On-Line Estimation of Molecular Orientation in Polypropylene Fibers Using Polarized Raman Spectroscopy

Polarized Raman spectra obtained at different points along the spin line during pilot-scale melt spinning of polypropylene fibers are presented for the first time. Measurements of the 841/809 cm −1 band intensity ratio for these fibers with varying draw are made and shown to correlate with birefringence. The effect of sample throughput and take-up velocity on real-time polarized Raman spectra of these fibers is also discussed. On the basis of the results obtained it is confirmed that the ratio of the 841/809 cm −1 band intensities can be used to estimate the molecular orientation in polypropylene fibers.