JP2005325248A - Carbon fiber reinforced plastic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost carbon fiber reinforced plastic which improves the impregnation properties of carbon fibers with a matrix resin without deteriorating the properties. <P>SOLUTION: The carbon fiber reinforced plastic is obtained by impregnating carbon fibers with a matrix resin, and the matrix resin is obtained by modifying a base matrix resin with a component having a higher surface energy than the surface energy of the base matrix resin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to carbon fiber reinforced plastics, and more particularly to a matrix resin used for carbon fiber reinforced plastics.

  One of fiber reinforced composite materials is carbon fiber reinforced plastics (hereinafter abbreviated as CFRP) made of carbon fiber and resin. As the matrix resin constituting the CFRP, many resins such as radical polymerization resins such as unsaturated polyester resins, vinyl ester resins and acrylic resins are used in addition to generally used epoxy resins. Carbon fiber used in CFRP is a fiber whose chemical composition is mostly composed of carbon (90% or more), and is obtained from regenerated cellulose, polyacrylonitrile (PAN), pitch, etc., and has high strength carbon fiber and high elasticity. A distinction is made between carbon fibers and the like. This carbon fiber is lightweight and has particularly excellent properties with respect to specific strength and specific modulus. In addition, because of its excellent heat resistance and chemical resistance, it is effective as a reinforcing material and is widely used.

  However, since this carbon fiber is generally poor in impregnation with the matrix resin, there has been a disadvantage that it is difficult to sufficiently exhibit the excellent properties of the carbon fiber in CFRP using this carbon fiber.

  Various attempts have been made to improve the impregnation of the matrix resin into the carbon fibers. For example, the method of lowering the molecular weight of the matrix resin to lower the resin viscosity, the method of thinning the carbon fiber bundle or fabric, and the surface treatment of the carbon fiber to bring the surface energy of the carbon fiber closer to the surface energy of the matrix resin Examples thereof include a method for improving wettability (see, for example, Patent Documents 1 to 3).

JP 2000-355881 A JP 2000-355884 A Japanese Patent Laid-Open No. 2001-3266

  However, in the method of lowering the resin viscosity by lowering the molecular weight of the matrix resin, the impregnation property is increased, but the physical properties of the matrix resin such as the thermal decomposition temperature and the resin strength are lowered, so that the physical properties of the CFRP using the same are also lowered. . Moreover, in the method of increasing the impregnation property by thinning the carbon fiber bundle or the woven fabric, it is not possible to produce a thick plate-like body, and in order to obtain a thick plate-like body, the thin plate-like body must be laminated. Had the problem. Furthermore, in the method of surface treatment of carbon fiber to improve the wettability by bringing the surface energy of the carbon fiber closer to the surface energy of the matrix resin, a new surface treatment process is required, and the raw material costs such as sizing agent are increased. In addition to the problem of increase in the size, it is difficult to uniformly attach the sizing agent to the carbon fiber, and the impregnation property is uneven.

  The present invention has been made in view of the above situation, and an object thereof is to provide a low-cost carbon fiber reinforced plastic with improved impregnation of carbon fiber and matrix resin without deteriorating the physical properties of the resin. .

  The carbon fiber reinforced plastics of the present invention are carbon fiber reinforced plastics obtained by impregnating a carbon fiber with a matrix resin, and the matrix resin is a component having a surface energy higher than that of the base matrix resin. It is characterized by being a modified matrix resin modified by the above.

  According to the carbon fiber reinforced plastics of the present invention, since the modified matrix resin modified with a component having a surface energy higher than that of the base matrix resin is used for the base matrix resin, the surface energy of the matrix resin is reduced. It is higher than the conventional one and the wettability to the carbon fiber is improved. Therefore, the impregnation property of the matrix resin with respect to the carbon fibers is improved without lowering the viscosity of the matrix resin, and as a result, carbon fiber reinforced plastics having excellent performance can be provided.

Hereinafter, preferred embodiments of the carbon fiber reinforced plastics of the present invention will be described.
In the present invention, the surface energy is increased by modifying the matrix resin to improve the impregnation of carbon fibers. The means for increasing the surface energy is not particularly limited, and any means can be selected, but radicals are generated by irradiating a base matrix resin that does not have a functional group in the molecular chain with an electron beam or radiation. An embodiment using a modified matrix resin into which a functional group has been introduced by a graft polymerization method in which polymerization with a modifying component is performed is preferred. As such a base matrix resin, an olefin resin such as polyethylene and polypropylene is preferably used.

  Components introduced into the base matrix resin by graft polymerization for modification include ethylenically unsaturated bond-containing carboxylic acids and anhydrides thereof. Specific examples include monocarboxylic acids such as acrylic acid and methacrylic acid, dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, and carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride. Chemical formula 1 shows the structural formula of a modified matrix resin in which maleic anhydride is introduced into polypropylene as an example of the present invention.

As the graft polymerization amount of the modifying component with respect to the base matrix resin, the number of carbon atoms (C) in the base matrix resin molecule and the number of carboxyl groups (COOH) of the modifying component are preferably in the range of the following formula.
40 <(C) / (COOH) <1400 (in the case of polypropylene)
27 <(C) / (COOH) <930 (in the case of polyethylene)
When maleic anhydride is graft-polymerized to polypropylene, it is preferable that the content of maleic anhydride is 0.3 to 10% by weight, as shown in Examples described later.

