A sustainable, eugenol-derived epoxy resin with high biobased content, modulus, hardness and low flammability: Synthesis, curing kinetics and structure–property relationship

To develop functional sustainable epoxy resins, we report a novel epoxy resin (DEU-EP) with high net biobased content (70.2 wt%) derived from renewable eugenol. We comparatively study DEU-EP with a commercial bisphenol A epoxy resin (DGEBA) in the presence of a diamine curing agent, 4,4′-diaminodiphenyl methane (DDM). Differential scanning calorimetry reveals that DEU-EP can be sufficiently cured by DDM at a slower rate than DGEBA. By applying an autocatalytic reaction kinetic model we adequately simulate the curing rate of DEU-EP/DDM, and reveal its detailed kinetic mechanisms from model-free isoconversional analysis. Dynamic mechanical analysis shows that DEU-EP/DDM takes the higher storage modulus up to ∼97 °C than does DGEBA/DDM with the glass temperature of 114 °C. Nanoindentation and thermogravimetric analyses demonstrate that compared with DGEBA/DDM, DEU-EP/DDM exhibits a 20%, 6.7% and 111% increase in Young’s modulus, hardness and char yield, respectively. Microscale combustion calorimetry data show that DEU-EP/DDM expresses 55% and 38% lower heat release rate and total heat release than does DGEBA/DDM, respectively. The horizontal burning test approves DEU-EP/DDM can self-extinguish in a short time. Our results demonstrate that the eugenol building blocks and their arrangement greatly affect the cure behaviors of DEU-EP/DDM, and contribute significantly to its enhanced mechanical properties, high-temperature charring ability and chain motions at the glassy state, as well as the reduced flammability. To summarize, DEU-EP exhibits a high promise as a new sustainable epoxy monomer for fabricating high biobased content, high rigid and low flammable epoxy materials.