Abstract: A series of PET-PMT(PEMT) copolyesters were synthesized by direct esterification using terephthalatic acid(PTA)ethylene glycol(EG)-2-methoxy-1,3-propanediol(MPD, obtained from conversion of bio-glycerol to displace 1,3-propanediol) as co-monomers, with different ratio of PET/PMT. The molecular structure and chemical composition of PEMT were confirmed by FT-IR and 1H NMR. Molecular mass and distributions of PEMT were determined by GPC. The intrinsic viscosity of PEMT was measured, while thermal and crystallization properties of the PEMT were characterized using DSC analysis. Results show that the chain segments of PMT containing in PEMT are much higher than the molar ratio of MPD in feed, and consequently, PEMT has higher intrinsic viscosity than PET. The crystallization degree is decreased with MPD inserting into the polyester. The crystallization and melting behavior of PEMT is similar to that of PET when the feed molar ratio of MPD to PTA is less than 0.4. The mass-average relative molecular mass(Mw), intrinsic viscosity(η), glass transition temperature(Tg), and melting point(Tm) of the synthesized PEMT-40 (the actual ratio of n（PMT）∶n（PET） is 24∶76) is 50216, 0.458 dL/g, 68.32 ℃, and 211.07 ℃, respectively. However, when the feed molar ratio of MPD to PTA is more than 0.6, the copolyester of PEMT becomes an amorphous material.

Key words: copolyester, 2-methoxy-1,3-propanediol, ethylene glycol, terephthalatic acid, characterization