BONDED FUEL CELL ASSEMBLY AND METHODS AND SYSTEMS FOR PRODUCING THE SAME

FIELD OF THE INVENTION:

[0001 J The present invention relates to a method for bonding and sealing components of an electrochemical cell, such as a fuel cell, and an electrochemical cell formed therefrom. More particularly, the present invention relates to a method and design for bonding fuel cell components in a manner suitable for continuous production of the fuel cell components.

BRIEF DESCRIPTION OF RELATED TECHNOLOGY:

[0002] Although there are various known types of electrochemical cells, one common type is a fuel cell, such as a proton exchange membrane ("PEM") fuel cell. The PEM fuel cell contains a membrane electrode assembly ("MEA") provided between two flow field plates or bipolar plates. Gaskets are used between the bipolar plates and the MEA to provide seals thereat. Additionally, since an individual PEM fuel cell typically provides relatively low voltage or power, multiple PEM fuel cells are stacked to increase the overall electrical output of the resulting fuel cell assembly. Sealing is also required between the individual PEM fuel cells. Moreover, cooling plates are also typically provided to control temperature within the fuel cell. Such plates are also sealed to prevent leakage within the fuel cell assembly. After assembling the fuel cell stack is clamped to secure the assembly.

[0003) As described in U.S. Patent No. 6,057,054, liquid silicone rubbers have been proposed to be molded onto fuel assemblies. Such silicone compositions, however, degrade before the desired operating lifetime of the fuel cell is achieved. Also, such silicone rubbers release materials that contaminate the fuel cell, thereby adversely affecting the performance of the fuel cell. Molding of liquid silicone rubber onto separator plates is also described in U.S. Patent No. 5,264,299. To increase the operating lifetime, more durable elastomers such as fluoroelastomers, as described in U.S. Patent No. 6,165,634, and polyolefin hydrocarbons, as

described in U.S. Patent No. 6,159,628, have been proposed to bond the surface of fuel cell components. The application of these compositions, however, is time consuming as each individual element of the fuel cell or each arrangement of fuel cell components have to be individually bonded with these compositions.

[0004] U.S. Patent Application Publication No. US 2005/0263246 Al describes a method for making an edge-seal on a membrane electrode assembly that impregnates the gas diffusion layer using a thermoplastic film. Application temperatures suitable for bonding the thermoplastic film may limit the design of a fuel cell and also are difficult to apply as aligned stacks of fuel cell components have to be heated and cooled under controlled conditions.

[0005] U.S. Patent No. 6,884,537 described the use of rubber gaskets with sealing beads for sealing fuel cell components. The gaskets are secured to the fuel cell components through the use of layers of adhesive to prevent movement or slippage of the gaskets. Similarly, International Patent Publication Nos. WO 2004/061338 Al and WO 2004/079839 A2 describe the use of multi-piece and single-piece gaskets for sealing fuel cell components. The gaskets are secured to the fuel cell components through use of an adhesive. The placement of the adhesives and the gaskets are not only time consuming, but problematic because misalignment may cause leakage and loss of performance of the fuel cell.

[0006] U.S. Patent No. 6,875,534 describes a cured-in-place composition for sealing a periphery of a fuel cell separator plate. The cured-in-place composition includes a polyisobutylene polymer having a terminal allyl radial at each end, an organopolysiloxane, an organohydrogenpolysiloxane having at least two hydrogen atoms each attached to a silicon atom and a platinum catalyst. U.S. Patent No. 6,451,468 describes a formed-in-place composition for sealing a separator, an electrode or an ion exchange membrane of a fuel cell. The formed-in- place composition includes a linear polyisobutylene perfluoropolyether having a terminal alkenyl group at each end, a cross-linker or hardener having at least two hydrogen atoms each bonded to a silicon atom, and a hydrosilylation catalyst. The cross-linked density and the resultant properties of these compositions are limited by using linear polyisobutylene oligomers having an allyl or alkenyl functionality of two. Functionality of these compositions is modified by varying the hydrosilyl functionality, which limits the properties of the resultant compositions.

