Poly(ethylene terephthalate)

Molecule of National Chemistry Week!
October 17, 2022
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Poly(ethylene terephthalate), known familiarly as PET, is a condensation copolymer of ethylene glycol1 and terephthalic acid2. It is often incorrectly expressed as polyethylene terephthalate, without the parentheses.

As shown in the chemical equation, PET is made industrially by the reaction of equimolar amounts of terephthalic acid and ethylene glycol at 220–260 °C and 0.3–0.6 MPa pressure. Another commercial process begins with dimethyl terephthalate3 instead of the free acid and proceeds under similar conditions. Annual worldwide production exceeds 30 million tonnes.

Although most of us are familiar with so-called “PET bottles” for water and soft drinks, bottles consume only ≈30% of PET production. About 60% of PET is spun into fibers that are used in fabrics for fashion apparel, thermal wear, sportswear, workwear, and upholstery. In the fiber and fabric industries, PET is commonly called “polyester”.

In 2021, Peter Dubruel, Sandra Van Vliergerghe, and colleagues at Ghent University (Belgium) published an excellent review of the chemistry and applications of poly(ethylene terephthalate) and other commercial poly(alkylene terephthalate)s.

PET, or polyester, is currently being celebrated as a “fabulous fiber” during National Chemistry Week!

1. CAS Reg. No. 107-21-1.
2. CAS Reg. No. 100-21-0.
3. CAS Reg. No. 120-61-6.

Poly(ethylene terephthalate) hazard information

Hazard class* GHS code and hazard statement
Not a hazardous substance or mixture  

*Globally Harmonized System of Classification and Labeling of Chemicals. Explanation of pictograms.

MOTW update

Ketene1 was the Molecule of the Week for June 27, 2016. It is a colorless, toxic gas that is useful in organic synthesis. This month, Guangjin Hou, Xiulian Pan, Xinhe Bao, and co-workers at the Chinese Academy of Sciences (Dalian) described the chemistry of converting ketene to gasoline-range hydrocarbons by passing it over H-SAPO-11 molecular sieves2 at temperatures up to 400 °C.

1. CAS Reg. No. 463-51-4.
2. H-SAPO-11 is an acidified medium-pore silicoaluminophosphate molecular sieve, CAS Reg. No. 308075-33-4.

Poly(ethylene terephthalate)
fast facts

CAS Reg. No. 25038-59-9
SciFinder nomenclature Poly(oxy-1,2-ethanediyloxycarbonyl-1,4-phenylenecarbonyl)
Empirical formula (C10H8O4)n
Molar mass Variable; 10–50 kg/mol
Appearance Transparent amorphous or semicrystalline solid
Melting point Variable; generally 250–260 °C
Water solubility Insoluble
Chemical Abstract Service - a division of ACS

Learn more about this molecule from CAS, the most authoritative and comprehensive source for chemical information.

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