JPH0689156B2 - Whisker-reinforced composite sliding material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a whisker-reinforced composite sliding material, and more particularly to a whisker-reinforced composite sliding material having excellent wear resistance and lubricity.

[Background Art] Generally, in various mechanical structures, from the viewpoint of wear, which appears as an accompanying phenomenon, it is extremely important to select the type of material, such as reinforced metal, reinforced synthetic resin, or reinforced rubber, for the mechanical sliding parts.

Conventionally, in order to improve wear resistance, materials have been reinforced by compounding fibers or fine particles with metals, synthetic resins, rubbers, or the like.

For example, in the case of materials used under severe sliding conditions, such as automobile piston rings, further improvements have been achieved by combining aluminum or aluminum alloys with carbon fibers, alumina fibers, alumina-silica fibers, ceramic whiskers, or the like.

Even if the conditions are not as severe as those mentioned above, the wear resistance and/or wear resistance of sliding parts such as gears and camshafts are also important.
Alternatively, there has been much research into composite materials for improving lubricity.

However, few materials to date have both wear resistance and lubricity, and it is no exaggeration to say that there are almost no materials that have both properties to a degree that satisfies the requirements.

For example, SiC whiskers have excellent wear resistance, but problems with lubricity. Generally, the conditions that a lubricant with excellent lubricity must meet are that it does not interact with the mating material during friction, does not adhere, has high strength itself, does not cause much damage or breakage during friction, and does not damage the mating material with broken pieces that accumulate over long periods of friction. SiC whiskers can be said to have problems with the above conditions.

On the other hand, although graphite whiskers are inferior to SiC whiskers in terms of wear resistance, they are superior in the above-mentioned points and are unrivaled as lubricants by other whiskers.

[Object of the Invention] The object of the present invention is to solve the above problems and to provide a whisker-reinforced composite sliding material that is excellent in both wear resistance and lubricity. In other words, during friction,
To provide a whisker-reinforced composite material having excellent properties such as no interaction with a mating member during friction, no adhesion, etc., and high strength in itself, so that damage or breakage does not occur during friction, and even if broken pieces are generated during friction and accumulate in a sliding portion, the broken pieces do not damage the mating member.

[Disclosure of the Invention] In order to achieve the above-mentioned object, the gist of the present invention is a whisker-reinforced composite sliding material characterized in that, in a composite reinforcement containing multiple types of whiskers in the synthetic resin, the composite reinforcement contains carbon fiber produced by a vapor growth method and/or graphite whiskers, which are fibers obtained by heat-treating carbon fiber produced by the vapor growth method in an inert gas, and other whiskers.

In this invention, the vapor-grown carbon fiber and the fiber obtained by heat-treating the vapor-grown carbon fiber in an inert gas (hereinafter, sometimes simply referred to as heat-treated fiber)
Either one of the above may be used alone, or both may be used in combination. When either one of the above is used, heat-treated fiber is preferable to simple vapor-grown carbon fiber, because heat-treated fiber is superior under the above-mentioned lubricant conditions.

Whether the vapor grown carbon fiber or the heat treated fiber is used, it is preferable to further subject it to a surface treatment.

Preferred surface treatments include, for example, reflux nitric acid treatment and air oxidation treatment.

Examples of the vapor-grown carbon fiber include substrate-grown carbon fiber and fluidized-phase vapor-grown carbon fiber, but fluidized-phase vapor-grown carbon fiber is preferred because fluidized-phase vapor-grown carbon fiber has rounded ends, which reduces the cause of stress concentration when dispersed in a matrix.

Such flow-phase grown carbon fibers are disclosed, for example, in Japanese Patent Application Laid-Open No. 2003-200644.
The carbon black can be obtained by a production method characterized by heating a mixed gas of a carbon compound, an organic transition metal compound, and a carrier gas, as disclosed in Japanese Patent Application Laid-Open No. 60-54998, a production method characterized by heating a mixed gas of a carbon compound, an organic transition metal compound, and a carrier gas, as disclosed in Japanese Patent Application Laid-Open No. 60-181319, and other production methods described in Japanese Patent Application Laid-Open Nos. 60-185818 and 60-216816.

