Polyimides Formulated from a Partially Fluorinated Diamine for Aerospace Tribological Applications

Preliminary tribological studies on new polyimides formulated from the diamine 2,2-bis [4-(4-aminophenoxy)phenyl] hexafluorapane (4-BDAF) indicate that polyimides formulated from this diamine have excellent potential for high-temperature tribological applications. The dianhydrides used to make the polyimides were pyromellitic acid (PMDA) and benzophenonetetracarboxylic acid (BTDA). Friction and wear studies at 25° and 200°C indicate that polyimides formulated using 50 mole percent of the PMDA dianhydride and 50 mole percent of the BTDA dianhydride perform better than polyimides formulated solely with the RTDA dianhydride. Graphite-fiber-reinforced polyimide (GFRPI) composites were formulated with the polyimide made from the BTDA dianhydride, both graphitic and nongraphitic fibers were evaluated. Graphitic fibers produced better tribological results, since thin, flowing, “layerlike” transfer films were produced which did not buildup with long sliding durations. Nongraphitic fibers did not produce this type of transfer.