WO2008120830A1

WO2008120830A1 - Composition for source particle of high-temperature typed bipolar plate for fuel cell and high-temperature typed bipolar plate for fuel cell manufactured by using the same

Info

Publication number: WO2008120830A1
Application number: PCT/KR2007/001558
Authority: WO
Inventors: Hyun Min Kang; In-Su Han; Chan Lim
Original assignee: Gs Caltex Corporation
Priority date: 2007-03-30
Filing date: 2007-03-30
Publication date: 2008-10-09
Also published as: KR101035187B1; JP2010524171A; KR20100005700A; JP5208199B2

Abstract

Disclosed herein is a source composition of high-temperature type bipolar plate for a fuel cell, the source composition comprising 100 parts by weight of a graphite powder; 0.2 to 10 parts by weight of a carbon black; and 0.1 to 40 parts by weigh of a cyanate ester resin, and a high-temperature type bipolar plate for a fuel cell manufactured by using the source composition. The high-temperature type bipolar plate for a fuel cell having a high thermal stability and durability in the range between 120 and 400°C can be obtained by using the source composition.

Description

COMPOSITION FOR SOURCE PARTICLE OF HIGH-TEMPERATURE TYPED BIPOLAR PLATE FOR FUEL CELL AND HIGH-TEMPERATURE TYPED BIPOLAR PLATE FOR FUEL CELL MANUFACTURED BY USING

THE SAME

Technical Field

The present invention relates to a source composition of high-temperature type bipolar plate for a fuel cell and a high-temperature type bipolar plate for a fuel -cell manufactured by using the same, and more particular, to a source composition of high- temperature type bipolar plate for a fuel cell and a high-temperature type bipolar plate for a fuel cell manufactured by using the same, which exhibits an improved high- temperature stability and durability.

Background Art In general, a fuel cell is referred to as an electrochemical apparatus for directly exchanging chemical energy, which is generated from the fuel such as hydrogen, methanol or the like, to electric energy. In fuel cells using hydrogen as a fuel, oxidation reaction of hydrogen and reduction reaction of oxygen occurs, thereby resulting in generating of electricity and water. The fuel cells have a high efficiency and use a variety of fuels. For these reasons, the fuel cells are current in the spotlight as one of the future energy source.

Specifically, polymer electrolyte membrane fuel cell (PEMFC) can reduce the release of air pollutants such as carbon dioxide, etc., into the environment, and is operated at relatively low temperature of 80⁰C in comparison with other fuel cells. In addition, since it has high-current density and uses a polymer electrolyte, there is no corrosion of electrodes and electrolyte loss, and has high generation efficiency.

In a basic structure of the polymer electrolyte membrane fuel cell, a porous anode and cathode, which are coated with Pt or Pt-Ru catalyst, are mounted at both sides around the polymer electrolyte membrane, and a separator which serves as a path for reactive gases and a current collector are placed outside of the anode and the cathode.

Specifically, an electrolyte membrane is disposed between the fuel anode and the air cathode prepared as described above, and then the fuel anode and the air cathode are hot-pressed under a certain pressure at a glass transition temperature (Tg) of the electrolyte membrane or higher, thereby providing membrane electrode assembly (MEA). Thereafter, the separator is disposed at the outside of the MEA.

The separator is also referred to as a bipolar plate or a channel plate. A gas channel of a fuel electrode is formed on a surface of the separator and a gas channel of an air electrode is formed on another surface of the separator.

Hydrogen, which is a fuel, enters the gas channel of the anode and oxygen or air, which is an oxidizer, is introduced into the gas flow channel of the cathode. An electrical energy is generated on the electrodes by an electrochemical oxidation of the fuel gas introduced and an electrochemical reduction of the oxidizer introduced.

In addition, the separator provides channels for supplying the fuel and the oxidizer, functions as a current collector conducting electrons produced at the anode to the cathode, and removes water generated during an operation of the fuel cell.

Additionally, the separator is a main body supporting the MEA and allows a stack to be formed. The separator used in the stack removes heat of reaction and thus functions as a cooling water channel.

The cooling water channel is formed in all separators used in the stack or only in a part of the separators. The separator with the formed cooling water channel is supplied with the fuel at one side thereof and the oxidizer at the opposite side thereof, and the cooling water is supplied to the middle of the separator.

