JPH08156115A - Carbon fiber reinforced composite material - Google Patents

Abstract

PURPOSE: To provide a carbon fiber reinforced composite material which develops high dynamical characteristics by using a carbon fiber in which PAN (polyacrylonitrile) series precursor is taken as a raw material. CONSTITUTION: An epoxy resin as a base resin, an acid anhydride as a hardening agent, and am imidazole catalyst as a catalytic hardener are used. An epoxy resin composition to which 0.1-3 pts.wt. of polymeric surface active agent having a carboxyl group as an additive is added, is used as a matrix resin. A carbon fiber taking a polyacrylonitrile series precursor as a raw material, is used as a reinforced fiber. Thus, a carbon fiber reinforced composite material is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a carbon fiber reinforced composite material in which carbon fibers made of a polyacrylonitrile (hereinafter abbreviated as PAN) precursor are used as reinforcing fibers.

[0002]

2. Description of the Related Art Carbon fiber reinforced composite materials are produced and sold as products for aerospace applications, sports and leisure applications due to their excellent mechanical properties. Therefore, a matrix resin that exhibits high mechanical properties when formed into a carbon fiber reinforced composite material is required.

The matrix resin is required to exhibit high mechanical properties when it is made into a composite material with carbon fiber and graphite fiber (hereinafter collectively referred to as carbon fiber), and not only the performance of the matrix resin itself but also the carbon fiber. It must have high adhesive strength with and impregnation with carbon fiber tow. That is, the mechanical properties of the carbon fiber reinforced composite material such as the bending strength and the bending elastic modulus can be improved by increasing the impregnation property of the matrix resin into the carbon fiber tow or by increasing the adhesive strength between the matrix resin and the carbon fiber.

Generally, the adhesion between the carbon fiber and the matrix resin is poor, and even a carbon fiber reinforced composite material with an epoxy resin, which is said to have a high adhesion strength with the carbon fiber, causes the carbon fiber-matrix resin interface to break down at a rate-determining rate and obtains sufficient strength. Often not. At present, the improvement of the adhesive strength between the carbon fiber and the matrix resin usually depends on the surface modification of the carbon fiber such as the electric field treatment or the size treatment of the surface of the carbon fiber.

Regarding the adhesion between the carbon fiber and the matrix resin, it has been proposed to change the surface treatment of the carbon fiber and the size. However, since the sizing agent that works effectively differs depending on the matrix resin, it is necessary to distinguish the carbon fibers into several types only by the sizing agent. Also, surface treatments are limited to low levels to prevent embrittlement of the carbon fiber surface.

Generally, the surface treatment of carbon fibers is fixed at a level such that brittleness of the carbon fiber surface does not occur for each elastic modulus level of the carbon fibers. Also, the type of carbon fiber sizing agent is limited because of its importance for convergence.
It is difficult to find a sizing agent that exhibits high wettability and high adhesiveness with the matrix resin.

On the other hand, the impregnability of the matrix resin into the carbon fiber tow is greatly affected by the viscosity of the matrix resin and the wettability between the carbon fiber and the matrix resin. this house,
The viscosity of the matrix resin is considerably limited by the morphology of the intermediate material. In particular, the viscosity of prepreg, which is most often used as an intermediate material for carbon fiber reinforced composite materials, is several tens po.
It is of the order of ise, and it is difficult to improve the impregnating property by decreasing the viscosity. In addition, various factors such as electrical properties of carbon fiber and matrix resin, surface free energy, etc. are effective for wettability, and it is very difficult to satisfy all the factors. It becomes even more difficult to reach the desired level of curability, strength, heat resistance, etc. of the matrix resin itself.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems of the prior art and to provide a carbon fiber reinforced composite material exhibiting high mechanical properties by using carbon fiber made of a PAN precursor as a raw material. To do.

