Modification of Esperase® by covalent bonding to Eudragit® polymers L 100 and S 100 for wool fibre surface treatment

A review of the sustainable methods in imparting shrink resistance to wool fabrics

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.

Recovery and reuse of immobilized α-amylase during desizing of cotton fabric

Purpose

Enzymatic desizing using α-amylase is the conventional and eco-friendly method of removing starch based size. Conventionally, enzymes are drained after completion of process; being catalysts, they retain their activity after reaction and need to be reused. Immobilization allows the recovery of enzymes to use them as realistic biocatalyst. This study aims to recover and reuse of α-amylase for desizing of cotton via immobilization.

Design/methodology/approach

This paper investigates the application of α-amylase immobilized on Chitosan and Eudragit S-100 for cotton fabric desizing. A commercial α-amylase was immobilized on reversibly soluble-insoluble polymers to work out with inherent problems of heterogeneous reaction media. The immobilization process was optimized for maximum conjugate activity, and immobilized amylases were applied for grey cotton fabric desizing.

Findings

The desizing performance of immobilized amylases was evaluated in terms of starch removal and was compared to free enzyme. The immobilized amylases showed adequate desizing efficiency up to four cycles of use and were recovered easily at the end of each cycle. The amylase immobilized on Eudragit is more efficient for a particular concentration than chitosan.

Practical implications

Immobilization associates with insolubility and increased size of enzymes which lead to poor interactions and limited diffusion especially in textiles where enzymes have to act on macromolecular substrates (heterogeneous media). The selection of support materials plays a significant role in this constraint.

Originality/value

The commercial α-amylase was covalently immobilized on smart polymers for cotton fabric desizing. The target was to achieve immobilized amylase with maximum conjugate activity and limited constraints. The reversibly soluble-insoluble polymers support provide easy recovery with efficient desizing results in heterogeneous reaction media.

Chemical Processing of Wool: Sustainability Considerations

Raw wool fibers contain fat, suint, plant material and minerals. It is necessary to remove these from wool by scouring with a combination of detergents, wetting agents and emulsifiers before further processing. Dyeing and finishing of wool fibers is necessary for their application in apparel and also in interior, automotive, smart and technical textiles. Some of the detergents and auxiliaries used in scouring are eco-toxic and some of them are endocrine disruptors. In many countries, wool scouring and dyeing effluents cannot be discharged to watercourses without further treatment by removing color and toxic components. Wool fibers can be given chemical treatments to make them stain-resistant, flame retardant, shrink-resistant, photo-stable and resistant to insect attack. Some of the chemicals under current practice to achieve these functionalities in wool are not eco-friendly and their discharge to water course is limited to the consent limit set by environment agencies. Environmental impact assessment of raw wool production is well studied but to our knowledge no comprehensive study has been carried out around the environmental impact of chemical processing of wool. Like those of other fiber types, the wool textile industries are under intense consumer as well as stakeholder scrutiny. Accreditation schemes now exist to provide reassurance to modern consumers, who want to see that not only are the marketed products safe but also that they are processed sustainably under ethically and environmentally acceptable conditions. Several alternatives to improve the environmental credentials of various chemical processes used for wool will be discussed.

Enzymatic processing of protein-based fibers

Wool and silk are major protein fiber materials used by the textile industry. Fiber protein structure-function relationships are briefly described here, and the major enzymatic processing routes for textiles and other novel applications are deeply reviewed. Fiber biomodification is described here with various classes of enzymes such as protease, transglutaminase, tyrosinase, and laccase. It is expected that the reader will get a perspective on the research done as a basis for new applications in other areas such as cosmetics and pharma.

Industrial production of enzyme-modified wool fibers for machine-washable bed coverings

Enzyme technology is explored on wool fibers to prevent shrinkage and consolidation behavior during washing of woolen bed coverings using normal household machine conditions. Enzyme modification of wool fibers after two different pretreatments has been realized on industrial scale. Enlarged proteolytic enzyme by chemical modification was applied successfully to prevent substantial fiber strength loss. Felt-ball analysis of the fibers as obtained from this industrial process showed substantial improvement in felting resistance. Further processing of these enzyme-modified fibers and finally integration in bed covering quilts have been executed successfully on industrial production lines. The observed fiber losses during processing were in the range of 4.5-6% which is comparable with that of nonmodified fibers. The machine-washability of these produced bed covering quilts was tested in a household washing machine using both wool and normal wash programs applied at different temperatures. It appeared that, contrary to the good washing results in terms of shrinkage and consolidation resistance using the wool program at moderate temperatures, this resistance is marginal when washed with the normal washing program with higher mechanical agitation level or with the wool program at elevated temperature. This result was different from that obtained with woolen fabrics and explained by the less-structured organisation of fibers within a fleece.