Shock and recovery of PTFE powder

Right-circular cylindrical containers with axial cavities were fabricated from 4340 steel (RC38) in two different cavity lengths (2.4 mm and 17.7 mm, respectively), with closure caps. Polytetrafluoroethylene (PTFE) powder specimens, 2.4 mm long, were pressed into the base of each cavity, filling the cavity of the short container, and leaving a 15.3 mm-length air-filled region inside the long container. The specimen porosities were all in the range 44–47%. The caps were secured to the containers by four high-strength screws. Momentum traps were provided for each container. In each experiment, a container was impacted by a gas-gun accelerated steel disk, and soft recovered in rags. For experiments at 0.9 km/s impact speed, the PTFE in the short container showed melting and limited discoloration; in the long container, a jet of PTFE formed and damaged the inside of the cap, with significant discoloration of the residue. In an experiment at 0.3 km /s impact speed with a long container, the PTFE showed no evidence of jetting or discoloration. Computational simulations using the CTH code and a newly-developed model for shock-induced dissociation of PTFE show results that are consistent with the experimental observations.