Herein, the separator is accomplished by joining two plates, each of which has a gas channel on a surface thereof and a cooling water channel on another surface thereof, with the surfaces having the cooling water channel facing each other.

The separator prepared as described above should be light while maintaining strength, and have excellent electrical conductivity for effectively transporting electrons being produced, corrosion resistance and firmness, and a long lifetime.

Further, the separator should supply humidified reacting gases, and remove water produced by an electrochemical reaction without fail.

A metal separator, a graphite separator, and the like, are used as the separator. However, the metal separator has a limitation in use due to problems in its production, and corrosion. The graphite separator has a disadvantage of high processing cost for forming the channels thereon by machining, and accordingly, in order to overcome the above mentioned problems, there has been actively developed a study of a polymer composite separator. The polymer compound resin separator is prepared via compression molding or injection molding after mixing graphite powder and polymer resin, and the separator having channels can be manufactured without machining. A general polymer electrolyte membrane fuel cell using the polymer compound resin separator is operated at a temperature of less than 100⁰C. Here, when the operation temperature is up to a temperature of 120 to 15O⁰C, a membrane humidification step may be removed as conductivity of hydrogen ion of the membrane increases, and an amount of a catalyst and CO poisoning can be reduced as the activity of catalyst increases.

However, a polymer compound resin separator of a conventional polymer electrolyte membrane fuel cell has a problem in that mechanical properties such as flexural strength and modulus and the like is significantly deteriorated at a temperature of 100 to 15O⁰C, thereby failing to function as a separator, although it is stably operated at the temperature lower than 100⁰C. Specifically, a separator with a conventional polymer constituent or amount formed thereon cannot be smoothly operated at high temperatures. Accordingly, there is a need for developing materials having high- temperature stability and excellent durability. Disclosure of Invention Technical Goals

An aspect of the present invention provides a source composition of a high- temperature type bipolar plate for a fuel cell, and a high-temperature type bipolar plate for a fuel cell manufactured by using the same, and more particular, to a source composition of high-temperature type bipolar plate for a fuel cell, and a high- temperature type bipolar plate for fuel using the same, which exhibits an improved high-temperature stability and durability. Technical solutions

According to an aspect of the present invention, there is provided a source composition of high-temperature type bipolar plate for a fuel cell comprises: 100 parts by weight of a graphite powder, 0.2 to 10 parts by weight of a carbon black, and 0.1 to 40 parts by weigh of a cyanate ester resin.

Also, according to an aspect of the present invention, there is provided a source composition of high-temperature type bipolar plate for a fuel cell, wherein the graphite powder comprises columnar graphite particles having an aspect ratio in the range between 1.5 and 2.

According to an aspect of the present invention, there is provided a source composition of high-temperature type bipolar plate for fuel cell, wherein the carbon black has a specific surface area of 50 to 100 m²/g.

According to another aspect of the present invention, there is provided a source composition of high-temperature type bipolar plate for fuel cell, wherein the cyanate ester resin comprises at least one resin selected from a group consisting of a phenol novolac-based cyanate ester resin, a biphenol-based dicyanate ester resin, bisphenol A- based dicyanate ester resin, a bisphenol E-based dicyanate ester resin, and a bisphenol F-based dicyanate ester resin.

According to an aspect of the present invention, there is provided a source composition of high-temperature type bipolar plate for fuel cell, further comprising 0.05 to 20 parts by weight of an epoxy resin, wherein the cynate ester resin is used in an amount of 0.05 to 20 parts by weight.

In addition, according to an aspect of the present invention, there is provided a source composition of high-temperature type bipolar plate for fuel cell, further comprising 0.01 to 1 parts by weight of a hardening catalyst. According to an aspect of the present invention, there is provided a source composition of high-temperature type bipolar plate for fuel cell, wherein the hardening catalyst comprises at least one hardening catalyst selected from a group of transition metal complexes of acetylacetonate, octoate, and naphthenate types, the group of transition metal complexes consisting of a metal material such as copper, manganese, plumbum, nickel, zinc and etc.

