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The laccase-assisted grafting of poly(tyrosine) is performed aiming to impart shrink-resistant properties to the wool materials. Laccase is able to catalyze the oxidation of tyrosine into dityrosine efficiently. When the reaction is performed using poly(ethylene glycol) (PEG) as the template, the tyrosine oxidation gives rise to differentiated oxidation products, including di-, tri-, and tetra-tyrosine, promoting a higher grafting onto the wool fibers. The characterization of the grafted wool fibers and fabrics reveals some loss of crystallinity (about 4% of crystallization index) and thermal resistance (decreasing from 232°C to 224°C) resulting from the grafting process. However, the new bonds established between the new oxidation products and the amino groups of the wool promote an improvement, not only of the shrinkage properties (1.87% of area shrinkage) but also of their mechanical behavior (increasing by 45.28%). The strategy herein presented demonstrates the potentiality to be applied as a “green” process for wool anti-shrinkage without compromising the fibers’ performance.

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• Wool fibers are shrink-resist treated to make the wool garments machine washable. • The scales available on wool fiber surface are responsible for felting shrinkage. • Various treatments have been investigated to make wool garments shrink-resistant. • The chlorine-Hercosett process is the most effective but harmful to the environment. • The future trend of green and sustainable alternatives treatments are discussed. Wool fiber is a natural protein fiber, which is used for the manufacturing of apparels, and floorcoverings because of its excellent fire retardancy, stain-resistance, antistatic and odor control properties along with exceptional warmth and resilience. However, wool fiber has several serious demerits, such as garments made of wool fibers extensively shrink during their laundering. To overcome this problem, wool fibers, especially those are used in apparel, are frequently shrink-resist treated to make them machine-washable. A wide range of treatments including oxidative, enzymatic, radiation, polymeric coatings, sol-gel coatings, and plasma treatments have been investigated to make wool fiber shrink-resistant. In this review, the mechanisms of wool fiber shrinkage, the research carried out until recently to make wool fiber shrink-resistant, and the current status of the sustainable alternatives developed, have been compiled and presented. The various methods investigated have been critically discussed with their merits and demerits, shrink-resist performance, and their shrink-resistance mechanisms. The chemistry and synthesis of various polymers used for the shrink-resistance and their reactions with wool fiber have been outlined. This review also includes the current challenges to make shrink-resist treatments green and sustainable, and also the future directions to meet these challenges. Some of the treatments investigated may affect the biodegradability of wool fibers, especially those are based on coating with synthetic polymers. A sustainable alternative polymeric coating based on sustainably produced polymeric resins, especially bio-based resins, needs to be developed so that the future treatments become sustainable. [ABSTRACT FROM AUTHOR]

Knitted wool fabric was pre-treated with the serine type protease, Esperase 8.0L (EC3.4.21.62), and sodium sulphite followed by an immersion treatment with a sol-gel hybrid polymer. To enhance the durability of the sol-gel treatment on wool, one of two different alkoxysilanes containing coupling epoxy or mercapto groups were added to the sol-gel hybrid. The combination of protease treatment with an immersion sol-gel treatment achieved wool fabric that was lightweight with a soft handle and had combined shrink-resistance and hydrophobic properties without fibre discoloration. The addition of an alkoxysilane with a mercapto coupling group within the sol-gel hybrid gave better performance than using an alkoxysilane with an epoxy coupling group in terms of polymer uptake, fabric shrink resistance, whiteness and durability to washing. [ABSTRACT FROM AUTHOR]

Abstract: Polypeptides were extracted from wool protein fibres using the serine type protease Esperase 8.0L (EC 3.4.21.62), a subtilisin from Bacillus sp., in a reducing solution. The extracted polypeptides, in aqueous liquor, were then applied to modify the fibre surface of wool fabric with or without additional protease. The treated wool fabric was subsequently treated with the cross-linking agent, glycerol diglycidyl ether, and then underwent a curing process to affix the polypeptide to the fibre. The resulting knitted fabric showed a very high level of shrink-resistance to machine washing, without excessive fibre damage. Shrinkage of 1–2% could be achieved after 5 times 5A washes with minimal (<1%) weight loss due to washing and a burst strength of 317kPa. [Copyright &y& Elsevier]

