A bio-resourced phytic acid/chitosan polyelectrolyte complex for the flame retardant treatment of wool fabric

A water-soluble polyelectrolyte complex (PEC) consisting of bio-resourced phytic acid and chitosan was fabricated at pH 1.3 and used to improve the flame retardancy of wool fabric by the repeated coating technique. Citric acid was used as a solvent for chitosan and a cross-linker. The PEC coated wool fabric was treated in a pH 4 buffer solution to yield a water-insoluble coating on the fabric surface. The flame retardant efficiency and durability to washing of the PEC coating on wool fabric were discussed. The growing deposit times with the PEC caused an increase in flame retardancy of wool fabric. One coating deposition with the PEC consisting of 10% phytic acid and 2% chitosan effectively ceased the fabric burning. Five depositions could still extinguish the flame on the fabric after ten washings, indicating good washing durability of the treated wool. Both the insolubilization treatment of the PEC coating and the cross-linking action of citric acid between chitosan and wool fiber were highly beneficial to the appreciable washing durability. The morphological structure of char residues revealed a significant intumescent charring mechanism for the treated wool. This study reveals that the PEC coating by bio-resourced materials can be used to prepare flame retardant wool textiles, and exhibits less processing steps and lower cost than the layer by layer assembly.