Determination of crystalline lamellar thickness in poly(ethylene terephthalate) using small-angle X-ray scattering and transmission electron microscopy

The crystalline lamellar thickness of semicrystalline poly(ethylene terephthalate) (PET) was evaluated using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) techniques. Both SAXS one-dimensional (1D) correlation function and interface distribution function analyses were utilized to determine the crystalline lamellar thickness. The two-dimensional fast Fourier transformation (2D-FFT) of the TEM image and the Gaussian-like lamellar thickness distribution determined from the TEM image were also performed. Results indicate that the larger value of the two correlation lengths calculated from the SAXS analysis should be assigned to the crystalline lamellar thickness in PET. Discussions and comparison among different methods for characterizing the lamellar thickness of semicrystalline polymers are made.