Water-based coatings have been in use for decades, as they eliminate or reduce the use of petroleum-based solvents, which increase levels of VOCs, toxic substances and energy consumption. The coatings industry is focusing on four major techniques in the area of eco-friendly technologies: water-soluble, powder, radiation-curable and high-solids coatings.
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In this regard, aqueous, cashew nut shell liquid (CNSL)-based coatings have received increased attention because of the availability of agro-based CNSL.
The CNSL constituents have two reactive units: phenolic OH, which is the hydrophilic part of the molecules, and the long C-15 side chain having an average of two double bonds (i.e., the hydrophobic part that contributes to crosslinking and gives gradual and satisfactory drying and baking properties).
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The long hydrocarbon chain imparts great flexibility to its aldehyde condensate in the various drying oils. CNSL exhibits the following unique properties: agro-based, excellent water resistance, corrosion resistance, satisfactory chemical resistance, better flexibility and drying than other oils, very cheap, sufficient reactive sites.