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== Classification == | == Classification == | ||
Polyols may be classified according to their chemistry.<ref>{{cite journal|doi = 10.1007/BF02699621|title = Polyurethanes, polyurethane dispersions and polyureas: Past, present and future|journal = Surface Coatings International Part B: Coatings Transactions|volume = 86|issue = 2|pages = 111–118|year = 2003|last1 = Howarth|first1 = GA| s2cid=93574741 }}</ref> Some of these chemistries are polyether, polyester,<ref>{{ | Polyols may be classified according to their chemistry.<ref>{{cite journal|doi = 10.1007/BF02699621|title = Polyurethanes, polyurethane dispersions and polyureas: Past, present and future|journal = Surface Coatings International Part B: Coatings Transactions|volume = 86|issue = 2|pages = 111–118|year = 2003|last1 = Howarth|first1 = GA| s2cid=93574741 }}</ref> Some of these chemistries are polyether, polyester,<ref>{{cite book |last1=Avar |first1=G. |last2=Meier-Westhues |first2=U. |last3=Casselmann |first3=H. |last4=Achten |first4=D. |title=Polymer Science: A Comprehensive Reference |chapter=Polyurethanes |date=2012 |pages=411–441 |doi=10.1016/B978-0-444-53349-4.00275-2 |isbn=978-0-08-087862-1 }}</ref> polycarbonate<ref>{{cite journal |last1=Scharfenberg |first1=Markus |last2=Hofmann |first2=Silja |last3=Preis |first3=Jasmin |last4=Hilf |first4=Jeannette |last5=Frey |first5=Holger |title=Rigid Hyperbranched Polycarbonate Polyols from CO 2 and Cyclohexene-Based Epoxides |journal=Macromolecules |date=22 August 2017 |volume=50 |issue=16 |pages=6088–6097 |doi=10.1021/acs.macromol.7b01276 |bibcode=2017MaMol..50.6088S }}</ref><ref>{{Cite patent|number=WO2011129940A1|title=Polycarbonate polyols and polyurethanes made therefrom|gdate=2011-10-20|invent1=Montgomery|invent2=Brown|invent3=Sonnenschein|invent4=Foley|inventor1-first=Steven|inventor2-first=Shawn|inventor3-first=Mark|inventor4-first=Paul|url=https://patents.google.com/patent/WO2011129940A1/en}}</ref> and also acrylic polyols.<ref>{{Cite web|last=Roesler|first=Richard|date=26 March 1986|title=Acrylic polyols having low residual monomer content European Patent|url=https://patentimages.storage.googleapis.com/78/38/fb/cd9c639d25a624/EP0197460A2.pdf|website=European Patent}}</ref><ref>{{Cite web|title=Polyacrylate Polyols|url=https://ebrary.net/14329/environment/polyacrylate_polyols|access-date=2022-02-13|website=Ebrary}}</ref> Polyether polyols may be further subdivided and classified as [[polyethylene oxide]] or [[polyethylene glycol]] (PEG), [[polypropylene glycol]] (PPG) and [[polytetrahydrofuran]] or PTMEG. These have 2, 3 and 4 carbon atoms respectively per oxygen atom in the repeat unit. Polycaprolactone polyols are also commercially available.<ref>{{Cite web|title=Polycaprolactone Polyols Market Report - Size and Share by 2026 {{!}} AMR|url=https://www.alliedmarketresearch.com/polycaprolactone-polyols-market|access-date=2022-02-12|website=Allied Market Research|language=en}}</ref> There is also an increasing trend to use biobased (and hence renewable) polyols.<ref>{{cite journal |last1=Li |first1=Yonghui |last2=Sun |first2=Xiuzhi Susan |title=Synthesis and characterization of acrylic polyols and polymers from soybean oils for pressure-sensitive adhesives |journal=RSC Advances |date=2015 |volume=5 |issue=55 |pages=44009–44017 |doi=10.1039/C5RA04399A |bibcode=2015RSCAd...544009L }}</ref><ref>{{Cite journal|vauthors=Patel JV, Desai SD, Sinha, VK |title= Bio-acrylic polyols for two pack polyurethane coating|url=https://www.researchgate.net/publication/268398112|pages=259–264 |access-date=2022-02-13|journal=Journal of Scientific and Industrial Research|volume=63|issue=3|date=March 2004|language=en}}</ref><ref>{{Cite journal|last1=Kasprzyk|first1=Paulina|last2=Sadowska|first2=Ewelina|last3=Datta|first3=Janusz|date=2019-11-01|title=Investigation of Thermoplastic Polyurethanes Synthesized via Two Different Prepolymers|journal=Journal of Polymers and the Environment|language=en|volume=27|issue=11|pages=2588–2599|doi=10.1007/s10924-019-01543-7|s2cid=201704473 |issn=1572-8919|doi-access=free|bibcode=2019JPEnv..27.2588K }}</ref><ref>{{cite journal |last1=Gurunathan |first1=T. |last2=Mohanty |first2=Smita |last3=Nayak |first3=Sanjay K. |title=Isocyanate terminated castor oil-based polyurethane prepolymer: Synthesis and characterization |journal=Progress in Organic Coatings |date=March 2015 |volume=80 |pages=39–48 |doi=10.1016/j.porgcoat.2014.11.017 }}</ref> | ||
