Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/02—Details
  • H01M8/0271—Sealing or supporting means around electrodes, matrices or membranes
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J7/00—Adhesives in the form of films or foils
  • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
  • C09J7/38—Pressure-sensitive adhesives [PSA]
  • C09J7/381—Pressure-sensitive adhesives [PSA] based on macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
  • C09J11/02—Non-macromolecular additives
  • C09J11/06—Non-macromolecular additives organic
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J127/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Adhesives based on derivatives of such polymers
  • C09J127/02—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Adhesives based on derivatives of such polymers not modified by chemical after-treatment
  • C09J127/12—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Adhesives based on derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J5/00—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J7/00—Adhesives in the form of films or foils
  • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/02—Details
  • H01M8/0271—Sealing or supporting means around electrodes, matrices or membranes
  • H01M8/0276—Sealing means characterised by their form
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/02—Details
  • H01M8/0271—Sealing or supporting means around electrodes, matrices or membranes
  • H01M8/028—Sealing means characterised by their material
  • H01M8/0284—Organic resins; Organic polymers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/02—Details
  • H01M8/0271—Sealing or supporting means around electrodes, matrices or membranes
  • H01M8/0286—Processes for forming seals
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/02—Details
  • H01M8/0297—Arrangements for joining electrodes, reservoir layers, heat exchange units or bipolar separators to each other
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/1004—Fuel cells with solid electrolytes characterised by membrane-electrode assemblies [MEA]
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
  • H01M8/241—Grouping of fuel cells, e.g. stacking of fuel cells with solid or matrix-supported electrolytes
  • H01M8/242—Grouping of fuel cells, e.g. stacking of fuel cells with solid or matrix-supported electrolytes comprising framed electrodes or intermediary frame-like gaskets
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J2203/00—Applications of adhesives in processes or use of adhesives in the form of films or foils
  • C09J2203/326—Applications of adhesives in processes or use of adhesives in the form of films or foils for bonding electronic components such as wafers, chips or semiconductors
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J2203/00—Applications of adhesives in processes or use of adhesives in the form of films or foils
  • C09J2203/33—Applications of adhesives in processes or use of adhesives in the form of films or foils for batteries or fuel cells
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J2301/00—Additional features of adhesives in the form of films or foils
  • C09J2301/40—Additional features of adhesives in the form of films or foils characterized by the presence of essential components
  • C09J2301/408—Additional features of adhesives in the form of films or foils characterized by the presence of essential components additives as essential feature of the adhesive layer
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J2427/00—Presence of halogenated polymer
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• Gaskets are useful for providing seals between two different components in a variety of articles.
• a conventional proton exchange membrane (PEM) fuel cell requires two flow field plates, an anode flow field plate and a cathode flow field plate.
• a membrane electrode assembly (ME A) including the actual proton exchange membrane is provided between the two flow field plates.
• GDM/GDL gas diffusion media or layer
• the gas diffusion media enables diffusion of an appropriate gas, either the fuel or the oxidant, to the surface of the proton exchange membrane, while at the same time providing conduction of electricity between the associated flow field plate and the PEM.
• the GDL may also be called a fluid transport layer (FTL) or a diffuser/current collector (DCC).
• FTL fluid transport layer
• DCC diffuser/current collector
• Fluoroelastomers have been reported to be useful as gaskets between a flow field plates in a fuel cell. See, for example, U.S. Pat. No. 7,569,299 (Thompson); 7,309,068 (Segawa); 6,720,103 (Nagai), U.S Pat. Appl. Pub. No. 2014/0077462 (Hong), and Japanese Patent No. 5162990, published March 13, 2013. Fluoroelastomer gaskets typically have been prepared by molding (e.g., injection molding) uncured amorphous fluoropolymers.
• Manufacturing gaskets for use in assemblies is generally carried out in one of two ways.
• an individual gasket can be formed by molding it in a suitable mold. With this method, the designer advantageously has freedom in choosing the cross-section of each gasket, which does not have to have a uniform thickness.
• molding gaskets can be relatively complex and expensive, and for each fuel cell configuration, design and manufacture of a mold corresponding exactly to the shape of the associated grooves in the flow field plates would be required.
• each gasket is cut from a solid sheet of material.
• a gasket having the same shape as the die-cut gasket can be made using separate pieces of material (e.g., adhesive tape) as shown in FIGS. 2 and 3, which would result in significant waste and cost reduction.
• adhesive tape e.g., adhesive tape
• a potential problem for a gasket formed with separate strips of adhesive tape is that gas leaking could occur from the gaps between the separate strips of tape.
• the adhesive tape includes an amorphous fluoropolymer
• applying at least one of heat or pressure to the adhesive tape can allow the adhesive to flow into and seal the gaps between the separate strips of adhesive tape.
• useful gaskets can be made from separate strips of tape without introducing the problem of gas leaking.
• the present disclosure provides a method of making an assembly.
• the method includes providing a component of an assembly having an interior portion and a peripheral portion and adhering separate strips of an adhesive tape to the peripheral portion of the component to surround the interior portion.
• the short side of a first strip is positioned adjacent a second strip.
• the adhesive tape includes an adhesive disposed on a backing, and the adhesive includes an amorphous fluoropolymer.
• the method further includes applying at least one of heat or pressure to the separate strips such that the adhesive seals any gap between the first and second strips and crosslinks.
• the method can be useful, for example, when the assembly is a fuel cell assembly and when the component includes at least one of an electrolyte membrane or a gas diffusion layer.
• the method can also be useful, for example, for hard disk drive assemblies, semiconductor devices, and other electrode assemblies including electrolyzers and battery assemblies.
• the present disclosure provides component of an assembly (e.g., a membrane electrode assembly) having an interior portion and a peripheral portion with separate strips of a tape backing having first surfaces adhered to the peripheral portion of the component to surround the interior portion.
• the component can include at least one of an electrolyte membrane or a current collector.
• the short side of a first strip of the tape backing is positioned adjacent a second strip of the tape backing.
• An adhesive disposed on the first surfaces of the separate strips of the tape backing seals a gap between the first and second strips of tape backing and adheres the separate strips to the peripheral portion of the component.
• the adhesive includes a crosslinked amorphous fluoropolymer.
• the component can be useful, for example, in a fuel cell assembly or subassembly.
• the component can also be useful, for example, for hard disk drive assemblies, semiconductor devices, and other electrode assemblies including electrolyzers and battery assemblies.
• the present disclosure provides a component of an assembly (e.g., a membrane electrode assembly) having an interior portion and a peripheral portion with separate adhesive strips disposed on the peripheral portion of the component to surround the interior portion.
• the component can include at least one of an electrolyte membrane or a current collector.
• a short side of a first adhesive strip is positioned adjacent a second adhesive strip.
• Each of the separate adhesive strips includes an adhesive that includes an amorphous fluoropolymer.
• the present disclosure provides a component of a membrane electrode assembly with separate adhesive strips disposed thereon before the adhesive is crosslinked.
• the component can be useful for making a fuel cell assembly or subassembly.
• the component can also be useful, for example, for hard disk drive assemblies, semiconductor devices, and other electrode assemblies including electrolyzers and battery assemblies.
• the present disclosure provides an electrochemical cell made by the method described above and/or including the component described above.
• phrases “comprises at least one of followed by a list refers to comprising any one of the items in the list and any combination of two or more items in the list.
• the phrase “at least one of followed by a list refers to any one of the items in the list or any combination of two or more items in the list.
• curable and “curable” joining polymer chains together by covalent chemical bonds, usually via crosslinking molecules or groups, to form a network polymer. Therefore, in this disclosure the terms “cured” and “crosslinked” may be used interchangeably.
• a cured or crosslinked polymer is generally characterized by insolubility, but may be swellable in the presence of an appropriate solvent.
• FIG. 1 is a plan view of a die cut gasket useful, for example, in membrane electrode assemblies
• FIG. 2 is a plan view of an embodiment of a configuration of adhesive strips useful in the assemblies and methods according to the present disclosure
• FIG. 3 is a plan view of another embodiment of a configuration of adhesive strips useful in the assemblies and methods according to the present disclosure
• FIG. 4A is cross-section taken at line 4A-4A in FIG. 2, showing one embodiment of adhesive strips before the adhesive is cured;
• FIG. 4B is cross-section taken at line 4A-4A in FIG. 2, showing the adhesive strips in FIG. 4A after the adhesive is cured;
• FIG. 5 is an exploded perspective view of a fuel cell including adhesive strips in accordance with some embodiments of the present disclosure.
• FIGS. 2 and 3 illustrate embodiments of configurations of adhesive strips useful in the components and methods according to the present disclosure.
• four strips 11, 21 are used to define the shape of a gasket.
• the strips 11, 21 collectively surround openings 17, 27.
• openings 17, 27 As described above, when a gasket is die-cut from a sheet of material as shown in FIG. 1, the material cut to form the opening is typically thrown away as waste.
• strips 11 are rectangular in shape and each have the same size or approximately the same size.
• Each strip 11 has two opposing short sides 13 and two opposing long borders. Since the strips are rectangular, the long borders are referred to as long sides 19.
