Amine-quinone polyimide: A new high-temperature polymer and its use to protect iron against corrosion

A new diamine monomer was synthesized by the Michael addition of 4,4'-methy lene dianiline with 1,4-benzoquinone. The monomer was condensed with 3,3',4 ,4'-benzophenone tetracarboxylic dianhydride to give a polyamic acid that w as soluble in NMP. The polyamic acid was cast onto iron and thermally imidi zed to yield the amine-quinone polyimide (AQPI-8). AQPI-8 had a thermal dec omposition temperature of 540 degrees C (10% TGA weight loss in N-2) and a glass transition at 292 degrees C, values typical of polyimides. The degrad ation of the coating on iron after exposure to 0.1 M NaCl electrolyte was f ollowed by electrochemical impedance spectroscopy. Under these conditions a conventional polyimide failed after 3 days exposure, while AQPI-8 survived more than 24 days exposure. The adhesive bond between the amine-quinone po lyimide and the iron surface was so strong that it could not be broken by t he electrolyte. (C) 2000 John Wiley & Sons, Inc.