Siloxane-Based Sol-Gel Coatings for Fluorine-Free Water-Repellent Textiles

The growing global restriction of long-chain per- and polyfluoroalkyl substances (PFASs), a class of persistent, bioaccumulative chemicals widely used for water and stain repellency, has accelerated the search for safer, fluorine-free alternatives that maintain comparable water-repellent performance with lower environmental impact. In this study, a scalable sol-gel-based fluorine-free waterrepellent coating derived from triethoxy(octyl)silane (OS) and amino-terminated polydimethylsiloxane (APT-PDMS) was reported. The hybrid formulation was applied to cotton fabrics via a conventional pad-dry-cure process. The treated textiles showed high water contact angles (≥130°). Surface morphology and chemistry were evaluated using SEM-EDS, ATR-FTIR, and Raman spectroscopy, confirming uniform coating coverage and covalent bonding with the substrate. The treatment provides a non-toxic, fluorine-free, and industry-friendly solution for water-repellent textile finishing. These results confirm that the proposed one-step, water-based sol-gel method offers a sustainable and scalable approach for producing high-performance water-repellent finishes on natural textiles, offering a promising alternative to PFAS-based chemistries for outdoor apparel and technical textiles.