Characterization of Nettle Fibers ( <i>Urtica dioica L</i> .) for Eco-Textile Applications: Influence of Water Retting Duration

The global textile and composite industries are heavily reliant on petroleum-based synthetic fibers, contributing to greenhouse gas emissions, microplastic pollution, and persistent environmental waste. This situation has interest in renewable, biodegradable natural fiber alternatives that are compatible with circular economy principles. This study examines the impact of water retting duration (10 days: D10; 21 days: D21) on the structural, physicochemical, mechanical, and thermal properties of wild nettle fibers from Giresun (Türkiye). Two controlled retting periods (D10) and (D21) extracted fibers were characterized using FT-IR spectroscopy, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, single-fiber tensile test, and fiber thickness measurement. D21 retting increased effective fiber length by 17% and reduced tensile variability by nearly fourfold compared with D10. XRD confirmed a high cellulose I crystallinity index exceeding 83% −87% for both samples, with a slight increase for D21 fibers. FT-IR confirmed reduced hemicellulose signals and enhanced cellulose bands in D21 fibers. Tensile variability decreased markedly from 67.8% D10 to 17.0% D21. TGA indicated enhanced thermal stability in D21 fibers. These findings underscore the potential of Giresun-sourced nettle as a sustainable bast fiber for eco-friendly textiles and bio-composites, supporting EU Circular Economy and Green Deal goals.