Thepresent research analyzes the effect induced through addition of two zinc concentrations to composites based on recycled PET (polyethylene terephthalate), as a polymer matrix. Prior to mechanical assessment, the optimum grinding time was determined, namely, where the smaller particle size was generated (PET–420mm and Zn-5mm), that was 3 h. Subsequently, a comparison was done between two different blends, changing the zinc concentration 10 or 30 wt. %, from which the necessary test specimens for isothermal sintering were prepared and exposed at 256°C for 10, 15 and 20 minutes periods. These preliminary specimens permitted to value, for each zinc concentration, theirdensity, hardness (shore D) and water absorption. The best results were obtained with the samples sintered for the intermediate periods. The flexion and compression toughness were evaluated, where the blend with the higher toughness contained 30 wt. % Zn.