polyol

Polyols may be classified according to their chemistry.{{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 }} Some of these chemistries are polyether, polyester,{{Cite web|title=Polyester Polyols - an overview |url=https://www.sciencedirect.com/topics/engineering/polyester-polyols|access-date=2022-02-12|website=www.sciencedirect.com}} polycarbonate{{Cite journal|last1=Scharfenberg|first1=Markus|last2=Hofmann|first2=Silja|last3=Preis|first3=Jasmin|last4=Hilf|first4=Jeannette|last5=Frey|first5=Holger|date=2017-08-22|title=Rigid Hyperbranched Polycarbonate Polyols from CO2 and Cyclohexene-Based Epoxides|url=https://doi.org/10.1021/acs.macromol.7b01276|journal=Macromolecules|volume=50|issue=16|pages=6088–6097|doi=10.1021/acs.macromol.7b01276|bibcode=2017MaMol..50.6088S |issn=0024-9297|url-access=subscription}}{{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}} and also acrylic polyols.{{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}}{{Cite web|title=Polyacrylate Polyols|url=https://ebrary.net/14329/environment/polyacrylate_polyols|access-date=2022-02-13|website=Ebrary}} 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 carbons respectively per oxygen atom in the repeat unit. Polycaprolactone polyols are also commercially available.{{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}} There is also an increasing trend to use biobased (and hence renewable) polyols.{{Cite journal|last1=Li|first1=Yonghui|last2=Sun|first2=Xiuzhi Susan|date=2015-05-15|title=Synthesis and characterization of acrylic polyols and polymers from soybean oils for pressure-sensitive adhesives|url=https://pubs.rsc.org/en/content/articlelanding/2015/ra/c5ra04399a|journal=RSC Advances|language=en|volume=5|issue=55|pages=44009–44017|doi=10.1039/C5RA04399A|bibcode=2015RSCAd...544009L |issn=2046-2069|url-access=subscription}}{{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}}{{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 }}{{Cite journal|last1=Gurunathan|first1=T.|last2=Mohanty|first2=Smita|last3=Nayak|first3=Sanjay K.|date=2015-03-01|title=Isocyanate terminated castor oil-based polyurethane prepolymer: Synthesis and characterization|url=https://www.sciencedirect.com/science/article/pii/S0300944014003725|journal=Progress in Organic Coatings|language=en|volume=80|pages=39–48|doi=10.1016/j.porgcoat.2014.11.017|issn=0300-9440|url-access=subscription}}

Polyether polyols have numerous uses.{{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}}{{Cite journal|last1=Kantheti|first1=Sasidhar|last2=Sarath|first2=P. S.|last3=Narayan|first3=Ramanuj|last4=Raju|first4=K. V. S. N.|date=2013-12-01|title=Synthesis and characterization of triazole rich polyether polyols using click chemistry for highly branched polyurethanes|url=https://www.sciencedirect.com/science/article/pii/S138151481300206X|journal=Reactive and Functional Polymers|language=en|volume=73|issue=12|pages=1597–1605|doi=10.1016/j.reactfunctpolym.2013.09.002|bibcode=2013RFPol..73.1597K |issn=1381-5148|url-access=subscription}} As an example, polyurethane foam is a big user of polyether polyols.{{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 }}

Polyester polyols can be used to produce rigid foam.{{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 }}{{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}} They are available in both aromatic and aliphatic versions.{{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}}{{Cite web|date=May 2018|title=Polyester Polyols|url=https://www.nord-composites.com/fichiersusers/files/NORD-COMPOSITES_BrochuresPolyesterPolyols_May_2018.pdf|website=Nord}} They are also available in mixed aliphatic-aromatic versions often made from recycled raw materials, typically polyethylene terephthalate (PET).{{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 }}

Acrylic polyols are generally used in higher performance applications where stability to ultraviolet light is required{{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}} and also lower VOC coatings.{{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 }}{{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}} Other uses include direct to metal coatings.{{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}} 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.{{Cite journal|last1=Gite|first1=V. V.|last2=Mahulikar|first2=P. P.|last3=Hundiwale|first3=D. G.|date=2010-08-01|title=Preparation and properties of polyurethane coatings based on acrylic polyols and trimer of isophorone diisocyanate|url=https://www.sciencedirect.com/science/article/pii/S030094401000086X|journal=Progress in Organic Coatings|language=en|volume=68|issue=4|pages=307–312|doi=10.1016/j.porgcoat.2010.03.008|issn=0300-9440|url-access=subscription}}

