Agro-Waste from Gladiolus hybrida Plants: Effects of Alkaline Processing on a New Natural Cellulosic Fiber Derived for Polymer Composites

This study investigates the potentiality of Gladiolus hybrida leaf fibers (GHLFs) as an eco-friendly reinforcing substance for polymer-based composites. Novel natural fibers were harvested from Gladiolus hybrida leaves (GHL) and treated with NaOH alkali (T-GHLF) to assess their influence on physical, strength, molecular, and heat-related properties. Initially, the obtained fibers had a diameter of 0.3084 mm, which reduced to 0.2524 mm following alkali treatment. Chemical investigation indicated that the cellulose content increased to 57.16 wt %, an enhancement of 11.38% over the untreated fibers, which had a cellulose content of 51.32 wt %. The degree of crystallinity percentage of the raw and processed fibers was 57.85% and 60.82%, respectively, without significant change in the cellulose phase. The thermogravimetric analysis indicated that T-GHLF exhibited improved thermal stability up to 257.77 °C, with the kinetic activation energy (Ea) measured at 81.56 kJ/mol. Fourier transform infrared spectroscopy (FTIR) has been employed to observe the distribution of different chemical groups on the fiber surface. Scanning electron microscopy (SEM) revealed that the fibers had a roughened surface. According to tensile testing of a single fiber, the Young’s modulus values for GHLFs and T-GHLFs were 2.08 and 2.21 GPa, respectively. These evidences suggested that GHLFs exhibited characteristics comparable to those of presently used natural fibers, positioning them as a strong contender to replace organic fibers in resin matrix composites. As a result, these novel natural resources may assist in achieving the Sustainable Development Goals of the United Nations through the sustainable utilization of agricultural waste in polymer matrix composites.