JP2003247802A - Strain sensor by conductive particle-polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To develop a strain sensor used to safety monitor various type structures by sensing a ground subsidence of a steel structure, a reinforced concrete structure or the like or a strain due to an earthquake. <P>SOLUTION: The strain sensor is made of a conductive particle-polymer of a linear or sheet state in which the conductive particles are dispersed in the polymer and the polymer is made of a thermoplastic elastomer. Here, the elastomer is a block copolymer of two or more ingredients. Particularly, the copolymer is preferred to be a styrene - diene block copolymer or a hydrogen- added styrene - diene block copolymer. More particularly, there is a styrene - butadiene block copolymer or styrene - isoprene block copolymer which is hydrogen-added. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive particle-polymer strain sensor, which detects various types of structures such as steel frame structures and reinforced concrete structures by detecting ground subsidence and strain due to earthquakes. It is a strain sensor used for safety monitoring of objects.

[0002]

2. Description of the Related Art A conventional strain sensor uses the electrostrictive property of a strong couple, a large number of conductive leads arranged in a direction perpendicular to the strain, and fibers move in the strain direction in accordance with the strain. There are those that use electric resistance change due to cutting depending on the amount of strain, by cutting with a cutting blade that
The most general method is one in which a metal thin film is formed on a polyimide film and a fine pattern is formed, but the resistance change due to strain deformation is used.

The above-mentioned cutting blade has practical problems. Although the latter metal thin film sensor has no practical problems, it is practically unusable for general purposes such as detection of earthquake damage to building steel frames because it is expensive and has only a small size.

Therefore, the present inventors previously proposed a strain sensor based on a system in which conductive particles such as carbon are dispersed in a polymer in Japanese Patent Application Laid-Open No. 11-241903.

[0005]

The strain sensor based on the conductive particle-polymer system described above can keep the production cost low and has a wide range of sensor sizes, so that it is possible to manufacture from large to small ones. The greatest merit is that the change in resistance value with respect to a certain amount of strain is extremely large, in other words, it is possible to obtain a sensor with extremely high sensitivity.

However, the high molecular weight ethylene-vinyl acetate copolymer (EVA) proposed in the invention of Japanese Patent Laid-Open No. 11-241903 mentioned above.
In the case of the above system, it was found that there are the following problems.
That is, the first problem is that, when a certain amount of strain is applied to the sensor and the state is maintained as it is, the electrical resistance of the sensor output decays with the passage of time.
In this case, if the amount of distortion is small, there is almost no attenuation, but attenuation appears as the amount of distortion increases. There is no problem when the strain sensor is online, but when a person measures after the earthquake, the attenuation causes an error with respect to the true strain amount. The second problem is the effect of temperature on the resistance of the sensor. This EVA is a material used as a self-regulating temperature (PTC) heater and has a switching temperature (70 ~ 8
The resistance value sharply increases around 0 ° C. When the sensor may be exposed to such a high temperature, it may not be possible to determine whether it is due to strain or due to an increase in temperature even if the resistance value of the sensor increases.

As a result of finding out these problems, the strain sensor has to be satisfied as a necessary condition.
It is to develop a strain sensor satisfying 1) high sensitivity, 2) small temperature coefficient of resistance value, and 3) no change in resistance value when constant strain application is continued.

[0008]

The three conditions necessary for the strain sensor are described above. It is not easy to satisfy these three conditions at the same time. However, it is relatively easy to satisfy only one at the expense of two of the three.
In this case, the option is obviously sensitivity.
Such a case corresponds to a polymer or rubber system having a low glass transition temperature. This is called type I. Even if it has this physical property, it cannot be said to be sufficient as a strain sensor.

Next, there are two cases in which two of the three conditions are simultaneously satisfied. Although the sensitivity of the first condition cannot be eliminated, there are two options for the second condition: to take a low temperature coefficient or to choose low attenuation under constant strain. In either case, it can be realized by a copolymer polymer such as EVA previously proposed. Taking as an example a certain type of copolymerized polymer that achieves this object, homopolymers obtained by polymerizing each monomer alone have different characteristics. A skillful combination of these differently-characterized monomers is the key to achieving the goal. Of these types, those with sensitivity and low temperature coefficient are type II _t , those with sensitivity and low attenuation characteristics are type II _d.
I will call it.

