Thermal analysis of polyesters containing oxirane groups

The preliminary studies of the thermal behaviour of polyester obtained in polycondensation process of cyclohex-4-ene-1,2-dicarboxylic anhydride and ethylene glycol and its new epoxidized florin have been performed. The thermal characterization of initial polyester and its completely oxidized form was done by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The non-isothermal DSC was applied to determine the influence of time and the temperature on the chemical modification of initial polyester using 38-40% solution of peracetic acid. On the basis of DSC profiles it has been found that the endothermic transition, due to the degradation process of initial polyester was characteristic feature under controlled heating program. The two characteristic transitions for the new epoxidized polyester, the exothermic peak corresponded to the thermal crosslinking of epoxidized polyester (322.8-336.4 degrees C) and the endothermic decomposition peak of the cured material (363.8-388.9 degrees C) were observed. The peak maximum temperatures (T,,,,,) and the heat of cross-linking reaction (Delta H-c) for epoxypolyester prepared at 20-60 degrees C under 1-4 h were evaluated. The T were almost independent from epoxidation conditions, while, the values of Delta H-c were dependent from conditions of synthesis. The Delta H-c values of this process decreased when time of oxidation increased. The highest values of Delta H-c at 40 degrees C were obtained. Additionally, TG experiments confirmed two separated degradation steps of the new epoxidized polyester indicating the ester (370-380 degrees C) and ether (450-460 degrees C) bond breakdown.