Volume 43, Issue 1 (January 1998)
Characterization of Fibers by Raman Microprobe Spectroscopy
A set of fibers, mainly synthetic, has been examined by Raman microprobe spectroscopy. It was found that high quality spectra, requiring no sample preparation, are easy to obtain and that fibers with different molecular structure have very different Raman spectra. Fluorescence was occasionally a problem with excitation at 632.8 nm, but could be significantly reduced by using a semiconductor laser emitting at 780 nm. Fibers of the same polymer type from different manufacturers have Raman spectra which are only slightly different but which could be distinguished by the multivariate statistical technique of principal components analysis (PCA). Dyed fibers gave spectra with bands due to the polymer, but also with intense bands due to the dye, because of the high Raman cross-section of dye molecules. Extraction of the dye, followed by a spectral subtraction procedure allowed separate spectra of the polymer and the dye to be obtained.