Study On Anti-solvent Crystallization Nucleation Kinetics And Crystal Morphology Of Insensitive High Explosive LLM-105

2,6-Diamino-3,5-dinitropyrazine-1-oxide(LLM-105)is a new type of insensitive high explosive developed in recent years due to its excellent safety performance and thermal stability.It has great application prospects in explosives,propellants and main charges,and has attracted widespread attention on the field of energetic materials.The crystal properties of LLM-105 have an important influence on its physical and chemical properties.Among them,the crystal morphology is one of the important crystal characteristics,because it not only affects the physical and chemical properties of LLM-105,but also affects the operation process of LLM-105 formulation and granulation,thereby affecting the application of LLM-105 explosives.The solution crystallization method is one of the effective methods to adjust the crystal morphology.During the solution crystallization process,the crystal nucleation kinetics and crystal growth kinetics both affect the final crystal morphology.In this paper,the anti-solvent crystallization of high-energy and low-sensitivity explosive LLM-105 is studied.The research contents include the following aspects:(1)The nucleation kinetics of LLM-105 during anti-solvent crystallization.The nucleation process of LLM-105 at different stirring speeds and different supersaturations was studied using DMSO as the solvent and ethyl acetate as the anti-solvent.The nucleation induction period was determined by turbidity method.It was found that when the supersaturation ratio of the LLM-105 solution is S>2.53,the solution system mainly undergoes homogeneous nucleation;when the supersaturation ratio is S<2.53,the solution system mainly undergoes heterogeneous nucleation.In addition,based on the experimental data and the classic nucleation theory,the nucleation kinetic parameters of LLM-105 anti-solvent crystallization were calculated,and the calculated surface entropy factor f value was less than 3,indicating the growth mode of LLM-105 in ethyl acetate anti-solvent,It is a continuous growth mechanism.(2)Research on the effect of anti-solvent on LLM-105 crystal morphology.Using DMSO as solvent,the effects of water,methanol,acetic acid,nitromethane,ethyl acetate,ethanol,methylene chloride,o-dichlorobenzene and toluene on the morphology of LLM-105 crystals were studied.Under the same experimental conditions,only the type of anti-solvent was changed to adjust the morphology of LLM-105 crystals,and LLM-105 crystals with different morphologies such as X-shaped,spherical,rod-shaped,needle-shaped and dendritic were obtained.The results show that the polarity and functional groups of anti-solvent molecules play an important role in the crystal morphology of LLM-105 explosive.P-XRD and FTIR results show that these anti-solvents only change the crystal morphology of LLM-105,but will not cause the crystal form to change.DSC and TG results show that the crystal morphology significantly affects the heat of LLM-105 crystal performance.(3)Preparation of spherical LLM-105 crystal and its mechanical properties.Using DMSO as a solvent and adding polymer additives,ethyl acetate as an anti-solvent,spherical LLM-105 crystal particles were prepared and the mechanical properties of the spherical LLM-105 crystal were tested by the compression stiffness method,and the LLM-105 crystal was calculated according to the compression curve The initial secant modulus(EISM),the results show that: compared with needle-shaped particles,spherical particles appear "harder" or "harder",spherical LLM-105 crystal particles have better mechanical properties than needle-shaped crystals.