JP3192400B2 - Piezoelectric dispersion type organic composite vibration damping material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration damping material obtained by dispersing a dispersing material in a polymer matrix, and more particularly, to converting vibration energy into electric energy and consuming it to reduce vibration. Regarding what makes you.

[0002]

2. Description of the Related Art Conventionally, the following (a) to (d) are known as vibration damping materials obtained by dispersing a dispersing material in a polymer matrix. (A) A scaly inorganic substance such as mica is dispersed as a dispersing material in a polymer matrix, and vibration energy is absorbed by mutual friction of the dispersing material due to vibration. (B) A combination of the above-mentioned frictional effect and magnetic interaction using a magnetic material powder such as ferrite as a dispersant.
These have a loss coefficient tan δ of around 0.5 at the maximum.

(C) In addition, there is an inorganic ceramics piezoelectric powder used as a dispersing material for the purpose of converting vibration energy into electric energy, but the elastic modulus of the ceramics is different from that of the polymer material. Too much, the effect of transferring mechanical energy is poor, and the powder has a spherical shape, so the antipolarization coefficient is as large as 0.3, the strain-electric conversion effect is reduced, and the loss coefficient tan δ is 0.5 or less.

[0004] (d) In addition, there has been an attempt to absorb vibration energy by friction between the gel and the polymer matrix using a polymer gel as a dispersing material, but all have a loss coefficient of 1. In particular, those using gel are soft and difficult to use as structural materials.

[0005] Since any of the above damping materials mainly uses the mechanical interaction between the polymer matrix and the dispersing material, the strain amplitude dependency is large, and it is effective where the amplitude is large. When the distortion amplitude was in the range of 10 ^-7 , the effect was not so much exhibited.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances of the prior art, and has as its object to have a hardness which can be used as a strength material and a loss factor tan δ.
Is as large as 1 or more, and a vibration damping material having a small strain amplitude dependency is obtained.

When an impedance (L) is connected to a piezoelectric ceramic and resonated with the capacitance (C) of the ceramic, an extremely large loss coefficient can be obtained.
undand Vibration (1991) "by NWHAGOOD and others. This technology is applied to polymer piezoelectric films (PV
DF: polyvinylidene fluoride) and cyanoethylated hydroxyethylcellulose have been reported by the present inventors to provide a large loss coefficient and a sound insulation effect near the resonance frequency (1994 Spring Meeting of the Society of Polymer Science, Yokohama). The effect of the internal loss due to the electrical loss of the piezoelectric material is shown by Equation 1, and in an electromechanical resonance state, the denominator of Equation 1 is close to zero, and thus does not depend on the electromechanical conversion constant K of the material. It is theoretically expected to grow. The expectation is that PVDF (K = 0.1) and cyanoethylated hydroxyethyl cellulose (K = 0.03)
The present inventor has shown that this is experimentally correct in the range of .about.0.01).

(Equation 1) Here, K _ij : electromechanical coupling constant δ: normalized resonance frequency ratio (electric and mechanical) r: normalized resistance g: real part of γ: normalized electrical frequency γ: normalized frequency

The following problems were pointed out when applying this technology to building walls. When the vibration damping effect of the piezoelectric body is represented by an electric equivalent circuit, a series equivalent circuit of a piezoelectric body as a battery and L (impedance), C (capacity), and R (resistance) is obtained. Since the effect of LC is canceled in the resonance state in the equivalent circuit constituted by the following equation, the optimum resistance R of the circuit network that obtains the maximum electric loss under the condition needs to satisfy the condition represented by Expression 2.

(Equation 2) Here, w: resonance frequency C: capacitance of the piezoelectric material R: total resistance of the circuit network including the electrode resistance of the piezoelectric material K: electromechanical conversion coefficient of the piezoelectric material K = 0.1 for PVDF

Since the C (capacity) of the piezoelectric material is proportional to its area, when a 30 μm-thick PVDF film is used, the area of the film is 30 × 40 cm at an acoustic measurement level using a small reverberation box. The optimal resistance is 2
It becomes 50Ω, but the size of general door is 200 × 100c
m is 0.25 Ω and the practical Al sputter electrode is 1 Ω / cm ² , so the circuit configuration in which the electrical resistance satisfies the above equation from any point of the film can be realized with a small required resistance value. Impossible.

