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

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 mu m 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 degrees 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 degrees 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. (c) 2019 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.