Properties of flame-retardant cotton fabrics: Combustion behavior, thermal stability and mechanism of Si/P/N synergistic effect

A novel Si/P/N synergistic effect flame retardant was synthesized and applied to cotton fabrics. • A novel Si/P/N synergistic effect flame retardant was synthesized and applied to cotton fabrics. • Silicon and nitrogen are the main flame retardant elements, environmentally friendly and low toxicity. • Flame retardancy of modified cotton was greatly improved with LOI value over 31 %. • The peak heat release rate and total heat release of treated cotton fabrics decreased significantly. A novel silicon, phosphorus and nitrogen synergistic flame retardant, aminoethylpiperazine phosphoric acid methyl ester modified siloxane (EPSO-P) was synthesized, the structure of EPSO-P was confirmed by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The limiting oxygen index (LOI) value of cotton fabrics treated by EPSO-P increased to 31.4 %, and passed the vertical flammability test (VFT) with a residual char length of 6.3 cm. The thermal stability of samples is obviously improved after processing, and the char residue maintained 43 % at 700 °C in nitrogen atmosphere. The burning behavior of cotton fabrics showed that the peak heat release rate decreased from 232.1 kW/m 2 to 74.5 kW/m 2 , and the total heat release decreased from 6.3 MJ/m 2 to 2.8 MJ/m 2 after flame retardant treatment. The flame retardant mechanism of the samples was analyzed by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and thermogravimetric analysis coupled with fourier transform infrared analysis (TG-FTIR). The results indicated that the EPSO-P can prevent the fabrics from burning in gas phase and condensed phase. This work proved that EPSO-P is enlightening for the production of flame retardant cotton fabrics with considerable properties.