Comparison of differences in the flame retardancy of cotton fabrics caused by the introduction of cyclic polysiloxane into P/N organic coatings

Abstract

A new type of phosphorus- and nitrogen-containing flame-retardant coating (ASPP) was prepared, and a phosphorus–nitrogen cyclic polysiloxane flame retardant (ASPP-Si) was synthesized based on ASPP and potassium cis-tetramethyl cyclotetrasiloxanolate (KCTSi). It is found that both ASPP and ASPP-Si can enhance the flame retardancy of cotton fabrics, which can be confirmed by the limiting oxygen index (LOI) and cone calorimetry tests. The results showed that the LOI of 200 g L⁻¹ ASPP-treated cotton fabrics (ASPP cot-3) reached 32.4%, and the peak heat release rate (pHRR) dropped to 40.3 kW m⁻², in contrast with an LOI of 18% and a pHRR of 236.3 kW m⁻² for control cotton. The 200 g L⁻¹ ASPP-Si-treated cotton fabrics (ASPP-Si cot-3) increased the LOI to 31.1% and decreased the pHRR to 150.8 kW m⁻². Thermogravimetric (TG) results showed that the char-forming ability of ASPP-Si cot-3 was better than that of ASPP cot-3 at an air atmosphere, and the char residue rate of ASPP-Si cot-3 was maintained at 18.0% at 750 °C. In addition, ASPP-Si cot-3 has a better smoke suppression performance, which may be related to the introduction of cyclic polysiloxane. Based on analysis of the condensed phase at different temperatures and the result of thermogravimetric analysis coupled with Fourier transform infrared analysis (TG-FTIR), the flame-retardant mechanism of treated cotton fabrics was further investigated, indicating that treated cotton fabrics effectively exert a flame-retardant effect in the condensed and gas phases during combustion.