Shock Wave Induced Reactivity of Al-PTFE

Aluminum-Polytetrafluoroethylene (Al-PTFE) mixtures have demonstrated the capability to produce rapid exothermic reactions, characterized by strain rates in the range of 10³ to 10⁶ sec^-1. Historically, over the past four decades, these reactions have been predominantly attributed to a shear stress ignition mechanism. However, recent investigations utilizing split Hopkinson pressure bar experiments have revealed that a pure compression wave can initiate the swift aluminum-fluorine reaction.

In this study, we encapsulate aluminum and Al-PTFE pellets within steel and copper casings. By impacting these casings with a flyer plate traveling at a velocity of 2200 m/sec, we subject the pellets to shock wave compression. The free surface velocity of the casings is measured using Photonic Doppler Velocimetry (PDV). Additionally, we conduct hydrocode simulations to model both processes.

Our findings indicate that for the aluminum pellet, the simulation results closely match the PDV velocity measurements. Conversely, for the Al-PTFE pellet, the simulated free surface velocity is lower than the experimental results, suggesting an inherent reactivity within the pellet, specifically under pure compression.