It has already been demonstrated that the impact behavior of PET can be strongly improved by rubber modification [2e7]. PET/NR blends have yet to be studied. In this study, various amounts of NR were blended with the PET in a twin-screw extruder using a screw speed of 100 rpm. Fig. 1 shows the Young’s modulus and the notched Izod impact strength of PET/NR blend versus the NR content in the blend. When the NR content is increased, the impact property increases while the Young’s modulus decreases. This is due to the elastomeric nature of NR and is similar to what have been reported for PET/SEBS [10] and for the amorphous copolyester/PEO-g-MA [17] blends.