Phytic acid-chitosan/silicone polyurethane composite coating: A versatile strategy for flame-retardant, water-repellent, and antibacterial hemp cellulose fabrics

In this study, an assembly technique based on phytic acid-modified chitosan (PA-CS) and silicone-containing waterborne polyurethane (SiWPU) was developed to construct of a multifunctional hemp fabric integrating flame retardancy, hydrophobicity, and antibacterial properties. A stable multilayer structure was constructed via hydrogen bonding interactions between the phosphate groups of PA-CS and the urethane groups (-NHCOO-) of SiWPU. Research shows that PA-CS significantly enhances the fabric's thermal stability and decomposes at high temperatures to form a dense carbon layer, raising the limiting oxygen index (LOI) of the hemp fabric to 35.1%, achieving a UL-94 V-0 rating. Compared with the original fabric, the PHRR, HRC, and THR of the PA-CS/SiWPU coated hemp fabric were reduced by 80.7%, 80.7%, and 65.8%, respectively. Simultaneously, the silicon component in SiWPU migrates to the fabric surface, resulting in a water contact angle of 133.10°, demonstrating excellent hydrophobicity and antifouling performance. Furthermore, the coating exhibits remarkable antibacterial activity against S. aureus and E. coli . Following the coating treatment, the breaking strength of the fabric increased by 41.6% (warp) and 40.7% (weft), while the elongation at break improved by 28.6% (warp) and 27.9% (weft). Concurrently, the bending rigidity decreased from 4.93 cN/mm to 3.20 cN/mm, accompanied by a reduction in both static and dynamic friction factors. After 10 washing cycles, the fabric exhibited breaking strength retention rates of 94.2% (warp) and 89.1% (weft). This study opens a new avenue for the high-value-added and multifunctional utilization of hemp fabrics, demonstrating great application potential in fields including home, biomedical, and smart textiles.