JPH10132021A - Piezoelectric damping material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily adjust electroconductivity in piezoelectric damping material obtained by scattering piezoelectric particulates and electroconductive particulates in high polymer matrix by adopting glassy carbon particulates to the electroconductive particulates. SOLUTION: Piezoelectric damping material having excellent characteristics suitable for a damping member is formed by scattering piezoelectric particulates and electroconductive particulates in high polymer matrix. Glassy carbon particulates are used for the electroconductive particulates. Ceramic or high polymer piezoelectric material is used for the piezoelectric particulates. Mean diameter of the pizoelectric particulates ranges between 0.1 and 50 micrometers. Its content may be desirably between 20 and 70vol% in respect to whole of the piezoelectric damping material. Sphrical glassy carbon obtained by burning spherical phenol resin under inactive atmosphere (including vacuum) is preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a piezoelectric damping material. In particular, an excellent vibration damping member suitable as a vibration damping member for reducing or excluding vibrations generated in transportation equipment-related members such as vehicles, railways, and aircraft, construction / building material-related members, and business-related members such as home appliances and OA equipment. The present invention relates to a piezoelectric damping material having vibration characteristics.

[0002]

2. Description of the Related Art As a conventionally known damping material, a polymer-based viscoelastic material is often used. For example, a damping steel plate in which a polymer-based viscoelastic layer is sandwiched between thin steel plates is practically used. Has been This is because the generated viscoelastic layer is deformed by the force of the generated vibration, and when this returns to the original state, the vibration energy changes to heat due to the friction between the molecules,
It is intended to exert a vibration damping effect.

[0003] Recently, attempts have been made to use a material having piezoelectric characteristics as a vibration damping material ("new material" vo
l.5, p66-69, 1993, JP-A-5-240298, JP-A-6-
No. 85346). The vibration damping material in this case is made of a resin composite material filled with piezoelectric particles and conductive particles. The mechanism takes out the generated vibration energy as an electric potential by piezoelectric conversion, and further consumes the vibration energy as Joule heat by flowing a generated current through a conductive path formed by the conductive particles. That is, when vibration is applied to the piezoelectric composite material, the vibration energy is converted into electric energy by the piezoelectric effect, and an alternating voltage is generated in the piezoelectric particles. Then, the composite material has an appropriate resistance due to the presence of the conductive particles in the composite material, and the electric energy generated thereby is eventually consumed as Joule heat.

In this case, if the resistance of the piezoelectric composite material is R, the capacitance of the piezoelectric particles is C, and the frequency to be attenuated is ω, when the condition of R = 1 / ωC is satisfied as the impedance matching condition, It is known that the vibration is damped most quickly. Therefore, by setting an appropriate conductivity corresponding to the natural frequency, the vibration damping effect can be increased.

[0005]

By the way, in a vibration damping material composed of a composite material containing piezoelectric particles and conductive particles, carbon black is generally used as the conductive particles.
Carbon particles such as acetylene black are used. When such carbon particles are used, it is known that the electrical conductivity of the composite material sharply increases when the carbon particles reach a certain concentration (critical filling amount) (Japanese Unexamined Patent Publication (Kokai) No. Heisei 9 (1994) -207).
5-240298, `` Journal of the Adhesion Society of Japan '' vol.23, p103-11
1, 1987).

In order to solve this problem, Japanese Patent Application Laid-Open No. 6-85346 discloses that carbon particles can be reduced by using elastic graphite having both compressibility and recovery force against compression when a mechanical external force is applied. It is disclosed that the conductivity can be gradually changed in the vicinity of a concentration at which network aggregation occurs. However, even when elastic graphite is used, the change in conductivity is slightly slower than when using general carbon particles, but it is extremely difficult to adjust the conductivity to a predetermined optimum range. It is.

[0007] As described above, in the conventional piezoelectric damping material, the electric conductivity rapidly changes in the vicinity of the critical filling amount of carbon particles, and it is very difficult to adjust the electric conductivity to a predetermined optimum range. There was a problem. As described above, it is difficult to adjust the conductivity of a material to a desired value, which means that it is difficult to industrially produce a piezoelectric material having a conductivity that exhibits a good vibration damping effect. Means that.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and facilitates the adjustment or control of the electrical conductivity for obtaining an excellent vibration damping effect. It is an object of the present invention to provide a piezoelectric composite material that is suitable for:

[0009]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve such problems, and as a result, by using granular glassy carbon as the conductive particles, the conductivity can be easily adjusted. They have found that they can do so and have reached the present invention. That is, the present invention is a piezoelectric damping material in which a particulate piezoelectric substance and conductive particles are dispersed in a polymer matrix, wherein the conductive particles are granular glassy carbon. The gist is a piezoelectric damping material.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
According to the findings of the present inventor, it has been found that by adding granular glassy carbon as a component for imparting conductivity, a change in conductivity with respect to a change in the content of granular glassy carbon can be made gentle.

