Amine-quinone polyimides – High temperature polymers that protect iron against corrosion - Polyimides and Other High Temperature Polymers - page 485

Amine-quinone polyimides - High temperature
polymers that protect iron against corrosion
MIJEONG HAN, 1 HUIMIN BIE, 2 DAVID E. NIKLES ∗ ,1 and
GARRY WARREN 2
1 Department of Chemistry and 2 Department of Metallurgical and Materials Engineering and Center
for Materials for Information Technology, The University of Alabama, Tuscaloosa, AL 35487-0209
Abstract—Two dianiline monomers were prepared by the reaction of 1,4-benzoquinone with either
4,4'-methylenedianiline or 4,4'-oxydianiline. These monomers were condensed with either
3,3',4,4'-benzophenonetetracarboxylic dianhydride or 4,4'-(hexafluoroisopropylidene) diphthalic
anhydride to make the corresponding poly(amic acid)s. The poly(amic acid)s were converted to the
polyimides by thermal imidization at 290°C. The amine-quinone polyimides gave free-standing
films with tensile strengths in the range of 90 to 150 MPa and elastic moduli of 0.9 to 1.5 GPa. The
thermal decomposition temperature under nitrogen was 440 to 480°C and the glass transition tem-
perature was in the range of 280 to 310°C. Polyimide coatings on iron were exposed to 0.1 M NaCl
electrolyte and any degradation was followed by electrochemical impedance spectroscopy. A con-
ventional polyimide, made from 4,4'-methylenedianiline and 3,3',4,4'-benzophenonetetracarboxylic
dianhydride, failed after 3 days exposure. The amine-quinone polyimides survived more than one
year of exposure. The adhesion between the amine-quinone polyimide coatings and the iron surface
was so strong that the coatings could not be delaminated by the electrolyte.
Keywords: Polyimides; iron corrosion; coatings; amine-quinone.
1. INTRODUCTION
Polymers containing the 2,5-diamino-1,4-benzoquinone functional group have
been of interest since Erhan and coworkers first reported the synthesis of these
polymers by the condensation of a diamine with 1,4-benzoquinone, Fig. 1, in the
presence of an oxidizing agent [1]. A number of polymers were prepared using ei-
ther aliphatic or aromatic diamines [2]. Depending on the choice of diamine,
polymers could be prepared that were soluble in organic solvents and films could
be cast by solution coating techniques. It was reported that the amine-quinone
polymers would displace moisture from the surface of iron, rendering it hydro-
phobic. This was important, since the rate of iron corrosion greatly increases
when surface moisture is present. Erhan reported that the amine-quinone polymer