Mature Cotton Fibers Research Articles

Scanning Microscopy of Wax Removal from Bioscoured Cotton Textiles

The cotton textile fiber is a field dried, single cellular, collapsed convoluted tube. It is covered with waxes, which are connected by ester linkages to pectins enmeshed in a basket weave structure of the cellulosic primary wall. Depending upon its variety, the mature cotton fiber contains between 0.5%and 1% wax by weight, and it is practically waterproof. The normal industrial method for cleaning cotton fabric involves three steps: de-sizing with amylase enzymes to remove starch sizing or boiling in an aqueous surfactant solution to remove polyvinyl alcohol (PVA) sizing; scouring with caustic soda to remove waxes; and bleaching with hydrogen peroxide to obtain uniform whiteness. The effluent from this process is environmentally toxic, but the process is necessary to prepare fabric for dyeing, durable press finishing, etc. Current research is directed towards the investigation of environmentally friendly methods of removing cotton waxes.

Single Fiber Strength Variations of Developing Cotton Fibers: Among Ovule Locations and Along the Fiber Length

This paper, the first in a series on variations in single fiber properties of developing and mature cotton, focuses on single fiber tensile property variations of greenhouse-grown developing G. hirsutum (Maxxa variety). Variations along single fibers and among locations on ovules are examined on developing and mature cotton fibers sampled from ovules located in the middle of the locules of the first-position bolls. The breaking force and elongation of the midsection of the fibers from the medial portion of these ovules, in either hydrated or dried state fibers, show the most significant increases during the fourth week of development. As fibers develop beyond 30 dpa, the single fiber breaking forces, linear densities, and tenacities become scattered. The forces required to break the mid- sections of the single fibers are highest, while the breaking forces for fiber sections closer to the basal or tips are similarly lower at all stages of development. Fibers from the medial sections of the ovules have the highest tenacities, followed by those from the micropylar and chalazal ends. Of the mature fibers, the ribbon widths of fibers from the medial sections and the micropylar ends of the ovules are similar, but the medial sections are higher than the micropylar ends. Fibers from the chalazal ends are narrowest and have the lowest linear densities. The tenacities of single fibers from the medial regions of the ovules are higher than those from the chalazal and micropylar ends, the latter two being similar. Ultimate fiber tensile properties are reached in the developing fibers by 30 dpa; further fiber development contributes to thicker cell walls and thus to fiber mass, but not to intrinsic fiber strength.

Variability of Malate Dehydrogenase among Cotton Cultivars with Differing Fiber Traits

Little is understood about the biochemical basis of differences in quantitative traits of cotton (Gossypium hirsutum L.) fiber. Malate dehydrogenase (MDH) is implicated as an enzyme that may have effect on extension growth during the development of cotton fiber. Our objectives were, first, to determine if variability among cultivars exists for MDH, and, second, to determine if variability in MDH can be correlated with quantitative traits of fiber. Twenty‐four cultivars G. hirsutum were chosen. Polyacrylamide gel electrophoresis was used to search for MDH allozyme variation in etiolated cotyledons. Additionally, MDH activity in developing fiber was measured. All cultivars were grown in 1990 at two sites near Stoneville, MS. At 12 days post anthesis (DPA), immature bolls were harvested and the fiber separated from the ovules. An extract was prepared from the fiber and assayed for MDH activity and protein concentration. Other bolls were allowed to mature and open naturally, and from these bolls fiber was taken and tested for eight traits: elongation, maturity (ratio of wail thickness to fiber diameter), micronaire reading (fiber fineness), perimeter, 2.5 and 50% span length, strength, and wall thickness. Allozyme variation for MDH was not detected. The MDH specific activity ranged from 13.8 to 18.8 µmol NADH min−1 mg−1 protein, with a mean of 16.4 μmol NADH min−1 mg−1 protein in 12 DPA fiber. Variation among cultivars for MDH specific activity and all fiber traits was significant (P < 0.05). Though implicated in extension growth, MDH specific activity was not correlated with the length of mature cotton fiber. Only correlations between MDH specific activity and three traits of fiber walls (maturity, r = −0.476; micronaire, r −0.469; and wall thickness, r = −0.475 were significant. Cotton cultivars vary significantly for MDH activity in developing fibers and high MDH activity is indicative of low micronaire reading, thin fiber walls, and decreased maturity.

Accessibility and Lateral Order Distribution of the Cellulose in the Developing Cotton Fiber1

Cotton fibers from bolls harvested at 5-day intervals beginning at 20 days after flowering and ending at 50 days ( when the bolls had opened on the plant) 'were preserved in three ways for study in the never-dned state. Preservation was accom plished in 70% aqueous ethanol, 50% aqueous dioxane, and by freezing. Measurements of iodine sorption, red-green ("differential") dye uptake, and liquid-phase deuteration rehydrogenation gave different kinds of estimates of accessibility. These data were interpreted as indicating a relatively open structure during the 20- to 30-day period of growth, and a consolidation of the cellulosic component of the cell wall during the subsequent period of wall-thickening (35 to 45 days after flowering). There was only a small change in magnitude of these data upon boll opening. The leveling-off D.P. was nearly constant from the 30th to the 45th day, but showed a slight decrease after boll opening. Lateral order distribution was assessed by treatment with sodium hydroxide solu tions of increasing concentrations, followed by moisture sorption measurements and x-ray evaluation of extent of lattice transformation. The data indicated perhaps a slight increase in lateral order from 20 to 30 days after flowering, then a leveling-off from 30 to 45 days and a small increase upon boll opening at 50 days. These data are interpreted as indicating that the high crystallinity of the mature cotton fiber does not suddenly appear when the fiber first dries as the boll opens, but begins to develop concurrently with the deposition of cellulose during the period of wall thickening, and reaches the final high value by crystallization of an additional small fraction of cellulose upon initial drying.

Crystalline state of cellulose in fresh and dried mature cotton fiber from unopened bolls as studied by x‐ray diffraction

AbstractThe crystallinity of cellulose in the undried cotton fiber, fresh from the unopened but mature boll, was studied by x‐ray diffractometer methods and compared with the crystallinity of portions of fibers from the same samples either dried directly or from which the water has been removed in various “indirect” ways calculated to better preserve the original structure including: (a) Solvent exchange, (b) freeze‐drying, (c) drying above the critical temperature of liquids and (d) drying after the cellulose of the wet fiber has been crosslinked. The difference in crystallinity observed between directly and indirectly dried fibers indicates that a crystallization process must take place during the direct drying of the water‐wet fiber. This crystallization process is promoted by the presence of water and inhibited or prevented when the fiber is dried indirectly. An increase of the degree of crystallinity due to wetting can be explained by assuming that the crystallization, which had been suppressed in the indirectly dried fiber takes place subsequently upon drying of the rewetted fiber. That the indirect methods preserve entirely or partially, such amorphous structure as is originally present is confirmed by the lower density and higher dyestuff accessibility of such fibers.

Perimeter Measurements of Cotton Fibers in the Primary-Wall Stage

A method is described for obtaining information regarding perimeter differences of mature cotton fibers by measuring the perimeters of the fibers in the primary-wall stage. Tufts of young fibers were cut from the seed, stained, fanned out on a glass slide, and dried. The width of the collapsed dried fiber is equal to half its perimeter at the point measured. Perimeters were measured for 9 types of cotton, which had been selected to represent a range in size of perimeters. The average perimeter values obtained were compared to and found to show differences that were consistent with perimeter values obtained for the mature fibers of the same types of cotton.