The analysis of the thermal stabil- ity, morphology, and mechanical properties of PET/PE blends containing the surfactants alone in the absence of clay made it possible to evidence separately the effects of the surfactant and of the nanofiller. The role of the surfactant as compatibilization agent was demonstrated. In the absence of nanofiller, the finest morphological and highest ductility were again obtained with the phosphonium surfactant which is the most thermally stable.