• the short sides 13 of the strips 11 are each cut at 90 degree angles to the long sides 19 of the strips. Also, the short sides 13 of two adjacent strips 11 are at 90 degree angles to each other.
• strips 21a and 21b are rectangular in shape, but strips 21a are longer than strips 21b.
• Each strip 21a, 21b has two opposing short sides 23 and two opposing long sides 29.
• the short sides 23 of the strips 21a, 21b are each cut at 90 degree angles to the long sides of the strips.
• the separate strips are not two concentric gaskets each surrounding the interior portion.
• the separate strips 11, 21a, 21b do not individually surround the opening 17, 27 but instead collectively surround the opening 17, 27, each forming only a portion of the perimeter of a figure or covering only a portion of the perimeter of a component of an assembly.
• the separate strips may be understood to collectively form a single gasket.
• Each of the separate strips itself does not have an aperture and is incapable of surrounding an interior portion of the component of the assembly.
• Each strip 11, 21a, 21b in the separate strips is typically identical in composition (e.g., may have the same backing and same adhesive disposed on the backing as described in some of the embodiments that follow).
• FIG. 4A One embodiment of an adhesive strip useful in the components and methods according to the present disclosure is shown in FIG. 4A.
• the adhesive strip includes a tape backing 12 having first and second opposing major surfaces. First and second major surfaces should be understood to be the surfaces of the tape backing having the greatest surface area.
• Adhesive 14 is disposed on the first major surface of the tape backing. Referring again to FIG. 2, the gap 16 is shown between the short side 13 of one adhesive strip 11 and the long side 19 of an adjacent adhesive strip.
• the size of the gap between separate strips in the components and methods according to the present disclose may depend on the size of the adhesives strips and the equipment used for positioning the adhesive strips to form a gasket.
• the gaps between adhesive strips or strips of tape backing can be up to 1 millimeter, up to 500 micrometers, up to 250 micrometers, up to 100 micrometers, up to 50 micrometers, up to 25 micrometers, up to 10 micrometers, or up to 1 micrometer.
• the adhesive strips are positioned to touch but still have a gap or interstice between them.
• FIG. 4B illustrates the cross-section shown in FIG. 4A after applying at least one of heat or pressure to the adhesive tape such that the adhesive 14 flows into and seals the spaces 16 between the separate strips of the tape backing 12.
• the sealed gap 18 can prevent the leakage of gas.
• the adhesive strips 11, 21a, 21b shown in FIGS. 2 and 3 are configured to form squares
• the adhesive strips may be arranged into any shape.
• the adhesive strips may be arranged to form a rectangle as shown in FIG. 5 or a triangle, pentagon, hexagon, octagon, or other multi-sided figure.
• Each of these shapes may be made with strips having polygonal shapes (e.g., quadrilaterals such as rectangles, trapezoids, and parallelograms). Separate strips forming two sides of a gasket may also be useful.
• L-shaped strips or other strips defining an acute or obtuse angle may be useful.
• the adhesive strips may be arranged to form a shape having non-linear borders, such as a circle or ellipse.
• the strips may have non-linear shapes such as arches (e.g., semi-circular arch, segmental arch, pointed arch, elliptical arch, or parabolic arch).
• the long borders of the strips are non-linear (e.g., arcs).
• strips including angles or arcs may be die cut from a sheet of material but may still produce less waste than a die-cut gasket such as that shown in FIG. 1 since the separate strips do not have an enclosed interior.
• each one of the at least three or four separate strips is adjacent two other of the at least three or four separate strips.
• the method and component of the present disclosure may be useful, for example, when the interior portion of the component is relatively large. As the size of the interior portion of the component increases, the amount of waste produced when die-cutting a gasket also increases.
• the method and assembly component of the present disclosure may be useful, for example, when the interior portion of the component has a surface area of at least 500 cm 2 , at least 750 cm 2 , or at least 1000 cm 2 .
• the interior portion of the component can be considered the active portion of the component (e.g., electrolyte membrane or current collector).
• the assembly of the present disclosure or made by a method of the present disclosure is a membrane electrode assembly in a fuel cell.
• a typical fuel cell system includes a power section in which one or more fuel cells generate electrical power.
• a fuel cell is an energy conversion device that converts hydrogen or other fuel and oxygen into water or water and carbon dioxide, producing electricity and heat in the process.
• Each fuel cell unit may include a proton exchange member (PEM) with gas diffusion layers, which function as diffusers and current collectors, on either side of the proton exchange member.
• Anode and cathode catalyst layers are respectively positioned between the gas diffusion layers and the PEM. This unit is referred to as a membrane electrode assembly (MEA).
• MEA membrane electrode assembly
• Separator plates are respectively positioned on the outside of the gas diffusion layers of the membrane electrode assembly.
• This type of fuel cell is often referred to as a PEM fuel cell.
• the reaction in a single MEA typically produces less than one volt. Therefore, to obtain operating voltages useful in most applications, a plurality of the MEAs may be stacked and electrically connected in series to achieve a desired voltage. Electrical current is collected from the fuel cell stack and used to drive a load. Fuel cells may be used to supply power for a variety of applications, ranging from automobiles to laptop computers.
• the efficiency of the fuel cell power system depends on the flow of reactant gases across the surfaces of the MEA as well as the integrity of the various contacting and sealing interfaces within individual fuel cells of the fuel cell stack.
• Such contacting and sealing interfaces include those associated with the transport of fuels, coolants, and effluents within and between fuel cells of the stack.
• Proper sealing of fuel cell components and assemblies within a fuel cell stack facilitates efficient operation of the fuel cell system.
• a subgasket may be deployed on the electrolyte membrane of a fuel cell, for example, to seal the active regions of the fuel cell and to provide dimensional stability to the electrolyte membrane. Under pressure, the edges of fuel cell components in the stack can cause local stress concentrations on the membrane which may cause failure of the fuel cell. Subgaskets provide support to the membranes to reduce the occurrence of this failure mechanism.
• FIG. 5 shows an exploded diagram of an embodiment of an assembly of the present disclosure or made by the method of the present disclosure.
• a membrane electrode assembly (MEA) 155 of the fuel cell 150 includes five component layers.
• An electrolyte membrane layer 152 is sandwiched between a pair of GDLs 154.
• An anode catalyst layer 156 is situated between a first GDL 154 and the membrane 152, and a cathode catalyst layer 158 is situated between the membrane 152 and a second GDL 154.
• Subgasket 110 formed from a first set of separate adhesive strips, is situated between GDL 154 and the anode catalyst layer 156, and subgasket 120, formed from a second set of separate adhesive strips, is situated between the second GDL 154 and the cathode catalyst layer 158.
• each strip 111, 121 has two opposing short sides 113, 123 and two opposing long sides 119, 129.
• the short sides 113, 123 of the strips 111, 121 are each cut at 45 degree angles to the long sides 119, 129 of the strips.
• the short sides 113, 123 of two adjacent strips 111, 121 are at 45 degree angles to each other.
• the strips are trapezoidal in shape, any of the shapes and configurations of adhesive strips described above and shown in FIGS. 2 and 3 may be useful.
• a membrane layer 152 is fabricated to include an anode catalyst layer 156 as a coating on one surface and a cathode catalyst layer 158 as a coating on the other surface.
• This structure is often referred to as a catalyst-coated membrane or CCM.
• the GDLs 154 can be fabricated to include or exclude a catalyst coating.
• an anode catalyst coating can be disposed partially on the first GDL 154 and partially on one surface of the membrane 152, and/or a cathode catalyst coating can be disposed partially on the second GDL 154 and partially on the other surface of the membrane 152.
• the electrolyte membrane is one of the more expensive components of an MEA, and it is sometimes desirable to decrease the amount of electrolyte membrane used to form fuel cell assemblies, thereby decreasing the cost of the fuel cell stacks.
• Techniques for decreasing the amount of electrolyte membrane used in an MEA is sometimes referred to as "membrane thrifting.”
• membrane thrifting is to reduce the x and/or y dimensions of the electrolyte membrane.
• electrolyte membrane 152 is "thrifted" in the x and y directions which means that electrolyte membrane extends only partially under the subgaskets 110, 120. In FIG. 5, subgaskets 110 and 120 are the same size.
• subgasket 110 may the same size or a different size from the subgasket 120. If subgaskets 110 and 120 are the same size, as depicted in FIG. 5, then the outer edges of each of the separate strips 111 aligns with corresponding outer edges of each of the separate strips 121. However if the subgaskets 110 and 120 are not the same size, then one or more outer edges of the separate strips 111 do not align with the corresponding outer edges of the second set of separate strips 121.
• the opening 117 defined by separate strips 111 may be the same size or a different size from the opening 127 defined by the second set of separate strips 121.
• openings 117 and 127 are the same size, and inner edges of the separate strips 111 align with the corresponding inner edges of the second set of separate strips 121.
• one or more inner edges of the separate strips 111 do not align with the corresponding inner edges of the second set of separate strips 121.
