Investigation into the crystal morphology and acidity of LLM-105 in recrystallization

Sensitivities and compatibilities of the explosives are greatly influenced by their crystal morphology and acidity. In order to improve the crystal morphology and reduce the acidity, a molecular dynamics simulation of the recrystallization of LLM-105 (2,6-diamino-3,5-dinitropyrazine-1-oxide) with nitric acid as solvent were carried out, and the influences of the process conditions on the acidity of LLM-105 in the process of recrystallization were investigated by the solvent–antisolvent method. The result shows that the nitric acid concentration, water bath temperature, undercooling, stirring speed and dropping mode have the significant effect on acidity. The LLM-105 crystal obtained from the recrystallization with the dropping mode by normal phase, HNO3 (85%) as solvent, water bath temperature of 70°C, anti-solvent temperature of 60°C, dropping rate of 12.5 ml/min and stirring speed of 330 r/min has the regular morphology (blocky and inclined prismatic) and good fluidity, with the acidity less than 0.05% (calculated by HNO3). By means of the mechanical sensitivity and differential heat analysis, the impact sensitivity and friction sensitivity of the LLM-105 crystal from the recrystallization were decreased by 58.4% and 20%, respectively, and the exothermic peak was increased by 14.6°C in comparison with the raw material.