An epoxy resin composition for fiber reinforced composite materials comprising components (A) to (E): component (A), an epoxy resin; component (B), a dicyandiamide or a derivative thereof; component (C), a polyisocyanate compound; component (D), a urea compound as represented by formula (1):

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(wherein R.sup.1 and R.sup.2 are each independently H, CH.sub.3, OCH.sub.3, 0C.sub.2H.sub.5, NO.sub.2, halogen, or NHCO NR.sup.3R.sup.4; and R.sup.3 and R.sup.4 are each independently a hydrocarbon group, allyl group, alkoxy group, alkenyl group, aralkyl group, or an alicyclic compound containing both R.sup.3 and R.sup.4, all containing 1 to 8 carbon atoms); and component (E), at least one compound selected from the group consisting of quaternary ammonium salts, phosphonium salts, imidazole compounds, and phosphine compounds.

The molded article includes a fiber-reinforced composite material and a film of a resin composition on a surface of the fiber-reinforced composite material prepared by curing the resin composition, wherein the resin composition includes components [A] to [C]: component [A]: an aliphatic epoxy resin, component [B]: a thiol compound, and component [C]: a quaternary phosphonium salt.

A curable composition includes specific amounts of a ketone, a curable component, and particulate poly(phenylene ether) having a mean particle size of 3 to 12 micrometers and a particle size relative standard deviation of 20 to 60 percent. The composition has a low viscosity that facilitates wetting of reinforcing structures, and composites formed from the composition and a reinforcing structure cure to form a dielectric material with a low dielectric constant and loss tangent.

A thermosetting resin composition for a fiber-reinforced composite material includes a domain of a base resin [A]; and a domain of a curing agent [B] and/or a domain of a catalyst [C], the thermosetting resin composition having a specific gravity of 0.90 to 1.30, and a complex viscosity * determined by dynamic viscoelasticity measurement at 25 C. of 110.sup.7 Pa.Math.s or more.

There is provided a curative system for epoxy resins comprising an alkyl benzene diamine and an additional aromatic amine. There is also provided the use of an alkyl benzene diamine to enhance the performance of an aromatic amine as a curative for an epoxy resin in an infusion processes for the production of fibre reinforced composites; a curable epoxy resin composition containing a mixture of an epoxy resin and a curative system according to the invention; the use of a composition according to the invention as the curable resin in the production of fibre reinforced composites and/or in the production of fibre reinforced composites by infusion processes; a fibre reinforced composite comprising fibrous reinforcement material and a cured epoxy resin obtainable by curing a curable epoxy resin composition according to the invention, and a process for the production of fibre reinforced composites wherein a fibrous reinforcement material is laid up and a curable epoxy resin composition according to the invention is infused through the fibrous reinforcement material at a temperature of 80 to 130 C. and, once the composition has infused the fibrous reinforcement material, the temperature is raised to 150 to 190 C.

Provided is a resin composition that has satisfactory impregnability into reinforcing fibers due to low viscosity and small viscosity increase even in an impregnation process performed for a long time. The resin composition being suitable as a matrix resin for a fiber-reinforced composite material for producing a cured molded article that has toughness and fatigue resistance. The resin composition for a fiber-reinforced composite material includes an epoxy resin, an acid anhydride-based curing agent, an imidazole-based curing accelerator, a radically polymerizable monomer, and a radical polymerization initiator as essential components, has a viscosity at 25 C. that falls within a range of 50 mPa.Math.s to 800 mPa.Math.s as measured by an E-type viscometer, and exhibits a viscosity increase ratio of 200% or less after 8 h at 25 C., wherein 50% by mass or more of the acid anhydride-based curing agent is an alicyclic acid anhydride having no olefinic unsaturated bond.

An object of the present invention is to provide an epoxy resin, an epoxy resin-containing composition, and a cured product which are excellent in flexibility. The present invention relates to an epoxy resin, which is a reaction product of an epoxy compound (A) and an acid-terminated polyester (B). In addition, the present invention relates to an epoxy resin-containing composition and a cured product obtained by using the epoxy resin.

Provided is a fiber-reinforced molding material including as essential materials: a vinyl ester (A) that is a reaction product of an epoxy resin (a1) having an epoxy equivalent in the range of 180 to 500 and (meth)acrylic acid (a2); an unsaturated monomer (B) having a flash point of 100 C. or higher; a polyisocyanate (C); a polymerization initiator (D); and carbon fibers (E) having a fiber length of 2.5 to 50 mm, in which the mass ratio ((A)/(B)) of the vinyl ester (A) to the unsaturated monomer (B) is in the range of 40/60 to 85/15, and the molar ratio (NCO/OH) of isocyanate groups (NCO) in the polyisocyanate (C) to hydroxy groups (OH) in the vinyl ester (A) is in the range of 0.25 to 0.85.

Pre-impregnated composite material (prepreg) that can be cured/molded to form aerospace composite parts that are designed to tolerate hot and wet conditions. The prepreg includes fibers and an uncured resin. The uncured resin includes an epoxy component that is a combination of a trifunctional epoxy resin, a tetra functional epoxy resin and a solid epoxy resin. The resin includes polyethersulfone and a thermoplastic particle component. The uncured resin also includes a curing agent.

A resin composition for a fiber-reinforced composite material that makes it possible to improve productivity by suppressing deformation at the time of removal from a mold, in particular, in the PCM method, while achieving both rapid curing and storage stability. The resin composition for a fiber-reinforced composite material includes an epoxy resin (A) including a phenol novolac epoxy resin and a bisphenol A epoxy resin; a phenoxy resin (B); dicyandiamide (C); an imidazole-based curing aid (D); and a phenol-based curing accelerator (E) as essential components, wherein the phenol novolac epoxy resin of the epoxy resin (A) constitutes 40 parts by mass to 75 parts by mass, the bisphenol A epoxy resin constitutes 10 parts by mass to 35 parts by mass, and the phenoxy resin (B) constitutes 5 parts by mass to 15 parts by mass in the total of 100 parts by mass of the components (A) to (E).