Editing Polyurethane (section)

==Raw materials==
The main ingredients to make a polyurethane are di- and tri-[[isocyanates]] and [[polyols]]. Other materials are added to aid processing the polymer or to modify the properties of the polymer. PU foam formulation sometimes have water added too.

===Isocyanates===
Isocyanates used to make polyurethane have two or more isocyanate groups on each molecule. The most commonly used isocyanates are the [[aromaticity|aromatic]] diisocyanates,  [[toluene diisocyanate]] (TDI) and [[methylene diphenyl diisocyanate]], (MDI). These aromatic isocyanates are more reactive than [[aliphatic]] isocyanates.

TDI and MDI are generally less expensive and more reactive than other isocyanates. Industrial grade TDI and MDI are mixtures of isomers and MDI often contains polymeric materials. They are used to make flexible foam (for example slabstock foam for mattresses or molded foams for car seats),<ref>{{cite web|url=http://dowglobal.beta.ides.com/DocSelect.aspx?DOC=DOWTDS&E=101414|title=Technical data sheet from Dow Chemical|access-date=2007-09-15|archive-date=2007-10-13|archive-url=https://web.archive.org/web/20071013154430/http://dowglobal.beta.ides.com/DocSelect.aspx?DOC=DOWTDS&E=101414|url-status=dead}}</ref> rigid foam (for example insulating foam in refrigerators) elastomers (shoe soles, for example), and so on. The isocyanates may be modified by partially reacting them with polyols or introducing some other materials to reduce volatility (and hence toxicity) of the isocyanates, decrease their freezing points to make handling easier or to improve the properties of the final polymers.

[[File:MDI isomers v2.svg|class=skin-invert-image|500px|center|MDI isomers and polymer]]

Aliphatic and cycloaliphatic isocyanates are used in smaller quantities, most often in coatings and other applications where color and transparency are important since polyurethanes made with aromatic isocyanates tend to darken on exposure to light.{{page needed|date=August 2023}}<ref>{{cite book | first1=David | last1=Randall |last2=Lee|first2= Steve | title=The Polyurethanes Book | publisher=Wiley | location=New York | year=2002 | isbn=978-0-470-85041-1}}</ref> The most important aliphatic and cycloaliphatic isocyanates are [[hexamethylene diisocyanate|1,6-hexamethylene diisocyanate]] (HDI), 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethyl-cyclohexane ([[isophorone diisocyanate]], IPDI), and [[hydrogenated MDI|4,4′-diisocyanato dicyclohexylmethane]] (H<sub>12</sub>MDI or hydrogenated MDI). Other more specialized isocyanates include [[Tetramethylxylylene diisocyanate]] (TMXDI).

===Polyols===
{{main|Polyol}}
[[Polyols#Polyols in polymer chemistry|Polyols]] are polymers in their own right and have on average two or more hydroxyl groups per molecule. They can be converted to polyether polyols by co-polymerizing [[ethylene oxide]] and [[propylene oxide]] with a suitable polyol precursor.<ref>{{cite journal|title=Polyurethanes from Vegetable Oils|first=Zoran S. |last=Petrović |journal=Polymer Reviews |volume=48 |issue=1 |date=2008|pages=109–155 |doi=10.1080/15583720701834224 |s2cid=95466690 }}</ref> Polyester polyols are made by the polycondensation of multifunctional [[carboxylic acid]]s and polyhydroxyl compounds. They can be further classified according to their end use. Higher molecular weight polyols (molecular weights from 2,000 to 10,000) are used to make more flexible polyurethanes while lower molecular weight polyols make more rigid products.

Polyols for flexible applications use low functionality initiators such as [[dipropylene glycol]] (''f''&nbsp;=&nbsp;2), [[glycerine]] (''f''&nbsp;=&nbsp;3), or a sorbitol/water solution (''f''&nbsp;=&nbsp;2.75).<ref>{{cite patent|title=Polyether polyols suitable for flexible polyurethane foam prepared by co-initiation of aqueous solutions of solid polyhydroxyl initiators|pubdate=1997-01-29|inventor1-last=Hager|inventor2-last=Knight|inventor3-last=Helma|inventor1-first=Stanley L.|inventor2-first=James E.|inventor3-first=Gregory F.|inventor4-last=Argento|inventor4-first=Ben J.|country=EP|number=0755955|assign=[[ARCO#ARCO Chemical|ARCO Chemical Technology]]}}</ref> Polyols for rigid applications use higher functionality initiators such as [[sucrose]] (''f''&nbsp;=&nbsp;8), [[sorbitol]] (''f''&nbsp;=&nbsp;6), [[toluenediamine]] (''f''&nbsp;=&nbsp;4), and [[Mannich base]]s (''f''&nbsp;=&nbsp;4). [[Propylene oxide]] and/or [[ethylene oxide]] is added to the initiators until the desired molecular weight is achieved. The order of addition and the amounts of each oxide affect many polyol properties, such as compatibility, water-solubility, and reactivity. Polyols made with only propylene oxide are terminated with secondary hydroxyl groups and are less reactive than polyols capped with ethylene oxide, which contain primary hydroxyl groups.  Incorporating carbon dioxide into the polyol structure is being researched by multiple companies.

