Structure Of Wool Fibers Research Articles

Development of novel parameters for characterising scale morphology of wool fibre and its correlation with dye diffusion coefficient of acid dye

This paper reports the development of novel surface parameters which can be used to characterise the scale structure of wool fibres obtained from different breeds. Scanning electron microscopy and subsequent image analysis technique were used to study wool fibres from Leicester, Dartmoor, Ryeland and Herdwick breeds of sheep. Novel scale parameters related to wool fibre’s effective chemical diffusion pathway were developed. Namely, the total scale perimeter per 100 µm fibre length and scale perimeter index, which is the total scale perimeter per 100 µm length divided by the fibre diameter. Wool fibres obtained from different breeds showed significant differences in their scale pattern with the change in fibre diameter. The scale perimeter per 100 µm length increased with the fibre diameter and showed a polynomial correlation. It was also demonstrated that an increase in the diameter of the wool fibre resulted in an increase in the apparent dye diffusion coefficient, which contrasts the established theory that finer fibres are associated with a higher dyeing rate. The increase in effective diffusion pathway (total scale perimeter per 100 µm) for the wool fibres (among different breeds) resulted in a higher dye diffusion rate at the initial phase of dyeing (liquor to surface).

Modification of wool fibre's structural properties as a cheap adsorbent for the elimination of Cr6+ and Rhodamine6g dye from aqueous solution

Wool, a naturally occurring biopolymer made up of amino acids, is employed as an adsorbent for both modified and unmodified forms of the dyes rhodamine6G (R6G) and Cr6+. The two-step procedure of (i) ring opening polymerization (ROP) and (ii) condensation reaction was used to modify the structure of wool fibre. Both the ROP and the condensation provide steric free chain expanding groups as well as adsorption-improving groups. The FT-IR spectrum, which showed peaks about 1725 and 1630 cm−1 corresponding to the CO and CN stretchings, respectively, confirmed the structural modification. By detecting a slight hump at 8.5 ppm, 1H NMR was able to validate the later functional group. DSC, TGA, FE-SEM, EDX, and water contact angle (WCA) were also used to characterize it. With the aid of a UV–visible spectrophotometer, the quantitative adsorption of both Cr6+ and R6G by modified and unmodified Wool fibre was monitored. For the adsorption of Cr6+ and R6G, the pseudo first order and pseudo second order kinetics were used. The multilayer coating of adsorbate onto adsorbent was confirmed by the Langmuir adsorption isotherm. Thermodynamic parameters were calculated and compared to values found in the literature.

The effect of glucose oxidase enzyme on wool fibres

AbstractGlucose oxidase is a type of enzyme that converts glucose into hydrogen peroxide and gluconic acid by enzymatic reaction. Glucose oxidase is widely used in industry; however, in the textile industry, glucose oxidase has only received academic interest. Previously, wool was bleached by some reducing agents; however, currently in industry, hydrogen peroxide dominates the bleaching of wool fibres. In this study, the effect of glucose oxidase enzyme treatment on wool merino fibres and dyeability properties was investigated. Wool fibres were treated with glucose oxidase enzyme, after which the whiteness index (Stensby) and yellowness index (ASTM D 1925 and ASTM E 313) were investigated. Scanning electron microscopy and scanning electron microscopy with energy dispersive X‐ray spectroscopy were used to identify the morphological structure of wool fibres and their atomic content. The chemical damage caused by enzyme was investigated using a fluorescence and a light microscope, and the alkali solubility (ASTM D 1283) was determined. After enzymatic treatment, the wool fibres were dyed at a 2.0% concentration with reactive dyes. Dyeability (K/S) and CIELab values were assessed with a Minolta CM 3600 D spectrophotometer (D65, 10°). The washing fastness of wool fibres was investigated according to TS EN ISO 105‐C06 (A1S).

Influence of liquid ammonia on the structure of wool fiber

Liquid ammonia treatment of worsted fabric was carried out by a continuous liquid ammonia finishing machine, and the effects of liquid ammonia on wool surface morphology, chemical structure and crystallinity were studied and corresponding mechanism was discussed in detail. The results showed that liquid ammonia made the surface scales of wool remove partially and decreased the content of hydrophobic lipid layer and hydrophobic property. After liquid ammonia treatment, the secondary structure of wool macromolecule was changed, manifested in increased α-helix and decreased β-sheet; the disulfide bonds were broken to form cysteine sulfonate, cysteic acid and cystine oxides. Liquid ammonia increased the content of α-crystallization, causing an increase in the crystallinity of wool. As our knowledge goes, this is the most systematic report to date on the effect of liquid ammonia on the structure of wool fiber, and provides a novel medium for the modification of wool in a large scale. Furthermore, it also provides a theoretical basis for the commercial application of liquid ammonia as a non-aqueous medium in wool textile industry.

