Difference between revisions of "Polyester" - New World Encyclopedia

Latest revision as of 17:38, 9 October 2021

This image, taken with a scanning electron microscope, shows a bend in a high surface area polyester fiber with a seven-lobed cross section.

A bottle made of PET

Polyester is the name for a class of polymers that contain the ester functional group in their main chain. Although some types of polyesters can be found in nature, such as the cutin of plant cuticles, the term polyester is usually applied to the artificially synthesized materials. Among the synthetic types of polyester, one of the most important is known as polyethylene terephthalate (PET); another is polycarbonate.

PET fibers are the most widely used manufactured fibers in the United States. Fabrics made from PET fibers are used for apparel and home furnishings. In addition, polyesters are used to make bottles, films, liquid crystal displays, filters, and electrical insulation. Some polyesters are thermosetting resins that are widely used in the bodies of automobiles and yachts.

Properties and uses

Thermoplastic polyesters, such as PET, may be heated and processed into different forms, including fibers, sheets, and three-dimensional shapes. Although combustible at high temperatures, polyester tends to shrink away from flames and often self-extinguishes. Woven PET fabrics are used for bed sheets, bedspreads, curtains, and draperies. Polyester fiberfill is also used to stuff pillows, comforters, and cushion padding.

Polyester fabrics sometimes have a "less natural" feel when compared to similarly woven fabrics made from natural fibers, such as cotton. However, polyester fabrics may exhibit other advantages over natural fabrics, particularly improved wrinkle resistance. For this reason, polyester fibers are often spun together with natural fibers, like cotton, to produce cloth with blended properties.

Close-up of a polyester shirt.

Polyesters are also used to make bottles, films, tarpaulin, liquid crystal displays, holograms, filters, dielectric film for capacitors, film insulation for wire, and insulating tapes.

Liquid crystalline polyesters are among the first such polymers to be used industrially. In general, they have extremely good mechanical properties and are very resistant to heat. They can therefore be used for seals in jet engines.

Thermosetting polyester resins are generally copolymers of unsaturated polyesters with styrene.^[1] The unsaturation in the polyester is generally obtained by the use of maleic acid or fumaric acid, each of which has a carbon-carbon double bond in its molecular structure. Another important family is the group of vinyl esters. Here the unsaturation is found in the alcohol part of the polyester. The double bond of the unsaturated polyester reacts with styrene resulting in a 3-D crosslinked structure, the thermoset material. Unsaturated polyesters are commonly used as casting materials, fiberglass laminating resins, and non-metallic auto-body fillers. Fiberglass reinforced unsaturated polyesters find wide application in the bodies of yachts and automobiles.

Polyester is also widely used as a finish on high-quality wooden products like guitars, pianos and vehicle/yacht interiors.^[2] The thixotropic properties of the sprayable form of polyester make it ideal for use on open-grain timbers, as it can quickly fill the grain and has a high build film thickness per coat. The cured polyester can then be sanded and polished to a high-gloss, durable finish.

Synthesis

Synthesis of polyesters is generally achieved by what are called polycondensation reactions.^[3] Some examples of these reactions are given below.

Azeotrope esterification

The repeating unit of polyethylene terephthalate (PET).

In this classical method, an alcohol and a carboxylic acid react to form a carboxylic ester, with the release of water molecules. For example, to synthesize PET, ethylene glycol (an alcohol with two OH groups) and terephthalic acid (an acid with two carboxyl groups) may be used as the starting materials.

To assemble the polymer, the water formed by the reaction must be continually removed, by a process known as azeotrope distillation.

Alcoholic transesterification

In transesterification, the alkoxy group of an ester compound is exchanged for another alcohol. For example, PET can be synthesized by reacting ethylene glycol with dimethyl terephthalate (the dimethyl ester of terephthalic acid).

Shown below is the reaction between an ester-terminated oligomer (with the alkoxy group -OCH₃) and an alcohol-terminated oligomer (with the OH group), producing a larger oligomer and methanol (CH₃OH).

