Epoxy resin composition for fiber-reinforced composite material, prepreg and fiber-reinforced composite material

Abstract

Provided are: an epoxy resin composition for fiber-reinforced composite materials, which has a good balance between storage stability and fast curing properties at high levels; a prepreg; and an epoxy resin composition which exhibits excellent mechanical characteristics as a fiber-reinforced composite material. A resin composition which contains an epoxy resin, dicyandiamide, an imidazole compound and an acidic compound, while satisfying the following conditions (a)-(c): (d) The time until the heat flow rate reaches the peak top after the epoxy resin composition reaches 100° C. is 25 minutes or less as measured by a differential scanning calorimeter at an isothermal temperature of 100° C. in a nitrogen gas stream. (e) The time until the heat flow rate reaches the peak top after the epoxy resin composition reaches 60° C. is 15 hours or more as measured by a differential scanning calorimeter at an isothermal temperature of 60° C. in a nitrogen gas stream. (f) The ratio of the number of epoxy groups to the number of imidazole rings in the epoxy resin composition is from 25 to 90 (inclusive).

Dependencies are inferred from the claim text.