• MEA 155 is shown sandwiched between a first perimeter gasket 165 and a second perimeter gasket 167. Adjacent the first and second perimeter gaskets 165, 167 are flow field plates 169. Each of the flow field plates or separators 169 includes a field of fluid flow channels 168 and ports through which hydrogen and oxygen feed fuels may pass.
• flow field plates 169 are configured as unipolar flow field plates, also referred to as monopolar flow field plates, in which a single MEA 155 is sandwiched therebetween.
• a unipolar flow field plate may comprise a separator that includes a flow field side and a cooling side.
• the flow field side incorporates a field of gas flow channels 168 and ports through which hydrogen or oxygen feed fuels may pass.
• the cooling side incorporates a cooling arrangement, such as integral cooling channels.
• the cooling side may be configured to contact a separate cooling element, such as a cooling block or bladder through which a coolant passes or a heat sink element, for example.
• the perimeter gaskets 165, 167 provide sealing within the fuel cell to isolate the various fluid
• hard stop generally refers to a nearly or substantially incompressible material that does not significantly change in thickness under operating pressures and temperatures. More particularly, the term “hard stop” refers to a substantially
• MEA membrane electrode assembly
• the perimeter gaskets 165, 167 may employ one or more gaskets, sub-gaskets and/or o-rings to effect sealing of the edges of the MEA 155 and sealing between and around the MEA 155 and the flow field plates 169.
• the perimeter gaskets 165, 167 include a gasket system formed from one, two, or more layers of various selected materials employed to provide the requisite sealing within the fuel cell 150.
• Such materials include, for example, polytetrafluoroethylene, fiberglass impregnated with polytetrafluoroethylene, a variety of crosslinkable resin materials, elastomeric materials, UV curable polymeric material, surface texture material, multi-layered composite material, sealants, and silicon material.
• Other configurations employ an in-situ formed seal system.
• separate strips of an adhesive as described herein can be useful for the perimeter gaskets 165, 167 as well as the subgaskets 110, 120.
• Adhesives useful in the components and methods according to the present disclosure include amorphous fluoropolymers.
• Amorphous fluoropolymers do not exhibit a melting point. They generally have glass transition temperatures below room temperature and exhibit little or no crystallinity at room temperature.
• Amorphous fluoropolymers useful as polymer processing additives include homopolymers and/or copolymers of fluorinated olefins.
• the homopolymers or copolymers can have a fluorine atom-to-carbon atom ratio of at least 1:2, in some embodiments at least 1: 1; and/or a fluorine atom-to- hydrogen atom ratio of at least 1: 1.5.
• Amorphous fluoropolymers useful for practicing the present disclosure can comprise interpolymerized units derived from at least one partially fluorinated or perfluorinated ethylenically unsaturated monomer represented by formula wherein each R a is independently fluoro, chloro, bromo, hydrogen, a fluoroalkyl group (e.g. perfluoroalkyl having from 1 to 8, 1 to 4, or 1 to 3 carbon atoms), a fluoroalkoxy group (e.g.
• perfluoroalkoxy having from 1 to 8, 1 to 4, or 1 to 3 carbon atoms, optionally interrupted by one or more oxygen atoms), alkyl or alkoxy of from 1 to 8 carbon atoms, aryl of from 1 to 8 carbon atoms, or cyclic saturated alkyl of from 1 to 10 carbon atoms.
• Examples of useful fluorinated monomers represented by formula include vinylidene fluoride (VDF), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), chlorotrifluoroethylene, 2- chloropentafluoropropene, dichlorodifluoroethylene, 1,1-dichlorofluoroethylene, 1- hydropentafluoropropylene, 2-hydropentafluoropropylene, perfluoroalkyl perfluoro vinyl ethers, and mixtures thereof.
• VDF vinylidene fluoride
• TFE tetrafluoroethylene
• HFP hexafluoropropylene
• chlorotrifluoroethylene 2- chloropentafluoropropene
• dichlorodifluoroethylene 1,1-dichlorofluoroethylene
• 1- hydropentafluoropropylene 2-hydropentafluoropropylene
• Perfluoroalkoxyalkyl vinyl ethers suitable for making an amorphous fluoropolymer include those represented by formula in which each n is independently from 1 to 6, z is 1 or 2, and Rf2 is a linear or branched perfluoroalkyl group having from 1 to 8 carbon atoms and optionally interrupted by one or more -O- groups.
• n is from 1 to 4, or from 1 to 3, or from 2 to 3, or from 2 to 4. In some embodiments, n is 1 or 3. In some embodiments, n is 3.
• C n F2n may be linear or branched. In some embodiments, C n F 2 n can be written as (CF 2 ) n , which refers to a linear perfluoroalkylene group. In some embodiments, C n F 2 n is -CF2-CF2-CF2-. In some embodiments, C n F 2 n is branched, for example, -CF 2 -CF(CF 3 )-.
• (OC n F 2 n)z is represented by -0-(CF 2 )i-4- [0(CF2)i-t]o-i.
• Rf 2 is a linear or branched perfluoroalkyl group having from 1 to 8 (or 1 to 6) carbon atoms that is optionally interrupted by up to 4, 3, or 2 -O- groups.
• Rf 2 is a perfluoroalkyl group having from 1 to 4 carbon atoms optionally interrupted by one -O- group.
• Suitable monomers represented by formula CF 2 CFORf and
• CF 2 CFOCF 2 CF 2 CF 2 CF 2 OCF 2 CF 3
• CF 2 CFOCF 2 CF 2 OCF 2 OCF 3
• CF 2 CFOCF 2 CF 2 OCF 2 CF 2 OCF 3
• CF 2 CFOCF 2 CF 2 OCF 2 CF 2 CF 2 OCF 3
• CF 2 CFOCF 2 CF 2 OCF 2 CF 2 CF 2 OCF 3
• CF 2 CFOCF 2 CF 2 OCF 2 CF 2 CF 2 OCF 3
• CF 2 CFOCF 2 CF 2 OCF 2 CF 2 CF 2 OCF 3
• CF 2 CFOCF 2 CF 2 OCF 2 CF 2 CF 2 CF 2 CF 2 OCF 3
• CF 2 CFOCF 2 CF 2 (OCF 2 ) 3 OCF 3
• CF 2 CFOCF 2 CF 2 (OCF 2 ) 4 OCF 3
• CF 2 CFOCF 2 CF 2 OCF 2 OCF 2 OCF 3
• CF 2 CFOCF 2 CF 2 OCF 2 CF 2 CF 3
• CF 2 CFOCF 2 CF 2 OCF 2 CF 2 OCF 2 CF 2 CF 3
• CF 2 CFOCF 2 CF(CF 3 )-0-C 3 F 7 (PPVE-2)
• Many of these perfluoroalkoxyalkyl vinyl ethers can be prepared according to the methods described in U.S. Pat. Nos. 6,255,536 (Worm et al.) and 6,294,627 (Worm et al.).
• Perfluoroalkyl alkene ethers and perfluoroalkoxyalkyl alkene ethers may also be useful for making an amorphous polymer for the composition, method, and use according to the present disclosure.
• the amorphous fluoropolymers may include interpolymerized units of fluoro (alkene ether) monomers, including those described in U.S. Pat. Nos. 5,891,965 (Worm et al.) and 6,255,535 (Schulz et al.).
• Such monomers include those represented by formula wherein m is an integer from 1 to 4, and wherein Rf is a linear or branched perfluoroalkylene group that may include oxygen atoms thereby forming additional ether linkages, and wherein Rf contains from 1 to 20, in some embodiments from 1 to 10, carbon atoms in the backbone, and wherein Rf also may contain additional terminal unsaturation sites.
• m is 1.
• CF 2 CFCF 2 -0-CF 2 -0-CF 3
• CF 2 CFCF 2 -0-CF 2 CF 2 -0-CF 3
• CF 2 CFCF 2 -0-CF 2 CF 2 -0-CF 2 -0-CF 2 CF 3
• CF 2 CFCF 2 -0-CF 2 CF 2 -0-CF 2 CF 2 CF 2 -0-CF 3
• CF 2 CFCF 2 -0-CF 2 CF 2 -0-CF 2 CF 2 -0-CF 3
• CF 2 CFCF 2 -0-CF 2 CF 2 -0-CF 2 CF 2 -0-CF 3
• CF 2 CFCF 2 CF 2 -0-CF 2 CF 2 CF 3 .
• Suitable perfluoroalkoxyalkyl allyl ethers include those represented by formula in which n, z, and Rf 2 are as defined above in any of the embodiments of perfluoroalkoxyalkyl vinyl ethers.
• CF 2 CFCF 2 OCF 2 CF 2 OCF 2 OCF 3
• CF 2 CFCF 2 OCF 2 CF 2 OCF 2 CF 2 OCF 3
• CF 2 CFCF 2 OCF 2 CF 2 OCF 2 CF 2 CF 2 OCF 3
• CF 2 CFCF 2 OCF 2 CF 2 OCF 2 CF 2 CF 2 OCF 3
• CF 2 CFCF 2 OCF 2 CF 2 OCF 2 CF 2 CF 2 CF 2 OCF 3
• CF 2 CFCF 2 OCF 2 CF 2 (OCF 2 ) 3 OCF 3
• CF2 CFCF20CF2CF(CF 3 )-0-C 3 F 7
• CF2 CFCF2(OCF2CF(CF 3 ))2-0-C 3 F 7
• Many of these perfluoroalkoxyalkyl allyl ethers can be prepared, for example, according to the methods described in U.S. Pat. No. 4,349,650 (Krespan).