Molecular genetics of wool fibre structure in sheep

Abstract Methods for mapping quantitative trait loci (QTL) are actively used in the sheep to identify chromosomal regions contributing to variation in wool traits. Therefore, this paper summarises and integrates QTL studies in the sheep to identify basic information on the genetic architecture of quantitative traits relating to wool’s important traits from viewpoint of the textile industry. The number of traits, number of QTL/associations and number of related chromosomes for categories of “Fibre” and “Fleece” were 6, 78 and 18, and 5, 97 and 23, respectively. QTL list and associated single nucleotide polymorphisms (SNPs) and genes relating to fibre curvature, fibre diameter coefficient of variance, fibre diameter standard deviation, mean fibres diameter, primary fibre diameter and primary fibre diameter coefficient of variance, fleece yield, greasy fleece weight, staple length, staple strength and wool crimp are presented. This information can be helpful in identifying genes or SNPs underlying the QTL and in the application of molecular genetic information in marker-assisted breeding programs. There is complexity in identifying relationships between wool genes. Part of this complexity in the relationships between wool traits is probably related to the pleiotropic phenomenon. In general, some researchers have found markers that have not been confirmed in other published papers. False positives and false negatives in the statistical methods used can be the reason for the differences in the distinguished genes for the desired traits of wool.

Effect of Alkali Metals and Alkaline Earth Metals Hydroxides on the Structure of Wool Fibers

ABSTRACT Wool is sensitive toward the effect of alkaline solutions which are usually used in the dissolution of wool fibers to regenerate keratin. In this investigation, the effect of different alkalis on the chemical composition and the secondary structure of wool was studied. Wool was treated with equivalent amounts of alkali metal hydroxides (lithium, sodium, and potassium hydroxides) as well as alkaline earth metal hydroxides (strontium and barium hydroxides). The effect of these alkalis on wool was monitored using amino acid analysis, elemental analysis, carboxylic content, acid, and base combining capacity, urea-bisulfite and alkali solubility, and FTIR spectroscopy. Further structure elucidation was conducted by thermo-gravimetric analysis, differential scanning calorimetry, and X-ray diffraction pattern. Scanning electron microscopy was used to assign the alteration of the fiber morphology of the alkali-treated wool. The results of this investigation indicate that the effect of the used alkalis on wool is not similar. Cystine, glycine, and the basic amino acids are the most affected species in the treated wool. Some elimination reactions were involved during alkaline treatment of wool; namely decarboxylation, desulphydration, and deamination. The secondary structure of wool treated with Sr(OH)2 and Ba(OH)2 was changed from the α-helical structure into the β-sheet form.

Analysis of lecithin treatment effects on the structural transformation of wool fiber using vibrational spectroscopy

The keratin macromolecule in wool fiber may be found in α-helix or β-sheet conformations besides a disordered portion. The physical and chemical treatments may cause transformations between α-helix and β-sheet conformations. The aim of this study was to investigate the influence of lecithin treatment on the wool fiber using the micro-Raman spectroscopy and Fourier transform infrared spectroscopy. Characteristic bands found in the FTIR spectra of wool fibers including the amide A, amide B and amide I–III, which are assigned to the peptide bonds of wool keratin and arise from the amide bonds that link the amino acids. The lecithin treatment didn’t affect the peak position of amide bands and only slightly influenced their intensity. It means that the lecithin treatment didn’t change the chemical structure of wool fibers. The amide I and III regions, CC skeletal vibration region, and SS bonds vibration regions were analyzed with the Raman microscope. The results indicated the peak area of α-conformation increased gradually by lecithin treatment of the wool fiber, while the peak area of β-conformation decreased. Therefore, it seems that lecithin treatment of the wool fiber resulted in transformation of β-sheet to α-helix.

Effect of wool fibers on thermal and dielectric properties of Alfa fibers reinforced polyester composite

Thermal and dielectric studies were investigated on hybrid composite of Alfa fibers reinforced polyester matrix. Taking into account the presence of wool fibers in the non-woven Alfa fibers reinforcement, these studies revealed the effect of wool fibers on the thermal stability of the reinforcement and hence on the hydrophilic character of the composite. Indeed, Thermo Gravimetric Analysis (TGA) revealed an enhancement of the moisture regain of the reinforcement, attributed either to the cystine structure of wool fibers or to its hygroscopic character. Contact angle method has shown a medium hydrophilic character of the composite. Differential Scanning Calorimetery (DSC) showed a plasticizer effect of the reinforcement explained by chemical bonds based on secondary bonding between the fibers and the matrix. Dielectric measurements confirmed such thermal analyses by exhibiting the presence of the dielectric relaxations at low temperatures. Furthermore, the analysis of dielectric relaxations at high temperatures illustrated Debye-type behavior of the interfacial polarization effect attributed to a homogenous distribution of the reinforcement in the polyester (PE) matrix.

