A prepreg containing the following constituent elements [A] to [C], wherein a resin composition containing the constituent elements [B] and [C] has a higher-order structure derived from a diffraction angle 2θ between 1.0° and 6.0° observed with X-ray diffraction after curing: [A]: carbon fibers [B]: epoxy resin [C]: curing agent of [B].

A prepreg containing the following constituent elements [A] to [C], wherein a resin composition containing the constituent elements [B] and [C] has a higher-order structure derived from a diffraction angle 2θ between 1.0° and 6.0° observed with X-ray diffraction after curing: [A]: carbon fibers [B]: epoxy resin [C]: curing agent of [B].

One purpose of the present invention is to provide an epoxy resin composition which is for obtaining a fiber-reinforced composite material that combines heat resistance with tensile strength on a high level. The other purpose is to provide: a fiber-reinforced composite material obtained using this epoxy resin composition; and a molded article and a pressure vessel both containing the fiber-reinforced composite material. The present invention has the following configuration in order to achieve the above purposes. Namely, the epoxy resin composition includes the constituent element [A]: An epoxy resin including an aromatic ring and having a functionality of 2 or higher and the following constituent element [B]: An acid anhydride-based hardener, and is characterized in that a cured object obtained by curing the epoxy resin composition has a rubber-state modulus of 10 MPa or less when evaluated for dynamic viscoelasticity and the cured object has a glass transition temperature of 95° C. or higher.

One purpose of the present invention is to provide an epoxy resin composition which is for obtaining a fiber-reinforced composite material that combines heat resistance with tensile strength on a high level. The other purpose is to provide: a fiber-reinforced composite material obtained using this epoxy resin composition; and a molded article and a pressure vessel both containing the fiber-reinforced composite material. The present invention has the following configuration in order to achieve the above purposes. Namely, the epoxy resin composition includes the constituent element [A]: An epoxy resin including an aromatic ring and having a functionality of 2 or higher and the following constituent element [B]: An acid anhydride-based hardener, and is characterized in that a cured object obtained by curing the epoxy resin composition has a rubber-state modulus of 10 MPa or less when evaluated for dynamic viscoelasticity and the cured object has a glass transition temperature of 95° C. or higher.

The present invention is directed to a two component (2K) composition comprising: (A) a first component comprising: a) at least one elastomer modified epoxy resin; b) at least one internally flexibilized epoxy resin which is characterized by a Shore D hardness, as measured with a durometer in accordance with ASTM D2240, of ≤45 when cured with diethylene triamine; c) at least one chelate modified epoxy resin; and d) optionally at least one epoxy resin different from said resins a) to c); and, (B) a second component comprising: e) a curative which consists of at least one compound possessing at least two epoxide reactive groups per molecule, said curative being characterized by comprising at least one Mannich base.

The present invention is directed to a two component (2K) composition comprising: (A) a first component comprising: a) at least one elastomer modified epoxy resin; b) at least one internally flexibilized epoxy resin which is characterized by a Shore D hardness, as measured with a durometer in accordance with ASTM D2240, of ≤45 when cured with diethylene triamine; c) at least one chelate modified epoxy resin; and d) optionally at least one epoxy resin different from said resins a) to c); and, (B) a second component comprising: e) a curative which consists of at least one compound possessing at least two epoxide reactive groups per molecule, said curative being characterized by comprising at least one Mannich base.

A resin composition including (A) an epoxy resin, (B) a curing agent, and (C) an inorganic filler, in which a chloride ion content included in the resin composition measured in accordance with a sample combustion ion chromatography method (BS EN 14532 2007) is 50 ppm or less.

A resin composition including (A) an epoxy resin, (B) a curing agent, and (C) an inorganic filler, in which a chloride ion content included in the resin composition measured in accordance with a sample combustion ion chromatography method (BS EN 14532 2007) is 50 ppm or less.

A thermoset precursor composition includes a backbone comprising an imine bond bonding at least one of: 1) aromatic compounds together, or 2) bonding an aromatic compound to an aliphatic chain, and at least one of: an epoxy group terminating the backbone or an aldehyde group terminating the backbone. The thermoset precursor can have at least two epoxy groups, one epoxy group and one aldehyde group, or two aldehyde groups.

A thermoset precursor composition includes a backbone comprising an imine bond bonding at least one of: 1) aromatic compounds together, or 2) bonding an aromatic compound to an aliphatic chain, and at least one of: an epoxy group terminating the backbone or an aldehyde group terminating the backbone. The thermoset precursor can have at least two epoxy groups, one epoxy group and one aldehyde group, or two aldehyde groups.