A study of molecular orientation in drawn and shrunk poly(ethylene terephthalate) by means of birefringence, polarized fluorescence and X-ray diffraction measurements

Stretching of PET films under constant load. II. Structural analysis

“…However, Nobbs et al 5 showed that, up to a level of amorphous orientation equal to 0.4, the density of the amorphous phase of PET does not exceed 1.342, i.e., a variation less than 0.556, which is negligible for the determination of crystallinity. Figure 1 shows the evolution of the axial birefringence with the draw ratio:…”

Infrared spectroscopic characterization of oriented polyamide 66: Band assignment and crystallinity measurement

“…4 It is uncertain how changes in the amorphous orientation might affect the amorphous density. A crude model by Ward et al 12 indicates that little change in density occurs until the amorphous orientation reaches about 0.45, and experimental data on PET film and fibers tend to confirm this. 13 Infrared spectroscopy has been used to some extent in the past to measure crystallinity, but this was done by calibration against another method.…”

A study of tensile modulus and molecular orientation in drawn and shrunk poly(ethylene terephthalate) combining refractive index, polarized fluorescence, and X‐ray diffraction measurements

“…The results of this study suggested that the shrinkage of PET is primarily associated with disorientation of the amorphous regions and that crystallization occurs at a later stage in the shrinkage process rather than being the predominant mechanism of shrinkage per se. 2 In the present paper, which is concerned with uniaxially oriented samples (as were Refs. 1-3), we describe a study of the changes in Young's modulus of PET due to drawing and subsequent shrinkage.…”