[0009]

The present invention uses an epoxy resin as a base resin, an acid anhydride as a curing agent, an imidazole catalyst as a curing catalyst, and 0.1 to 3 parts by weight of a high molecular weight surfactant having a carboxyl group. A carbon fiber reinforced composite material in which an epoxy resin composition to which a part is added as an additive is used as a matrix resin and a carbon fiber obtained from a polyacrylonitrile precursor is used as a reinforcing fiber is used as a means for solving the above problems.

Examples of the base resin in the present invention include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, tetraglycidyl diaminodiphenylmethane, cresol novolac polyglycidyl ether, and phenol novolac polyglycidyl ether. . The epoxy resin is not limited to these, but bisphenol A diglycidyl ether and bisphenol F diglycidyl ether having a good balance of physical properties such as strength, adhesiveness and heat resistance are preferable.

Examples of the curing agent include methyl tetrahydrophthalic anhydride and methyl nadic acid anhydride, and the addition amount thereof is 50 to 50 which is a stoichiometric amount based on the epoxy resin.
Must be 120%. This is because if it exceeds this range, the heat resistance of the cured product decreases. 70-10
0% is more preferable.

Examples of the imidazole-based catalyst in the present invention include 2-ethyl-4-methylimidazole and 1-benzyl-2-methylimidazole, and the amount by weight of epoxy is preferably 0.1 to 5 parts by weight. If it is less than this range, the curing speed will be remarkably slow, and if it is more than this range, the stability of the resin viscosity in the intermediate material state will be significantly impaired, which is not preferable. 0.5 to 3 parts by weight is more preferable.

The high molecular weight surfactant which is an additive in the present invention is the most important factor in the present invention. This is because, by adding a high molecular weight surfactant having a carboxyl group, excellent impregnation of the matrix resin into the carbon fiber tow and excellent adhesion between the matrix resin and the carbon fiber can be imparted only for the first time. . That is, by adding a high molecular weight surfactant having a carboxyl group, the surface tension of the matrix resin is lowered to enhance the impregnability of the matrix resin into the carbon fiber tow, and at the time of curing the matrix resin, the carbon fiber-matrix resin interface This is because the high molecular weight surfactant itself also plays a role as a binder by participating in the reaction to increase the adhesive strength at the carbon fiber-matrix interface. Further, the surface tension of the matrix resin is lowered, so that the air serving as a void source can be easily released.

The high molecular weight surfactant in the present invention must have a carboxyl group, and examples thereof include ammonium salts of high molecular weight polycarboxylic acids and high molecular weight saturated polyesters. Addition amount is 0.1 parts by weight to epoxy
Must be ~ 3 parts by weight. This is because if the amount is less than this, the effect of addition does not appear, and if the amount is too large, the demerits such as reduction in heat resistance are large. 0.5 to 2 parts by weight is more preferable.

The carbon fiber used in the present invention is not particularly limited as long as it is made of PAN type precursor.
There is no limitation on the firing conditions at the time of manufacturing the carbon fiber or the elastic modulus level of the carbon fiber.

The method for molding the carbon fiber reinforced composite material of the present invention includes autoclave method, filament winding method, resin transfer molding method and the like.
Any known method may be used. However, as a method of utilizing the defoaming property of the epoxy resin in the present invention, a method of using as a low viscosity epoxy resin such as filament winding or resin transfer molding is preferable.

[0017]

The present invention will be described in detail with reference to the following examples. The adjustment of the epoxy resin, the production of the carbon fiber reinforced composite material, and the method for measuring the bending strength and Tg of the carbon fiber reinforced composite material in the examples and comparative examples are based on the following methods.

(1) "Preparation of epoxy resin": Bisphenol F diglycidyl ether (DGEBF: Ep807 manufactured by Yuka Shell Epoxy Co., Ltd.) 200 g (100 parts by weight), methyltetrahydrophthalic anhydride (MeTHP)
A) 180 g (90 parts by weight), 2 ethyl 4-methylimidazole (2E4MZ) 1.5 g (0.75 parts by weight), polymeric polycarboxylic acid alkyl ammonium salt (PCA)
S: BYK Chemie BYK-W960) was mixed and stirred in a flask to prepare an epoxy resin.

