Title:
Carbon nanotube complex molded body and the method of making the same
Kind Code:
A1


Abstract:
A complex molded body of carbon nanotubes includes a matrix and carbon nanotubes arranged in a given direction in the matrix. The matrix is at least one organic polymer selected from the group consisting of thermoplastic resin, thermosetting resin, rubber, and thermoplastic elastomer. The complex molded body is produced by a method comprising the step of: providing a composition that includes a matrix and carbon nanotubes; applying a magnetic field to the composition to arrange the carbon nanotubes in a given direction; and hardening the composition to produce a complex molded body. The complex molded body has excellent anisotropy in terms of electrical property, thermal property, and mechanical property.



Inventors:
Tobita, Masayuki (Tokyo, JP)
Kimura, Toru (Tokyo, JP)
Yumura, Motoo (Ibaraki-ken, JP)
Ohshima, Satoshi (Ibaraki-ken, JP)
Ago, Hiroki (Ibaraki-ken, JP)
Uchida, Kunio (Ibaraki-ken, JP)
Kakudate, Yozo (Ibaraki-ken, JP)
Yokoi, Hiroyuki (Ibaraki-ken, JP)
Application Number:
10/097393
Publication Date:
05/22/2003
Filing Date:
03/14/2002
Assignee:
Polymatech Co., Ltd. (Senjyo Bldg., 4-8-16, Nihonbashi-honcho, Chuo-ku, Tokyo, JP)
Primary Class:
Other Classes:
428/336, 204/155
International Classes:
B82B1/00; B29C39/02; B82B3/00; C04B35/52; C04B35/524; C08J5/00; C08K3/04; C08K7/24; C08L101/00; (IPC1-7): C25B5/00
View Patent Images:
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Primary Examiner:
AHMED, SHEEBA
Attorney, Agent or Firm:
STOUT, UXA, BUYAN & MULLINS LLP (4 VENTURE, SUITE 300, IRVINE, CA, 92618, US)
Claims:
1. A complex molded body of carbon nanotubes comprising: a matrix; and carbon nanotubes arranged in a given direction in the matrix.

2. A complex molded body of claim 1, wherein the matrix is at least one organic polymer selected from the group consisting of thermoplastic resin, thermosetting resin, rubber, and thermoplastic elastomer.

3. A complex molded body of claim 1, wherein the matrix is metal, ceramic, other inorganic material, or a precursor thereof.

4. A complex molded body of claim 1, wherein the carbon nanotubes have a diameter of 1 to 20 nm and a length of 50 nm to 100 μm.

5. A complex molded body of claim 1, wherein the amount of the carbon nanotubes is 0.1 to 20 parts by weight relative to 100 parts by weight matrix.

6. A complex molded body of claim 1, further comprising graphitized carbon fibers.

7. A complex molded body of claim 1, wherein the carbon nanotubes have a ferromagnetic coating on their surface.

8. A method of making a complex molded body of carbon nanotubes comprising the steps of: providing a composition that includes a matrix and carbon nanotubes; applying a magnetic field to the composition to arrange the carbon nanotubes in a given direction; and hardening the composition to produce a complex molded body.

9. A method of claim 8, wherein the matrix is at least one organic polymer selected from the group consisting of thermoplastic resin, thermosetting resin, rubber, and thermoplastic elastomer.

10. A method of claim 8, wherein the matrix is metal, ceramic, other inorganic material, or a precursor thereof.

11. A method of claim 8, wherein the carbon nanotubes have a diameter of 1 to 20 nm and a length of 50 nm to 100 μm.

12. A method of claim 8, wherein the amount of the carbon nanotubes in said composition is 0.1 to 20 parts by weight relative to 100 parts by weight matrix.

13. A method of claim 8, wherein said composition further includes graphitized carbon fibers.

14. A method of claim 8, wherein the carbon nanotubes have a ferromagnetic coating on their surface.

15. A method of claim 8, wherein the magnetic field has a magnetic flux density from 5 to 20 tesla.

16. A method of claim 8, wherein the step of providing a composition includes injecting the composition into a recess of a forming mold.

