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For the 1981 motion picture, see Polyester (film).
Close-up of a polyester shirt
Stretching polyester fabric

Polyester is a category of polymers that contain the ester functional group in their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include naturally occurring chemicals, such as in the cutin of plant cuticles, as well as synthetics through step-growth polymerization such as polybutyrate. Natural polyesters and a few synthetic ones are biodegradable, but most synthetic polyesters are not. This material is used very widely in clothing.

Depending on the chemical structure, polyester can be a thermoplastic or thermoset. There are also polyester resins cured by hardeners; however, the most common polyesters are thermoplastics.[1]


Polyester fibers are sometimes spun together with natural fibers to produce a cloth with blended properties. Cotton-polyester blends (polycotton) can be strong, wrinkle and tear-resistant, and reduce shrinking. Synthetic fibers in polyester also create materials with water, wind and environmental resistance compared to plant-derived fibers. Cons of cotton and polyester blends include being less breathable than cotton and trapping more moisture while sticking to the skin. They are also less fire resistant and can melt when ignited.[3]

Polyester blends have been renamed so as to suggest their similarity or even superiority to natural fibers (for example, China silk, which is a term in the textiles industry for a 100% polyester fiber woven to resemble the sheen and durability of insect-derived silk).

Polyesters are also used to make bottles, films, tarpaulin, canoes, liquid crystal displays, holograms, filters, dielectric film for capacitors, film insulation for wire and insulating tapes. Polyesters are widely used as a finish on high-quality wood products such as guitars, pianos and vehicle/yacht interiors. Thixotropic properties of spray-applicable polyesters make them ideal for use on open-grain timbers, as they can quickly fill wood grain, with a high-build film thickness per coat. Cured polyesters can be sanded and polished to a high-gloss, durable finish.




Unsaturated polyesters (UPR) are thermosetting resins. They are used in the liquid state as casting materials, in sheet molding compounds, as fiberglass laminating resins and in non-metallic auto-body fillers. They are also used as the thermoset polymer matrix in pre-pregs. Fiberglass-reinforced unsaturated polyesters find wide application in bodies of yachts and as body parts of cars.

According to the composition of their main chain, polyesters can be:

Main chain
Type Examples of
Polyesters Manufacturing methods
Aliphatic Homopolymer Polyglycolide or polyglycolic acid (PGA) Polycondensation of glycolic acid
Polylactic acid (PLA) Ring-opening polymerization of lactide
Polycaprolactone (PCL) Ring-opening polymerization of caprolactone
Polyhydroxyalkanoate (PHA)
Polyhydroxybutyrate (PHB)
Copolymer Polyethylene adipate (PEA)
Polybutylene succinate (PBS) Polycondensation of succinic acid with 1,4-butanediol
Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) Copolymerization of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid,
butyrolactone, and valerolactone (oligomeric aluminoxane as a catalyst)
Semi-aromatic Copolymer Polyethylene terephthalate (PET) Polycondensation of terephthalic acid with ethylene glycol
Polybutylene terephthalate (PBT) Polycondensation of terephthalic acid with 1,4-butanediol
Polytrimethylene terephthalate (PTT) Polycondensation of terephthalic acid with 1,3-propanediol
Polyethylene naphthalate (PEN) Polycondensation of at least one naphthalene dicarboxylic acid with ethylene glycol
Aromatic Copolymer Vectran Polycondensation of 4-hydroxybenzoic acid and 6-hydroxynaphthalene-2-carboxylic acid

Increasing the aromatic parts of polyesters increases their glass transition temperature, melting temperature, thermal stability, chemical stability...

Polyesters can also be telechelic oligomers like the polycaprolactone diol (PCL) and the polyethylene adipate diol (PEA). They are then used as prepolymers.



Polyester is a synthetic polymer made of purified terephthalic acid (PTA) or its dimethyl ester dimethyl terephthalate (DMT) and monoethylene glycol (MEG). With 18% market share of all plastic materials produced, it ranges third after polyethylene (33.5%)[citation needed] 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 (or antimony tri-acetate):

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.[citation needed]

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

There are several reasons for the importance of polyester:

  • The relatively easy accessible raw materials PTA or DMT and MEG
  • The low toxicity level of all raw materials and side products during polyester production and processing
  • The outstanding mechanical and chemical properties of polyester
  • The recyclability
  • The wide variety of intermediate and final products made of polyester.

In the following table, the estimated world polyester production is shown. Main applications are textile polyester, bottle polyester resin, film polyester mainly for packaging and specialty polyesters for engineering plastics. According to this table, the world's total polyester production might exceed 50 million tons per annum before the year 2010.

World polyester production by year
Product type 2002 (million tonnes/year) 2008 (million tonnes/year)
Textile-PET 20 39
Resin, bottle/A-PET 9 16
Film-PET 1.2 1.5
Special polyester 1 2.5
Total 31.2 59

Raw material producer[edit]

Polyester processing[edit]

After the first stage of polymer production in the melt phase, the product stream divides into two different application areas which are mainly textile applications and packaging applications. In the following table, the main applications of textile and packaging of polyester are listed.

