Solvent‐Free Strategy for Preparation of Carbon Dots From <scp>PA66</scp> Waste and Its Application in Flame Retardant Modification of <scp>PET</scp> Fabrics

ABSTRACT Polyamide 66 (PA66) is the most widely produced and used engineering plastic, and it also holds a significant position in the field of chemical fibers, resulting in a large amount of PA66 waste. Recycling PA66 waste not only helps alleviate environmental pollution caused by PA66 waste but also reduces the consumption of fossil resources, which has important practical significance. In this paper, PA66 waste and phytic acid were used as precursors to prepare PA66‐based carbon dots (66CDs), a novel zero‐dimensional carbon nanomaterial, through a solvent‐free one‐step pyrolysis method. The optimal excitation and emission wavelength of the prepared 66CDs is 410 nm and 500 nm, and the fluorescence quantum yield is 25.42%. The average particle size of 66CDs is 3.30 nm, and the lattice spacing is 0.21 nm, with surface functional groups such as –OH and –NH 2 . Subsequently, the as‐prepared 66CDs were used for flame retardant finishing of polyester fabrics through double‐dip‐double‐nip method. When the concentration of 66CDs is 10 g/L, the weight gain of the polyester fabric is 1.69% and the limit oxygen index value reaches 29%. The ignition time of finished polyester fabric reaches 219 s with an improvement of 10.60% compared to pure polyester fabric, and the damage length decreased 39.20% compared to pure PET, thus enhancing fire safety of polyester fabric. The study on the flame retardant mechanism indicates that 66CDs play a role in quenching free radicals and promote the formation of a dense char layer in the polyester fabric, thereby achieving the flame retardant effect.