Synthesis of multifunctional surface-treatment coatings for hemp fabric: Incorporating flame retardancy, hydrophobicity, antibacterial activity, UV resistance, and enhanced mechanical strength

In this study, a multifunctional waterborne polyurethane (WPU) coating was prepared via a one-pot method to impart flame retardancy, hydrophobicity, antibacterial activity, UV resistance, and enhanced mechanical strength. The WPU system was functionalized with bis-hydroxypropyl fluorosiloxane (HPFSi), hydroxyl-terminated oligophosphate (Exolit OP550), and curcumin, successfully yielding a stable, multi-component curcumin/Exolit OP550/fluorosilicone-modified WPU (CPFSiWPU) emulsion. This emulsion was subsequently applied to hemp fabrics, which then underwent systematic characterization and performance evaluation. The CPFSiWPU coated hemp fabric exhibited outstanding flame-retardant performance, with a limiting oxygen index (LOI) of 36% and an 86.5% reduction in the peak heat release rate (PHRR). The material also demonstrated significant antibacterial efficacy against S. aureus and E. coli , attributable to the incorporation of curcumin. Furthermore, it achieved a high ultraviolet protection factor (UPF) of 51.2 and pronounced hydrophobicity, with a water contact angle of 147.03°. Notably, substantial enhancements in mechanical properties were observed, including increases in breaking strength (277 N in the warp direction and 272 N in the weft) and breaking elongation (25.4% in the warp and 26.9% in the weft). Importantly, the coated fabric's bending rigidity was significantly reduced by 21.8%, while the static and dynamic friction coefficients decreased by 56.4% and 50.5%, respectively, indicating a substantial improvement in softness and hand feel. This work presents a highly promising strategy for multifunctional textile finishing, thereby significantly enhancing the functional value and practical applicability of hemp fabrics.