Cardanol is a phenolic lipid obtained from

anacardic acid Anacardic acids are phenolic lipids, chemical compounds found in the shell of the cashew nut ('' Anacardium occidentale''). An acid form of urushiol, they also cause an allergic skin rash on contact, known as urushiol-induced contact dermatitis. ...

, the main component of cashew nutshell liquid (CNSL), a byproduct of cashew nut processing. Cardanol finds use in the chemical industry in resins, coatings, frictional materials, and

surfactant Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsion#Emulsifiers , ...

s used as pigment dispersants for water-based inks. It is used to make phenalkamines, which are used as curing agents for the durable epoxy coatings used on concrete floors. The name of the substance is derived by contraction from the genus ''

Anacardium ''Anacardium'', the cashews, are a genus of flowering plants in the family Anacardiaceae, native to tropical regions of the Americas. The best known species is '' Anacardium occidentale,'' which is commercially cultivated for its cashew nuts and ...

'', which includes the cashew tree, ''

Anacardium occidentale The cashew tree (''Anacardium occidentale'') is a tropical evergreen tree native to South America in the genus '' Anacardium'' that produces the cashew seed and the cashew apple accessory fruit. The tree can grow as tall as , but the dwarf cu ...

''. The name of the genus itself is based on the Greek word for ''heart''. Friction particles are made by polymerizing the unsaturated side chain of cardanol, followed by cross-polymerization with formaldehyde to yield a cardanol-formaldehyde resin by a process analogous to the formation of phenol-formaldehyde resins such as

Bakelite Polyoxybenzylmethylenglycolanhydride, better known as Bakelite ( ), is a thermosetting phenol formaldehyde resin, formed from a condensation reaction of phenol with formaldehyde. The first plastic made from synthetic components, it was developed ...

. Cardanol-phenol resins were developed in the 1920s by Mortimer T. Harvey, then a student at

Columbia University Columbia University (also known as Columbia, and officially as Columbia University in the City of New York) is a private research university in New York City. Established in 1754 as King's College on the grounds of Trinity Church in Manhatt ...

. These resins found use in vehicle brakes after it was found that they had a coefficient of friction that was less sensitive to temperature changes than phenol-formaldehyde resins. Despite all these uses, only a fraction of the cardanol obtained from cashew nut processing is used in the industrial field. Therefore, there is still interest in developing new applications, such as new polymers. The name ''cardanol'' is used for the

decarboxylated Decarboxylation is a chemical reaction that removes a carboxyl group and releases carbon dioxide (CO2). Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain. The reverse process, which is ...

derivatives obtained by thermal decomposition of any of the naturally occurring anacardic acids. This includes more than one compound because the composition of the

side chain In organic chemistry and biochemistry, a side chain is a chemical group that is attached to a core part of the molecule called the "main chain" or backbone. The side chain is a hydrocarbon branching element of a molecule that is attached to a ...

varies in its degree of unsaturation. Tri-unsaturated cardanol, the major component (41%) is shown below. The remaining cardanol is 34% mono-unsaturated, 22% bi-unsaturated, and 2% saturated. In terms of physical properties, cardanol is comparable to

nonylphenol Nonylphenols are a family of closely related organic compounds composed of phenol bearing a 9 carbon-tail. Nonylphenols can come in numerous structures, all of which may be considered alkylphenols. They are used in manufacturing antioxidants, lubr ...

. Cardanol is hydrophobic and remains flexible and liquid at very low temperatures; its freezing point is below −20 °C, it has a density of 0.930 g/mL, and boils at 225 °C under reduced pressure (10

mmHg A millimetre of mercury is a manometric unit of pressure, formerly defined as the extra pressure generated by a column of mercury one millimetre high, and currently defined as exactly pascals. It is denoted mmHg or mm Hg. Although not an ...

). CAS registry number: 37330-39-5. Recently, it has been demonstrated that cardanol can be used for formation of eco-design of biobased polymeric microcapsules for pesticidal applications with potential to further extended for drugs, self-healing agents, catalysts, etc.Rahul Kishore Hedaoo and Vikas Vitthal Gite, Renewable resource-based polymeric microencapsulation of natural pesticide and its release study: an alternative green approach, RSC Adv., 2014, 4, 18637

References

{{Reflist Phenolic lipids