O \\ C - OCH₃ + OH[Oligomer2] / [Oligomer1]	$\leftrightarrow$	O \\ C - O[Oligomer2] + CH₃OH / [Oligomer1]
(ester-terminated oligomer + alcohol-terminated oligomer)		(larger oligomer + methanol)

Acylation (HCl method)

This method involves the use of the acid chloride (R-COCl) form of the acid. Thus the polycondensation proceeds with emission of hydrochloric acid (HCl) instead of water. This method can be carried out in solution or as an enamel.

Recycling PET bottles

Although all thermoplastics are technically recyclable, PET bottle recycling is more practical than many other plastic applications. The primary reason is that plastic carbonated soft drink bottles and water bottles are almost exclusively PET, which makes them more easily identifiable in a recycle stream. PET has a resin identification code of one. Like many other plastics, PET is also an excellent candidate for thermal recycling (incineration), as it is composed of carbon, hydrogen and oxygen with only trace amounts of catalyst elements (no sulfur), and it has the energy content of soft coal.

Notes

↑ In organic chemistry, an "unsaturated" molecule is one that contains double or triple covalent bonds between carbon atoms.
↑ Burns Guitars, Rolls Royce, and Sunseeker are examples of companies that use polyester on their products.
↑ In a "condensation reaction," two molecules (or functional groups) combine to form a single molecule, accompanied by the loss of a small molecule, such as water.

References
ISBN links support NWE through referral fees

Albertsson, Ann-Christine. Degradable Aliphatic Polyesters. Advances in Polymer Science, 157. Berlin: Springer, 2002. ISBN 3540422498
Goodman, Isaac, and Brian Parkyn. Polyesters. London: Published for the Plastics Institute by Iliffe Books, 1965. OCLC 2033281
Kadolph, Sara J. Textiles. Upper Saddle River, NJ: Pearson Prentice Hall, 2007. ISBN 9780131187696
Scheirs, John, and Timothy E. Long (eds.). Modern Polyesters: Chemistry and Technology of Polyesters and Copolyesters. Wiley Series in Polymer Science. Hoboken, NJ: John Wiley & Sons, 2003. ISBN 0471498564

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[1] In organic chemistry, an "unsaturated" molecule is one that contains double or triple covalent bonds between carbon atoms.

[2] Burns Guitars, Rolls Royce, and Sunseeker are examples of companies that use polyester on their products.

[3] In a "condensation reaction," two molecules (or functional groups) combine to form a single molecule, accompanied by the loss of a small molecule, such as water.

[1]

[2]

[3]

