Durable flame‐retardant cotton fabric modified by water‐soluble C–N–P intumescent flame retardant

Abstract Intumescent flame retardant (IFR) is the new generation of environmentally friendly flame retardant. The improved water solubility of IFR enhances its application in cellulose‐based textiles. A water‐soluble carbon–nitrogen–phosphorus (C–N–P) ternary IFR (PTETP) was synthesized using cyanuric chloride (TCT), ethylene glycol (EG), and O‐phosphoethanolamine (O‐PEA) as starting materials. The burning performance of untreated and PTETP treated cotton fabrics was evaluated using vertical flammability test (VFT), limiting oxygen index (LOI), and cone calorimetry. The results indicate that with the increase of PTETP content, the flame retardant performance of cotton fabrics is gradually enhanced. The cotton fabric treated with 10 wt% PTETP shows no afterflame combustion, has a char length of 98 mm, and a LOI of 30.8%. Compared with pristine cotton fabric, the peak heat release rate (PHRR) and total heat release (THR) of the treated cotton fabric were reduced by 52.6% and 28.2%, respectively. Thermogravimetric (TG) shows that PTETP effectively improves the thermal stability and reduces the thermal decomposition temperature of cotton fabric, and even can increases the residual carbon rate by 20%. In addition, the employment of PTETP shows no harm on the tensile strength of cotton fabrics. After washing 20 times, LOI of flame‐retardant cotton fabric still remained almost 26%.