Entirely Bioderived Intumescent Flame-Retardant Coating for Polyamide Textiles

Polyamide 6,6 (PA6,6) is one of the most widely used synthetic textile fibers for consumer and industrial applications, but its inherent flammability and melt-dripping behavior present significant fire hazards. A fully bioderived intumescent flame retardant for PA6,6 textiles was developed using tannic acid (TA), chitosan (CS), and guanidine phosphate (GP). The coating was designed as an effective flame-retardant formulation that conformally coats PA6,6 fibers to minimally impact mechanical properties. Additionally, all materials used were derived from biological feedstocks to minimize the use of petroleum-derived materials. All coated PA6,6 samples eliminated melt dripping during vertical flame testing and achieved self-extinguishing behavior. The limiting oxygen index was increased from 23.5% to 27%, and the peak heat release rate measured by cone calorimetry was reduced by 56%. Overall, this work demonstrates an effective and scalable, bioderived, intumescent coating capable of significantly improving the fire safety of PA6,6 textiles.