Durable flame retardant cellulosic fibers modified with novel, facile and efficient phytic acid-based finishing agent

As a renewable, abundant, and eco-friendly bio-based compound, phytic acid (PA) possesses high phosphorus content, which is a potential flame retardant for cellulosic fibers. Generally, PA is not efficient for cellulosic fibers due to strong acidity that results in greatly reduced strength and lack of soft hand. As proved elsewhere, the compounds with phosphorous and nitrogen was reported to be an efficient flame retardant and exhibited synergistic effect for cellulosic fibers. Therefore, PA was firstly reacted with urea to synthesize a novel green flame retardant containing a high level of phosphorus and nitrogen elements, i.e., phytic acid ammonium, then it was employed for lyocell fibers through pad-dry-cure finishing process. As expected, flame retardancy and durability of finished lyocell fabrics were considerably improved, as evidenced by an increase of limiting oxygen index value up to 39.2% and still 29.7% after 30 laundering cycles. TG–MS and TG–FTIR coupled techniques demonstrate that the formation of carbonaceous residue and non-combustion gases preferably generated during thermal pyrolysis process of finished lyocell fibers.