Fully bio-based epoxy resins from the condensation of vanillin and piceol derivatives

A series of unsymmetric bio-based epoxy monomers were synthesized using lignin-derived monophenols (vanillin and syringaldehyde) and methyl ketone (piceol, zingiberone, and raspberry ketone). The obtained bisphenols are analog of retrochalcone (echinatin), which is isolated from the root of liquorice. The structure of lignin-based epoxy monomers and the obtained epoxy thermosets was confirmed by nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy. The curing behavior of the epoxy thermosets was determined by differential scanning calorimetry (DSC) at different ramp rates (5°C/min, 10°C/min, 15°C/min, and 20°C/min). The activation energy of the bio-based epoxy resins was from 50.59 KJ mol −1 to 61.36 KJ mol −1 according to Kissinger equation. The glass transition ( T g ) of the obtained epoxy thermosets was higher than that of DGEBA-based resins (74.8°C vs 61.9°C) based on dynamic mechanical analysis (DMA). Thermomechanical properties of the corresponding thermosets were conducted on thermogravimetric analysis (TGA) and tensile test (TA). They exhibited comparable thermal stability with that of DGEBA based resins.