Bleaching of black pigmented karakul wool fibers using copper sulfate as catalyst

The best chance for an efficient bleaching of highly pigmented wool with minimum fiber damage is provided by the use of metal catalysts in mordanting step preceding peroxide bleaching. This study evaluates the catalytic effect of copper sulfate (CuSO4) in the bleaching process of pigmented wool fibers under the used condition. The effects of CuSO4 and Na4P2O7 (as a stabilizer) concentration, bleaching time and rinsing time after mordanting on yellowness index, optical and mechanical properties were investigated and the optimum conditions for each step was reported. The results showed that an excellent depigmentation with minimum fiber damage is provided by using 1 %w/v CuSO4 and subsequent rinsing for 60 min, as well as bleaching with 60 ml/l H2O2 and 7 %w/v Na4P2O7 for 15 min. The optical properties of fibers were improved after bleaching under optimum conditions compared with raw samples. The color indices revealed that the black wool fibers have turned into a pale light brown shade. The morphology and structure of wool fibers, before and after bleaching, were characterized by using optical microscopy, scanning electron microscopy (SEM), and EDAX test method.

Analysis of structural transformation in wool fiber resulting from oxygen plasma treatment using vibrational spectroscopy

The aim of this study was to investigate the influence of oxygen plasma procedure at different time treatments on wool fiber using the micro-Raman spectroscopy as a non-destructive vibrational spectroscopic technique and Fourier transform infrared spectroscopy. The amide I and III regions, CC skeletal vibration region, and SS and CS bonds vibration regions were analyzed with the Raman microscope. The Fourier transform infrared spectroscope analysis was employed to find out the effect of oxygen plasma treatment on the cysteic acid residues content of the wool fiber sample. The results indicated that the α-helix structure was the highest component content of wool fiber. Moreover, the protein secondary structure of wool fibers was transformed from α-helical arrangement to the β-pleated sheet configuration during the oxygen plasma treatment. Also, the disulphide bonds content in the treated wool fiber reduced because they were fractured and oxidized during oxygen plasma treatment. The oxygen plasma treated samples presented higher cysteic acid compared to the untreated wool samples due to produce more cleavage of disulfide linkages.

Preparation and properties of nano-SiO2-coated wool fibers

Nano-SiO2-coated wool fibers were prepared by coating nano SiO2 onto wool fibers pretreated by low-temperature plasma (LTP) irradiation. The morphologies and structures of coated wool fibers were characterized by scanning electron microscopy, transmission electron microscopy, and fourier transformation infrared spectrometry. The results show that after LTP irradiation, the surface structure of wool fibers was changed and new chemical bonds were formed; nano-SiO2 combined well with the wool fibers and formed a functional layer on the surface of wool fibers. Compared with parent wool, the coated wool fibers had better thermal stability, breaking strength, elongation, and frictional property.

Optimization of enzymatic hydrolysis of wool fibers for nanoparticles production using response surface methodology

Optimization of enzymatic hydrolysis of wool fiber was carried out using a Central Composite Design (CCD) in order to produce wool nanoparticles. The effects of three important determinants, i.e. enzyme loading, substrate concentration and hydrolysis time on enzymatic efficiency were investigated. Polynomial regression model was fitted to the experimental data to generate predicted response such as particle size. The results were subjected to analysis of variance (ANOVA) to determine significant parameters used for optimization. Wool nanoparticles was produced under the attained optimal condition (enzyme loading: 3.3%, substrate concentration: 5g/l and hydrolysis time: 214h), followed by ultrasonic treatment. SEM micrographs indicated wool fiber degradation in which the outer cuticle layer was removed and the inner cortical cells were isolated. The results of particle size analysis indicated the positive effect of sonication on reducing particles size further. FTIR spectra denoted no evident changes in the composition of the chemical groups in the macromolecular structure of wool fiber. Besides, the enzymatic hydrolysis and ultrasonic treatment led to an increase in crystallinity, solubility in caustic solution and thermal stability of wool nanoparticles, but caused a decrease in moisture regain comparing to the raw wool fiber.

