JPH02212370A - Composite material - Google Patents

Abstract

PURPOSE:To form a composite material having superior mechanical strength and heat resistance by dispersing specified vapor grown fine carbon fibers in a matrix. CONSTITUTION:This composite material is formed by dispersing vapor grown fine carbon fibers having 3.44-3.39Angstrom spacing (d) between graphite layers and obtd. by vapor growth in a matrix such as a metal, plastics or ceramics. The pref. diameter of the vapor grown carbon fibers is 0.01-1.0mum and the pref. aspect ratio is 100-200. The vapor grown carbon fibers have been preferably subjected to surface modification such as oxidation, CVD, sputtering or coupling treatment.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing composite materials, and more specifically, the present invention relates to a method for manufacturing composite materials, and more specifically, the present invention relates to a method for manufacturing composite materials, and more specifically, the present invention relates to a method for manufacturing composite materials, and more specifically, to The present invention relates to a method for manufacturing a composite material obtained by dispersing.

[Conventional technology and the problem to be solved by the invention] Traditionally, carbon fiber is used as plastic and ceramic.

BACKGROUND OF THE INVENTION Carbon fiber composite materials made by dispersing fillers in a matrix of metal, rubber, etc. are used in various fields.

The reason why carbon fiber composite materials are used in such various fields is that when carbon fibers are dispersed in the matrix, the mechanical strength and heat resistance of the composite material are improved. In recent years, there has been a demand for materials with even greater mechanical strength and heat resistance.

By the way, in a high-temperature furnace, a mixed gas of raw materials such as benzene and methane and a carrier gas such as hydrogen is mixed.

Created fine carbon fiber M [VGCF] produced by vapor phase growth by heating to 1,000 to 1,300°C with a transition metal compound containing iron, nickel, etc. as a catalyst.
(Vapor Grown Carbon F
iber)] is known to have better mechanical properties than PAN type carbon fiber (polyacrylonitrile carbon Ia).

Therefore, a composite material made by dispersing the generated fine carbon fibers in a matrix as a filler has been considered, but such a composite material did not have sufficient mechanical strength as expected. .

VGCF is a substance before graphitization and is incompletely crystallized, the interplanar spacing d of the graphite layers is 3.47 to 3.44λ, the tensile strength of VGCF is 2.5 to 5 GPa, and the elasticity is 1. Since the rate is 350-450 GPa, this VGC
It is presumed that the mechanical strength of the composite material containing F as a filler could not be increased.

For this VGCF, add 2,800 to 3.0
G W (Graphite W h
isker) as a filler.

GW is a material with good crystallinity in which the interplanar spacing of graphite layers reaches approximately 3.36 mm, and its tensile strength is 10 to 20 G.
Pa, and the elastic modulus is 700 to 800 GPa.

Therefore, it is expected that a composite material containing GW as a filler will be an excellent material with high mechanical strength, but in reality, no material with the expected mechanical strength has been obtained. .

According to the inventors' studies, it is presumed that GW has poor wettability (or compatibility) with matrices such as plastics, ceramics, metals, and rubbers, which hinders improvement in mechanical strength.

Therefore, it is possible to improve the wettability to the matrix by modifying the surface of this GW.
As mentioned above, since graphitization has been achieved to a high degree and the crystallinity is good, it is extremely difficult to modify its surface.

As detailed above, when VGCF is used as a filler, the strength of the composite material cannot be increased due to its weak mechanical strength, and even if the surface of VGCF is modified, the mechanical strength cannot be improved. On the other hand, even if GW was used as a filler, due to its poor wettability, even if the mechanical strength of GW was excellent, the mechanical strength of the composite material could not be improved. be.

This invention has been made based on the above circumstances.

That is, an object of the present invention is to provide a composite material with high mechanical strength by blending specific created fine carbon fibers as a filler.

[Means for Solving the Problems] This invention for solving the above fi11 uses fine carbon fibers created by vapor phase growth in which the interplanar spacing d of the graphite layers is within the range of 3.44 to 3.3 g. It is a composite material characterized by being made by dispersing in a matrix.

