Orientation of cellulose crystallites in regenerated cellulose fibres under tensile and bending loads

Abstract

The degree of orientation in regenerated cellulose fibres with a diameter of 36lm was determined using position-resolved synchrotron X-ray microbeam diffraction. The fibres were characterized in unstrained condition, under tensile strain, and in bending. A homogeneous distribution of the degree of crystalline orientation (Herman's orientation factor f c = 0.85) across the fibre thickness was found in the unstrained fibre. The degree of orientation of cellulose crystallites increased in a linear manner with increasing tensile strain applied to the fibre. Also in bending, a linear relationship between applied strain and the degree of crystalline orientation was found, where f c increased in tension and decreased in compression. This linear relationship was found to be valid for both the tensile and the compressive zone of the bent fibre.

Reorientation of crystalline and noncrystalline regions in regenerated cellulose fibers and films tested in uniaxial tension

“…However, because of their specific cell‐wall architecture, with cellulose fibrils winding around the central fiber cavity in a spiral fashion, natural cellulose fibers are only of limited use as reference for (synthetic) regenerated cellulose fibers. With the exception of Northolt and de Vries12 who report birefringence measurements, only data on the orientation of the crystalline fraction in regenerated cellulose fibers7–9 and cellulose composite films10 are available. In ref 9,.…”

“…data on the relationship between fiber stress and crystalline orientation are presented, and it is thus difficult to interpret these results with regard to the relationship between fiber strain and orientation. All other studies cited (refs 7,8,. and10) observed a linear relationship between applied strain and molecular orientation.…”

“…That is, flax,2, 3 coir,4 thin slices of wood,3, 5, 6 and single wood fibers5 using X‐ray diffraction (XRD) technique. Wide‐angle XRD experiments with strained regenerated cellulose fibers7–9 and cellulose composite films10 also demonstrated the reorientation of crystalline regions upon straining. In a recent study, it was shown that the mechanical performance of regenerated cellulose films can be greatly improved by stretching in wet condition and consecutive drying 11…”

Analysis of regenerated cellulose fibers with ionic liquids as a solvent as spinning speed is increased

“…The orientation parameter cos 2 u hkl of regenerated cellulose was evaluated from WAXD 2D detector images according to the method reported in the literature (Gindl et al 2006).…”

Alkali Treatments of Woven Lyocell Fabrics

“…A system with compact fiber core, a porous middle zone and a semi-permeable fiber skin. However, Gindl et al (2006) showed that only two different parts within lyocell fiber do exist, skin and core. They observed that studied fibers have uniform skin-core orientation, in contrast, Kong et al (2007) obtained non-uniform skin-core orientation by X-ray diffraction as claimed due to the differences of used beam size (5 × 5 µm vs. 500 nm).…”