Morphological analyses of polybutylene terephthalate by terahertz time-domain spectroscopy

A characteristic feature around 2.38 THz in the real and the imaginary part of the permittivity or alternatively the absorption coefficient and refraction index is a good indicator of the degree of crystallinity in polybutylene terephthalate (PBT). We assign this spectral feature to macromolecular origin, based on the comparison with polyethylene terephthalate (PET). Furthermore, the refractive index behavior reveals more insight about the morphology affected by thermal treatment of the samples under test.