Synthesis of Novel Vanillin‐Amine Hardeners and Its Curing With Magnolol Epoxy Resins to Produce Degradable, Intrinsically Flame‐Retardant Thermoset Resin

ABSTRACT In response to the problem of traditional epoxy resins relying on petroleum‐based raw materials and struggling to balance high performance and sustainability, this paper innovatively designs a fully bio‐based epoxy resin system based on the structure of magnolol biphenyl and the dynamic covalent bond of Schiff base. Firstly, vanillin‐amine curing agent ( VD ) was synthesized by Schiff base reaction using vanillin and 4,4‐diaminodiphenylmethane ( DDM ) as raw materials. Biobased epoxy monomers ( DGEM ) were prepared by the epoxidation reaction of magnolol with excess epichlorohydrin. The fully bio‐based epoxy resin DGEM / VD exhibits high mechanical properties, degradability, and intrinsic flame retardancy. The bending modulus (3391 MPa ) and storage modulus (2542 MPa ) of DGEM / VD were increased by 49.4% and 26.2%, respectively, compared to the petroleum‐based epoxy resin system E44 / DDM , and by 23.8% and 13.7% compared to the semi‐biobased system DGEM / DDM . DGEM / VD epoxy resin exhibits excellent flame retardancy and heat resistance. Compared with E44 / DDM , E44 / VD , and DGEM / DDM , its peak heat release rate decreased by 39.9%, 22.2%, and 12.5%, respectively. Analysis shows that DGEM / VD resin has a synergistic flame retardant mechanism of condensed phase and gas phase. Moreover, VD cured epoxy resin exhibits good degradability in acidic tetrahydrofuran solution. This all bio‐based epoxy resin system achieves a synergistic improvement in flame retardancy, heat resistance, and degradability while maintaining excellent mechanical properties, providing new ideas for the development of environmentally friendly high‐performance epoxy resins.