55. Fibers from Feather Keratin

Feathers are natural protein fibers with a unique hierarchical structure [07Red]. Keratin, the major (>90 %) protein in feathers, is a relatively small protein with molecular weight of 10 kDa and contains high levels of cysteine which provides extensive disulfide cross-linking making feather keratins strong and tough. Keratins have a β-sheet conformation with 96 amino acids having 7 cysteine residues as terminals [09Poo]. However, the central portion of keratin is also reported to have α-structures. Several attempts have been made to develop regenerated protein fibers from feather keratin. Regenerated keratin fibers were obtained using alkali and surfactants [47Har, 49Wor]. In another research, ionic solvents were used to dissolve keratin and obtain fibers. However, the tensile strength of the fibers was only 0.2 g/den, much lower than the strength of the natural protein fibers such as wool. Recently, controlled disentanglement and alignment of keratin molecules were achieved by using a surfactant sodium dodecyl sulfate (SDS). Figure 55.1 shows the digital picture of the actual regenerated keratin fibers. The mechanical properties of the fibers are shown in Table 55.1. As seen from the table, the properties of the fibers were affected by the type of coagulation bath used. Fibers obtained had tensile strength of up to 0.7 g/den and had low dry elongation but good wet elongation of up to 28 %.