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Keywords:

  • poly(butylene terephthalate);
  • glass transition temperature;
  • melting temperature;
  • random copolyesters;
  • copolymerization;
  • melt;
  • NMR

Abstract

Poly(butylene terephthalate-co-2-methyl-ethylene terephthalate) (PBT/MET) was synthesized by incorporating 1,2-propandiol(1,2-PDO) into PBT chains. The molar composition and chemical structure of PBT/MET copolyesters were confirmed by means of FT-IR and 1H-NMR. To investigate the effect of 1,2-PDO on the thermal properties of PBT/MET copolyesters, the copolymerizations were carried out by varying various contents of MET units, and the prepared materials were evaluated by differential scanning calorimetry and thermogravimetric analysis. Results suggested that with the increase of the content of 1,2-PDO, the amount of crystallinity and the melting temperature decline, while the glass transition temperature increases and the copolyesters become more transparent and brittle with respect to PBT homopolymer. In addition, the Tg-composition and Tm-composition data are well subjected to the Wood equation and Flory's equation, respectively. All these copolyesters are found to consist of the general trend displayed by copolymers reported elsewhere. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010