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

Abstract

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_fs) 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°C showed good meltability at elevated temperatures. The polyimide (PI) neat resins prepared by thermally curing the B-staged oligoimide resins at 370°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°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°C.