Influence of Biological, Chemical, and Combined Extraction Methods on the Physicochemical, Structural, and Mechanical Properties of Okra (Abelmoschus esculentus) Fibers for Natural Latex-Based Bio-Composite Reinforcement

Okra (Abelmoschus esculentus) stems represent an abundant lignocellulosic resource with considerable potential for sustainable textile and bio-composite applications. This study investigated the effects of biological, alkaline (1–7.5 wt.% NaOH), and combined extraction methods on the physicochemical, structural, and mechanical properties of okra fibers. FTIR and XRD analyses confirmed the progressive removal of hemicellulose and lignin, resulting in increased cellulose crystallinity after alkaline treatment. Optical microscopy revealed enhanced fiber individualization and cleaner surface morphology. Increasing the NaOH concentration improved fiber density, reduced hygroscopicity, and enhanced mechanical performance. The highest cellulose content (76.52%), tensile strength (148.57 MPa), and Young’s modulus (6.62 GPa) were achieved with 7.5 wt.% NaOH treatment. However, excessive treatment severity induced partial cellulose degradation. Overall, alkali-treated okra fibers exhibited improved structural organization, reduced moisture sensitivity, and enhanced mechanical properties, highlighting their potential as lightweight and sustainable reinforcements for technical textile and bio-composite applications.