The high hydrophilicity of pineapple leaf fibres (PALF) limits their use in cement- and gypsum-based composites exposed to moisture. This study evaluates, for the first time, the combined effect of palm kernel oil and beeswax on the hygroscopic resistance and mechanical stability of PALF. The fibres were functionalised with three formulations (oil, wax, and a 1:2 oil/wax blend) applied at different mass ratios (CR = 0.5–2). Treatments increased the average bundle diameter by up to +46% (238 μm) and reduced density down to 1.06 g/cm3. Hygroscopically, water absorption decreased from 202.4% (raw fibres) to 76.3% (CR = 2), representing a maximum reduction of 59.4% in saline medium, while moisture regain dropped from 27.9% to 14.6% (−47.7%). The oil/wax blend proved most effective, simultaneously reducing water absorption (−51.2%) and moisture regain (−46.8%) at CR = 1. Mechanically, the fibres retained tensile strength (415.2 vs. 460.8 MPa, +11% at CR = 1) and exhibited enhanced ductility (+62.5%, with elongation at break increasing from 1.6% to 2.6%), without significantly altering Young’s modulus (12.3 to 10 GPa). Water absorption kinetics were accurately described by the Czel and Mohsenin models (R2 > 0.98). These findings clearly demonstrate that bio-based lipid coatings can provide an eco-friendly alternative to conventional chemical treatments. They improve hygroscopic resistance and preserve mechanical integrity of PALF, providing original quantitative data for their integration into durable cement- and gypsum-based composites subjected to humid or cyclic wet-dry conditions.
Omgba et al. (Thu,) studied this question.