A second life for low‐grade wool through formation of all‐keratin composites in cystine reducing calcium chloride–water–ethanol solution

Abstract

BACKGROUND Coarse low grade wool holds a share of more than 40% of the worldwide production of 1.2 million tons per year. Wool hair with a diameter above 32.5 μm and recycled wool waste represent an important source of high quality keratin. An efficient and simple shaping procedure to form all‐keratin composites could open a new approach to utilise wool keratin for production of sustainable and biodegradable all‐keratin composite. RESULTS In this work the dissolution and regeneration of wool keratin was studied using a concentrated solution of calcium chloride–water–ethanol as solvent and thioglycolate as reducing agent to open disulphide bonds. Up to 70% of the wool keratin dissolved in the solvent at pH 7, 60 °C. After dilution with water a share of 80% of the total keratin could be obtained as regenerated composite structure while 20% of the protein remains in solution. Based on the model studies, all‐keratin composites were prepared by impregnation of wool with solvent followed by thermal consolidation in a heated press at 60 °C and 2.2–3.3 bar pressure. CONCLUSIONS The new method for production of all‐keratin composites permits production of a protein‐based bio‐composite, which opens new applications for low value coarse wool and recycled wool waste. By use of cheap chemicals and thermal consolidation in standard equipment scale‐up of the technology is expected to be straightforward and commercially feasible, leading to a bio‐based and biodegradable composite material. © 2019 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Investigation of the decomplexation of polyamide/CaCl2 complex toward a green, nondestructive recovery of polyamide from textile waste

“…It had previously been determined that CEW mixtures do not dissolve wool or measurably reduce its mass without presence of a cysteine reducing agent 23 . That was confirmed in this work as well, and it may be observed in Figure S1 that no differences can be found between untreated wool and the fiber after treatment.…”

Enhanced keratin extraction from wool waste using a deep eutectic solvent

“…The upper and lower limits of the processing parameters were selected in accordance with our preliminary results and the reported values in the literature. [11,23,24] In particular, due to concerns regarding keratin degradation at high temperatures (i.e. > 130 o C [11]), the current study specified the upper limit of the temperature as 110 o C. At the end of each experiment, the resulting mixture was dialyzed using a 500 Da membrane against distilled water for 3 days at room temperature, and the water was replaced every 8 h. The recovery of the keratin product was achieved via freeze-drying of the mixture, after which the mass of the resulting keratin powder was measured, and the keratin yield in percentage (Ky) calculated as follows;…”

Wool keratin as a novel alternative protein: A comprehensive review of extraction, purification, nutrition, safety, and food applications

“…Several mechanisms of composite formation using keratin have been proposed, including the reduction or oxidation of the protein to form sidechains of cystine groups (Fitz‐Binder et al., 2019). For instance, functional keratin bioplastics were developed through the splitting of disulfide (–S–S–) bonds using a mild alkaline oxidation process by hydrogen peroxide (H 2 O 2 ; Fernández‐d'Arlas, 2019).…”