Polyethylene terephthalate is the most important variety in thermoplastic polyester, English name is Polyethylene terephthalate, abbreviated as PET or PEIT (hereinafter referred to as PET), commonly known as polyester resin. The molar mass of the repeating unit is 192 g/mol. It is a polycondensate of terephthalic acid and ethylene glycol, and together with PBT, it is collectively referred to as thermoplastic polyester, or saturated polyester. In 1946, the United Kingdom issued the first patent for the preparation of PET. In 1949, the British ICI formula completed the pilot test, but after the DuPont Company of the United States purchased the patent, a production device was established in 1953, which was the first industrialized production in the world. In the early days, PET was almost used for synthetic fibers (commonly known as polyester in my country, which is really good). Since the 1980s, PET has made a breakthrough as an engineering plastic, and nucleating agents and crystallization accelerators have been developed successively. PET and PBT, together as thermoplastic polyesters, have become one of the five major engineering plastics.
PET is divided into fiber-grade polyester chips and non-fiber-grade polyester chips. ① Fiber-grade polyester is used to manufacture polyester staple fibers and polyester filaments, and is the raw material for polyester fiber enterprises to process fibers and related products. Polyester is the most productive variety of chemical fibers. ②Non-fiber polyester is also used for bottles, films, etc., and is widely used in the packaging industry, electronic appliances, medical and health, construction, automobiles and other fields. Among them, packaging is the largest non-fiber application market for polyester, and it is also the fastest growing PET market. fast field.
Advantages of PET as a packaging material:
1. It has good mechanical properties, the impact strength is 3 to 5 times that of other films, and the folding resistance is good.
2. Oil resistance, fat resistance, dilute acid, dilute alkali, and most solvents.
3. It has excellent high and low temperature resistance, can be used for a long time in the temperature range of 120 degree , can withstand high temperature of 150 degree in short-term use, and can withstand low temperature of -70 degree , and has little effect on its mechanical properties at high and low temperatures.
4. The permeability of gas and water vapor is low, and it has excellent gas barrier, water, oil and odor properties.
5. High transparency, can block ultraviolet rays, and have good gloss.
6. Non-toxic, tasteless, good hygiene and safety, can be directly used for food packaging.