Phenylethynyl-endcapped polymerizable monomer reactants poly(amic ester) resins for high impact-toughened carbon fiber composites

Toughened polymerizable monomer reactants (PMR) poly(amic ester) matrix resins were prepared by the reaction of the diesters of aromatic dianhydrides (3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and/or 2,3',3,4'-biphenyltetracarboxylic dianhydride) and aromatic diamines (the mixture of 3,4'-oxydianiline and 1,3-bis(4-aminophenoxy) benzene) in the presence of monoester of 4-phenylethynyl phthalic anhydride as the end-capping agent using ethanol as solvent. The PMR matrix resins owned the characteristic of high resin concentration and low viscosity, suitable for impregnating carbon fibers (C(f)s) to give high-quality C-f prepreg. The B-staged imide oligomers prepared by thermal baking of the PMR matrix resins at the temperature of <= 240 degrees C showed good meltability at elevated temperatures. The polyimide (PI) neat resins prepared by thermally curing the B-staged oligoimide resins at 370 degrees C showed good combined thermal and mechanical properties. The C-f/PI composite (T300/PI) showed high impact toughness, with compression strength after impact of as high as 260 MPa. Unidirectional laminates had high mechanical properties at room temperature and high strength retention at 250 degrees C, with 97.4% for flexural modulus, 53.3% for flexural strength, and 48.8% for interlaminar shear strength, demonstrating that the high impact-toughened C-f/PI composite could be long-term served at a temperature as high as 250 degrees C.