Conversely, when the piezoelectric material is made smaller and dispersed,
In the case of the 40 × 2 mm size, the optimum resistance is as large as 10 ⁶ Ω. If the object having the micron size and having the piezoelectricity can be dispersed in the non-piezoelectric material, the optimum resistance value is as extremely large as 10 ¹³ to 10 ¹⁶ Ω. The resistivity of ordinary polymer materials falls in this region. Thus, the present inventor has come to the idea that the use of a polymer material as the piezoelectric material eliminates the need for a special circuit configuration, for example, electrodes and lead wires. Further, the present inventor has clarified in the Journal of the Society of Polymer Science, Vol. 1997, Vol. 46, that the equivalent inductance (L) component is expressed by Expression 3 based on a mechanical motion equation of the piezoelectric matrix and the material in the piezoelectric material.

(Equation 3) Here, M: mass of the piezoelectric material Y: Young's modulus D: piezoelectric d constant (piezoelectric strain constant) w: width of the piezoelectric material That is, the width of the piezoelectric material is reduced, and the organic dielectric (the Young's modulus is smaller than that of the ceramic) Two digits smaller)
It is expected that a large inductance component is obtained, and the external additional inductance represented by the HAGOOD equation becomes unnecessary. That is, the problem that the L component must be added in order to increase the damping efficiency with a conventional piezoelectric damping material in which an inorganic piezoelectric powder is dispersed in an organic polymer matrix is solved.

Furthermore, if the piezoelectric material can be dispersed in a fine needle shape, it can be predicted from a analogy of the effect of the shape anisotropy of the magnetic material that a dielectric material having a small piezoelectric d constant can be used as a piezoelectric material having a large piezoelectric constant. .

[0012]

SUMMARY OF THE INVENTION The present invention has been made based on such an idea. To solve the above problems, a piezoelectric dispersion type organic composite vibration damping material according to the first aspect of the present invention comprises: It is characterized in that an organic dielectric or ferroelectric is dispersed in a non-piezoelectric polymer matrix.
That is, vibration energy is absorbed by utilizing the strain-electric conversion effect of an organic dielectric or ferroelectric dispersed in a polymer matrix. Here, a dielectric or a ferroelectric refers to a substance that spontaneously generates electric polarization when an electrostatic field is applied or when no electric field is applied, but does not generate a direct current, and is not a dielectric generally referred to. Also, a substance which shows the same physical properties as a dielectric when in the form of a needle is included.

[0013]

In the vibration damping material, the vibration energy applied from the outside is transmitted to the organic dielectric or ferroelectric dispersed in the non-piezoelectric polymer matrix. Vibration energy is converted into electric energy by the strain-electric conversion action of the dielectric or ferroelectric, and the electric energy is consumed as Joule heat (thermal energy) by resistance. As a result, the vibration is damped.

Next, the effects of the above-described basic invention and other inventions for improving the effects will be described. 1) Improvement of transmission efficiency of mechanical vibration energy According to the invention of claim 1, since an organic dielectric or ferroelectric is dispersed in a non-piezoelectric polymer matrix, the transmission efficiency of vibration energy to the dielectric is improved. Is increased, the loss coefficient tan δ is as large as 1 or more, and it is possible to obtain a vibration damping material having small strain amplitude dependency. It is desirable to use an organic dielectric or ferroelectric that is close to the elastic modulus of the polymer matrix. Thereby, the transmission efficiency of the vibration energy to the dielectric is further increased. 2) Improvement of conversion efficiency of vibration energy to electric energy The invention of claim 3 is characterized in that the shape of the dielectric or ferroelectric which is a dispersing material is made acicular. As a result, the anti-polarization coefficient was reduced, the effect of the anti-electric field based on the charge generated by the strain was reduced, and the conversion efficiency from vibration energy to electric energy was increased. In particular, by keeping the acicular ratio at 5 or more, the depolarization coefficient becomes 0.04 or less,
This effect is greater. The invention according to claim 4 is characterized in that if the needle-shaped dispersion material is a cylinder, the diameter is set, and if the needle-shaped dispersion material is a prism, the shorter one of the two sides of the cross section is set to 20 μm or less. This increases the coercive power, increases the hysteresis area, and increases energy loss. Further, the invention of claim 5 is characterized in that the volume ratio of the dispersed dielectric or ferroelectric to the matrix is selected to be 0.3 to 0.7. As a result, the reduction of the coercive power based on the interaction due to the interference of the dispersing material and the effect of the electric charge due to the increase in the filling factor of the dielectric material were balanced, and the decay ability of the damping material was increased. As described above, since the present invention utilizes the strain electric effect based on the shape anisotropy of the organic dielectric, the effect of absorbing the vibration energy is large, and unlike the application of the ordinary piezoelectric polymer film, the polarization treatment and the electrode attachment are performed. Since no process is required, the economic effect is large. Particularly, since the effect is exhibited in a region where the distortion rate is small, a remarkable effect is expected as an acoustic damping material.

