To reduce the fuel consumption of aircraft launch vehicles, potential weight savings can be achieved through the replacement of the electrical wiring with alternative materials. A large commercial aircraft uses up to 140 miles of copper wiring encased in PVC, weighing a total of 3,500 pounds. Replacement of the copper wiring with a conductive carbon nanotube wire could result in weight savings of up to 50%. Further weight savings as well as reductions in electrical interference in the wiring could be achieved by developing a low density polyimide aerogel coating in place of PVC. Advantages of polyimide aerogel over traditional PVC wire coatings include improved thermal stability, lower density as well as a lower dielectric constant which improves the signal-to-noise ratio of the wiring. The production of a polyimide aerogel wire coating requires the production of a stable pot-life polyimide with sufficient viscosity to ensure uniform coating of the wire followed by a cross-linking step to enhance the strength of the resultant aerogel. The goal of this study is to examine how the addition of various chemical moieties in the polyimide backbone produce gels which demonstrate thermal reversibility from a gel to a viscous liquid and back to a gel once coated on the carbon nanotube wire. Thirty-five separate formulations of polyimide gels were synthesized through combinations of five different diamines and 4 different dianhydrides. Of the thirty-five formulations, 5 showed thermal reversibility, with thermal transitions occurring between 97 °C and 140 °C. The polyimide formulation consisting of 4,4’-oxydianiline-3,3’4,4’-biphenyltetracarboxylic dianhydride-9,9’-bis(4-aminophenyl)fluorene was selected to coat the carbon nanotube yarns due to its low melting temperature, 113 °C, and its sufficiently high viscosity, 2000 cP.

Development of thermally reversible polyimide gels for coating carbon nanotube wires

255th National Meeting (2018)

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