitivity of DNP (impact sensitivity:0%; friction sensitivity:0%; H50=71.3cm) showed that the sensitivity to mechanical simulation of DNP is lower than that of TNT. Since it is difficult to obtain the single crystal of DNP, the crystal structure was predicted based on Karfunkel-Gdanitzand method. Meanwhile, the detonation properties of DNP were predicted based on Kamlet method. Calculated results indicated that the space group of DNP is Pbca most probably, and its detonation velocity and pressure are8.04km·s-1and28.6GPa respectively.