(2) "Preparation of carbon fiber reinforced composite material":
Using this epoxy resin and 40-ton elastic type PAN-based carbon fiber (HR40-12M manufactured by Mitsubishi Rayon Co., Ltd.),
A carbon fiber reinforced composite material was produced by the filament winding method. The carbon fiber reinforced composite material was wound around a flat die and heated under pressure with a press to obtain a flat carbon fiber reinforced composite material. The curing condition of the matrix resin was 140 ° C. × 1 hr.

(3) "Measurement of flexural strength of carbon fiber reinforced composite material": 0 degree and 90 degree flexural strength of the carbon fiber reinforced composite material was measured. L / D was 16 in the 90-degree bending test and 40 in the 0-degree bending test, and an indenter having an indenter tip radius of 3.2 mm was used.

(4) "Tg measurement of carbon fiber reinforced composite material": Tg of the carbon fiber reinforced composite material was measured by TMA. The measurement conditions were a temperature rising rate of 10 ° C./min.

Example 1 3 g (1.5 parts by weight) of PCAS was added to prepare an epoxy resin, and a carbon fiber reinforced composite material was produced from the epoxy resin. Table 1 shows the 0-degree and 90-degree bending strength and ILSS of this carbon fiber reinforced composite material.

Comparative Example 1 A carbon fiber reinforced composite material was produced in the same manner as in Example 1 except that PCAS was not added.
0 degree and 90 degree bending strength of this carbon fiber reinforced composite material,
ILSS is shown in Table 1 together with the results of Example 1.

Example 2 1 g of PCAS in Example 1 (0.5 parts by weight, Example 2-1), 3 g
(1.5 parts by weight of Example 2-2) Three kinds of carbon fiber reinforced composite materials were produced in the same manner as in Example 1 except that the amount was changed to 5 g (2.5 parts by weight, Example 2-3). . These 9
The 0 degree bending strength and Tg were measured. Table 2 shows the results.

(Comparative Example 2) PCAS in Example 1 was 0 (0 part by weight, Comparative Example 2-1) and 7 g (3.5 parts), respectively.
Two kinds of carbon fiber reinforced composite materials were produced in the same manner as in Example 1 except that parts by weight and Comparative Example 2-2) were used. The 90 degree bending strength and Tg of these carbon fiber reinforced composite materials are shown in Table 2 together with the results of Example 2. As shown in the table, PCAS
The 90.degree. Bending strength of the steel with the addition of B. Regarding Tg,
Up to the addition of 5 g (2.5 parts by weight), it is about the same as that without addition, but when 7 g (3.5 parts by weight) is added, it is 20 ° C. lower than that without addition.

Example 3 Using the epoxy resin in which PCAS was 3 g (1.5 parts by weight) in Example 1, a cylindrical mandrel was helically wound by 85 degrees by a filament winding method to reinforce the cylindrical carbon fiber. A composite material was made. The curing conditions are the same as for the flat plate, 140 ℃ x 1h
r. When an axial cross section of these cylindrical carbon fiber reinforced composite materials was observed by an optical microscope, almost no voids were present.

Comparative Example 3 A cylindrical carbon fiber reinforced composite material was formed in the same manner as in Example 3 except that the epoxy resin containing no PCAS was used. When the axial cross section of the obtained composite material was observed with an optical microscope, it was confirmed that a large number of voids were present.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

EFFECT OF THE INVENTION The carbon fiber reinforced composite material of the present invention is a carbon fiber reinforced composite material using carbon fibers made of a polyacrylonitrile precursor as a raw material, has almost no void, and has higher mechanical properties than conventional products. It is a carbon fiber reinforced composite material.

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Claims (1)

[Claims] 1. An epoxy resin containing an epoxy resin as a base resin, an acid anhydride as a curing agent, an imidazole catalyst as a curing catalyst, and 0.1 to 3 parts by weight of a high molecular weight surfactant having a carboxyl group as an additive. A carbon fiber reinforced composite material comprising a resin composition as a matrix resin and a carbon fiber made of a polyacrylonitrile precursor as a raw material.