Toughening of Epoxy Resins by Polyimides Synthesized from Bisanilines

A range of thermoplastic polyimides has been synthesized and used to modify a DGEBA-DDS epoxy thermoset. The influence of polyimide end-group functionality and particle size has been examined. Increases in fracture toughness of up to three times that of the neat resin have been achieved, together with no loss of modulus. Thermal capability is little affected across the range of modifying polyimides. The influence of copoly(imide–imide)s has also been studied. Morphological examination has revealed a range of structures in the blends, including some which are unusual. A particulate toughening mechanism is proposed for one high fracture toughness system.