A series of formulations based on epoxidized linseed oil, ELO cured with various anhydride hardeners, were investigated to assess the potential for enhanced elastic properties and thermal transitions through variations in catalyst concentration (1,8-diazabicyclo[5.4.0]­undec-7-ene, DBU), hardener type (nadic methyl anhydride, NMA, methyltetrahydrophthalic anhydride, MTHPA, and their blends with phthalic anhydride, PA), and nanofiller (organically modified hydrotalcite, Perkalite F100S) content. To facilitate rapid screening, Shore D hardness was used as a proxy for Young’s modulus, and the limits of this approach were tested via comparisons with modulus measurements made via dynamic mechanical analysis (DMA). ELO cured with MTHPA at a 1:1 epoxy/anhydride molar ratio with 4.5 phr DBU gave a particularly attractive combination of rigidity, homogeneity, and alpha transition temperature rarely seen in thermosets composed of a 100% biobased epoxy component. Nanocomposite formation provided a modest increase in modulus with no change in thermal transitions.

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 °C. ELO-MTHPA-DBU shows greater infusability at T ≤ 80 °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.

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