Development of highly soluble addition-type imide oligomers for matrix of carbon fiber composite (I): Imide oligomers based on asymmetric biphenyltetracarboxylic dianhydride and 9,9-bis(4-aminophenyl)fluorene

Novel highly soluble addition-type imide oligomers were synthesized from 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), 9,9-bis(4-aminophenyl)fluorene (BAFL), 4,4'-diaminodiphenyl ether (4,4'-ODA), and 4-phenylethynylphthalic anhydride (PEPA) to fabricate carbon fiber-reinforced plastics (CFRP) by routing imide solution prepreg. The imide oligomers were soluble in aprotic polar solvents of more than 35 wt.%. Imide oligomers consisting of less than 50 mol% BAFL per total diamine had good processability when using a hot press. The glass transition temperature (T-g) values of the cured resins were higher than 340 degrees C. The T-g values increased when the BAFL component increased. The 5% weight loss temperatures (T-d5) were higher than 550 degrees C. The elongations-at-break of the BAFL copolymers were less than that of the polymer without BAFL. An imide solution prepreg was prepared from the imide oligomer solution and carbon fibers. Polyimide/carbon fiber composite without voids was fabricated from the imide solution prepreg.