Polyethylene terephthalate (PET) is the most important variety of thermoplastic polyester. Its English name is PET or PEIT, commonly known as polyester resin. The molecular weight of the repeating unit is192g/mol. It is a polycondensate of terephthalic acid and ethylene glycol. Together with PBT, it is called thermoplastic polyester or saturated polyester.
1946, the first patent for preparing PET was published in Britain, 1949, and the pilot test of ICI formula in Britain was completed. However, after purchasing the patent, DuPont Company of the United States set up a production device at 1953, which took the lead in realizing industrial production in the world.
In the early days, PET was almost entirely used in synthetic fibers (commonly known as polyester and polyester in China). Since 1980s, PET has made a breakthrough as an engineering plastic, and has successively developed nucleating agents and crystallization promoters. As thermoplastic polyesters, PET and PBT 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 processing fibers and related products in polyester fiber enterprises. Polyester is the largest variety of chemical fiber.
2. Non-fiber polyester is also used in bottles, films and other fields, and is widely used in packaging industry, electronic appliances, medical care, construction, automobiles and other fields. Packaging is the largest non-fiber application market of polyester and the fastest developing field of PET.
Advantages of PET as packaging material;
1, good mechanical properties, impact strength 3~5 times that of other films, and good folding resistance.
2, oil resistance, fat resistance, dilute acid resistance, dilute alkali resistance, resistance to most solvents.
3. It has excellent high and low temperature resistance, can be used in the temperature range of 120℃ for a long time, and can withstand the high temperature of 150℃ and the low temperature of -70℃ in a short time, with little influence on its mechanical properties.
4. The permeability of gas and water vapor is low, and it has excellent gas, water, oil and odor resistance.
5, high transparency, can block ultraviolet rays, good gloss.
6, non-toxic, tasteless, good health and safety, can be directly used for food packaging.
use
Plastic bottles made of PET are widely used as soft drinks (see carbonation). For some special bottles, such as those specially used for beer, PET will be sandwiched with an extra layer of polyvinyl alcohol (PVOH) to further reduce its oxygen permeability.
Biaxially oriented PET film (usually known by its trade name "polyester film") can be evaporated with a metal film by aluminum plating to reduce its air permeability and make it reflective and opaque (MPET). These characteristics are useful in many applications, including flexible food packaging and thermal insulation materials (such as space blankets).
Due to its high mechanical strength, PET films are often used in adhesive tape applications, such as the backing of carrier tapes or pressure-sensitive tapes.
Non-oriented PET sheets can be thermoformed to make packaging trays and blister packages. If crystallizable PET is used, trays can be used for frozen dinners because they can withstand the temperatures of freezing and oven baking. Amorphous PET and BoPET are transparent to the naked eye. Color-imparting dyes can be easily prepared into PET sheets.
When filled with glass particles or glass fibers, it will become harder and more durable.
Polyester (a trademark reversed from polyethylene terephthalate) is also spliced to the top of the bell rope to prevent the rope from wearing when it passes through the ceiling.
Refer to the above? Baidu encyclopedia-pet material