Gallic acid ester-based flexible UV-shielding epoxy thermosets with tunable properties

Epoxy thermosets are usually limited by their inherent brittleness and low-impact resistance. Henceforth, a series of bio-based epoxy resins were synthesized from gallic acid (GA) esters. Varying the chain length of flexible poly(ethylene glycol) (PEG) enabled tailoring the thermomechanical properties of the thermosets. Decreasing the chain length of the epoxy prepolymer, resulted in the increase of tensile strength from 2.89 to 15.18 MPa with a decrease in elongation from 121.7 to 16.91% and an increase in viscosity of the epoxy resins from 5.25 to 228.46 Pa.s. The low viscosity of epoxy resins with longer chain lengths offers good processability and broadens their relevance as reactive diluents for resins of high viscosity. Additionally, the thermosets exhibited decent transparency and UV shielding ability with satisfactory biodegradable attributes. The study revealed a direct correlation between chain length and thermomechanical properties of the epoxy thermosets.