Graft polyols (also called filled polyols or polymer polyols) contain finely dispersed [[Copolymer|styrene–acrylonitrile]], [[acrylonitrile]], or polyurea (PHD) polymer solids chemically grafted to a high molecular weight polyether backbone. They are used to increase the load-bearing properties of low-density high-resiliency (HR) foam, as well as add toughness to microcellular foams and cast elastomers. Initiators such as [[ethylenediamine]] and [[triethanolamine]] are used to make low molecular weight rigid foam polyols that have built-in catalytic activity due to the presence of nitrogen atoms in the backbone. A special class of polyether polyols, [[poly(tetramethylene ether) glycol]]s, which are made by polymerizing [[tetrahydrofuran]], are used in high performance coating, wetting and elastomer applications.

Conventional polyester polyols are based on virgin raw materials and are manufactured by the direct polyesterification of high-purity diacids and glycols, such as adipic acid and 1,4-butanediol. Polyester polyols are usually more expensive and more viscous than polyether polyols, but they make polyurethanes with better solvent, abrasion, and cut resistance. Other polyester polyols are based on reclaimed raw materials. They are manufactured by transesterification ([[glycolysis]]) of recycled [[Polyethylene terephthalate|poly(ethyleneterephthalate)]] (PET) or [[dimethylterephthalate]] (DMT) distillation bottoms with glycols such as diethylene glycol. These low molecular weight, aromatic polyester polyols are used in rigid foam, and bring low cost and excellent flammability characteristics to [[polyisocyanurate]] (PIR) boardstock and polyurethane spray foam insulation.

Specialty polyols include [[polycarbonate]] polyols, [[polycaprolactone]] polyols, [[polybutadiene]] polyols, and [[polysulfide]] polyols. The materials are used in elastomer, sealant, and adhesive applications that require superior weatherability, and resistance to chemical and environmental attack. [[Natural oil polyols]] derived from [[castor oil]] and other [[vegetable oils]] are used to make elastomers, flexible bunstock, and flexible molded foam.

Co-polymerizing [[chlorotrifluoroethylene]] or [[tetrafluoroethylene]] with vinyl ethers containing hydroxyalkyl vinyl ether produces fluorinated (FEVE) polyols. Two-component fluorinated polyurethanes prepared by reacting FEVE fluorinated polyols with polyisocyanate have been used to make ambient cure paints and coatings. Since fluorinated polyurethanes contain a high percentage of fluorine–carbon bonds, which are the strongest bonds among all chemical bonds, fluorinated polyurethanes exhibit resistance to UV, acids, alkali, salts, chemicals, solvents, weathering, corrosion, fungi and microbial attack. These have been used for high performance coatings and paints.<ref>{{cite web |author=Bob Parker |title=FEVE Technology for Higher Performance Coating Systems on Bridges |url=https://www.paintsquare.com/library/articles/(038-47)BridgeResins01-15.pdf#:~:text=The%20FEVE%20polyol%20resins%20play%20an%20integral%20part,coating%20systems%20across%20the%20globe%20since%20its%20introduction |url-status=dead |archive-url=https://web.archive.org/web/20210815112712/https://www.paintsquare.com/library/articles/(038-47)BridgeResins01-15.pdf |archive-date=15 August 2021 |access-date=5 March 2022 |website=Paintsquare.com}}</ref>

[[Phosphorus]]-containing polyols are available that become [[Chemical bond|chemically bonded]] to the polyurethane matrix for the use as [[flame retardants]]. This covalent linkage prevents migration and leaching of the [[organophosphorus compound]].

