Improving the flame retardant and anti-dripping performance of polyamide 66 inspired by vegetable tanning

Vegetable tanning is an ancient process that uses polyphenols to transform animal hides and pelts into durable and structurally stable leather. Inspired by this, polyamide 66 (PA66) and keratin (Ker) were blended to fabricate a PA66 composite (PA66/Ker) by solution casting, which was then tanned to prepare flame retardant and anti-dripping PA66/Ker composite (FR-PA66). The results indicated that the peak of heat release rate (PHRR) and total heat release (THR) of FR-PA66 decreased by 75.3% and 38.4%, respectively. The limiting oxygen index (LOI) of FR-PA66 reached 29.65% and a UL-94 V-0 rating was obtained. In addition, the char residue of FR-PA66 was 21.6% at 800 °C under N2 atmosphere, indicating good char-forming ability. This work provides a new idea by using renewable biomass keratin and tannin to endow PA66 with flame retardant and anti-dripping performance. The preparation process is simple and feasible, suitable for large-scale preparation.