Here is a calibrated material model for a generic polyethylene terephthalate (PET) tested at room temperature. 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.
The provided material model is not temperature-dependent, but if you are interested in a temperature-dependent model, then we can certainly test and calibrate that model for you. Just send us a message.
Also, as a reference, the glass transition temperature of PET is usually between 69°C and 85°C.