Enhancement of the chemical, physical, mechanical and thermal properties of NaOH-treated natural cellulosic fibers from Calathea lutea

The increasing demand for sustainable composite materials is propelling the exploration of new natural fiber with high mechanical performance. However, low interfacial connection as well as a high content of amorphous components, including lignin and hemicellulose, remain significant challenges in the development of natural reinforcement fiber. Therefore, this study aimed to propose Calathea lutea fiber (CLF) as a new reinforcement candidate in polymer composite. The main objective of the analysis was to evaluate the effect of alkali treatment on the chemical, mechanical, morphological, crystallinity, and thermal properties of CLF. Treatment was conducted by immersing fiber in a 5 % sodium hydroxide (NaOH) solution for several hours. The resulting fiber was characterized using tensile test, Fourrier transform infrared (FTIR), Thermogravimetric analysis (TGA), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and chemical analysis. The results showed that treatment for 2 h (N2H) led to a significant increase in tensile strength (182.34 ± 26.96 MPa), Young's modulus (12.70 ± 1.61 GPa), crystallinity index (49.16 %), and the main thermal degradation temperature. In addition, SEM analysis signified a cleaner and rougher fiber surface. Alkali-treated CLF had the potential to serve as an alternative reinforcement material for the development of environmentally friendly and sustainable natural composite. • Calathea lutea fibers (CLF) demonstrate strong potential as a sustainable natural fiber reinforcement for polymer composites. • Alkali treatment using 5 % NaOH significantly improves the chemical composition by increasing cellulose content and reducing lignin and hemicellulose levels. • Optimal alkali treatment duration of 2 h (N2H) yields the highest tensile strength (182.34 ± 26.96 MPa) and Young’s modulus (12.70 ± 1.61 GPa), along with enhanced fiber crystallinity (49.16 %). • SEM analysis reveals that alkali treatment produces cleaner and rougher fiber surfaces, facilitating better mechanical interlocking with polymer matrices. • Alkali treatment improves thermal stability, with treated fibers showing increased degradation temperatures compared to untreated fibers. • Prolonged alkali treatment beyond 2 h leads to degradation of fiber microstructure and a decline in mechanical properties.