==Uses== | ==Uses== | ||
Polyether polyols have numerous uses.<ref>{{Cite journal|last1=Datta|first1=Janusz|last2=Kosiorek|first2=Paulina|last3=Włoch|first3=Marcin|date=2017-04-01|title=Synthesis, structure and properties of poly(ether-urethane)s synthesized using a tri-functional oxypropylated glycerol as a polyol|journal=Journal of Thermal Analysis and Calorimetry|language=en|volume=128|issue=1|pages=155–167|doi=10.1007/s10973-016-5928-2|s2cid=100046328 |issn=1588-2926|doi-access=free}}</ref><ref>{{ | Polyether polyols have numerous uses.<ref>{{Cite journal|last1=Datta|first1=Janusz|last2=Kosiorek|first2=Paulina|last3=Włoch|first3=Marcin|date=2017-04-01|title=Synthesis, structure and properties of poly(ether-urethane)s synthesized using a tri-functional oxypropylated glycerol as a polyol|journal=Journal of Thermal Analysis and Calorimetry|language=en|volume=128|issue=1|pages=155–167|doi=10.1007/s10973-016-5928-2|s2cid=100046328 |issn=1588-2926|doi-access=free}}</ref><ref>{{cite journal |last1=kantheti |first1=Sasidhar |last2=Sarath |first2=P.S. |last3=Narayan |first3=Ramanuj |last4=Raju |first4=K.V.S.N. |title=Synthesis and characterization of triazole rich polyether polyols using click chemistry for highly branched polyurethanes |journal=Reactive and Functional Polymers |date=December 2013 |volume=73 |issue=12 |pages=1597–1605 |doi=10.1016/j.reactfunctpolym.2013.09.002 |bibcode=2013RFPol..73.1597K }}</ref> As an example, [[polyurethane foam]] is a big user of polyether polyols.<ref>{{cite book |last1=Abraham |first1=T.W. |last2=Höfer |first2=R. |editor-last1=Matyjaszewski |editor-first1=K |editor-last2=Möller |editor-first2=M |year=2012 |chapter= 10.03 - Lipid-Based Polymer Building Blocks and Polymers |title=Polymer Science: A Comprehensive Reference |publisher=Elsevier |pages= 15–58 |doi=10.1016/B978-0-444-53349-4.00253-3 |isbn=9780080878621 }}</ref> | ||
Polyester polyols can be used to produce rigid foam.<ref>{{Cite journal |last1=McAdams |first1=Carina |last2=Farmer |first2=Steven |date=September 2003 |title=Stabilization of Rigid Systems Containing Aromatic Polyester Polyol and Water |journal=Journal of Cellular Plastics |volume=39 |issue=September 2003 |pages=369–386 |doi=10.1177/0021955X03035067 |s2cid=96795892 }}</ref><ref>{{Cite web|date=February 2022|title=Polyester polyols for rigid foam|url=https://www.stepan.com/content/dam/stepan-dot-com/webdam/website-product-documents/literature/polyester-polyols/StepanRigidFoamBrochure.pdf|website=Stepan}}</ref> They are available in both [[Aromatic_compound|aromatic]] and [[Aliphatic_compound|aliphatic]] versions.<ref>{{Cite web|title=Aromatic Polyester Polyols|url=https://purinova.com/en/products/polyester-polyols/aromatic-polyester-polyols|access-date=2022-02-12|website=purinova.com|language=en}}</ref><ref>{{Cite web|date=May 2018|title=Polyester Polyols|url=https://www.nord-composites.com/fichiersusers/files/NORD-COMPOSITES_BrochuresPolyesterPolyols_May_2018.pdf|website=Nord}}</ref> They are also available in mixed aliphatic-aromatic versions often made from recycled raw materials, typically [[polyethylene terephthalate]] (PET).<ref>{{Cite journal|last=Makuska|first=Ricardas|date=2008| number= 2 |title=Glycolysis of industrial poly(ethylene terephthalate) waste directed to bis(hydroxyethylene) terephthalate and aromatic polyester polyols|journal=Chemija|volume=19|pages=29–34 |url=https://mokslozurnalai.lmaleidykla.lt/publ/0235-7216/2008/2/29-34.pdf }}</ref> | Polyester polyols can be used to produce rigid foam.<ref>{{Cite journal |last1=McAdams |first1=Carina |last2=Farmer |first2=Steven |date=September 2003 |title=Stabilization of Rigid Systems Containing Aromatic Polyester Polyol and Water |journal=Journal of Cellular Plastics |volume=39 |issue=September 2003 |pages=369–386 |doi=10.1177/0021955X03035067 |s2cid=96795892 }}</ref><ref>{{Cite web|date=February 2022|title=Polyester polyols for rigid foam|url=https://www.stepan.com/content/dam/stepan-dot-com/webdam/website-product-documents/literature/polyester-polyols/StepanRigidFoamBrochure.pdf|website=Stepan}}</ref> They are available in both [[Aromatic_compound|aromatic]] and [[Aliphatic_compound|aliphatic]] versions.