Renewable Reactive Diluents as Practical Styrene Replacements in Biobased Vinyl Ester Thermosets

A concise series of renewable vinyl compounds has been prepared from benign biosourced precursors, vanillin and eugenol, in fair overall yield. These were evaluated against styrene as reactive diluents in a renewable high-performance vinyl ester resin thermoset: dimethacrylated-epoxidized-sucrose-soyate (DMESS). Each diluent contained a 1,2-dimethoxybenzene or veratrole core structure that connotes a decreased vapor pressure and thereby reduced exposure hazard. Viscosities for formulations (10, 20, and 30% by weight of diluents) with styrene and all three veratrole-diluents were evaluated. Veratrole-diluents were comparable to styrene at similar molar concentration. Thermosets formulated with 30% by weight of diluents were prepared and characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA); the most promising thermoset was prepared using 3-ally1-1,2-dimethoxy-5-vinylbenzene-diluted-DMESS and closely matched the performance of the styrene-diluted thermoset in terms of thermal stability, glass transition temperature, toughness, and tensile strength.