IMIDE OLIGOMERS CONTAINING PENDENT AND TERMINAL PHENYLETHYNYL GROUPS - II

As part of a programme to develop high-performance/high-temperature st ructural resins for aeronautical applications, imide oligomers contain ing pendent and terminal phenylethynyl groups were prepared, character ized and the cured resins evaluated as composite matrices. The oligome rs were prepared at a calculated number-average molecular weight of 50 00 g mol(-1) and contained 15-20 mol% pendent phenylethynyl groups. In previous work. an oligomer containing pendent and terminal phenylethy nyl groups exhibited a high glass transition temperature (similar to 3 13 degrees C), and laminates therefrom exhibited high compressive prop erties, 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 detracti ng from the high glass transition temperature and high compressive pro perties. The amide acid oligomeric solutions were prepared in N-methyl -2-pyrrolidinone and were subsequently processed into imide powder, th in films, adhesive tape and carbon fibre prepreg. Neat resin plaques w ere fabricated from imide powder by compression moulding. The maximum processing pressure was 1.4 MPa and the cure temperature ranged from 3 50 to 371 degrees C for 1 h for the mouldings, adhesives, films and co mposites. The properties of the 1,3-bis(3-aminophenoxy)benzene modifie d cured imide oligomers containing pendent and terminal phenylethynyl groups are compared with those of previously prepared oligomers contai ning pendent and terminal phenylethynyl groups of similar composition and molecular weight.