According to an aspect of the present invention, there is provided a source composition of high-temperature type bipolar plate for fuel cell, further comprising 0.1 to 3 parts by weight of a release agent, wherein the release agent uses a carnauba wax and the like. According to an aspect of the present invention, there is provided a high- temperature type bipolar plate for a fuel cell having a cross-linked structure of phenolic triazine. According to still another aspect of the present invention, there is provided a high-temperature type bipolar plate for a fuel cell, wherein the cross-linked structure of phenolic triazine is formed with a phenolic cynate ester polymer having been thermally crosslinked. According to an aspect of the present invention, there is provided a high- temperature type bipolar plate for a fuel cell, further comprising an oxazoline structure formed by reacting an epoxy group and a cynate ester group. Brief Description of Drawings

FIG. 1 is a cross-sectional schematic view illustrating an apparatus for preparing source particles of a separator for a fuel cell according to an exemplary embodiment of the present invention. Best Mode for Carrying Out the Invention

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.

A source composition of high-temperature type bipolar plate for fuel cell according to an embodiment of the present invention comprises a graphite powder, a carbon black, a cyanate ester resin, an epoxy resin, a hardening catalyst, and a release agent. The graphite powder uses a primary artificial graphite having a columnar crystal structure (i.e., blocky crystal structure) whose aspect ratio is in a range between 1.5 and 2, which is different from a lamellar crystal structure.

When the graphite having a columnar or blocky crystal structure is used, flexural deformation of a bipolar plate is significantly reduced, thereby exhibiting excellent formation property upon forming a stack, and improving stability upon manufacturing a fuel cell.

Preferably, the graphite powder has an average particle size of from 50 to 150 μm, and a relatively narrow particle distribution.

Further, the graphite powder purity is preferably above 99.5% when considering long term durability of a bipolar plate to be manufactured, and ash and metal amount are preferably smaller.

The carbon black is used for reducing penetration resistance of the bipolar plate, and preferably has a specific surface area of from 50 to 100 m²/g. Here, when the specific surface area is less than 50 m²/g, a small reduction in the penetration resistance arises. Conversely, when the specific surface area is greater than 100 m²/g, it is difficult to achieve a uniform distribution when manufacturing the source particles, thereby deteriorating mechanical properties of the bipolar plate.

Also, the carbon black preferably contains an amount less than about 0.1% by weight of ash.

The source composition comprises 0.2 to 10 parts by weight of the carbon black based on 100 parts by weigh of the graphite powder. When the amount of the carbon black is less than 0.2 parts by weight, the penetration resistance of the bipolar plate to be manufactured is significantly increased. Conversely, when the amount of the carbon black is more than 10 parts by weight, flexural strength of the bipolar plate is significantly reduced, and a hardening reaction of the polymer is adversely affected, thereby deteriorating processability. Accordingly, the amount of the carbon black is 0.2 to 10 parts by weight based on 100 parts of the graphite powder, and preferably 2 to

5 parts by weight.

The cyanate ester resin comprises a phenol novolac-based cyanate ester resin, a biphenol-based dicyanate ester resin, bisphenol A-based dicyanate ester resin, a bisphenol E-based dicyanate ester resin, a bisphenol F-based dicyanate ester resin, and the like.

A dimethyl bisphenol A dicyanate resin and tetra ortho methyl bisphenol F dicyanate resin, in which methyl group is substituted in a benzene ring, may be used. The cyanate ester resin may be used alone or in a mixture thereof.

The cyanate ester resin is used in an amount of from 0.1 to 40 parts by weight based on 100 parts by weight of the graphite powder. Here, when the cynate ester resin is used in an amount of 0.1 parts by weigh or less, based on 100 parts by weight of the graphite, mechanical properties of the bipolar plate to be manufactured is significantly deteriorated and the flexural strength is reduced. Conversely, when the cynate ester resin is used in an amount of 40 parts by weight or more, the penetration resistance of the bipolar plate is significantly increased.

Although any polymer resin containing an epoxy group may be used as the epoxy resin, especially polymer resins containing a phenol group are preferable considering a heat stability. A phenol novolac-based epoxy resin, a cresol novolac- based epoxy resin, an epoxy resin containing naphthalene ring, phenol aralkly-based epoxy resin, biphenyl-based epoxy resin, substituted epoxy resin, bisphenol A-based epoxy resin, bisphenol F-based epoxy resin and the like can be used as the epoxy resin. The epoxy resin may be used with the cynate ester resin, and may be used within 40 parts by weight of total polymer based on 100 parts by weight of the graphite powder.