• An amorphous fluoropolymer useful for practicing the present disclosure may also comprise interpolymerized units derived from the interpolymerization of at least one monomer with at least one non-fluorinated, copolymerizable comonomer represented by formula wherein each R b is independently hydrogen, chloro, alkyl having from 1 to 8, 1 to 4, or 1 to 3 carbon atoms, a cyclic saturated alkyl group having from 1 to 10, 1 to 8, or 1 to 4 carbon atoms, or an aryl group of from 1 to 8 carbon atoms.
• Examples of useful monomers represented by formula include ethylene and propylene.
• Perfluoro-l,3-dioxoles may also be useful to prepare the amorphous fluoropolymer.
• useful amorphous copolymers of fluorinated olefins are those derived, for example, from vinylidene fluoride and one or more additional olefins, which may or may not be fluorinated (e.g., represented by formula
• useful fluoropolymers include copolymers of vinylidene fluoride with at least one terminally unsaturated fluoromonoolefin represented by formula containing at least one fluorine atom on each double-bonded carbon atom.
• Examples of comonomers that can be useful with vinylidene fluoride include hexafluoropropylene, chlorotrifluoroethylene, 1 iydropentafluoropropylene, and 2-hydropentafluoropropylene.
• Other examples of amorphous fluoropolymers useful for practicing the present disclosure include copolymers of vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene or 1- or 2-hydropentafluoropropylene and copolymers of tetrafluoroethylene, propylene, and, optionally, vinylidene fluoride.
• the amorphous fluoropolymer is a copolymer of hexafluoropropylene and vinylidene fluoride. In some embodiments, the amorphous fluoropolymer is a copolymer of perfluoropropylene, vinylidene fluoride and tetrafluoroethylene.
• Amorphous fluoropolymers including interpolymerized units of VDF and HFP typically have from 30 to 90 percent by weight VDF units and 70 to 10 percent by weight HFP units.
• Amorphous fluoropolymers including interpolymerized units of TFE and propylene typically have from about 50 to 80 percent by weight TFE units and from 50 to 20 percent by weight propylene units.
• Amorphous fluoropolymers including interpolymerized units of TFE, VDF, and propylene typically have from about 45 to 80 percent by weight TFE units, 5 to 40 percent by weight VDF units, and from 10 to 25 percent by weight propylene units.
• Those skilled in the art are capable of selecting specific interpolymerized units at appropriate amounts to form an amorphous fluoropolymer.
• polymerized units derived from non-fluorinated olefin monomers are present in the amorphous fluoropolymer at up to 25 mole percent of the fluoropolymer, in some embodiments up to 10 mole percent or up to 3 mole percent.
• polymerized units derived from at least one of perfluoroalkyl vinyl ether or perfluoroalkoxyalkyl vinyl ether monomers are present in the amorphous fluoropolymer at up to 50 mole percent of the fluoropolymer, in some embodiments up to 30 mole percent or up to 10 mole percent.
• VDF/CF 2 CFOC 3 F 7 copolymer, an ethylene/HFP copolymer, a TFE/ HFP copolymer, a CTFE/VDF copolymer, a TFE/VDF copolymer, a TFE/VDF/PMVE/ethylene copolymer, or a
• TFE/VDF/CF 2 CFO(CF 2 )30CF 3 copolymer.
• Amorphous fluoropolymers useful for the components and methods according to the present disclosure are capable of being crosslinked. That is, the amorphous fluoropolymer typically has a cure site.
• the amorphous fluoropolymer can include a chloro, bromo-, or iodo- cure site or a combination thereof.
• the amorphous fluoropolymer comprises a bromo- or iodo-cure site.
• the amorphous fluoropolymer comprises an iodo-cure site.
• the cure site can be an iodo-, bromo-, or chloro- group chemically bonded at the end of a fluoropolymer chain.
• the weight percent of elemental iodine, bromine, or chlorine in the amorphous fluoropolymer may range from about 0.2 wt.% to about 2 wt.%, and, in some embodiments, from about 0.3 wt.% to about 1 wt.%.
• an iodo-chain transfer agent, a bromo-chain transfer agent, a chloro-chain transfer agent, or any combination thereof can be used in the polymerization process.
• suitable iodo-chain transfer agents include perfluoroalkyl or chloroperfluoroalkyl groups having 3 to 12 carbon atoms and one or two iodo- groups.
• iodo-perfluoro-compounds include 1,3-diiodoperfluoropropane, 1,4-diiodoperfluorobutane, 1,6- diiodoperfluorohexane, 1,8-diiodoperfluorooctane, 1, 10-diiodoperfluorodecane, 1, 12- diiodoperfluorododecane, 2-iodo-l,2-dichloro-l, l,2-trifluoroethane, 4-iodo-l,2,4-trichloroperfluorobutane and mixtures thereof.
• Suitable bromo-chain transfer agents include perfluoroalkyl or
• chloroperfluoroalkyl groups having 3 to 12 carbon atoms and one or two bromo-groups.
• Chloro-, bromo-, and iodo- cure sites may also be incorporated into the amorphous fluoropolymer by including at least one cure site monomer in the polymerization reaction.
• non-fluorinated bromo-or iodo-substituted olefins e.g., vinyl iodide and allyl iodide, can be used.
• CF 2 CFCF 2 OCH 2 CH 2 I
• CF 2 CFO(CF 2 ) 3 OCF 2 CF 2 I
• CH 2 CHBr
• CF 2 CHBr
• CF 2 CFBr
• amorphous fluoropolymer when the amorphous fluoropolymer is perhalogenated, in some embodiments perfluorinated, typically at least 50 mole percent (mol %) of its interpolymerized units are derived from TFE and/or CTFE, optionally including HFP.
• the balance of the interpolymerized units of the amorphous fluoropolymer (10 to 50 mol %) is made up of one or more perfluoroalkyl vinyl ethers and/or perfluoroalkoxyalkyl vinyl ethers, and a suitable cure site monomer.
• the fluoropolymer When the fluoropolymer is not perfluorinated, it typically contains from about 5 mol % to about 95 mol % of its interpolymerized units derived from TFE, CTFE, and/or HFP, from about 5 mol % to about 90 mol % of its
• interpolymerized units derived from VDF, ethylene, and/or propylene up to about 40 mol % of its interpolymerized units derived from a vinyl ether, and from about 0.1 mol % to about 5 mol %, in some embodiments from about 0.3 mol % to about 2 mol %, of a suitable cure site monomer.
• the amorphous fluoropolymer presently disclosed is typically prepared by a sequence of steps, which can include polymerization, coagulation, washing, and drying.
• an aqueous emulsion polymerization can be carried out continuously under steady-state conditions.
• an aqueous emulsion of monomers e.g,. including any of those described above
• water, emulsifiers, buffers and catalysts are fed continuously to a stirred reactor under optimum pressure and temperature conditions while the resulting emulsion or suspension is continuously removed.
• batch or semibatch polymerization is conducted by feeding the aforementioned ingredients into a stirred reactor and allowing them to react at a set temperature for a specified length of time or by charging ingredients into the reactor and feeding the monomers into the reactor to maintain a constant pressure until a desired amount of polymer is formed.
• unreacted monomers are removed from the reactor effluent latex by vaporization at reduced pressure.
• the amorphous fluoropolymer can be recovered from the latex by coagulation.
• the polymerization is generally conducted in the presence of a free radical initiator system, such as ammonium persulfate.
• the polymerization reaction may further include other components such as chain transfer agents and complexing agents.
• the polymerization is generally carried out at a temperature in a range from 10 °C and 100 °C, or in a range from 30 °C and 80 °C.
• the polymerization pressure is usually in the range of 0.3 MPa to 30 MPa, and in some embodiments in the range of 2 MPa and 20 MPa.
• perfluorinated or partially fluorinated emulsifiers may be useful. Generally these fluorinated emulsifiers are present in a range from about 0.02% to about 3% by weight with respect to the polymer. Polymer particles produced with a fluorinated emulsifier typically have an average diameter, as determined by dynamic light scattering techniques, in range of about 10 nanometers (nm) to about 300 nm, and in some embodiments in range of about 50 nm to about 200 nm.
• emulsifiers perfluorinated and partially fluorinated emulsifier having the formula [Rf-0-L-COO " ]iX 1+ wherein L represents a linear partially or fully fluorinated alkylene group or an aliphatic hydrocarbon group, Rf represents a linear partially or fully fluorinated aliphatic group or a linear partially or fully fluorinated aliphatic group interrupted with one or more oxygen atoms, X 1+ represents a cation having the valence i and i is 1, 2 or 3. (See, e.g. U.S. Pat. No. 2007/0015864 to Hinzter et al.).
