ELECTRON-BEAM-INDUCED CYCLIZATION TO OBTAIN C-FIBER PRECURSORS FROM POLYACRYLONITRILE HOMOPOLYMERS

Alkyl radicals were produced and proved to be present (ESR) in polyacr ylonitrile fibres which had been exposed to electron beams. By giving the irradiated fibres thermal treatment, it was possible to achieve a radical cyclisation of the PAN fibres. The mechanical textile characte ristics of the fibres were determined; they were found to be suitable precursors for carbon fibres. In contrast to conventional cyclisation methods, the convenient high-energy method of irradiation does not nee d any external or internal catalysts (e.g. PAN copolymers), and it lea ds to reduced cyclisation times.