For example, when 0.05 to 20 parts of weight of the cynate ester resin is used, an amount of 0.05 to 20 parts by weight of the epoxy resin is used. In consideration of the penetration resistance of the bipolar plate, when mixing the cynate ester resin and the epoxy resin, less than 40 parts by weight of the total polymer is preferable.

When mixing the cynate ester resin and the epoxy resin, an additional epoxy hardening catalyst is not used. However, a hardening catalyst such as an imidazole- based compound, an organic phosphate compound, a secondary (tertiary) amine, and a quaternary ammonium salt is used for effective hardening.

An imidazole, 2-ethyl imidazole, 2-ethyl-4-methyl imidazole, 2-phenyl imidazole, 2-undecyl imidazole, 1 -benzyl-2methyl imidazole, 2-hepta decyl imidazole, 4,5-diphenyl imidazole, 2-methyl imidazoline, 2-phenyl imidazoline, 2-undecyl imidazoline, 2-hepta decyl imidazoline, 2-isopropyl imidazoline, 2,4-dimethyl imidazole, 2-phenyl-4-methyl imidazole, 2-ethyl imidazoline, 2-isopropyl imidazoline, 2,4-dimethyl imidazoline and 2-phenyl-4-methyl imidazoline can be used as an imidazole-based compound.

A tripheyl phosphine, and the like, can be used as the organic phosphate compound. A piperidine, and the like, can be used as the secondary amine, a dimethyl benzyl amine, tris (dimethyl amino methyl) phenol, and the like, can be used as the tertiary amine, and a tetra butyl ammonium bromide, tetra butyl ammonium chloride, and the like, can be used as the quaternary ammonium salt.

The hardening catalyst comprises 0.05 to 20 parts by weight of the cyanate ester resin, based on 100 parts by weight of the graphite powder. When the epoxy resin is used in an amount of 0.05 to 20 parts by weight, the hardening catalyst is used in an amount of 0.001 to 1 parts by weight. When the hardening catalyst is used in an amount less than 0.001 parts by weight, an effect in using the hardening catalyst cannot be sufficiently shown. Conversely, when the hardening catalyst is used in an amount greater than 1 part by weight, it leads to an excessive crosslinked density.

The hardening catalyst uses transition metal complexes, which is a catalyst, of acetylacetonate, octoate, and naphthenate types. The group of transition metal complexes consists of a metal material such as cobalt, copper, manganese, plumbum, nickel, and zinc. Cobalt acetylacetonate, manganic acetylacetonate, zinc acetylacetonate, copper acetylacetonate, nickel acetylacetonate, titanyl acetylacetonate, manganese octoate, cobalt octoate, zinc octoate, ferric octoate, tin octoate, lead naphthenate, manganese naphthenate, cobalt naphthenate, zinc naphthenate, cupric naphthenate, and the like, may be used as a hardening catalyst.

The hardening catalyst is used in an amount of 0.01 to 1 parts by weight, when the cynate ester resin is used in an amount of 0.1 to 40 parts by weight based on 100 parts by weight of the graphite powder. When the hardening catalyst is used in an amount less than 0.01 parts by weight, an effect obtained when using the hardening catalyst cannot be sufficiently shown. Conversely, when the hardening catalyst is used in an amount greater than 1 part by weight, and metal ion is eluted from the bipolar plate for fuel cell, thereby causing performance deterioration of the fuel cell.

A carnauba wax, and the like, are used as the release agent. The release agent functions to allow the bipolar plate to be readily removed from a mold upon compression molding or injection molding of the bipolar plate.

Since the carnauba wax provides a releasing property while exerting no influence on hardening of polymer unlike a PE wax, an Oxidized PE wax, etc., it is suitable for preparing powdery source particles of a bipolar plate which is manufactured by a process including a crosslinked reaction in the same manner as the present invention.

