A sustainable approach for the functionalization of lyocell nonwovens by hardwood kraft lignin

Eucalyptus kraft lignin (EKL), a side product of pulp-and-paper industry, was proposed as an environmentally sustainable multifunctional agent for the modification of needle-punched nonwovens produced from regenerated lyocell fibres. Functionalization was attained by impregnating the nonwoven in a lignin solution (5-100 g/L) in 1-5% ammonia using the padding process followed by hot pressing of the dried mat at 180 °C for 2 min at 2 bar. This heat treatment carried out above the glass transition temperature of lignin allowed its better dispersion and adhesion to the fibre surface, particularly evident in the hydrophobicity of the nonwoven fabric and its resistance to leaching during washing. Tuneable nonwoven colour (from beige to dark brown), water contact angle (from 120° to 160°), improved tensile strength in machine direction, enhanced UV protection (UPF >50+), programmable thermal management response, and variable antimicrobial resistance against Gram-positive bacteria Staphylococcus aureus can be achieved while varying the amount of the retained lignin in the needle-punched structure. Although EKL imparts enhanced integrity to lyocell nonwovens fabrics during biodegradation, lignin-modified nonwovens still retain biodegradability and demonstrate the absence of concomitant phytotoxic effects. All-round balance of nonwoven fabrics properties was attained with a lignin content in the fabric of approximately 2.5%. This study positions EKL as a reliable bio-based multifunctional additive, enabling the development of sustainable, high-performance lyocell nonwovens aligned with circular economy principles through an environmentally responsible approach thus avoiding the hazardous functional agents originating from fossil resources.