The effect of metal catalyst on the discoloration of poly(ethylene terephthalate) in thermo-oxidative degradation

Titanium-based catalyst and ethylene glycol antimony were used as catalysts to prepare poly(ethylene terephthalate) (PET), and the effect of the catalysts on the discoloration of PET in thermo-oxidative degradation was studied by UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR) and fluorescence spectroscopy. Hydroxylation was found during thermo-oxidative degradation of both the titanium- and antinomy-containing PETs. However, more hydroxylated products were further changed into quinonoid species in the presence of titanium catalyst, which directly results in obviously enhanced coloration of the PET. It indicates that the PET synthesized with titanium-based catalysts is more susceptible to formation of quinonoid groups and discoloration than the PET prepared with ethylene glycol antimony.