Preparation of durable and efficient P/N synergical flame retardant and its application on cotton fabrics

Objective Cotton fabric is one of the most common natural fabrics, and has excellent moisture absorption, breathability, thermal insulation and softness, which are widely used in clothing, household tems, military and other fields. Unfortunately, the limiting oxygen index of cotton fabric is only 18 %, and it is easily ignited in the air, causing fire accidents. In addition, the flame retardant durability of flame-retardant cotton fabrics is also very important. Hence, it is necessary to prepare efficient and durable flame-retardant cotton fabrics.Method The ammonium phosphate (AHPA) flame retardant was prepared from phosphorus pentoxide and ethanolamine. The P/N-type flame retardant AHPA was heated to produce acidic substances such as polyphosphoric acid, which promoted the dehydration of the fabrics and formed a dense carbon layer. During this process, P/N-type flame retardant AHPA generated non-flammable gases, which isolated heat and oxygen, diluted combustible gases, and hindered flame spread. Flame retardant cotton fabrics were prepared by common rolling-baking-baking finishing process. The thermal stability and mechanical properties of flame retardant cotton fabrics were analyzed by vertical flammability test, limiting oxygen index test, thermogravimetric test, cone calorimetry test and universal material test.Results The test results showed that the flame retardant AHPA was successfully synthesized, and the fiber surface had been successfully covered by the flame retardant. When the concentration of flame retardant AHPA was set to 300 g/L, the LOI value of flame retardant cotton fabric had been increased to 52. 9 % from 18 %, with only 45 mm damaged carbon length. The heat release rate and total heat release of the treated cotton fabrics were decreased by 86. 1 % and 31.5 %, respectively. The flame spread rate (FIGRA) and mean effective heat combustion (Mean-EHC) were decreased from 6 kW/(m • s) and 23.5 MJ/kg to 0.3 kW/(m • s) and 15.3 MJ/kg, respectively, representing 95 % and 34.9 % reductions in each perspective. The AHPA flame retardant worked to reduce the heat release and the combustion efficiency with improved safety. In nitrogen and air atmosphere, the carbon residue of flame-retardant cotton fabrics had been greatly increased compared to the pristine cotton fabric, indicating that the thermal stability of the flame-retardant treated cotton fabrics had been greatly improved. The breaking force of the finished cotton fabrics was decreased in both warp and weft directions. After 50 washing cycles, the LOI value of the flame retardant cotton fabrics maintained at about 31.6 %.Conclusion In summary, the flame retardant AHPA endows cotton fabrics with efficient and durable flame retardant properties, self-extinguishing of fire, discontinuous smoldering phenomenon, and excellent washing durability. The flame retardant AHPA can be applied to cotton fabrics used for bedding, carpets, curtains and so on. In following-up research work, the mechanical strength of the flame retardant cotton fabrics needs be optimized, and the total smoke release should be reduced. © 2024 China Textile Engineering Society. All rights reserved.