Cashew Nut Shell Liquid CNSL

Bond type Covalent Ionic, hydrophobic, hydrogen bond, metal-ligand coordination 

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Cardanol, a main component obtained by thermal treatment of cashew nut shell liquid (CNSL), is a phenol derivative having mainly the meta substituent of a C15 unsaturated hydrocarbon chain with one to three double bonds as the major. Since CNSL is nearly one-third of the total nut weight, a great amount of CNSL is obtained as byproducts from mechanical processes for the edible use of the cashew kernel. Only a small part of cardanol obtained in the production of cashew kernel is used in industrial fields, though it has various potential industrial utilizations such as resins, friction-lining materials, and surface coatings. Therefore, development of new applications for cardanol is very attractive. 

Synthesis Epoxy resins consisting ofglycidyl ether, ester and amines are generally prepared by the condensation reaction between diol, dibasic acid or amine and epichlorohydrin in the presence of sodium hydroxide with the elimination of hydrochloric acid. The commercially available epoxy resins are, however, made by the reaction of epichlorohydrin and bisphenol-A. Cashew nut shell liquid (CNSL)-based novolac epoxy resins have also been reported [342]. 

Cashew nut shell liquid (CNSL) is the exudate from the cashew nut shell. It is mainly phenolic in nature. Industrially used for making polymeric resins etc. A bath of the CNSL is traditionally used for heating the whole nuts with shells. 

This is one of the most widely distributed plants cultivated to obtain cashew nut. The phenolic lipid is only a by-product known as cashew nut shell liquid (CNSL). The nut, attached to the base of the cashew nut apple consists of an ivory-colored kernel covered by a thin brown membrane (testa) and enclosed by an outer porous shell, the mesocarp which is about 3 mm thick with a honey-comb structure where the reddish brown liquid (CNSL) is stored [91]. The major components of CNSL are a phenolic acid, anacardic acid, a dihydric phenol, cardol with traces of mono hydric phenol, cardanol, and 2-methyl cardol [92-95]. 

AR occur in cashew nut shells as a fraction of other oil components like cardols, cardanols and anacardic acid. A comparative study on the extraction of cashew nut shell liquid (CNSL) was presented by Shobha and Ravindranath (50). The study involved the extraction of the cashew nut shell by supercritical CO2 or pentane. The pentane extraction was carried out on 50g steamed or fresh cashew nut shells in lOOmL solvent. Supercritical CO2 extraction was performed on 300g freshly broken cashew nut shells at 25 MPa and 40 C with the CO2 flow kept at 4-5Kg/h for 17,5h with extract collection every 2.5h. The resorcinolic lipid fraction obtained by supercritical CO2 represented 82% of the equivalent obtained by pentane extraction of fresh cashew nut shells and 70% of the extraction of steamed material. Despite this appreciable variation on the ratio of the total cardols and cardanols from one mediod to other, the relative proportion of the enomers in each group was very similar (50). Generally, the extraction yield obtained by supercritical CO2 was lower (= 60%) than that obtained by the classical solvent extraction methods (50), however, the product was nearly colorless. One of the major problems in the industrial application of CNSL is the very dark brown color of the solvent extracted product. 

The phenolic lipids of Anacardieum occidentale have been commercially exploited (ref. 174) and those in Rhus vernicifera to a lesser extent. Most of the technical cashew nut shell liquid (CNSL) which results from industrial processing is and has been employed as a phenolic source for formaldehyde polymerisation the products from which in compounded form have been the basis for friction dusts widely used throughout the world in vehicle brake and clutch linings (ref.175). Urushiol has had use over many centuries in the art of Japanese lacquering (ref. 176) and in more recent years has been sometimes supplemented with CNSL. Chemical uses are referred to later. 