• Suitable emulsifiers also include perfluorinated polyether emulsifiers having the formula CF3-(OCF 2 ) m -0-CF 2 -X, wherein m has a value of 1 to 6 and X represents a carboxylic acid group or salt thereof, and the formula CF 3 -0-(CF 2 )3-(OCF(CF 3 )-CF 2 ) z -0-L-Y wherein z has a value of 0, 1, 2 or 3, L represents a divalent linking group selected from-CF(CF 3 )-,-CF 2 -and-CF 2 CF 2 -and Y represents a carboxylic acid group or salt thereof.
• perfluorinated polyether emulsifiers having the formula CF3-(OCF 2 ) m -0-CF 2 -X, wherein m has a value of 1 to 6 and X represents a carboxylic acid group or salt thereof, and the formula CF 3 -0-(CF 2 )3
• Suitable emulsifiers include perfluorinated polyether emulsifiers having the formula Rf-0(CF 2 CF 2 0) m CF 2 COOA wherein Rf is C n F( 2n +i); where n is 1 to 4, A is a hydrogen atom, an alkali metal or NH 4 , and m is an integer of from 1 to 3. (See, e.g., U.S. Pat. No. 2006/0199898 to Funaki; Hiroshi et al.).
• Suitable emulsifiers also include perfluorinated emulsifiers having the formula F(CF 2 )nO(CF 2 CF 2 0)mCF 2 COOA wherein A is a hydrogen atom, an alkali metal or NH 4 , n is an integer of from 3 to 10, and m is 0 or an integer of from 1 to 3.
• perfluorinated emulsifiers having the formula F(CF 2 )nO(CF 2 CF 2 0)mCF 2 COOA wherein A is a hydrogen atom, an alkali metal or NH 4 , n is an integer of from 3 to 10, and m is 0 or an integer of from 1 to 3.
• Further suitable emulsifiers include fluorinated polyether emulsifiers as described in U.S. Pat. No. 6,429,258 to Morgan et al.
• perfluoroalkyl component of the perfluoroalkoxy has 4 to 12 carbon atoms, or 7 to 12 carbon atoms.
• Suitable emulsifiers also include partially fluorinated polyether emulsifiers having the formula [Rf-(0) t -CHF-(CF 2 ) n -COO-]iX 1+ wherein Rf represents a partially or fully fluorinated aliphatic group optionally interrupted with one or more oxygen atoms, t is 0 or 1 and n is 0 or 1, X 1+ represents a cation having a valence i and i is 1, 2 or 3. (See, e.g.
• emulsifiers include perfluorinated or partially fluorinated ether containing emulsifiers as described in U.S. Pat. Publ. Nos. 2006/0223924 to Tsuda; Nobuhiko et al., 2007/0060699 to Tsuda; Nobuhiko et al, 2007/0142513 to Tsuda; Nobuhiko et al and 2006/0281946 to Morita; Shigeru et al.
• Fluoroalkyl for example, perfluoroalkyl, carboxylic acids and salts thereof having 6-20 carbon atoms, such as ammonium perfluorooctanoate (APFO) and ammonium perfluorononanoate.
• APFO ammonium perfluorooctanoate
• U.S. Pat. No. 2,559,752 to Berry may also be useful.
• the emulsifiers can be removed or recycled from the fluoropolymer latex as described in U.S. Pat. Nos. 5,442,097 (Obermeier et al.), 6,613,941 (Felix et al.), 6,794,550 (Hintzer et al.), 6,706,193 (Burkard et al.), and 7,018,541 (Hintzer et al.).
• the polymerization process may be conducted with no emulsifier (e.g., no fluorinated emulsifier).
• Polymer particles produced without an emulsifier typically have an average diameter, as determined by dynamic light scattering techniques, in a range of about 40 nm to about 500 nm, typically in range of about 100 nm and about 400 nm, and suspension polymerization will typically produce particles sizes up to several millimeters.
• a water soluble initiator can be useful to start the polymerization process.
• Salts of peroxy sulfuric acid such as ammonium persulfate, are typically applied either alone or sometimes in the presence of a reducing agent, such as bisulfites or sulfinates (disclosed in U.S. Pat. Nos. 5,285,002 Grootaert and 5,378,782 to Grootaert) or the sodium salt of hydroxy methane sulfinic acid (sold under the trade designation "RONGALIT", BASF Chemical Company, New Jersey, USA). Most of these initiators and the emulsifiers have an optimum pH -range where they show most efficiency. For this reason, buffers are sometimes useful.
• Buffers include phosphate, acetate or carbonate buffers or any other acid or base, such as ammonia or alkali metal hydroxides.
• concentration range for the initiators and buffers can vary from 0.01% to 5% by weight based on the aqueous polymerization medium.
• the chain transfer agents having the cure site and/or the cure site monomers can be fed into the reactor by batch charge or continuously feeding. Because feed amount of chain transfer agent and/or cure site monomer is relatively small compared to the monomer feeds, continuous feeding of small amounts of chain transfer agent and/or cure site monomer into the reactor is difficult to control. Continuous feeding can be achieved by a blend of the iodo-chain transfer agent in one or more monomers. Examples of monomers useful for such a blend include hexafluoropropylene (HFP) and perfluoromethyl vinyl ether (PMVE).
• HFP hexafluoropropylene
• PMVE perfluoromethyl vinyl ether
• any coagulant which is commonly used for coagulation of a fluoropolymer latex may be used, and it may, for example, be a water soluble salt (e.g., calcium chloride, magnesium chloride, aluminum chloride or aluminum nitrate), an acid (e.g., nitric acid, hydrochloric acid or sulfuric acid), or a water-soluble organic liquid (e.g., alcohol or acetone).
• the amount of the coagulant to be added may be in range of 0.001 to 20 parts by mass, for example, in a range of 0.01 to 10 parts by mass per 100 parts by mass of the amorphous fluoropolymer latex.
• the amorphous fluoropolymer latex may be frozen for coagulation.
• the coagulated amorphous fluoropolymer can be collected by filtration and washed with water.
• the washing water may, for example, be ion exchanged water, pure water, or ultrapure water.
• the amount of the washing water may be from 1 to 5 times by mass to the amorphous fluoropolymer, whereby the amount of the emulsifier attached to the amorphous fluoropolymer can be sufficiently reduced by one washing.
• amorphous fluoropolymers useful for practicing the present disclosure have weight average molecular weights in a range from 10,000 grams per mole to 200,000 grams per mole. In some embodiments, the weight average molecular weight is at least 15,000, 20,000, 25,000, 30,000, 40,000, or 50,000 grams per mole up to 100,000, 150,000, 160,000, 170,000, 180,000, or up to 190,000 grams per mole.
• Amorphous fluoropolymers disclosed herein typically have a distribution of molecular weights and compositions. Weight average molecular weights can be measured, for example, by gel permeation chromatography (i.e., size exclusion chromatography) using techniques known to one of skill in the art.
• Viscosity of amorphous fluoropolymers typically decreases with decreasing molecular weight.
• Amorphous fluoropolymers are often described by their Mooney viscosities rather than their molecular weights.
• Amorphous fluoropolymers useful for practicing the present disclosure may have a Mooney viscosity in a range from 0.1 to 150 (ML 1+10) at 100 °C according to ASTM D1646-06 TYPE A.
• amorphous fluoropolymers useful for practicing the present disclosure have a
• Mooney viscosity in a range from 0.1 to 100, 0.1 to 50, 0.1 to 20, 0.1 to 10, or 0.1 to 5 (ML 1+10) at 100 °C according to ASTM D1646-06 TYPE A.
• the amorphous fluoropolymer useful in the assemblies and methods according to the present disclosure has a storage modulus (G 1 ) at 25 °C and 6.3 rad/s of at least 300 kPa and at 25 °C and 0.1 rad/s of up to 200 kPa. In some embodiments, the amorphous fluoropolymer has a storage modulus (G 1 ) at 25 °C and 6.3 rad/s of at least 400 kPa and at 25 °C and 0.1 rad/s of up to 100 kPa. In these embodiments, the amorphous fluoropolymer may not be tacky on its own, which may be useful for processing the amorphous fluoropolymer.
• amorphous fluoropolymers useful for practicing the present disclosure having a storage modulus (G) of less than about 300 kPa at 6.3 rad/s (1 Hz).
• the amorphous fluoropolymer may be tacky on its own, which may be beneficial to the adhesion of adhesive tapes in the assemblies and methods disclosed herein.
• the adhesive useful for the assemblies and methods according to the present disclosure includes a peroxide.
• peroxides useful for practicing the present disclosure are acyl peroxides. Acyl peroxides tend to decompose at lower temperatures than alkyl peroxides and allow for lower temperature curing.
• the peroxide is di(4-/- butylcyclohexyl)peroxydicarbonate, di(2-phenoxyethyl)peroxydicarbonate, di(2,4-dichlorobenzoyl) peroxide, dilauroyl peroxide, decanoyl peroxide, l,l,3,3-tetramethylethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, disuccinic acid peroxide, /-hexyl peroxy-2- ethylhexanoate, di(4-methylbenzoyl) peroxide, t-butyl peroxy-2-ethylhexanoate, benzoyl peroxide, t- butylperoxy 2-ethylhexyl carbonate, or t-butylper
• the peroxide is a diacyl peroxide.
