JPH0341000A - Method for modifying whisker - Google Patents

Abstract

PURPOSE:To make it possible to incorporate whiskers into a matrix at a high volume fraction by treating the surfaces of the whiskers with an ionized inert gas. CONSTITUTION:A gaseous mixture of an organometallic compd. with hydrocar bon and a hydrogen-contg. carrier gas is heated to 800-1,300 deg.C to obtain whiskers made of carbon fibers having >=0.1mum diameter and <=300 aspect ratio by vapor growth in a suspended state. The whiskers are put in a reaction chamber, this chamber is evacuated to 10<-1>-10<-5>Torr pressure and an inert gas is introduced and ionized by impressing DC voltage or causing high frequency discharge, hollow cathode discharge or arc discharge. By treatment with the ionized inert gas, the surfaces of the whiskers are roughened or functional groups such as carbonyl or nitro group are introduced into the surfaces.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for modifying whiskers, and more specifically, the present invention relates to a method for modifying whiskers. This invention relates to a method for modifying whiskers.

[Issue 8 to be solved by the prior art and the invention] Whiskers, which are acicular crystals, exhibit mechanical properties close to theoretical values, and therefore are a common reinforcing material for fiber-reinforced composite materials.
For example, AAM of carbon fiber, aramid fiber, etc.
It is attracting attention as an even better reinforcing material.

However, whiskers have problems with wetting and adhesion to the matrix due to their crystalline perfection.

Therefore, whiskers usually require surface modification.

Methods for modifying the surface of whiskers include, for example, surface treatments such as oxidation and coating with different substances, each of which is used depending on the matrix.

For example, when the matrix is a synthetic resin, surface treatments such as gas phase oxidation and liquid phase oxidation are generally performed.

However, since whiskers are completely crystalline,
It is very difficult to form functional groups on the surface, and sufficient surface treatment effects cannot be achieved.

In addition, the whisker surface may be coated with a metal film such as aluminum or nickel or a ceramic film such as silicon carbide by chemical vapor deposition, physical vapor deposition, etc., but since the coating material easily peels off, it is difficult to satisfy the requirements. No results have been obtained.

On the other hand, with respect to reinforcing materials containing whiskers, it is known that the higher the volume content of whiskers in the composite material, the greater the effect as a composite material.

However, for example, in graphite whiskers whose surface has been modified by conventional methods, if the volume content exceeds 20%, the fluidity of the matrix will generally decrease and the uniform dispersibility will decrease, so molding is difficult. The problem is that it cannot be done. This problem is especially serious in the crosstalk method.

The present invention has been made based on the above circumstances.

An object of the present invention is to provide a whisker modification method that enables uniform surface modification and easily obtains whiskers that can be contained in a matrix at a high volume content.

[Means for Solving the Problems] As a result of intensive studies by the present inventor to solve the above-mentioned problems, it has been found that uniform surface modification can be achieved by a specific method of treating the surface of whiskers with a specific inert gas. The present invention was achieved by discovering that it is possible to easily obtain whiskers that can have a high volume content of 6 in a matrix.

The structure of the invention according to claim 1 is a whisker modification method characterized in that the surface of the whisker is treated with an ionized inert gas.

The structure of the invention according to claim 2 is the whisker modification method according to claim 1, wherein the whisker is a vapor-phase truncated fiber.

The present invention will be described in detail below.

As the whiskers whose surface can be suitably modified by the method of the present invention, whiskers obtained by vapor phase growth can be suitably used. Further, as long as it can be obtained by a vapor phase growth method, for example, one obtained by a fluidized vapor phase method, a substrate method, etc. can be suitably used.

In the method of the present invention, whiskers made of vapor phase and carbon fiber can be particularly preferably used.

Furthermore, in the method of the present invention, the whiskers may be graphite whiskers obtained by heat-treating the whiskers in an inert atmosphere such as nitrogen or argon.

Regarding the diameter and aspect ratio of the whiskers,
There is no particular restriction, but it is usually preferable that the diameter is 0.1 μm or more and the aspect ratio is 300 or less.

In the present invention, the whiskers are treated with an ionized inert gas (hereinafter, this treatment may be referred to as bombardment treatment).

The inert gas is not particularly limited as long as it does not react with whiskers, and examples thereof include argon, helium, neon, xenon, and nitrogen.

The inert gas can be introduced into a reaction chamber whose pressure is reduced to, for example, 1 G-' to 10-% Torr, and ionized by applying a DC electric field, high-frequency discharge, hollow cathode discharge, arc discharge, or the like.

The conditions for treating the whiskers with an ionized inert gas cannot be unconditionally defined because they vary depending on the type of inert gas, but for example, the pressure during treatment is usually 10-'-10-'7 orr. , especially 10
-'~1(1-'Torr.

Note that when treating the whiskers with an ionized inert gas, it is preferable to always expose fresh whiskers to the ionized inert gas, for example by stirring the whiskers.

In this way, whiskers treated with ionized inert gas have dramatically improved wettability and adhesion.

The reason for this is not clear, but when the whisker surface is treated with ionized inert gas.

It is presumed that the surface of the whiskers has been roughened or functional groups have been introduced.

