Extension of the window correction for Kel-F 800: A near impedance-matched window for high explosives

Abstract

The chemical reaction zone (CRZ) of detonating explosives is defined by the leading, inert shock front, which compresses the explosive to the von Neumann (vN) spike condition on the unreacted Hugoniot, and the Chapman-Jouget (CJ) sonic locus condition, according to the Zel’dovich/von Neumann/Doering (ZND) one-dimensional theory of detonation. The CRZ is often measured using optical velocimetry techniques at a windowed interface; the window affects the reaction zone dynamics due to wave interactions from the interface. Fluoropolymer windows are attractive as they provide a near impedance match to most common explosives with initial densities 0ρ = 1.8-2.0 g/cm3. Poly(chlorotrifluoroethylene-co-vinylidene fluoride) (Kel-F 800, Lot 30013) was purchased from 3M Inc., St. Paul, Minnesota. Small (150 mm × 150 mm × 50 mm) billets were prepared by compression molding the polymer at 90 °C and ∼50,000 psi by Afton Plastics. This method resulted in a semi-transparent, golden-colored billet from which window samples were machined and polished to an optical clarity for experiments. To extend the window correction for Kel-F 800 (see D. M. Dattelbaum et al., Proceedings of the 15th International Detonation Symposium (2014)), a series of gas gun-driven plate impact experiments were performed using both VISAR (532 nm) and PDV (1550 nm) velocimetry methods to extend the window correction to a larger range of initial shock pressures and densities.