Durable and flame retardant finishing of the wool fabrics with the combination of hydroxyl-phosphoramidate and 1, 2, 3, 4-butane tetracarboxylic acid

A flame retardant (dimethyl N, N-bis(2-hydroxyletheylphosphoramidate), DMBHP) and crosslinking agent (1, 2, 3, 4-butanetetracarboxylic acid, BTCA) were combined to impart durable flame-retardant property to wool fabrics using the pad-dry-cure method. The wool fabrics exhibited a limiting oxygen index value of 30.1% and were resistant to 25 cycles of washing after treatment with 200 g/L DMBHP and 60 g/L BTCA. Besides, the results of cone calorimetry suggested that the treated wool formed an intumescent char layer. The total heat release and total smoke production of the finished wool fiber decreased by 48.1% and 39.4%, respectively. The results indicated that the DMBHP/BTCA system can markedly improve the fire safety performance of the wool fabric. Moreover, the flame retardant treatment improved the stability of thermal degradation and the residual char of treated wool remained 32.7% and 36.7% at 700 ˚C both in air and nitrogen, respectively. The possible fire retardant mechanism of the system was also studied based on the analysis of gas products and residual char.