The type II _t belongs to a molded product obtained by heat-melting a system in which carbon is dispersed in an ethylene-ethyl acrylate copolymer.
-A system in which carbon is dispersed in a methylmethacrylate copolymer can provide sufficient performance within a certain temperature range.

Included in Type II _d is the above-mentioned ethylene-acrylate copolymer system, which is not heat-melted but is dissolved in a solvent and printed on a substrate (graphite carbon) -ethylene-ethyl acrylate copolymer. The system falls into this over a wide temperature range.

The last type sufficiently satisfies the above-mentioned three conditions. This is called type III. Such a case is a polymer that has a low glass transition temperature, yet exhibits a rubber-like elastic body in a wide range around room temperature, and is a polymer that is thermoplastic and dispersible in a molten state with conductive particles. is there. A so-called thermoplastic elastomer system corresponds to this. Alternatively, the less-achievable nature of the three can be reinforced by supplementary measures. The following is a summary of the means for solving the problems of type III in the present invention.

First, the present invention is a strain sensor based on a conductive particle-polymer system in which conductive particles are linear or sheet-like dispersed in a polymer and the polymer is a thermoplastic elastomer. Here, the thermoplastic elastomer is
It is a block copolymer of two or more components, and it is particularly preferable that this block copolymer is a styrene-diene-based block copolymer or a hydrogenated styrene-diene-based block copolymer. Specific examples include styrene-butadiene block copolymers and styrene-isoprene block copolymers that have been hydrogenated.

Other examples of the thermoplastic elastomer belonging to the type III of the present invention include a blend of a polyolefin polyolefin and EPDM or butyl rubber, a blend of a polyvinyl chloride NBR, and a polyurethane hard urethane. -A thermoplastic elastomer such as a polyester-polyether block copolymer, a polyamide-based polyether, a block copolymer with an amorphous polyester, or a polyester-based crystalline polyester-polyether block copolymer can be effectively used.

In the present invention, another structure belonging to type III is a modified polymer in which conductive particles are dispersed in a polymer in a linear or sheet form, and the polymer is unevenly distributed in physical properties. Is a strain sensor made of a conductive particle-polymer system. Examples of the modified polymer include modified polyester resin and amorphous polyester resin.

The present invention constructs a sensor by providing electrodes in a system in which conductive particles such as carbon are dispersed in a polymer, and utilizes the property that electric resistance changes when strain is applied to the system. It seeks to detect strain applied to the system by measuring changes. The mechanism by which the strain applied to the system leads to the change in resistance value can be explained by the tunnel effect through the conductive particle gap.
(T. Kimura, N. Yoshimura, T. Ogiso, Polymer, 40, 4149, 1
999).

As the conductive particles, graphite, carbon black, carbon whiskers, carbon nanotubes, carbon black, metal pieces, metal powder, insulating fine particles such as mica and potassium titanate to which conductivity is imparted by chemical plating or CVD. Etc. can be used. However, the particle diameter, the diameter distribution, and the like have a delicate influence on the resistance value and the sensitivity to strain.

On the other hand, the polymer as the matrix has various effects depending on its type. Most of the above-mentioned various properties from type I to type III arise from the properties of polymers. In principle, when the conductive particles are uniformly dispersed in the polymer, the change in resistance value should depend only on the strain and not on the type of polymer. This is because the resistance value depends only on the distance between particles.
When the system is subjected to strain, the strain is evenly distributed in the system, and therefore the increase in interparticle distance is also uniform in the system, and thus the change in resistance value is also uniform. Under such conditions, the resistance value does not change depending on the type of polymer. However, if the particle distribution and the interaction with the polymer are locally biased, various changes occur in the relationship between strain and resistance value.
Even if the system is subjected to a certain amount of strain, the uneven distribution of particles causes a bias in the resistance change in the system. Generally speaking, a polymer coexists with a crystalline portion and an amorphous portion, and particles tend to be localized in the amorphous portion. Naturally, the interaction between the particles and the polymer also differs between the crystalline region and the amorphous region.

One of the factors that make the relationship between strain and resistance change more complicated is the presence of local strain in the polymer.
When strain is applied to the system, it seems that the strain is distributed uniformly on the outside, but it has become clear from strain sensor research that there is a local bias in strain.
(Scheduled to be announced at the 2002 National Meeting of the Institute of Electrical Engineers of Japan, March 2002
27th of May Kogakuin University). There is a method of using a copolymer as a method of intentionally realizing such strain or local deviation of particles.

