Enhancing (Super)hydrophobicity of Natural Fibers: An Overview of Methodologies and Their Sustainability Assessment

Escalating regulatory pressures have accelerated the development of nature-based alternatives to per- and polyfluoroalkyl substances (PFAS) for hydrophobic textile coatings, driven by concerns over persistence and toxicity. Despite substantial progress, research remains fragmented, with diverse methodologies and limited comparative evaluation of environmental and industrial performance. This review systematically examines wet and dry approaches for applying PFAS-free, natural-based low-surface-energy materials and inducing surface roughness, with a focus on sustainability metrics including energy and water use, solvent consumption, time efficiency, scalability, versatility, waste generation, cost, performance, and durability. Each method is additionally evaluated through an integrated sustainability assessment combining environmental impact and industrial feasibility to identify the most practical and eco-friendly strategies. By highlighting critical bottlenecks and mapping opportunities in process design for biobased chemistries, this review provides a strategic roadmap to accelerate the understanding of the current state and to take an initial step toward upscaling and industrial adoption of PFAS-free alternatives and hydrophobic finishes for natural textiles. In addition, a frequency analysis of reported techniques from 2008 to 2024 reveals temporal trends in methodological development and highlights the dominant approaches and emerging technologies driving the transition toward more sustainable hydrophobic textile engineering.