Effect of phosphorus-containing inorganic-organic hybrid coating on the flammability of cotton fabrics: Synthesis, characterization and flammability

A kind of novel inorganic-organic hybrid coating (PPD-PTES) containing phosphorus, silicon and nitrogen elements was successfully synthesized and deposited on cotton fabric through a sol-gel process to improve the flame retardant properties. Fourier transform infrared spectroscopy, ¹H-, ¹³C-, ²⁹Si- and ³¹P-nuclear magnetic resonance were carried out to characterize the structure of the inorganic-organic hybrid coating. The surface morphology, flammability and thermal degradation properties of the untreated and coated cotton fabrics were investigated by scanning electron microscopy, vertical burning, microscale combustion calorimetry, thermogravimetric analysis coupled with Fourier transform infrared analysis. The PPD-PTES coating system improved the thermal stability of the cotton because of the protective effect of underlying cotton from degradation, and also badly increased the char yield. In the vertical burning test, cotton fabrics treated with the PPD-PTES hybrid coating self-extinguished immediately when the ignition source was removed, while uncoated cotton was burned out. The superior fire retardant performance was assigned to the formation of thermally stable char layer on cotton fibers which effectively inhibited oxygen and heat transfer when it was burning. The results obtained here will enlarge the application of silicon-phosphorus hydrogel to flame retard cotton fabrics.