When a rubber polymer is used, even if it is a homopolymer, a large local change may be observed in the interaction between the particles and the matrix polymer. This produces a type I sensor. Studies on the uneven distribution of such interactions have not yet progressed, and it is considered that the residual stress is probably a large part.

In order to produce a highly sensitive strain sensor, there is a method of intentionally configuring the uneven distribution of the above-mentioned interactions.
As a method, a copolymer is used as a matrix polymer. In this case, each component constituting the copolymer is
When each exists as a homopolymer, it is necessary to show different physical properties from each other. It is expected that if a block copolymer is prepared by using monomers of polymers having different physical properties, polymers having locally different physical properties can be obtained. This is the localized uneven distribution of particle-polymer interactions.

Empirically, the attenuation of the resistance value when a constant strain is applied to the system and kept as it is is empirically related to the glass transition point of the system. Therefore, if the glass transition point of the polymer used is a fairly high temperature range above room temperature, it will be type _IId, and if the glass transition point is in the low temperature range, a type III sensor can be expected. As a copolymer having such properties, a thermoplastic elastomer composed of a block copolymer of a hard segment such as styrene and a soft segment such as butadiene serves as an excellent polymer material for a strain sensor of this type. is there.

Therefore, when selecting a copolymer,
It is also good to consider that the glass transition point of the block polymer of one component is room temperature or higher. Generally, a thermoplastic elastomer has rubber-like elasticity in a normal temperature range and melts at a high temperature, so that it is easy to mix and mold the conductive particles,
Further, since it is easily dissolved in the solvent of rubber, it is easy to mix and disperse graphite or the like, and a strain sensor can be obtained by an operation such as coating a base material sheet. Hereinafter, the conductive particle-polymer strain sensor of the present invention will be specifically described with reference to examples.

[0024]

Example 1 An ethylene-propylene sensor was prepared as a sensor corresponding to type I. Maleic acid modified ethylene
-Propylene (T7761 maleic acid 0.3 wt% made by Japan Synthetic Rubber) 4
Dissolve in 0 parts by weight and 400 parts by weight of toluene, mix and stir 40 parts of graphite (J-SP, made by Nippon Graphite Co., Ltd.), cast into a Teflon (registered trademark) plate with depressions, and form a sheet with a thickness of 1 mm. did. Cut this sheet into 50 × 100 mm, apply silver paste on both ends, provide electrodes with a length of 100 mm, electrode spacing of 40 mm,
The sample was used for temperature resistance-characteristics measurement. On the other hand, this sheet was cut into a dumbbell shape, electrodes were provided, and strain-temperature characteristics were measured. Temperature-resistance characteristics are measured in an air temperature chamber (Tabay Espec SU-240), and measured by Agilent 34907A.
-data acquisition switch unit and 34901A-channel mu
Data was loaded into a computer using ltiplexer. The strain-temperature characteristic was measured with a custom-made measuring system.

FIG. 1 shows the shape of the sample for strain-temperature characteristic measurement. Figure 2 shows the strain and the specific resistance of the strain sensor (the ratio of the resistance value R when the strain is applied to the resistance value Ro when the strain is applied: R
/ R _o ). It can be seen from FIG. 2 that this sensor has a very high sensitivity. The conventional metal thin film sensor has a specific resistance of 1.02 for a strain of 1%. Comparing the increase in resistance with _R / R _o = (R−R _o ) / R _o , it was 0.02 for the metal thin film sensor, but was 8.0 for the maleic acid-modified ethylene-propylene system, 400 times higher. It can be seen that is also highly sensitive.

FIG. 3 shows the relationship between resistance and temperature in this graphite-maleic acid-modified ethylene-propylene copolymer system. As can be seen from FIG. 2, the strain-electric resistance characteristics of this system, and the results of FIG. 3 show that the resistance value sharply increases at 40 ° C. or higher, so it should be noted that it is limited to use in cold regions of lower temperature.

