The Theory of Shrinkproofing of Wool: Part V: Electron and Light Microscopy of Wool Fibers after Chemical Treatments

Abstract

Lincoln 36's top, subjected to ten different cheniical treatments as described in previous publications of this series [4, 51, was examined by light and electron microscopy using replica and thin-sectioning techniques. The sectioning and staining technique proved useful in showing the extent of penetration of the fiber by the reagent. T h e more drastic treatments such as 5% sodium hydroxide in water, hydrogen peroxide (10 vol for 16 h r ) , and severe treatment with chlorine (16% on weight of wool) caused almost complete obliteration of cellular detail throughout the fiber. Milder oxidation treatments may not have destroyed cellular detail, but may have oxidized sufficient disulfide bonds to prevent the TGA-Os04 staining procedure from staining the matrix, witli the result that the fine structure of microfibrils and matrix in the cortex were not visible. Alternative section staining procedures utilizing permanganate or lead hydroxide were also useful.LIodification of the cuticle was observed after every treatment which effected shrink-. proofing; namely, acid chlorination, treatment with permonosulfuric acid, hydrogen peroxide, sodiuni hytlroxide, and treatment with permanganate in saturated salt. Some treatments (ethanol extraction, for example) produced a marginal degree of shrinkproofing and showed a small amount of cuticle modification. Other treatments (with peracetic acid, for instance) did not modify the cuticle and did not effect shrinkproofing. Thus, the primary requirement for shrinkproofing by degradative chemical treatments is sufficient modification of the fiber cuticle. T h e chemical reaction by which cuticle modification (and thereby shriiikproofing) is hrought allout generally involves cystine, but with the use of ethanolic sodium hytlroxitle the major process is probably the removal of a \vool wax constituent from the cell nienil~rane complex beneath the cuticle. Although modification of the cortex by chemical reaction is undesirable from a practical point of view, it has only a secondary effect on the degree of shrinkproofing. Various methods of confining the reaction to the cuticle are discussed. I n particular, it was found that sodiiim hytlrositle in water penetrates throughout the fiber, whereas the reaction \\-as limited to the cuticle by the use of sodium hydroxide in ethanol or in a n aqueous solution saturated with salt. Similarly, reaction of the cortex occurred with permanganate in water (with no subsequent shrinkproofing) , whereas the presence of salt limited the reaction to the cuticle, thus producing shrinkproofitlg. The correlation between cuticle modification (hence degree of shrinkproofing) and alteration of frictional coefficients was good in most cases, but the lack of correlation in a few cases emphasized the importance of a new approach to the nleasurenient of frictional coefficients. NUMEROUS studies 011 striictiiral changes produced by cheinical agents for shrinkproofing in \\.o01 workers to observe alterations, particularly at the fiber surface, resulting from degradati...

New Enzyme-based Process Direction to Prevent Wool Shrinking without Substantial Tensile Strength Loss

“…These results are in line with those of other authors (Bradbury et al 1963): with the set of parameters applied no major diffusion of peroxide into the fiber interior, with subsequent severe fiber damage (weight and tensile strength), could be observed. This phenomenon has been explained by the fact that swelling of wool under those circumstances is suppressed (Simpson 2002).…”

“…It was already shown in 1963 by Bradbury et al (1963) that use of high concentrations of salt prevents diffusion of agents into the interior of wool fibers. This technique has been combined with the hydrogen peroxide pretreatment at different pH values, which was followed by enzymatic incubation using different time windows.…”

The Impact of Nitrogen Plasma Treatment upon the Physical-Chemical and Dyeing Properties of Wool Fabric

“…The outer surface, the cuticle cells, are hydrophobic in nature due to the presence of proteins with a high cystine-disulfide content along with the covalently bound fatty acid, monolayer on the fiber surface, thereby acting as a surface barrier against diffusion and penetration of dyestuffs and finishing agents into the wool-structure [3,4] . Much attention is being focused on replacement of traditional chemical treatments [3,[5][6][7][8] with more environmentally friendly processes [1,4,[9][10][11][12][13][14] i.e., with low-or zero-effluent processes, to upgrade the quality and to enhance the performance properties of wool fabrics.…”

Some New Observations on the Effects of Mild Shrinkproofing Treatments on Wool Fibers

“…That the treatment produces a change of some kind in the scales can be demonstrated more easily by staining with methylene blue, which the scales retain more tenaciously-after treatment. Changes in the scale shape have been detected by electron microscopy [2,7]. It is clear that some changes do occur in the scales during treatment, but it has been considered [26] that these changes are inadequate to account for the reduction in feltability of the wool.…”