Comparison of PFAS-free hydrophobic layer-by-layer coatings for cellulosic textiles: evaluation of water repellency, mechanical durability, and the effects of fabric construction

Environmentally safe water-repellent coatings are urgently needed for the textile industry as an alternative to PFAS-based finishes. Challenges include development of coatings that are effective in imparting both water repellency and mechanical durability, with relatively simple synthesis to promote industry use. This study compared the performance and abrasion resistance of two different bio-based, layer-by-layer (LbL) self-assembled hydrophobic coatings for cellulosic fibers. Textile samples were coated with bilayers composed of negatively charged plant-derived carnauba wax and a positively charged component: either poly-L-lysine or lower-cost zinc oxide nanoparticles. To investigate the influence of surface microroughness on coating adhesion and performance, two different woven cotton fabrics were produced in-house. Water contact angle (WCA) testing demonstrated high values approaching superhydrophobicity and excellent coating retention, with minimal decrease in contact angle over contact duration for both coating types. Additionally, fabric construction resulted in differences in surface micro-roughness, and had a statistically significant impact on WCA. Notably, this study is the first to evaluate the mechanical durability of carnauba wax-based LbL coatings using textile industry standard Martindale abrasion method. Both coating types demonstrated minimal performance loss after abrasion with a remarkably small decrease in the initial WCA. The zinc oxide/carnauba wax coating performed comparably to the poly-L-lysine/carnauba wax system, highlighting its potential as a cost-effective and scalable alternative. Further testing revealed minimal impacts of this coating on appearance, flexibility, and air permeability. Overall, the wax-based LbL coating showed promise as a sustainable water-repellent finish for cellulosic textiles suitable for abrasion-prone applications. • Two PFAS-free natural wax coatings were tested on different cotton fabrics • Both demonstrated high water repellency and durability even after abrasion • Fabric construction influenced coating water repellency through surface roughness • Zinc-oxide nanoparticle based layer-by-layer coatings need no textile pre-treatment • The proposed low-cost sustainable coating can reduce use of forever chemicals