An experimental investigation of the mechanisms of melting of various thermoplastics elastomers (TPEs) in single screw extruder was carried out under different operating conditions. The TPEs included three polypropylene vulcanized EPDM (TPV) thermoplastic elastomers and two styrene-hydrogenated butadiene block copolymer. The results were compared to new and earlier experimental investigations of the melting of polyethylene and polypropylene. We also characterized the shear viscosity of all polymer melts studied. The TPEs all exhibited yield values in shear flows. To characterize the melting process in a single screw extruder, we used a flow marker procedure which consists of introducing pigments with the neat pellets. This is a technique originally developed by Maddock (1959). At the steady state, we abruptly stopped the extruder operation, cooled the barrel and pushed the screw from the barrel. The polymer carcasses were stripped from the screws and slices cross-sectioned every turn from the hopper to die were photographed and evaluated, and the melting mechanism was determined. The results for the TPEs exhibit significant differences from the crystalline polyolefin.