A number of polymer films were evaluated to determine thefeasibility of a >200° C AC and DC capacitor dielectric. Smallsamples of film were checked for their dielectric properties,particularly dissipation-factor-temperature relations between 150° Cand 300° C, electric strength, thermal and hydrolytic stability, andpotential to be produced in large quantities in thin gauges. A 3Mproprietary experimental film, FPE, was found to be the most promisingwith low dissipation factors between 150° C and 275° C. Thecriterion for the high temperature usability of this film was itsperformance in 0.4-μF to 1-μF capacitors as a film-film-foil andmetallized film winding. The quality and production of FPE film wereupgraded for the capacitor application. This was based on capacitorproducibility from FPE film rolls and high temperature life tests underDC and 400 Hz AC stresses, and film producibility and tests. Capacitorfailures were of the dielectric puncture type, apparently due to defectswhich could be minimized. A group of 0.5-μF capacitors was made foroperation in a NASA power circuit at 20 kHz and 200° C. The 10-kHz to100-kHz, dissipation factors of FPE film were very low at 175° C to300° C, and were found to be very stable under these conditions ofoperation
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