Deformation Processes in Regenerated Cellulose Fibers

Molecular deformation processes of regenerated cellulose fibers are investigated using Raman spectroscopy. These fibers have well-defined Raman spectra, and the main Raman bands in the region of 895 to 1170 cm -1 shift to lower wavenumbers upon application of tensile strain and stress. The peak positions of the Raman bands at 895 and 1095 cm -1 show an approximately linear relationship with strain and stress. For fibers with lower moduli and more nonlinearity in their stress-strain curves, there is poorer correlation with strain and stress, consistent with mechanical data and structural characteristics. Also, the strain sensitivity of the Raman band strain shift (in cm -1 /%) increases with the Young's modulus of regenerated cellulose fibers, and there is a universal stress band shift of about -4 cm -1 /GPa for both bands, consistent with a modified series model of deformation. Deviations from this model for lower fiber moduli are discussed with evidence to suggest that chain slippage and re-orientation behavior dominate.