Amino acid flame-retardant finishing of poly-(ethylene terephthalate) (PET) fabrics based on supercritical CO2

The majority of conventional flame retardants are made by chemical processes using petroleum resources, which cause serious pollution and waste of resources in the ecological environment. In this paper, flame retardants such as L-aspartic acid, DL-serine, L-tyrosine, L-lysine, L-phenylalanine, L-histidine, L-tryptophan, and glycine were employed to finish poly-(ethylene terephthalate) (PET) fabrics with supercritical CO₂ fluid. Scanning electron microscope (SEM) and Energy dispersive spectroscopy (EDS) were used to examine. the microstructure and chemical composition of flame-retardant PET fabrics. The limiting oxygen index (LOI) test and the vertical combustion test were used to assess the flame-retardant qualities of PET fabrics. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to test and assess the thermal properties of PET fabrics. The strength test was used to assess the mechanical properties of PET fabrics. The results showed that the amino acid flame retardants were successfully finished on the PET fabrics by supercritical CO₂ (SC-CO₂) technology and improved the thermal stability of the PET fabric. In comparison to untreated PET fabric, the elongation at break was 13–15 % greater, and the breaking strength was not reduced. Among them, the PET fabrics treated with L-aspartic acid and L-lysine had better flame-retardant performance, there were no droplets, the LOI values were greater than 30 %, and the char length was less than 10 cm. After 45 minutes of soaping and 3 times of washing, the LOI values were still above 28 %, and there were no droplets. Therefore, the PET fibers treated with amino acids using SC-CO₂ technology effectively improved the flame-retardant performance of PET fabrics.