Synthetic novel, convenient and eco-friendly Si/P/N synergistic treatment agent to improve the flame retardancy and thermal stability of cotton fabrics

Abstract

Modified flame retardant cotton fabrics were prepared by introducing a novel aminoethylpiperazine spirocyclic pentaerythritol bisphosphonate functional heptamethyltrisiloxane (ASPBH). The structure of the synthesized ASPBH was characterized using nuclear magnetic resonance (1H and 31P) and Fourier transform infrared spectra (FTIR). ASPBH successfully attached to the surface of cotton fibers, which was proved by the results of scanning electron microscope (SEM) combined with energy dispersive X-ray spectroscopy. The flame retardancy of ASPBH-treated cotton fabrics was further improved. The limiting oxygen index (LOI) value reached 30.4%, the residual char length was reduced to 7.5 cm, and there was no afterflame and afterglow. However, the LOI of untreated cotton fabric is only 18%, and the vertical burning test cannot be completed. Thermogravimetric analysis results showed that the modified cotton fabrics has excellent thermal stability, which can also be seen from SEM analysis of char residues. In addition, addition of ASPBH caused the peak heat release rate and total heat release decrease from 232.1 to 177.2 kW/m2 and from 6.5 to 5.0 MJ/m2, respectively. And the treated cotton fabrics released less smoke than untreated ones during the combustion, which would greatly reduce combustion harm. Based on analysis of condensed phase at different temperatures, the thermal degradation mechanism of ASPBH on cotton fabrics was presumed. A novel aminoethylpiperazine spiro pentaerythritol bisphosphonate functional heptamethyltrisiloxane (ASPBH) can be dissolved in a mixed solution of ethanol and water to prepare a flame retardant treating solution. The original cotton fabric was immersed for a certain period of time under certain conditions, then it was dried and solidified to complete finishing process. Treated cotton can form a stable SiO2 char layer at high temperature and release less smoke.