===Bio-derived materials===
Interest in [[sustainable]] [[green chemistry|"green"]] products raised interest in polyols derived from [[vegetable oil]]s,<ref>Khanderay, Jitendra C., and Vikas V. Gite. "Vegetable oil-based polyurethane coatings: recent developments in India." Green Materials 5.3 (2017): 109-122.</ref><ref name="ussc">
{{cite conference
  | last1 = Niemeyer | first1 = Timothy
  | last2= Patel    | first2= Munjal
  | last3= Geiger   | first3= Eric
  | title =A Further Examination of Soy-Based Polyols in Polyurethane Systems
  | publisher = Alliance for the Polyurethane Industry Technical Conference
  | date = September 2006
  | location = Salt Lake City, UT
}}</ref><ref>
{{cite news
  | title = New Twist on Green: 2008 Ford Mustang Seats Will Be Soy-Based Foam
  | publisher = Edmunds inside line
  | date = July 12, 2007
  | url = http://www.edmunds.com/insideline/do/News/articleId=121682
  | access-date = 2010-06-15
  | archive-url = https://web.archive.org/web/20080531084933/http://www.edmunds.com/insideline/do/News/articleId=121682 
  | archive-date = 2008-05-31
}}</ref> fatty acids,<ref>SD Rajput, PP Mahulikar, VV Gite, Biobased dimer fatty acid containing two pack polyurethane for wood finished coatings, Progress in Organic Coatings 77 (1), 38-46
https://doi.org/10.1016/j.porgcoat.2014.04.030</ref> lignin, [[sorbitol]],<ref>A Anand, RD Kulkarni, VV Gite, Preparation and properties of eco-friendly two pack PU coatings based on renewable source (sorbitol) and its property improvement by nano ZnO, Progress in Organic Coatings 74 (4), 764-767, https://doi.org/10.1016/j.porgcoat.2011.09.031</ref> etc. These are mostly contributing to [[polyol]] part.  There are attempts made to prepare isocyanate part using bio-derived material.  However, as far as commercialization is concern, polyol part is more targeted being easy and required in more quantity than [[isocyanate]] part.  Various oils used in the preparation polyols for polyurethanes include [[soybean oil]], [[cottonseed oil]], [[neem seed oil]], [[algae]] oil,<ref>Chandrashekhar K Patil, Harishchandra D Jirimali, Jayasinh S Paradeshi, Bhushan L Chaudhari, Prakash K Alagi, Pramod P Mahulikar, Sung Chul Hong, Vikas V Gite, Chemical transformation of renewable algae oil to polyetheramide polyols for polyurethane coatings, Progress in Organic Coatings 151, 106084, https://doi.org/10.1016/j.porgcoat.2020.106084</ref><ref>CK Patil, HD Jirimali, JS Paradeshi, BL Chaudhari, VV Gite, Functional antimicrobial and anticorrosive polyurethane composite coatings from algae oil and silver doped egg shell hydroxyapatite for sustainable development, Progress in Organic Coatings 128, 127-136, https://doi.org/10.1016/j.porgcoat.2018.11.002</ref> and [[castor oil]]. Vegetable oils are functionalized in various ways and modified to [[polyetheramide]]s, [[polyether]]s, [[alkyd]]s, etc. Renewable sources used to prepare polyols may be [[fatty acid]]s or [[dimer acid|dimer fatty acids]].<ref>Biobased dimer fatty acid containing two pack polyurethane for wood finished coatings, SD Rajput, PP Mahulikar, VV Gite, Progress in Organic Coatings 77 (1), 38-46</ref> Some biobased and isocyanate-free polyurethanes exploit the reaction between [[polyamine]]s and cyclic carbonates to produce [[polyhydroxyurethane]]s.<ref name="From Petrochemical Polyurethanes to Biobased Polyhydroxyurethanes">{{cite journal |doi=10.1021/ma400197c |title=From Petrochemical Polyurethanes to Biobased Polyhydroxyurethanes |journal=Macromolecules |volume=46 |issue=10 |pages=3771–92 |year=2013 |last1=Nohra |first1=Bassam |last2=Candy |first2=Laure |last3=Blanco |first3=Jean-François |last4=Guerin |first4=Celine |last5=Raoul |first5=Yann |last6=Mouloungui |first6=Zephirin |bibcode=2013MaMol..46.3771N |url=http://oatao.univ-toulouse.fr/9942/1/Nohra_9942.pdf |archive-url=https://web.archive.org/web/20170922043448/http://oatao.univ-toulouse.fr/9942/1/Nohra_9942.pdf |archive-date=2017-09-22 |url-status=live }}</ref>

===Chain extenders and cross linkers===
[[Chain extender]]s (''f''&nbsp;=&nbsp;2) and [[cross-link|cross linkers]] (''f''&nbsp;≥&nbsp;3) are low molecular weight hydroxyl and amine terminated compounds that play an important role in the polymer morphology of polyurethane fibers, elastomers, adhesives, and certain integral skin and microcellular foams.

