Here is a calibrated viscoelastic material model for a Vitron fluoroelastomer tested at room temperature.
Viton, a kind of FKM, is a synthetic fluoroelastomer. The material is commonly used in o-rings.
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 Bergstrom-Boyce (BB) model.