Chemistry and properties of a phenylethynyl-terminated imide blend

As part of an effort to develop a low-volatile, essentially dry, carbon fiber tape from a phenylethynyl-terminated imide for use in heated head automated tow placement, a 70:30 blend of LaRCTM PETI-5 and LaRCTM PETI-IAX was prepared in N-methyl-2-pyrrolidinone by mixing the phenylethynyl-terminated amide acid solutions together. Solutions of the amide acids and the blend were characterized by size exclusion,chromatography after aging at room temperature and at 5degreesC over a 30-day period. Thin films were periodically cast from the solutions, thermally cured, and the tensile properties determined. Unoriented thin-film tensile properties were unaffected by aging conditions over the 30-day period whereas the weight average molecular weights of the phenylethynyl-terminated amide acids decreased. Imide oligomers were prepared from the amide acids, characterized, and thermally cured. A low-volatile tape prepared from prepreg of the 70:30 blend was fabricated into composites by processing in a vacuum press. The thin-film tensile and composite properties of the blend generally followed a rule of mixtures.