Study on thermal oxidation degradation of PET-PTMG poly(ether-ester)s
Poly(ethylene terephthalate)-poly(tetramethylene glycol)(PET-PTMG)poly(ether-ester)s were synthesized by melt polycondensation.The thermal degradation reaction of PET-PTMG copolymers with differ-ent polyether contents in the presence of oxygen was investigated using thermogravimetric analysis.The re-sults showed that the introduction of polyether structures into copolymers resulted in poor thermal stability and sensi-tivity to oxygen.The degradation activation energy of PET and PET-PTMG copolymers in air was calculated using the Kissinger method.PET exhibited a two-step reaction,with an apparent activation energy(Ea)of 179 kJ/mol for the first step and 148 kJ/mol for the second step.The copolymers with different polyether contents exhibited a three-step reaction,with Ea values ranging from 66 to 97 kJ/mol for the first step,196 to 197 kJ/mol for the second step,and 135 to 142 kJ/mol for the third step.The application of the Flynn-Wall-Ozawa method re-vealed that the poly(ether-ester)s exhibited lower activation energy and poorer thermal stability at the initial stage of degradation.However,in the later stages of the reaction,their activation energy was higher than that of PET,demonstrating relatively better thermal stability.
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