Extraction and Evaluation of Raw and Alkali Treated Pennisetum purpureum Schumach . Cellulosic Fibers for Sustainable Polymer Composites

ABSTRACT Depleting global energy resources and the escalation of environmental problems have driven the development of novel cellulosic fibers for sustainable polymer composites. This study investigates the extraction and performance enhancement of the natural cellulosic fibers obtained from the stems of Pennisetum purpureum Schumach . and explores the potential application as reinforcement fibers in the sustainable polymer composites. The extracted Pennisetum purpureum Schumach . fiber (PPF) was subjected to alkali treatments of varying concentrations, namely, 1, 5, 9, and 13 wt%. The effects of alkali concentration on the comprehensive properties of raw and treated PPFs was systematically investigated. Results demonstrate that the cellulose content of the treated PPFs raised, whereas hemicellulose content decreased after the alkali treatment. Scanning electron microscopy analysis reveals that the treated PPFs exhibit a textured surface, with partial exposure of fiber bundles. Water contact angle and water absorption rate decreased by 6.7%–45.5% and 9.56%–15.75%, respectively, after alkali treatments. Fourier‐transform infrared spectroscopy confirms that hemicellulose and lignin components were effectively dissolved from the surface of the plant fiber. X‐ray diffraction result indicates that the sodium hydroxide treatment significantly raised the crystallization properties of the PPFs, with the crystallinity index rising from 44.43% to 52.27% and the crystalline size improving from 2.00 to 1.88 nm. Thermal stability analysis reveals that the maximum thermal stability temperatures of the PPFs raised from 260°C to 280°C, and the mechanical properties of the treated PPFs enhanced from 62.43 to 117.92 MPa and 6.27 to 9.60 GPa, respectively, after the alkaline modification. These findings confirm that the PPFs treated with an appropriate concentration of sodium hydroxide is the most suitable reinforcement fibers for the structure of sustainable polymer composites.