Study on the Structure of Poly(ethylene terephthalate) with Thermal-oxidative Aging

Abstract

Polyethylene terephthalate (PET) is widely used in food and pharmaceutical packaging. In the processing, storage and use of the process, it will inevitably be in contact with air at a certain temperature, resulting in thermal-oxidative aging. So in this paper, the hot air exposure test was used to investigate the changes of structure before and after thermal-oxidative aging of PET by means of FTIR, DSC, UV-visible spectroscopy and fluorescence spectroscopy. IR study found that, after thermal-oxidative aging, the trans conformation of PET increased, the cis content decreased, and the carboxyl content of PET increased slightly. DSC analysis showed that the melting temperature, crystallization temperature and crystallinity of PET increased after thermal-oxidative aging. The results of IR, UV/Vis and fluorescence spectra showed that the crystallinity of PET increased after thermal-oxidative aging, the color difference (C) and the transparency (T%) increased, the yellow index(YI) decreased and the content of trans conformation was higher.