Influence of the extraction method on the physico-chemical, thermal, and mechanical properties of pineapple leaf fibers from Benin

Pineapple leaf residues generated from post-harvest activities represent an abundant yet underutilized lignocellulosic resource in Benin, where production exceeded 500000 tons in 2023. This crop generates large quantities of agricultural waste, with significant environmental impact and a reduction in available arable land, highlighting the need for sustainable valorization strategies. This study investigates the influence of extraction method on the physico-chemical, crystallographic, thermal, and mechanical properties of pineapple leaf fibers intended for bio-based composite applications, comparing two extraction processes: manual scraping and water retting. The extraction method strongly affected fiber morphology and microstructure. Scraped fibers were finer (median diameter: 94 µm) but exhibited higher water absorption (245%) and lower crystallinity (30%) than retted fibers (115 µm, 223%, and 40%, respectively). FTIR analysis indicated partial removal of hemicellulose after retting, without altering the lignocellulosic nature of the fibers. Thermogravimetric analysis revealed thermal stability up to 200°C, with a maximum cellulose degradation temperature of 322°C for scraped fibers and 341°C for retted fibers. This gain in crystallinity was accompanied by a marked improvement in mechanical performance: retted fibers exhibited tensile strength between 784 and 1416 MPa, compared to 403 - 882 MPa for scraped fibers. These results demonstrate that the extraction process strongly governs the microstructure and mechanical behavior of pineapple leaf fibers, which show particular promise as a bio-based reinforcement for polymer or cementitious composite materials, supporting the sustainable valorization of agricultural residues within local and industrial construction sectors.