STRUCTURE-PROPERTY RELATIONSHIPS IN ADDITION POLYIMIDES .2. RESINS FROM 3-RING AROMATIC DIAMINES CONTAINING CARBONYL AND METHYLENE GROUPS

The use of flexibilized three-ring aromatic diamine moieties was inves tigated in an effort to improve the processing characteristics of addi tion-type polyimide resins. A series of 10 diamines containing carbony l and methylene bridging groups was synthesized. The diamines were pol ymerized with the dimethylester of 3,3',4,4'-benzophenonetetracarboxyl ic acid (BTDE), using the monomethyl ester of nadic acid (NE) as an en dcap. The effect of diamine structure on the solubility and rheologica l properties during cure was determined. The effect of diamine structu re and formulated molecular weight on the thermo-oxidative stability a nd glass transition temperature of the polyimides was also investigate d. Unidirectional laminates were fabricated from selected resins, usin g carbon fibre as the reinforcement. Interlaminar shear strength and f lexural properties of the laminates were determined. The results indic ate that polyimides from some of the diamines containing methylene bri dging groups have potential as matrix resins for long-term application s at temperatures up to 300 degrees C.