Unknown composition of composite waste of tire treads (CWT), supplied by a truck tire remoulding company, were processed in an intermeshing corotating twin-screw extruder (ICTSE). The extrusion process was applied to evaluate the efficiency of the thermomechanical recycling on the devulcanization of rubbers from CWT. Polypropylene (PP) and Low Density Polyethylene (LDPE) were adopted as swelling agent of the CWT, extruded with different process parameters and rubber granulometry. After extrusion, samples were subjected to xylene extraction to determine the soluble fraction (SF). Subsequently, the samples were evaluated by infrared spectroscopy (FTIR), thermogravimetry (TG) and Difference Scanning Calorimetry (DSC). The results showed that the highest SF (approximately 29 wt%), was obtained with higher screw rotating speeds and CWT with smaller particle size. Higher SF indicates a higher degree of devulcanization and possibly degradation of the rubbers. Analysis of the SF by FTIR and DSC showed that the Natural Rubber (NR) was the main rubber extracted from extruded samples. In addition, PP was more effective than LDPE in the devulcanization process of the CWT, once it promoted a higher SF of the CWT.