Properties of Imide Oligomers Containing Pendent Phenylethynyl Groups

Abstract

As part of a programme to develop high-performance/high-temperature structural resins for aeronautical applications, imide oligomers containing pendent phenylethynyl groups were prepared, characterized, thermally cured and the cured resins evaluated as films, mouldings, adhesives and composites matrices. Initially a diamine containing a pendent phenylethynyl group (3, 5-diamino-4′-phenylethynylbenzophenone) was prepared and characterized. This compound was used to make amide acid and subsequently imide oligomers containing pendent phenylethynyl groups. In order to control the distance between reactive sites, the concentration of pendent phenylethynyl groups was varied randomly along the oligomer backbone. The amide acid oligomers in N-methyl-2-pyrrolidinone were processed into thin films, adhesive tape, carbon fibre prepreg and also converted into imide powder. After initial screening work was performed on unoriented thin films, imidized powders and neat resin mouldings to assess glass transition temperature, mechanical properties (tensile properties and fracture toughness), melt flow behaviour and processability, one particular formulation was scaled up for more comprehensive evaluation. This imide oligomer containing pendent phenylethynyl groups was fabricated into adhesive and composite specimens under 1.4 MPa for1hat 350–371 °C. Excellent mechanical properties were obtained at room temperature and 177 °C. The properties of this material are compared with those of a material of similar composition and molecular weight containing only terminal phenylethynyl groups.