17. A method of claim 10, wherein the step of hardening the composition includes cooling the composition.

18. A method of claim 8, wherein the step of hardening the composition includes drying and sintering the composition to carbonize or graphitize the matrix.

Description:

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a complex molded body where carbon nanotubes are arranged in a given direction in a matrix and a method of making the complex molded body. The molded body functions anisotropically in terms of electrical property, thermal property, mechanical property and may be used as electronic parts, thermally conductive material, and high-strength material.

[0002] Japanese Laid-Open Patent Publication No.5-125619 and Japanese Laid-Open Patent Publication No.7-216660 disclose a carbon nanotube and a method of making it. According the publications, development of many interesting applications, which use specific functions of carbon nanotube, such as an electron-emitting element, a hydrogen storage, a thin-film cell, a probe, a micromachine, semiconductor ultra large-scale integrated circuit, electrically conductive material, thermally conductive material, high-strength and high-elasticity material are actively examined.

[0003] A conventional complex molded body of carbon nanotube is obtained by blending carbon nanotubes in a matrix such as resin, rubber, metal, or ceramic and hardening the composition. In such a complex molded body, carbon nanotubes are basically dispersed at random in the matrix. Accordingly, resultant properties such as mechanical property, electrical property, electron-emitting property are randomly or equally provided. In other words, the conventional complex molded body is an isotropic material.

[0004] Carbon nanotubes in the matrix can be oriented in a flowing direction by molding the composition in a flowing field or shearing fields or by extending the composition. However, in these methods, carbon nanotubes can not be arranged in a thickness direction of the plate-like molded body. The direction of nanotubes can not be controlled in a desired direction.

[0005] Japanese Laid-Open Patent Publication No.11-194134 and Japanese Laid-Open Patent Publication No.10-265208 propose a carbon nanotube device and a method of carbon nanotube film respectively where carbon nanotubes are grown in a given direction in vapor on the catalytic molecules (such as iron, cobalt, nickel) arranged on the substrate. However, when the carbon nanotubes are arranged on the planar substrate by using these methods, only a device in which carbon nanotubes are arranged perpendicular to the substrate can be obtained. Therefore, to fabricate a device that has a desired form is difficult.

[0006] The object of the present invention is to provide a complex molded body of carbon nanotubes that has excellent anisotropic functions in terms of electrical property, thermal property, and mechanical property, and a method of making the complex molded body.

BRIEF SUMMARY OF THE INVENTION

[0007] The complex molded body of carbon nanotubes includes a matrix and carbon nanotubes that are arranged in the matrix in a given direction.

[0008] Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0009] The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

[0010] FIG. 1 is a schematic view of a complex molded body of carbon nanotubes of Example 1;

[0011] FIG. 2 is a cross-sectional view of forming molds in an opened position;

[0012] FIG. 3 is a cross-sectional view of forming molds where the composition is injected in a recess of a mold and two molds are closed together;

[0013] FIG. 4 is a cross-sectional view showing that, following FIG. 3, a pair of magnets are placed on both sides of the forming mold and a magnetic field is applied to the composition in the recess;

[0014] FIG. 5 is a schematic view of a complex molded body of carbon nanotubes of Example 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Embodiments of the present invention are described in detail below.

[0016] A complex molded body of carbon nanotubes is formed such that the carbon nanotubes are arranged in a matrix in a given direction. The complex molded body may be formed into a desired shape such as a plate, a tube, and a block to be used.

[0017] A type and a manufacturing method of the carbon nanotube for use in the present invention are not particularly limited so long as the carbon nanotube is made of carbon, it takes a tubular shape, and it has a diameter on the order of nanometer. For example, the carbon nanotubes manufactured by the methods disclosed in Japanese Laid-Open Patent Publication No.6-157016, Japanese Laid-Open Patent Publication No.6-280116, Japanese Laid-Open Patent Publication No.10-203810, and Japanese Laid-Open Patent Publication No.11-11917 may be used. An arc discharge process has become generally used for synthesis of carbon nanotubes. However, the use of a laser vaporization process, a thermal cracking process, and a plasma discharge process have recently been studied and carbon nanotubes produced by such processes.

