Fluorination to Convert the Surface of Lignocellulosic Materials from Hydrophilic to Hydrophobic

Natural fibers are increasingly used as sustainable, lightweight, and low-cost alternatives to glass fibers in polymer composites. However, their inherent hydrophilicity and surface polarity limit compatibility with non-polar polymer matrices. Both gas/solid and plasma fluorination modify only the surface of lignocellulosic materials. Mild conditions are mild, with reactivity governed by fluorine concentration, temperature, and material composition. Surface energy is typically assessed through contact-angle measurements and surface analytical techniques that quantify changes in hydrophobicity and chemical functionalities. In wood, fluorination proceeds preferentially in lignin-rich regions, making lignin a key component controlling reactivity and the spatial distribution of fluorinated groups. Natural fibers follow the same logic as for flax, which is a representative example of lignin content. Applications of fluorinated bio-based materials include improved moisture resistance, enhanced compatibility in composites, and functional surfaces with tailored wetting properties. Scalability depends on safety, cost, and process control, especially for direct fluorination. Durability of the treatment varies with depth of modification, and environmental considerations include the potential release of fluorinated species during use or disposal.