Roselle plant stem fibers: A sustainable biomaterial for composite reinforcement and antimicrobial applications

• Demonstrated antibacterial efficacy of Roselle fibers with a 14 mm inhibition zone against S. aureus . • Achieved a high crystallinity index of 61.4 %, indicating robust structural integrity of fibers. • Confirmed thermal stability up to 300 °C and suitability for polymer composite applications. • Comprehensive analysis using XRD, FTIR, SEM, EDX, TGA, and tensile testing for fiber characterization. This study provides a comprehensive analysis of the characteristics of novel Roselle fibers extracted from the stem of the Hibiscus sabdariffa plant using the water retting technique. A range of analytical techniques and antibacterial activity assays were employed to investigate the intrinsic properties of Roselle fibers. Antibacterial inhibition zone tests confirmed the fiber's inherent antibacterial properties. X-ray Diffraction analysis revealed a crystallinity index of 61.4 %, indicating a strong and well-ordered fiber structure. Fourier Transform Infrared spectroscopy identified the primary functional groups, confirming the presence of cellulose, hemicellulose, and lignin. Tensile testing demonstrated notable mechanical performance, with significant tensile strength and moderate elongation, highlighting the fiber's robustness. Scanning Electron Microscopy provided detailed insights into the fiber's surface morphology and microstructure, essential for understanding its compatibility with polymer matrices. Energy Dispersive X-ray analysis revealed a composition dominated by carbon and oxygen, with minor traces of other elements, emphasizing the fiber's organic nature. Thermogravimetric Analysis confirmed its thermal stability. These findings position Roselle fibers as a potential sustainable and environmentally friendly alternative to synthetic fibers, with potential applications in advanced composite materials.