[0018] A carbon nanotube has a structure of hexagonal networks of carbon atoms extending in tubular form. The nanotube that has one tubular layer is called single-wall nanotube (called SWNT hereinafter) while the nanotube that has a multiple of tubular layers is called multi-wall nanotube (called MWNT hereinafter). Structure of carbon nanotube is determined by a kind of synthesis process or various conditions during the process.

[0019] By-products, such as amorphous carbon nanoparticles, fullerenes, and metal nanoparticles, are produced together with carbon nanotubes, and such by-products may remain in the product. However, since fullerenes are soluble in organic solvents, such as toluene, carbon disulfide, benzene, and chlorobenzene, they can be extracted. Also, carbon nanoparticles and graphite pieces can be removed by forming selective inter-layer compounds of carbon nanoparticles and graphite pieces and sintering them at low temperature, based on the fact that interlayer distances between layers of carbon nanotubes are shorter than those of carbon nanoparticles and graphite pieces. The decrease in temperature inhibits decrement of carbon nanotubes due to combustion and thus improves a yield of the nanotubes.

[0020] Further, the carbon nanotubes are materials of high aspect ratio. Thus the product often has a complex intertwined structure, depending on the manufacturing process. In such cases, the carbon nanotubes may be dispersed by ultrasonic dispersion. Preferably, carbon nanotubes are pulverized under a predetermined condition and processed to yield shorter carbon nanotubes. The pulverization process may include, but is not limited to, dry pulverization processes such as shearing and grinding, and ball milling and a homogenizer that use a surfactant-containing water or an organic solvent.

[0021] The carbon nanotube for use in the present invention is not limited to SWNT or MWNT. Carbon nanotubes such as those containing metal or other inorganic or organic materials; those filled with carbon or other materials; coiled, spired, or fibrillary carbon nanotubes; or so-called nanofibers may also be used. Neither the diameters nor the lengths of the carbon nanotubes are limited. However, with regard to manufacturing facility and realization of anisotropic function, the carbon nanotubes preferably have a diameter from 1 to 20 nm and a length from 50 nm to 100 μm.

[0022] The matrix is a base material in which carbon nanotubes are blended. Examples of the matrix may include resin, rubber, thermoplastic elastomer, adhesive, paint, ink, metal, alloy, ceramic, cement, gel, paper, fiber, web, and nonwoven fabric. The matrix may be selected according to intended required characteristics of the complex molded body, such as hardness, mechanical strength, heat resistance, electrical properties, durability, and reliability. In particular, the matrix is preferably at least one organic polymer selected from the group consisting of thermoplastic resin, thermosetting resin, rubber, and thermoplastic elastomer, due to their molding capability.

[0023] Thermoplastic resin includes polyethylene, polypropylene, ethylene-α-olefin copolymer such as ethylene-propylene copolymer, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyvinyl acetal, fluoropolymers such as polyvinylidene fluoride and polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyacrylonitrile, styrene-acrylonitrile copolymer, ABS resin, polyphenylene ether (PPE) resin and modified PPE resin, aliphatic and aromatic polyamide, polyimide, polyamide imide, polymethacrylic acid and polymethacrylates such as polymethyl methacrylate, polyacrylic acids, polycarbonate, polyphenylene sulfide, polysulfone, polyether sulfone, polyether nitrile, polyether ketone, polyketone, liquid crystal polymer, silicone resin, and ionomer.

[0024] The thermosetting resin includes epoxy resin, phenol resin, acrylic resin, urethane resin, polyimide resin, unsaturated polyester resin, diallyl phthalate resin, dicycropentadiene resin, and benzocyclobutene diene. The methods of hardening the thermosetting resin are not limited to thermosetting but include ordinary hardening methods, such as light setting and moisture setting.

