Waterproof and moisture permeable coating of polyester fabrics using a novel waterborne polyurethane agent modified with silk fibroin and polyvinylpyrrolidone

A novel waterproof and moisture-permeable coating agent was prepared by modifying a waterborne polyurethane (WPU) agent with silk fibroin (SF) and polyvinylpyrrolidone (PVP), and the PVP/SF/WPU blended agent was applied in polyester fabric coating to achieve a desirable waterproof and breathable effect. The PVP/SF/WPU film prepared by the novel coating agent was characterized with Fourier transform infrared (FT-IR), scanning electron microscope (SEM), thermogravimetry (TG) and X-ray diffraction (XRD) techniques, and the moisture permeability and water repellency of the PVP/SF/WPU coated polyester fabrics were evaluated. The results showed that the thermostability of the blended film was increased compared to the single WPU film, and the compatibility of SF and polyurethane was improved with adding PVP component; the moisture permeability and waterproof of the PVP/SF/WPU coated polyester fabrics were improved significantly. The optimized recipe of the PVP/SF/WPU-coating agent was as follows: 10 wt.%SF (with particle size of 5 μm), 4 wt.% PVP, 4 wt.% cross-linking agent TF694A, and 2 wt.% Thickener TF601. The water vapor transmission rate and hydrostatic pressure value of the PVP/SF/WPU coated polyester fabric reached 5,031 g/ (m² 24 h) and 493 mm H₂O, respectively. The physical and mechanical properties of the coated fabric were not considerably affected.