Changes in the intra- and inter-fibrillar structure of lyocell (TENCEL®) fibers caused by NaOH treatment

Abstract

Some effects of NaOH treatment at concentrations of up to 8 M on (1) the porous structure, (2) the degree of swelling, (3) carboxyl content using methylene blue sorption and 9H-fluoren-2-yl-diazomethane (FDAM) methods, (4) dyeing, (5) the molecular weight distribution measured by gel permeation chromatography (GPC), (6) crystallinity determined by wide angle X-ray diffraction (WAXD) and (7) the tensile properties of lyocell fibers were investigated. The porous structure of fibers was visualised using fluorescence microscopy and transmission electron microscopy (TEM) on fiber cross-sections and was also studied by inversion size exclusion chromatography (ISEC). Mean pore diameter and pore area of fibers were not changed by NaOH treatments. The pore volume increased above 2.5 M NaOH. NaOH-treated samples showed higher dye uptake, higher swelling, but lower carboxyl and moisture content and increased crystallinity. As the NaOH concentration increased, the depth of colour following dyeing with C.I. Direct Red 81 also increased due to deep penetration of alkali into the fiber. In general, fiber properties were distinctly different in the ranges 0 to approximately 3 and 3-8 M NaOH.

Characterization and mechanical properties investigation of the cellulose/gypsum composite

“…Water retention value is an ability of cellulose to uptake water. [34][35][36][37] In water or under alkali treatment of 2-4 M NaOH cellulose II can swell extensively in comparison to cellulose I. 36,37 On the other hand under strong alkali treatment, e.g.…”

Properties of cotton fabrics treated by protease and its multienzyme combinations

“…13,25 Despite a higher packing density of the amorphous regions due to the removal of cementing materials, 30 the widening of underlying cavities and increased absorbance capacity was reported for cellulosic textiles with higher CrI values. 31 Whiteness was the property most affected by treatment of fabrics with Alcalase. Increased WI values were obtained after scouring with protease and its combinations.…”

Alkali and Peroxide Bleach Treatments on Spring Harvested Switchgrass for Potential Composite Application

“…Strong alkali solutions are capable of altering the crystal structure of cellulose, causing an irreversible conversion from cellulose I to II, due to the changes in crystallite length and packing order (El Oudiani et al 2012). Most of the structural changes that happen to the fiber have been reported to occur after neutralization and drying (Ozturk et al 2009). Alkali solutions cause swelling of the fiber by cleaving hydrogen bonds and rearranging the configuration, which in turn reduces the crystallinity.…”

“…Alkali solutions cause swelling of the fiber by cleaving hydrogen bonds and rearranging the configuration, which in turn reduces the crystallinity. However, the neutralization and drying process changes the porosity and increases crystallinity after regenerating the cellulosic fibers (Ozturk et al 2009). …”