The elastomeric properties of these materials are derived from the phase separation of the hard and soft copolymer segments of the polymer, such that the urethane hard segment domains serve as cross-links between the amorphous polyether (or polyester) soft segment domains. This phase separation occurs because the mainly nonpolar, low melting soft segments are incompatible with the polar, high melting hard segments. The soft segments, which are formed from high molecular weight polyols, are mobile and are normally present in coiled formation, while the hard segments, which are formed from the isocyanate and chain extenders, are stiff and immobile. As the hard segments are covalently coupled to the soft segments, they inhibit plastic flow of the polymer chains, thus creating elastomeric resiliency. Upon mechanical deformation, a portion of the soft segments are stressed by uncoiling, and the hard segments become aligned in the stress direction. This reorientation of the hard segments and consequent powerful hydrogen bonding contributes to high tensile strength, elongation, and tear resistance values.<ref name="Oertel 1985"/><ref>{{cite journal| first1=J. | last1=Blackwell |first2=M. R.|last2= Nagarajan |first3=T. B.|last3= Hoitink | title=The Structure of the Hard Segments in MDI/diol/PTMA Polyurethane Elastomers |journal=ACS Symposium Series| volume=172 | pages=179–196 | publisher=American Chemical Society | location=Washington, D.C. | year=1981 | issn=0097-6156| doi=10.1021/bk-1981-0172.ch014 | isbn=978-0-8412-0664-9 }}</ref><ref>{{cite journal | first1=John | last1=Blackwell |first2=Kenncorwin H.|last2= Gardner | title=Structure of the hard segments in polyurethane elastomers | journal=Polymer | year=1979 | issn=0032-3861 | doi = 10.1016/0032-3861(79)90035-1 | volume=20 | issue=1 | pages=13–17}}</ref><ref>{{cite conference | last1=Grillo | first1=D. J. |last2=Housel|first2= T. L. | title=Physical Properties of Polyurethanes from Polyesters and Other Polyols | book-title=Polyurethanes '92 Conference Proceedings  | publisher=The Society of the Plastics Industry, Inc. | year=1992 | location=New Orleans, LA }}</ref><ref>{{cite conference | last1=Musselman | first1=S. G. |last2=Santosusso|first2= T. M. |last3=Sperling|first3= L. H. | title=Structure Versus Performance Properties of Cast Elastomers | book-title=Polyurethanes '98 Conference Proceedings | publisher=The Society of the Plastics Industry, Inc. | year=1998 | location=Dallas, TX }}</ref>
The choice of chain extender also determines flexural, heat, and chemical resistance properties.

The most important chain extenders are [[ethylene glycol]], [[1,4-butanediol]] (1,4-BDO or BDO), [[1,6-hexanediol]], [[cyclohexane dimethanol]] and hydroquinone bis(2-hydroxyethyl) ether (HQEE). All of these glycols form polyurethanes that phase separate well and form well defined hard segment domains, and are melt processable. They are all suitable for [[thermoplastic polyurethanes]] with the exception of ethylene glycol, since its derived bis-phenyl urethane undergoes unfavorable degradation at high hard segment levels.<ref name="Gum 1992"/> Diethanolamine and triethanolamine are used in flex molded foams to build firmness and add catalytic activity. Diethyltoluenediamine is used extensively in RIM, and in polyurethane and polyurea elastomer formulations.