(0007) International Patent Publication No. WO 2004/047212 A2 describes the use of a foam rubber gasket, a liquid silicone sealant or a solid fluoroplastic for sealing fluid transport layer or a gas diffusion layer of a fuel cell. The use of solid gaskets, i.e., foam rubber and/or solid fluoroplastic tape or film, makes placement of these materials and subsequent alignment of the fuel cell components and gaskets time consuming and problematic.

[0008] U.S. Patent Application Publication No. 2003/0054225 describes the use of rotary equipment, such as drums or rollers, for applying electrode material to fuel cell electrodes. While this publication describes an automated process for forming fuel cell electrodes, the publication fails to address the sealing concerns of the formed fuel cells.

[0009) EP 159 477 Al describes a peroxide curable terpolymer of isobutylene, isoprene and para-methylstryene. Use of the composition in fuel cells is noted, but no application, processing, or device details are provided.

[0010] U.S. Patent No. 6,942,941 describes the use of a conductive adhesive to bond different sheets to form a bipolar separator plate. A conductive primer is first applied onto two plates and partially cured by heating to about 100°F. An adhesive is then applied between the two plates, and after pressing the plates together the adhesive is cured by heating to about 260°C.

[0011] Despite the state of the art, there remains a need for a sealant composition suitable for use with electrochemical cell components, desirably applied through liquid injection molding.

SUMMARY OF THE INVENTION;

[0012] The present invention provides a method, a composition and a system to bond and seal fuel cell components. The sealant composition used to bond and seal fuel cell parts may include two or more components that separately are stable, however, when combined or exposed to an energy source are curable. In a two-component sealant system, one part of the sealant may be applied to first fuel cell component substrate, and the second part may be applied to a second fuel cell substrate. The substrates are joined and the sealant is cured to from a bonded fuel cell component assembly.

[0013] In one aspect of the present invention, a method for forming a fuel cell component includes providing a two-part sealant having a first part including an initiator and a second part including a polymerizable material; applying the first part of the sealant to a substrate of a first fuel cell component; applying the second part of the sealant to a substrate of a second fuel cell component; juxtaposingly aligning the substrates of the first and second fuel cell components; and curing the sealant to bond the first and second fuel components to one and the other. Desirably, the initiator is an actinic radiation initiator, whereby the sealant is cured by actinic radiation. The polymerizable material may be a polymerizable monomer, oligomer, telechelic polymer, functional polymer and combinations thereof. Desirably, the functional group is epoxy, allyl, vinyl, acrylate, methacrylate, imide, amide, urethane and combinations thereof. Useful fuel cell components to be bonded include a cathode flow field plate, an anode flow field plate, a resin frame, a gas diffusion layer, an anode catalyst layer, a cathode catalyst layer, a membrane electrolyte, a membrane-electrode-assembly frame, and combinations thereof.

[0014] In another aspect of the present invention, a method for forming a fuel cell component includes providing a two-part sealant, where a first part includes an initiator and the second part includes a polymerizable material; providing first and second separator plates and first and second resin frames; coating a side or both sides, desirably both sides, of the first separator plate with the first part of the sealant; activating the first part of the sealant on the first separator plate with actinic radiation; coating a side or both sides, desirably one side, of the first resin frame with the second part of the sealant; juxtaposingly aligning first separator plate and the first resin frame; curing the sealant to bond the first separator plate and the first resin frame to one and the other; coating a side or both sides, desirably both sides, of the second separator plate with the second part of the sealant; coating a side or both sides, desirably one side, of the second resin frame with the first part of the sealant; activating the first part of the sealant on the second resin frame with actinic radiation; juxtaposingly aligning the second separator plate and the second resin frame; curing the sealant to bond the second separator plate and the second resin frame to one and the other; juxtaposingly aligning the first and second separator plates; curing the sealant to bond the first and second separator plates to one and the other to form a form bipolar separator plate. Desirably, the initiator is an actinic radiation initiator, whereby the sealant is cured by actinic radiation. The polymerizable material may be a polymerizable