@@ Line 1: / Line 1: @@
-:''For the 1981 cinema film, see the article ''[[Polyester (film)]]''.
+{{Copyedited}}{{Images OK}}{{Submitted}}{{Approved}}{{Paid}}
+[[Image:SEMexample.jpg|thumb|400px|This image, taken with a [[scanning electron microscope]], shows a bend in a high surface area polyester [[fiber]] with a seven-lobed cross section.]]
+[[File:Botella de plástico - PET.jpg|thumb|300px|A bottle made of PET]]
-[[Image:SEMexample.jpg|thumb|[[Scanning electron microscope|SEM]] picture of a bend in a high surface area polyester [[fiber]] with a seven-lobed cross section]]
+'''Polyester''' is the name for a class of [[polymer]]s that contain the [[ester]] [[functional group]] in their main chain. Although some types of polyesters can be found in [[nature]], such as the [[cutin]] of [[plant cuticle]]s, the term ''polyester'' is usually applied to the artificially synthesized materials. Among the synthetic types of polyester, one of the most important is known as [[polyethylene terephthalate]] (PET); another is [[polycarbonate]].
-'''Polyester''' (aka Terylene) is a category of [[polymer]]s which contain the [[ester]] [[functional group]] in their main chain.  Although there are many forms of polyesters, the term "polyester" is most commonly used to refer to [[polyethylene terephthalate]] (PET). Other forms of polyester include naturally occurring [[cutin]] of [[plant cuticle]]s as well as [[synthetic]] polyesters such as [[polycarbonate]].
-Polyester may be produced in numerous forms.  For example, polyester as a [[thermoplastic]] may be heated and processed into different forms, e.g., fibers, sheets, and three-dimensional shapes.  While combustible at high temperatures, polyester tends to shrink away from flames and often self-extinguishes.
+PET fibers are the most widely used manufactured fibers in the [[United State]]s. [[Fabric]]s made from PET fibers are used for apparel and home furnishings. In addition, polyesters are used to make [[bottle]]s, [[film]]s, [[liquid crystal display]]s, [[filter (chemistry)|filter]]s, and [[electrical insulation]]. Some polyesters are thermosetting resins that are widely used in the bodies of automobiles and yachts.
-==Applications==
+== Properties and uses ==
+[[Thermoplastic]] polyesters, such as PET, may be heated and processed into different forms, including fibers, sheets, and three-dimensional shapes. Although combustible at high [[temperature]]s, polyester tends to shrink away from flames and often self-extinguishes. Woven PET fabrics are used for bed sheets, bedspreads, curtains, and draperies. Polyester fiberfill is also used to stuff pillows, comforters, and cushion padding.
-Polyester is the most widely used manufactured fiber in the United States.  Woven polyester fabrics are used for apparel and home furnishings.  These include bed sheets, bedspreads, curtains and draperies.  Polyester fiberfill is also used to stuff pillows, comforters and cushion padding.
+Polyester fabrics sometimes have a "less natural" feel when compared to similarly woven fabrics made from natural fibers, such as [[cotton]]. However, polyester fabrics may exhibit other advantages over natural fabrics, particularly improved wrinkle resistance. For this reason, polyester fibers are often spun together with natural fibers, like cotton, to produce cloth with blended properties.
-Polyester fabrics sometimes have a "less natural" feel when compared to similarly woven fabrics made from natural fibers, e.g., cotton.  However, polyester fabrics may exhibit other advantages over natural fabrics, e.g., improved wrinkle resistance.  As a result, polyester fibers are often spun together with natural fibers, e.g., [[cotton]], to produce a cloth with blended properties.
+[[Image:Polyester Shirt, close-up.jpg|thumb|350px|Close-up of a polyester shirt.]]
-[[Image:Polyester Shirt, close-up.jpg|thumb|Close-up of a polyester shirt]]
-Polyesters are also used to make bottles, films, [[tarpaulin]], [[liquid crystal display]]s, [[hologram]]s, [[filter (chemistry)|filter]]s, [[dielectric]] film for [[capacitor]]s, [[Electrical insulation|film insulation]] for [[wire]] and insulating tapes.
+Polyesters are also used to make [[bottle]]s, [[film]]s, [[tarpaulin]], [[liquid crystal display]]s, [[hologram]]s, [[filter (chemistry)|filter]]s, [[dielectric]] film for [[capacitor]]s, [[Electrical insulation|film insulation]] for [[wire]], and insulating tapes.
-Liquid crystalline polyesters are among the first industrially used liquid crystalline polymers. In general they have extremely good mechanical properties and are extremely heat resistant. For that reason, they can be used as an abradable seal in jet engines.
