Spinning of PEN, PEN/PET Polymer Blends Aslı Ertan, Emine Güven, İbrahim Yıldırım Kordsa Global Endüstriyel İplik ve Kord Bezi Sanayi ve Ticaret A.Ş. Polyethylene naphthalate (PEN) has many advantages over polyethylene terephthalate (PET) and is used for high performance fiber applications. PEN is superior to PET in modulus, dimensional and thermal stability. Yarns made of PEN have superior performance to those from PET and are highly desirable for use as tire cord. When used as cap-ply and carcass material, PEN cords can improve the dimensional stability, rolling resistance, noise, and safety of tires. On the other hand, major disadvantages of pure PEN are its higher cost and limited availability. Blends of PEN and PET have attracted research interest because they combine excellent properties of PEN with the relatively lower cost of PET. Up to date, monofilament and multifilament pure PEN studies have been completed in Kordsa Global R&D center in lab scale. Physical properties, characterization and dipped cord studies have been performed with the multifilament yarns developed. On the other hand, different concentrations of PET/PEN blend studies have been conducted in monofilament system in lab scale. Similarly, all the studies regarding the characterization and physical properties of monofilament blends have been completed. Efforts are being carried out in developing multifilament PET/PEN blends in pilot plant and studies are going on to accomplish this challenging task.