Polyphosphazene–Tannic Acid Colloids as Building Blocks for Bio-Based Flame-Retardant Coatings

Colloids using hexachlorocyclophosphazene (HCCP) and natural polyphenol tannic acid (TA) were synthesized for the first time under precipitation polycondensation conditions. The synthesis parameters were optimized to obtain submicrometer cross-linked polymer colloids with variable TA/HCCP ratios. Using thermogravimetric analysis coupled with FTIR spectroscopy, we demonstrate that TA/HCCP particles exhibit high thermal stability and high char-forming ability. Synthesized polymer colloids can be easily redispersed in water, forming colloidally stable dispersions as confirmed by dynamic light scattering. Aqueous formulations of TA/HCCP particles were used to coat cotton samples. TA/HCCP coatings exhibit excellent flame-retardant properties with a maximal limiting oxygen index (LOI) of 35.