Example 2 Hydrogenated styrene-butadiene rubber was used as another sensor corresponding to type I. 40 parts by weight of hydrogenated styrene-butadiene rubber (DR-1320P made by Japan Synthetic Rubber), toluene
Dissolve in 400 parts by weight, mix and stir 40 parts of graphite (manufactured by Nippon Graphite Co., Ltd., J-SP), and put Teflon (registered trademark) (registered trademark) with a depression
It was cast on a plate to form a sheet having a thickness of 1 mm. This sheet is cut into 50 x 100 mm, silver paste is applied to both ends, electrodes with a length of 100 mm and electrode spacing of 40 mm are provided, and temperature resistance-
The sample was used for characteristic measurement. On the other hand, this sheet was cut into a dumbbell shape, electrodes were provided, and strain-temperature characteristics were measured.
The measurement was performed by the same method as in Example 1.

FIG. 4 shows the relationship between the strain of the strain sensor and the specific resistance. It can be seen from Fig. 4 that this hydrogenated styrene-butadiene rubber (DR-1320P) sensor is also very sensitive. FIG. 5 shows the relationship between the resistance value and temperature of this graphite-hydrogenated styrene-butadiene rubber (DR-1320P) system. As can be seen from FIG. 5, in this system as well, the resistance value rapidly increases with increasing temperature, so that it is for cold regions as in Example 1.

Example 3 Ethylene-ethyl acrylate copolymer (Evaflex A712 manufactured by Mitsui-DuPont, ethyl acrylate 9 wt%) 60
A part by weight was heat-melted using a biaxial stretching roller, and 40 parts of graphite (CP manufactured by Nippon Graphite Co., Ltd.) was kneaded, and was formed into a sheet having a thickness of 1 mm by hot pressing. The strain-resistance characteristic and the temperature resistance characteristic were prepared by using the samples having the same shapes as those in the above-described examples. Both measurements were performed in the same manner.

The relationship between resistance and strain of the graphite-ethylene-ethyl acrylate copolymer system is shown in FIG. Figure 6
As can be seen from the above, the specific resistance exceeds 2 when a strain of 1% is applied. Comparing _R / Ro of this system with that of a metal thin film sensor, the graphite-ethylene-ethyl acrylate copolymer system is 50 times more sensitive. However, this system requires careful usage, as shown below.

A large strain of 5% was applied to the graphite-ethylene-ethyl acrylate copolymer system, and the change in resistance value was measured while maintaining the strain amount, which is shown in FIG. The resistance value is greatly attenuated for about 1000 seconds from the start of measurement, and the attenuation is gentle after 2000 seconds. About 600 seconds (10 minutes) from the beginning
The measured value is halved during the period. Such a sensor becomes practical if an online system is used.

The relationship between temperature and resistance of the graphite-ethylene-ethyl acrylate copolymer system is shown in FIG. As can be seen from FIG. 8, the resistance value of this system sharply increases above 70 ° C. It cannot be used at temperatures above 60 ° C. Therefore, the graphite-ethylene-ethyl acrylate copolymer type sensor made by hot melt molding has a problem of resistance decay even at a temperature of 60 ° C or less. There is a need to. However, if the amount of distortion is small, the attenuation rate becomes extremely small.

Example 4 In this example, the graphite-ethylene-ethyl acrylate copolymer system was prepared by a melting method using a solvent, instead of the thermal melting as in Example 3. To 60 parts by weight of ethylene-ethyl acrylate copolymer (Evaflex A712 manufactured by Mitsui DuPont, 9% by weight of ethyl acrylate), 500 parts of tetralin was added and dissolved, while 40 parts of graphite was dissolved.
(Nippon Graphite CP) was dispersed and 120 μm PET film was coated using a coater. The film thickness was about 50 μm. The coated film with the substrate was cut to prepare a sample in the same manner as in the previous example, and the same measurement as in Example 3 was performed.

The relationship between the strain and resistance of this system is shown in FIG. As can be seen from FIG. 9, the specific resistance is almost 2 when a strain of 1% is applied. This point is almost the same as the third embodiment. However, when a strain of 5% was applied to the system and kept as it was, as shown in FIG. 10, the attenuation of the resistance value as seen in Example 3 was not observed. But the figure
As shown in 11, the resistance-temperature characteristic of this system was not so different from that of Example 3.

