Development of toughened bio‐based epoxy with epoxidized linseed oil as reactive diluent and cured with bio‐renewable crosslinker

In the current work, renewable resourced toughened epoxy blend has been developed using epoxidized linseed oil (ELO) and bio‐based crosslinker. Epoxidation of linseed oil was confirmed through FTIR and 1 H NMR spectra. The ELO bio‐resin was blended at different compositions (10, 20, and 30 phr) with a petroleum‐based epoxy (DGEBA) as reactive diluent to reduce the viscosity for better processibility and cured with cardanol‐derived phenalkamine to overcome the brittleness. The flow behavior of the neat epoxy and modified bio‐epoxy resin blend systems was analyzed by Cross model at low and high shear rates. The tensile and impact behavior studies revealed that the toughened bio‐epoxy blend with 20 to 30 phr of ELO showed moderate stiffness with much higher elongation at break 7% to 13%. Incorporation of higher amount of ELO (20 to 30 phr) increases enthalpy of curing without affecting peak temperature of curing. The thermal degradation behavior of the ELO based blends exhibits similar trend as neat epoxy. The higher intensity or broadened loss tangent curve of bio‐epoxy blends revealed higher damping ability. FE‐SEM analysis showed a rough and rippled surface of bio‐based epoxy blends ensuring effective toughening. Reduced viscosity of resin due to maximum possible incorporation of bio‐resin and use of phenalkamine as curing agent leads to an eco‐friendly toughened epoxy and can be useful for specific coating and structural application.