[0025] The rubber may be natural rubber or synthetic rubber. Synthetic rubbers may include butadiene rubber, isoprene rubber, styrene-butadiene copolymer rubber, nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, ethylene-propylene rubber, chlorinated polyethylene, chlorosulfonated polyethylene, butyl rubber and butyl rubber halide, fluorine rubber, urethane rubber, and silicone rubber.

[0026] The thermoplastic elastomer includes styrene-butadiene or styrene-isoprene block copolymers and hydrogenated polymer thereof, styrene thermoplastic elastomer, olefin thermoplastic elastomer, vinyl chloride thermoplastic elastomer, polyester thermoplastic elastomer, polyurethane thermoplastic elastomer, and polyamide thermoplastic elastomer. Thermoplastic resin and thermoplastic elastomer are particularly preferred since they are recyclable.

[0027] The matrix preferably contains at least one material selected from the group consisting of silicone rubber, epoxy resin, polyimide resin, bis-maleimide resin, benzocyclobutene resin, fluororesin, and polyphenylene ether resin. More preferably, the matrix contains at least one material selected from the group consisting of silicone rubber, epoxy resin, and polyimide resin in terms of reliability.

[0028] A polymer alloy of the above-mentioned organic polymers, as well as additives including a known plasticizer, a filler, a hardener, organic fiber such as carbon fiber, glass fiber, and aramid fiber, a stabilizer, a colorant may also be mixed in the matrix.

[0029] To facilitate mixing of carbon nanotubes with the matrix or arrangement of carbon nanotubes in the matrix, an organic solvent such as methylene chloride or water may be added to decrease the viscosity of the composition. Further, a dispersion and stabilization agent such as a surfactant may be used to improve dispersion.

[0030] The amount of carbon nanotubes mixed in the matrix is preferably 0.01 to 100 parts by weight relative to 100 parts by weight matrix. When the amount is less than 0.01 parts by weight, the composition has inadequate anisotropic function. When the amount is more than 100 parts by weight, dispersion of carbon nanotubes in the matrix is worsen. The amount of carbon nanotubes mixed in the matrix in which the nanotubes can be arranged by a magnetic field and the composition exhibit achieves the effective anisotropic function is conveniently 0.1 to 20 parts by weight, although the amount may vary depending on a kind of matrix material, other additives, or strength of magnetic field used.

[0031] Further, to improve wettability or adhesion of the carbon nanotubes to the matrix, the surface of the carbon nanotubes is preferably pretreated with degreasing, washing, or activation process such as UV-radiation, corona discharge, plasma treatment, flaming treatment, and ion implation. In addition, after these surface treatments, the surface can be treated with a coupling agent such as a silane-containing agent, a titanium-containing agent, and an alminum-containing agent. This facilitates the filling of more carbon nanotubes, so that the resultant complex molded body functions more effectively.

[0032] A dispersing method of carbon nanotubes in the matrix is not particularly limited. For example, when the matrix is a liquid polymer, carbon nanotubes may be mixed in the matrix at a certain amount with a usual mixer or a usual blender. Ultrasonic or vibration may further be applied to improve dispersion of carbon nanotubes. Preferably, degas process is conducted to remove entrained air under vacuum or with pressure.

[0033] When the matrix is a solid polymer in the form of pellet or powders, carbon nanotubes may be mixed in the matrix at a certain amount with a usual mixing machine, such as an extruder, a kneader, or a roller.

[0034] The strength of the magnetic field applied to the carbon nanotubes sufficient to arrange them in a given direction is a magnetic flux density from 0.05 to 30 tesla. When the magnetic flux density is less than 0.05 tesla, carbon nanotubes can not be arranged in a given direction sufficiently. When the density is more than 30 tesla, the magnetic field is too strong to improve the arrangement further. Although the magnetic flux density is experimentally determined from types or amount of the matrix and the carbon nanotubes, an intended shape of complex molded body, and required characteristics of end products, the practical range of magnetic flux density for arranging carbon nanotubes effectively is from 5 to 20 tesla.

