Used primarily as a byproduct in the production and recycling of polyethylene terephthalate (PET) plastics and fibers. It serves as a marker for thermal degradation of PET during processing or recycling, helping assess material quality and thermal history. Due to its cyclic structure and thermal stability, it is also studied in research related to polymer degradation mechanisms and recycling technologies. In some cases, it is used as a model compound for analyzing trace contaminants in food packaging materials where PET is in contact with food, especially under high-temperature conditions. Its presence is monitored to ensure compliance with food safety regulations, as it can migrate in small amounts into food or beverages.