Epoxy resin compositions for fiber-reinforced composite materials, process for production of the materials and fiber-reinforced composite materials

Abstract

The present invention relates to an epoxy resin composition for fiber reinforced composite material comprising the following components (1)-(3) as essential components, their mixing ratios meeting the following conditions (I)-(IV), and component (3) being dissolved homogeneously: component (1): epoxy resin that is liquid at room temperature, component (2): aromatic polyamine that is liquid at room temperature, component (3): diaminodiphenylsulfone, condition (I): The proportion of component (1) relative to the entire epoxy resin in the composition is 60-100 wt %, condition (II): The sum of the proportions of components (2) and (3) relative to the entire polyamine in the composition is 70-100 wt %, condition (III): The proportion of component (3) relative to the entire polyamine in the composition is 25-60 wt %, and condition (IV): The stoichiometric ratio of the entire polyamine to the entire epoxy resin in the composition is 0.7-1.3. Another embodiment of the invention relates to an epoxy resin composition for fiber reinforced composite material that contains at least the following components (4)-(6), forms a cured product with a theoretical molecular weight between crosslinking points in the range of 250-350 g / mol, and has an initial viscosity at 80° C. of 1-500 MPa.s: (4): aromatic epoxy resin with tri- or higher functionality, (5): aromatic epoxy resin with di- or higher and lower than tri-functionality, and (6): aromatic polyamine, the molecular weight between crosslinking points being defined as the weight of the entire cured epoxy resin divided by the number of crosslinking points contained in the entire cured epoxy resin. The invention also relates to an epoxy resin composition for fiber reinforced composite material that consists of the following components (7) and (8): (7) a polyglycidyl ether of phenol aralkyl resin as represented by the following formula: where R<1>, R<2>, R<3 >and R<4>denote a hydrogen atom, an alkyl group having 1-8 carbon atoms, or a halogen atom, and m and n denote an integer of 1-4 and a real number of 0 or more and less than 1, respectively, and (8) polyamine. With the constitution described above, the present invention can provide a liquid epoxy resin composition for low cost production of high performance fiber reinforced composite material, that has a low viscosity at relatively low temperatures, and that after being cured, the cured product is high in glass transition temperature, elastic modulus and toughness while being small in the glass temperature decrease caused by water absorption and also small in the coefficient of linear expansion; and can provide a method to produce fiber reinforced composite material therefrom. Fiber reinforced composite material produced according to the present invention can serve as material for parts of aircraft, including main wing, tail, rotor blade, fairing, cowl, and door; parts of spacecraft, including motor case and main wing; and parts of space satellite body structure. They can also be used preferably as material for automobile chassis and railroad vehicle body structure.

Description

[0001] The present invention relates to an epoxy resin composition that is useful for production, by resin transfer molding (RTM) in particular, of high performance fiber reinforced composite material, and also relates to a molding method that uses said resin composition.[0002] Fiber reinforced composite materials that consist of reinforcing fiber, such as glass fiber, carbon fiber and aramid fiber, and matrix resin, such as unsaturated polyester resin, vinyl ester resin, epoxy resin, phenol resin, cyanate ester resin and bismaleimide resin, are lightweight but high in strength, rigidity, shock resistance, fatigue resistance and other mechanical properties, in addition to being high in corrosion resistance, and accordingly have been used in aircraft, spacecraft, automobiles, railroad vehicles, ships, construction material, sporting goods, and many other materials in different fields. In particular, fiber reinforced composite materials composed of continuous fiber are generally used ...

AI Technical Summary

Benefits of technology

[0015] The purpose of the present invention is to provide a liquid epoxy resin composition for low cost production of high performance fiber reinforced composite material, that has a low viscosity at relatively low temperatures, and that after being cured, the cured product is high in glass transition temperature, elastic modulus and toughness while being small in the glass temperature decrease caused by water absorption and also small in the coefficient of linear expansion; and to provide a method to produce fiber reinforced composite material therefrom.

Problems solved by technology

This process, however, cannot be said to be excellent in terms of cost because it requires production of prepregs as intermediate.

A variety of thermosetting resins have been applied to RTM, but in particular, epoxy resin and bismaleimide resin are widely used in the field of aircraft manufacturing where high performance materials are essential, with particular importance attached to epoxy resin because of its high cost performance.

Since aromatic polyamines are relatively low in reactivity, compositions that consist of epoxy resin and aromatic polyamine can be stored for a relatively long period of time.

Above the glass transition temperature, the rigidity of cured resin decreases greatly, resulting in deterioration of mechanical properties of the fiber reinforced composite material.

To use such a high curing temperature of about 180.degree. C., however, molds and other tools have to be resistant to such heat, which increases the required costs.

The reactivity of epoxy resin and aromatic polyamine is relatively low, and cuing at a low temperature will require a longer cure time.

However, since diaminodiphenyl sulfones are solid with a high melting point, they are not used in two parts type epoxy resin composition products.

It is not impossible in theory to design a batch comprising a solid hardener, but this is not practical because a continuous mixer cannot be applied.

Thus, difficulty of using high-performance components has been a major problem with conventional two parts type epoxy resin composition products.

Another serious problem with conventional epoxy resin composition products for RTM is trade-off between low viscosity and good properties of cured products.

Conventional epoxy resin composition products for RTM that can provide cured products with good properties, however, are generally high in viscosity and have to be injected at a high temperature, and therefore, they are not suitable for VaRTM and other low cost processes for which low temperature injection is preferred.

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