Wool cortical cell-based porous films

The aim of this work is to improve the select mechanical properties of keratin films for biomedical application by exploiting the hierarchical cell structure of wool fibers in a simple and green process. Bio-composite keratin films were prepared by ultrasonic irradiation of wool fibers soaked in clean water, have previously been swollen in mild alkali. The disruption of the fiber cell structure produced a suspension of cortical cells that was centrifuged and rinsed to remove part of the hydrolyzed keratin matrix, then cast into micro-structured porous films made of randomly oriented cortical cells stuck to each other by solidification of the matrix. The chemical and physical properties of the porous films were compared with those of compact films produced using the entire hydrolyzed keratin matrix. Reduction of the keratin matrix amount leads to an even micro-porous structure and improves the mechanical properties (ultimate tensile strength: 11.36 MPa; elongation at break: 3.18%), the moisture uptake and the thermal stability of the films. These properties, associated with other properties of wool keratin, which is naturally hydrophilic, non-burning, biodegradable and biocompatible, make the porous bio-composite keratin films simple and low-cost candidates for biomedical and biotechnology applications.

Influence of different pretreatments on the accessibility of transglutaminase and tyrosinase to wool fibre proteins

Wool fibres are subject to a variety of industrial chemical treatments prior to finishing processes. The influence of such treatments on subsequent enzymatic treatments is still poorly characterised, but its importance is paramount to achieve maximal efficiency of enzymatic action on the fibres. The effect of such treatments on wool fibre structure and their significance on the accessibility of the enzymes transglutaminase and tyrosinase to their target amino acids within wool proteins was investigated. These enzymes are of great interest due to their potential as protein cross‐linkers and their capability to covalently graft beneficial compounds onto proteins. The accessibility of target amino acids was assessed using specific peptides tagged with fluorescent probes, followed by epifluorescence or confocal microscopy. Differences in the action of the different chemical pretreatments were found, with a treatment with permonosulphuric acid resulting in the greatest level accessibility to both enzymes, followed by chlorination and plasma treatments. This was confirmed by the increase in tensile strength of treated wool observed in the enzyme‐treated yarns. This work illustrates that the accessibility of these enzymes to their target aminoacids in solid substrates such as wool is key for their action and to achieve the desired property modifications. The techniques used have the advantage of permitting the visual monitoring of the diffusion of the active enzymes through the wool fibre structure and to relate this to the extent of enzymatic reaction. Crucially, this will allow an informed choice of the best wool processing stage at which to introduce such enzyme treatments.

Identification of the ovine KAP11-1 gene (KRTAP11-1) and genetic variation in its coding sequence

Keratin-associated proteins (KAPs) are a structural component of the wool fibre and form the matrix between the keratin intermediate filaments (KIFs). The gene encoding high sulphur-protein KAP11-1 has been identified in human, cattle and mouse, but not yet in sheep, despite the economic importance of wool. In this study, PCR using primers based on the cattle KAP11-1 gene sequence produced an amplicon of the expected size with sheep DNA. Upon using PCR-Single Stranded Conformational Polymorphism (PCR-SSCP) analysis in 260 sheep, six different PCR-SSCP patterns were detected. Either one or a combination of two banding patterns was observed for each sheep, suggesting they were either homozygous or heterozygous for this gene. Sequencing of the amplicons confirmed the occurrence of six DNA sequences. All of these were unique, and the greatest homology was with KRTAP11-1 sequences from cattle, human and mouse, suggesting that they were derived from the ovine KAP11-1 gene and were allelic variants. The ovine KAP11-1 gene had an open reading frame of 477 nucleotides encoding 159 amino acids. The putative protein was rich in serine, cysteine, and threonine which account for 18.2-18.9, 12.6 and 12.0 mol%, respectively. Of these, approximately 20 of the serine and threonine residues might be phosphorylated. Five nucleotide substitutions were identified, and one was non-synonymous and would result in an amino acid change at a potential phosphorylation site. The genetic variation found in KRTAP11-1 may influence its expression, protein structure, and/or post-translational modifications, and consequently affect wool fibre structure and wool traits.

