Isuke Ouchi

Hygroscopic Expansion of Polyester Films

The hygroscopic expansion of polyethylene terephthalate (PET) and polyethylene 2,6-naphthalate (PEN) films was measured by use of a thermomechanical analyzer at 30, 40 or 50°C. Their initial weight increase was proportional to the square root of time after exposure to moisture, obeying Ficks law; the hygroscopic expansion with time showed the same relationship. The equilibrium moisture content was 1.0×10-5/% RH for both films; the hygroscopic expansion at equilibrium was also about the same for these films. However, the diffusion constant for moisture in PEN films was 16×10-9 cm2/s at 30°C in comparison with 48×10-8 for PET, although the activation energies were 45 kJ/mol for PET and 41 for PEN.

Structure and Core Electron Absorption Spectra of Polyester Films

Soft x-ray absorption spectra of oriented films of polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) of several tenth micron in thickness were measured by a transmission method. A similar resolution and the same dependence on the beam incident angle as obtained by a total electron yield method were observed in the oxygen K-edge region, but not in the carbon K-edge. IR spectra of the thin oriented sample films utilized in these measurements indicated their aromatic rings to be parallel to the film plane as found in the thick PET and PEN films. This fact conformed to the spectral change near the oxygen K-edge and gave a further support of the peak assignments made previously. The spectral behavior near the carbon K-edge was interpreted by the saturation effect which was due to the presence of greater number of carbon atoms in a repeat unit than oxygen atoms, and partially by strayed light effects.

Effects of Infrared Exposure on Stress Relaxation in Polyester Films

Undrawn and drawn polyester films were stretched by 1% between the clamps of a tensile tester, and the effects of infrared exposure on the stress relaxation were observed. Upon exposure for 5 s, the stress deceased sharply, and after stopping, it recovered nearly to the extended level of the original stress relaxation, except for the uniaxially drawn films stretched along the machine direction which showed a complex behavior.

Dynamic Mechanical Behaviour of Thin Metal-Layer Coated Polyethylene Terephthalate Films under Torsional Oscillation

Co-Cr or Ni thin layers were deposited on both sides of a polyethylene terephthalate (PET) film by sputtering. Complex rigidity moduli of these films were measured by a torsional oscillation method under a load of 6.8×105 Pa between room temperature and 200°C. The real and imaginary parts of the complex moduli of the coated films were explainable, qualitatively, in terms of those of the base film and thin metal layers using a simple composite model. The loss moduli of Co-Cr layers were small, as previously shown by a nonresonant, forced stretching oscillation method, while those of Ni were definitely greater in the temperature range above 130°C. Cracks occurred in Ni above 165°C and in Co-Cr at higher than 180°C under the minimal load mentioned above.