<ref>{{Cite web|title=Aromatic Polyester Polyols|url=https://purinova.com/en/products/polyester-polyols/aromatic-polyester-polyols|access-date=2022-02-12|website=purinova.com|language=en}}</ref><ref>{{Cite web|date=May 2018|title=Polyester Polyols|url=https://www.nord-composites.com/fichiersusers/files/NORD-COMPOSITES_BrochuresPolyesterPolyols_May_2018.pdf|website=Nord}}</ref> They are also available in mixed aliphatic-aromatic versions often made from recycled raw materials, typically [[polyethylene terephthalate]] (PET).<ref>{{Cite journal|last=Makuska|first=Ricardas|date=2008| number= 2 |title=Glycolysis of industrial poly(ethylene terephthalate) waste directed to bis(hydroxyethylene) terephthalate and aromatic polyester polyols|journal=Chemija|volume=19|pages=29–34 |url=https://mokslozurnalai.lmaleidykla.lt/publ/0235-7216/2008/2/29-34.pdf }}</ref> | ||
Acrylic polyols are generally used in higher performance applications where stability to [[ultraviolet]] light is required<ref>{{Cite patent|number=US6762262B1|title=Preparation of acrylic polyols|gdate=2004-07-13|invent1=Wang|invent2=Harris|inventor1-first=Wei|inventor2-first=Stephen H.|url=https://patents.google.com/patent/US6762262B1/en}}</ref> and also lower [[Volatile organic compound|VOC]] coatings.<ref>{{Cite book|last=Ionescu|first=Mihail|chapter=10. Acrylic polyols|title=Aromatic Polyester Polyols: Chemistry and Technology|volume=1|publisher=De Gruyter|year=2019|pages=267–272 |isbn=978-3-11-064410-4|language=en|doi=10.1515/9783110644104-010|s2cid=241043906 }}</ref><ref>{{Cite web|title=New Acrylic Polyols for Low-VOC Coatings|url=https://www.pcimag.com/articles/84259-new-acrylic-polyols-for-low-voc-coatings|access-date=2022-02-13|date=2002-05-31|website=www.pcimag.com|language=en}}</ref> Other uses include direct to metal coatings.<ref>{{Cite web|title=Acrylic polyol with enhanced performance for 2K PUR direct-to-metal coatings |url=https://insights.basf.com/home/article/read/acrylic-polyol-with-enhanced-performance-for-2k-pur-direct-to-metal-coatings|access-date=2022-02-13|publisher=BASF}}</ref> As they are used where good UV resistance is required, such as automotive coatings, the [[isocyanate]] component also tends to be UV resistant and hence isocyanate oligomers or [[prepolymer]]s based on [[Isophorone diisocyanate]] are generally used.<ref>{{ | Acrylic polyols are generally used in higher performance applications where stability to [[ultraviolet]] light is required<ref>{{Cite patent|number=US6762262B1|title=Preparation of acrylic polyols|gdate=2004-07-13|invent1=Wang|invent2=Harris|inventor1-first=Wei|inventor2-first=Stephen H.|url=https://patents.google.com/patent/US6762262B1/en}}</ref> and also lower [[Volatile organic compound|VOC]] coatings.<ref>{{Cite book|last=Ionescu|first=Mihail|chapter=10. Acrylic polyols|title=Aromatic Polyester Polyols: Chemistry and Technology|volume=1|publisher=De Gruyter|year=2019|pages=267–272 |isbn=978-3-11-064410-4|language=en|doi=10.1515/9783110644104-010|s2cid=241043906 }}</ref><ref>{{Cite web|title=New Acrylic Polyols for Low-VOC Coatings|url=https://www.pcimag.com/articles/84259-new-acrylic-polyols-for-low-voc-coatings|access-date=2022-02-13|date=2002-05-31|website=www.pcimag.com|language=en}}</ref> Other uses include direct to metal coatings.<ref>{{Cite web|title=Acrylic polyol with enhanced performance for 2K PUR direct-to-metal coatings |url=https://insights.basf.com/home/article/read/acrylic-polyol-with-enhanced-performance-for-2k-pur-direct-to-metal-coatings|access-date=2022-02-13|publisher=BASF}}</ref> As they are used where good UV resistance is required, such as automotive coatings, the [[isocyanate]] component also tends to be UV resistant and hence isocyanate oligomers or [[prepolymer]]s based on [[Isophorone diisocyanate]] are generally used.<ref>{{cite journal |last1=Gite |first1=V.V. |last2=Mahulikar |first2=P.P. |last3=Hundiwale |first3=D.G. |title=Preparation and properties of polyurethane coatings based on acrylic polyols and trimer of isophorone diisocyanate |journal=Progress in Organic Coatings |date=August 2010 |volume=68 |issue=4 |pages=307–312 |doi=10.1016/j.porgcoat.2010.03.008 }}</ref> | ||
