Nanocomposites are of great industrial and technological interest. In recent years, they have gained rapidly increasing interest due to the combination of properties they present. Thanks to the small dimensions of the nanoparticles, these materials have a high fraction of interfacial regions (interphase) which has a major influence on the physical properties of the material. They allow to combine the properties of the polymer (ease of processing, lightness...) with those of the inorganic filler (optical, magnetic properties...). The polymeric matrices used in this work are two saturated polyesters, namely polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). The method of elaboration of PET/PEN/clay nanocomposites in a single step by reactive extrusion has been successfully carried out. The untreated clay was purified and then activated using three basic reagents namely peroxide, sulfur and a specific gas pedal. PET and PEN were mixed separately in the molten state with reactive clay. PET/4 wt% clay and PEN/7.5 wt% clay showed complete exfoliation.