Structural Analysis for PET Fiber using Laser Raman Microprobe Spectroscopy.

Abstract

Polarized Raman spectra for the various types of poly(ethylene terephthalate) fibers were measured using microprobe spectroscopy changing the optical systems, and the conditions suitable for the estimation of density and molecular orientation of the fibers were discussed. For the estimation of density, the full width at a half maximum of 1730 cm-1 band measured under the laser polarization direction parallel to and Raman polarization direction perpendicular to the fiber axis was most convenient. For the estimation of molecular orientation, the parameter using the ratio of relative Raman intensities, that is (I1615 / I632)/(I1615 / I1730) which showed the highest correlation coefficient against birefringence, was suitable: Here, I1730, I1615 and I632 are the intensity of 1730cm-1, 1615cm-1 and 632cm-1 bands, respectively. The relative intensity, I1615 / I632, was measured under both laser polarization and Raman polarization in the direction parallel to the fiber axis, and I1615 / I1730 was measured under both laser polarization and Raman polarization in the direction perpendicular to the fiber axis.