A case study on mechanical enhancement of pineapple leaf fibers treated with lime and sodium bicarbonate

Natural fibers are gradually replacing glass fibers in fiber-reinforced composites, especially for applications where extremely high strength is not required. In Mauritius, pineapple leaves are an abundant agricultural waste, offering an untapped source for bio-based fiber composites. However, achieving the necessary mechanical properties generally demands chemical pretreatment, commonly with environmentally harmful sodium hydroxide (NaOH). This study aims to develop and evaluate alternative, eco-friendly chemical treatments for pineapple leaf fibers (PALF). Two environmentally friendly treatments – lime and sodium bicarbonate – were investigated and compared to conventional NaOH treatment. Both treatments use natural substances and are tested on two different types of PALF with varying soaking times, while solution concentrations and preparation methods were optimized to minimize resource and energy consumption. To identify the most effective treatment, mechanical properties such as tensile strength, diameter, force at break and linear density were measured and FTIR spectra as well as SEM images were analyzed to evaluate both performance improvements and the underlying mechanisms. The results show that sodium bicarbonate treatment for 24 hours yields the highest tensile strength increase (> 75%) for both studied PALF types, whereas lime or NaOH treatment results in an approximately 50% increase. Both ecofriendly treatments of PALF perform as well as or better than the commonly used treatment, highlighting their potential for future sustainable composite applications. • Eco-friendly pretreatment of pineapple leaf fibers using lime and sodium bicarbonate • Sodium bicarbonate (24 h) achieves >75% tensile strength increase in PALF • Treatments enhance fiber properties without major removal of hemicellulose or lignin • Lime and sodium bicarbonate are viable alternatives to conventional NaOH mercerization • Study supports sustainable valorization of agricultural waste at the fiber level