[0035] A device for producing an external magnetic field is, for example, a permanent magnet, an electromagnet, and a coil. In the present invention, carbon nanotubes have diamagnetism and they can be arranged in the direction parallel to magnetic lines of force. Therefore, to apply the magnetic field properly, a north pole and a south pole of magnets may be placed corresponding to a desired arrangement direction of tubes. Alternatively, a north pole and a north pole of magnets may be placed so as to face to each other. Or a magnet may be placed only one side of the composition. Further, magnets may be placed such that magnetic lines of force are curved. That is, a magnetic field may be applied in any way so long as the magnetic lines of force are adjusted to achieve the aimed anisotropic function.

[0036] The composition may then be molded into a desired shape, such as a plate, a tube, or a block by press molding, extrusion molding, transfer molding, calendering molding, to form a complex molded body. The composition may be further processed into a thin film by processes such as painting and printing. Thus, the resultant carbon nanotube complex molded body includes carbon nanotubes that are arranged in a given direction. This can be confirmed in an enlarged picture with an electron microscope.

[0037] The complex molded body of the present invention is anisotropic in terms of carbon nanotube-specific properties, such as electrical property, thermal property, and mechanical property. In other words, the complex molded body has different degrees of such properties at different directions.

[0038] For electrical property, the complex molded body of the present invention has high electrical conductivity in a certain direction. In addition, this molded body exhibits higher conductivity with a smaller amount of carbon nanotubes compared with a molded body in which carbon nanotubes are not arranged in a given direction. The electron emission of carbon nanotubes is believed to be most efficient at the end of nanotubes. According to the invention, carbon nanotubes may be placed so that a larger number of ends of carbon nanotubes are placed at the edge of the complex molded body.

[0039] For thermal property, when the carbon nanotubes are arranged in a thickness direction of a plate-like molded body, thermal conductivity in a direction parallel to the arrangement direction of the nanotubes is different from that in a direction perpendicular to the same. Since the carbon nanotubes have greater thermal conductivity in their axial direction than that in a direction perpendicular to the axial direction, the above plate-like molded body has greater thermal conductivity in a thickness direction, which allows the molded body to be anisotropic. In this case, the carbon nanotubes are preferably graphitized to improve thermal conductivity.

[0040] For mechanical property, when the carbon nanotubes are arranged in a thickness direction of a plate-like molded body, anisotropic elasticity is obtained. The tensile strength and bending strength in the thickness direction are improved.

[0041] Besides, the complex molded body of the present invention may be anisotropic in terms of magnetic property, electromagnetic property, linear expansion coefficient, dielectric property, and wave-absorbing property. Thus, the molded body may be used for various applications such as a damping material and a wave-absorber.

[0042] The advantages of the above embodiments are described below.

[0043] In the embodiments, carbon nanotubes are arranged in a given direction. Thus, properties (such as electrical property, thermal property, and mechanical property) of the molded body in a direction in which the carbon nanotubes extend is different from those in other directions. This allows the complex molded body to have excellent anisotropic functions that have never been achieved. Moreover, since microscopic carbon nanotube is a minute material, such anisotropic functions can be achieved in a minute complex molded body.

[0044] In addition, the complex molded body may be anisotropic in terms of magnetic property, electromagnetic property, linear expansion coefficient, dielectric property, and wave-absorbing property. Accordingly, the complex molded body may be used for various applications such as a pressure sensor, a sensing switch, a magnetic shield material, magnetic recording material, and a magnetic filter.

[0045] With respect to the above embodiments, a magnetic field may be applied to the composition that includes carbon nanotubes. Thus, the carbon nanotubes may be arranged in a given direction in the matrix effectively.

