Editing Castor oil (section)

===Coatings===
Castor oil is used as a biobased [[polyol]] in the [[polyurethane]] industry. The average functionality (number of [[hydroxyl]] groups per triglyceride molecule) of castor oil is 2.7, so it is widely used as a rigid polyol and in coatings.<ref name=ullmanns/> 
One particular use is in a polyurethane concrete where a castor-oil emulsion is reacted with an isocyanate (usually polymeric [[methylene diphenyl diisocyanate]]) and a [[cement]] and [[construction aggregate]]. This is applied fairly thickly as a slurry, which is self-levelling. This base is usually further coated with other systems to build a resilient floor.<ref>{{Cite journal|last=Howarth|first=GA|date=June 2003|title=Polyurethanes, polyurethane dispersions and polyureas: Past, present and future|journal=Surface Coatings International Part B: Coatings Transactions|language=en|volume=86|issue=2|pages=111–118|doi=10.1007/bf02699621|s2cid=93574741|issn=1476-4865}}</ref> Castor oil is not a [[drying oil]], meaning that it has a low reactivity with air compared with oils such as [[linseed oil]] and [[tung oil]]. However, dehydration of castor oil yields linoleic acids, which do have drying properties.<ref name=ullmanns/> 
In this process, the OH group on the ricinoleic acid along with a hydrogen from the next carbon atom are removed, forming a double bond which then has oxidative cross-linking properties and yields the drying oil. It is considered a vital raw material.<ref>{{Cite journal |last=Ogunniyi |first=D. S. |date=2006-06-01 |title=Castor oil: A vital industrial raw material |url=https://www.sciencedirect.com/science/article/pii/S0960852405002026 |journal=Bioresource Technology |language=en |volume=97 |issue=9 |pages=1086–1091 |doi=10.1016/j.biortech.2005.03.028 |pmid=15919203 |bibcode=2006BiTec..97.1086O |issn=0960-8524 |access-date=2023-03-09 |archive-date=2016-11-30 |archive-url=https://web.archive.org/web/20161130045802/http://www.sciencedirect.com/science/article/pii/S0960852405002026 |url-status=live }}</ref>