The release agent is used in an amount of 0.1 to 3 parts by weight based on 100 parts by weight of the graphite powder. When the release agent is used in an amount less than 0.1 parts by weight, a proper releasing property cannot be achieved. Conversely, when it is used in an amount more than 3 parts by weight, mechanical properties of the bipolar plate is deteriorated.

A high-temperature type bipolar plate for fuel cell according to an embodiment of the present invention is prepared via steps of providing source particles, preparing powdery source particles, followed by fluidized coating the source particles, and preparing a bipolar plate, followed by thermal-pressurizing the prepared powdery source particles. First, the source particles are provided in order to prepare the bipolar plate.

The source particles include a graphite powder, a carbon black, a cynate ester resin, an epoxy resin, a hardening catalyst, and a release agent.

The graphite powder, the carbon black and the release agent are mixed in a predetermined ratio to produce a powdery mixture, the cynate ester resin, the epoxy resin, and the hardening catalyst are dissolved in a predetermined ratio in a solvent such as a methylethylketone and an acetone to make a polymer solution.

The powdery source particles are prepared via the fluidized coating process by using the provided powdery mixture and the polymer solution.

Hereinafter, an example of the fluidized coating process will be described in detail with reference to FIG. 1.

As can be seen from FIG. 1 , an apparatus for preparing source particles of a bipolar plate for a fuel cell 1000 comprises a first chamber region 100, a second chamber region 200, and an apparatus for recovering a solvent 300.

The first chamber region 100 comprises a spray nozzle 110 for spraying a mixture solution, a source particle injecting unit for injecting a powdery mixture therethrough 120, and a gas injecting unit 130 for injecting a fluidized gas therethrough

130. The gas injecting unit 130 includes a gas injecting pipe for injecting a gas therethrough 132, a heating apparatus 134 connected to the gas injecting pipe 132, a temperature controller 136 connected to the heating apparatus 134, and a gas distribution plate 138 disposed at the lower portion of the first chamber region 138.

The second chamber region 200 includes a gas discharging unit 210 through which the fluidized gas and the solvent of the mixture solution are discharged, and a skirt region 220. The gas discharging unit 210 is connected to the apparatus for recovering a solvent 300. In order to prepare powdery source particles of a bipolar plate for a fuel cell by using the apparatus for preparing source particles of a bipolar plate for the fuel cell 1000, first, the fluidized gas is heated to a predetermined processing temperature by using the heating apparatus 134 connected to the gas injecting pipe 132. Specifically, the temperature of the heated fluidized gas is controlled by means of the temperature controller 136. Next, the heated fluidized gas is introduced into the first chamber region 100 via the gas injecting pipe 132. Further, a general air or other different gases may be used as the fluidized gas, however, preferably, a nitrogen gas is used so as to inhibit possibilities for dust explosion, additional reactions, etc., other than coating.

A powdery mixture is supplied via the source particle injecting unit 120 while the fluidized gas is being injected via the gas injecting pipe 132. In a first fluidized step, the supplied powdery mixture is dispersed in the first chamber region 100, and is fluidized in a fluidized area (A) of the first chamber region 100, which is formed by means of the skirt region 220 and a sieve 50.

Thereafter, a polymer solution is sprayed via the spray nozzle 110.

In a secondary fluidized step, the sprayed polymer solution is fluidized together with the powdery mixture having been fluidized.

According to the present invention, the powdery mixture is first fluidized, and subsequently the polymer solution is fluidized. However, the powdery mixture and the polymer solution are simultaneously fluidized, as necessary.

The powdery mixture is coated with the polymer solution thereon in the fluidized area (A), while being subjected to the first and second fluidized steps. Here, when an amount and concentration of a polymer solution, and an injected velocity and temperature of a fluidized gas for the powdery mixture are regulated, a thickness of a coated layer may be regulated.

Additionally, a dry solvent in the polymer solution is generated when the powdery mixture is coated with the polymer solution thereon, while being subjected to the first and second fluidized steps. Specifically, a solvent constituent on the coated powdery mixture is vaporized by the fluidized gas. As a result, only a polymer coated layer is remained.

In order to completely dry the solvent constituent, the fluidized gas is continuously injected for a predetermined time period even when completing injection of the powdery mixture and spray of the polymer solution. The injected time period of the fluidized gas may be regulated according to properties and a coating amount of the used solvent.