Textile and packaging polyester application list (melt or pellet)
Textile Packaging
Staple fiber (PSF) Bottles for CSD, water, beer, juice, detergents, etc.
Filaments POY, DTY, FDY A-PET film
Technical yarn and tire cord Thermoforming
Non-woven and spunbond biaxial-oriented film (BO-PET)
Mono-filament Strapping


Polyester-staple fiber;
Partially oriented yarn;
Draw-textured yarn;
Fully drawn yarn;
Carbonated soft drink;
Amorphous polyester film;
Biaxial-oriented polyester film;

A comparable small market segment (much less than 1 million tonnes/year) of polyester is used to produce engineering plastics and masterbatch.

In order to produce the polyester melt with a high efficiency, high-output processing steps like staple fiber (50–300 tonnes/day per spinning line) or POY /FDY (up to 600 tonnes/day split into about 10 spinning machines) are meanwhile more and more vertically integrated direct processes. This means the polymer melt is directly converted into the textile fibers or filaments without the common step of pelletizing. We are talking about full vertical integration when polyester is produced at one site starting from crude oil or distillation products in the chain oil → benzene → PX → PTA → PET melt → fiber/filament or bottle-grade resin. Such integrated processes are meanwhile established in more or less interrupted processes at one production site. Eastman Chemicals were the first to introduce the idea of closing the chain from PX to PET resin with their so-called INTEGREX process. The capacity of such vertically integrated production sites is >1000 tonnes/day and can easily reach 2500 tonnes/day.





Azeotrope esterification[edit]


Alcoholic transesterification[edit]

Main article: Transesterification
Transesterification: An alcohol-terminated oligomer and an ester-terminated oligomer condense to form an ester linkage, with loss of an alcohol. R and R' are the two oligomer chains, R'' is a sacrificial unit such as a methyl group (methanol is the byproduct of the esterification reaction).

Acylation (HCl method)[edit]


Silyl method
In this variant of the HCl method, the carboxylic acid chloride is converted with the trimethyl silyl ether of the alcohol component and production of trimethyl silyl chloride is obtained

Acetate method (esterification)[edit]

Silyl acetate method

Ring-opening polymerization[edit]

Aliphatic polyesters can be assembled from lactones under very mild conditions, catalyzed anionically, cationically or metallorganically. A number of catalytic methods for the copolymerization of epoxides with cyclic anhydrides have also recently been shown to provide a wide array of functionalized polyesters, both saturated and unsaturated.


Main article: Biodegradation

The futuro house was made of fibreglass-reinforced polyester plastic; polyester-polyurethane, and poly(methylmethacrylate) one of them was found to be degrading by Cyanobacteria and Archaea.[4][5]


Unsaturated polyesters are thermosetting resins. They are generally copolymers prepared by polymerizing one or more diol with saturated and unsaturated dicarboxylic acids (maleic acid, fumaric acid...) or their anhydrides. The double bond of unsaturated polyesters reacts with a vinyl monomer, usually styrene, resulting in a 3-D cross-linked structure. This structure acts as a thermoset. The exothermic cross-linking reaction is initiated through a catalyst, usually an organic peroxide such as methyl ethyl ketone peroxide or benzoyl peroxide.

Environmental concerns[edit]

Pollution of freshwater and seawater habitats[edit]

A team at Plymouth University in the UK spent 12 months analysing what happened when a number of synthetic materials were washed at different temperatures in domestic washing machines, using different combinations of detergents, to quantify the microfibres shed. They found that an average washing load of 6 kg could release an estimated 137,951 fibres from polyester-cotton blend fabric, 496,030 fibres from polyester and 728,789 from acrylic. Those fibers add to the general microplastics pollution.[6][7][8]

See also[edit]


  1. ^ Rosato, Dominick V.; Rosato, Donald V.; Rosato, Matthew V. (2004). Plastic product material and process selection handbook. Elsevier. p. 85. ISBN 978-1-85617-431-2. 
  2. ^ Schuler, Mattias J. (1981). "Part 8: Dyeing with disperse dyes". Dyeing Primer. AATCC. p. 21. GGKEY:SK3T00EYAFR. 
  3. ^ Mendelson, Cheryl (17 May 2005). Home Comforts: The Art and Science of Keeping House. Simon and Schuster. ISBN 9780743272865. 
  4. ^ Cappitelli F; Principi P; Sorlini C. (Aug 2006). "Biodeterioration of modern materials in contemporary collections: can biotechnology help?". Trends in biotechnology. 24 (8): 350–4. doi:10.1016/j.tibtech.2006.06.001. PMID 16782219. 
  5. ^ Rinaldi, Andrea (7 November 2006). "Saving a fragile legacy. Biotechnology and microbiology are increasingly used to preserve and restore the worlds cultural heritage". EMBO Reports. 7 (11): 1075–1079. doi:10.1038/sj.embor.7400844. PMC 1679785Freely accessible. PMID 17077862. 
  6. ^ O'Connor, Mary Catherine (27 October 2014) Inside the lonely fight against the biggest environmental problem you've never heard of. The Guardian
  7. ^ Williams, Alan. "Washing clothes releases thousands of microplastic particles into environment, study shows". Plymouth University. Retrieved 9 October 2016. 
  8. ^ Napper, I. E.; Thompson, R. C. (2016). "Release of Synthetic Microplastic Plastic Fibres From Domestic Washing Machines: Effects of Fabric Type and Washing Conditions". Marine Pollution Bulletin. 112 (1–2): 39–45. doi:10.1016/j.marpolbul.2016.09.025. PMID 27686821. 

Further reading[edit]


External links[edit]