In Example 4, the graphite-ethylene-ethyl acrylate copolymer strain sensor made by coating corresponds to type II _d . However, when the operating temperature range is limited to 0 to 60 ° C., it can be seen that this sensor corresponds to type III.
Therefore, it can be said that the graphite-ethylene-ethyl acrylate copolymer strain sensor is an ideal sensor belonging to type III in an environment where the temperature of the usage environment does not reach 80 ° C.

Example 5 To 60 parts by weight of an amorphous polyester resin (manufactured by Toyobo, Byron 240), 500 parts of tetralin was added and dissolved, to which 40 parts of graphite (CP manufactured by Nippon Graphite Co., Ltd.) was dispersed, 120 μm PET
The film was coated using a coater. The film thickness was about 50 μm. The coated film with the substrate was cut to prepare a sample in the same manner as in the previous example, and the same measurement as in Example 3 was performed. The relationship between resistance and strain in this system is shown in FIG. In this case, the specific resistance is less than 1.2 for a strain of 1%. As shown in FIG. 13, no attenuation is observed in resistance attenuation when 5% strain is applied. On the other hand, the relationship between the temperature and the resistance is as shown in FIG. 14, and the resistance value increases by 5.7% as the temperature rises from 0 ° C to 60 ° C. This resistance change is 0.3%
It is equivalent to the case of the strain change of. Therefore, this system corresponds to type II _d , but its sensitivity is slightly lower than the change in resistance with temperature. However, in the 3-lead system, that is, only one pole of the two sensors is a common pole, one is attached to the strain measurement target, and the other is the common pole only is attached to the target.
If the other part is floated and only one of the sensors is strained, the strain amount can be measured with the resistance value of the sensor not strained as a reference. In the case of this system, even if such a method is used, it should be used in a temperature range of 60 ° C or lower.

Example 6 To 60 parts by weight of an amorphous polyester resin (manufactured by Toyobo, Byron 300), 500 parts of tetralin was added and dissolved, and 40 parts of graphite (CP manufactured by Nippon Graphite Co., Ltd.) was dispersed therein, 120 μm PET
The film was coated using a coater. The film thickness was about 50 μm. The coated film with the substrate was cut to prepare a sample in the same manner as in the previous example, and the same measurement as in Example 3 was performed. The relationship between resistance and strain of this system is shown in FIG. In this case, the specific resistance is 1.8 with respect to the strain of 1%, and the sensitivity is higher than that of the sixth embodiment. As shown in FIG. 16, the resistance decay when a strain of 5% is applied is initially increased this time. On the other hand, the relationship between temperature and resistance is as shown in Fig. 17, and the resistance value changes from 0 ℃ to 60 ℃ as the temperature rises.
It will increase by 32%. This resistance change is equivalent to a 0.4% strain change. Therefore, this system can be used except that its sensitivity is equivalent to Type II _d , but its sensitivity is slightly lower than the change in resistance with temperature.

Example 7 This was retried with an amorphous polyester of the same kind as Example 5 or 6 but from another company. 50 against 76 parts by weight of amorphous polyester (Arakawa 7037 manufactured by Arakawa Chemical Industry)
Tetralin (part by weight) was added and dissolved, and then 24 parts by weight of graphite (CP manufactured by Nippon Graphite Co., Ltd.) was dispersed therein, and a PET film of 120 μm was coated with a coater. The film thickness was about 50 μm. The coated film with the substrate was cut to prepare a sample in the same manner as in the previous example, and the same measurement as in Example 3 was performed. The relationship between resistance and strain of this system is shown in FIG.
From FIG. 18, the specific resistance at a strain amount of 1% is about 1.2, and it cannot be said that the sensitivity is high as compared with Example 5 or 6. Next, distortion 5
% Was held and the resistance value decay was determined and shown in FIG. Also,
The relationship between temperature and resistance of this system is shown in FIG. In this system, as shown in Fig. 19, the attenuation of the resistance value is extremely small. From Fig. 20, when the temperature rises from 0 ℃ to 60 ℃, the resistance value becomes
Increase by 6.7%. This change corresponds to a strain of about 0.3%, and there is a slight problem in practical use in this state. This system corresponds to type II _d . However, even in this system, if the above-mentioned three-lead method is used, 0 ° C to 60 ° C
It becomes practical in the temperature range of.

