AbstractBecause of the increasing awareness of the environment and energy issues, as well as advances in technology, the areas of application for annual plant fiber functional materials are expanding. In this work, two chemical treatments, alkalization (2 h agitation with 5% NaOH) and furfurylation (graft furfuryl alcohol followed by oxidation with (1N) NaClO2 solution), were conducted on Luffa cylindrica fiber surfaces. The grafting of furfuryl alcohol followed by oxidation-generated quinines showed better results than alkaline treatment with respect to enhancement of surface area and hydrophobicity as well as wax, lignin, and hemicellulose extraction. The efficiency of chemical treatments was verified by elemental analysis and FTIR spectroscopy. Differential scanning calorimetry, thermo-gravimetric analysis, scanning electron microscopy, water absorption, and mechanical tests were performed to determine the thermal, mechanical, and morphological properties of untreated and chemically treated luffa fiber reinforced epoxy composites. Microstructures of the composites were examined to determine the mechanisms for the fiber-matrix interaction, which affects the thermal stability, water absorption, and mechanical behavior of the composites. The data from the water absorption process of composites at various temperatures were analyzed using a diffusion model based on Fick’s law.