Caprolactone-based polyols produce polyurethanes with enhanced hydrolysis resistance.<ref>{{Cite web|last=Takaaki|first=Fujiwa|date=19 July 1990|title=A polycaprolactone polyol and hydrolysis resistant polyurethane resins prepared therefrom patent 0 409 735 A1|url=https://patentimages.storage.googleapis.com/8b/3e/79/e4bdbb854918b7/EP0409735A1.pdf|website=European Patent Office}}</ref><ref>{{ | Caprolactone-based polyols produce polyurethanes with enhanced hydrolysis resistance.<ref>{{Cite web|last=Takaaki|first=Fujiwa|date=19 July 1990|title=A polycaprolactone polyol and hydrolysis resistant polyurethane resins prepared therefrom patent 0 409 735 A1|url=https://patentimages.storage.googleapis.com/8b/3e/79/e4bdbb854918b7/EP0409735A1.pdf|website=European Patent Office}}</ref><ref>{{cite journal |last1=Huang |first1=Shan |last2=Xiao |first2=Juan |last3=Zhu |first3=Yan’an |last4=Qu |first4=Jinqing |title=Synthesis and properties of spray-applied high solid content two component polyurethane coatings based on polycaprolactone polyols |journal=Progress in Organic Coatings |date=May 2017 |volume=106 |pages=60–68 |doi=10.1016/j.porgcoat.2017.02.011 }}</ref> | ||
Polycarbonate polyols are more expensive than other polyols and are thus used in more demanding applications.<ref>{{ | Polycarbonate polyols are more expensive than other polyols and are thus used in more demanding applications.<ref>{{cite journal |last1=Pohl |first1=M. |last2=Danieli |first2=E. |last3=Leven |first3=M. |last4=Leitner |first4=W. |last5=Blümich |first5=B. |last6=Müller |first6=T. E. |title=Dynamics of Polyether Polyols and Polyether Carbonate Polyols |journal=Macromolecules |date=13 December 2016 |volume=49 |issue=23 |pages=8995–9003 |doi=10.1021/acs.macromol.6b01601 |bibcode=2016MaMol..49.8995P }}</ref><ref>{{Cite web|title=Polycarbonate Diols for Ultimate Performance Polyurethanes|url=https://www.gantrade.com/blog/ultimate-performance-polyurethanes-based-on-polycarbonate-diols|access-date=2022-02-14|website=www.gantrade.com|language=en-us}}</ref> They have been used to make an [[isophorone diisocyanate]] based prepolymer which is then used in glass coatings.<ref>{{Cite journal|last=Wilson|first=Michael G.|date=November 1991|title=New coatings for glass|journal=Journal of the Oil and Colour Chemists Association|volume=11|pages=412–415|via=Springer}}</ref> They may be used in reactive hotmelt [[adhesive]]s.<ref>{{Cite web|title=Carbon Dioxide-Based Polycarbonate Polyols for Polyurethane Systems|url=https://www.adhesivesmag.com/articles/93368-carbon-dioxide-based-polycarbonate-polyols-for-polyurethane-systems|access-date=2022-02-14|website=www.adhesivesmag.com|language=en|first=Anna |last=Cherian|date=2014-11-01}}</ref> | ||
All polyols may be used to produce polyurethane [[prepolymer]]s.<ref>{{Cite journal|last1=Harani|first1=H.|last2=Fellahi|first2=S.|last3=Bakar|first3=M.|date=1998|title=Toughening of epoxy resin using synthesized polyurethane prepolymer based on hydroxyl-terminated polyesters|journal=Journal of Applied Polymer Science|language=en|volume=70|issue=13|pages=2603–2618|doi=10.1002/(SICI)1097-4628(19981226)70:13<2603::AID-APP6>3.0.CO;2-4|issn=1097-4628|doi-access=free}}</ref><ref>{{ | All polyols may be used to produce polyurethane [[prepolymer]]s.<ref>{{Cite journal|last1=Harani|first1=H.|last2=Fellahi|first2=S.|last3=Bakar|first3=M.|date=1998|title=Toughening of epoxy resin using synthesized polyurethane prepolymer based on hydroxyl-terminated polyesters|journal=Journal of Applied Polymer Science|language=en|volume=70|issue=13|pages=2603–2618|doi=10.1002/(SICI)1097-4628(19981226)70:13<2603::AID-APP6>3.0.CO;2-4|issn=1097-4628|doi-access=free}}</ref><ref>{{cite journal |last1=Shi |first1=Minxian |last2=Zheng |first2=Juanli |last3=Huang |first3=Zhixiong |last4=Qin |first4=Yan |title=Synthesis of Polyurethane Prepolymers and Damping Property of Polyurethane/Epoxy Composites |journal=Advanced Science Letters |date=March 2011 |volume=4 |issue=3 |pages=740–744 |doi=10.1166/asl.2011.1597 }}</ref><ref>{{cite journal |last1=Pokharel |first1=Pashupati |last2=Lee |first2=Dai Soo |title=High performance polyurethane nanocomposite films prepared from a masterbatch of graphene oxide in polyether polyol |journal=Chemical Engineering Journal |date=October 2014 |volume=253 |pages=356–365 |doi=10.1016/j.cej.2014.05.046 |bibcode=2014ChEnJ.253..356P }}</ref> These then find use in [[coatings]],<ref name="howarth">{{cite journal|first=G.A.