IMIDE OLIGOMERS CONTAINING PENDENT AND TERMINAL PHENYLETHYNYL GROUPS

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 adhesives and composite matrix resins. As a means of controlling the molecular weight between reactiv e sites (i.e. crosslink density), varying amounts of phenylethynyl gro ups were distributed randomly along the imide oligomer whose calculate d number-average molecular weight was 5000 gmol(-1). Upon thermal cure at 350-371 degrees C for 1 h in air, the phenylethynyl group undergoe s a complex reaction resulting in chain extension, branching and cross linking. The products depend upon several factors such as the relative concentration of phenylethynyl groups, molecular mobility of the grow ing polymer and conformational restrictions and have been postulated t o be predominantly highly conjugated polyenes. In general, the cured r esins have a favourable combination of properties including good therm al stability, solvent and moisture resistance and good toughness. The amide acid oligomer solutions were processed into thin films, adhesive tape and carbon fibre prepreg. Neat resin plaques were fabricated fro m imide oligomer powder by compression moulding. The maximum processin g pressure was 1.4MPa and the cure temperature varied from 350-371 deg rees C for 1 h for the composites, adhesive panels and neat resin moul dings. The properties of the cured imide oligomers containing pendent and terminal phenylethynyl groups are compared with those of cured oli gomers of similar composition and molecular weight which contain eithe r terminal or pendent phenylethynyl groups. Published by Elsevier Scie nce Ltd.