  The carbon fiber used for the carbon fiber reinforced plastics of the present invention may be produced from any raw material such as pitch, rayon, or polyacrylonitrile, and is not particularly limited. Moreover, the kind may be any kind such as a high strength type low elastic modulus carbon fiber, medium high elasticity carbon fiber, and ultra high elasticity carbon fiber. Furthermore, the form can use arbitrary things, such as what has a sheet form form, such as a long fiber, a short fiber, or a textile fabric, a knitted fabric, and a nonwoven fabric.

  Examples of the carbon fiber sheet include woven fabrics, unidirectionally arranged sheets, nonwoven fabrics, mats, and the like, and combinations thereof. The weaving structure is not particularly limited, and other than the plain weaving, twill weaving, satin weaving, etc., these original structures may be changed. Further, both the weft and the warp may be the above carbon fiber, or may be a mixed weave with other carbon fibers or fibers other than carbon fibers. Examples of such fibers include inorganic fibers such as glass fibers, Tyranno fibers, and SiC fibers, and organic fibers such as aramid, polyester, polypropylene, nylon, acrylic, polyimide, and vinylon.

  The carbon fiber reinforced plastics of the present invention are compounded with matrix resin using these fibers as reinforcing fibers, such as unidirectional prepreg, cross prepreg, tow prepreg, short fiber reinforced resin impregnated sheet, short fiber mat reinforced resin impregnated sheet, etc. Carbon fiber reinforced plastics.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
[Resin graft]
After dry blending 0.03 kg of maleic anhydride, 0.03 kg of t-butylperoxybenzoate and 10 kg of crystalline propylene homopolymer powder, the mixture was melt-kneaded at 210 ° C. with a kneader (manufactured by Moriyama Seisakusho) and grafted with maleic anhydride. A polypropylene resin (PP-1) was obtained.

[Preparation of measurement sample]
1 g of PP-1 was placed on a hot press adjusted to a surface temperature of 200 ° C., preheated for 5 minutes, and then a pressure of 5 MPa was applied to produce a film.

[Measurement of surface energy]
Distilled water (manufactured by Wako Pure Chemical Industries, Ltd.) with known surface energy and liquid paraffin (manufactured by Wako Pure Chemical Industries, Ltd.) are dropped in an amount of 0.2 μl on the film prepared above, and a contact angle measuring device (trade name) : GI, manufactured by ERMA INC.), The contact angle was measured. In the measurement, the contact angle was measured 30, 60, and 90 seconds after dropping, and the contact angle immediately after dropping was determined from the regression line. The following formula was used for the calculation of the surface energy.
γ = γd + γp
γd = 7.95 × (1 + cos θp) ²
γp = [72.8 × (1 + cosθw) -2 × (γd × 21.8) 0.5] 2/204
(In the above equation, θw is the distilled water contact angle and θp is the liquid paraffin contact angle)

[Measurement of impregnation depth]
Using an oven (trade name: High Temp Oven PHH-200, manufactured by Tabai Co., Ltd.), the ambient temperature was set to 230 ° C., 30 g of PP-1 was added and held in a constant temperature bath for 1 hour to melt. A carbon fiber fabric (trade name: TCS-S3001, manufactured by Toho Tenax Co., Ltd.) having a basis weight of 300 g was cut into 50 × 50 mm, and seven layers were laminated on a stainless steel bat so that the carbon fiber textures were orthogonal to each other. On this laminate, a metal cylinder having an outer diameter of φ26, an inner diameter of φ22, and a weight of 100 g was placed. The bat was placed in a thermostat and 5 g of melted PP-1 was poured. After leaving for 5 minutes in a thermostatic bath, the bat was taken out and cooled indoors. The impregnation depth with respect to the plate thickness direction was measured using SEM (trade name: S-800, manufactured by Hitachi).

[Measurement result]
The relationship between the graft amount of maleic acid and the surface energy of the matrix resin is shown in FIG. 1, and the relationship between the surface energy and the impregnation depth is shown in FIG. As is apparent from the figure, the surface energy of the matrix resin increases with the grafting of maleic acid, and the impregnation depth increases with the increase of the surface energy. The maleic anhydride content is preferably in the range of 0.3 to 10% by weight. When the content is less than 0.3% by weight, the effect of the present invention cannot be obtained. On the other hand, if the grafting amount is more than 10% by weight, the maleic acid component sterically interferes with the molecular chain, so that the molecular chain must be cut and maleic acid grafted to the end. However, if the molecular chain is cleaved, the molecular weight of the matrix resin is lowered, so that desired physical properties cannot be obtained, which is not preferable.

  As described above, according to the multiaxial laminated reinforcing material for fiber reinforced plastic of the present invention, the impregnation property can be improved without increasing the viscosity of the matrix resin, so that a thick mat can be formed without reducing the physical properties of the resin. Impregnation can be performed.

It is a graph which shows the relationship between the graft amount of maleic acid in the matrix resin of this invention, and surface energy. It is a graph which shows the relationship between the surface energy of the matrix resin of this invention, and the impregnation depth to a carbon fiber.

Claims (2)

  Carbon fiber reinforced plastic obtained by impregnating a carbon fiber with a matrix resin, wherein the matrix resin is a modified matrix resin obtained by modifying a base matrix resin with a component having a higher surface energy than the base matrix resin. Carbon fiber reinforced plastics.   2. The carbon fiber according to claim 1, wherein the modified matrix resin is a thermoplastic resin and is a modified matrix resin obtained by graft polymerization of an ethylenically unsaturated bond-containing carboxylic acid or an anhydride thereof. Reinforced plastics.

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