|last=Howarth |year=2000 |title=Legislation-compliant polyurethane and epoxy coatings |journal=Pigment & Resin Technology|volume=29 |issue=6|pages=325–336|doi=10.1108/03699420010355120}}</ref> [[adhesives]], [[sealants]] and [[elastomers]].<ref>{{cite journal |last1=Wang |first1=Lei |last2=Shen |first2=Yiding |last3=Lai |first3=Xiaojuan |last4=Li |first4=Zhongjin |last5=Liu |first5=Min |title=Synthesis and properties of crosslinked waterborne polyurethane |journal=Journal of Polymer Research |date=May 2011 |volume=18 |issue=3 |pages=469–476 |doi=10.1007/s10965-010-9438-9 }}</ref> | ||
===Low molecular weight polyols=== | ===Low molecular weight polyols=== | ||
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Low molecular weight polyols are widely used in [[polymer chemistry]] where they function as crosslinking agents and chain extenders. [[Alkyd resin]]s for example, use polyols in their synthesis and are used in [[paint]]s and in molds for [[casting]]. They are the dominant [[resin]] or "binder" in most commercial "oil-based" coatings. Approximately 200,000 tons of alkyd resins are produced each year. They are based on linking reactive monomers through ester formation. Polyols used in the production of commercial alkyd resins are [[glycerol]], [[trimethylolpropane]], and [[pentaerythritol]].<ref name =ullmann>{{Ullmann | author = Frank N. Jones | title = Alkyd Resins | doi = 10.1002/14356007.a01_409}}</ref> In polyurethane prepolymer production, a low molecular weight polyol-[[diol]] such as [[1,4-butanediol]] may be used as a chain extender to further increase molecular weight though it does increase [[viscosity]] because more [[hydrogen bonding]] is introduced.<ref name="howarth"/> | Low molecular weight polyols are widely used in [[polymer chemistry]] where they function as crosslinking agents and chain extenders. [[Alkyd resin]]s for example, use polyols in their synthesis and are used in [[paint]]s and in molds for [[casting]]. They are the dominant [[resin]] or "binder" in most commercial "oil-based" coatings. Approximately 200,000 tons of alkyd resins are produced each year. They are based on linking reactive monomers through ester formation. Polyols used in the production of commercial alkyd resins are [[glycerol]], [[trimethylolpropane]], and [[pentaerythritol]].<ref name =ullmann>{{Ullmann | author = Frank N. Jones | title = Alkyd Resins | doi = 10.1002/14356007.a01_409}}</ref> In polyurethane prepolymer production, a low molecular weight polyol-[[diol]] such as [[1,4-butanediol]] may be used as a chain extender to further increase molecular weight though it does increase [[viscosity]] because more [[hydrogen bonding]] is introduced.<ref name="howarth"/> | ||
{| class="wikitable floatright | {| class="wikitable floatright skin-invert-image" | ||
|- class="hintergrundfarbe6" | |- class="hintergrundfarbe6" | ||
|'''Low molecular weight polyols''' | |'''Low molecular weight polyols''' | ||
|- | |- | ||
| [[File:Pentaerythritol.svg |130px]] | | [[File:Pentaerythritol.svg |130px]] | ||
[[Pentaerythritol]] | |||
|- | |- | ||
| [[File:Xylitol Structural Formula V.1.svg |180px]] | | [[File:Xylitol Structural Formula V.1.svg |180px]] | ||
[[Xylitol]] | [[Xylitol]] | ||
|} | |} | ||
===Sugar alcohols=== | ===Sugar alcohols=== | ||
