Experimental determination of the fiber orientation parameters and the Raman tensor of the 1614 cm−1 band of poly(ethylene terephthalate)☆

Abstract Polarized Raman spectroscopic measurements were performed on uniaxially oriented fibers of poly(ethylene terephthalate). The diagonal Raman tensor for the 1614 cm −1 band along with the second- and fourth-order coefficients of the orientation distribution function are determined from the Raman scattering intensities as a function of spin-speed. The development of an oriented-amorphous material within the fiber is explained. The elements of the Raman tensor appear to vary as a function of spinning speed. This observation calls into question the use of isotropic values for the Raman tensor when determining the orientation.