Tannic acid-based tough hyperbranched epoxy thermoset as an advanced environmentally sustainable high-performing material

Abstract

Bio-based resources are progressively replacing those of petroleum-based to address the detrimental impact on environment and health issues. In this regard, hyperbranched epoxy resins with three different compositions were synthesized by simple polycondensation reaction of bio-based branching reactant, diethanolamide of gallic acid with bisphenol-A, and epichlorohydrin. Diethanolamide of gallic acid was obtained from the reaction between tannic acid and diethanol amine in the presence of sodium methoxide catalyst. FTIR, 1H NMR, and 13C NMR spectroscopic analyses were employed to confirm the structure of branching unit and hyperbranched resins. Poly(amido amine)-cured hyperbranched epoxy thermosets exhibited superior properties, such as tensile strength (45–57.2 against 38.5 MPa), elongation-at-break (16.3–24.2 against 5 %), scratch hardness (>10 against 7 kg), toughness (577.8–859.1 against 150.2 MPa), tensile adhesive strength (1647–2086 against 581 MPa), and biodegradability (17.6–31 against 2.2 %), compared with the conventional bisphenol-A-based epoxy, prepared under the same conditions. These results simply indicate the advantageous of the bio-based moiety and hyperbranched architecture on the overall performance of the thermosets. Moreover, good antioxidative response of these thermosets expands their applications as protective coatings and adhesive materials. Thus, diethanolamide of gallic acid-based hyperbranched epoxy thermoset can be used as potent ecofriendly advanced material in multifaceted applications.