Synthesis of a formaldehyde-free flame retardant for cotton fabric

A flame retardant ammonium salt of diethylene glycol phosphonate (ADGP) is synthesized using low-cost materials (diethylene glycol, phosphoric acid, and urea). The flame retardant is grafted on the cotton fabrics via P–O–C covalent bonds. The structure of the flame retardant is characterized by nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR). The combustion performance of the treated and untreated cotton fabrics is evaluated based on vertical flammability, limiting oxygen index (LOI), and cone calorimetry. As the concentration of the flame-retardant ADGP increased, the cotton fabric treated with 40% ADGP exhibited an LOI of 43.7% and superior fire resistance, whereas physiological comfort showed a decrease. Scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction were used to characterize the surface morphology, chemical composition, and crystal structure of the control and treated cotton fabrics. The thermal stability of the treated and untreated cotton fabrics is determined by thermogravimetric analysis. The results indicated that the treated cotton showed superior flame retardancy.