SYNTHESIS AND THERMOOXIDATIVE STABILITY OF 2,2,2-TRIFLUORO-1-PHENYLETHYLIDENE)BISPHTHALIMIDE] AND OTHER FLUORINATED POLYIMIDES

The synthesis of a novel polyimide (3F-PDA) derived from 4,4'- (2,2,2- trifluoro-1-phenylethylidene]bisphthalic acid anhydride or its diethyl ester and p-phenylene diamine is described. This material shows uniqu e thermooxidative stability compared with commercially available state -of-the-art polyimides. The optimum monomer stoichiometric ratios of d iester to diamine to form a stable 3F-PDA polyimide were investigated. The studies revealed that diester/diamine ratios greater than 1.000 e xhibited the greatest resistance to thermooxidative stability at 371-d egrees-C in 1 atm of circulating air and at 371-degrees-C in 4 atm of flowing air.