Abstract: A series of co-polyesters ［poly(propylene-co-ethylene terephthalate), PPET］ were synthesized by adding various contents of 1,2-propylene glycol (PG) through a direct esterification method. Their structures were characterized systematically and their crystallization property and thermal performance were investigated. Gel permeation chromatography analysis indicated that the PPET has a number average molecular weight of over 29000 and a molecular weight distribution of 1.9~2.1. Nuclear magnetic resonance (NMR) spectroscopic characterization suggested that the weight fraction of PG remained in macromolecular chains was lower than its feed ratio, indicating that PG was more difficult to be introduced into the macromolecular chain than EG. Differential scanning calorimetry analysis demonstrated that the crystallization capability of PPET was reduced in comparison with poly(ethylene terephthalate) (PET), and their melting point also decreased by 24 ℃ when 20 wt % PG was incorporated. In addition, PPET exhibited a thermal stability similar to the conventional PET polyester according to thermogravimetric analysis.

Key words: 1, 2-propylene glycol, modified copolyester, structure, crystallization, themal property