monomer, oligomer, teiecneiic polymer, functional polymer and combinations thereof. Desirably, the functional group is epoxy, allyl, vinyl, acrylate, methacrylate, imide, amide, urethane and combinations thereof. Useful fuel cell components to be bonded include a cathode flow field plate, an anode flow field plate, a resin frame, a gas diffusion layer, an anode catalyst layer, a cathode catalyst layer, a membrane electrolyte, a membrane-electrode-assembly frame, and combinations thereof.

(0015] In another aspect of the present invention, a system for forming a fuel cell component includes a first dispenser for providing a first part of a two-part sealant, where the first part the sealant includes an initiator; a second dispenser for providing a second part of a two- part sealant, where the second part of the sealant includes a polymerizable material; a first station for applying the first part of the sealant to a substrate of a first fuel cell component; a second station for applying the second part of the sealant to a substrate of a second fuel cell component; a third station for juxtaposingly aligning the substrates of the first and second fuel cell components; and a curing station for curing the sealant to bond the first and second fuel components to one and the other. Desirably, the initiator is an actinic radiation initiator, whereby the sealant is cured by actinic radiation. The polymerizable material may be a polymerizable monomer, oligomer, telechelic polymer, functional polymer and combinations thereof. Desirably, the functional group is epoxy, allyl, vinyl, acrylate, methacrylate, imide, amide, urethane and combinations thereof. Useful fuel cell components to be bonded include a cathode flow field plate, an anode flow field plate, a resin frame, a gas diffusion layer, an anode catalyst layer, a cathode catalyst layer, a membrane electrolyte, a membrane-electrode-assembly frame, and combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS:

[0016] FIG. 1 is a cross-sectional view of a fuel cell having an anode flow field plate, a resin frame, a gas diffusion layer, an anode catalyst, a proton exchange membrane, a cathode catalyst, a second gas diffusion layer, s second resin frame and a cathode flow field plate.

[0017] FIG. 2 is an exploded, cross-sectional view of a separator plate and resin frame assembly according to the present invention.

[0018) FIG. 3 is a cross-sectional view of an assembled separator plate and resin frame assembly according to the present invention.

[0019J FIG. 4 is a schematic of an assembly for forming bonded fuel cell components of the present invention.

DETAILED DESCRIPTION OF THE INVENTION:

[0020| The present invention is directed to a method for bonding and compositions for bonding components of an electrochemical cell. As used herein, an electrochemical cell is a device which produces electricity from chemical sources, including but not limited to chemical reactions and chemical combustion. Useful electrochemical cells include fuel cells, dry cells, wet cells and the like. A fuel cell, which is described in greater detail below, uses chemicals reactants to produce electricity. A wet cell has a liquid electrolyte. A dry cell has an electrolyte absorbed in a porous medium or otherwise restrained from being flowable.

[0021] FIG. 1 shows a cross-sectional view of the basic elements of an electrochemical fuel cell, such as fuel cell 10. Electrochemical fuel cells convert fuel and oxidant to electricity and reaction product. Fuel cell 10 consists of an anode flow field plate 12 with open face coolant channels 14 on one side and anode flow channels 16 on the second side, a resin plate 13, a gas diffusion layer 18, an anode catalyst 20, a proton exchange membrane 22, a cathode catalyst 24, a second gas diffusion layer 26, a second resin plate 13 and a cathode flow field plate 28 with open face coolant channels 30 on one side and cathode flow channels 32 on the second side, interrelated as shown in FIG. 1. The gas diffusion layer 18, the anode catalyst 20, the proton exchange membrane 22, the cathode catalyst 24 and the second gas diffusion layer 26 combination is often referred to as a membrane electrode assembly 36. Gas diffusion layers 18 and 26 are typically formed of porous, electrically conductive sheet material, such as carbon fiber paper. The present invention is not, however, limited to the use of carbon fiber paper and other materials may suitably be used. Fuel cells are not, however, limited to such a depicted arrangement of components. The anode and cathode catalyst layers 20 and 24 are typically in the form of finely comminuted platinum. The anode 34 and cathode 38 are electrically coupled (not shown) to provide a path for conducting electrons between the electrodes to an external load (not