[[Sugar alcohol]]s, a class of low molecular weight polyols, are commonly obtained by [[hydrogenation]] of sugars.<ref name="malani">{{ | [[Sugar alcohol]]s, a class of low molecular weight polyols, are commonly obtained by [[hydrogenation]] of sugars.<ref name="malani">{{cite journal |last1=Malani |first1=Ritesh S. |last2=Malshe |first2=Vinod C. |last3=Thorat |first3=Bhaskar Narayan |title=Polyols and polyurethanes from renewable sources: past, present, and future—part 2: plant-derived materials |journal=Journal of Coatings Technology and Research |date=March 2022 |volume=19 |issue=2 |pages=361–375 |doi=10.1007/s11998-021-00534-5 }}</ref>{{rp|363}} They have the formula (CHOH)<sub>n</sub>H<sub>2</sub>, where n = 4–6.<ref>{{cite encyclopedia|vauthors=Schiweck H, Bär A, Vogel R, Schwarz E, Kunz M, Dusautois C, Clement A, Lefranc C, Lüssem B, Moser M, Peters S|display-authors=3|chapter=Sugar Alcohols|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry|year=2012|publisher=Wiley-VCH|place=Weinheim|doi=10.1002/14356007.a25_413.pub3|isbn=978-3527306732}}</ref> | ||
Sugar alcohols are added to foods because of their lower caloric content than [[sugar]]s; however, they are also, in general, less sweet, and are often combined with high-intensity [[Sugar substitute|sweeteners]]. They are also added to [[chewing gum]] because they are not broken down by bacteria in the mouth or [[metabolized]] to acids, and thus do not contribute to [[tooth decay]]. [[Maltitol]], [[sorbitol]], [[xylitol]], [[erythritol]], and [[isomalt]] are common sugar alcohols. | Sugar alcohols are added to foods because of their lower caloric content than [[sugar]]s; however, they are also, in general, less sweet, and are often combined with high-intensity [[Sugar substitute|sweeteners]]. They are also added to [[chewing gum]] because they are not broken down by bacteria in the mouth or [[metabolized]] to acids, and thus do not contribute to [[tooth decay]]. [[Maltitol]], [[sorbitol]], [[xylitol]], [[erythritol]], and [[isomalt]] are common sugar alcohols. | ||
Sugar alcohols, such as [[inositol|myoinositol]], [[pinitol]], and [[mannitol]], have roles in maintaining cellular water balance and responding to drought or low temperature stress.<ref name="Vovener de Verlands et al 2025">{{cite journal |last1=Vovener de Verlands |first1=Edmond |last2=Hong |first2=Zonglie |last3=Nelson |first3=Andrew S. |title=Sugar alcohols in plants: implications for enhancing tree seedlings drought tolerance and production strategies |journal=BMC Plant Biology |date=2025 |volume=28 |page=891 |doi=10.1186/s12870-025-06860-9|pmid=40634904|pmc= 12239448|doi-access=free}}</ref> | |||
===Polymeric polyols=== | ===Polymeric polyols=== | ||
{| class="wikitable floatright" style=" | {| class="wikitable floatright" style="width:300px; color:black; background-color:white;" | ||
|- class="hintergrundfarbe6" | |- class="hintergrundfarbe6" | ||
|'''Polymeric polyols''' | |'''Polymeric polyols''' | ||
|- | |- | ||
| [[File:Polyether Polyol Structural Formula V3.svg |270px]] | | [[File:Polyether Polyol Structural Formula V3.svg |270px]] | ||
[[Polyether polyol]] | [[Polyether polyol]]. The oxygen atoms of the [[ether]] linkages are shown in blue. | ||
are shown in blue. | |||
|- | |- | ||
| [[File:Polyester Polyol Structural Formula V.3.svg |300px]] | | [[File:Polyester Polyol Structural Formula V.3.svg |300px]] | ||
[[Polyester polyol]]. The oxygen and carbon atoms of the [[ester group]]s are shown in blue. | |||
of the [[ester group]]s are shown in blue. | |||
|} | |} | ||
The term ''polyol'' is used for various chemistries of the molecular backbone. Polyols may be reacted with [[diisocyanate]]s or polyisocyanates to produce [[polyurethane]]s. [[Methylene diphenyl diisocyanate|MDI]] finds considerable use in PU foam production.<ref>{{Citation|title=4,4′-Methylene diphenyl isocyanate (MDI) and polymeric MDI″ (PMDI) [MAK Value Documentation, 1997]|date=2012 | The term ''polyol'' is used for various chemistries of the molecular backbone. Polyols may be reacted with [[diisocyanate]]s or polyisocyanates to produce [[polyurethane]]s. [[Methylene diphenyl diisocyanate|MDI]] finds considerable use in PU foam production.<ref>{{Citation|title=4,4′-Methylene diphenyl isocyanate (MDI) and polymeric MDI″ (PMDI) [MAK Value Documentation, 1997]|date=2012|work=The MAK-Collection for Occupational Health and Safety|pages=66–96|publisher=John Wiley & Sons, Ltd|language=en|doi=10.1002/3527600418.mb10168stae0008|isbn=978-3-527-60041-0|doi-access=free}}</ref> Polyurethanes are used to make flexible foam for [[mattresses]] and seating, rigid foam insulation for [[refrigerator]]s and [[freezers]], [[elastomeric]] shoe soles, fibers (e.g. [[Spandex]]), coatings, sealants and [[adhesives]].<ref>{{cite web | last = Boustead | first = I. | work = Eco-Profiles of the European Plastics Industry | title = Polyurethane rigid foam | year = 2005 | publisher = PlasticsEurope | location = Brussels | url = http://www.isopa.org/isopa/uploads/Documents/documents/rigid%20foam%20LCI.pdf | url-status = dead | archiveurl = https://web.archive.org/web/20130925082609/http://www.isopa.org/isopa/uploads/Documents/documents/rigid%20foam%20LCI.pdf | archivedate = 2013-09-25 }}</ref> | ||