An example of a method for producing a vibration damping material having a high loss factor tan δ of 1 to 15 by applying the above mechanism to a polymer composite material will be described below. Regarding the first energy transfer efficiency, ceramics such as PZT have a larger elastic modulus and specific gravity than the polymer material of the matrix, so their mutual acoustic impedances are different, and distortion of the matrix is transmitted to the ceramic piezoelectric material. It is obvious that the organic dielectric-polymer dispersion type is superior in terms of transmission efficiency because it is difficult. Regarding the shape effect of the second dispersing material, the coercive force formula shown by the curling model of the needle-shaped magnetic material is regarded as the needle-shaped dielectric material as a magnetic material.

(Equation 4) Here, according to I: magnetic susceptibility R: particle diameter R ₀ : diameter determined by exchange integration, the thinner the acicular dispersion material, the larger the coercive force in the range where it does not become a paramagnetic material (Fe 100 Å). Become. In the case of a magnetic material, the direction cannot be maintained unless the electron spins are aggregated to some extent,
In the case of a dielectric, it is considered that this restriction is reduced to the molecular size. Regarding the application of the magnetic body theory to the dielectric, it seems appropriate because there are many similarities as phenomena. When the dielectric becomes thinner due to the same phenomenon, the coercive force increases, the hysteresis area increases, and the energy loss increases. This effect can be handled in the same manner as a needle-shaped dispersion material as long as the dispersion material is connected as a whole even if the dispersion material is granular. When the acicular ratio exceeds 5 and becomes elongated, the anti-polarization coefficient decreases, and the effect of the anti-electric field due to spontaneous polarization decreases. Therefore, the acicular dielectric has an electric field proportional to its electric charge. And the loss due to the charges generated by the distortion can be increased. It is obvious that the same effect can be expected from the influence of the dielectric polarization moment on the loss effect because the coercive force increases in proportion to the magnetic susceptibility in the above equation. Furthermore, it is derived from the theoretical formula of the piezoelectric body that the loss effect is significantly increased when the dispersed dielectric is used near the mechanical electric resonance frequency. Regarding the volume effect of the dielectric, the Neel equation applied to the relationship between the filling factor of the needle-shaped magnetic material and the coercive force Hc (P) = (1−P) * Hc (0) I (P) = P * I Here, when Hc: coercive force I: magnetic susceptibility P: filling rate is applied, the optimum value of the filling rate is around 50%, and when the volume ratio of the dielectric exceeds 0.7, mutual interaction of the needle-like dielectrics occurs. As a result, the coercive power drops. Further, when the volume ratio is 0.
Below 3, the coercive power of the individual dielectrics is large, but the absolute amount is small, resulting in a reduction in energy loss. The above phenomenon of the dielectric dispersion type vibration damping material is caused by dispersing a needle-like magnetic material formed by plating in mercury into a non-magnetized matrix (a magnet material, LODOX). It can be said that this is the same phenomenon that is handled.

