LLM-105: achieving different morphologies for different properties

Abstract. 2,6-Diamino-3,5-dinitropyrazine-1-oxide, known as LLM-105, stands as one of the best safety/performances trade-offs to date in the field of explosives. Its common synthesis involved a 3-steps process from 2,6-dimethoxypyrazine, known as the DMP route. However, a more recent route, consisting in the dinitration of 2,6-diaminopyrazine-1-oxide (DAPO), offers substantial advantages: there is only one step to be carried out in facilities dedicated to explosives, and the product is highly pure, avoiding the issue of residual ANPZ associated with the DMP route. Initial drawbacks of the DAPO pathway were circumvented through optimization of the quench step. Quenching the nitrating mixture in the presence of nitrates yielded LLM-105 samples with enhanced thermostability and particle size. Particle morphology is a critical issue when developing new formulations, and the work focuses here on the relationships between a microscopic feature (particle morphology) and macroscopic properties. Different morphologies were achieved through specific quench conditions or post-synthesis treatments. For example, sonication of as-precipitated LLM-105 resulted in a dramatic change in the morphology: partial fragmentation occurred, and eroded, rounded particles were obtained. Some specific morphologies induced different behaviors in safety characteristics, but also in PBX processing and in detonics experiments. This was particularly evaluated in small-scale corner turning experiments, using cylinders of LLM-105-based PBXs initiated with a slapper detonator.