Influence of Alkaline Treatment on Banana Peel Powder Functionality at Ultra-Low Loading in PLA Composites: A Comparative Study

Environmental concerns over petroleum-based plastics have accelerated demand for biodegradable composites from renewable resources. Conventional filler loadings (5%–40%) consistently produce particle agglomeration and ductility loss, leaving a critical gap for composites achieving simultaneous strength, flexibility, and thermal stability. This study investigates ultra-low loading (0.3%, 0.5%, 0.7%, 1.0%) NaOH-treated banana peel powder (BPP) as multifunctional reinforcement in PLA matrices. BPP was derived from agricultural waste, surface-modified with 0.1M NaOH, dried, ground, and sieved to 177μm. Treated and untreated composites at four loading levels were fabricated via melt-blending and compression molding. ATR-FTIR confirmed significant surface reorganization post-treatment, including a 138.4% enrichment in cellulosic content (8.6% to 20.5%), validating improved interfacial compatibility. At 0.3 wt% treated BPP, composites exhibited simultaneous gains in tensile strength (62.15 MPa, +5.83%), flexural strength (95.93 MPa, +9.8%), and elongation at break (1.90%, +34.75%) a rare synergistic improvement in particulate systems. SEM confirmed uniform dispersion and strong matrix adhesion, while TGA and DSC revealed enhanced thermal stability (T g : 63°C, T max : 354.90°C) with marginal crystallinity reduction. This ultra-low loading approach demonstrates effective agricultural waste valorization while delivering superior performance in biodegradable polymer composites.