[0016]

Next, examples will be described. Example 1 Preparation of Sample Polyethylene chloride as a matrix (molecular weight (50,0
100 to 350,000)) and a predetermined amount of N, N-dicyclohexyl-2-benzothiazylsulfenamide as a dielectric dispersing material was measured, and heated and mixed at a temperature of 120 to 160 ° C. for 10 minutes to obtain 100 to 200 kg · cm ² . Press molding was performed under pressure to prepare a sheet having a thickness of 0.1 to 0.3 mm. A small amount of a second plasticizer such as dioctyl phthalate was added as needed in order to increase the moldability of the sample and adjust the shape and dispersion of the needles. The sheet was annealed at 80 to 100 ° C. for 30 minutes to produce various samples having different mixing ratios and mixing conditions. Sample size is 40 to 10 × 2 × 0.
1 mm. Since the melting point of N, N-dicyclohexyl-2-benzothiazylsulfenamide is around 80 ° C., it is dispersed in the form of needles during the process of precipitation and recrystallization. In the case of N, N-dicyclohexyl-2-benzothiazolsulfenamide and polyethylene chloride, cellulose fiber;
By adsorbing the dielectric on the surface of polyester whiskers or the like, the durability can be improved. In the case where the dielectric is made of nylon 11 or a liquid crystal polymer (trademark: Vectran) which can be processed into a fibrous form, it may be processed into a fine fibrous form and then cut to a predetermined dimensional ratio and dispersed. In this case, if the electric conductivity of the polymer matrix is insufficient due to the relationship between the fiber diameter and the dimensional ratio, it is also effective to supplement the electric conductivity with carbon powder and fibers. In addition, when the dielectric material to be dispersed is a compound having a relatively low molecular weight and a low melting point, and easily oozes out of the polymer matrix, it may be used by binding to the surface of an inorganic or organic material filler as necessary.
Alternatively, a predetermined shape may be maintained by dispersing between fillers. [Example 2] Polyethylene chloride was used for a polymer matrix, and nylon 11 having a diameter of 25 µmφ and a needle ratio of 5 or more was used as a dielectric.
Were mixed under the same temperature conditions as in Example 1 and pressed under the same pressure conditions to form a sheet. Example 3 A polymer cellulose fiber was used as a matrix, and wood pulp fiber 100 phr (No.
1), liquid crystal polymer fiber (Pectran®) 30 microns φ 100 phr (No. 2); 2 and a mixture of carbon powder 10% wtN, respectively, to prepare a vibration damping sheet under the same conditions as in Example 1. The loss coefficient tan δ was measured with a vibron type 2 (a measuring device manufactured by Toyo Baldwin Co., Ltd.). EDX measurement of filling ratio and needle ratio
(Energy dispersive X-ray analyzer) with SEM (scanning electron microscope).

Dependency of Loss Coefficient by Needle Ratio The needle ratio is determined by changing the temperature of the heating and mixing and the rolling reduction by a roll to produce various samples.
The loss factor was measured in Hz. The loss coefficient measurement data at 110 Hz is shown in FIG. 1, and SEM photographs of the needle ratio measurement are shown in FIGS. 7 shows an example in which the dielectric is fine and the loss coefficient tan δ is large, and FIG. 8 shows an example in which the dielectric is thick and the loss coefficient tan δ is small. From this data, it is understood that those having a needle ratio of 5 or more and a cross-sectional diameter of 20 microns or less have a large loss coefficient.

Dependency of Loss Coefficient Due to Dielectric Dispersion Ratio Samples were prepared by changing the mixing ratio of the constituent materials, and the amounts of sulfur and chlorine at predetermined locations were measured by EDX to confirm the amount of dispersion. The needle ratio of the sample is about 30,
The diameter is 10 microns. The loss factor is 3
It was measured at 5-110 Hz. FIG. 2 shows the measurement data at 110 Hz. 20% before and after 50% dispersion ratio
It can be seen that those having good characteristics.

Dependence of Loss Factor on Strain Amplitude FIG. 3 shows the amplitude dependence of the loss factor as compared with the internal friction type Gelnac (Nippon Automation Co., Ltd.) using gel as a dispersing material. The product of the present invention has no loss factor degradation at a small amplitude, and shows that the mechanism of vibration energy absorption is different from normal, indicating that it is excellent in controlling acoustic vibration.