What is important in this invention is that the interplanar spacing d of the graphite layers of the created fine carbon fibers is within the range of 3.44 to 3.39 degrees. By blending the created fine carbon fibers with such a specific interplanar spacing d into the matrix, the resulting composite material has excellent mechanical strength and heat resistance that could not be achieved with conventional VGCF or GW blends. It comes to have.

In other words, if the created fine carbon fiber has a surface spacing larger than 3.44, the mechanical strength of the created fine carbon fiber will be low as in the past, and the mechanical strength of the composite material containing it as a filler will be lower. It is not possible to achieve improvement in strength and heat resistance, and when using engineered fine carbon fibers with a spacing d smaller than 3.39, the crystallization is too large and the wettability with the matrix is poor. It is not possible to improve the mechanical strength and heat resistance of a composite material containing this.

The created fine carbon fiber used in this invention has a diameter of 0.
．． 01 to 1.0 pm, and the aspect ratio is 100 to 2.
The diameter is preferably 0.00. If it is smaller than m, there is a disadvantage that it becomes difficult to disperse the created fine carbon fibers in the matrix, and if it is larger than 1.0 pm, the strain between the fiber and the matrix may become large during the compositing stage. There is an inconvenience. Also, the aspect ratio is 1
If the aspect ratio is smaller than 00, the mutual bonding force between the created fine carbon fibers and the matrix will be insufficient, and if the aspect ratio is larger than 200, the created fine carbon fibers will not be bonded properly when dispersed in the matrix. Fine carbon fibers aggregate, making uniform dispersion difficult.

The above-described fine carbon fibers related to the present invention can be produced as follows.

That is, in a high-temperature furnace, a mixed gas of raw materials such as benzene and methane and a carrier gas such as hydrogen is mixed with an organic fiber metal compound containing iron, nickel, etc. as a catalyst at a temperature of 1,000 yen.
The crude fine carbon fiber obtained by heating to ~1,300°C is further heated to 1,800~2,500°C,
Preferably, it can be produced by graphitizing at 2,100 to 2,500°C for about 30 minutes or more, preferably 40 to 50 minutes.

Examples of matrices used in the present invention include thermoplastic resins such as nylon, polyphenylene sulfide, polybutylene terephthalate, polyester, polypropylene, polybutene, polystyrene, polyacetal, and polyvinyl chloride, as well as epoxy resins, unsaturated polyester resins, and tetrafluoride resins. , plastics such as thermosetting resins such as phenolic resins and urea-formalin resins, ceramics such as alumina, silicon nitride, silicon carbide, silicon dioxide, and zirconium dioxide, aluminum, nickel,
Metals such as titanium, copper, and iron, as well as polybutadiene, polyisoprene, and natural rubber.

Rubbers such as styrene rubber can be mentioned. Which matrix is preferable cannot be determined as it depends on the use of the composite material, but for plastics, epoxy resin is preferred.

Silicon nitride is preferred for ceramics such as nylon, and aluminum is preferred for metals.

The amount of created fine carbon fibers added to the matrix is usually 5 to 30% by volume, preferably 10 to 25%. If the zero volume ratio is less than 5%, the mechanical strength etc. of the composite material can be improved. If the amount exceeds 30%, uniform dispersion becomes extremely difficult.

In addition, the created fine carbon fibers blended into the matrix are
Although the created fine carbon fibers produced by the above-mentioned production method can be used as they are, it is preferable to use them after further surface modification treatment.

This is because the surface modification treatment can improve the wettability of the created fine carbon to the matrix.

The surface modification treatment method is appropriately selected depending on the type of matrix.

For example, when the matrix is plastic, surface modification treatment includes methods of imparting appropriate functional groups or vapor-deposited metals to the surface of the created fine carbon fibers by oxidation treatment, CVD treatment, sputtering treatment, coupling treatment, etc. Something will happen.

