Correlation between crystallinity and some infrared bands in the spectra of syndiotactic poly(propylene)

Abstract

Films of syndiotactic poly(propylene) were obtained by quenching the melt to different temperatures, that is 0, 30, 50, and 100°C. Some films were aged at room temperature for 1 month. All the samples crystallised in the disordered Form I, containing also a fraction of mesophase. The crystallinity was derived from the X-ray diffractograms, and the fraction of mesophase from the sorption properties. In the infrared spectra of all the samples, the bands of the helical conformation were identified and correlated with the crystallinity. The bands at 810, 868, and 1 005 cm–1 showed a good linear correlation with this parameter. With respect to variance, for the band at 977 cm–1 there was no simple correlation; therefore we assumed that this band is sensitive to both the crystallinity and the fraction of mesophase. Using the values of crystallinity, derived from X-ray, and the fraction of mesophase, derived from sorption measurements, we obtained the contribution of each phase to the total absorbance of the band at 977 cm–1.