Epoxy Resin from Renewable Phenols and Furfuraldehyde and Resorcinol: A Sustainable Approach to High Performance Coatings and Adhesives

Abstract

This study presents the augment need for sustainable substitutes for petroleum-based materials by introducing the synthesis of three novel epoxy resins that can be utilize renewable resources. Three resins were synthesized by combining resorcinol and cardanol, hydroquinone and cardanol, catechol and cardanol. Furfuraldehyde was used as the replacement for conventional formaldehyde. Renewable cardanol was incorporated as a partial substitute up to 50% of the phenols to enhance sustainability without compromising performance. Epichlorohydrin was used for further epoxidation to synthesize phenolic resin and achieve the desired functionality. The resins exhibited viscosities in the range of 15,500–16,700 cP, epoxy equivalent weights (EEW) of 600–675 g/eq, and weight-average molecular weights between 2400 and 2680 g/mol, determined by GPC. FTIR demonstrated typical functional groups; the hydrolyzable chlorine content was less than 1.0%, including strong chemical stability. Adhesion tests on metal-to-metal, metal-to-wood, and wood-to-wood substrates yielded lap shear strengths between 25 and 25.60 MPa, respectively. Coatings applied on metal panels showed pencil hardness values of 8–9 H, chemical resistance over 7 days in acidic and alkaline environments, and dry film thickness of 133–135 μm. This work is novel because renewable phenols and furfuraldehyde, along with epichlorohydrin used to develop sustainable tetrafunctional epoxy resin with exceptional mechanical and chemical properties, closing the major gap in sustainable material research and providing an eco-friendly solution for adhesive and coating applications.