SynopsisBy impregnating cotton fiber with alkaline swelling agents and reacting with some chemical agents which can be substituted for the hydroxyl groups on cellulose molecules in the presence of alkali, highly accessible or decrystallized cotton fibers can be obtained. As the effective substitution reactions, acetylation by acetic anhydride and cyanoethylation by acrylonitrile were applied. The cotton fibers modified by these chemical treatments showed no decrease of tensile strength, and had moisture regain higher than the untreated cotton though the degrees of substitution were as high as 20-30 mol %. The resistance to heat or acid and the soil removal were improved. Dyeability for direct dye was increased, and dyeability for disperse or cationic dye was also given. Benzoylation and oleoylation were also investigated. Crease recovery of the cotton fabrics was somewhat improved and dyeability for disperse dye was given. The cotton fabrics oleoylated &r decrystallizing by alkali-acrylonitrile treatment had moisture regain almost the same as the untreated cotton, while high water repellency was given.

Microfibril orientation in a cotton fiber surface is measured by the fluorescence polarization method using microphotometry. To serve as a cotton model, drawn nylon fibers are dyed with a high concentration of fluorescent probe and subjected to a twist tester to obtain certain twisting angles, which are then quantitatively determined from the angular distribution of the polarized fluorescence intensity. For naturally dried cotton fibers, this fluorescence polarization analysis shows the twisting angle to be 24.5°. The method also permits analysis of the twisting sense of fibrils in the surface of cotton fibers without needing to untwist them.The structure and properties of cotton fibers have been studied intensively since the late 19th century. Many new findings have been reported by investigators in different countries. Even in this age of newly developed synthetic functional fibers, the structures of natural fibers are regarded as more sophisticated than what can be produced by human techniques.The orientation of cellulose fibrils in cotton fibers, Balls explained [ 3 ], is one of the important structural features in the mechanical properties of cotton fibers, which include tenacity, elongation, and elastic recov-ery. The convolution of cotton fibers occurs during the drying process after opening of the cotton boll [ 1 ] .

Cotton fabrics were chemically modified to allow transfer printing with disperse and cationic dyestuffs. Acetylated, cyanoethylated and styrene grafted cotton fabrics could be well transfer printed with disperse dye similarly to acetate and polyester fabrics. Light fastness was excellent, but durability to laundering was generally insufficient except acetylated cotton. As to cationic dyes, the printability was good for acrylic acid grafted cotton, fair for cyanoethylated cotton, but poor for carboxymethylated and acrylonitrile grafted cotton fabrics. Light fastness was generally good, but the fastness to laundering was almost poor.

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Field-opened American cotton fibers were treated with acrylonitrile after impregnation with aqueous sodium hydroxide. By this treatment the water absorbency and the amount of bound water as determined by DSC were increased and approached those of never-dried cotton. As for tensile strength, the increase in dry strength was higher than that of wet strength. On DSC cooling curves peak II , ascribable to freezable bound water, was observed as a small shoulder for field-opened and mercerized cotton fibers. However, this peak disappeared after the acrylonitrile treatment. Those treated fibers showed a nearly circular cross-sectional shape. Lumen and con volution could hardly be observed.