At present, the fresh-keeping films used for fresh foods on the market are mainly one or more polyolefin-based substances extracted from petroleum. They are widely used because they have the properties required for a variety of fresh foods. Among them, polyethylene is the most used single polymer in fresh food packaging, its inertness is extremely strong, and it is not harmful under normal conditions. Vinyl polymer is another plastic polymer polymerized by vinyl monomer. It is mostly used in food packaging to prepare liquid bottles, trays of fresh fruits and vegetables, or eggs. In addition, the polyester industry accounts for about 18% of the world's polymer output. Although there are many types, polyester is mostly used to refer to PET.