Caprolactone-based polyols produce polyurethanes with enhanced hydrolysis resistance.{{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}}{{Cite journal|last1=Huang|first1=Shan|last2=Xiao|first2=Juan|last3=Zhu|first3=Yan’an|last4=Qu|first4=Jinqing|date=2017-05-01|title=Synthesis and properties of spray-applied high solid content two component polyurethane coatings based on polycaprolactone polyols|url=https://www.sciencedirect.com/science/article/pii/S030094401630786X|journal=Progress in Organic Coatings|language=en|volume=106|pages=60–68|doi=10.1016/j.porgcoat.2017.02.011|issn=0300-9440|url-access=subscription}}

Polycarbonate polyols are more expensive than other polyols and are thus used in more demanding applications.{{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. |display-authors=3|date=2016-12-13 |title=Dynamics of Polyether Polyols and Polyether Carbonate Polyols |url=https://pubs.acs.org/doi/10.1021/acs.macromol.6b01601 |journal=Macromolecules |language=en |volume=49 |issue=23 |pages=8995–9003 |doi=10.1021/acs.macromol.6b01601 |bibcode=2016MaMol..49.8995P |issn=0024-9297|url-access=subscription }}{{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}} They have been used to make an isophorone diisocyanate based prepolymer which is then used in glass coatings.{{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}} They may be used in reactive hotmelt adhesives.{{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}}

All polyols may be used to produce polyurethane prepolymers.{{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}}{{Cite journal|last1=Shi|first1=Minxian|last2=Zheng|first2=Juanli|last3=Huang|first3=Zhixiong|last4=Qin|first4=Yan|date=2011-03-01|title=Synthesis of Polyurethane Prepolymers and Damping Property of Polyurethane/Epoxy Composites|url=https://www.ingentaconnect.com/contentone/asp/asl/2011/00000004/00000003/art00020|journal=Advanced Science Letters|volume=4|issue=3|pages=740–744|doi=10.1166/asl.2011.1597|url-access=subscription}}{{Cite journal|last1=Pokharel|first1=Pashupati|last2=Lee|first2=Dai Soo|date=2014-10-01|title=High performance polyurethane nanocomposite films prepared from a masterbatch of graphene oxide in polyether polyol|url=https://www.sciencedirect.com/science/article/pii/S1385894714006214|journal=Chemical Engineering Journal|language=en|volume=253|pages=356–365|doi=10.1016/j.cej.2014.05.046|bibcode=2014ChEnJ.253..356P |issn=1385-8947|url-access=subscription}} These then find use in coatings,{{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}} adhesives, sealants and elastomers.{{Cite journal|last1=Wang|first1=Lei|last2=Shen|first2=Yiding|last3=Lai|first3=Xiaojuan|last4=Li|first4=Zhongjin|last5=Liu|first5=Min|display-authors=3|date=2011-05-01|title=Synthesis and properties of crosslinked waterborne polyurethane|url=https://doi.org/10.1007/s10965-010-9438-9|journal=Journal of Polymer Research|language=en|volume=18|issue=3|pages=469–476|doi=10.1007/s10965-010-9438-9|s2cid=56442579 |issn=1572-8935|url-access=subscription}}

File:Glyptal.svg derived from the polyol glycerol (red, a low molecular weight polyol) and phthalic anhydride.]]

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.{{Ullmann | author = Frank N. Jones | title = Alkyd Resins | doi = 10.1002/14356007.a01_409}} 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.

Sugar alcohols, a class of low molecular weight polyols, are commonly obtained by hydrogenation of sugars.{{Cite journal |last1=Malani |first1=Ritesh S. |last2=Malshe |first2=Vinod C. |last3=Thorat |first3=Bhaskar Narayan |year=2022 |title=Polyols and polyurethanes from renewable sources: past, present, and future—part 2: plant-derived materials |url=https://doi.org/10.1007/s11998-021-00534-5 |journal=Journal of Coatings Technology and Research |language=en |volume=19 |issue=2 |pages=361–375 |doi=10.1007/s11998-021-00534-5 |s2cid=246083110 |issn=1935-3804|url-access=subscription }}{{rp|363}} They have the formula (CHOH)_nH₂, where n = 4–6.{{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}}

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.

