Fibrillation-controlled lyocell fibers were developed by crosslinking reactions between dialdehyde cellulose (DAC) and multifunctional amines. DAC lyocell fibers were manufactured by partial oxidation with sodium metaperiodate and were successfully crosslinked with two multifunctional amines by Schiff-base formation. The amorphous regions and the char formations, which were characterized by differential scanning calorimetry and thermogravimetric analysis, increased with the degree of oxidation. After the crosslinking reactions, an increase in the amorphous regions also appeared, whereas the thermal stability was somewhat improved by the chain crosslinking. These results were in good agreement with viscosity-average degree of polymerization values in that they diminished with oxidation level and increased with the crosslinking reactions. The water retention value and moisture regain value decreased with the oxidation and crosslinking levels, which implied that the swellability of fibers and the water absorbency in characteristic sites decreased with them. The increase in the dry crease recovery angle also confirmed the presence of hemiacetal crosslinks in the DAC and amine crosslinks between the DAC and the amines. The fibrillation grade of the crosslinked fibers diminished with oxidation level and the amine concentration. In particular, the fibrillation properties of the crosslinked fibers with 4-hydroxy-2,4,6-triaminopyrimidine sulfate salt were more easily controlled than those of the crosslinked fibers with 2,4,6-triamino-1,3,5-triazine.
Antimicrobial nonfibrillated lyocell fibers were developed by crosslinking reactions between dialdehyde cellulose and chito-oligosaccharides. Partially oxidized lyocell fibers with sodium metaperiodate were successfully crosslinked with two water-soluble chito-oligosaccharides with different molecular weights by Schiff base formation and were reduced with sodium borohydride. Infrared spectroscopy measurements showed the characteristic absorption bands caused by the functional groups of each reaction product. The surface chemical compositions of the modified fibers were analyzed with electron spectroscopy. O 1s intensities decreased with the oxidation and crosslinking reaction, whereas N 1s intensities increased with the crosslinking reaction. According to the curve fittings, C 1s spectra were divided into ACH, ACOA/ACNA, AC¼ ¼O, and ACOOA peaks, and their relative peak areas confirmed the reaction results. The degree of fibrillation of the crosslinked fibers decreased with the oxidation levels and chito-oligosaccharide concentrations and increased with the molecular weight of the chito-oligosaccharide. Furthermore, the chito-oligosaccharide-treated lyocell fibers exhibited antimicrobial activity, especially when treated with a chitooligosaccharide of a low weight-average molecular weight.
Four different kinds of wood pulp are used to make lyocell fabric and its intermediate products, and each is evaluated in terms of its physical characteristics and fabric hand values measured with the Kawabata Evaluation System for Fabrics. The rank orders of fiber, yarn, and fabric characteristics as a whole suggest that H4 pulp is ranked highest for its physical characteristics, thus producing textile intermediates with higher strength and dimensional stability than the other pulp types. Comparing such physical results with the KES-FB rank orders, it appears that high strength and stability along with high elongation and crimp factors are less significant for characterizing fabrics with higher hand values. For lyocell fabrics made from yarns with higher CV%, the results are more favorable for increasing the hand values of numeri, fukurami, sofutosa, and shari characteristics, and such fabric hand as a total is an important requirement for women’s suit fabrics.
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