shown). The flow field plates 12 and 28 are typically formed of graphite impregnated plastic, compressed and exfoliated graphite; porous graphite; stainless steel or other graphite composites. The plates may be treated to effect surface properties, such as surface wetting, or may be untreated. The present invention is not, however, limited to the use of such materials for use as the flow field plates and other materials may suitably be used. For example, in some fuel cells the flow field plates are made from a metal or metal containing material, typically, but not limited to, stainless steel. The flow field plates may be bipolar plates, i.e., a plate having flow channels on opposed plate surfaces. For example, as depicted in FIGS. 2-3, the bipolar flow field plates 15 may be made from monopolar plates 12, 28 having a flow channel only on one side. The monopolar plates 12 and 28 are secured to one and the other to from bipolar plates 15. In one aspect of the present invention, the plates 12 and 28 are also sealed with the composition and by the methods of the present invention.

[0022] Some fuel cell designs utilize resin frames 13 between the membrane electrode assembly 36 and the separator plates 12, 28 to improve the durability of the membrane electrode assembly 36 and afford the correct spacing between the membrane electrode assembly 36 and separator plates 12, 28 during fuel cell assembly. In such a design, it is necessary have a seal between the separator plates 12, 28 and the resin frames 13.

[0023) The present invention is not limited to the fuel cell components and their arrangement depicted in FIG. 1. For example, a direct methanol fuel cell ("DMFC") can consist of the same components shown in FIG. 1 less the coolant channels. Further, the fuel cell 10 can be designed with internal or external manifolds (not shown).

[0024] While this invention has been described in terms of a proton exchange membrane

(PEM) fuel cell, it should be appreciated that the invention is applicable to any type of fuel cell. The concepts in this invention can be applied to phosphoric acid fuel cells, alkaline fuel cells, higher temperature fuel cells such as solid oxide fuel cells and molten carbonate fuel cells, and other electrochemical devices.

[0025] At anode 34, a fuel (not shown) traveling through the anode flow channels 16 permeates the gas diffusion layer 18 and reacts at the anode catalyst layer 20 to form hydrogen

cations (protons), which migrate through the proton exchange membrane 22 to cathode 38. The proton exchange membrane 22 facilitates the migration of hydrogen ions from the anode 34 to the cathode 38. In addition to conducting hydrogen ions, the proton exchange membrane 22 isolates the hydrogen-containing fuel stream from the oxygen-containing oxidant stream.

[00261 At the cathode 38, oxygen-containing gas, such as air or substantially pure oxygen, reacts with the cations or hydrogen ions that have crossed the proton exchange membrane 22 to form liquid water as the reaction product. The anode and cathode reactions in hydrogen/oxygen fuel cells are shown in the following equations:

Anode reaction: H ₂ -» 2 H ⁺ + 2 e ^~ (I)

Cathode reaction: V ₂ O ₂ + 2 H ⁺ + 2 e ^" → H ₂ O (II)

