Polyethylene terephthalate
| Names | |
|---|---|
| IUPAC name
poly(ethylene terephthalate) | |
| Systematic IUPAC name
poly(oxyethyleneoxyterephthaloyl) | |
| Other names
Terylene (trademark);
Dacron (trademark). | |
| Identifiers | |
| Abbreviations | PET, PETE |
| ChEBI | |
| ChemSpider |
|
| ECHA InfoCard | 100.121.858 |
| UNII | |
CompTox Dashboard (EPA) |
|
| Properties | |
| (C10H8O4)n | |
| Molar mass | 10–50 kg/mol, varies |
| Density |
|
| Melting point | > 250 °C (482 °F; 523 K) 260 °C |
| Boiling point | > 350 °C (662 °F; 623 K) (decomposes) |
| Practically insoluble | |
| log P | 0.94540 |
| Thermal conductivity | 0.15 to 0.24 W/(m·K) |
Refractive index (nD) |
1.57–1.58, 1.5750 |
| Thermochemistry | |
Heat capacity (C) |
1.0 kJ/(kg·K) |
| Related compounds | |
Related Monomers |
Terephthalic acid Ethylene glycol |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references | |
Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods, and thermoforming for manufacturing, and in combination with glass fibre for engineering resins.
In 2022, the global PET (fiber and resins) capacity stood at 81 million tons with PET fiber accounting for over 65% of the total PET market while PET resins accounts for the remaining share. PET resins are widely used in the production of plastic bottles and packaging materials. The beverage and packaging industries heavily rely on PET resins due to their transparency, lightweight nature, and the ease with which they can be molded into various shapes. PET fibers on the other hand, are spun into threads and woven into fabrics for clothing, carpets, and a variety of other textile products.
PET consists of repeating (C10H8O4) units. PET is commonly recycled, and has the digit 1 (♳) as its resin identification code (RIC). The National Association for PET Container Resources (NAPCOR) defines PET as: "Polyethylene terephthalate items referenced are derived from terephthalic acid (or dimethyl terephthalate) and mono ethylene glycol, wherein the sum of terephthalic acid (or dimethyl terephthalate) and mono ethylene glycol reacted constitutes at least 90 percent of the mass of monomer reacted to form the polymer, and must exhibit a melting peak temperature between 225 °C and 255 °C, as identified during the second thermal scan in procedure 10.1 in ASTM D3418, when heating the sample at a rate of 10 °C/minute."
Depending on its processing and thermal history, polyethylene terephthalate may exist both as an amorphous (transparent) and as a semi-crystalline polymer. The semicrystalline material might appear transparent (particle size less than 500 nm) or opaque and white (particle size up to a few micrometers) depending on its crystal structure and particle size.
One process for making PET uses bis(2-hydroxyethyl) terephthalate, which can be synthesized by the esterification reaction between terephthalic acid and ethylene glycol with water as a byproduct (this is also known as a condensation reaction), or by transesterification reaction between ethylene glycol and dimethyl terephthalate (DMT) with methanol as a byproduct. Polymerization is through a polycondensation reaction of the monomers (done immediately after esterification/transesterification) with water as the byproduct.
| Young's modulus, E | 2800–3100 MPa |
| Tensile strength, σt | 55–75 MPa |
| Elastic limit | 50–150% |
| Notch test | 3.6 kJ/m2 |
| Glass transition temperature, Tg | 67–81 °C |
| Vicat B | 82 °C |
| Linear expansion coefficient, α | 7×10−5 K−1 |
| Water absorption (ASTM) | 0.16 |
| Source | |
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