Bio-based coating for wool fabrics prepared from sodium alginate and Eobania vermiculata snail shell waste for...

This study investigates the development of a novel sustainable bio-based coating to enhance the flame-retardant properties of wool fabrics. The coating consists of a hybrid formulation combining Eobania vermiculata (EV) snail shell microparticles, rich in non-combustible calcium carbonate (CaCO₃) and mineral components, with sodium alginate (SA) used as a bio-based thickener. It was applied using a direct coating technique. Vertical flammability tests demonstrated that combustion of the coated fabrics ceased before removal of the ignition source (12 s). In addition, the char length decreased significantly from 27.53 ± 4.27 cm for the untreated wool fabric (Wool-NT) to 5.4 ± 0.03 cm for Wool-SA-EV. SEM observations revealed smoother fiber surfaces and well-distributed snail shell microparticles (< 90 µm). FTIR analysis confirmed the deposition of the coating via physical interactions with wool fibers. Furthermore, tensile strength of Wool-SA-EV samples increased by approximately 16.6% compared with untreated samples, accompanied by a significant improvement in elastic strain and elongation at maximum force (85.4%). The flexural rigidity increased from 3.12 ± 0.50 to 6.64 ± 0.56 mg cm after SA coating, while the addition of EV microparticles did not significantly affect fabric stiffness. Air permeability decreased from 267 L/m²/s for Wool-NT to 212.33 and 165.33 L/m²/s for Wool-SA and Wool-SA-EV, respectively, due to pore filling and the formation of a more compact fabric structure. These results highlight the potential for valorizing snail shell waste to develop an eco-friendly and bio-based coating for wool fabrics.