Electrically conductive thermoplastic polymer composites of particulate thermoplastic polyester polymers, electrically conductive components (carbon nanofibers, graphene nanoplatelets, and/or conductive metal nanoparticulates), processing aids such as plasticizers, thermal stabilizers, etc., as well as nanoscopic particulate fillers such as nanoscopic titanium dioxide, etc., the electrically conductive components being distributed substantially uniformly in the composite to form an electrically conductive network. Also, methods for preparing thermoplastic polymer composites, a system for collecting extruded filaments prepared from thermoplastic polymer composites as a coil of filament, as well as method for tempering articles formed from thermoplastic polymer composites to increase the degree of crystallinity of the thermoplastic polymers and thus their mechanical strength properties.