Influence of Polymer on Shock-Induced Pore Collapse: Hotspot Criticality through Reactive Molecular Dynamics

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 on hotspot formation and its criticality is not well-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.

含能材料的冲击起爆是通过机械能集中在热点处来实现的。这些热点源于冲击与材料微观结构的相互作用；最有效的热点是由孔隙坍塌形成的。近期利用分子动力学（MD）所做的工作揭示了纯含能材料中孔隙坍塌后冲击 - 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结剂的复合物，这与之前对纯材料的关注有所不同。聚合物相在热点形成中的作用及其关键性尚未得到很好的理解。我们使用反应性分子动力学模拟来研究聚苯乙烯和聚硝酸乙烯酯薄膜在孔隙周围对黑索今（RDX）冲击诱导孔隙坍塌的作用。聚合物影响热点的温度及其关键性。虽然惰性聚合物的存在常常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。这些模拟为这些现象提供了一种机理上的理解。