Experimental Studies on the Dynamic Behaviour of Polytetrafluoroethylene (PTFE)

The shock adiabat of PTFE (with the initial density 2.19 g/cm3) has been measured with the impedance matching method at high pressures. LY-12 Al was used as a standard material (the initial density is 2.794 g/cm3, and the linear relation between the shock velocity D and the particle velocity u is D=5.47+1.28u (mm/s).). In the experiments, the plane shock waves were produced by means of the contact explosion technique or the flyer impact technique, and the shock velocity D was measured by the high-speed scanning photography combined with the flash-gap technique. Is the pressure range from 10 to 55 GPa, the obtained linear relation between D and u of PTFE is D=2.10+1.62u (mm/s). At lower pressures (0.2~3 GPa), the experiments were conducted on a gas-gun with the symmetric impact principle, the impact velocities were measured by a laser system the Lagrange particle velocity profiles for loading and unloading processes and the shock velocity in the specimen were measured with the electro-magnetic velocity gages. For the shock loading process, the obtained D-u relation and the shock adiabat are respectively. D=1.24+3.72u-1.94u2 (mm/s) and =2.10+44.52+123.23 where is the axial stress behind the shock front for one-dimensional strain, and is the corresponding bulk strain. The obtained unloading paths are almost in agreement with the shock adiabat. The residual strains seem to be either inexistent or very small. The elastic behavior almost does not occur; i. e. PTFE presents plastic behavior essentially.