A starch-based, durable phosphorous-containing flame retardant for cotton

A starch-based, durable phosphorus flame retardant, ((bis((dimethoxy phosphoryl)methyl)(hydroxymethyl)phosphonio)methyl)-1,10-bis(dimethoxyphosphoryl)-4,7-diaza-2,9-diphosphadecane (BMPTHD), was synthesized. The structure of the flame retardant BMPTHD was analyzed using NMR and FTIR. These test results indicated that the BMPTHD was successfully synthesized. After treatment, the limiting oxygen index (LOI) values of the cotton fabric increased from 17.9 % to 39.6 %, the total heat release (THR) decreased 49.29 %, the flame growth rate (FGR) slowed down by 81.02 %, showing good flame retardancy and passing the vertical flame test (VFT). The Thermogravimetric analysis (TG) test results show that after flame retardant treatment, the char residue rate of the fabric in N₂ atmosphere has significantly increased from 1.13 % to 38.17 %. Under O₂ atmosphere, the char residue rate also increased from 0.01 % to 7.34 %. After undergoing 50 laundering cycles (LCs) in accordance with the NFPA 2112-2012 washing standard, the cotton fabric can still pass the VFT, demonstrating significant flame retardant durability. The cone calorimetry test (CCT) results indicate that BMPTHD effectively slows down the peak heat release rate (PHRR), reduces the total heat release (THR), and hinders the spread of the flame. In thermogravimetric (TG) tests and thermogravimetric infrared (TG-IR) tests, the residue from CN-BMPTHD treated fabric was significantly higher than that of untreated cotton, and the production of combustible gases was reduced. This indicates that BMPTHD is a condensed-phase flame retardant.