Marie-Alice Rousselle

Cotton Fiber Chemistry and Technology

Cotton fiber chemistry and technology , Cotton fiber chemistry and technology , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

The Iodine Sorption Test. Factors Affecting Reproducibility and a Semimicro Adaptation

The iodine sorption test is a convenient though empirical method of measuring cellulose accessibility, but results show considerable variability. The relative importance of some experimental factors with respect to reproducibility of test results was, therefore, examined. Agitation during equilibration and use of a standard concentration of iodine solution and a standard sample weight were shown to be important. A fixed shedule of equilibration times and some degree of temperature control are also necessary. No increase in precision was obtained by direct titration of iodine in the sample, compared to the usual indirect determination by titration of supernatant solution and blank. The procedure can be scaled down from the usual 300-mg sample to 60-mg samples without loss of precision.

Enzymatic treatment of lyocell - clarification of depilling mechanisms

We have characterized cellulose from the original structure of a lyocell fabric, from pills mechanically removed from the surface with a razor blade and from cellulose microfibrils removed from the surface and dispersed in the liquor during a cellulase depilling process. We find that cellulases first attack the cellulose from the microfibrils on the surface of the fabric because they are more externally exposed than the cellulose of the original fabric structure and have the same characteristics in terms of molecular weight, polydispersity, and crystallinity index as the base fabric. Cellulose from the microfibrils removed from the base fabric by the cellulase and recovered from the liquor shows significantly increased polydispersity, therefore indicating that the microfibrils have been widely attacked by the enzymes. Cellulases prove to be thorough surface finishing agents, since they change only the fiber surface, not the crystallinity.

Determining the Molecular Weight Distribution of Cotton Cellulose: A New GPC Solvent

Dimethylimidazolidinone/lithium chloride (DMI/LiCL) is shown to be an effective solvent system for a variety of celluloses, including the high molecular weight cellulose of cotton, when a swelling pretreatment in sodium hydroxide is incorporated. DMI/0.5% LiCl is suitable for use as a mobile phase in gel permeation chromatography to determine the molecular weight of cellulose. The results of using the DMI/LiCl solvent system to determine molecular weight parameters (number-average, weight-average, and peak mo lecular weight) of a variety of celluloses (cotton, rayon, tencel, linen, ramie, flax, kenaf) are reported.

Molecular Weight of Cotton Cellulose: Effect of Treatment with a Total Cellulase

Cotton fabric is treated with a total cellulase preparation in either a Launderometer or a reciprocal water bath/shaker for times ranging from 10 to 180 minutes. Control fabrics, buffer-only treated fabrics, and cellulase-treated fabrics are analyzed by gel permeation chromatography to determine peak, weight-average, and number-average molecular weights. The GPC data are compared to weight loss and breaking load mea surements on control and treated fabrics. Despite considerable weight loss and breaking load reduction with the total cellulase treatment in the Launderometer, GPC analysis does not show a reduction in the molecular weight of the cellulose.

Reactivity and Fine Structure of Cotton Mercerized in Sodium Hydroxide or Liquid Ammonia

The effect of liquid ammonia mercerization on the fine structure and reactivity of cotton sliver and yarn was compared with that of sodium hydroxide mercerization. X-ray diffractograms showed considerable decrystallization by both swelling agents, with little difference between them, and no effect of tension. The swelling produced by both reagents decreased the density of the cotton, with the percentage decrease being dependent on tension, method of removing the swelling agent, and fiber maturity, rather than on type of reagent. Accessibility to moisture, deuterium exchange, and iodine was increased by all treatments, but in general, increases with caustic soda were greater than with ammonia. Differences in enhanced reactivity towards acid hydrolysis and crosslinking with formaldehyde, attributable to mercerizing agent, were small, but in partial acetylation, greater reactivity resulted from caustic mercerization.

Properties of Durable-Press Cotton Fabrics Related to Swellability

Fabrics with a wide range of durable-press properties were prepared by treating cotton printcloth with dimethyloldi hydroxyethyleneurea (DMDHEU) by pad-dry-cure, mild-cure, and steam-cure processes and with formaldehyde by vapor-phase, Form D, and Form W processes. Swellability in aqueous media, as measured by water retention, iso propanol retention, alkali centrifuge value, and yarn untwisting number, is discussed in relation to durable-press appear ance ratings and wrinkle recovery angles. Such measurements of accessibility as moisture sorption isotherms, internal surface area, iodine sorption, and differential dye sorption are also presented. Some inferences regarding spatial location of crosslinks and its relation to wet and dry fabric recovery properties are discussed.

Cotton Fiber Properties and Moisture: Water of Imbibition

Southern Regional Research Center (SRRC) is participating in a multi-year area-of-growth study of selected cotton cultivars. We report here preliminary moisture data (water of imbibition) on the cottons from the 2001 crop year, and compare them to maturity properties determined by image analysis and to micronaire.

Effect of Purified Trichoderma reesei Cellulases on the Supramolecular Structure of Cotton Cellulose

Commercial cellulases may contain mixtures of different cellulase components, and properties of cotton fabrics treated with cellulases vary with the nature of these mixtures. This study reports the effect of treatments with cellulase monocomponents on the molecular and supramolecular structures of cotton cellulose. Desized, scoured, and bleached printcloth fabrics prepared from ring spun or rotor spun Deltapine cotton yarns are treated with monocomponent cellulases—endoglucanase I and II and cellobiohydro lase I and II from Trichoderma reesei—in an acetate buffer in stainless steel canisters in the presence of stainless steel ball bearings. The effects of the treatments are reported for fabric weight loss, reducing sugar formation, fabric breaking strength and tearing strength, copper number, water of imbibition, cellulose microstructure as revealed by hydrogen bonding patterns, and fiber pore size distribution.

Closed-Boll Cotton Part I. Properties of Never-Dried Cotton Fibers Before and After Aqueous Formaldehyde Treatment

Cotton lint from closed bolls harvested at various stages approaching maturity had very high initial moisture content, water retention, and dye sorption. Values decreased as fibers matured. Equilibrium moisture contents of never-dried cotton by desorption to 93 and 87% relative humidity were much higher than those for rewet air-dried fibers. Tensile elongations of never-dried fibers were greater than those of rewet air-dried fibers only in the more mature samples. Under the condi tions employed, treatment of never-dried cotton with aqueous acidified formaldehyde solution did not preserve the very high sorptive properties.