Nanopartículas de lignina kraft: síntese, caracterização e aplicação em têxteis funcionais.

Abstract

Kraft lignin, one of the main by-products of the pulp and paper industry, has attracted increasing interest as a renewable feedstock for the development of sustainable materials, in line with the principles of the circular economy and the Sustainable Development Goals. In this context, this thesis aimed to investigate the production, characterization, and application of kraft lignin nanoparticles (KLNP) as a strategy to valorize this macromolecule in functional materials. KLNP were produced using the solvent exchange method and characterized in terms of chemical composition, structural and thermal properties, and colloidal stability through spectroscopic, thermal, and microscopic techniques. The results demonstrated the formation of nanoparticles with nanometric dimensions, homogeneous size distribution, and good colloidal stability. The environmental safety of the KLNP was assessed through phytotoxicity assays using arugula seeds (Eruca sativa), with no significant adverse effects observed in the evaluated parameters. In a subsequent stage, the nanoparticles were applied to the functionalization of cotton fabrics to impart functional properties. The incorporation of KLNP led to a significant increase in the ultraviolet protection factor (UPF), as well as effective antibacterial activity against Escherichia coli and Staphylococcus aureus. A homogeneous deposition of nanoparticles on the fabric fibers and enhanced material retention after washing cycles were observed in the presence of a fixing agent. Overall, the results highlight the potential of KLNP as a sustainable and versatile alternative for the development of functional materials and advanced technological textiles. Keywords: sustainable materials; ultraviolet protection; antimicrobial activity; circular economy