Temperature Dependence of Loss Coefficient FIG. 4 shows a dielectric volume ratio of 50% and polyethylene chloride (CP).
E) and a sulfenamine-based additive (DZ) in a 1: 1 mixture ratio of 15% dioctyl phthalate (DO)
P) was added, and the needle ratio was 30 or more formed by heating at 160 ° C.,
4 shows the temperature dependence of the loss coefficient at 110 Hz of a composite vibration damping material having a maximum diameter of 16 microns. This sample is 100
It resonates around ℃ and shows a large loss coefficient of 3000 or more. The resonance point temperature and frequency can be changed by selecting the organic dielectric and the matrix polymer material. Such a large loss coefficient is a phenomenon that has been conventionally observed only in a liquid, and has not been obtained with a solid vibration damping material having a Young's modulus of 10 ⁶ dyn · cm ² .

The above effects are obtained when the above materials are used as the organic dielectric material and the matrix polymer, and it is obvious that the selection according to the use conditions can be made by combining the materials. .

Normal incidence sound absorption coefficient The vibration damping sheet obtained in Example 2 was tested according to the test method JISA.
According to 1405, the normal incidence sound absorption coefficient was measured. As shown in FIG. 9, good results were obtained in the frequency range of 100 to 230 Hz.

Internal Loss Increasing Rate The internal loss increasing rate based on the polymer cellulose fiber of the vibration damping sheet obtained in Example 3 is shown in FIG.
0.

Deterioration rate test The damping rate of each of the vibration damping materials obtained in the above examples after 60 days was measured. The results shown in FIG. 11 were obtained. In FIG. 4 is polyethylene chloride + N, N dicyclohexylsulfenamide
100: 100; No. 5 is No. No. 4 to which 10% wt of plasma-treated cellulose fiber was added. 6
Is a polymer cellulose + liquid crystal polymer fiber 50.

As described above, in the present invention, a dielectric substance is dispersed in a polymer matrix in a monodomain structure to obtain a damping effect by its piezoelectric effect, and does not depend on a manufacturing method. In particular, when the dielectric is a compound having a linear structure used for a liquid crystal material, a vibration damping effect can be obtained even when dispersed at the molecular level.

[Brief description of the drawings]

FIG. 1 is a graph showing the dependence of the loss coefficient on the diameter or cross-sectional diameter of a dielectric and the acicular ratio.

FIG. 2 is a graph showing a loss coefficient dependency by a fractional ratio of a dielectric.

FIG. 3 is a graph showing the strain amplitude dependence of a distributed piezoelectric damping material and an internal friction damping material.

FIG. 4 is a graph showing a resonance characteristic of a loss coefficient.

FIG. 5 is an SEM photograph showing an example of a component analysis location.

FIG. 6 is a graph showing the results of component analysis of parts C and S of the SEM photograph.

FIG. 7 is an SEM photograph showing an example of a component analysis needle ratio.

FIG. 8 is an SEM photograph showing another example of the component analysis needle ratio.

FIG. 9 is a graph showing a measurement result of a normal incidence sound absorption coefficient when a dielectric is a fiber.

FIG. 10 is a graph illustrating an internal loss increase rate when a polymer cellulose fiber is used as a matrix.

FIG. 11 is a graph showing test results of a deterioration rate of various damping materials.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI G10K 11/178 G10K 11/16 H (31) Claimed priority number Japanese Patent Application No. 9-169423 (32) Priority date June 1997 10th (June 10, 1997) (33) Countries claiming priority Japan (JP)

Claims (5)

(57) [Claims] 1. A piezoelectric dispersion type organic composite vibration damping material comprising an organic dielectric or ferroelectric dispersed in a non-piezoelectric polymer matrix. 2. The piezoelectric dispersion type organic composite vibration damping material according to claim 1, wherein an organic dielectric or ferroelectric substance having an elastic modulus close to that of the polymer matrix is used as the dispersion material. . 3. The piezoelectric dispersion type organic composite vibration damping material according to claim 1, wherein the form of the dielectric or ferroelectric is acicular. 4. A dielectric or ferroelectric material having a needle ratio of 5 or more, having a circular cross-sectional area having a diameter and a rectangular cross-sectional area having a side of 20 μm or less. The piezoelectric dispersion-type organic composite vibration damping material according to the above. 5. The piezoelectric dispersion type organic composite vibration damping material according to claim 1, wherein the volume ratio of the dielectric or ferroelectric to the non-piezoelectric polymer matrix is 0.3 to 0.7.