Thermal effects of ionic liquid dissolution on the structures and properties of regenerated wool keratin

Keratins derived from wool and feathers are a source of raw materials for biomaterial use. Such biomaterials are essentially biodegradable polyamides, and offer many favourable features such as biocompatibility in contrast with petro-derived synthetic materials. In the present study, raw wool samples were dissolved in hot ionic liquid (1-butyl-3-methylimidazolium chloride) at temperatures ranging from 120 to 180 °C, resulting in regenerated keratins after coagulation with water. The physicochemical characteristics of the regenerated keratins were evaluated with respect to their protein profile, thermal stability, mechanical performance and SEM morphology, and contrasted with those of raw wool. Cysteine content reduced significantly on increasing temperature of ionic liquid and some disordering of protein secondary structures occurred in regenerated keratins. Keratin regenerated from a solution prepared with ionic liquid at 180 °C showed improved thermal processing properties, and it revealed dense fibrous network morphology of the film's cross-sectional surface produced under compression moulding. This in-depth study on regenerated keratins demonstrates a potential new route for the conversion of keratinous materials into bio-resin for industrial applications. However, further development is required to create keratinous materials that are melt-processable like classical synthetic polymers.