{| class="wikitable plainrowheaders" style="text-align: center;"
|+Table of chain extenders and cross linkers<ref>
{{Cite book
  | title = A Guide to Glycols
  | id = Brochure 117-00991-92Hyc
  | location = Midland, Mich.
  | publisher = The Dow Chemical Co., Chemicals and Metals Department
  | year = 1992}}
</ref>
|-
!scope="col"|Compound type
!scope="col"|Molecule
! scope="col"|[[Molecular weight|Mol. <br />mass]]
! scope="col"| Density<br />(g/cm{{sup|3}})
! scope="col"| [[Melting point|Melting <br />pt]] (°C)
! scope="col"|[[Boiling point|Boiling <br />pt]] (°C)
|-
|rowspan="18"| Hydroxyl compounds – difunctional molecules
!scope="row"|[[Ethylene glycol]]
| 62.1 || 1.110 || −13.4 || 197.4
|-
!scope="row" |[[Diethylene glycol]]
| 106.1 || 1.111 || −8.7 || 245.5
|-
!scope="row" |[[Triethylene glycol]]
| 150.2 || 1.120 || −7.2 || 287.8
|-
!scope="row" |[[Tetraethylene glycol]]
| 194.2 || 1.123 || −9.4 || 325.6
|-
!scope="row" |[[Propylene glycol]]
| 76.1 || 1.032 || [[Supercooling|Supercools]] || 187.4
|-
!scope="row" |[[Dipropylene glycol]]
| 134.2 || 1.022 || Supercools || 232.2
|-
!scope="row" |[[Tripropylene glycol]]
| 192.3 || 1.110 || Supercools || 265.1
|-
!scope="row" |[[1,3-Propanediol]]
| 76.1 || 1.060 || −28 || 210
|-
!scope="row" |[[1,3-Butanediol]]
| 92.1 || 1.005 || — || 207.5
|-
!scope="row" |[[1,4-Butanediol]]
| 92.1 || 1.017 || 20.1 || 235
|-
!scope="row" |[[Neopentyl glycol]]
| 104.2 || — || 130 || 206
|-
!scope="row" |[[1,6-Hexanediol]]
| 118.2 || 1.017 || 43 || 250
|-
!scope="row" |[[1,4-Cyclohexanedimethanol]]
| — || — || — || —
|-
!scope="row" |[[HQEE]]
| — || — || — || —
|-
!scope="row" |[[Ethanolamine]]
|61.1 || 1.018 || 10.3 || 170
|-
!scope="row" |[[Diethanolamine]]
| 105.1 || 1.097 || 28 || 271
|-
!scope="row" |[[Methyldiethanolamine]]
| 119.1 || 1.043 || −21 || 242
|-
!scope="row" |[[Phenyldiethanolamine]]
| 181.2 || — || 58 || 228
|-
|rowspan="4"| Hydroxyl compounds – trifunctional molecules
!scope="row" |[[Glycerol]]
| 92.1 || 1.261 || 18.0 || 290
|-
!scope="row" |[[Trimethylolpropane]]
| — || — || — || —
|-
!scope="row" |[[1,2,6-Hexanetriol]]
| — || — || — || —
|-
!scope="row" |[[Triethanolamine]]
|149.2 || 1.124 || 21 || —
|-
|rowspan="2"| Hydroxyl compounds – tetrafunctional molecules
!scope="row" |[[Pentaerythritol]]
| 136.2 || — || 260.5 || —
|-
!scope="row" |''N'',''N'',''N''′,''N''′-Tetrakis<br />(2-hydroxypropyl)<br />ethylenediamine
| — || — || — || —
|-
|rowspan="2"| Amine compounds – difunctional molecules
!scope="row" |[[Diethyltoluenediamine]]
| 178.3 || 1.022 || — || 308
|-
!scope="row" |[[Dimethylthiotoluenediamine]]
| 214.0 || 1.208 || — || —
|}

===Catalysts===
{{main|catalyst}}
Polyurethane [[catalyst]]s can be classified into two broad categories, basic and acidic [[amine]]. [[Tertiary amine]] catalysts function by enhancing the nucleophilicity of the diol component. Alkyl tin carboxylates, oxides and mercaptides oxides function as mild Lewis acids in accelerating the formation of polyurethane. As bases, traditional amine catalysts include triethylenediamine (TEDA, also called [[DABCO]], 1,4-diazabicyclo[2.2.2]octane), [[dimethylcyclohexylamine]] (DMCHA), [[dimethylethanolamine]] (DMEA), [[Dimethylaminoethoxyethanol]] and bis-(2-dimethylaminoethyl)ether, a blowing catalyst also called A-99. A typical Lewis acidic catalyst is [[dibutyltin dilaurate]]. The process is highly sensitive to the nature of the catalyst and is also known to be [[autocatalytic]].<ref>{{Ullmann |doi=10.1002/14356007.a21_665.pub2 |title=Polyurethanes |year=2005 |last1=Adam |first1=Norbert |last2=Avar |first2=Geza |last3=Blankenheim |first3=Herbert |last4=Friederichs |first4=Wolfgang |last5=Giersig |first5=Manfred |last6=Weigand |first6=Eckehard |last7=Halfmann |first7=Michael |last8=Wittbecker |first8=Friedrich-Wilhelm |last9=Larimer |first9=Donald-Richard |last10=Maier |first10=Udo |last11=Meyer-Ahrens |first11=Sven |last12=Noble |first12=Karl-Ludwig |last13=Wussow |first13=Hans-Georg |isbn=978-3-527-30673-2 }}</ref>