+Liquid crystalline polyesters are among the first such polymers to be used industrially. In general, they have extremely good mechanical properties and are very resistant to [[heat]]. They can therefore be used for seals in jet engines.
-[[Thermoset]]ting polyester [[resin]]s are generally copolymers of unsaturated polyesters with styrene. The unsaturation in the polyester is generally governed by maleic acid or fumaric acid.  Another important family is the group of vinyl esters. Here the unsaturation is found in the alcohol part of the polyester. The double bond of the unsaturated polyester reacts with styrene  resulting in a 3-D crosslinked structure, the thermoset material. The [[cross-link]]ing is initiated through an [[exothermic]] reaction involving an [[organic peroxide]], such as [[methyl ethyl ketone peroxide]] or [[benzoyl peroxide]]. Unsaturated polyesters are commonly used as [[casting]] materials, [[fiberglass]] laminating resins, and non-metallic auto-body fillers. Fiberglass reinforced unsaturated polyesters find wide application in bodies of yachts and as body parts of cars.
+[[Thermoset]]ting polyester [[resin]]s are generally copolymers of unsaturated polyesters with styrene.<ref>In organic chemistry, an "unsaturated" molecule is one that contains double or triple covalent bonds between carbon atoms.</ref> The unsaturation in the polyester is generally obtained by the use of maleic acid or fumaric acid, each of which has a carbon-carbon double bond in its molecular structure. Another important family is the group of vinyl esters. Here the unsaturation is found in the alcohol part of the polyester. The double bond of the unsaturated polyester reacts with styrene resulting in a 3-D crosslinked structure, the thermoset material. Unsaturated polyesters are commonly used as [[casting]] materials, [[fiberglass]] laminating resins, and non-metallic auto-body fillers. Fiberglass reinforced unsaturated polyesters find wide application in the bodies of yachts and automobiles.
-Polyester is also widely used as a finish on high-quality wooden products like [[guitar]]s, [[piano]]s and vehicle/yacht interiors ([[Burns London|Burns Guitars]], [[Rolls-Royce car|Rolls Royce]] and [[Sunseeker]] are examples of companies that use polyester on their products). The [[thixotropic]] properties of the sprayable form of polyester make it ideal for use on open grain timbers as it can quickly fill the grain and has a high build film thickness per coat. The cured polyester can then be sanded and polished to a high-gloss, durable finish.
+Polyester is also widely used as a finish on high-quality wooden products like [[guitar]]s, [[piano]]s and vehicle/yacht interiors.<ref>[[Burns London|Burns Guitars]], [[Rolls-Royce car|Rolls Royce]], and [[Sunseeker]] are examples of companies that use polyester on their products.</ref> The [[thixotropic]] properties of the sprayable form of polyester make it ideal for use on open-grain timbers, as it can quickly fill the grain and has a high build film thickness per coat. The cured polyester can then be sanded and polished to a high-gloss, durable finish.
 ==Synthesis==
-Synthesis of polyesters is generally achieved by a polycondensation reaction. See "[[condensation reaction]]s in polymer chemistry".
+Synthesis of polyesters is generally achieved by what are called polycondensation reactions.<ref>In a "condensation reaction," two [[molecule]]s (or [[functional group]]s) combine to form a single molecule, accompanied by the loss of a small molecule, such as [[water]].</ref> Some examples of these reactions are given below.
 ===Azeotrope esterification===
-In this classical method, an [[alcohol]] and a [[carboxylic acid]] react to form a carboxylic ester.
+[[Image:PET.png|thumb|right|400px|The repeating unit of polyethylene terephthalate (PET).]]
-To assemble a polymer, the water formed by the reaction must be continually removed by [[azeotrope]] distillation.
+In this classical method, an [[alcohol]] and a [[carboxylic acid]] react to form a carboxylic ester, with the release of [[water]] [[molecule]]s. For example, to synthesize PET, ethylene glycol (an alcohol with two OH groups) and terephthalic acid (an acid with two carboxyl groups) may be used as the starting materials.
+To assemble the polymer, the water formed by the reaction must be continually removed, by a process known as [[azeotrope]] distillation.
 ===Alcoholic transesterification===
