Dynamic infrared spectra of uniaxially drawn poly(ethylene terephthalate) (PET) under a sinusoidal strain were examined. A very intense dynamic band at 973 cm−1 assigned to the trans C-O stretching mode indicated stress-induced high mobility around the C-O bond in the ethylene glycol units. It was supposed that derivative-like skeletal bands observed in the dynamic spectra originated from the stress-induced frequency shift. Two-dimensional correlation analyses of the dynamic spectra were also carried out and revealed that the phenyl ring 18a band at 1018 cm−1 and the phenyl ring 19b band at 1410 cm−1 were composed of three and two independent components, respectively. The correlation peaks between the phenyl ring and CH2 vibrational modes showed that orientation of the methylene group in the ethylene glycol unit, induced by mechanical stretching, is faster than that of the phenyl ring in the terephthalate unit.

No abstract

A method of data manipulation using the dynamic magnitude spectrum and the static absorbance spectrum is applied to uniaxially drawn poly(ethylene terephthalate) films with five different draw ratios for the evaluation of the amplitude of dynamic structural changes under a sinusoidal strain at the level of a functional group. This analysis revealed that, in the drawn film, the skeletal structures, such as the C–O bond in the ethylene glycol unit and the phenyl ring, are susceptible to deformation by mechanical stretching, while the dynamic structural changes around the methylene group are small. It was assumed that the backbone of the polymer is responsible for the change of the mechanical properties induced by the drawing of the film.

Dynamic FT-IR spectra of uniaxially 5×-drawn poly(ethylene terephthalate) (PET) film at a temperature of 30 to 150 °C were measured with the use of a variable-temperature polymer stretcher, and amplitude spectrum analyses of the dynamic spectra were carried out. A drastic decrease in dynamic variations of the trans C–O stretching band was observed above the glass-to-rubber transition temperature. This observation suggests that the trans C–O bond in the ethylene glycol unit is closely related to changes in macroscopic mechanical properties of PET film in the glass-to-rubber transition.