Thermal, Mechanical, and Interfacial Evaluation of Banana Fiber Biocomposites with Exploratory Alkali Treatment

Commercial banana‑fiber textiles derived from sustainable fashion supply chains are a largely underexplored reinforcement for polymer composites. Their compatibility with conventional and bio‑based resins and eco‑friendly treatments must be carefully studied to ascertain their utility. This work constitutes the first comprehensive thermomechanical and interfacial evaluation of sodium-bicarbonate-treated commercial banana-fiber composites with both synthetic and bio-epoxy matrices, offering new insights into fiber morphology and composite performance. Sodium bicarbonate treatment (8.5 wt.% for 90 h) induced mild fiber decohesion and a 6.8% reduction in fiber diameter. Within the composite systems, the glass transition temperature increased by 13.7%, and the tan δ peak reduced by 16.1%. Interestingly, the use of a bio-epoxy resin with these treated fibers yielded a 4.3% higher flexural modulus and an 8.7% higher glass transition temperature than those observed with its synthetic counterpart. A 7.9% reduction in tan δ peak occurred, suggesting improved fiber-matrix compatibility with the bio-based resin, which is in agreement with micrographic observations. These findings are timely for sustainable composite development and demonstrate the potential of commercial banana-fiber textiles for composite applications, particularly when combined with greener surface treatment methods and bio-based resin systems.