Example 8 This time is an example for a styrene-hydrogenated butadiene-styrene block copolymer. 60 parts by weight of styrene-butene-1 copolymer (Kuraray, Septon 8006, styrene 33 wt.
%) Dissolved in 500 parts tetralin, and 40 parts graphite
(CP from Nippon Graphite Co., Ltd.) was mixed and dispersed. 120 μm of this
The PET film was coated using a coater. The film thickness was about 50 μm. The coated film with the substrate was cut to prepare a sample in the same manner as in the previous example, and the same measurement as in Example 3 was performed. The strain-resistance value relationship of this system is shown in FIG. With a strain amount of 1%, the specific resistance is 1.8 and the sensitivity is high. FIG. 22 shows the change with time in resistance value when a 5% strain amount was applied to this system and the system was held. From this figure, it can be seen that the resistance attenuation is extremely small. The relationship between the resistance value and temperature of this system is shown in FIG. The variation of the resistance value of this system in the temperature range from 0 ° C to 78 ° C is 1.4%. This resistance change corresponds to 0.014% strain application, and the temperature effect at the time of strain measurement has no practical problem if the temperature range is from 0 ° C to 78 ° C. Therefore, in the temperature range of 0 ° C. to 78 ° C., this system is a superior type III.

Example 9 A strain sensor was prepared by using a styrene copolymer as in the previous example. 76 parts by weight of styrene-hydrogenated isoprene-styrene block copolymer (Kuraray, Hybler 7125)
It was dissolved in 500 parts of tetralin, and 24 parts of graphite (CP manufactured by Nippon Graphite Co., Ltd.) was mixed and dispersed therein. This was coated on a 120 μm PET film using a coater. Film thickness is about 50
It was μm. The coated film with the substrate was cut to prepare a sample in the same manner as in the previous example, and the same measurement as in Example 3 was performed. The relationship between resistance and strain is shown in FIG. Figure 24
It can be seen that the specific resistance corresponding to a strain of 1% is 5.3 and that the sensitivity is extremely high. FIG. 25 shows the change over time in the resistance value when the strain of 5% was applied to this system and held. From Fig. 25, no resistance decay is observed. Figure 26 shows the relationship between resistance and temperature.
It was shown to. From FIG. 26, it can be seen that the resistance change in the temperature range of 0 ° C. to 80 ° C. is 8.2%. This resistance change is 0.019%
Corresponds to the application of strain. Therefore, this system
There is no problem in practical use in the temperature range of 80 ° C. In this temperature range, this system has excellent properties that can be classified as type III.

[0041]

In the conventional conductive particle-polymer strain sensor, the strain sensor has high sensitivity to strain, but when a certain amount of strain is continuously held, the problem of resistance attenuation remains unsolved. there were. Moreover, in the proposed system, the resistance value remarkably increased at high temperature, and the usable temperature range was extremely narrow. The prior art (JP-A-11-241903) also disclosed a system having no attenuation and a low temperature coefficient, but in this case, the sensitivity was not sufficient.

According to the present invention, an excellent strain sensor having a high sensitivity, having no resistance attenuation under a constant strain application, and having an effect of temperature negligible can be obtained.

[Brief description of drawings]

FIG. 1 is a morphological view of a sample for measuring strain-resistance characteristics.

FIG. 2 is a graph showing the relationship between specific resistance (R / R _o ) and strain in a graphite-maleic acid-modified ethylene-propylene copolymer system.

FIG. 3 is a graph showing the relationship between resistance and temperature in a graphite-maleic acid-modified ethylene-propylene copolymer system.

FIG. 4 is a graph showing the relationship between specific resistance (R / R _o ) and strain in a graphite-maleic acid-modified ethylene-propylene copolymer system.

FIG. 5 is a graph showing the relationship between resistance and temperature in a graphite-styrene-hydrogenated butadiene rubber system.

FIG. 6 is a graph showing the relationship between specific resistance (R / R _o ) and strain in a graphite-ethylene-ethyl acrylate copolymer system (samples were prepared by a hot melt-hot press method).

FIG. 7 is a graph showing changes with time in specific resistance in a graphite-ethylene-ethyl acrylate copolymer system when 5% strain is applied.

FIG. 8 is a graph showing the relationship between resistance and temperature in a graphite-ethylene-ethyl acrylate copolymer system.

FIG. 9 is a graph showing the relationship between specific resistance (R / R _o ) and strain in a graphite-ethylene-ethyl acrylate copolymer system (sample was prepared by a coating method).