EXAMPLE

[0046] The above embodiments will be described by way of examples. Although the description is made on a plate-like complex molded body in Examples and Comparative examples, the invention is not limited in any way by the examples.

[0047] In each example, carbon nanotubes were synthesized by a thermal cracking process using a catalyst, which is an example of synthetic method of carbon nanotubes. The cracking process is almost equal to carbon fiber vapor phase epitaxy and will be described below.

[0048] Firstly, ethylene or propane as a source gas is introduced into a thermostat together with hydrogen. A source gas may be saturated hydrocarbons such as methane, ethane, butane, hexane, and cyclohexanone; unsaturated hydrocarbons such as propylene, benzene, toluene; and oxygen-containing material such as acetone, methanol, and carbon monoxide.

[0049] Next, the source gas introduced into a thermostat is heated or cooled to control a vapor pressure. Then the gas is further introduced with hydrogen gas into a thermal cracking reactor, where ethylene or propane as a source gas is cracked to yield carbon nanotubes.

Example 1

[0050] A manufacturing device and a manufacturing method for making a plate-like complex molded body are described with reference to FIGS. 1 to 4.

[0051] As shown in FIG. 2, a pair of forming molds 1a, 1b is placed to oppose to each other. A forming recess 2 is provided in the opposing surface of the forming mold 1a. The recess 2 matches to a intended plate-like complex molded body. Both of the mold 1a, 1b are formed of aluminum. The surface of the recess 2 is coated with fluororesin.

[0052] A composition 3 was prepared by adding 1 part by weight of carbon nanotubes to 100 parts by weight of thermosetting unsaturated polyester resin (NIPPON SHOKUBAI CO., Ltd., a trade name of EPOLAC™ G-157 MB) and stirring. The composition 3 was filled in the recess 2.

[0053] As shown in FIG. 3, the molds 1a, 1b were closed together at a certain pressure to seal the recess 2. Then, as shown in FIG. 4, a pair of magnets 4a, 4b was placed on either side of the molding 1a, 1b. A north pole N of the magnet 4a and a south pole S of the magnet 4b were opposed to each other. A magnetic field of 10 tesla was applied in a direction parallel to an inner bottom face of the recess 2. Then the composition 3 was left for 30 minutes at room temperature to be hardened. After that, the mold 1a, 1b were opened to remove a plate-like complex molded body 5 of carbon nanotubes from the recess 2.

[0054] As seen in FIG. 1, the carbon nanotubes 6 in the resultant complex molded body 5 were arranged in a direction parallel to upper and lower faces of the mold 1a, 1b.

Example 2

[0055] A complex molded body 5 was obtained as in Example 1, except that a magnetic field of 10 tesla was applied in a direction perpendicular to an inner bottom face of the recess 2. As seen in FIG. 5, The carbon nanotube 6 in the resultant complex molded body 5 were arranged in a direction perpendicular to upper and lower faces of the complex molded body 5.

Example 3

[0056] A composition 3 was prepared by adding 1 part by weight of carbon nanotubes to 100 parts by weight of thermosetting epoxy resin (Epoxy Technology, Inc., a trade name of EPO-TEK310) and stirring. The composition 3 was filled in the recess 2 of the mold 1a shown in FIG. 2. Following the procedures as in Example 1, a complex molded body 5 was obtained.

Example 4

[0057] A composition 3 was prepared by adding 2 parts by weight of carbon nanotubes to 100 parts by weight of thermosetting epoxy resin (Epoxy Technology, Inc., a trade name of EPO-TEK310) and stirring. The composition 3 was filled in the recess 2 of the mold 1a shown in FIG. 2. Following the procedures as in Example 1, a complex molded body 5 was obtained.