[0027] In one aspect of the present invention, a two-part sealant is used to bond separator plates 12, 28 and resin frames 13. Part A of the sealant may contain a UV-activated initiator, which may be an acid, base, radical, anionic, and/or cationic initiator. Part B of the sealant may include a polymerizable monomer, oligomer, telechelic polymer, and/or functional polymer. The functional group could be, as an example, an epoxy, allyl, vinyl, acrylate, methacrylate, imide, amide or urethane. The resin frames 13 are used for spacing within the fuel cell assembly 10. The resin frames 13 are placed on the gas pathway sides of the separators 12, 28 and seals are provided between each element. In the first manufacturing line, a separator plate 12, typically a metal sheet, such as stainless steel, is desirably coated on both sides with part A of the sealant, cut, stamped to produce the necessary channels for reactive gas and coolant pathways, and activated with UV light. A resin frame 13 is coated on at least one side with part B of the sealant and is assembled with the coated separator plate 12 to provide an anode separator with bonded frame. In the second manufacturing line, a second separator plate 12, typically a sheet of stainless steel, is desirably coated on both sides with part B of the sealant, cut, and stamped to produce the necessary channels for reactive gas and coolant pathways to form separator plate 28. A second resin frame 13 coated on at least one side with part A of the sealant and irradiated with UV light is assembled with the separator plate 28 to provide a cathode separator with a bonded frame. Finally, the two manufacturing lines meet so that the bonded anode separator having an exposed coating of part A of the sealant on one of its side and the bonded cathode separator

having an exposed coating of part B of the sealant on one of its sides are aligned, part A and part B of the sealant react and seal the fuel cell interfaces and to form bonded assembly.

[0028] In another aspect of the present invention, a two-part sealant is used to bond the separator plates 12, 28. Part A of the sealant contains a UV-activated initiator, which may be an acid, base, radical, anionic, and/or cationic initiator. Part B of the sealant is composed of a polymerizable monomer, oligomer, telechelic polymer, and/or functional polymer. The functional group could be, as an example, an epoxy, allyl, vinyl, acrylate, methacrylate, imide, amide or urethane. Part A is applied to the first separator plate, and part B is applied to the second separator plate. Part A is applied to the coolant pathway side of the anode separator 12. Part B is applied to the coolant pathway side of the cathode separator 28. On the anode separator 12, part A undergoes UV irradiation to activate the initiator, followed by compression assembly with the cathode separator 28. The separators 12, 28 are joined so that part A and part B react and seal the components to form the bipolar plate 15.

[0029] In another aspect of the present invention, a one-part sealant is used to bond separator plates 12, 28 and resin frames 13. The sealant, which may be composed of a UV- activated acid, base, radical, anionic, and/or cationic initiator and polymerizable monomer, oligomer, telechelic polymer and/or functional polymer, may be applied to one substrate, radiated with UV light, and compressed with a second substrate to form the seal.

[0030] In another aspect of the present invention, a two-part composition is used to bond and seal. Part A is applied to the first substrate. Part B is applied to the second substrate. The two substrates are combined and fixtured. Polymerization may be achieved in its simplest form by bringing the two substrates together, or by combining the substrates and using some additional form of energy, such as pressure, heat, ultrasonic, microwave or any combinations thereof.

[0031] In another aspect of the present invention, the liquid gasket-forming material may include actinic radiation curable acrylates, urethanes, polyethers, polyolefins, polyesters, copolymers thereof and combinations thereof. Desirably, the curable material includes a (meth)acryloyl terminated material having at least two (meth)acryloyl pendant groups. Desirably, the (meth)acryloyl pendant group is represented by the general formula:

-OC(O)C(R ')=CH ₂ , where R ¹ is hydrogen or methyl. More desirably, the liquid gasket-forming material is a (meth)acryloyl-terminated poly acrylate. The (meth)acryloyl-terminated poly aery late may desirably have a molecular weight from about 3,000 to about 40,000, more desirably from about 8,000 to about 15,000. Further, the (meth)acryloyl-terminated poly acrylate may desirably have a viscosity from about 200 Pas (200,000 cPs) to about 800 Pas (800,000 cPs) at 25°C (77 ⁰ F), more desirably from about 450 Pas (450,000 cPs) to about 500 Pas (500,000 cPs). Details of such curable (meth)acryloyl-terminated materials may be found in European Patent Application No. EP 1 059 308 Al to Nakagawa et al., and are commercially available from Kaneka Corporation, Japan.