FIG. 10 is a graph showing changes with time in specific resistance in a graphite-ethylene-ethyl acrylate copolymer system when a 5% strain is applied.

FIG. 11 is a graph showing the relationship between resistance and temperature in a graphite-ethylene-ethyl acrylate copolymer system.

FIG. 12 is a graph showing the relationship between specific resistance (R / R _o ) and strain in a graphite-amorphous polyester resin system. .

FIG. 13 is a graph showing changes with time in specific resistance in a graphite-amorphous polyester resin system when a 5% strain is applied.

FIG. 14 is a graph showing the relationship between resistance and temperature in a graphite-amorphous polyester resin system.

FIG. 15 is a graph showing the relationship between specific resistance (R / R _o ) and strain in a graphite-amorphous polyester resin system.

FIG. 16 is a graph showing changes in specific resistance with time in a graphite-amorphous polyester resin system when a 5% strain is applied.

FIG. 17 is a graph showing the relationship between resistance and temperature in a graphite-amorphous polyester resin system.

FIG. 18 is a graph showing the relationship between specific resistance (R / R _o ) and strain in a graphite-amorphous polyester resin system.

FIG. 19 is a graph showing changes with time in specific resistance of a graphite-amorphous polyester resin system when a 5% strain is applied.

FIG. 20 is a graph showing the relationship between resistance and temperature in a graphite-amorphous polyester resin system.

FIG. 21 is a graph showing the relationship between specific resistance (R / R _o ) and strain in a graphite-styrene-hydrogenated butadiene-styrene block copolymer. .

FIG. 22 is a graph showing changes with time in specific resistance of a graphite-styrene-hydrogenated butadiene-styrene block copolymer when a 5% strain is applied.

FIG. 23 is a graph showing the relationship between resistance and temperature in a graphite-styrene-hydrogenated butadiene-styrene block copolymer.

FIG. 24 is a graph showing the relationship between specific resistance (R / R _o ) and strain in a graphite-styrene-hydrogenated isoprene-styrene block copolymer.

[Fig. 25] Fig. 25 is a graph showing changes with time in specific resistance of a graphite-styrene-hydrogenated isoprene-styrene block copolymer when a 5% strain is applied.

FIG. 26 is a graph showing the relationship between resistance and temperature in a graphite-styrene-hydrogenated isoprene-styrene block copolymer.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tetsuo Fujita             2478 Ose-cho, Hamamatsu City, Shizuoka Prefecture Chubu Processing Co., Ltd.             Inside the company F term (reference) 2F063 AA25 BA14 CA29 DA02 DA05                       EC01 EC04 EC21 EC26                 4J002 BB071 BP011 BP031 CF271                       DA026 DA036 DA066 DE186                       DJ056 FA066 FA116 FB006                       FD116 GQ00 GT00

Claims (11)

[Claims] 1. When the conductive particles are dispersed in a copolymer polymer and each component of the copolymer in the polymer alone forms a homopolymer, each component has different physical properties. Sensor made of a conductive particle-polymer system composed of a copolymer containing a. 2. The strain sensor according to claim 1, wherein the copolymer is a thermoplastic elastomer. 3. The strain sensor according to claim 1, wherein the copolymer is an ethylene-acrylate copolymer. 4. The conductive particle-polymer strain sensor according to claim 1, wherein the copolymer is a block copolymer having two or more components. 5. The conductive sensor-polymer strain sensor according to claim 4, wherein the copolymer is a styrene-diene block copolymer. 6. The strain sensor according to claim 5, wherein the copolymer is a hydrogenated styrene-diene copolymer. 7. The conductive particle according to claim 5, wherein the copolymer is a styrene-butadiene block copolymer.
A strain sensor based on a polymer. 8. The conductive particle according to claim 5, wherein the copolymer is a styrene-isoprene block copolymer.
A strain sensor based on a polymer. 9. A strain sensor based on a conductive particle-polymer system, wherein conductive particles are dispersed in a polymer, and the polymer component is composed of a modified homopolymer having unevenly distributed physical properties or a chemically modified homopolymer. 10. The strain sensor according to claim 9, wherein the homopolymer is a modified polyester resin. 11. The conductive sensor-polymer strain sensor according to claim 9, wherein the homopolymer is an amorphous polyester resin.