The term ''polyol'' is also attributed to other molecules containing hydroxyl groups. For instance, [[polyvinyl alcohol]] is (CH<sub>2</sub>CHOH)<sub>''n''</sub> with ''n'' hydroxyl groups where ''n'' can be in the thousands. [[Cellulose]] is a polymer with many hydroxyl groups, but it is not referred to as a polyol. | The term ''polyol'' is also attributed to other molecules containing hydroxyl groups. For instance, [[polyvinyl alcohol]] is (CH<sub>2</sub>CHOH)<sub>''n''</sub> with ''n'' hydroxyl groups where ''n'' can be in the thousands. [[Cellulose]] is a polymer with many hydroxyl groups, but it is not referred to as a polyol. | ||
===Polyols from recycled or renewable sources=== | ===Polyols from recycled or renewable sources=== | ||
There are polyols based on renewable sources such as [[Bioplastic|plant-based]] materials including [[castor oil]] and [[cottonseed oil]].<ref>{{ | There are polyols based on renewable sources such as [[Bioplastic|plant-based]] materials including [[neem oil]], [[castor oil]], and [[cottonseed oil]].<ref>Ashok B. Chaudhari, Pyus D. Tatiya, Rahul K. Hedaoo, Ravindra D. Kulkarni, Vikas V. Gite, Polyurethane Prepared from Neem Oil Polyesteramides for Self-Healing Anticorrosive Coatings, Industrial & Engineering Chemistry Research, 2013, 52, 30, 10189–10197</ref><ref>{{cite journal |last1=Nelson |first1=Thomas J. |last2=Masaki |first2=Bryan |last3=Morseth |first3=Zachary |last4=Webster |first4=Dean C. |title=Highly functional biobased polyols and their use in melamine–formaldehyde coatings |journal=Journal of Coatings Technology and Research |date=November 2013 |volume=10 |issue=6 |pages=757–767 |doi=10.1007/s11998-013-9524-0 }}</ref><ref>{{cite journal |last1=Jia |first1=Lian Kun |last2=Gong |first2=Li Xiang |last3=Ji |first3=Wen Jiao |last4=Kan |first4=Cheng You |title=Synthesis of vegetable oil based polyol with cottonseed oil and sorbitol derived from natural source |journal=Chinese Chemical Letters |date=November 2011 |volume=22 |issue=11 |pages=1289–1292 |doi=10.1016/j.cclet.2011.05.043 }}</ref><ref>{{cite journal |last1=Narute |first1=Prashant |last2=Palanisamy |first2=Aruna |title=Study of the performance of polyurethane coatings derived from cottonseed oil polyol |journal=Journal of Coatings Technology and Research |date=January 2016 |volume=13 |issue=1 |pages=171–179 |doi=10.1007/s11998-015-9741-9 }}</ref> Vegetable oils and biomass are also potential renewable polyol raw materials.<ref>{{cite journal |last1=Malani |first1=Ritesh S. |last2=Malshe |first2=Vinod C. |last3=Thorat |first3=Bhaskar Narayan |title=Polyols and polyurethanes from renewable sources: past, present and future—part 1: vegetable oils and lignocellulosic biomass |journal=Journal of Coatings Technology and Research |date=January 2022 |volume=19 |issue=1 |pages=201–222 |doi=10.1007/s11998-021-00490-0 }}</ref> Seed oil can even be used to produce polyester polyols.<ref>{{cite journal |last1=Argyropoulos |first1=John |last2=Popa |first2=Paul |last3=Spilman |first3=Gary |last4=Bhattacharjee |first4=Debkumar |last5=Koonce |first5=William |title=Seed oil based polyester polyols for coatings |journal=Journal of Coatings Technology and Research |date=December 2009 |volume=6 |issue=4 |pages=501–508 |doi=10.1007/s11998-008-9154-0 }}</ref> | ||
==Properties== | ==Properties== | ||
Latest revision as of 10:07, 22 December 2025
In organic chemistry, a polyol is an organic compound containing multiple hydroxyl groups (Template:Chem2). The term "polyol" can have slightly different meanings depending on whether it is used in food science or polymer chemistry. Polyols containing two, three and four hydroxyl groups are diols,[1] triols,[2] and tetrols,[3][4] respectively.
