The role of fiber alkalization in enhancing the physical and mechanical performance of false banana fiber and its composites in geopolymer matrices

Natural fibers are increasingly being employed as sustainable reinforcements in composite products. However, industrial applications are limited due to challenges related to moisture absorption, weak fiber-matrix bonding, and inconsistent processing outcomes. Alkaline pretreatment is commonly used to improve fiber surface properties, but little emphasis has been given to how the treatment apparatus affects the resulting fiber surface changes and composite performance. In this study, false banana fibers were alkaline-treated using two different methods: a traditional magnetic stirring setup and an Atlas Syrris automated synthesis reactor. To isolate the influence of the treatment apparatus, all treatment parameters for both instruments were kept constant, including temperature, NaOH concentration, treatment time, fiber volume content, fiber length, and fiber-to-liquor weight ratio. The study focused on how the treatment affected the fibers' physical properties, such as weight, diameter, surface roughness, and morphological changes. Surface roughness was evaluated using ImageJ analysis with the SurfCharJ Plugin. Additionally, the tensile strength and reinforcing efficacy of treated fibers in geopolymer composites were assessed. Results indicate that the reactor-assisted treatment greatly improves fiber modification, reducing diameter and weight by 24.4% and 26.54%, respectively, indicating more effective removal of amorphous and soluble components. Scanning electron microscopy and surface roughness study revealed the improved fiber surface texture, which is beneficial for interfacial bonding. Furthermore, the tensile strength of fibers treated in the Atlas Syrris reactor increased by 22% and when used in geopolymer matrix composites, they demonstrated superior mechanical performance, boosting compressive strength by 56% and splitting tensile strength by 68% when compared to unreinforced geopolymer paste specimens. These improvements outperformed those obtained with fibers treated using magnetic stirring, revealing the superior efficiency and industrial relevance of reactor-assisted alkaline treatment in the production of high-performance natural fiber-reinforced composites.