Renewable Approach To Synthesize Highly Toughened Bioepoxy from Castor Oil Derivative-Epoxy Methyl Ricinoleate and Cured with Biorenewable Phenalkamine

Epoxidation and transesterification of castor oil were carried out to synthesize less viscous epoxy methyl ricinoleate (EMR) and confirmed by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance analysis. Both of the bioresins, epoxidized castor oil (ECO) and EMR, were copolymerized at different compositions (10, 20, and 30 wt %) with diglycidyl ether of bisphenol A (DGEBA)-epoxy resin using biorenewable phenalkamine (PKA) cross-linker for better processability and superior toughening. On incorporation of 20 wt % EMR, the viscosity of epoxy got significantly reduced. The tensile and impact properties showed that the bioepoxy blend with 10 wt % of EMR possesses greater stiffness and strength with higher toughness compared with its ECO counterpart. The increased peak intensity or broadened tan delta curve of bioepoxy blends confirmed higher damping ability. Field-emission-scanning electron microscopy micrographs showed single-phase morphology of epoxy/EMR blends and a phase-separated network of epoxy/ECO blend, which ensured better toughening. Preliminary biodegradability of the epoxy/EMR blend has been studied through vermicompost burial.