Preparation of a self-catalyzed amino-epoxy phthalonitrile resin with a large processing window

To expand the processing window of phthalonitrile resins, a novel self-catalyzed amino-epoxy 4-aminophenoxy phthalonitrile-resorcinol diglycidyl ether phthalonitrile (APRE-PN) resin was prepared via a two-step method of reacting amino and epoxy groups at a low temperature and then reacting nitrile with nitrile groups at a high temperature. The amine-epoxy, epoxy-nitrile, and nitrile-nitrile reactions were confirmed by Fourier-transform infrared spectroscopy and differential scanning calorimetry, and the probable polymerization mechanism was elucidated. The significant decrease in the melting point of the proposed APRE-PN prepolymers dramatically expands the processing window (173 degrees C) for an entire class of phthalonitrile matrices. The APRE-PN resin exhibits excellent thermal stability and dynamic mechanical properties owing to the presence of triazine, phthalocyanine, and oxazoline structures. The improved preparation method provides a new path for the preparation of phthalonitrile resins with large processing windows and new opportunities for the use of this type of thermosetting matrix in manufacturing various composite materials and prepregs.