Composite materials using surface-modified fine carbon fibers as fillers have a strength of 1.5 to 2 times the strength of the matrix.
．． Composite materials that use conventional VGCF as filler, which has been subjected to zero surface modification treatment to have 5 times the strength, have an improvement in mechanical strength of about 1.2 to 1.50 compared to the strength of the matrix. However, the mechanical strength of composite materials using conventional GW as a filler that has undergone surface modification treatment is approximately 1.1 to 1.4 times higher than that of the matrix. In view of the fact that only a certain number of carbon fibers have been observed, it is surprising that the effect obtained by blending a specific created fine carbon fiber having a specific interplanar spacing as a filler is surprising.

Next, the present invention will be explained in further detail by showing specific examples of the present invention.

[Example] (Example 1) Created fine carbon fiber (VGCF) with a diameter of 0.6 pm and an average length of 72 pm was heated for t, a in an argon atmosphere.
Graphitization treatment was performed at 0°C, 2,000°C, and 2,200°C for 40 minutes, and then surface treatment was performed with reflux concentrated nitric acid for 10 hours.

Next, 100 parts by weight of epoxy resin [LY-556].

manufactured by Ciba Geigy], 90 parts by weight of curing agent [HY-91
7J] and 2 parts by weight of a curing accelerator to form a plastic matrix in a volume proportion of 12.
5% surface-treated synthetic fine carbon fibers, and cured under the conditions of 2 hours while heating to 120°C under a pressure of 50kg/cm'', and 2 hours while heating to 150°C. A composite material was obtained.

This composite material was subjected to a compression test in accordance with JIS 7208.

Table 1 shows the compression test results and the interplanar spacing d of the created fine carbon fibers.

(Comparative Example 1) A fine carbon fiber # (VGCF) with a diameter of 0.6 pm and an average length of 72 μm was heated at 2.50 μm in an argon atmosphere.
A composite material was produced by treating the generated fine carbon fibers obtained by graphitizing them at 0° C. and 2,900° C. for 40 minutes in the same manner as in Example 1 above.

This composite material was evaluated in the same manner as in Example 1,
The results are shown in Table 1.

(Comparative Example 2) A VGCF composite material having a diameter of 0.6 pm and an average length of 72 μm was prepared in the same manner as in Example 1 without heat treatment.

This composite material was evaluated in the same manner as in Example 1,
The results are shown in Table 1.

(Example 2) A fine carbon fiber (VGCF) having a diameter of 0.6 gm and an average length of 75 μm was prepared in an argon atmosphere for 2.1 gm.
Graphitization treatment was performed at 00° C. for 40 minutes, and then surface treatment was performed using oxygen plasma for 10 minutes.

Next, 100 parts by weight of epoxy resin [LY-556].

manufactured by Ciba Geigy], 90 parts by weight of curing agent [HY-91
7J] and 2 parts by weight of a curing accelerator as a plastic matrix, with a volume ratio of 15%.
Adding Sosei fine carbon fibers that have been surface-treated so that
2 while heating to a temperature of 120℃ at a pressure of 50kg/cm''.
A composite material was obtained by curing for 2 hours while heating at 150°C.

This composite material was subjected to a compression test in accordance with JIS K7208.

Table 2 shows the compression test results and the interplanar spacing d of the created fine carbon fibers.

(Comparative Example 3) A generator, fine carbon fiber, $9 (VGCF) with a diameter of 1.5) hm and an average length of 90 pm, and 100 parts by weight of epoxy resin [LY-55] as a plastic matrix.
6], a mixture consisting of 90 parts by weight of a hardening agent [+1Y-917J], and the volume ratio of the created fine carbon fibers is 1.
5%, heated to 120℃ for 2 hours while applying a pressure of 50kg/cm'', and then
A curing treatment was performed by heating to 150° C. for 2 hours under the same pressure to obtain a composite material.

This composite material was subjected to a compression test in the same manner as in Example 1, and the test results are shown in Table 2.

(Comparative Example 4) The same procedure as in Comparative Example 3 was conducted using a created fine carbon fiber (VGCF) having a diameter of 0.05 μm and an average length of 20 pm.

The results are shown in Table 2.

(Example 3) Created fine carbon fibers (VGCF') with a diameter of 0.34 m and an average length of 541 Lm were grown for 2 hours in an argon gas atmosphere.
, graphitized at 100°C for 30 minutes, and then
The surface was treated with oxygen plasma for 10 minutes, and then with a silane coupling agent [D403, manufactured by Shin-Etsu Silicone Co., Ltd.].