Examples of functional groups to be introduced include carbonyl groups, carboxyl groups, nitro groups, amino groups, and hydroxyl groups.

In any case, the vapor-grown carbon fiber whose surface has been modified by the method of the present invention is, for example, Ia! It can be suitably used as a reinforcing material in the production of 1-reinforced plastics (FRP), fiber-reinforced ceramics (FRC), and fiber-reinforced metals (FRM).

In addition, when using the reinforcing material modified by the method of the present invention, surface treatments such as corona discharge treatment, nitric acid oxidation treatment, metal plating treatment, electroless plating treatment, and silane coupling treatment are performed in combination. Good too.

[Example] Next, Examples and Comparative Examples of the present invention will be shown to further specifically explain the present invention.

(Example vapor-grown carbon fibers were heated at 2.900°C in an argon atmosphere.
Graphite whiskers were obtained by graphitizing the mixture for 40 minutes. The graphite whisker aggregate was placed in a reaction chamber maintained at a reduced pressure of 5 x 10-'' Torr while stirring.

The graphite whiskers were brought into contact with ionized argon at 600 V and 1 mA/cm" for 60 minutes to modify the surface thereof.

Next, 100 ji [Okibe's epoxy resin [L Y
-556, manufactured by Ciba Geigy], 90 parts by weight of curing agent [
HY-917J, manufactured by Ciba Geigy) and 1 part by weight of a curing accelerator [DY-062, manufactured by Ciba Geigy] as a plastic matrix,
By adding the surface-modified graphite whiskers so that the volume content is 20% and curing under the conditions of heating to 10°C for 2 hours, then heating to 150°C for 2 hours, A composite material was obtained.

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

The results are shown in Table 1.

(Comparative Example 1) A composite material was obtained in the same manner as in Example 1, except that the treatment with ionized argon was not performed.

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

The results are shown in Table 1.

(Example 2) Vapor grown carbon fibers were grown in an argon atmosphere.

Graphite whiskers were obtained by graphitization treatment at °C for 40 minutes. 5 X 10-'To
While stirring this graphite whisker aggregate installed in a reaction chamber maintained at a reduced pressure of 500 V
, 0.7 mA/am” to ionized nitrogen.

Contact this graphite whisker for 120 minutes,
Its surface +1! I made a pledge.

Next, 100 parts by weight of epoxy resin [LY-556
[manufactured by Ciba Geigy], 90 parts by weight of curing agent [HY-9
17J, manufactured by Ciba Geigy Co., Ltd.] and 1 part by weight of a curing accelerator [DY-01i2, manufactured by Ciba Geigy Co., Ltd.] as a plastic matrix. The graphite whiskers were added and cured for 2 hours while heating to 100°C and then for 2 hours while heating to 150°C to obtain a composite material.

This composite material was subjected to a compression test in accordance with JIS K720B.

The results are shown in Table 1.

(Comparative Example 2) A composite material was obtained in the same manner as in Example 2, except that the treatment with ionized nitrogen was not performed.

This composite material was subjected to a compression test in accordance with JIS K720B.

The results are shown in Table 1.

(Example 3) While stirring an aggregate of vapor-grown carbon fibers installed in a reaction chamber maintained at a reduced pressure of 5 X 10-3 Torr,
This vapor-grown carbon fiber was brought into contact with ionized argon at 600 V and 0.7 mA/cm'' for 60 minutes to modify its surface.

Next, 100 parts by weight of epoxy resin [LY-55
6, manufactured by Ciba Geigy], 90 parts by weight of curing agent [HY-
917J, manufactured by Ciba Geigy Corporation] and 1 part by weight of a curing accelerator [DY-062, manufactured by Ciba Geigy Corporation] was used as a plastic matrix, and the surface was modified so that the volume content was 20%. A composite material was obtained by adding the above-mentioned vapor-grown carbon fibers and curing the mixture for 2 hours while heating to 100°C and then for 2 hours while heating to 150°C.

This composite material was subjected to a compression test in accordance with JIS K720B.

The results are shown in Table 1.

(Comparative Example 3) A composite material was obtained in the same manner as in Example 3, except that the treatment with ionized argon was not performed.

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

The results are shown in Table 1.

(Leave below) Table 1 (Evaluation) As is clear from Table 1, the composite material of Example 1 has lower compressive stress and compressive modulus than the composite material of Comparative Example 1. It's improving.

Further, the same can be said when comparing the composite material of Example 2 and the composite material of Comparative Example 2. Furthermore, the composite material of Example 3 has improved compressive stress compared to the composite material of Comparative Example 3. From these results, it was confirmed that the whisker-containing composite material whose surface was modified by the method of the present invention had significantly improved mechanical strength.

[Effects of the Invention] According to the present invention, since the surface of the whiskers is treated with an ionized inert gas, it is possible to uniformly modify the surface, and it is also possible to incorporate the whiskers at a high volume content in the matrix. It is possible to provide an industrially useful method for modifying whiskers, which has the advantage of being able to modify whiskers into whiskers.

Procedural amendment 1990 August 6th day

Claims (2)

[Claims] (1) A whisker modification method characterized by treating the surface of the whisker with an ionized inert gas. (2) The method for modifying whiskers according to claim 1, wherein the whiskers are vapor-grown carbon fibers.