The Influence of Polybutylene Terephthalate Cross-Linking on Infrared Spectra

The attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) spectra of the samples of polybutylene terephthalate (PBT) with varying spatial densities of cross-links are obtained. The changes are primarily observed in the fingerprint region. The ratios of the area of the absorption bands 810/794 and 917/935 cm^–1 bands are shown to decrease with increasing degree of cross-linking and can be used to assess it. The changes in infrared absorption are linked to the difference in the bending frequency between the crystalline and amorphous phases of PBT. The latter is more prevalent in the densely cross-linked samples.