Cardanol-modified phenolic resin

Cashew nut shells are a byproduct of cashew nut processing, and they are a source of cashew nut shell liquid (CNSL), a mixture of four potential compounds including anacardic acid, cardanol, cardol, and 2-methyl cardol, which make up around 30%-35% of the shell's weight. Although CNSL was initially considered a waste material, studies have shown that it can be converted into various industrially important chemicals using a range of reactions. Especially, cardanol has a high potential among these components. For example, the phenolic nature of cardanol has been shown to react with formaldehyde to form novolac and resole-type resins, which are commonly used in the production of adhesives, coatings, and molded parts. Additionally, cardanols can be converted into benzoxazine resins, which are a type of phenolic resin and have emerged as an alternative to cardanol-formaldehyde resins due to their design flexibility, and they offer a vast potential for the production of advanced materials. This chapter focuses on the use of cardanol as a renewable source for phenolic resins such as cardanol-formaldehyde and benzoxazines. Accordingly, the syntheses and properties of these resins are reviewed. Moreover, some of the applications have also been shown as examples.