Structural differences in regenerated cellulose fibers produced using Viscose and Lyocell techniques*

We compare the structural features of regenerated cellulose fibers manufactured using Viscose and Lyocell processes. It is known that these fibers possess different surface morphologies. However, there is not much information on nanoscale structural features e.g. microvoids, lamellar structure etc. We show using small angle x ray and ultra-small angle neutron scattering that the fibers possess elongated microvoids, oriented in the fiber direction. We analyse 2D SAXS data using Ruland’s equatorial streak method and obtain average length and average misorientation of the microvoids in both fibers. Using Porod’s law and invariant calculated from the combined SAXS and USANS measurement, we evaluate the radius. We show that Lyocell fibers have bigger, better orientated voids than Viscose fibers. There are also differences in the crystal structure of these two fibers. Scattering from Viscose fibers show evidence for lamellar stacking in the fiber direction whereas, that from the Lyocell fibers is qualitatively different and does not show stacking. This shows that process differences strongly affect the microstructure of the fibers at length scales of few nanometres.