Cashew nutshell liquid
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Cashew nutshell liquid
The cashew nutshell liquid (CNSL) or cashew shell oil is a natural resin found in the honeycomb structure of the cashew nutshell and is a byproduct of processing Cashew Nuts. Its composition varies depending on how it is processed. Cold, solvent extracted CSNL is mostly composed of anacardic acids (70%), cardol (18%) and cardanol (5%). These substances are dermatogenic, like the oils of the poison ivy, and present danger during manual cashew processing.
It is a raw material of multiple uses in developing drugs, antioxidants, fungicides, etc. It is used in tropical folk medicine and for anti-termite treatment of timber.
Cardolite products are based on cashew nutshell liquid (CNSL), a natural, non-food chain, and annually renewable biomaterial. CNSL is a reddish brown viscous liquid extracted from a soft honeycomb structure inside the cashew nutshell.
This nutshell liquid contains mainly anacardic acid and a smaller amount of cardol and its methyl derivatives. CNSL can be decarboxylated and distilled to yield high purity cardanol, a highly desirable alkylphenolic compounds compound in the coatings and adhesive industries. The distillation residue can be used to produce resilient friction particles and binders for the automotive brake lining industry.
Cardanol is used as a primary building block for Cardolite epoxy curing agents and epoxy diluents and modifiers. This natural alkylphenolic material has an aromatic ring that provides a strong chemical resistant backbone while the hydroxyl group gives strong adhesion and good reactivity for fast and low temperature cure. A long aliphatic side chain provides excellent water resistance, good flexibility, low viscosity, extended pot life, and excellent corrosion protection.
The anacardic acids have been used effectively in vivo against tooth abscesses due to their lethality to a wide range of gram-positive bacteria. Many parts of the plant are used by the Patamona of Guyana medicinally. The bark is scraped and soaked overnight or boiled as an antidiarrheal. Seeds are ground up into powders used for antivenom for snake bites. The nut oil is used topically as an antifungal and for healing cracked heels.
Heating CNSL 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). This process also reduces the degree of thermal polymerization of the un-saturated alkyl-phenols present in cashew shell nut liquid. This natural oil phenol has been found to have interesting chemical structural features which enable a range of chemical modifications to create a wide spectrum of bio-based monomers capitalising on the chemically versatile construct it containing three different functional groups, the aromatic ring, the hydroxyl group and the double bonds in the flanking alkyl chain. These can be split into key groups, there use as Polyols. Which have recently seen a dramatic increase in demand for their bio-based 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 ridged polyurethanes aided by their inherent phenolic structure and larger number of reactive units per unit mass. CNSL based Novolac are another versatile industrial monomer deriving from cardanol typically used as reticulating agents for epoxy matrices in composite applications providing good thermal and mechanical properties to the final composite material. Further examples of applications which are Cashew shell nut liquid derived materials are being evaluated are in the fields of chemical intermediates, additives, stabilizers, lubricants, diesel engine fuel alternatives, poor point dispersants, anti-oxidants, anticorrosive paints. Abrasives and friction dusts have also been developed from Residol, the residue byproduct of this synthesis process.
Shipment / Storage / Risk factors
The raw liquid contains anacardic acid and an organic sulphur compound. It is strong and irritant to skin, eyes and mucous membranes and causes blisters. Most of the liquid used in commerce has
been heated or treated with chemicals to make it safe to handle.
When offered for shipment, it should be certified whether the liquid is raw or has been heated or treated as above. When the raw liquid is offered for shipment, it is a dangerous cargo classification, EmS and MFAG. Tanks not to be used for other commodities than CNSL.