Bio-based self-adhesive intumescent flame-retardant system for polyester

Polyester products account for over half of all textile fires, yet flame-retardant versions remain underutilized. Conventional flame-retardant coatings are confronted with a number of environmental, tactile and durability issues. Based on this, this study constructs a self-bonding intumescent flame-retardant system from bio-based phytic acid (PA), arginine (Arg), and chitosan (CHI), which is applied as an efficient finishing strategy for polyester. The synthesis of the flame-retardant compound PA-Arg was achieved through a straightforward ion exchange reaction between PA and Arg. Simultaneously, the dissolution of CHI in citric acid (CA) was conducted in a single step, yielding modified chitosan CA-CHI, which exhibited an adhesive effect as a carbon source. CA-CHI and PA-Arg were applied to polyester fabric by a pad-dry-cure process, forming PET@CA-CHI@PA-Arg. Experimental results indicate that PET@CA-CHI@PA-Arg reached B1 flame-retardant rating, with LOI rising from 19.8% to 29.27%, and exhibited no melt-dripping. Cone calorimetry revealed reductions in THR and PHRR by 25.5% and 32.6%. The flame retardancy mechanism of CA-CHI@PA-Arg on PET was inferred from CCT results and char residue analysis. In addition, PET@CA-CHI@PA-Arg underwent breathability, moisture permeability, tensile strength, and softness testing, successfully passing practicality tests. This work offers a sustainable strategy for bio-based flame-retardant finishing of polyester textiles.