Biaxial orientation of poly(ethylene terephthalate). Part III: Comparative structure and property changes resulting from simultaneous and sequential orientation

Commercial operations for producing Poly(ethylene Terephthalate) (PET), Blow molded oriented containers and films, usually involve stretching PET either in simultaneous or sequential modes. The specific orientation characteristics of these two modes are studied with respect to the stress‐strain curves and the strain‐hardening parameter. Degree of orientation, crystallinity, and physical properties are studied for each mode as functions of stretch ratio and temperature. The relationships among physical properties, orientation, and below molding characteristics are studies.