Rheological Studies of High-Performance Bioepoxies for Use in Fiber-Reinforced Composite Resin Infusion

A new approach is presented to quantify the processability of high-performance biobased epoxy formulations via vacuum-assisted resin transfer molding (VARTM). Epoxidized linseed oil (ELO) is cured with two anhydride hardeners, nadic methyl anhydride and methyltetrahydrophthalic anhydride (NMA, MTHPA), and two catalysts, 1,8-diazabicyclo[5.4.0]-undec-7-ene and 2-ethyl-4-methylimidazole (DBU, 2E4MI). As neither gel times nor the viscosity time curves reported vs temperature are sufficient to assess processability, we integrate fluidity time curves to generate a useful numerical metric for the infusibility of a given resin formulation and report the variation of integrated fluidity with temperature. A conventional high-performance anhydride-cured epoxy serves as a control. ELO-NMA-DBU and ELO-MTHPA-2E4MI show significantly greater infusability vs the control at T <= 120 degrees C. ELO-MTHPA-DBU shows greater infusability at T <= 80 degrees C, and ELO-NMA-2E4MI shows greater infusability, in general. These attractive characteristics highlight the potential of bioepoxies as the basis for more sustainable fiber composites.