Enhancing Epoxy Composites with Alkali-Treated Sedge Fibers: A Mechanical, Thermal, and Chemical Perspective

The advance of industrialization has intensified the growing interest in sustainable materials that reduce environmental impacts without compromising technical performance. In this context, polymer composites reinforced with natural lignocellulosic fibers (NLFs) stand out owing to their renewable origin, biodegradability, low cost, and competitive mechanical properties. This study investigates epoxy resin composites reinforced with sedge fibers ( Cyperus malaccensis ), an abundant yet underexplored resource, evaluating the effects of alkaline NaOH treatment (3% for 24 h) on chemical, thermal, and mechanical properties. Treated and untreated fibers were incorporated into the epoxy matrix at volume fractions of up to 30%. Tensile and flexural mechanical tests were performed, along with thermal analyses by TGA/DTG and DSC, FTIR spectroscopy, and scanning electron microscopy. The results indicated that alkaline treatment significantly improved fiber–matrix adhesion, mainly reflected in increased flexural strength, thereby outperforming neat epoxy resin. In tensile testing, improvements were observed relative to composites with untreated fibers, although the performance did not exceed that of neat epoxy. Thermal analyses evidenced diminished moisture uptake and a slight decrease in thermal stability, attributed to the partial extraction of hemicellulose and lignin. FTIR confirmed surface chemical modifications without cellulose degradation, highlighting the potential of treated sedge fiber as a sustainable reinforcement in polymer composites.