Vol.15 No.1Chinese Journal of Reactive Polymers●65●work was called PETA90.)HHO一.CH2-CH2-OH + HOOC-CH- -CHg===二HO-- CH2 CH2-0- c一 -CH- CHg+ H2OEGALEScheme 1 Esterification of EG and LAQH QtCatHOOC-COOH+ HO- CH2 -CH2-0-- -C- -CH- -0H + H2C-- -CH2Polycondensation.E CHsTPAO一CO-CO- -0- -CH2--CH2- 0-CHgPETAScheme 2 Synthesis of Random Copolyesters of Poly(lactic acid-co-glycol terephthalic acid)The same process was applied for the synthesis of the copolyesters PETA80, the ratio of nEG :nLA was 1.5: 1, and nTPA : nLA was 80 : 20. For the PETA70, the ratio of nEG: nLA was 1.5 :1, and nTPA : nLA was 70: 30. For the PETA60, the ratio of nEG: nLA was 1.5: 1, and nTPA :nLA was60 : 40. And for the PETA50, the ratio of nEG : nLA was 1.5: 1, and nTPA : nLA was .50: 50.2.3 Purification of PETAThe reaction product 5g was dissolved in 100ml~ 150 CHCl3 and filtrated, then precipitated in3 times of cold methanol. The precipitated PETA was isolated and dried at 50°C in vacuum. Soin this work the final purification product were chosen as samples in all the course ofmeasurements.2.4 M [easurements2.4.1 FT-IR SpectroscopyThe samples after incubation were studied by FT-IR spectroscopy and the FT-IR spectra wererecorded on a NICO- - -LET170S IR apparatus.2.4.2 DSC MeasurementsHeat histories of samples were removed and they were kept at ambient temperature for days toallow their crystallization to approach the equilibrium state prior to the DSC characterization.DSC measurements of copolyesters were carried out on a Pyrisl differential scanning calorimeterequipped with a liquid nitrogen cooling system under a nitrogen flow at a rate of 50 ml/min. Thesamples of about 8mg~ 10mg were encapsulated in the DSC aluminum pans and then thermallyIYHCNMHG