Making alkyd greener: Modified cardanol as bio-based reactive diluents for alkyd coating

With the increase in demand for bio-based coatings with lower volatile organic compound (VOC) emissions, methacrylated cardanol (MACO) and triethoxysilane-functionalized cardanol (TSCO) have been investigated as bio-based reactive diluents for formulating alkyd coatings as a substitute for volatile solvents. The viscosity of the representative alkyd resin was significantly reduced through the use of cardanol-based reactive diluents (over 84% diluent efficiency at 30 wt% loading). Both MACO and TSCO were able to participate in the cross-linked network of the alkyd coating as confirmed by the gel content and cross-link density of the cured coating films. Moreover, the cross-link density of the alkyd coating was significantly improved by using TSCO as the reactive diluent, leading to a significant enhancement in mechanical strength and solvent resistance of the alkyd coating. This work will facilitate the adoption of cardanol as a renewable building block in the coating industry in order to produce greener alkyd coatings.