I. Food grade ① Protected food should have all the technical properties required to protect food, such as the corresponding air permeability, moisture permeability, chemical stability, physical and mechanical properties, sealability (determined with a seal tester), light shielding, Fragrance and so on. ② Adaptability of production process It can meet the requirements of packaging mechanization and automated production processes, such as the sterilization and sterilization of materials, forming, filling (sometimes hot filling) and sealing operations, to ensure production efficiency and packaging quality. ③ Promote sales Packaging materials and containers should have good sales appearance and adaptability to printing and decoration, which will help to increase the value of food commodities and be attractive and competitive in the market. ④ Hygiene and safety Food packaging materials must not have any adverse effects on food, including any odor and pollution of harmful ingredients, to ensure the health and safety of food; at the same time, it should make consumers feel safe and hygienic. ⑤Other, long-term issues such as the economics of packaging, saving resources, energy, and post-processing recycling of packaging waste, environmental sanitation, and ecological balance
Second, PET polyethylene terephthalate chemical formula -OCH2-CH2OCOC6H4CO- English name: polyethylene terephthalate, referred to as PET, is a high polymer, derived from the dehydration condensation reaction of polyethylene terephthalate. Ethylene terephthalate is obtained by the esterification reaction between terephthalic acid and ethylene glycol. PET is a milky or light yellow, highly crystalline polymer with a smooth and shiny surface. It has excellent physical and mechanical properties in a wide temperature range. The long-term use temperature can reach 120 ° C. The electrical insulation is excellent. Even at high temperature and high frequency, its electrical performance is still good, but the corona resistance is poor. Creep, fatigue resistance, friction resistance, and dimensional stability are all very good. ① Has good mechanical properties, impact strength is 3 to 5 times that of other films, good folding resistance ② Resistant to oil, fat, dilute acids, alkalis, and most solvents. ③ It has excellent resistance to high and low temperature. It can be used for a long time in the temperature range of 120 ℃. It can withstand high temperature of 150 ℃ and low temperature of -70 ℃ for a short time. ④ Gas and water vapor permeability is low, that is, it has excellent gas barrier, water, oil and odor performance. ⑤ High transparency, can block ultraviolet rays, good gloss. ⑥ Non-toxic, odorless, good hygiene and safety, can be directly used in food packaging.