Example 5

[0058] A composition was prepared by adding 1 part by weight of carbon nanotubes to 100 parts by weight of thermoplastic polycarbonate resin (MITSUBISHI ENGINEERING-PLASTICS CORPORATION, a trade name of Iupilon™ S-2000) and mixing with a screw extruder. Then methylene chloride was added to the composition and the mixture was stirred until the mixture became a uniform liquid. The resultant liquid was filled in the recess 2 of the mold 1a shown in FIG. 2. While a magnetic field of 10 tesla was applied in a direction parallel to an inner bottom face of the recess 2, the liquid was thermally hardened at 120 degrees C. for an hour to obtain a complex molded body 5.

Example 6

[0059] A complex molded body 5 was obtained as in Example 5, except that a magnetic field of 10 tesla was applied in a direction perpendicular to an inner bottom face of the recess 2.

Comparative Example 1

[0060] A composition was prepared by adding 1 part by weight of carbon nanotubes to 100 parts by weight of thermosetting unsaturated polyester resin (NIPPON SHOKUBAI CO., Ltd., a trade name of EPOLAC™ G-157 MB) and stirring. The composition was filled in the recess 2. Then, without a magnetic field applied, the composition was left for 30 minutes at room temperature to be hardened to form a complex molded body. The carbon nanotubes were randomly dispersed in the complex molded body.

Comparative Example 2

[0061] A composition was prepared by adding 1 part by weight of carbon nanotubes to 100 parts by weight of thermosetting epoxy resin (Epoxy Technology, Inc., a trade name of EPO-TEK310) and stirring. The composition was filled in the recess 2 of the mold 1a shown in FIG. 2. Then, without a magnetic field applied, the composition was left for 30 minutes at room temperature to be hardened to form a complex molded body.

Comparative Example 3

[0062] A composition was prepared by adding 2 parts by weight of carbon nanotubes to 100 parts by weight of thermosetting epoxy resin (Epoxy Technology, Inc., a trade name of EPO-TEK310) and stirring. The composition was filled in the recess 2 of the mold 1a shown in FIG. 2. Then, without a magnetic field applied, the composition was left for 30 minutes at room temperature to be hardened to form a complex molded body.

Comparative Example 4

[0063] A pellet was prepared by adding 1 part by weight of carbon nanotubes to 100 parts by weight of thermoplastic polycarbonate resin (MITSUBISHI ENGINEERING-PLASTICS CORPORATION, a trade name of Iupilon™ S-2000) and mixing with a screw extruder. Then 70 parts by weight of methylene chloride was added to 100 parts by weight of the pellet and the mixture was stirred until the pellet was completely dissolved. The resultant liquid was filled in the recess 2 of the mold 1a shown in FIG. 2. Then, without a magnetic field applied, the liquid was thermally hardened at 120 degrees C. for an hour to obtain a complex molded body.

[0064] For complex molded bodies obtained in Examples 1, 2, 5, and 6 and Comparative examples 1 and 4, storage modulus E′, loss modulus E″, loss tangent tan δ at a frequency of 11 Hz were measured using a dynamic viscoelasticity measuring system (ORIENTECH CO., Ltd., a trade name of RHEOVIBRON DDV-III). The results were shown in Table 1. 1

TABLE 1
amountE′E″
(part by wt)direction(N/m2)(N/m2)tan δ
Ex. 11parallel 1.8 × 105 2.4 × 1040.13
Ex. 21perpendicular 1.2 × 1050.89 × 1040.074
Ex. 51parallel 1.5 × 106 2.2 × 1040.14
Ex. 61perpendicular0.92 × 1060.78 × 1040.085
Comp. 11no 1.1 × 1050.87 × 1040.078
Comp. 21no0.95 × 1060.80 × 1040.084

[0065] Aside from the above measurement, for complex molded bodies obtained in Examples 3, 4 and Comparative examples 2, 3, magnetic susceptibility χ from 0 to 5 T was measured using a SQUID susceptibility measurement system (Quantum Design, Model MPMS-7). The results were shown in Table 2. In Tables 2 to 4 below, measurement direction means the following:

[0066] Parallel: sample was measured in a direction parallel to the direction in which the carbon nanotubes extend.

