Polyester is a synthetic polymer made of purified terephthalic acid or its dimethyl ester dimethyl terephthalate and monoethylene glycol. With 18% market share of all plastic materials produced, it ranges third after polyethylene (33.5%) and polypropylene (19.5%).

The main raw materials are described as follows: Purified terephthalic acid (PTA) CAS-No.: 100-21-0, Synonym: 1,4 benzenedicarboxylic acid. Sum formula: C₆H₄(COOH)₂, mol. weight: 166.13,Dimethylterephthalate (DMT) CAS-No.: 120-61-6.

Synonym: 1,4 benzenedicarboxylic acid dimethyl ester, Sum formula: C₆H₄(COOCH₃)₂, mol. weight: 194.19.

Mono-ethylene glycol (MEG) CAS No.: 107-21-1, Synonym: 1,2 ethanediol,Sum formula: C₂H₆O₂ , mol. weight: 62.07.

To make a polymer of high molecular weight a catalyst is needed. The most common catalyst is antimony trioxide :Antimony trioxide (ATO) CAS-No.: 1309-64-4, mol. weight: 291.51, Sum formula: Sb₂O₃

In 2008, about 10,000 tonnes Sb₂O₃ were used to produce around 49 million tonnes polyethylene terephthalate.

Polyester is described as follows: Polyethylene terephthalate CAS-No.: 25038-59-9, Synonyms/abbreviations: polyester, PET, PES, 
Sum formula: H-[C₁₀H₈O₄]-n=60–120 OH, mol. unit weight: 192.17.