Study of Irradiation Effect on Electrical Insulation Material for Superconducting Magnet of Nuclear Fusion Reactor

Cyanate ester (CE) is a polymer material regarded as a candidate for the insulation material of superconducting magnet for nuclear fusion reactor due to its high radiation stability. Therefore, the relationship between the mechanical strength of CE resin and its molecular structure was investigated. Glass fiber reinforced plastic (GFRP) with CE/epoxy resin compound was irradiated up to 10 MGy, and interlaminar shear strength (ILSS) test of the specimens was conducted at liquid nitrogen temperature (LNT). Additionally, IR spectroscopy and dynamic mechanical analysis (DMA) were also conducted to obtain information about changes in crosslink density. When the CE content of GFRPs is more than 40 wt%, the mechanical strength was hardly affected by irradiation up to 10 MGy because of rich triazine rings in their matrix. For the CE 20 wt% GFRP, decrease in the mechanical strength was observed over 5 MGy irradiation. This was partly because such samples contain few triazine rings in the polymer network structure and show low crosslink density.