The vaporized solvent constituent is discharged to the gas discharging unit 210 together with the fluidized gas. Here, the solvent constituent is collected in the apparatus for recovering a solvent 300 connected to gas discharging unit 210. The fluidized gas discharged to the gas discharging unit 210 is treated through a filler and the like, so that the fluidized gas can be re-used.

An equipment such as a general coating mixer, and the like, other than the fluidized coating chamber may be used for preparing the powdery source particles. However, when using the fluidized coating chamber, powdery source particles having a uniform size-distribution can be obtained, and a problem in that a non-coated portion with polymer on the powdery mixture is exposed to the outside or the powdery source particles itself is ground due to having no additional grinding process can be overcome. The polymer solution as described above includes both cyanate ester resin and epoxy resin. However, the cyanate ester resin may be used alone. Next, a bipolar plate for a fuel cell is prepared through the compressing molding and injecting molding by using powdery source particles of a bipolar plate prepared by including both the cynate ester resin and the epoxy resin. The bipolar plate has a cross-linked structure by reacting either the cynate ester resin alone or the cyanate ester resin together with the epoxy resin by means of the heat applied to the powdery source particles upon molding, thereby improving thermal and mechanical strength of the bipolar plate. Specifically, the finished bipolar plate for the fuel cell has a cross-linked structure including a phenolic triazine structure and an oxazoline structure.

The cross-linked structure including the phenolic triazine structure is expressed by the following chemical formula 1. [chemical formula 1]

The cross-linked cynate ester resin further includes structures having a phenyl group, a non-phenol group, a bisphenol group, and a substation-typed phenyl group, a substitution-typed non-phenol group, a substitution-typed bisphenol and the like around the structure of the chemical formula 1 based on the structure of the chemical formula 1.

For example, a phenol novolac -based cynate ester resin among the cynate ester resin is thermally cross-linked to produce a cross-linked structure of phenol triazine expressed by the following equation 1.

[equation 1]

When the cross-linked structure of phenol triazine is produced, a bipolar plate has high thermal stability and physical properties. The thermal stability of the bipolar plate can be regulated to a temperature of 120 to 400°C according to types of polymers to be used.

The speed of a heat-hardening reaction through which the cross-linked structure of the phenol triazine is produced is significantly slow. Accordingly, preferably, a proper hardening catalyst such as a catalyst of transition metal complexes and the like is used in order to accelerate the heat-hardening reaction. The cross-linked structure of oxazolone is produced by reacting a cyanate ester of the cyanate ester resin and an epoxy of the epoxy resin. The cross-linked structure of oxazolone is expressed by the following equation 2.

[equation 2]

R — 0 — C≡ N + R¹— CH CH ₂

N

R-O-C^ ^CH₂ \ / O— CH *

The R of equation 2 includes the remaining functional group except for an ester functional group from the cynate ester resin, and R' of equation 2 includes the remaining functional group except for the epoxy functional group from the epoxy resin. As a result, the bipolar plate for a fuel cell includes either the cross-linked structure of phenol triazine alone, or both the cross-linked structure of phenol triazine and the cross-linked structure of oxazolone.

Hereinafter, the present invention will be described in detail by examples and comparative examples. It is to be understood, however, that these examples are for illustrative purpose only, and are not construed to limit the scope of the present invention.

[Example 1]

100 parts by weight of an artificial graphite powder having an average particle size of 75 μm and aspect ratio of 1.5, 17 parts by weight of a novolac cyanate ester resin,

17 parts by weight of an epoxy resin, 0.01 parts by weight of a cobalt acetyl acetonate, and 0.1 parts by weight of a carnauba wax were thoroughly mixed, coated through the fluidized coating chamber, thereby preparing a bipolar plate for a fuel cell.

The finished powdery source particles prepared by the apparatus for preparing source particles of a bipolar plate had an average particle size of 15 μm, and a uniformity of particle distribution of 0.3, thereby obtaining a significantly uniform powdery source particles of a bipolar plate.

A bipolar plate was prepared by using the prepared powdery source particles in conditions of 225°C, 142 mPa, and 5 minutes.

