There are several material models in Abaqus that can be used for thermoplastics. Their choice depends on the type and magnitude of loading, analysis procedure and desired response. The easiest and the most common approach is to use regular elastoplastic material. But for large strains, you should switch to hyperelasticity while for the inclusion of viscous effects you should use viscoelasticity. In some cases, creep and stress relaxation might also be important and then you need to define material properties related to those effects.