Here is a calibrated non-linear viscoelastic material model for a generic ABR (Nitrile rubber, Buna-N, acrylonitrile butadiene rubber) tested at room temperature.
Nitrile butadiene rubber is a group of synthetic unsaturated rubbers with good chemical resistance. The material is often used in for hoses and seals.
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 model.