Preparation of high-modulus and high-strength poly(ethylene terephthalate) film by zone-annealing method



The zone-annealing method was attempted to prepare high-modulus and high-strength poly(ethylene terephthalate) (PET) film. The film having Young′s modulus of 14.5 × 1010 dyn/cm2 and a tensile strength of 86.9 kg/mm2 in the drawing direction was obtained. These values correspond to four times those of a biaxial-stretched PET film available commercially. The dyanmic viscoelastic properties also were measured. The dynamic storage modulus was 15.4 × 1010 dyn/cm2 at room temperature, and a high value of 3.6 × 1010 dyn/cm2 even at 200°C. The latter value is slightly higher than the room temperature modulus of the commercially available film. From the intensity and temperature position of α-dispersion E″ peak, it was suggested that the amorphous chains in the zone-annealed film was densely packed in a highly oriented state. Furthermore, the crystallinity, orientation, especially double orientation, and molecular chain conformation of the films in the zone-annealing process are discussed in the present paper.