Editing Cashew (section)

=== Shell oil ===
{{See also|Urushiol}}

Cashew nutshell liquid (CNSL) or cashew shell oil ([[CAS registry number]] 8007-24-7) is a natural [[resin]] with a yellowish [[Paint sheen|sheen]] found in the [[honeycomb structure]] of the cashew nutshell, and is a byproduct of processing cashew nuts. Since it is a strong irritant, it should not be confused with edible cashew nut oil. It is dangerous to handle in small-scale processing of the shells, but is itself a raw material with multiple uses.<ref name=hamad/> It is used in tropical [[folk medicine]] and for anti-[[termite]] treatment of timber.<ref name=clay />  Its composition varies depending on how it is processed.
* Cold, [[Liquid–liquid extraction|solvent-extracted]] CNSL is mostly composed of [[anacardic acids]] (70%),<ref name=cen/> [[cardol]] (18%), and [[cardanol]] (5%).<ref name=hamad/><ref name=epa>{{cite web|url=http://www.epa.gov/hpv/pubs/summaries/casntliq/c13793rr3.pdf|title=Exposure and Use Data for Cashew Nut Shell Liquid|publisher=[[United States Environmental Protection Agency]]|access-date=12 January 2012|archive-url=https://web.archive.org/web/20130512194341/http://www.epa.gov/hpv/pubs/summaries/casntliq/c13793rr3.pdf|archive-date=12 May 2013|url-status=dead}}</ref>
* Heating CNSL [[decarboxylation|decarboxylates]] the anacardic acids, producing a technical grade of CNSL that is rich in cardanol. [[Distillation]] of this material gives distilled, technical CNSL containing 78% cardanol and 8% cardol (cardol has one more [[hydroxyl]] group than cardanol).<ref name=epa/> This process also reduces the degree of thermal [[polymerization]] of the unsaturated alkyl-phenols present in CNSL.
* Anacardic acid is also used in the chemical industry for the production of cardanol, which is used for resins, coatings, and frictional materials.<ref name=cen>{{cite journal|doi=10.1021/cen-v086n033.p026|title=A Nutty Chemical|date=8 September 2008 |volume=86|issue=36|pages=26–27|author=Alexander H. Tullo|journal=[[Chemical and Engineering News]]}}</ref><ref name=epa />

These substances are skin allergens, like [[Toxicodendron vernicifluum#Lacquer|lacquer]] and the oils of poison ivy, and they present a danger during manual cashew processing.<ref name=clay>{{Cite book|last=Clay|first=Jason|url=https://books.google.com/books?id=_RU8D9kB714C&q=nutshell+liquid&pg=PA268|title=World Agriculture and the Environment: A Commodity-By-Commodity Guide To Impacts And Practices|date=March 2004|publisher=Island Press|isbn=978-1-55963-370-3|language=en |page=268}}</ref>

This natural oil phenol has interesting chemical structural features that can be modified to create a wide spectrum of biobased [[monomer]]s. These capitalize on the chemically-versatile construct, which contains three [[functional group]]s: The [[aromatic ring]], the [[hydroxyl group]], and the [[double bond]]s in the flanking [[alkyl]] chain. These include [[polyols]], which have recently seen increased demand for their biobased origin and key chemical attributes such as high reactivity, range of functionalities, reduction in blowing agents, and naturally occurring fire retardant properties in the field of rigid polyurethanes, aided by their inherent phenolic structure and larger number of reactive units per unit mass.<ref name=hamad/>

CNSL may be used as a resin for [[carbon composite]] products.<ref>{{cite web|last=Ferri|first=Enrico|title=Bioresins Derived from Cashew Nutshell Oil|url=http://www.materialstoday.com/composite-processing/features/bio-resins-derived-from-cashew-nutshell-oil/|publisher=MaterialsToday|access-date=7 September 2011|date=22 May 2011|archive-url=https://web.archive.org/web/20150910171651/http://www.materialstoday.com/composite-processing/features/bio-resins-derived-from-cashew-nutshell-oil/|archive-date=10 September 2015|url-status=live}}</ref>  CNSL-based [[novolac]] is another versatile industrial monomer deriving from cardanol typically used as a [[cross-link|reticulating]] agent (hardener) for [[epoxy]] matrices in [[Composite material|composite]] applications<ref>{{Cite journal |last1=da Silva |first1=Kássia Teixeira |last2=Oliveira |first2=Beatriz S. |last3=da Silva |first3=Lucas R. R. |last4=Mattos |first4=Adriano L. A. |last5=Mazzetto |first5=Selma E. |last6=Lomonaco |first6=Diego |date=2023-01-27 |title=<scp>Bio-based</scp> novolac resins from cashew nut processing waste: Alternative resource for the development of <scp>high-value</scp> sustainable products |url=http://dx.doi.org/10.1002/app.53661 |journal=Journal of Applied Polymer Science |volume=140 |issue=13 |doi=10.1002/app.53661 |issn=0021-8995}}</ref> providing good thermal and mechanical properties to the final composite material.<ref>{{Cite journal |last1=Ferri |first1=Enrico |last2=Talentino |first2=Debi |date=May 2011 |title=Bio-resins from cashew nutshell oil |url=http://dx.doi.org/10.1016/s0034-3617(11)70074-1 |journal=Reinforced Plastics |volume=55 |issue=3 |pages=29–31 |doi=10.1016/s0034-3617(11)70074-1 |issn=0034-3617}}</ref>