Micro-Raman and Micro-FT-IR Spectroscopic Investigation of Raw and Dyed Pan Fibers

Micro-Raman and micro-FTIR spectroscopy were used to investigate raw and dyed polyacrylonitril (PAN) fibers with three different linear densities (3,6 and 9 den), dyed with three cationic dyes (red, blue and yellow) by standard procedure. The Raman and the ER spectra of the raw and dyed fibers as well as the corresponding spectra of pure dyes were analyzed. High quality spectra, both Raman and IR were obtained, requiring no sample preparation. Dyed fibers gave Raman spectra with bands characteristic for both the polymer and the dyes, while the IR spectra consist of predominantly bands due to the fiber polymer. Spectral subtraction procedures were used to separate the Raman spectra of the raw PAN fiber from the corresponding spectrum of dyed fiber and were then compared with the Raman spectra of pure dyes. The recorded Raman spectra of the three different linear densities of dyed fibers did not show variation in band frequencies, but in one dyed (blue) fiber, a regular variation in the band intensities was observed. This effect has been related to the quantity of the dye fixed on the (blue) fiber in three different linear densities. The results were compared with the quantity of the absorbed dye, previously determined for the blue fiber by colorimetric measurements. (doi: 10.5562/cca1888)