Preparation and Application Properties of Cyclic Polysiloxane Flame Retardant Containing Phosphorus and Nitrogen for Cotton Fabrics

Poly[tetra(tetramethylcyclosiloxyl-piperazin)-phosphinic acid methyl ether) (PNCTSi) was successfully synthesized, and its chemical structure was investigated by Fourier transform infrared spectra (FTIR) and nuclear magnetic resonance ( ¹ H-NMR and ¹³ C-NMR) spectroscopy. The flammability and thermal decomposition behaviors of cotton fabrics treated with PNCTSi were systematically evaluated by limiting oxygen index (LOI), vertical burning test (UL-94), thermogravimetric analysis (TGA), and cone calorimetry. As a result, the LOI value reached 30.1% and the char length decreased to 10.3 cm when cotton fabrics were treated in 300 g/L of PNCTSi solution for 30 min. According to TGA results, the residual rate of treated cotton fabrics at 800 °C increased to 16.4%. The peak heat release rate (PHRR) and CO ₂ /CO ratio significantly decreased.