• the peroxide is benzoyl peroxide or a substituted benzoyl peroxide (e.g., di(4-methylbenzoyl) peroxide or di(2,4-dichlorobenzoyl) peroxide).
• the peroxide is typically present in the adhesive in an amount effective to cure the adhesive.
• the peroxide is present in the adhesive in a range from 0.5% by weight to 10% by weight versus the weight of the adhesive.
• the peroxide is present in the adhesive in a range from 1% by weight to 5% by weight versus the weight of the adhesive.
• crosslinkers may be useful, for example, for providing enhanced mechanical strength in the final cured adhesive.
• adhesive useful for the assemblies and methods according to the present disclosure further comprises a crosslinker.
• crosslinker Those skilled in the art are capable of selecting conventional crosslinkers based on desired physical properties.
• the crosslinker is typically present in an amount of 1% by weight to 10% by weight versus the weight of the curable composition. In some embodiments, the crosslinker is present in a range from 2% by weight to 5% by weight versus the weight of the curable composition.
• the amorphous fluoropolymer useful in the assemblies and methods disclosed herein may include nitrogen- containing cure sites. These can be incorporated into amorphous fluoropolymers using nitrogen- containing monomers and/or nitrogen-containing chain-transfer agents.
• monomers comprising nitrogen-containing groups useful in preparing fluoropolymers comprising a nitrogen- containing cure sites include free -radically polymerizable nitriles, imidates, amidines, amides, imides, and amine-oxides. Mixtures of any of these nitrogen-containing cure sites may be useful in the fluoropolymer compositions according to the present disclosure.
• Nitrogen-containing cure sites can also be incorporated into the amorphous fluoropolymer by employing selected chain transfer agents (e.g., I(CF2) (j CN in which d is
• Nitriles for example, when heated in the presence of organometallic compounds of arsenic, antimony, and tin and/or organo onium compounds such as those described in U.S. Pat. No. 7,989,552 (Grootaert et al.) can trimerize and form triazine rings to crosslink the amorphous fluoropolymer.
• Fluoropolymers in particular VDF containing amorphous fluoropolymers, may also be cured using a polyhydroxy curing system. In such instance, it will not be required that the fluoropolymer includes cure site components.
• the polyhydroxy curing system generally comprises one or more polyhydroxy compounds and one or more organo-onium accelerators.
• the useful organo-onium compounds typically contain at least one heteroatom, i.e., a non-carbon atom such as N, P, S, O, bonded to organic or inorganic moieties.
• One useful class of quaternary organo-onium compounds broadly comprises relatively positive and relatively negative ions wherein a phosphorus, arsenic, antimony or nitrogen generally comprises the central atom of the positive ion.
• the negative ion may be an organic or inorganic anion (e.g., halide, sulfate, acetate, phosphate, phosphonate, hydroxide, alkoxide, phenoxide, bisphenoxide, etc.).
• organic or inorganic anion e.g., halide, sulfate, acetate, phosphate, phosphonate, hydroxide, alkoxide, phenoxide, bisphenoxide, etc.
• organo-onium accelerators include those described in U.S. Pat. Nos. 4,233,421 (Worm), 4,912,171 (Grootaert et al.), 5,086,123 (Guenthner et al.), 5,262,490 (Kolb et al.), and 5,929,169 (Coggio et al.).
• useful organo-onium compounds include those having one or more pendent fluorinated alkyl groups.
• the polyhydroxy compound may be used in its free or non-salt form or as the anionic portion of a chosen organo-onium accelerator.
• useful polyhydroxy compounds for forming cured fluoroelastomers include those disclosed in U.S. Pat. Nos. 3,876,654 (Pattison) and 4,233,421 (Worm).
• the polyhydroxy compound is an aromatic polyphenol such as 4,4'-hexafluoroisopropylidenyl bisphenol (bisphenol AF), 4,4'- dihydroxydiphenyl sulfone (bisphenol S), and 4,4'-isopropylidenyl bisphenol (bisphenol A).
• bisphenol AF 4,4'-hexafluoroisopropylidenyl bisphenol
• bisphenol S 4,4'- dihydroxydiphenyl sulfone
• bisphenol A 4,4'-isopropylidenyl bisphenol
• Fluoropolymers in particular VDF containing amorphous fluoropolymers, may also be cured using a polyamine curing system.
• useful polyamines include N,N-dicinnamylidene-l,6- hexanediamine, trimethylenediamine, cinnamylidene trimethylenediamine, cinnamylidene
• ethylenediamine, and cinnamylidene hexamethylenediamine Useful polyamines may be protected as carbamates. Examples of useful carbamates are hexamethylenediamine carbamate, bis(4- aminocyclohexyl)methane carbamate, 1,3-diaminopropane monocarbamate, ethylenediamine carbamate and trimethylenediamine carbamate. Usually about 0.1-5 phr of the diamine is used.
• the adhesive useful for the assemblies and methods according to the present disclosure includes a plasticizer.
• a plasticizer may be useful, for example, for increasing the tackiness of the adhesive.
• the plasticizer may be an amorphous fluoropolymer incapable of crosslinking, for example. Any of the monomers (other than cure-site monomers) and methods described above may be useful for making such amorphous fluoropolymers.
• Useful plasticizers can also include
• perfluoropolyethers such as those described, for example, U.S. Pat. No. 5,268,405 (Ojakaar et al.).
• the plasticizer is an ionic liquid.
• An ionic liquid is in a liquid state at about 100 °C or less. Ionic liquids typically have negligible vapor pressure and high thermal stability.
• the ionic liquid is composed of a cation and an anion and typically has a melting point of about 100 ° C or less (i.e., it is a liquid at about 100 ° C or less), about 95 ° C or less, or about 80 ° C or less. Certain ionic liquids have melting points that allow them to be in a molten state even at ambient temperature, and therefore they are sometimes referred to as ambient temperature molten salts.
• the cation and/or anion of the ionic liquid are relatively sterically -bulky, and typically one or both of these ions are an organic ion.
• the ionic liquid can be synthesized by known methods, for example, by a process such as anion exchange or metathesis process or via an acid-base or neutralization process.
• the cation of the ionic liquid may be an ammonium ion, a phosphonium ion, or a sulfonium ion, for example, including various delocalized heteroaromatic cations.
• suitable ammonium ions include alkylammonium, imidazolium, pyridinium, pyrrolidinium, pyrrolinium, pyrazinium, pyrimidinium, triazonium, triazinium, quinolinium, isoquinolinium, indolinium, quinoxalinium, piperidinium, oxazolinium, thiazolinium, morpholinium, piperazinium, and combinations thereof.
• Suitable phosphonium ions include tetraalkylphosphonium, arylphosphonium,
• alkylarylphosphonium and combinations thereof examples include alkylsulfonium, arylsulfonium, thiophenium, tetrahydrothiophenium, and combinations thereof.
• the alkyl group directly bonded to nitrogen atom, phosphorus atom, or sulfur atom may be a linear, branched or cyclic alkyl group having at least 1, 2, or 4 carbon atoms and typically up to 8, 10, 12, 15, or 20 carbon atoms.
• the alkyl group may optionally contain heteroatoms such as O and N and S in the chain or at the end of the chain (e.g., a terminal -OH group).
• the aryl group directly bonded to nitrogen atom, phosphorus atom, or sulfur atom may be a monocyclic or condensed cyclic aryl group having at least 5, 6, or 8 carbon atoms and typically up to 12, 15, or 20 carbon atoms.
• any of these cations may be further substituted by an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an aryl group, an aralkyl group, an arylalkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a carbonyl group, a carboxyl group, an ester group, an acyl group, an amino group, a dialkylamino group, an amide group, an imino group, an imide group, a nitro group, a nitrile group, a sulfide group, a sulfoxide group, a sulfone group, or a halogen atom, and a heteroatom such as oxygen atom, nitrogen atom, sulfur atom and silicon atom may be contained in the main chain or ring of the structure constituting the cation.
• suitable cations include N-ethyl-N'-methylimidazolium, N-methyl-N- propylpiperidinium, N,N,N-trimethyl-N-propylammonium, N-methyl-N,N,N-tripropylammonium, N,N,N-trimethyl-N-butylammoniuim, N,N,N-trimethyl-N-methoxyethylammonium, N-methyl-N,N,N- tris(methoxyethyl)ammonium, N,N-dimethyl-N-butyl-N-methoxyethylammonium, N,N-dimethyl-N,N- dibutylammonium, N-methyl-N,N-dibutyl-N-methoxyethylammonium, N-methyl-N,N,N- tributylammonium, N,N,N-trimethyl-N-hexylammonium, N,N,
• the cation does not contain a functional group or reactive moiety (for example, an unsaturated bond). In some of these embodiments, heat resistance of the ionic liquid is maximized.
