2025 Volume 74 Issue 7.8 Pages 335-340
The low-temperature depolymerization method, which has been developed at the National Institute of Advanced Industrial Science and Technology, and the current high-temperature depolymerization method for polyethylene terephthalate (PET) were comparatively evaluated to assess their usefulness for chemical recycling. The evaluation was conducted based on the results of the chemical structure analysis of the dyes contained in PET fibers and their depolymerization products. A liquid chromatograph-quadrupole mass spectrometer equipped with a photodiode array detector was used for the analysis of dyes, and a reprecipitation method was employed for the extraction of dyes from polyester fibers to prevent changes in the chemical structure of dyes during extraction. Mass spectral calibration software and internet databases were used to estimate the chemical structure of the dyes. The results of this study indicate that low-temperature depolymerization leaves behind much less dye-derived compounds in the depolymerization products than high-temperature depolymerization. Moreover, in some cases, the structure of dye-derived compounds obtained by low-temperature depolymerization can be estimated. Using the low-temperature depolymerization method is expected to improve the efficiency of the purification process of PET chemical recycling products.