[0067] Perpendicular: sample was measured in a direction perpendicular to the direction in which the carbon nanotubes extend.

[0068] No: sample in which the carbon nanotubes were randomly dispersed were measured. 2

TABLE 2
amountmeasurement
(part by wt)directionχ (/g)|Δχ| (/g)
Ex. 31parallel−6.4 × 10−51.2 × 10−5
perpendicular−7.5 × 10−5
Ex. 42parallel−8.2 × 10−51.0 × 10−6
perpendicular−8.3 × 10−5
Comp. 21no−7.0 × 10−5
Comp. 32no−8.2 × 10−5

[0069] Further, for complex molded bodies obtained in Example 3 and Comparative example 2, electric resistance was measured. The results were shown in Table 3. Electric resistance is a measured voltage across the two terminals, when a direct current of 1 mA is passed through and the distance between the terminals is 1 mm. 3

TABLE 3
amountmeasurement
(part by wt)directionresistance (Ω)
Ex. 31parallel17.8 × 103
perpendicular1.14 × 103
Comp. 21no6.06 × 103

[0070] For complex molded bodies obtained in Example 1 and Comparative example 2, linear expansion coefficient at from 30 to 200 degree C. was measured using a thermomechanical analyzer (Mettler, TMA-40, TA-3000). The results were shown in Table 4. 4

TABLE 4
amountmeasurementlinear expansion
(part by wt)directioncoefficient (/degree C.)
Ex. 11parallel1.45 × 10−4
perpendicular1.70 × 10−4
Comp. 21no1.57 × 10−4

[0071] Particularly, variations in magnetic susceptibility χ, or the absolute value of the difference between the magnetic susceptibility in a parallel direction and that in a perpendicular direction |Δχ|, of Table 2 show that Example 3 has magnetic anisotropy. Variations in electric resistance of Table 3 show that Example 3 has anisotropy of electric resistance. Variations in linear expansion coefficient show that Example 1 has anisotropy of linear expansion coefficient. In addition, Table 1 showed that the molded body of Example 1 has greater storage modulus E′ and loss modulus E″ in a parallel direction than in a perpendicular direction, indicating that the molded body of Example 1 has an excellent elasticities in a direction parallel to the upper and lower faces of the molded body.

[0072] It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the invention may be embodied in the following forms.

[0073] The magnetic field applied to the composition 3 may be oriented in an oblique direction relative to the inner bottom face of the recess 2 of the mold 1a.

[0074] A coating of ferromagnetic material may be formed on the surface of the carbon nanotubes to arrange them effectively. This facilitates the anisotropic functions of the molded body.

[0075] Carbon fibers, such as graphitized carbon fibers, may be mixed with the carbon nanotubes. This facilitates the anisotropy functions in terms of thermal conductivity and electro-isolative property.

[0076] Metals, ceramics, other inorganic materials, or precursors thereof may be used as a matrix. In such cases, a magnetic field is applied to the matrix that is melted or dispersed in a solvent. The matrix is then cooled to be hardened or dried or sintered to be hardened to form a complex molded body. For example, an aluminum-alloy composition including carbon nanotubes is melted in a container that has a predetermined shape. Then a magnetic field is applied to the composition to arrange the carbon nanotubes in a given direction. The composition is then cooled and hardened to form a complex molded body. This manufacturing method provides a resultant molded body with required characteristics such as hardness and anisotropy in terms of mechanical strength, heat resistance, electrical properties, and durability.

[0077] The matrix may be carbonized or graphitized. For example, the composition including phenol resin or epoxy resin as a matrix and carbon nanotubes is melted in a container that has a predetermined shape. Then a magnetic field is applied to the composition to arrange the carbon nanotubes in a given direction. The composition is then dried and sintered to carbonize or graphitize the matrix, thereby forming a complex molded body. This manufacturing method provides a resultant molded body with required characteristics such as hardness and anisotropy in terms of mechanical strength, heat resistance, electrical properties, and durability.

[0078] Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.





 
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