Abstract: A range of enteric polymeric molecules of different molecular masses and chemical structures were coupled to the protease Esperase (EC 3.4.21.62) using carbodiimide. The activities of the range of chemically modified enzymes of enlarged molecular weight were measured with a standard assay on casein as substrate. Gel filtration confirmed covalent bonding had taken place. Using the same activity value per gram of fibre, the range of modified enzymes were used to treat wool to see if the size of the enlarged enzyme would effect the location of enzyme attack and penetration ability. Less fibre damage in terms of weight loss and tensile strength of treated wool was observed for all six modified enzymes and was less than native enzyme of a similar activity level. All modified enzymes showed similar levels of improved shrink-resistance. [Copyright &y& Elsevier]

Knitted wool and wool/nylon blend dyed fabrics were treated with low temperature plasma (LTP) to achieve optimum shrink-resistance without impairing surface topography, colour or fastness to washing of the fabrics. As LTP tends to impair handle of the fabrics, both wool and wool/nylon blend fabrics were submitted to industrial softening and/or biopolymer treatments after LTP treatment, leading to hydrophilic wool and wool/nylon blend fabrics with improved shrink-resistance without any colour changes and good fastness to washing. The results obtained were compared with those obtained by an industrial shrink-resist treatment. [ABSTRACT FROM AUTHOR]

Abstract: There is currently considerable interest in the use of enzymes to achieve a variety of finishing effects on wool, but it is apparent that the extent of fibre degradation by enzymes is of major concern during their commercial application. Proteolytic enzymes are known to penetrate and degrade the internal wool structure during processing, causing fibre damage, rather than limiting the degradation to the cuticle cells. The ability to be able to control the exact location of proteolytic attack on wool protein structures will lead to the successful development of enzymatic treatments for achieving a variety of finishing effects for wool-containing products. This present work describes the modification of proteases so that enzymatic modification of wool fibres is restricted to the cuticle scales of the fibres. Bulk trials have demonstrated that novel modifications of the enzyme enable the reaction of the enzyme with wool to be controlled, so that less degradation of the wool occurs than in similar treatments with the native protease. An anti-felting effect has been achieved without any significant weight loss being caused by the modified protease during the treatment. This novel enzymatic process leads to environmentally friendly production of machine washable wool. [Copyright &y& Elsevier]

The simultaneous stabilization of set and shrink proofing of pre-chlorinated wool fabric can be achieved by the condensation of a di-isocyanate with a polyamine or a polyalcohol across the wool-liquid-phase boundary. When polymerization occurred at the interface between two immiscible solvents, a high degree of shrinkage-resistance, but no set-stabilization, was obtained. Polymers derived from the reaction of a polyamine with diacid chlorides or bis(chloroformates) failed to stabilize the set and produced satisfactory shrink-resistance only when formed by condensation at a liquid-liquid interface. Polymers derived from the reaction of a polyamine with divinyl sulphone, epichlorohydrin, or formaldehyde failed to shrink proof the wool and lowered the set stability produced by the action of divinyl sulphone, epichlorohydrin, or formaldehyde alone. The mechanism of set-stabilization by polymers is discussed in terms of fibre-encapsulation and inter-fibre bonding. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented regarding the extent of covalent bonding between wool and a polyurethane prepolymer containing isocyanate groups.

A method is described whereby the shrinking property of wool can be modified during growth by the administration of chemical additives to the sheep's diet so as to enter the character of the fibre half-way through the growth of the staple. Thus, hard-root-soft-tip fibres can be grown to enhance shrinkage and soft-root- hard-tip fibres to impart shrink-resistance. Methods of modifying the shrinkage of wool have so far been confined to chemical treatments of the shorn fibre, but this original approach to shrinkage control also presents an opportunity for the mass production of a large variety of other types of special-purpose wools. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to a review on the finishing of textile fabrics by C.S. Whewell, in the Volume 2 of the "Journal of the Textile Institute."