The comfort in wear of textiles has been studied extensively on the level of textile construction. The influence of the fibre material is present in the experience of textile consumers, but objective assessment is rather difficult. Some recent works are reviewed here. TENCEL 1 is a man-made cellulosic fibre of the generic fibre type lyocell. The background of the special comfort in wear of textiles made from TENCEL 1 fibres is explained as a consequence of the fibres' water-absorbing nanostructure. The basis for these properties are found in the high absorption of water and water vapour, which leads to high heat capacity and heat balancing effect for thermoregulation, comparable with the action of phase change materials. The thermal wear properties resulting are the cool and dry touch, the active cooling effect in sports wear, and the warming properties when used as an insulation layer. These effects are to a certain extent adaptive to the environment, providing comfort in a wide range of climatic conditions. Moreover, neutral electric properties, retarded bacterial growth and good skin sensory perception add to the overall skin friendly properties, which were also shown in wear studies with patients suffering from skin diseases.

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.

ABSTRACT:The internal porous structures of the manmade cellulosic fibers Lyocell (TENCEL 1 ), Modal, and Viscose fibers were visualized by applying fluorescence microscopy on fiber cross sections. The fiber pore structure was probed by the optical brightener Uvitex BHT, and the dye penetration depth was measured. The main differences in the pore structures of these three fiber types could be visualized. Only TENCEL shows a significant difference between dried and never-dried fibers. A fiber structure model of TENCEL was obtained, which discriminates three different porous zones with respect to dye diffusion kinetics. The results are discussed in relationship with the fiber physical and chemical properties. The dye penetration depth and kinetics in TEN-CEL fibers was found to be sensitive to the production and treatment conditions, in particular to changes in the pore system by drying, and following alkali swelling processes. The performance of surface-specific enzymatic peeling could also be observed.

The reorganization of cellulose fibers by swelling treatments in alkali solutions results in numerous changes to fiber structure, causing changes of chemical reactivity in the fiber‐solution heterogeneous system. An important part of the change in chemical reactivity is the change of fiber accessibility because it results in exclusion of chemicals such as reagents or catalysts from the fiber. In the second of a two‐part series of papers, we examine the influence of changes in fiber accessibility and/or reactivity due to treatment in swelling solutions on the performance or behavior of substrates during and after chemical finishing treatments. Changes in fiber accessibility due to alkali treatments are visualized with fluorescence microscopy. The effect of alkali treatments on enzymatic hydrolysis and pad‐dry‐cure crosslinking treatments of cellulose substrates are discussed as representative examples to demonstrate the effects of swelling processes on fiber reactivity and accessibility. Model calculations indicate that a considerable redistribution of chemicals in substrates occurs during dry‐cure operations resulting from molecule‐specific exclusion effects. Pilling tests on lyocell knit‐fabrics show the impact of preceding alkali processes on the final physical performance of textile fabric highlighting the importance of correct selection of alkali processes to achieve desired behavior.

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