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

TL;DR

This study uses reactive molecular dynamics to explore how polymer binders influence hotspot formation and criticality during shock-induced pore collapse in energetic materials, revealing that polymers can both hinder or accelerate chemical reactions depending on geometry.

Contribution

It is the first to investigate the effect of polymer phases on hotspot formation and criticality in composite energetic materials using reactive MD simulations.

Findings

Polystyrene and polyvinyl nitrate polymers alter hotspot temperatures.

Polymers can delay or hinder reactions in some geometries.

Certain geometries with polymers accelerate chemical reactions.

Abstract

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.