The reason why the change in conductivity can be moderated by employing granular glassy carbon as described above is not always clear, but is presumed to be due to the following mechanism. The reason why the conductivity changes rapidly near the critical loading of carbon particles such as carbon black, acetylene black and elastic graphite is that conductive particles such as carbon particles are stitched in a polymer matrix near the critical amount. This is considered to be caused by agglomeration of the particles, whereby the distance between the particles becomes short and the conductivity sharply increases. However, when granular glassy carbon as used in the present invention is used, aggregation does not occur unlike the above-described carbon particles, so that it is considered that a sudden increase in conductivity does not occur.

As the particulate piezoelectric substance in the present invention, conventionally known ceramic-based and polymer-based piezoelectric materials can be used as long as the object of the present invention can be achieved. Barium titanate (BT), lead zirconate titanate (PZ)
T), lead zirconate titanate lanthanate (PLZ)
T), a three-component system or a four-component system based on lead titanate (PT) -lead zirconate (PZ) is preferably used. As the three-component or four-component element, Nb,
Mg, Ni, Mn, Co, Sn, Fe, Cd, Sb, A
1, Yb, In, Y, Ta, Bi, W, Tl, Re and the like are used. Examples of the polymer-based piezoelectric material include poly-γ-methyl glutamate, diacetyl cellulose, polyvinylidene fluoride, tetrafluoroethylene, trifluoroethylene, polyvinyl chloride, nylon 11, nylon 7, and the like.

The average particle size of the particulate piezoelectric substance is 0.1.
About 50 μm is preferable, and the content of the particulate piezoelectric substance is 10 to 8 with respect to the whole piezoelectric damping material.
0 vol% is preferable, and 20 to 70 vol% is more preferable. If it exceeds 80 vol%, the workability of the piezoelectric damping material deteriorates, and if it is less than 10 vol%, the conversion efficiency from vibration energy to electric energy decreases, which is not preferable.

As the granular glassy carbon used in the present invention, those obtained by carbonizing a thermosetting resin such as a furfuryl alcohol resin or a phenol resin in an inert atmosphere (including vacuum) can be used. Among them, spherical glassy carbon obtained by firing a spherical phenol resin at a temperature of 1000 ° C. or more in an inert atmosphere is particularly preferable. The method for producing the spherical phenolic resin is described in
And commercial products are also available.

The average particle size of the granular glassy carbon used in the present invention is preferably in the range of 0.1 to 100 μm, more preferably 1 to 70 μm, and further preferably 3 to 30 μm.
μm is more preferred. When the average particle size is smaller than 0.1 μm or larger than 100 μm, it becomes difficult to control the resistance. The average particle size according to the present invention refers to an average of 100 or more granular glassy carbons observed with a microscope having a magnification of 200 times.

The content of the particulate glassy carbon is not particularly limited, and can be appropriately selected according to the desired function. For example, a piezoelectric material and a polymer matrix can be selected in accordance with the magnitude and location of the vibration to be reduced, and the content of the granular glassy carbon can be designed so as to obtain the optimum conductivity. The conductivity of the piezoelectric vibration damping material (log sigma) is, it is preferable to add a particulate glassy carbon to be in the range of ^{-5~-9Ω -1 · cm -1,} -6~-8Ω -1 · cm -1 It is more preferable to add them so as to fall within the range.

Examples of the polymer matrix include thermosetting resins such as phenolic resins and epoxy resins, polyolefins such as polyethylene and polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyurethane, polyamide, polyester, polyether, and the like. Thermoplastic resins such as polyarylate and liquid crystal polymer, and synthetic rubbers such as natural rubber, silicone rubber, and butadiene can also be used. In particular, when polyvinylidene fluoride, which is a piezoelectric polymer having a high dielectric constant, is used, the piezoelectric effect of the entire composite can be enhanced by performing the polarization treatment at a high temperature. Therefore, the efficiency of converting mechanical energy into electrical energy increases, and the energy conversion efficiency increases.

The piezoelectric vibration damping material of the present invention can be easily formed by ordinary molding methods such as injection molding, extrusion molding, casting molding, vacuum molding, press molding, transfer molding, and paste processing according to the properties of the polymer matrix. It can be formed into a desired shape, and secondary processing is easy. When a vibration damping member / part is formed, the entire member / part can be made of the piezoelectric vibration damping material of the present invention. Further, a kind of a laminated structure or a tilted structure using the piezoelectric damping material of the present invention may be used only in a region of the member / part close to the vibration source.

