A novel reactive flame retardant for cotton fabric based on a thiourea-phosphoric acid polymer

A novel polythiourea-phosphoric acid-based flame retardant containing high amounts of phosphorus, nitrogen, and sulfur elements was synthesized and successfully applied to cotton fabrics. This formulation provides greatly improved flame retardancy of cotton fabrics. Infrared spectroscopy and elemental analysis verified the presence of phosphorus, nitrogen and sulfur elements in the flame retardant cotton. Scanning electron micrographs revealed that the introduction of flame retardant showed little effect on the fiber structure of cotton fabrics. Under nitrogen atmosphere, the degradation temperature of the treated cotton was reduced 72 degrees C compared with raw cotton, with weakened degradation degree of the treated cotton and a residue ratio that was significantly increased to 49.06 %. The cone calorimetry results showed that the mean heat release rate of raw cotton decreased from 9.20 to 4.83 kW/m(2) of treated cotton, and the total heat release decreased from 2.83 to 1.45 MJ/m(2) after treatment. The experimental results indicate that 30 % flame retardant can impart good durability and excellent flame retardancy to cotton fabrics. Moreover, the mechanical performance tests demonstrated little effect on the strength of cotton fibers.