• alkyl and/or aryl groups in the cation are substituted with fluorine atoms, and advantageous compatibility with the amorphous fluoropolymer may result.
• R-OSO3- a sulfate
• R-SO3- sulfonate
• R-CO2- carboxylate
• R-CO2- a phosphate
• each R may be independently a hydrogen atom, a halogen atom (fluorine, chlorine, bromine, iodine), or a substituted or unsubstituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl, aralkyl, arylalkyl, acyl or sulfonyl group.
• a heteroatom such as an oxygen atom, a nitrogen atom, and a sulfur atom may be contained in the main chain or ring of the group R, and a part or all of hydrogen atoms on the carbon atom of the group R may be replaced with fluorine atoms.
• these R groups may be the same or different.
• anions containing perfluoroalkyl groups include a bis(perfluoroalkylsulfonyl)imide ((RfS02)2 -), a perfluoroalkylsulfonate (RfSC -) and a
• RfS02 tris(perfluoroalkylsulfonyl)methide ((RfS02)3C-) (wherein Rf represents a perfluoroalkyl group).
• the perfluoroalkyl group can include at least 1, 2, 3 or 4 carbon atoms and typically up to 8, 10, 12, 15, or 20 carbon atoms.
• suitable bis(perfluoroalkylsulfonyl)imides include
• Suitable perfluoroalkylsulfonates include trifluoromethane sulfonate, pentafluoroethanesulfonate,
• tris(perfluoroalkylsulfonyl)methides include tris(tafluoromethanesulfonyl)methide
• ionic liquids suitable as plasticizers in the adhesive useful in the assemblies and methods according to the present disclosure include N-methyl-N-propylpiperidinium
• the absolute value of the solubility parameter difference between amorphous fluoropolymer (5 a ) and ionic liquid (5b) is less than or equal to 8.2 (MPa) 1/2 [4 (cal/cc) 1/2 ], in other words,
• the absolute value of the solubility parameter difference between fluoropolymer (5 a ) and ionic liquid (5b) is less than or equal to 6.1 (MPa) 1/2 [3 (cal/cc) 1/2 ] or less than or equal to 4.1 (MPa) 1/2
• the solubility parameter of ionic liquids can be calculated using computer simulation. See, for example, Bela Derecskei and Agnes Derecskei-Kovacs, "Molecular modelling simulations to predict density and solubility parameters of ionic liquids", Molecular Simulation, Vol. 34 (2008) 1167 -1175.
• the solubility parameter, ⁇ , of a fluoroelastomer including VDF and HFP in a 78/22 molar ratio is reported to be 8.7 (cal/cc) 1/2 (17.8 (MPa) 1/2 ) in Myers and Abu-Isa, Journal of Applied Polymer Science, Vol. 32, 3515-3539 (1986).
• the solubility parameter of an amorphous fluoropolymer is considered to be 17.8 (MPa) 1/2
• the ionic liquid has a solubility parameter in a range from 9.6 (MPa) 1/2 to 26 (MPa) 1/2 , in some embodiments, 11.7 (MPa) 1/2 to 23.9 (MPa) 1/2 , and in some embodiments, 13.7 (MPa) 1/2 to 21.9 (MPa) 1/2 .
• Additives such as carbon black, dyes, pigments, stabilizers, lubricants, fillers, and processing aids typically utilized in fluoropolymer compounding can be incorporated into the adhesives useful in the components and methods disclosed herein, provided they have adequate stability for the intended service conditions.
• Carbon black fillers can be employed in fluoropolymers as a means to balance modulus, tensile strength, elongation, hardness, abrasion resistance, conductivity, and processability of the compositions. Suitable examples include MT blacks (medium thermal black) and large particle size furnace blacks. When used, 1 to 100 parts filler per hundred parts fluoropolymer (phr) of large size particle black is generally sufficient.
• Fluoropolymer fillers may also be present in the adhesive. Generally, from 1 to 100 phr of fluoropolymer filler is used.
• the fluoropolymer filler can be finely divided and easily dispersed as a solid at the highest temperature used in fabrication and curing of the adhesive. By solid, it is meant that the filler material, if partially crystalline, will have a crystalline melting temperature above the processing temperature(s) of the curable composition(s).
• One way to incorporate fluoropolymer filler is by blending latices. This procedure, using various kinds of fluoropolymer filler, is described in U.S. Pat. No.
• Examples of other fillers that may be useful for balancing modulus, tensile strength, elongation, hardness, abrasion resistance, conductivity, and processability include clay, silica (S1O2), alumina, iron red, talc, diatomaceous earth, barium sulfate, wollastonite (CaSiC ), calcium carbonate (CaCC ), calcium fluoride, titanium oxide, and iron oxide.
• the adhesive useful in the components and methods disclosed herein is free of fillers or contains less than 5%, 2%, or 1% by weight fillers versus the weight of the adhesive.
• the curable composition according to the present disclosure can be free of inorganic fillers.
• One advantage to avoiding fillers in the curable compositions disclosed herein is that visible light transmissive adhesives may be obtained, which may be useful for some applications.
• acid acceptors may be employed to facilitate the cure and thermal stability of the adhesive.
• Suitable acid acceptors may include magnesium oxide, lead oxide, calcium oxide, calcium hydroxide, dibasic lead phosphite, zinc oxide, barium carbonate, strontium hydroxide, calcium carbonate, hydrotalcite, alkali stearates, magnesium oxalate, or combinations thereof.
• the acid acceptors can be used in amounts ranging from about 1 to about 20 parts per 100 parts by weight of the amorphous fluoropolymer.
• the adhesive is free of such adjuvants or includes less than 0.5% by weight of such adjuvants versus the weight of the adhesive.
• amorphous fluoropolymers having relatively low molecular weights can be useful for making adhesives with lower viscosity for coating onto a tape backing to make a tape.
• solvents useful for practicing the present disclosure include ketones, esters, carbonates, and formates such as tert-butyl acetate, 4-methyl-2- pentanone, n-butyl acetate, ethyl acetate, 2-butanone, ethyl formate, methyl acetate, cyclohexanone, dimethyl carbonate, acetone, and methyl formate.
• the solvent is not an alcohol, which tend to be particularly detrimental to a peroxide-cure.
• Compounding can be carried out, for example, on a roll mill (e.g., two-roll mill), internal mixer (e.g., Banbury mixers), or other rubber-mixing device. Thorough mixing is typically desirable to distribute the components and additives uniformly throughout the adhesive composition so that it can cure effectively.
• the compounding can be carried out in one or several steps. For example, certain components such as the crosslinker may be compounded into a mixture of the amorphous fluoropolymer, solvent, and catalyst just before use. Also the solvent may be compounded into a mixture of the amorphous fluoropolymer, peroxide, and optionally crosslinker in a second step. It is typically desirable that the temperature of the composition during mixing should not rise high enough to initiate curing. For example, the temperature of the composition may be kept at or below about 50 °C.
• the tape backing comprises at least one of a polyamide, a polycarbonate, a modified polyphenylene ether, a polyester, a fluoroplastic, polyphenylene sulfide, polysulfone, polyarylate, polyetherimide, polyimide, polyethersulfone, polyether ketone, or polystyrene.
• Fluoroplastics useful as tape backings include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-fluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, ethylene- chlorotrifluoroethylene copolymer, tetrafluoroethylene-perfluorodioxole copolymer, polyvinylidene fluoride-hexafluoropropylene copolymer.
• the tape backing includes
• the backing surface that comes into contact with the adhesive may be subjected to a surface treatment.
• the surface treatment may at least partially fluorinate the backing. Examples of the surface treatment which can be used include plasma treatment using a fluorine-containing gas, and coating of a conventional fluorine-containing primer.
• the plasma treatment using a fluorine-containing gas can be performed, for example, by using octafluoropropane (C3F8) as the fluorine-containing gas, using, if desired, tetramethylsilane (TMS) and oxygen in combination, and flowing these gases at a flow rate of 50 to 500 SCCM in WAF'R/BATCH 7000 Series manufactured by Plasma-Therm under the conditions of a chamber pressure of 10 to 1,000 mTorr, an output of 50 to 2,000 W and a treatment time of 0.1 to 10 minutes.
• C3F8 octafluoropropane
• TMS tetramethylsilane
• the adhesive disposed on the tape backing is a pressure sensitive adhesive (PSA), and the adhesive tape useful for practicing the present disclosure is a pressure-sensitive adhesive tape.
• PSAs are well known to those of ordinary skill in the art to possess properties including the following: (1) aggressive and permanent tack, (2) adherence with no more than finger pressure, (3) sufficient ability to hold onto an adherend, and (4) sufficient cohesive strength to be cleanly removable from the adherend.
• Materials that have been found to function well as PSAs are polymers designed and formulated to exhibit the requisite viscoelastic properties resulting in a desired balance of tack, peel adhesion, and shear holding power.
• Examples of commercially available tapes suitable for use in the components and methods according to the present disclosure include an adhesive tape with a PTFE backing and a fluoroelastomer adhesive, available under the trade designation, "CIPG 1951" from 3M Company, St. Paul, MN.
