Fan Lin

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 (Cfs) to give high-quality Cf 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 Cf/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 Cf/PI composite could be long-term served at a temperature as high as 250°C.

Synthesis and Properties of PMR Matrix Resins of Poly(Pyrrolone-Benzimidazole)s

PMR type of poly(pyrrolone-benzimidazole) copolymers (PPBI) were synthesized by the polycondensation of monoethyl ester of cis-5-norbornene-endo-2,3-dicarboxylic acid (NE), diphenyl-isophthalate (DPIP), diethyl ester of 4,4′-oxydiphthalic acid (ODPE) and 3,3′-diaminobenzidine (DAB) or 3,3′,4,4′-tetraamindiphenyl ether(TAD) in a mixing solution of anhydrous ethyl alcohol and N -methylpyrrolidone (NMP) under different temperature and pressure procedures. The resulting resin solution showed an excellent solubility in polar organic solvents and good stability at room temperature, while the corresponding PPBI molded powder and molded plate could be prepared by undergoing amidation, imidization, cyclization and crosslinking reactions when the reaction temperature would be increased from 150 to 350°C, especially, the crosslinking structure formed by the reverse Dials-Alder reaction at 270-290°C under 2.5-3.5 MPa pressure displayed by the pressure meter. The chemical reactions and properties of the resulting PPBI molded powders and molded plates were studied by means of FT-IR, TGA, DMA methods, and the results indicate that the PPBI materials obtained hold excellent thermal stability and processability, the initial decomposition temperature > 600°C and its T g defined by the peak temperature in tan δ curve from the DMA method is 448°C (DAB) or 423°C (TAD) for PPBI-20 molded plate.