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.{{Citation|title=4,4′-Methylene diphenyl isocyanate (MDI) and polymeric MDI″ (PMDI) [MAK Value Documentation, 1997]|date=2012|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/3527600418.mb10168stae0008|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|access-date=2022-02-12}} 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.{{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 }}

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.

There are polyols based on renewable sources such as plant-based materials including castor oil and cottonseed oil.{{Cite journal |last1=Nelson |first1=Thomas J. |last2=Masaki |first2=Bryan |last3=Morseth |first3=Zachary |last4=Webster |first4=Dean C. |date=2013-11-01 |title=Highly functional biobased polyols and their use in melamine–formaldehyde coatings |url=https://doi.org/10.1007/s11998-013-9524-0 |journal=Journal of Coatings Technology and Research |language=en |volume=10 |issue=6 |pages=757–767 |doi=10.1007/s11998-013-9524-0 |s2cid=93718470 |issn=1935-3804 |access-date=2023-03-09 |archive-date=2023-03-14 |archive-url=https://web.archive.org/web/20230314202621/https://link.springer.com/article/10.1007/s11998-013-9524-0 |url-status=live |url-access=subscription }}{{Cite journal |last1=Jia |first1=Lian Kun |last2=Gong |first2=Li Xiang |last3=Ji |first3=Wen Jiao |last4=Kan |first4=Cheng You |date=2011-11-01 |title=Synthesis of vegetable oil based polyol with cottonseed oil and sorbitol derived from natural source |url=https://www.sciencedirect.com/science/article/pii/S1001841711001860 |journal=Chinese Chemical Letters |language=en |volume=22 |issue=11 |pages=1289–1292 |doi=10.1016/j.cclet.2011.05.043 |issn=1001-8417|url-access=subscription }}{{Cite journal |last1=Narute |first1=Prashant |last2=Palanisamy |first2=Aruna |date=2016-01-01 |title=Study of the performance of polyurethane coatings derived from cottonseed oil polyol |url=https://doi.org/10.1007/s11998-015-9741-9 |journal=Journal of Coatings Technology and Research |language=en |volume=13 |issue=1 |pages=171–179 |doi=10.1007/s11998-015-9741-9 |s2cid=98726099 |issn=1935-3804|url-access=subscription }} Vegetable oils and biomass are also potential renewable polyol raw materials.{{Cite journal |last1=Malani |first1=Ritesh S. |last2=Malshe |first2=Vinod C. |last3=Thorat |first3=Bhaskar Narayan |year=2022 |title=Polyols and polyurethanes from renewable sources: past, present and future—part 1: vegetable oils and lignocellulosic biomass |url=https://doi.org/10.1007/s11998-021-00490-0 |journal=Journal of Coatings Technology and Research |language=en |volume=19 |issue=1 |pages=201–222 |doi=10.1007/s11998-021-00490-0 |s2cid=235442129 |issn=1935-3804|url-access=subscription }} Seed oil can even be used to produce polyester polyols.{{Cite journal |last1=Argyropoulos |first1=John |last2=Popa |first2=Paul |last3=Spilman |first3=Gary |last4=Bhattacharjee |first4=Debkumar |last5=Koonce |first5=William |date=2009-12-01 |title=Seed oil based polyester polyols for coatings |url=https://doi.org/10.1007/s11998-008-9154-0 |journal=Journal of Coatings Technology and Research |language=en |volume=6 |issue=4 |pages=501–508 |doi=10.1007/s11998-008-9154-0 |s2cid=96095676 |issn=1935-3804 |access-date=2023-03-14 |archive-date=2023-03-14 |archive-url=https://web.archive.org/web/20230314202649/https://link.springer.com/article/10.1007/s11998-008-9154-0 |url-status=live |url-access=subscription }}

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.

• Cyclitol
• Oligomer
• Polyurethane

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{{reflist|30em}}

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