Investigation on the effect of castor‐oil based bio‐resins on mechanical, visco‐elastic, and water diffusion properties of flax fiber reinforced epoxy composites

Abstract

Due to the depletion of petro-based sources and environmental consciousness, researchers are striving to replace synthetic fibers and resins in composites with bio-sourced ones without compromising their properties. In this regard, the present study investigates the effect of partially replacing epoxy moieties with castor oil based bio-resins on various properties of epoxy resin and its flax fiber reinforced composite system to achieve sustainable materials, thereby encouraging the bio-based theme. Base-catalyzed transesterification was used to synthesize epoxy methyl ricinoleate (EMR) as a low viscous reactive green monomer derived from epoxidized castor oil (ECO). The influence of both ECO and EMR bio-resin on various mechanical, thermo-mechanical properties, free mode vibration, and water absorption of epoxy and its composites were studied. The composition with 20% of ECO and EMR was optimized based on stiffness-toughness balance. The inclusion of 20% EMR significantly escalated the tensile, impact, and fracture toughness properties of epoxy composites by 6.45%, 12.8%, and 14.2%, respectively. The strong fiber-matrix interface was confirmed by increased pullout adhesion by 21% and 35.1% due to the addition of ECO and EMR, respectively. Dynamic mechanical analyzer revealed a 12% higher storage modulus for EMR modified composites than ECO counterparts. Scanning electron microscope morphology revealed superior interfacial adhesion between fiber and matrix in case of EMR modified bio-composite, which resulted in a lower water diffusion coefficient than ECO modified bio-composite. These results showed that the 20% EMR customized epoxy composite is dimensionally stable with improved mechanical properties and may act as a green alternative to petro-sourced epoxy composites in automotive and semistructural applications.