High fire-safety phosphorus-containing polyethylene terephthalate with well-balanced comprehensive performances by reactive blending with liquid crystalline copolyester

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With increased public awareness of fire-safety, flame retardant materials have been widely used and developed. Among them, a polyester called CPET, synthesized by the copolymerization of polyethylene terephthalate and 2-carboxyethyl (phenyl) phosphinic acid, has a good fire-safety and has been employed in the manufacture of synthetic fibers. However, the fabricated fiber made of CPET simultaneously possessing good flame retardancy and mechanical properties is a dilemma. Herein, we resolve this problem through the reactive blending of CPET with a type of thermotropic liquid crystal copolyester (PPDT) and subsequently solid-state polymerization (SSP). Thus, the fire-safety of the CPET/PPDT SSP blend improves greatly. The peak heat release rate, total heat release, and total smoke release decrease by 31.2%, 16.3%, and 11.0%, respectively, compared with those of CPET. Meanwhile, the CPET/PPDT SSP shows better crystallization and mechanical properties than CPET. The strength at yield and Young’s modulus of CPET/PPDT SSP increase by 20.0% and 15.8%, respectively. This blend shows great potential in the fabrication of fire-safety fibers with high strength.