The piezoelectric vibration damping material of the present invention can be effectively used for suppressing and attenuating vibrations and noises in a wide range of fields including industrial use and consumer use such as automobiles, audio equipment, construction and construction.

[0020]

Next, the present invention will be described specifically with reference to examples. Example 1 A piezoelectric ceramic PZT (PE60A manufactured by Fuji Titanium Co., Ltd.) having an average particle size of about 5 μm as a particulate piezoelectric substance, a spherical glassy carbon having an average particle size of about 5 μm as a conductive particle (GCP-10H manufactured by Unitika), 1900 ° C.), and polyvinylidene fluoride (PVDF) was used as a polymer matrix. A piezoelectric damping material in which the volume fraction of the particulate piezoelectric substance was unified to 40 vol% and the conductivity was changed by changing the filling amount of spherical glassy carbon was produced by the following method.

That is, after kneading with a plast mill at 190 ° C., heat press molding is performed at 200 ° C., 40 kg / cm ² for 3 minutes, and then cold pressed at 40 kg / cm ² for 3 minutes to obtain a 0.5 mm thick sheet. Was. A 100 × 15 mm sheet was cut out from the sheet and the conductivity was measured. The conductivity was measured using Loresta AP and Hiresta (manufactured by Mitsubishi Chemical Corporation). Further, using the apparatus shown in FIG. 1, one end of the sheet is fixed and vibration is applied by a vibrator, and residual vibration is detected using a non-contact displacement sensor.
The time to become e (τ: decay time constant) was calculated. The damping effect can be evaluated by the numerical value of τ.

Comparative Example 1 Spherical glassy carbon was replaced with carbon black (CB: TO
An experiment was performed in the same manner as in Example 1 except that the experiment was changed to KAI SEAST 300).

REFERENCE EXAMPLE 1 Elastic graphite was synthesized according to the method described in JP-A-64-9808. 6 g of coke powder (PC-40, manufactured by Lonza)
Mixed acid 10 with a 50/50 volume ratio of 7% concentrated sulfuric acid and 70% concentrated nitric acid
After adding little by little to 0 ml, the mixture was heated at 100 ° C. for 1 hour. Then, the mixture was filtered, washed sufficiently with water, and dried. This is dispersed in water, and 1N-N
aOH was added. After filtration through a membrane filter (0.1 μm), 1N-HCl was added to the filtrate so as to have a pH of 2 or less, and the precipitated powder was filtered and dried. This powder is heated to 2800 ° C. in an argon stream at a rate of 400 ° C./min.
, And held for 30 minutes for graphitization to obtain elastic graphite having an average particle size of about 2 µm. The yield was 3.3 g.

Comparative Example 2 An experiment was conducted in the same manner as in Example 1 except that the spherical glassy carbon was changed to the elastic graphite obtained in Reference Example 1.

FIG. 2 shows the values of the conductivity measured for the samples of Example 1 and Comparative Examples 1 and 2, and FIG. 3 shows the decay time constant. FIG. 2 shows the content (vol%) of the conductive particles on the horizontal axis,
5 is a graph in which the logarithm of the conductivity (Ω ⁻¹ · cm ⁻¹ ) of the sample is represented on the vertical axis. As is apparent from the graph, the piezoelectric damping material of the present invention is accompanied by a change in the filling amount of spherical glassy carbon. It can be seen that the conductivity changes very slowly, and in Comparative Examples 1 and 2, the conductivity changes so as to rise almost vertically at a specific content. This indicates that the desired conductivity can be easily adjusted. FIG. 3 is a graph in which the abscissa represents the content (vol%) of the conductive particles and the ordinate represents the decay time constant (msec) of the sample. As is apparent from FIG. It can be seen that the material has a greater damping effect over a wider range than the comparative example.

[0026]

According to the present invention, it is possible to easily adjust or control the electrical conductivity for obtaining an excellent vibration damping effect, and thus to provide a piezoelectric composite material suitable for production on an industrial scale. , Automobile, audio, construction and construction industries,
Vibration and noise suppression in a wide range of fields regardless of consumer use,
It can be used effectively for attenuation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a residual vibration measuring device for measuring residual vibration of a piezoelectric damping material of the present invention.

FIG. 2 is a graph showing a change in conductivity with respect to the content of conductive particles for the piezoelectric damping material of the present invention and a material of a comparative example.

FIG. 3 is a graph showing a change in a decay time constant with respect to a content ratio of conductive particles for a piezoelectric vibration damping material of the present invention and a material of a comparative example.

Claims (1)

[Claims] 1. A piezoelectric damping material comprising a particulate piezoelectric substance and conductive particles dispersed in a polymer matrix, wherein the conductive particles are granular glassy carbon. Damping material.