Poly(ethylene terephthalate) blends for permeability barrier applications

Poly(ethylene terephthalate) (PET) offers good properties as a material of choice for various packaging, electronic, and other applications. In these applications in general, the PET articles achieve improved toughness and other physical properties through molecular orientation resulting from stretching at temperatures slightly above its Tg. Without such orientation, these articles suffer from poor impact toughness. We have been investigating modifications of PET for improving toughness and retaining the permeability properties. PET having intrinsic viscosities of 0.5 to 0.7 have been modified with low modulus polymers, particularly ethylene copolymers such as ethylene-methacrylic acid (EMAA) copolymers. The effect of crystallinity on toughness was determined. The crystallinity was established by Differential Scanning Calorimetry (DSC) techniques. Many of these modified PET compositions have good toughness and permeability barrier properties for various packaging and other controlled permeability applications such as containers and films.