Preparation and Characterization of Epoxy Resin Composites With Enhanced Mechanical Properties and Heat Resistance via Blending With Polyimide Oligomer

N , N , N ′, N ′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane (TGDDM) is a glycidylamine epoxy resin with excellent heat resistance and rigidity. However, its inherent high brittleness restricts its application scope. The use of thermoplastic polyimide to toughen EP has several drawbacks, such as increased viscosity and deteriorated dispersibility of composites. To address this issue, an amino‐terminated polyimide oligomer (DBD) was synthesized to toughen TGDDM due to a minimal impact on the viscosity during processing. In addition, the reactive terminal amino groups of DBD can participate in the epoxy curing reaction to form a chemically bonded interface between the oligomer and the matrix and dissipate fracture energy via mechanisms such as crack deflection, thereby enhancing the fracture toughness of the resulting composites. The results demonstrated that, compared with neat EP, the modified epoxy resin TGDDM with 5 wt% of DBD exhibited an increase in impact strength to 7.0 kJ/m 2 and fracture toughness to 0.77 MPa· m 1/2 (representing increases of 40% and 22%, respectively), without sacrificing its thermal and tensile properties. Furthermore, the results of mechanical and thermal characterization were further validated by phase morphology analysis results. This research provides novel insights for the practical application of oligomer‐modified epoxy resins in the electronic and aerospace industries.