Efficient and durable flame-retardant wool fabrics achieved by a facile phytic acid grafting approach

Imparting wool fabrics with durable flame-retardant properties via simple and mild methods has remained a vital research quest. This study explored the grafting of phytic acid (PA) onto wool fabrics by a mild Mannich reaction. The introduction of PA significantly enhanced the flame-retardant properties and durability of the wool fabrics. The limiting oxygen index (LOI) value of wool fabrics treated with 0.08 mol/L PA was 34.2%. After 30 washing cycles, the LOI of PA-Wool fabric still remains at 29.5%, which would be attributed to the formation of strong C-N bonds between PA and wool. Meanwhile, thermogravimetric (TG) and cone calorimeter tests (CCT) indicated that grafting of PA could significantly enhance the thermal stability and char-forming ability of wool fabrics, wherein the T 50% values increased from 341 °C to 397 °C and 407 °C to 492 °C in N 2 and air atmospheres, respectively. The char residues of PA-Wool at 700 °C were 34.9% and 30.0% in N 2 and air atmospheres, respectively, representing a significant increase compared to those of the control wool. Moreover, the morphology of the char residue became more complete after grafting phytic acid. In addition, the whiteness, tensile strength, and handle of wool fabric were all only slightly impacted by PA grafting. This research offers a new facile and mild strategy for preparing efficient and durable flame-retardant wool fabrics. • A mild grafting process has been used to produce a flame-retardant wool with the physical properties of wool unaffected. • PA covalent grafting approach shows high flame-retardant efficiency and thermal stability on wool fabric. • The PA covalent grafting approach gives the flame-retardant wool fabrics excellent washing resistance. • PA works through the action of both the condensed phase and the gas phase.