[0032] Desirably, the liquid composition includes a photoinitiator. A number of photoinitiators may be employed herein to provide the benefits and advantages of the present invention to which reference is made above. Photoinitiators enhance the rapidity of the curing process when the photocurable compositions as a whole are exposed to electromagnetic radiation, such as actinic radiation. Examples of suitable photoinitiators for use herein include, but are not limited to, photoinitiators available commercially from Ciba Specialty Chemicals, under the "IRGACURE" and "DAROCUR" trade names, specifically "IRGACURE" 184 (1- hydroxycyclohexyl phenyl ketone), 907 (2-methyl-l-[4-(methylthio)phenyl]-2-morpholino propan-1 -one), 369 (2-benzyl-2-N,N-dimethylamino-l-(4-moφholinophenyl)-l-butan one), 500 (the combination of 1 -hydroxy cyclohexyl phenyl ketone and benzophenone), 651 (2,2- dimethoxy-2-phenyl acetophenone), 1700 (the combination of bis(2,6-dimethoxybenzoyl-2,4,4- trimethyl pentyl) phosphine oxide and 2-hydroxy-2-methyl-l-phenyl-propan-l-one), and 819 [bis(2,4,6-trimethyl benzoyl) phenyl phosphine oxide] and "DAROCUR" 1 173 (2-hydroxy-2- methyl-1 -phenyl- 1 -propan-1-one) and 4265 (the combination of 2,4,6-trimethylbenzoyldiphenyl- phosphine oxide and 2-hydroxy-2-methyl-l-phenyl-propan-l-one); and the visible light [blue] photoinitiators, dl-camphorquinone and "IRGACURE" 784DC. Of course, combinations of these materials may also be employed herein.

[0033] Other photoinitiators useful herein include alkyl pyruvates, such as methyl, ethyl, propyl, and butyl pyruvates, and aryl pyruvates, such as phenyl, benzyl, and appropriately substituted derivatives thereof. Photoinitiators particularly well-suited for use herein include

ultraviolet photoinitiators, such as 2,2-dimethoxy-2-phenyl acetophenone (e.g., "IRGACURE" 651), and 2-hydroxy-2-methyl-l -phenyl- 1 -propane (e.g., "DAROCUR" 1 173), bis(2,4,6- trimethyl benzoyl) phenyl phosphine oxide (e.g., "IRGACURE" 819), and the ultraviolet/visible photoinitiator combination of bis(2,6-dimethoxybenzoyl-2,4,4-trimethylpentyl) phosphine oxide and 2-hydroxy-2-methyl-l-phenyl-propan-l-one (e.g., "IRGACURE" 1700), as well as the visible photoinitiator bis (η ⁵ -2,4-cyclopentadien-l-yl)-bis[2,6-difluoro-3-(lH-pyrrol-l- yl)phenyl]titanium (e.g., "IRGACURE" 784DC). Useful actinic radiation includes ultraviolet light, visible light, and combinations thereof. Desirably, the actinic radiation used to cure the liquid gasket-forming material has a wavelength from about 200 nm to about 1 ,000 nra. Useful UV includes, but is not limited to, UVA (about 320 nm to about 410 nm), UVB (about 290 nm to about 320 nm), UVC (about 220 nm to about 290 nm) and combinations thereof. Useful visible light includes, but is not limited to, blue light, green light, and combinations thereof. Such useful visible lights have a wavelength from about 450 nm to about 550 nm.

[0034] The present invention, however, is not limited to only the use of UV radiation and other energy sources such as heat, pressure, ultraviolet, microwave, ultrasonic or electromagnetic radiation may be used to initiate polymerization of one or more of the compositions. Additionally, the initiator could be active without an activating agent. Further, the initiation process may be applied before, during and/or after assembly.

|0035) FIG. 4 depicts a system 50 for forming bonded assemblies, such as fuel cells or bonded fuel cell components, according the present invention. System 50 includes different stations 52, 54 for processing different fuel cell components. The system includes dispensers 56 and 58 for dispensing first and second parts, respectively, of a two-part sealant composition to coat different duel cell components. The system further includes sources 60 of energy, such as actinic radiation.