Cashew (Anacardium occidentale L.) is a tropical evergreen plant known for its seeds that are consumed worldwide. It is one of the most economically important genera in the Anacardiaceae family and is presently cultivated in many regions of the world [ 1 ]. World production of cashew nut is about 2.8 million tons in 2005. Vietnam, Nigeria, and India are the major cashew nut producers, with 33.5%, 20.7% and 19.0%, respectively, of world production of cashew nut [2]. The cashew industry ranks third in the world production of edible nnts [3]. Cashew tree produces several products. Cashew nut is the seed of cashew. There is no donbt that the nut is the most important product of the cashew tree. It is consumed whole, roasted, sheUed, and salted. Its fruit, also called as cashew apple, may be eaten raw, preserved as jam, made into a beverage, or fermented into a wine [4]. Cashew nnt shell oil, also known as cashew nut shell liquid (CNSL), is extracted from the honey-combed shell of the cashew nut and has been used in several industrial applications. 

For instance cardanol, a phenol-based by-product of the cashew nut industry, is one of the common precursors used to obtain different types of epoxy bio-based resins. Cardanol is an industrial grade yellow oil obtained by vacuum distillation of cashew nut shell liquid (CNSL), the international name for the alkyl phenolic oil contained in the spongy mesocarp of the cashew nut shell from the cashew tree Anacardium occidentale L. CNSL derived from the most diffused roasted mechanical processes of the cashew industry represents nearly 25% of the total nut weight, and its production worldwide (Africa, Asia and South America being the main producer areas) is estimated to be about 300,000 tons per year (Calo et al., 2007). 

Another important group of phenolic resins are those derived from cardanol, a substituted phenol obtained from a naturai material, cashew nut shell liquid (CNSL). CNSL has a polyunsaturated Cjj alkyl chain substituted at the m-position of phenoi. The phenolic resins derived from cashew nut shell liquid have oxidative curing properties. Despite their dark color, they are very popular binders for anticorrosive air-drying primers. 

Souza et al. examined the influence of plasticizers, such as dioctyl phthalate (DOP) and cashew nut shell liquid (CNSL), on the electrical properties of blends based on PANI (doped with dodecylbenzene sulfonic acid) and SBS (styrene-butadiene-styrene) copolymer [106,107]. EPR experiments revealed an increase in polaron mobility (a decrease of AHpp) as the amount of plasticizer in the blend was increased, with the effect being more pronounced for CNSL (Figure 23.25). This phenomenon is known as a second doping, and is achieved without any additional protonation of PANI rather, it is due to an enhanced conformational... 

Cardanol is a main component of thermally treated cashew nut shell liquid (CNSL), and is a phenolic compound with a long unsaturated hydrocarbon chain substituted in the meta position (Figure 2.17a). Urushiol, which is obtained from lacquer tree, poison ivy, poison oak, and poison sumac (Toxicodendron), and used for a raw material of a lacquer (urushi) in East Asia, is also a phenolic compound of catechol with a long unsaturated or saturated hydrocarbon chain (Figure 2.17b). Cardanol-based polymers have been reported very often, while there are a few research reports on urushiol-based polymers. Research on polymers synthesized from cardanol or CNSL are reviewed elsewhere.In the late 1980s, cardanol or CNSL-based polymers began to be reported as novel phenol-formaldehyde type resins and novel epoxy resins.Thereafter, Pillai and his co-workers have vigorously studied synthesis of various type of cardanol-based polymers polymers obtained... 

Resins. The phenolic resins used are varied. They are novolak, resole, novolak/resole combinations, cresol resins, and rubber-modified and oil-modified novolaks. Tung oil, cashew nut shell liquid (CNSL), linseed oil, and soya bean oil are reacted with phenolics. The value of oil-modified phenolics is the quieter performance of the braking action, and the reduction of cracking in components. Oil-modified novolak resins are supplied in viscous liquid or powdered forms. The flexibility in the cured resin can be controlled by the percentage and type of oil introduced into the resin. 

Mahanwar P.A., and Kale D.D. (1996) Effect of Cashew Nut Shell Liquid (CNSL) on Properties of Phenolic Resins J.ApplPolym.Sci., 61, 2107-2111. 

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