Polyethylene terephthalate (PET) is a semi-crystalline thermoplastic polyester formed by the condensation polymerization of terephthalic acid and ethylene glycol. It can be regarded as the “dual-star of plastic bottles and synthetic fibers” - it forms high crystallinity and molecular orientation through the regular arrangement of rigid benzene rings and ethylene glycol segments, thus possessing excellent mechanical strength, fatigue resistance, good gas barrier properties (especially for carbon dioxide and oxygen), as well as resistance to dilute acids, oils, and organic solvents. PET can not only significantly increase crystallinity and strength after biaxial stretching (used to make BOPET films), but also obtain transparent amorphous products through rapid cooling, and is widely used in beverage bottles (mineral water, carbonated beverage bottles), synthetic fibers (polyester fabrics, industrial yarns), food packaging boxes, audio-visual tape bases, electronic insulation films, and medical X-ray films, etc., in situations that require high strength, transparency, or fibrous form.