Structure and Properties of Phosphorus Flame Retardant Copolyester

A series of flame retardant copolyesters were prepared by polymerization reaction using phosphorus flame retardant CEPPA as the third monomers. The chemical composition, sequence distribution, crystallization property, phosphorus content and limiting oxygen index of the flame retardant copolyester were characterized by means of NMR, DSC, elemental analysis and limiting oxygen index instrument. Results showed that a majority of CEPPA units were copolymerized into the copolyester chains in a form of random distribution; part of CEPPA units were copolymerized in the flame retardant polyesters in a form of short segment, and the random coefficient of the copolyester decreased as the flame retardant contents increased. Compared with PET, Tg, Tm and degree of crystallinity of the flame retardant copolyester decreased, which was ascribed to the decline of the regularity of the copolyesters chains. Moreover, limiting oxygen index values also increased with the increasing of the flame retardant content, as the phosphorus content of the flame retardant copolyester was 9.08 mg/g, the limiting oxygen index values can be more than 33%.