Identification of the keratin-associated protein 13-3 (KAP13-3) gene in sheep

Keratin-associated proteins (KAPs) are a major stru- ctural component of hair and wool fibres, and play a critical role in determining the properties of the fibre. To date, forty functional high sulphur KAP genes from fourteen families have been identified in hu- mans, but only seven functional high sulphur KAP genes have been identified in sheep. This led us to search for the ovine KAP13-3 gene, a gene encoding a high sulphur KAP. In this study, the notional KAP13- 3 gene (KRTAP13-3) was amplified using primers designed based on a reported bovine KRTAP13-3 se- quence. PCR-single stranded conformational poly- morphism (PCR-SSCP) analysis was used to screen amplicons derived from the gene in one hundred and forty seven New Zealand Romney cross-bred sheep. Five unique banding patterns were revealed. Either one PCR-SSCP pattern (homozygous) or a combina- tion of two patterns (heterozygous) was observed for each sheep. Sequencing of PCR amplicons represent- tative of different SSCP patterns revealed five dif- ferent DNA sequences. The sequences derived from the amplicons showed a low homology to other known ovine KRTAPs, but had a high homology with previous reported KRTAP13-n sequences from hu- man and cattle, with the closest homology being with bovine KRTAP13-3, suggesting the sequences repre- sent the ovine KRTAP13-3 locus. Among the five allele sequences, four nucleotide substitutions were identi- fied within the coding region. Of these substitutions, three were non-synonymous and would result in amino acid changes (p.Arg79Cys, p.Arg81Gln and p.Tyr130His). This variation in the KAP13-3 gene may affect gene expression, the structure and assem- bly of the protein, and consequently influence wool traits, if KAP13-3 is of importance to wool fibre structure.

The structure of wool fibers grafted with chitosan coated Ag-loading nano-SiO2 antibacterial composites

Wool fiber was grafted with chitosan coated Ag-loading nano-SiO2 (CCTS-SLS) antibacterial composites under ultraviolet irradiation. The morphologies and structures of CCTS-SLS-wool were characterized by using scanning electronic microscopy, transmission electron microscopy, and Fourier transformation infrared spectrometry. The results show that a uniform and smooth antibacterial layer of 200 nm in thickness was formed on the surface of wool fiber by covalent bonding. The mechanical properties of the antibacterial wool fiber were improved. The antibacterial performance was found to be excellent, with antibacterial effect up to 90 % even after repeated washing. CCTS-SLS-wool possessed soft hand-feeling and good color.

Basic Parameter Study for the Separation of Wool Fibre Components by Ultrasonic Irradiation in Formic Acid

The structure of wool fibre is a key point in clarifying its properties and performances. Wool fibre can be separated into cuticle cells, cortical cells and even macrofibrils using formic acid as the medium by ultrasonication. The disintegration process of wool fibre is significantly subjected to many parameters. In order to obtain the maximum ratio of disintegration of wool fibre, the effect of these parameters on the disintegration process is studied. The separated wool fibre components are examined with a scanning electron microscopy and the disintegration rates are calculated from the weight proportion of residual and original wool fibres. The results indicate that wool fibre can be separated into cortical cells and macrofibrils by ultrasonication in formic acid. The broken ratio of wool fibre varies greatly with different conditions of ultrasonic irradiation, such as irradiation time, temperature, output power of a transducer, shape of vessel, position of probe, ratio of wool fibre to formic acid, and state of wool fibre. Additionally, ultrasonic irradiation is an efficient method for the preparation of intact cortical cells with high yield from wool fibre in appropriate conditions.

Effects of Dyeing Conditions on Discoloration Behavior for Oxidative Dyed Wool Fabrics

The effect of air function on discoloration behavior of oxidation dyes in wool fibers at ordinary temperature and humidity in dark room was investigated. The samples dyed under three different dyeing conditions and dyed with the different mixed ratios of precursor and copular were used in experiment. In the color change defined by chromaticity diagram (a* and b*) and color tone diagram (L* and C*), the color tone of samples dyed under dyeing system including alkali and hydrogen peroxide changed more significant than that of samples dyed in the performed oxidation dye solution. The discoloration of samples dyed with the different mixed rations of precursor and copular is scarcely dependent on mixed ratio, except for the couple system of p-diaminotoluene/p-amino-o-cresol. The modifications of physical and chemical structure of wool fibers had no effect on the decreasing rate of K/S value for the samples dyed using three precursor / copular systems.

Effect of Mechanical and Enzymatic Treatments on Some Properties of Coarse Wool

ABSTRACT A new mechanical method for treatment of wool fibers has been predicted to impart certain desired properties to coarse wool. Subsequent treatment of wool with sodium sulfite and the proteolytic enzyme savinase 16L, Type EX has been conducted. The treated wool fibers have better dyeability with acid, reactive, and basic dyes than the untreated ones. The felting resistance of wool has been enhanced to an acceptable degree. Scanning electron microscopy investigation has been used to monitor any change in the morphological structure of wool fibers.