[0036) In another aspect of the present invention, a fuel cell stack may be prepared from a modular assembly and a gasket. A resin framed-MEA is produced in the first step. The anode and cathode resin frames are coated with a single component UV-activated sealant on one side of the resin frame. The sealant is activated by UV irradiation and the resin frames are fixtured on either side of the MEA. In the second step, the separators are bonded to the resin frames using a

two-part sealant. In a two-component system, part A would be applied to substrate one, part B would be applied to substrate two. Part A and B when combined could polymerize in one form of this invention. The resin framed-MEA is coated with part A on the resin frames, and then activated by UV irradiation. At the same time, the reactant gas sides of the separators are coated with part B. The resin framed-MEA is fixtured with the anode and cathode separators to produce a unit cell (anode separator, anode resin frame, MEA, cathode resin frame, and cathode separator). In the next step, the unit cells are bonded together with a two-part sealant to form a module, containing a select number of unit cells, such as ten, for example. The unit cell is run through an operation to apply uncured polymer to the surface of one or more substrates. The coolant pathway side of the anode separator may be coated with part A and activated with UV irradiation. The coolant pathway side of the cathode separator may be coated with part B. The cells are stacked and fixtured to react part A with part B and seal the coolant pathways of the module. The separators at the ends of the module may not be coated in the process described above. In a separate manufacturing line, a gasket is produced from sheet metal and a UV- activated sealant. A roll of sheet metal is cut, coated with a single component UV-activated sealant, and placed under UV light. The fuel cell stack may be assembled by alternating the gaskets with the modules until the desired number of cells in the stack is achieved. It is also envisioned that the resin frames and separators may be coated on both sides with the appropriate sealant, fixtured to the first component and then fixtured to the second component.

[0037] In another aspect of the present invention, a fuel cell stack may be prepared from a modular assembly and a gasket. A resin framed-MEA is produced in the first step. Two resin frames are coated with a single component UV-activated sealant on one side of the resin frame. The sealant is activated by UV irradiation and the resin frames are fixtured on either side of the MEA. In the second step, a bonded separator is sealed to the resin framed-MEA using a two-part sealant. In a two-component system, part A of the sealant would be applied to a first substrate, part B of the sealant would be applied to a second substrate. Part A and B of the sealant, when combined, polymerize to form a bonded assembly according to one aspect of the present invention. For example, an anode resin frame may be coated with part A of the sealant, and then activated by UV irradiation. A resin framed-MEA may be fixtured with the bonded separators to produce a unit cell (cathode separator, anode separator, anode resin frame, MEA, and cathode

resin frame). The anode and cathode separators are bonded in another manufacturing line using a two-component sealant. The coolant pathway side of the anode separator is coated with part A of the sealant, and then activated by UV irradiation. The coolant pathway side of the cathode separator is coated with part B of the sealant, and fixtured to anode separator to react part A of the sealant with part B. In the next step, the unit cells are bonded together with a two-part sealant to form a module, containing a select number of unit cells, such as but not limited to ten. The unit cell is run through a coating operation. The gas pathway side of the cathode separator may be coated with part A of the sealant and activated with UV irradiation. The cathode resin frame may be coated with part B of the sealant. The unit cells are stacked and fixtured to react part A of the sealant with part B of the sealant to produce a module of bonded unit cells. The separator and resin frame at the ends of the module would not be coated in the process described above. In a separate manufacturing line, a gasket is produced from sheet metal and a UV-activated sealant. A roll of sheet metal is cut, coated with a single component UV-activated sealant, and placed under UV light. The fuel cell stack is assembled by alternating the gaskets with the modules until the desired number of cells in the stack is achieved. It is also envisioned that the resin frames and separators may be coated on both sides with the appropriate sealant, fixtured to the first component and then fixtured to the second component.