The shock initiation of energetic materials is mediated by the localization of mechanical energy into hotspots. These originate through the interaction of the shock and material microstructure; the most potent hotspots are formed by the collapse of porosity. Recent work using molecular dynamics (MD) has shed light on the molecular mechanisms responsible for the shock-to-deflagration transition following pore collapse in pure energetic materials. However, explosive formulations are composites of energetic crystals and a polymer binder, which differs from the prior focus on pure materials. The role of polymer phases in hotspot formation and its criticality remains poorly understood. We use reactive MD simulations to investigate the role of polystyrene and polyvinyl nitrate films around pores in the shock-induced pore collapse of RDX. The polymer affects the hotspots’ temperature and their criticality. While the presence of inert polymer often delays or hinders chemical reactions of the energetic material, certain geometries accelerate chemistry. The simulations provide a mechanistic understanding of these phenomena.

中文翻译：

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聚合物对冲击引起的孔隙塌陷的影响：通过反应分子动力学确定热点临界点


高能材料的冲击引发是通过将机械能定位到热点来介导的。这些源自冲击和材料微观结构的相互作用；最有效的热点是由孔隙塌陷形成的。最近使用分子动力学（MD）的工作揭示了纯含能材料中孔塌陷后冲击到爆燃转变的分子机制。然而，炸药配方是含能晶体和聚合物粘合剂的复合材料，这与之前对纯材料的关注不同。聚合物相在热点形成中的作用及其重要性仍然知之甚少。我们使用反应性 MD 模拟来研究孔隙周围的聚苯乙烯和聚硝酸乙烯酯薄膜在冲击引起的 RDX 孔隙塌陷中的作用。聚合物影响热点的温度及其临界性。虽然惰性聚合物的存在通常会延迟或阻碍含能材料的化学反应，但某些几何形状会加速化学反应。模拟提供了对这些现象的机械理解。