Boric Acid as a Flame Retardant for Banana Fiber/Polyester Composites

ABSTRACT This study developed fire‐retardant composites using pseudo stem banana fiber‐reinforced unsaturated polyester with boric acid, offering a novel approach to enhancing flame retardancy. Banana fibers, mechanically extracted and alkali‐treated (5%), were processed into twisted yarn (woven structures) and chopped fibers. Composites were fabricated via hand lay‐up using orthophthalic resin and varying boric acid concentrations. Tensile strength, limited oxygen index (LOI), and thermogravimetric behavior were assessed. Woven composites with 15% boric acid exhibited 24.18 MPa tensile strength, below untreated counterparts (28.74 MPa). Increasing boric acid to 20% in chopped fiber composites elevated LOI from 18.7% to 28.5% (untreated: 18%), attributed to enhanced char formation. Thermogravimetric analysis (TGA) showed 20% boric acid‐treated composites (chopped and woven) resisted thermal decomposition. However, woven structures demonstrated uneven resin distribution, reducing fire‐retardant penetration and accelerating decomposition compared to chopped fibers. While boric acid lowered mechanical properties, composites retained sufficient thermal stability for light construction, furniture, and decorative panels, serving as eco‐friendly alternatives to synthetic materials. The study underscores a viable balance between fire retardancy and structural performance, positioning banana fiber‐boric acid composites as sustainable solutions for nonload‐bearing applications.