Another class of catalysts was published in a study in May 2024. In this study, polyurethane synthesis was investigated in the presence of acid catalysts, namely [[dimethylphosphite]] (DMHP), [[methanesulfonic acid]] (MSA), and [[trifluoromethanesulfonic acid]] (TFMSA). The thermodynamic profile was examined and described in detail through computational tools, showing that TFMSA had the best catalytic properties. The study aimed to open the door to a new class of catalysts.<ref name= "Urethane Synthesis in the Presence of Organic Acid Catalysts—A Computational Study">{{Cite journal|title=Urethane Synthesis in the Presence of Organic Acid Catalysts—A Computational Study|date=2024 |pmc=11123846 |language=en |last1=Waleed |first1=H. Q. |last2=Viskolcz |first2=B. |last3=Fiser |first3=B. |journal=Molecules (Basel, Switzerland) |volume=29 |issue=10 |page=2375 |doi=10.3390/molecules29102375 |doi-access=free |pmid=38792235 }}</ref>

Factors affecting catalyst selection include balancing three reactions: urethane (polyol+isocyanate, or gel) formation, the urea (water+isocyanate, or "blow") formation, or the isocyanate trimerization reaction (e.g., using potassium acetate, to form [[isocyanurate]] rings). A variety of specialized catalysts have been developed.<ref>{{cite web | title = Jeffcat Amine Catalysts for the Polyurethane Industry | year = 2006 | url = http://www.huntsman.com/performance_products/Media/JEFFCAT_Catalyst_Trifold_bulletin.pdf | access-date = 2007-10-23 |archive-url = https://web.archive.org/web/20071129082418/http://www.huntsman.com/performance_products/Media/JEFFCAT_Catalyst_Trifold_bulletin.pdf <!-- Bot retrieved archive --> |archive-date = 2007-11-29}}</ref><ref>{{cite web | title = Building quality with Air Products trimerisation catalysts | year = 2003 | url = http://www.airproducts.com/NR/rdonlyres/55C5A72A-D126-4888-9E1A-D24EFBE4AAC1/0/14004004EU.pdf | access-date = 2007-10-23 | archive-date = 2007-11-29 | archive-url = https://web.archive.org/web/20071129082418/http://www.airproducts.com/NR/rdonlyres/55C5A72A-D126-4888-9E1A-D24EFBE4AAC1/0/14004004EU.pdf | url-status = dead }}</ref><ref>{{Cite journal | title = FOMREZ Specialty Tin Catalysts for Polyurethane Applications | journal = 120-074-10 | date = January 2001}}</ref>

===Surfactants===
{{main|surfactant}}
[[Surfactants]] are used to modify the characteristics of both foam and non-foam polyurethane polymers. They take the form of polydimethylsiloxane-polyoxyalkylene block copolymers, [[silicone]] oils, [[nonylphenol]] ethoxylates, and other organic compounds. In foams, they are used to emulsify the liquid components, regulate cell size, and stabilize the cell structure to prevent collapse and sub-surface voids.<ref>{{cite book |year=2002 |chapter=10 |editor1-last=Randall |editor1-first=David |editor2-last=Lee |editor2-first=Steve |title=The Polyurethanes Book |chapter-url=https://www.wiley.com/en-us/The+Polyurethanes+Book-p-9780470850411 |location=The United Kingdom |publisher=Huntsman International LLC, Polyurethanes business |pages=156–159 |isbn=978-0470850411 |archive-date=2018-05-24 |access-date=2018-05-23 |archive-url=https://web.archive.org/web/20180524083953/https://www.wiley.com/en-us/The+Polyurethanes+Book-p-9780470850411 |url-status=dead }}</ref> In non-foam applications they are used as air release and antifoaming agents, as wetting agents, and are used to eliminate surface defects such as pin holes, orange peel, and sink marks.