Next, 100 parts by weight of epoxy resin [LY-556].

manufactured by Ciba Geigy], 90 parts by weight of curing agent [HY-91
7J] and 2 parts by weight of a curing accelerator [DY-062] was used as a plastic matrix, surface-treated created fine carbon fibers were added to this so that the volume ratio was 15%, and the mixture was heated at a pressure of 50 kg/cs2. at a temperature of 120℃
A composite material was obtained by curing for 2 hours while heating to 150°C and then for 2 hours while heating to 150°C.

When this composite material was subjected to a compression test in the same manner as in Example 1, the compressive strength was 35.2 kg/cm.
"l", compression modulus is 780kg/cm""t"
there were. Further, the interlayer spacing d was 3.40 people.

(Example 4) Created fine carbon fibers with a diameter of 0.3 pm and an average length of 407 zm were heated at 2,200°C in an argon atmosphere.
Graphitization treatment was carried out for 0 minutes to obtain graphite whiskers with an interplanar spacing of 3.39 whiskers. This graphite whisker (20% by volume) was mixed with Si:+N4 (313N, :A
Text, 03:Y, O:l:90:3:7) and heated in a hot press (manufactured by Fuji Denpa Kogyo ■) in a nitrogen atmosphere (l kg/cm") at a pressure of 250 kg/cs".
, and sintered for 10 minutes at 1,800°C. after that,
At HIP (manufactured by Nikkiso), pressure 1800 kg/cm2 (
Re-sintering was performed at 1,750° C. for 30 minutes (in a nitrogen atmosphere) to obtain whisker-reinforced ceramics.

Using the obtained reinforced ceramics, the diameter is 4 mm and the thickness is 3.
A sample with a length of 40 mm was made, and a bending test and toughness measurement were performed, and the bending strength was 112 kgf.
/ Zenho 2 toughness value; 7. :l MParm.

(Comparative Example 5) The same procedure as in Example 3 was carried out except that created fine carbon fibers having a diameter of 0.34 m, an average length of 40 JLm, and a face spacing of 3.46 were used.

Bending strength: 88 kgf/s” Toughness value: 5.8 MParm I got it.

(Example 5) Created fine carbon fibers with a diameter of 0.8 uLm and an average length of 90 μm were heated at 2,200°C in an argon atmosphere for 40 minutes.
Graphitization treatment was carried out for a minute to obtain graphite whiskers with an interplanar spacing of 3.39 people. Thereafter, a Ti film was formed on the graphite whisker surface while surface renewal was performed for 30 minutes under an argon pressure of 5×10-'torr using an arc type ion blating device. Titanium-coated graphite whiskers (25
% by volume) in molten aluminum (750-800°C) to obtain graphite whisker-reinforced aluminum. The resulting reinforced aluminum has a radius of 10 mm and a thickness of 2.
A sample piece with a length of 150 mm was prepared and its tensile strength was measured, and the average tensile strength was 55 kgf/-2.

(Comparative Example 6) Souvenir fine carbon fiber with a diameter of 0.8gm, average length of 90uLm, and interplanar spacing of 3.46mm! 9 (VGCF)
The test was conducted in the same manner as in Example 4, except that the average tensile strength was 48 kgf/2.

[Effects of the Invention] According to the present invention, a composite material with high mechanical strength can be provided by blending specific created fine carbon fibers having a specific interplanar spacing as a filler.

Claims (4)

[Claims] (1) A composite material characterized in that fine carbon fibers produced by vapor phase growth are dispersed in a matrix, and the interplanar spacing d of the graphite layers is within the range of 3.44 to 3.39 Å. (2) The diameter of the created fine carbon fiber is 0.01 to 1.
The composite material according to claim 1, having a diameter of 0 μm and an aspect ratio of 100 to 200. (3) The composite material according to claim 1, wherein the generated fine carbon fibers are surface-modified. (4) The composite material according to claim 1, wherein the matrix is one selected from the group consisting of plastics, ceramics, and metals.