Triple Benefits of Cardanol as Chain Stopper, Flame Retardant and Reactive Diluent for Greener Alkyd Coating

Abstract

Cardanol, a waste from the food industry and widely produced (1 Mt/y), has been used as a chain stopper during the polycondensation of short oil alkyd resins in order to replace benzoic acid. Then, phosphorylated cardanol has been added in order to both reduce solvent content and bring flame-retardant (FR) properties to the alkyd resins. The renewable carbon content of the formulations has been increased up to 23%. The impact of the introduction of phosphorylated cardanol molecules on the drying time and flexibility has been studied as well as the thermal and flame-retardant properties by differential scanning calorimeter, thermogravimetric analysis and pyrolysis-combustion flow calorimeter. The most effective flame-retardant coating that was associated with excellent FR properties and excellent coating properties has been obtained with phosphate-cardanol added at 2%wt of P. Indeed, the film properties were closed to the classical alkyd resin, the solvent content was reduced by 50% and the pHRR decreased by 42% compared to the reference alkyd resin.

Isolation of Cardanol Fractions from Cashew Nutshell Liquid (CNSL): A Sustainable Approach

“…Interestingly, even food, drug, and beverage industries also extensively use CNSL due to its antioxidant properties [42,43] and possible flavoring and mineral oil additive. Low viscosity further enables its use as a reactive diluent [44,45]. Natural CNSL is a complex mixture of phenolic compounds, and depending on the source, it mainly consists of anacardic acid (70%), cardanol (5%), and cardol (18%), and each type has varying degrees of unsaturation at the meta-substituted C 15 -long aliphatic side chain (Figure 1).…”