fusible polyimide powders are prepared by the process of this invention . an amic acid amine is first prepared by treating moles of a bismethane with n mole of aromatic tetracarboxylic anhdride to produce an aromatic amic acid prepolymer . this prepolymer is then mixed with an unsaturated carbocyclic monoanhydride and the mixture heated to form a reactive end - capped polyamic acid precursor . the resulting composition is thermally treated in order to partially imidize the precursor . the resulting fusible polyimide powder is finally separated .