A phytic acid-based chelating coordination embedding structure of phosphorus–boron–nitride synergistic flame retardant to enhance durability and flame retardancy of cotton

A halogen-free, non-formaldehyde and eco-friendly bio-based synergistic flame retardant containing phosphorus–boron–nitrogen elements were synthesized and applied on cotton fabrics. Three curing cycles in cotton finishing process were employed. Samples treated with 30 g/L PBN solutions revealed the best result, while high concentrations did not gain more weight increase nor improved performance on the products. The SEM morphologies suggested penetration of ammonium phytate groups to the inner space and floatation of boron-containing groups on the surfaces of the cotton fibers. FTIR and XPS analyses indicated that after 50 laundering cycles, the boron can still stay on the surface of the treated cotton fibers. The LOI value of 30 g/L PBN finished cotton fabrics reached 45.0% and remained at 37.6% after 50 LCs. The char length of the treated cotton sample was 63 mm, whereas the control sample was 300 mm. The TG analysis in N₂ demonstrated that the decomposition temperature of the treated fabric slightly decreased, while the thermal oxidation stability was significantly improved. Cone calorimetry analysis showed that the peak heat release rate, total heat release, and effective heat combustion of the treated samples were substantially reduced compared with the control sample at 50 kW/m². LOI, TG, vertical burning and cone calorimetry showed that the PBN treated samples had good flame retardancy and thermal stability.