Vanillin-based BDBEP enhances the comprehensive performance of trifunctional NNDG epoxy resin

Since less attention has been paid to the modification of trifunctional N, N-diglycidyl-4-glycidyloxyaniline (NNDG) epoxy resins. Initially, the 4, 4′-methylenedianiline (DDM) hardener was used to fabricate NNDG networks, and then, petroleum-based EPDOPO and vanillin-based BDBEP epoxy monomers containing DOPO motifs were developed to modify the NNDG/DDM network. Finally, the resulting resins were investigated on their thermal curing process and comprehensive behaviors. It is found that NNDG/DDM has an activation energy of 52.2 kJ/mol in polymerization reactions, whereas NNDG/EPDOPO/DDM and NNDG/BDBEP/DDM counterparts have activation energies of 48.7 kJ/mol and 55.4 kJ/mol, respectively. All thermosets have good storage moduli (2116.3–2892.5 MPa) and high phase transition temperatures (218.2–208.1 °C). Besides, the epoxy resins demonstrated favorable mechanical characteristics. On average, as to NNDG/BDBEP/DDM, the bending strength and modulus reached 129.83 MPa and 3.43 GPa, respectively, while its tensile strength reached up to 81.49 MPa. Most importantly, compared to EPDOPO, the bio-based BDBEP exhibits superior flame-retardant properties, thereby augmenting the flame-retardancy of NNDG/BDBEP/DDM to meet the UL-94-V0 rating. Therefore, in terms of excellent functionality and sustainability, the NNDG/BDBEP/DDM networks offer good overall performance for potential future applications.