Effects of Catalyst Content, Anhydride Blending, and Nanofiller Addition on Anhydride-Cured Epoxidized Linseed Oil-Based Thermosets

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.