High self-extinguishing and thermal insulating PA66 composites enhanced with flame-retardant cellulose nanocrystals

Polyamide 66 (PA66), a globally attractive high-performance plastic, is hindered by its poor fire resistance, which triggers excessive smoke and dripping. In this work, we introduce a novel halogen-free, thermal insulating flame-retardant for PA66, modified by cellulose nanocrystals (CNCs) with 3-aminopropyltriethoxysilane (APTES) and phosphoric acid (PA) to form a spider web-like nano composite CNC/A/P, by improving the thermal stability and inhibiting the droplet phenomenon of PA66. This high self-extinguishing flame retardant owns a 56.9 % residual carbon rate and the limiting oxygen index of 42.74 %. PA66-C15, incorporating 15 wt% CNC/A/P, significantly enhances PA66's flame retardancy, achieving a V-0 rating, and a rising LOI of 46.7 % from 21.6 %. Surprisingly, a 114.3 % temperature reduction (194.1 °C) under heating alcohol lamp were also observed in this PA66 composite, preserving superior tensile strength mechanical properties and thermal insulation. This study presents a promising, high-performance CNC-based flame-retardant material with excellent fire retardancy and mechanical properties.