Smart Crosslinkable Aromatic-Imine Enables Integrated Heat-Resistance, Flame Retardancy, Smoke Suppression and Non-Dripping for Polyester

The increasing fire risk in modern society urgently requires high-performance flame-retardant protective polymer materials. Polyester is a versatile thermoplastic polymer widely used in fiber textiles, films, and plastics. However, it remains a huge challenge to simultaneously achieve green preparation, heat resistance, flame retardancy, smoke suppression and non-dripping for polyester materials. Herein, we propose a halogen-free and phosphorus-free green strategy for synthesizing flame-retardant, smoke-suppressed and non-dripping polyesters with enhanced heat resistance. By chemically copolymerizing an aromatic-imine containing monomer CID, the corresponding polyester PET-CID exhibits an increased glass transition temperature of 84.0°C, a limiting oxygen index of 31.5%, a 42% reduction in peak heat release rate, a 45% reduction in peak release smoke rate, and passes the UL-94 V-0 rating without melt dripping. The key is that the smart crosslinkable aromatic-imine remains stable at the synthesis and processing temperatures of the polyester. At higher temperature during combustion, aromatic-imine rapidly crosslinks to increase the melt viscosity of the polyester and promote the formation of a dense char layer. This work simultaneously integrates the high heat resistance, flame retardancy, smoke suppression and non-dripping of polyester through a single aromatic-imine group, paving the way for the green development of high-performance flame-retardant polymer materials with low fire hazards.