Abstract: In this paper, aspartic acid and lysine were used as flame retardants, and the flame-retardant finishing of PET fabric was carried out by supercritical CO₂ technology. The effects of flame retardant dosage, temperature, pressure, and time of supercritical treatment on the flame-retardant performance of PET fabric were discussed. The mechanical and thermodynamic properties of PET fabric after flame-retardant finishing were tested. The results showed that the flame-retardant performance increased with the increase in the amount of flame retardant and the increase in temperature and pressure during supercritical treatment. The optimal finishing process was determined as flame retardant at 10% o.w.f., with supercitical conditions of 25 MPa, 135 °C and 60 min. The char length of PET fabric after aspartic acid or lysine finishing was less than 10 cm, and the LOI value was greater than 30%. The breaking strength of the PET fabric increased by 94 N and 76 N, respectively, and the elongation at break increased by 14.6% and 15.1%, respectively. The melting enthalpy and residue increased slightly, indicating that the mechanical and thermodynamic properties of the PET fabric after flame-retardant finishing were improved. After repeated washing, the LOI values of PET fabrics can reach no less than 28%.

Key words: supercritical CO₂, flame-retardant finishing, polyethylene terephthalate (PET) fiber, aspartic acid, lysine