Sustainable Reactive Dyeing of Regenerated Cellulose Fibers via Keratin Incorporation

Reactive dyeing of regenerated cellulose fibers is typically associated with high salt and alkali consumption, which leads to considerable environmental burden and can induce fiber degradation and fibrillation during alkaline wet processing. In this work, cellulose/keratin hybrid fibers were developed as a model system to investigate the role of an incorporated protein phase in regulating dye uptake, fixation behavior, and fiber structural stability during reactive dyeing. Compared to pure cellulose fibers, the hybrid fibers exhibited enhanced dye exhaustion and color strength over a wide range of dyeing temperatures and alkali concentrations. Structural analyses revealed that the incorporation of keratin partially disrupted cellulose chain orientation and crystallinity while simultaneously modifying the fiber surface chemistry through the introduction of protein-derived functional groups. These changes promoted dye–fiber interactions via a combination of electrostatic interactions, hydrogen bonding, and secondary interactions under alkaline dyeing conditions. Importantly, keratin-derived hydrophobic domains were largely preserved during dyeing, leading to altered interfacial properties and reduced fibrillation compared to pure cellulose fibers. This study demonstrates that the controlled incorporation of keratin provides an effective strategy to enhance reactive dyeing performance while mitigating structural damage in regenerated cellulose fibers, offering new insights into protein-assisted and low-impact dyeing of sustainable textiles.