Electrical conduction in select polymers under shock loading

It is known that polymers become conductive under shock loading, which can be critical to the operation of explosive driven high current/voltage devices. Hence, the propensity of several select polymers to conduct under shock loading was investigated. Four polymers, Nylon, Teflon, Polypropylene, and High Density Polyethylene, were tested under shock pressures up to ~22 GPa. Shock waves were generated with high explosives, and CTH, a hydrodynamic code developed at Sandia National Laboratories, was utilized to calculate pressure and temporal resolution of the shock waves. Time of arrival measurements of the shock waves were taken to correlate the hydrodynamic calculations with experimental results. A notable delay between shock front arrival and the onset of conduction is exhibited by each polymer. The delay tends to decrease with increasing pressure down to approximately 500 ns for HDPE at ~22 GPa under electric field strength of ~6.3 kV/cm. The data shows that some polymers exhibit more delay than others, thereby indicating better insulating properties under shock loading. Additionally, experiments revealed that the polymers conducted for a finite time on the microsecond time scale before recovering back to an insulating state. This recovery from a shock wave induced conducting state back to insulating state was investigated for a possible opening switch application.