-''See main article on [[transesterification]].''
+In ''transesterification'', the [[alkoxy group]] of an [[ester compound]] is exchanged for another [[alcohol]]. For example, PET can be synthesized by reacting ethylene glycol with dimethyl terephthalate (the dimethyl ester of terephthalic acid).
+Shown below is the reaction between an ester-terminated oligomer (with the alkoxy group -OCH<sub>3</sub>) and an alcohol-terminated oligomer (with the OH group), producing a larger oligomer and methanol (CH<sub>3</sub>OH).
 {|
 |- style="vertical-align:center;"
 |
-          O
+  O
-          \\
+  \\
-            C - O<font color="#ff0000">CH<sub>3</sub></font>  +  <font color="#00c000">OH</font>[Oligomer2]
+  C - O<font color="#ff0000">CH<sub>3</sub></font> + <font color="#00c000">OH</font>[Oligomer2]
-          /
+  /
   [Oligomer1]
 | <math>\leftrightarrow</math>
 |
-          O
+  O
-          \\
+  \\
-            C - O[Oligomer2]  + <font color="#ff0000">CH<sub>3</sub></font><font color="#00c000">OH</font>
+  C - O[Oligomer2] + <font color="#ff0000">CH<sub>3</sub></font><font color="#00c000">OH</font>
-          /
+  /
   [Oligomer1]
 |- style="text-align:center;"
-| (ester-terminated oligomer  +  alcohol-terminated oligomer)
+| (ester-terminated oligomer + alcohol-terminated oligomer)
 | &nbsp;
-| (larger oligomer  +  methanol)
+| (larger oligomer + methanol)
 |}
 ===Acylation (HCl method)===
-The acid begins as an acid chloride, and thus the polycondensation proceeds with emission of [[hydrochloric acid]] (HCl) instead of water.  This method can be carried out in solution or as an [[vitreous enamel|enamel]].
+This method involves the use of the acid chloride (R-COCl) form of the acid. Thus the polycondensation proceeds with emission of [[hydrochloric acid]] (HCl) instead of water. This method can be carried out in solution or as an [[vitreous enamel|enamel]].
-:'''Silyl method'''
-:In this variant of the HCl method, the carboxylic acid chloride is converted with the trimethyl silyl ether of the alcohol component; trimethyl silyl chloride is produced.
-===Acetate method (esterification)===
+== Recycling PET bottles ==
-:'''Silyl acetate method '''
+[[Image:Resin-identification-code-1-PETE.svg|left|100px|1-PETE]]
-===Ring-opening Polymerization===
+Although all thermoplastics are technically recyclable, PET bottle [[recycling]] is more practical than many other plastic applications. The primary reason is that plastic carbonated soft drink bottles and [[Bottled water|water bottles]] are almost exclusively PET, which makes them more easily identifiable in a recycle stream. PET has a [[resin identification code]] of one. Like many other plastics, PET is also an excellent candidate for thermal recycling (incineration), as it is composed of [[carbon]], [[hydrogen]] and [[oxygen]] with only trace amounts of [[catalyst]] elements (no [[sulfur]]), and it has the energy content of soft coal.
-[[Aliphatic]] polyesters can be assembled from [[lactone]]s under very mild conditions, catalyzed [[anionic]]ally, [[cationic]]ally or [[metallorganic]]ally.
+== See also ==
+* [[Alcohol]]
+* [[Carboxylic acid]]
+* [[Ester]]
+* [[Plastic]]
+* [[Polymer]]
+== Notes ==
+<references/>
 ==References==
-*''Textiles'', by Sara Kadolph and Anna Langford. 8th Edition, 1998.
+* Albertsson, Ann-Christine. ''Degradable Aliphatic Polyesters''. Advances in Polymer Science, 157. Berlin: Springer, 2002. ISBN 3540422498
+* Goodman, Isaac, and Brian Parkyn. ''Polyesters''. London: Published for the Plastics Institute by Iliffe Books, 1965. {{OCLC|2033281}}
+* Kadolph, Sara J. ''Textiles''. Upper Saddle River, NJ: Pearson Prentice Hall, 2007. ISBN 9780131187696
+* Scheirs, John, and Timothy E. Long (eds.). ''Modern Polyesters: Chemistry and Technology of Polyesters and Copolyesters''. Wiley Series in Polymer Science. Hoboken, NJ: John Wiley & Sons, 2003. ISBN 0471498564
 {{Plastics}}
 {{fibers}}
-[[Category:Carboxylate esters]]
-[[Category:Plastics]]
-[[Category:Polyesters| ]]
-[[Category:Synthetic resins]]
-[[Category:Synthetic fibers]]
-[[Category:Dielectrics]]
-[[cs:Polyester]]
+[[Category:Physical sciences]]
-[[de:Polyester]]
+[[Category:Chemistry]]
-[[es:Poliéster]]
+[[Category:Polymers]]
-[[eo:Poliestero]]
+[[Category:Textile technology]]
-[[fr:Polyester]]
-[[it:Poliesteri]]
+{{credits|Polyester|158786201|Polyethylene_terephthalate|159273154}}
-[[he:פוליאסטר]]
-[[nl:Polyester]]
-[[ja:ポリエステル]]
-[[pl:Poliestry]]
-[[pt:Poliéster]]
-[[ru:Полиэфиры]]
-[[sq:Poliesteri]]
-[[fi:Polyesteri]]
-[[sv:Polyester]]
-[[tr:Polyester]]