Modified Natural Eucommia Ulmoides Gum Effectively Improves the Toughness and Strength of Epoxy Resins

Epoxy resins are commonly utilized for their robust strength and high modulus. However, their brittleness is a drawback caused by their elevated cross-linking density, which restricts their suitability for numerous applications. In this study, natural eucommia ulmoides gum (EUG) underwent modification with maleic anhydride (MA) and was used to toughen epoxy resin. The modified EUG contains active sites that effectively participate in the curing process of epoxy resin, resulting in lower cross-linking density. Additionally, during the curing process, EM particles cluster together and form a "sea–island" structure, providing epoxy resin with an additional mechanism for energy dissipation and enhancing its damage resistance. The incorporation of 1% EM results in a 26.5% increase in the fracture toughness and a 40% increase in the elongation at break of epoxy resin. This research offers a validated approach for utilizing biobased materials to reinforce the toughness of epoxy resin.