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Polyethylene terephthalate

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Polyethylene terephthalate
800px-Polyethylene terephthalate.svg.pngBottles-60477 960 720.jpg
General
IUPAC name Poly(ethyl benzene-1,4-dicarboxylate)
Other names PET, PETE
Molecular formula (C10H8O4)n
Molar mass variable
CAS number 25038-59-9
Properties
Density and phase 1.38 g/cm3 (20 °C),

amorphous: 1.370 g/cm3,
single crystal: 1.455 g/cm3

Solubility in water practically insoluble
Melting point [250 °C, 260 °C
Boiling point 350 °C (decomposes)
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
Disclaimer and references

Polyethylene terephthalate is the chemical name for polyester commonly known as PET. PET used in rigid or synthetic fiber fabrics, and a member of the polyester family of polymers. When used for containers and other purposes, it is called PET or PET resin. PET is one of various engineering plastics which is widely used in the manufacture of high strength fibers, audio and video tapes and various kinds of packaging materials, mainly soft drink bottles and jars. It is a growing interest in the recent use of PET wastes for low production of specialty products such as saturated and unsaturated polyester synthesis feed stocks. And polyethylene terephthalate uses of metals and glass for food packaging is even more being replaced by plastics in applications where high barriers to steam and gas are required. However, plastics are previous to various gases and can be attacked by several organic products. As a result, research into and the development of new and improved plastic materials has escalated.[1]

Properties

Chemical

Polyethylene terephthalate (PET) is construct by polymerization of ethylene glycol and terephthalic acid. Ethylene glycol is a colorless liquid obtained from ethylene and terephthalic acid a crystalline solid obtained from xylene. When heated together under the affection of a chemical catalyer, ethylene glycol and terephthalic acid produce PET in the form of a molten viscous mass, and PET can be co-extruded directly into fiber or later processed into plastic. The presence of a large aromatic ring in the PET repeating units imparts notable stiffness and strength to the polymer, especially when the polymer chains are aligned with each other in a regular arrangement by stretching. PET is made from high-strength plastic that can be molded in any common way used with other thermoplastics.[2]

Physical

Natural polyethylene terephthalate (PET) is a colorless semi-crystalline resin. PET can be semi-rigid, and very lightweight. It is strong and impact-resistant. PET becomes white when exposed to certain chemicals such as chloroform and toluene. Crystallization of about 60% is the upper limit of commercial products except for polyester fibers. The transparent product can be produced by quenching the molten polymer below the Tg glass transition temperature to form an amorphous solid. Like glass, amorphous PET is formed when molecules do not have enough time to cool down in a regular, orderly way when cooled. [3]At room temperature, the molecules are stationary, but once sufficient heat energy has been reintroduced by the heat above Tg, they will begin to move again and nucleate and grow crystals. This procedure is known as solid-state crystallization. Upon slow cooling, the molten polymer forms a more crystalline material.This material contains spherical fossils containing many small crystals when crystallized from amorphous solids rather than forming a single large single crystal.[4]

Synthesis

Polyethylene terephthalate 3D balls

Polyethylene terephthalate (PET) is made through a simple dehydration reaction between ethylene glycerol and terephthalic acid. The synthesis of polyethylene terephthalate is an example of a condensation polymerization. This reaction will be repeated as necessary until an appropriate long chain is formed. And polyethylene terephthalate was alcoholised with ethylene glycol to synthesize hydroxytelechelic oligomers of PET. The competition for this synthesis is dehydration of the carboxylic acid on both sides of the terephthalic acid. Theoretically the hydroxide group can fall into water after hydrogenate. [5]

Uses

Polyethylene terephthalate is transparent, strong and lightweight plastic. It is widely used in packaging of foods and beverages, especially convenient soft drinks, water and juice. Morally all single serving and 2 liter bottles of carbonated soft drinks and water sold are made from PET in the United States of America. Also packaged salad dressings, peanut butter, cooking oils, mouthwash, shampoo, liquid hand soap, window cleaners, and even a tennis ball are also popular. Special grades of PET are used to transport food trays and food containers that can be heated in ovens or microwave ovens. PET has also been used as a substrate in thin film solar cells, and since late 2014 it has been used as a liner material for Type IV composite high pressure gas cylinders and 3D printable thermoplastics.[6]

History

Polyethylene terephthalate was first synthesized by DuPont chemists during the mid-1940s, who were searching for polymers that could be used to make new textile fibers in the United States of America. Later, DuPont would make a brand these polyester fibers as "Dacron." In the late 1950s, researchers found a way to stretch a thin extruded sheet of PET to create PET film, which today is used extensively as video, photographic and X-ray film, as well as for packaging films. In the early 1970s, this technology was developed to blow stretch PET into a powerful, lightweight, fragile bottle. In 1973, PET bottles were patented and soon entered the market. In 1977, the first PET bottle was recycled. Today, PET is one of the most widely used and reliable materials in the world. More than half of the world's synthetic fiber is made of PET, and almost all individual sizes sold in the United States and 2 liter bottles of carbonated soft drinks and water are made of PET resin.[7]

Video

This is the Polyethylene Terephthalate Polymerization video.

References

  1. The Editors of Encyclopædia Britannica. Polyethylene terephthalate (PET or PETE) ENCYCLOPAEDIA BRITANNICA.2017.
  2. The Editors of Encyclopædia Britannica. Polyethylene terephthalate (PET or PETE) CHEMICAL COMPOUND ENCYCLOPÆDIA BRITANNICA. Unknown author.
  3. Polyethylene terephthalate WIKIPEDIA.20 November, 2017.
  4. AZoM. Polyethylene Terephthalate Polyester ( PET, PETP ) - Properties and Applications - Supplier Data by Goodfellow AZO METERIALS.June 25, 2003.
  5. Bernard Boutevin. Synthesis of (polyethylene terephthalate/polyϵ-caprolactone) copolyesters sciencedirect. Web. June 2003.
  6. FAQs - Frequently Asked QuestionsPET Basics | Uses for PET | PET Safety | Recycling & Sustainability PETRA PET Resin Association.2015.
  7. Polyethylene terephthalate (PET) PLASTICS HISTORICAL SOCIETY. 1986.