Phytic acid–urea doped hybrid sol–gel coating for flame retardancy of polyester/cotton

It is highly desirable to construct a sustainable hybrid silica coating to enhance the flame-retardant (FR) properties of polyester/cotton (T/C) blend fabrics. In this study, a novel urea phytate salt was synthesized and used to prepare a phosphorus/nitrogen-doped hybrid silica sol system. The hybrid silica coating was then applied to a T/C fabric to develop a highly efficient FR-coated T/C fabric with improved washing durability. The surface morphology, size distribution and condensation degree of the hybrid silica sol particles were characterized. The thermal stability, heat release, flame retardancy and mode of action of the coated T/C fabrics were also investigated. The coated T/C fabrics exhibited self-extinguishing performance, with the damaged length decreasing from 30 to 8.5 cm and the limiting oxygen index increasing from 17.1 to 30%. The desirable flame retardancy of the coated T/C fabric was well maintained even after ten washing cycles. The remarkably inhibited heat release ability suggested a decreased fire hazard. A potential condensed-phase flame retardancy mechanism was proposed based on thermogravimetric and char residue analyses. This study presents an eco-friendly and efficient hybrid silica coating that effectively reduces the fire hazard of T/C fabrics.