A roll-to-roll chitosan finishing strategy for elastane recovery†

Elastane fibers, renowned for their balanced strength, elasticity, and comfort, are a prevalent component in blended fabrics. However, their strong adhesion within core-spun yarns and resistance to chemical dissolution pose significant challenges for separation and recycling. The lack of a universal single-solvent strategy across blend types limits the scalability of selective dissolution recycling. Here, we propose an alternative approach using a dissolvable chitosan (CS) finishing layer applied to elastane fibers, which can be selectively removed at end-of-life to enable separation from sheath fibers. We implemented a continuous dip-coating process and demonstrated its feasibility at pilot scale using a roll-to-roll setup. By tuning solution viscosity, we achieved uniform, conformal coatings on neat elastane. A 4 wt% CS solution in 0.5 N HCl yielded a 5–10 μm-thick coating that forms strong non-covalent interactions with the elastane core without compromising the elastic modulus or energy dissipation under cyclic strain. The CS layer can be redissolved under mild acidic conditions, preserving the chemical integrity of the recovered elastane. This proof-of-concept highlights CS dip-coating as a promising finishing strategy for scalable elastane recovery from diverse fiber blends via selective dissolution.