Click chemistry modification of natural keratin fibers for sustained shrink-resist performance

Valorisation of keratinous wastes: A sustainable approach towards a circular economy

The valorisation of keratinous wastes involves biorefining and recovering the bioresource materials from the keratinous wastes to produce value-added keratin-based bioproducts with a broad application, distribution, and marketability potential. Valorisation of keratinous wastes increases the value of the wastes and enables more sustainable waste management towards a circular bioeconomy. The abundance of keratinous wastes as feedstock from agro-industrial processing, wool processing, and grooming industry benefits biorefinery and extraction of keratins, which could be the optimal solution for developing an ecologically and economically sustainable keratin-based economy. The transition from the current traditional linear models that are deleterious to the environment, which end energy and resources recovery through disposal by incineration and landfilling, to a more sustainable and closed-loop recycling and recovery approach that minimises pollution, disposal challenges, loss of valuable bioresources and potential revenues are required. The paper provides an overview of keratinous wastes and the compositional keratin proteins with the descriptions of the various keratin extraction methods in biorefinery and functional material synthesis, including enzymatic and microbial hydrolysis, chemical hydrolysis (acid/alkaline hydrolysis, dissolution in ionic liquids, oxidative and sulphitolysis) and chemical-free hydrolysis (steam explosion and ultrasonic). The study describes various uses and applications of keratinases and keratin-based composites fabricated through various manufacturing processes such as lyophilisation, compression moulding, solvent casting, hydrogel fabrication, sponge formation, electrospinning, and 3D printing for value-added applications.

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.

Wool Fabrics Coated with an Anionic Bunte Salt-Terminated Polyether: Physicomechanical Properties, Stain Resistance, and Dyeability

The Bunte salt-terminated polyether (BSTP)-based treatment has been developed for the chlorine-free shrink-resist treatment of wool fibers and fabrics. However, the effect of BSTP treatment on the physicomechanical and chemical properties of wool fabrics has not been thoroughly investigated. In this work, wool fabrics were treated with a commercially available BSTP at various concentrations by the pad-dry-cure process. The effect of BSTP coatings on the dyeability, shrink resistance, mechanical properties, wettability, hydrophilicity, and yellowness of the treated wool fabrics was systematically evaluated. It was found that the shrinkage of the treated wool fabrics considerably decreased with an increase in the BSTP concentration. On the other hand, the tensile strength, elongation at break, and surface hydrophilicity highly increased with an increase in the BSTP concentration. The tensile strength of the treated fabric was better than the tensile strength shown by the blank-treated fabric even at the lowest investigated concentration of BSTP (60 g/L). The bending rigidity as well as the bending modulus of wool fabric also decreased with an increase in the applied concentration of BSTP. The treatment showed very little effect on the yellowness and whiteness indices of wool fabric. The stain resistance against C.I. Acid Red 40 of the treated wool fabrics increased with an increase in the applied concentrations of BSTP. However, against red wine, the stain resistance decreased at lower concentrations of BSTP but showed a little effect for the higher concentrations. The coating of wool fabrics with the BSTP not only reduced the shrinkage of the fabrics but also increased their hydrophilicity and also the stain resistance against acid dye-based stain but also negatively affected their dyeability and stain resistance against red wine, especially at lower BSTP concentrations.

Pure keratin membrane and fibers from chicken feather

In this research, keratin was extracted from the disposable chicken feather using l-cysteine as reducing agent. Then, it was re-dissolved in the sodium carbonate-sodium bicarbonate buffer, and the pure keratin membrane and fiber were fabricated by doctor-blade casting process and wet spinning method, respectively. Scanning electron microscopy (SEM), fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were used to characterize the chemical and physical properties of resulting powder, membrane and fiber. Compared with the raw chicken feather, the regenerated keratin materials retain its chemical structure and thermal stability, their relative crystallinity is a little different depend on the shaping method, which leads to the difference in moisture regain. The mechanical results show that tensile strength of the keratin membrane researches 3.5MPa, have potential application in biomedical fields. However, the keratin fiber presents low tenacity, i.e. 0.5cN/dtex, this problem should be solved in order to apply the new fiber in textile and material science.