ABSTRACT 2,4,6,8,10,12‐Hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane (HNIW, CL‐20) is currently recognized as the energetic material with the highest energy density in the world and can replace traditional nitramine explosives RDX and HMX for mixed explosives and solid propellants. At present, the most commonly used method for synthesizing CL‐20 is the nitration reaction using 2,6,8,12‐tetraacetyl‐2,4,6,8,10,12‐hexaazaisowurtzitane (TAIW) as the nitration precursor and HNO 3 /H 2 SO 4 mixed acid as the nitrating agent, and then the synthesized crude CL‐20 is converted into ε‐CL‐20 through the solvent/anti‐solvent recrystallization process. However, little is known about the optimal synthesis parameters for the nitration process. In this study, the Taguchi experimental design method was used to determine the optimal synthesis parameters for maximum yield of crude CL‐20. The ε‐CL‐20 produced after crystal form conversion was identified by means of scanning electron microscopy, nuclear magnetic resonance spectrometry, Fourier‐transform infrared spectrometry, X‐ray diffraction, elemental analyzer, simultaneous thermogravimetry‐differential scanning calorimetry, and high‐performance liquid chromatography, and its sensitivity was measured using BAM fallhammer, friction sensitivity tester, and electrostatic spark sensitivity tester. The Taguchi analysis results indicated that the optimal synthesis parameters were as follows: the volume ratio of HNO 3 to H 2 SO 4 was 5:1, the nitration temperature was 82.5°C, the reaction time was 40 min, and the amount of TAIW used was 9 g/100 mL mixed acid, and the maximum yield of crude CL‐20 could reach 92.9%. The average yield of the process for converting crude CL‐20 into ε‐CL‐20 was about 91.8%. In addition, the impact sensitivity, friction sensitivity, and electrostatic spark sensitivity of the synthesized ε‐CL‐20 were 4.23 J, 84 N, and 0.072 J, respectively.
Li et al. (Mon,) studied this question.