Facile Fabrication of Eco-Friendly Waterproof Breathable Nanofibrous Membranes with Asymmetric Wettability via Electrospray of Waterborne Polyurethane Emulsion

Waterproof and breathable membranes (WBMs) are essential in diverse applications, including textiles, healthcare, electronics, and construction. Traditional WBMs often rely on hazardous solvents and fluorinated compounds, posing considerable risks to human health and the environment. This study presents an eco-friendly, fluorine-free nanofibrous WBM with asymmetric wettability, fabricated using ethanol, a green solvent, and electrospray technology to coat alcohol soluble polyamide/trimethylolpropane tris (2-methyl-1-aziridine propionate) (EPA/TTMA) nanofibers with a waterborne hydrophobic polyurethane (HPU) emulsion. The resulting EPA/TTMA-HPU WBMs feature a robust three-dimensional cross-linked structure that retains its integrity even after exposure to ethanol. These nanofibrous membranes exhibit differential properties, with a waterproof performance of 103.2 kPa and a moisture permeability of 9.28 kg·m^-2·d^–1 on the hydrophobic side, and 96.1 kPa with 6.92 kg·m^-2·d^–1 on the hydrophilic side, outperforming most fluorine-free WBMs. Furthermore, the durability of the EPA/TTMA-HPU membranes is significantly enhanced by the incorporation of HPU, enabling them to withstand 40 abrasion cycles, 24 h of ultrasonic washing, and ultraviolet irradiation. This study presents a scalable, environmentally benign method for fabricating high-performance WBMs, advancing sustainable membrane technology for protective textiles and other applications.