Starch-modified date palm leaf fibers for eco-friendly epoxy biocomposites: microstructural, structural, and thermal characterization

Growing environmental concerns are driving the search for sustainable alternatives to synthetic materials. This study investigates the effect of a chemical-free, starch-based treatment on date palm leaf fibers (DPFs) for use in fully biodegradable epoxy biocomposites. The treatment consists of mechanical cleaning, water washing, and immersion in an aqueous starch solution, with no chemical reagents. SEM and AFM analyses confirm effective removal of surface waxes, lignin, and hemicellulose, along with significant fiber bundle fibrillation. Surface amplitude (Rq) decreased by 37%, from 2.59 nm to 2.39 nm. XRD analysis reveals an increase in the Crystallinity Index from 41.93% to 44.72%, with a crystal size of 4.33 nm. FTIR analysis further confirms purification of the cellulosic structure. TGA results show improved thermal stability of starch-treated fibers (STFs) between 250 °C and 350 °C, indicating reduced hemicellulose and cellulose degradation. These findings demonstrate that starch treatment is an effective, eco-friendly surface modification that enhances interfacial adhesion and supports the development of high-performance biodegradable biocomposites.