(1) flexural strength measure

A flexural strength of a bipolar plate was measured according to ASTM D640 by using the prepared bipolar plate and the results are shown in Table 1. (2) electrical conductivity measure

A penetration resistance of the bipolar plate was measured to convert into an electrical conductivity according to ASTM C611 by using the prepared bipolar plate, and the results are shown in Table 1.

(3) modulus and glass transition temperature Modulus changes and glass transition temperature depending on the temperature of the bipolar plate were measured through Dynamic Mechanical Analyzer (DMA) by using the prepared bipolar plate. The measure conditions were the rate of a rising temperature of 2°C/min, vibration at 10 Hz, 50 μm (amplitude). Also, in this instance a single clamp was used and the results are shown in Table 1 below. [Comparative Example 1 ]

A flexural strength, electrical conductivity, glass transition temperature and modulus were measured in the same manner as Example 1 by using a bipolar plate of ShinEtsu Co., and the results are shown in Table 1 below.

[Comparative Example 2] A flexural strength, electrical conductivity, glass transition temperature and modulus were measured in the same manner as Example 1 by using a bipolar plate of Entegris Co., and the results are shown in Table 1 below.

(Table 1)

As can be seen in Table 1 , the bipolar plate of the present invention showed excellent flexural strength and electrical conductivity when compared to Comparative Examples 1 and 2.

The glass transition temperature (Tg) of the bipolar plate of the present invention was higher than those of Comparative Examples 1 and 2. Further, the modulus at a temperature of 150°C showed relatively excellent results when compared to Comparative Examples 1 and 2.

As described above, according to the present invention, a source composition of a high-temperature type bipolar plate for a fuel cell and a high-temperature type bipolar plate for a fuel cell manufactured by using the same can provide a high thermal stability and durability in the range between 120 and 400⁰C. Specifically, the cross-linked structure of a phenol triazine is produced in the bipolar plate by using a phenol cyanate ester resin, thereby improving physical stability of the bipolar plate at a relatively high temperature. Further, the bipolar plate exhibits an excellent flexural strength, so that a stack can be stably formed upon preparing the fuel cell. Also, the bipolar plate has a high conductivity, thereby improving performance of the fuel cell.

Although a few embodiments of the present invention have been shown and described, the present invention is not limited to the described embodiments. Instead, it would be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A source composition of high-temperature type bipolar plate for a fuel cell, the source composition comprising:

100 parts by weight of a graphite powder; 0.2 to 10 parts by weight of a carbon black; and

0.1 to 40 parts by weigh of a cyanate ester resin.

2. The composition of claim 1, wherein the graphite powder comprises columnar graphite particles having an aspect ratio in the range between 1.5 and 2.

3. The composition of claim 1, wherein the carbon black has a specific surface area of 50 to 100 m²/g.

4. The composition of claim 1, wherein the cyanate ester resin comprises at least one resin selected from a group consisting of a phenol novolac -based cyanate ester resin, a biphenol-based dicyanate ester resin, bisphenol A-based dicyanate ester resin, a bisphenol E-based dicyanate ester resin, and a bisphenol F-based dicyanate ester resin.

5. The composition of claim 1, further comprising 0.05 to 20 parts by weight of an epoxy resin, wherein the cynate ester resin is used in an amount of 0.05 to 20 parts by weight.

6. The composition of claim 1, further comprising 0.01 to 1 parts by weight of a hardening catalyst.

7. The composition of claim 6, wherein the hardening catalyst comprises at least one hardening catalyst selected from a group of transition metal complexes of acetylacetonate, octoate, and naphthenate types, the group of transition metal complexes consisting of a metal material including any one of cobalt, copper, manganese, plumbum, nickel, and zinc.

8. The composition of claim 1, further comprising 0.1 to 3 parts by weight of a release agent.

9. A high-temperature type bipolar plate for a fuel cell having a cross-linked structure of phenolic triazine.

10. The bipolar plate of claim 9, wherein the cross-linked structure of phenolic triazine is formed with a phenolic cynate ester polymer having been thermally crosslinked and comprises a unit structure expressed by the following chemical formula 1 [chemical formula 1]

11. The bipolar plate of claim 9, further comprising an oxazoline structure formed by reacting an epoxy group with a cyanate group.