The vapor-grown carbon fibers in this invention are not limited to those obtained by the above-mentioned exemplary manufacturing methods, and in short, any manufacturing method may be used as long as it can convert a carbon source compound into carbon fibers or carbon whiskers in a suspended state through the catalytic action of a transition metal.

The heat-treated fiber can be produced by heating the vapor-grown fiber to a high temperature of 2000°C or higher, preferably 2800°C or higher.

The heat treatment is usually carried out in an atmosphere of an inert gas such as nitrogen or argon.

The time required for the heat treatment is 5 minutes or more, but it is usually about 30 minutes.

The graphite whiskers preferred in this invention have a diameter of 10 μm or less, preferably 0.05 to 2.0 μm, and an aspect ratio of 3000 or less, preferably 200 or less.

If the aspect ratio is large and the diameter is large, the strain between the matrix and the particle may become large during the composite process.
Even if the diameter is within the above range, the aspect ratio
When the viscosity exceeds 3000, the whiskers become more entangled and flocs are formed.

Next, whiskers other than graphite whiskers include:
Examples include SiC whiskers, _Si3N4 whiskers, _{Al2O3 whiskers} , _MgO whiskers, _{AlN whiskers, B4C3 whiskers} , _{Fe2O3 whiskers} , BeO whiskers, _MoO3 whiskers, NiO whiskers, _Cr2O3 whiskers, _K2O ( _TiO2 ) ₆ whiskers _, and diamond whiskers.

The size of the whiskers other than the graphite whiskers is preferably the same as that of the graphite whiskers, and the diameter is preferably 100 mm or less.
The diameter is preferably 10 μm or less, more preferably 0.05 to 2.0 μm, and the aspect ratio is preferably 3000 or less, more preferably 200 or less.

The whisker-reinforced composite sliding material according to the present invention comprises a mixture of the graphite whiskers and other whiskers dispersed in a matrix. While it is preferable to incorporate the mixture into the matrix, the specific graphite whiskers and other whiskers may be incorporated separately into the matrix. In short, the whisker-reinforced composite sliding material according to the present invention is not particularly limited as long as the specific graphite whiskers and other whiskers are mixed in the matrix.

The volume ratio of the specific graphite whiskers to the other whiskers is usually 1:4 to 9:1, and preferably 1:2 to 3:1.

The matrix is not particularly limited, but examples thereof include polyolefin resins such as polyethylene and polypropylene, nylon-6, nylon-66, nylon-
8. Examples of the synthetic resin include polyamide resins such as nylon-11 and nylon-610, polyacetal resins such as polyformaldehyde and formalin-ethylene oxide copolymers, polycarbonate, thermoplastic polyester molding materials, polyphenylene oxide, polysulfone, polyethyl ethyl ketone, epoxy resins, polyurethane resins, polyethylsulfone, polyphenylene sulfide, and fluorine-based resins such as polytetrafluoroethylene and polytetrafluoroethylene.

Among these, preferred matrices are polyolefin resins, polyamide resins, epoxy resins, and polyacetal resins, and particularly preferred are synthetic resins such as ultra-high molecular weight polyethylene, nylon-66, polyacetal, epoxy resins, and fluorine-based resins.

The volume ratio of the whisker-reinforced composite sliding material containing the specific graphite whiskers and other whiskers in the whisker-reinforced composite sliding material is usually:
The volume fraction is 0.1 to 30%, preferably 2 to 20%.
If the content is less than this, the effect of blending the specific graphite whiskers with other whiskers may not be sufficient, and if it is more than 30%, the contact between the whiskers will become too great and the composition obtained by blending the specific graphite whiskers with other whiskers in the matrix will become brittle, which may result in the effect of blending the composite reinforcing material being lost.

The compound reinforcement material can be mixed and dispersed in the matrix by any means known in the art to which this type of technology belongs.

