A Highly Wash-Durable Flame-Retardant Finishing for Polyester (PET) Fabrics via a Facile Postfinishing

Wash-resistant flame retardancy is crucial, as it ensures that life-saving protection remains reliable and effective even after repeated laundering, making it a non-negotiable feature for durable safety. However, balancing the fiber’s inherent mechanical strength, wash-durable flame retardance, and practical performance is necessary yet challenging. Herein, a simple impregnation and curing strategy has been employed to modify the PET fiber with phosphate ester and 1,1,1-tris(hydroxymethyl)ethane (TME). As a result, a substantial improvement in flame retardancy was achieved, with the Limiting Oxygen Index (LOI) of the PET fabric jumping from an initial 20.9% to 37.5% post-treatment, and the tensile strength and softness of PET fabrics showed almost no decrease. Besides, the damaged length (DL) is only 7.2 cm during the vertical burning test (VBT), exhibiting significant antidroplet properties. The flame-retardant properties showed remarkable resilience to laundering, as the treated fabric passed the VBT and preserved an LOI of 35.2% after 50 washes. Due to the strong covalent bonds between PET, dimethyl methylphosphonate (DMMP), and TME, the analysis results indicate the DT coating plays a role in both condensed and gaseous phases. This work provides a valuable reference for the commercialization of high-performance, washable flame-retardant fabrics.