Classification
Polyols may be classified according to their chemistry.[5] Some of these chemistries are polyether, polyester,[6] polycarbonate[7][8] and also acrylic polyols.[9][10] Polyether polyols may be further subdivided and classified as polyethylene oxide or polyethylene glycol (PEG), polypropylene glycol (PPG) and polytetrahydrofuran or PTMEG. These have 2, 3 and 4 carbon atoms respectively per oxygen atom in the repeat unit. Polycaprolactone polyols are also commercially available.[11] There is also an increasing trend to use biobased (and hence renewable) polyols.[12][13][14][15]
Uses
Polyether polyols have numerous uses.[16][17] As an example, polyurethane foam is a big user of polyether polyols.[18]
Polyester polyols can be used to produce rigid foam.[19][20] They are available in both aromatic and aliphatic versions.[21][22] They are also available in mixed aliphatic-aromatic versions often made from recycled raw materials, typically polyethylene terephthalate (PET).[23]
Acrylic polyols are generally used in higher performance applications where stability to ultraviolet light is required[24] and also lower VOC coatings.[25][26] Other uses include direct to metal coatings.[27] As they are used where good UV resistance is required, such as automotive coatings, the isocyanate component also tends to be UV resistant and hence isocyanate oligomers or prepolymers based on Isophorone diisocyanate are generally used.[28]
Caprolactone-based polyols produce polyurethanes with enhanced hydrolysis resistance.[29][30]
Polycarbonate polyols are more expensive than other polyols and are thus used in more demanding applications.[31][32] They have been used to make an isophorone diisocyanate based prepolymer which is then used in glass coatings.[33] They may be used in reactive hotmelt adhesives.[34]
All polyols may be used to produce polyurethane prepolymers.[35][36][37] These then find use in coatings,[38] adhesives, sealants and elastomers.[39]
Low molecular weight polyols
Low molecular weight polyols are widely used in polymer chemistry where they function as crosslinking agents and chain extenders. Alkyd resins for example, use polyols in their synthesis and are used in paints and in molds for casting. They are the dominant resin or "binder" in most commercial "oil-based" coatings. Approximately 200,000 tons of alkyd resins are produced each year. They are based on linking reactive monomers through ester formation. Polyols used in the production of commercial alkyd resins are glycerol, trimethylolpropane, and pentaerythritol.[40] In polyurethane prepolymer production, a low molecular weight polyol-diol such as 1,4-butanediol may be used as a chain extender to further increase molecular weight though it does increase viscosity because more hydrogen bonding is introduced.[38]
| Low molecular weight polyols |
| File:Pentaerythritol.svg |
| File:Xylitol Structural Formula V.1.svg |
Sugar alcohols
Sugar alcohols, a class of low molecular weight polyols, are commonly obtained by hydrogenation of sugars.[41]Template:Rp They have the formula (CHOH)nH2, where n = 4–6.[42]
Sugar alcohols are added to foods because of their lower caloric content than sugars; however, they are also, in general, less sweet, and are often combined with high-intensity sweeteners. They are also added to chewing gum because they are not broken down by bacteria in the mouth or metabolized to acids, and thus do not contribute to tooth decay. Maltitol, sorbitol, xylitol, erythritol, and isomalt are common sugar alcohols.
Sugar alcohols, such as myoinositol, pinitol, and mannitol, have roles in maintaining cellular water balance and responding to drought or low temperature stress.[43]
Polymeric polyols
| Polymeric polyols |
| File:Polyether Polyol Structural Formula V3.svg
Polyether polyol. The oxygen atoms of the ether linkages are shown in blue. |
| File:Polyester Polyol Structural Formula V.3.svg
Polyester polyol. The oxygen and carbon atoms of the ester groups are shown in blue. |
The term polyol is used for various chemistries of the molecular backbone. Polyols may be reacted with diisocyanates or polyisocyanates to produce polyurethanes. MDI finds considerable use in PU foam production.[44] Polyurethanes are used to make flexible foam for mattresses and seating, rigid foam insulation for refrigerators and freezers, elastomeric shoe soles, fibers (e.g. Spandex), coatings, sealants and adhesives.[45]
The term polyol is also attributed to other molecules containing hydroxyl groups. For instance, polyvinyl alcohol is (CH2CHOH)n with n hydroxyl groups where n can be in the thousands. Cellulose is a polymer with many hydroxyl groups, but it is not referred to as a polyol.
Polyols from recycled or renewable sources
There are polyols based on renewable sources such as plant-based materials including neem oil, castor oil, and cottonseed oil.[46][47][48][49] Vegetable oils and biomass are also potential renewable polyol raw materials.[50] Seed oil can even be used to produce polyester polyols.[51]
Properties
Since the generic term polyol is only derived from chemical nomenclature and just indicates the presence of several hydroxyl groups, no common properties can be assigned to all polyols. However, polyols are usually viscous at room temperature due to hydrogen bonding.
See also
References
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- ↑ Ashok B. Chaudhari, Pyus D. Tatiya, Rahul K. Hedaoo, Ravindra D. Kulkarni, Vikas V. Gite, Polyurethane Prepared from Neem Oil Polyesteramides for Self-Healing Anticorrosive Coatings, Industrial & Engineering Chemistry Research, 2013, 52, 30, 10189–10197
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