BEST MODE FOR CARRYING OUT THE INVENTION Example 1 Graphite whiskers with a diameter of 0.2 μm and an average length of about 53 μm were used.
m of vapor-grown carbon fiber was heat-treated at 2800°C for 30 minutes.
The whiskers were then surface-treated with refluxing nitric acid for 5 hours. The graphite whiskers were mixed with SiC whiskers with an average diameter of 0.3 μm and an average length of 110 μm in a 1:1 volume ratio. Alcohol was added and the mixture was thoroughly stirred in a mixer. The alcohol was then evaporated. A pelletized composite material containing nylon-66 and the mixed whiskers was then produced in a pelletizer, with the mixed whiskers accounting for 8% by volume. The pelletized composite material was then injection-molded into plates, from which 10 mm x 10 mm rectangular test pieces were cut. These test pieces were then subjected to abrasion tests using a φ100 pure iron disk.

The wear conditions were a load of FN = 165N (surface pressure = 1.65MPa), a friction track diameter of PCDφ84, and a sliding distance of 4km. The change in weight was measured before and after the experiment using an electronic balance to determine the specific wear rate, which was 0.035×10 ^-7 mm ³ /mmN.

(Comparative Example 1) The same procedure as in Example 1 was carried out except that only SiC whiskers were used as whiskers. The specific wear rate was 0.
050×10 ^-7 mm ³ /mmN.

Comparative Example 2 The same procedure as in Example 1 was carried out except that no whiskers were used and only nylon-66 was used. The specific wear rate was 0.10×10 ⁻⁷ mm ³ /mmN.

(Comparative Example 3) Only graphite whiskers were used as whiskers.
When the same procedure as in Example 1 was carried out, the specific wear rate was 0.
065×10 ^-7 mm ³ /mmN.

Taking the results of Example 1 and Comparative Examples 1 to 3 together,
When whiskers are blended with nylon-66, the specific wear rate decreases, resulting in improved wear resistance. However, when comparing graphite whiskers alone with SiC whiskers alone, it is clear that the graphite whiskers do not contribute as much to wear resistance as SiC whiskers (compare Comparative Examples 1 and 3), but the mixture of graphite whiskers and SiC whiskers achieves improved wear resistance compared to SiC whiskers alone, demonstrating a synergistic effect.

(Example 2) Graphite whiskers with a diameter of 0.2 μm and an average length of about 53 μm
m of vapor-grown carbon fiber was heat-treated at 2800°C for 30 minutes.
The graphite whiskers were then surface-treated with refluxing nitric acid for 5 hours. These whiskers were mixed with _{Si3N4 whiskers} with an average diameter of 0.2 μm and an average length of 50 μm in a volume ratio of 1:2, and alcohol was added to the mixture, which was then thoroughly stirred in a mixer. The alcohol was then evaporated.
Furthermore, the mixed whiskers were dispersed in an aluminum alloy (AC8A) so that the volume ratio of the mixed whiskers was 15%, to produce whisker-reinforced aluminum (FRM).

This FRM was cut into a test piece measuring 40 x 40 x 4 mm, and a wear test was carried out using a φ4 pure iron pin as the mating material.

The wear conditions are load FN = 32.4N, friction track diameter is PCDφ
31, sliding velocity V = 0.062 to 1.0 m/s, sliding distance 4 km
The wear amount of the test piece was measured by measuring the change in weight before and after the experiment using a direct-visual electronic balance, and the specific wear amount was found to be 0.4×10 ^-7 mm ³ /mmN.

(Comparative Example 4) The same procedure as in Example 2 was carried out except that only Si ₃ N ₄ whiskers were used as whiskers. The specific wear rate was
The value was 0.6×10 ⁻⁷ mm ³ /mmN.

(Comparative Example 5) Only graphite whiskers were used as whiskers.
When the same experiment as in Example 2 was carried out, the specific wear rate was 0.7
×10 ^-7 mm ³ /mmN.

(Example 3) Graphite whiskers with a diameter of 0.5 μm and an average length of about 100 μm
Vapor-grown carbon fibers measuring 1/4" (3000°C) were heat-treated for 30 minutes at 2800°C and then surface-treated for 3 hours in refluxing concentrated nitric acid. These whiskers were mixed with SiC whiskers measuring 0.2 μm in average diameter and 90 μm in average length at a volume ratio of 3:1. Alcohol was added to the mixture and thoroughly stirred in a mixer, after which the alcohol was evaporated. Three types of composite materials were prepared using the mixed whiskers and epoxy resin (LY-556 manufactured by Ciba-Geigy).

