Soluble Polyimide‐Modified Epoxy Resin With Enhanced Comprehensive Performances

ABSTRACT This research is dedicated to improving the mechanical properties and thermal stability of epoxy resin modified with polyimide. Two types of imides, along with soluble polyimides incorporating trifluoromethyl and tert‐butyl groups, were synthesized as modifiers for epoxy resins. We investigated the effects of imide units with varying structures and soluble polyimides on the mechanical, thermal, and dielectric properties of epoxy resins. The six‐membered imide ring demonstrated enhanced thermal stability compared to its five‐membered counterpart. The modified epoxy resins exhibited a substantial improvement in mechanical properties, with elongation at break increasing from 6.5% to 11.33%, compared to unmodified ones. SEM images of the fracture surfaces of the modified epoxy resins showed distinct fracture features, which indicated enhanced toughness as a result of the incorporation of imide units. These modified resins also demonstrated excellent thermal stability (with a char yield of 31.5% at 800°C), low hydrophilicity (water absorption ranging from 0.69% to 1.54%, and contact angles between 72° and 85°), and superior dielectric properties (the dielectric constant decreased by 1.95 at 10 3 Hz, while the volume resistivity increased by two orders of magnitude). This research provides new insights into the application of epoxy resins in the aerospace and advanced electronic materials fields.