Lignin-Based Bio-Oil Mimic as Biobased Resin for Composite Applications

Lignin is an abundant renewable raw material that has the potential to yield valuable bio-oils consisting of aromatic chemicals when strategically depolymerized. In order to determine if lignin-based bio-oils can be utilized in the development of biobased vinyl ester resins without the need of extensive and costly separations, a methacrylated lignin-based bio-oil mimic (MBO) was generated and utilized as a low viscosity vinyl ester resin (30.3 cP at 25 °C) and as a reactive diluent in a standard commercial vinyl ester resin. MBO was comprised of phenol, guaiacols, and catechols that were methacrylated by esterification with methacrylic anhydride and a catalytic amount of 4-dimethylaminopyridine. Curing the resin produced hard transparent thermosets that possessed near complete conversion of free radical polymerizable groups as per near-infrared spectroscopy. Temperatures of maximum decomposition rate (≥400 °C) and initial decomposition temperatures (≥300 °C) were measured by means of thermo-gravimetric analysis (TGA). Glass transition temperatures ≥115 °C and storage moduli ≥2.5 GPa at 25 °C were measured by dynamic mechanical analysis (DMA). Overall, high-performance lignin-based thermosets were synthesized possessing comparable thermo-gravimetric and thermo-mechanical properties to commercial petroleum- and vinyl ester-based thermosets.