Here is a calibrated material model for a PTFE (fluoropolymer, Teflon) tested at Room temperature. The material contained a small amount of graphite and carbon fibers. To use this material model you will need to first install the MCalibration software, and then export the model to your favorite FE software. The calibrated material model is the PolyUMod Three Network (TN) model.
Recommended ANSYS settings when using a PolyUMod material model.