Imide Oligomers Containing Pendent and Terminal Phenylethynyl Groups—II

As part of a programme to develop high-performance/high-temperature structural resins for aeronautical applications, imide oligomers containing pendent and terminal phenylethynyl groups were prepared, characterized and the cured resins evaluated as composite matrices. The oligomers were prepared at a calculated number-average molecular weight of 5000 g mol−1 and contained 15–20 mol% pendent phenylethynyl groups. In previous work, an oligomer containing pendent and terminal phenylethynyl groups exhibited a high glass transition temperature (∼313 °C), and laminates therefrom exhibited high compressive properties, but processability, fracture toughness, microcrack resistance and damage tolerance were less than desired. In an attempt to improve these deficiencies, modifications in the oligomeric backbone involving the incorporation of 1,3-bis(3-aminophenoxy)benzene were investigated as a means of improving processability and toughness without detracting from the high glass transition temperature and high compressive properties. The amide acid oligomeric solutions were prepared in N-methyl-2-pyrrolidinone and were subsequently processed into imide powder, thin films, adhesive tape and carbon fibre prepreg. Neat resin plaques were fabricated from imide powder by compression moulding. The maximum processing pressure was 1.4 MPa and the cure temperature ranged from 350 to 371 °C for 1 h for the mouldings, adhesives, films and composites. The properties of the 1,3-bis(3-aminophenoxy)benzene modified cured imide oligomers containing pendent and terminal phenylethynyl groups are compared with those of previously prepared oligomers containing pendent and terminal phenylethynyl groups of similar composition and molecular weight.