A circular groove with an outer diameter of 4 mm was cut out from the composite material, and its friction characteristics with a rotating disk made of pure Fe were evaluated.
Table 1 shows the results for a friction speed of 20 cm/sec and a friction distance of 2 km.
Shown below.

Comparative Example 6 The same test as in Example 3 was carried out on a resin alone and a composite material containing only one type of whisker.

The results are shown in Table 2.

As can be seen from the above examples and comparative examples, not only wear resistance but also a reduction in the coefficient of friction was observed by using graphite whiskers, which are carbon fibers produced by vapor growth and/or fibers obtained by heat-treating carbon fibers produced by the vapor growth method in an inert gas, in combination with other whiskers.

Furthermore, whisker-reinforced composite sliding materials do not damage mating materials and are extremely promising as friction materials.

[Industrial Applicability] According to the present invention, by blending and dispersing graphite whiskers, which are carbon fibers produced by vapor phase growth and/or fibers obtained by heat-treating the carbon fibers produced by the vapor phase growth method in an inert gas, together with other whiskers in a matrix, it is possible to obtain a composition having much greater wear resistance and lubricity than a composition in which only other whiskers are blended and dispersed in a matrix.
Such a composite reinforcement can be provided.

Generally, when a second component is added to maintain the excellent properties of a first component while compensating for its shortcomings, the shortcomings of the first component are improved by the second component, but the first component is not.
Considering that the excellent properties of one component are often diminished by the presence of the first component, it is noteworthy that in this invention, the blending of the specific graphite whiskers further enhances the excellent wear resistance of the other whiskers and improves the lubricity that is a drawback of the other whiskers.

Claims (12)

[Claims] [Claim 1] A whisker-reinforced composite sliding material containing whiskers in a synthetic resin matrix, characterized in that it contains graphite whiskers, which are carbon fibers produced by vapor growth and/or fibers obtained by heat-treating carbon fibers produced by the vapor growth method in an inert gas, and other whiskers. 2. The whisker-reinforced composite sliding material according to claim 1, wherein the heat treatment temperature is 2,000° C. or higher. 3. The graphite whiskers have a diameter of 10 μm.
2. The whisker-reinforced composite sliding material according to claim 1, wherein the aspect ratio is 3,000 or less. 4. The graphite whiskers have a diameter of 0.05 to 1.0 mm.
2.0 μm and an aspect ratio of the whisker-reinforced composite sliding material according to claim 1. Claim 5: Whiskers other than graphite whiskers are Si
2. The whisker-reinforced composite sliding material according to claim 1, wherein the whisker is C whisker. Claim 6: Whiskers other than graphite whiskers are Si
_2. The whisker-reinforced composite sliding material according to claim 1, which is made of _3N4 whiskers. Claim 7: The whiskers other than graphite whiskers are:
Its diameter is 0.05 to 2.0 μm, and its aspect ratio is 2
2. The whisker-reinforced composite sliding material according to claim 1, wherein the average molecular weight of the whisker-reinforced composite sliding material is 00 or less. 8. A whisker-reinforced composite sliding material,
2. A whisker-reinforced composite sliding material according to claim 1, wherein the volume ratio of the graphite whiskers to the whiskers other than graphite whiskers is 1:4 to 9:1. 9. A whisker-reinforced composite sliding material,
2. A whisker-reinforced composite sliding material according to claim 1, wherein the volume ratio of the graphite whiskers to the whiskers other than graphite whiskers is 1:2 to 3:1. 10. The synthetic resin is a polyolefin resin.
2. The whisker-reinforced composite sliding material according to claim 1, which is one selected from the group consisting of polyamide-based resins, epoxy-based resins, polyacetal-based resins and fluorine-based resins. 11. The volume ratio of the graphite whiskers to the other whiskers in the whisker-reinforced composite sliding material is 0.1
2. The whisker-reinforced composite sliding material according to claim 1, wherein the whisker content is 30% or less. 12. The volume ratio of the graphite whiskers to the other whiskers in the whisker-reinforced composite sliding material is 2 to 100%.
20%的颗粒重量。 20% of the whisker-reinforced composite sliding material according to claim 1.