• the amorphous fluoropolymer may be partially cured. That is, before or after the adhesive is coated onto the tape backing, the adhesive composition may be heated to cause partial crosslinking of the amorphous fluoropolymer.
• the temperature for making a partially cured amorphous fluoropolymer can be selected, for example, based on the decomposition temperature of the peroxide. For example, a temperature can be selected that is above (in some embodiments, at least 10 °C, 20 °C, or 30 °C above) the ten-hour half-life temperature of the peroxide.
• the cure time can be selected such that full curing of the amorphous fluoropolymer does not occur. Partial curing of the amorphous fluoropolymer can be useful for modifying its viscoelastic properties to improve the handling or stability of the tape or to increase tackiness, for example.
• the method according to the present disclosure includes providing a component of an assembly having an interior portion and a peripheral portion, adhering separate strips of an adhesive tape to the peripheral portion of the component to surround the interior portion, and applying at least one of heat or pressure to the adhesive tape such that the adhesive seals any gaps (described above) between the separate strips of adhesive tape and crosslinks.
• the adhesive tape can be as described as above in any of its embodiments. Crosslinking the adhesive improves the compression set resistance and other physical properties of the adhesive.
• Example 1 Evidence that the method according to the present disclosure can seal gaps between the separate strips of adhesive is provided in the Examples, below.
• a cavity was formed in a test apparatus between an aluminum plate, an elastomeric die-cut seal such as that shown in FIG. 1, and a piece of polyimide film.
• a hole provided in the aluminum plate was connected to an air supply to provide pressure in the cavity.
• Four separate strips of adhesive tape in a configuration shown in FIG. 2 were applied to the polyimide film according to the method of the present disclosure. Heat and pressure were applied to the adhesive tape to crosslink the adhesive.
• the polyimide film with the separate strips was then placed on the elastomeric seal in the test apparatus, and a second aluminum plate was clamped on top of the polyimide film.
• the method of the present disclose can seal gaps between separate strips of adhesive tape prevent gas leakage in an assembly.
• Applying at least one of heat or pressure to the adhesive tape such that the adhesive flows and crosslinks can include heating at a temperature in a range from about 100 °C to 220 °C, in some embodiments, from about 110 °C to 180 °C, for a period of about 1 minute to about 15 hours, usually for about 1 to 15 minutes.
• the temperature during cure is sometimes raised gradually from the lower limit of the range to the desired maximum temperature.
• the adhesive tape useful in the method according to the present disclosure can be a single-sided tape, or an adhesive as described above in any of its embodiments may also be provided on both major surfaces of a tape backing to form a double-sided tape.
• Either a double-sided or single-sided tape may be useful in a membrane electrode assembly such as that illustrated in FIG. 5.
• a single-sided tape may be useful for adhering the tape backing to one of an electrolyte membrane or a gas diffusion layer.
• a double-sided tape may provide a subgasket 110 that can adhere to both the electrolyte membrane 152 and the gas diffusion layer 154.
• the adhesive tape can be applied to electrolyte membrane, the gas diffusion layer, or both. Either the electrolyte membrane or the gas diffusion layer may be catalyst-coated.
• a double-sided adhesive tape may be applied between an electrolyte membrane, which may be a catalyst-coated electrolyte membrane, and a gas diffusion layer and cured with at least one of heat or pressure.
• an electrolyte membrane which may be a catalyst-coated electrolyte membrane, and a gas diffusion layer and cured with at least one of heat or pressure.
• any gaps between the separate strips of adhesive in the membrane electrode assembly can be sealed with the crosslinked amorphous fluoropolymer.
• the method further comprises removing a release liner from the adhesive of the adhesive tape before adhering the separate strips of the adhesive tape to the peripheral portion of the component.
• a release liner can be a paper liner or polymer film made, for example, from any of the polymers described above for the tape backing.
• the release liner includes a release surface which can be a release coating (e.g., a silicone, fluorochemical, or carbamate coating) on the paper backing or polymeric film.
• a release liner is useful for protecting an adhesive surface before it is applied to the surface of the component.
• the adhesive tape may have two release liners.
• the adhesive strips are strips from an adhesive transfer tape.
• the method may include removing at least one of a release liner or backing before applying at least one of heat and pressure to the adhesive tape. After removing at least one of a release liner or backing from the transfer tape, the resulting assembly may no longer include the tape backing.
• applying at least one of heat or pressure to the separate strips can result in a single, continuous layer of crosslinked adhesive, with no gaps between the adhesive strips.
• the separate adhesive strips in the methods and components according to the present disclosure can be applied to an individual component, for example in a membrane electrode assembly as shown in FIG. 5.
• the separate adhesive strips may also be applied to a fuel cell roll good subassembly having a plurality of individual electrolyte membranes.
• Sets of separate adhesive strips can be attached to the individual electrolyte membranes in the roll.
• Each of the sets of the separate adhesive strips can be attached to the peripheral portion of an individual electrolyte membrane in an arrangement that allows the center regions of the individual electrolyte membranes to be exposed.
• Second sets of separate adhesive strips can be attached to the individual electrolyte membranes in the roll on a side opposite the first set of separate adhesive strips, for example.
• Each of the second set of separate strips is arranged on peripheral portion of the individual electrolyte membranes on the opposite side so that second surfaces of the center regions of the individual electrolyte membranes are exposed. Individual electrolyte membranes with attached adhesive strips may then be cut from the roll.
• the separate adhesive strips collectively form a first subgasket on a first peripheral surface of the electrolyte membrane.
• the membrane electrode assembly further includes a second set of separate adhesive strips having first surfaces adhered to an opposing second peripheral surface of the electrolyte membrane to surround the interior portion. A short side of a fifth adhesive strip is positioned adjacent a sixth adhesive strip, for example.
• adhesive comprising a crosslinked amorphous fluoropolymer disposed on the first surfaces of the second set of separate strips of the tape backing seals any gaps between the second set of separate adhesive strips and adheres the second set of separate adhesive strips to the opposing second peripheral surface of the electrolyte membrane.
• useful assemblies may have only one set of separate adhesive strips collectively forming a single subgasket.
• Any electrolyte membrane suitable for use in a fuel cell, flow battery, or other electrochemical cell, may be used in the practice of the present disclosure.
• useful PEM thicknesses can range between about 200 micrometers and about 1 micrometer.
• membrane electrode assemblies described herein include catalyst layers.
• Catalyst layers may comprise Pt or Pt alloys coated onto larger carbon particles by wet chemical methods, such as reduction of chloroplatinc acid. This form of catalyst is dispersed with ionomeric binders and/or solvents to form an ink, paste, or dispersion that is applied either to the membrane, a release liner, or current collector.
• the catalyst layers may comprise nanostructured support elements bearing particles or nanostructured thin films (NSTF) of catalytic material.
• Nanostructured catalyst layers generally do not contain carbon particles as supports and therefore may be incorporated into very thin surface layers of the electrolyte membrane forming a dense distribution of catalyst particles.
• the use of nanostructured thin film (NSTF) catalyst layers can provide much higher catalyst utilization than catalyst layers formed by dispersion methods and can typically offer more resistance to corrosion at high potentials and temperatures due to the absence of carbon supports.
• the catalyst surface area of a CCM may be further enhanced by using an electrolyte membrane having
• NSTF catalyst layers comprise elongated nanoscopic particles that may be formed by vacuum deposition of catalyst materials on to acicular nanostructured supports.
• Suitable nanostructured supports may comprise whiskers of organic pigment, such as C.I. PIGMENT RED 149 (perylene red).
• the crystalline whiskers can have substantially uniform but not identical cross-sections, and high length-to-width ratios.
• the nanostructured support whiskers are coated with coating materials suitable for catalysis, and which endow the whiskers with a fine nanoscopic surface structure capable of acting as multiple catalytic sites.
• the nanostructured support whiskers may be extended through continued screw dislocation growth. Lengthening the nanostructured support elements allows for an increased surface area for catalysis.
• the nanostructured support whiskers are coated with a catalyst material to form a nanostructured thin film catalyst layer.
• the catalyst material comprises a metal, such as a platinum group metal.
• the catalyst coated nanostructured support elements may be transferred to a surface of an electrolyte membrane to form a catalyst coated membrane.
• the catalyst coated nanostructured support elements maybe formed on a GDL surface.
• a current collector may have one or more of the following functions: 1) maximizing the electrical contact with electrodes thereby minimizing the resistivity due to long transverse paths of current in the electrodes, 2) serving as the electrode itself (e.g., for some flow batteries), 3) lowering resistance with contact with the backing plates, 4) transferring heat from an ME A to backing plates, 5) allowing flow of reactants (fuel and oxidant, or reductant and oxidant) with minimal pressure drop and uniform distribution of reactants on the surface of an MEA, and 6) allowing easy removal of reaction products, such as water.
• current collectors are typically electrically conductive and porous. Desirably, materials for current collectors are selected to be electrochemically stable under the reaction conditions of the electrochemical cell.
• current collectors useful as components in membrane electrode assemblies and methods according to the present disclosure can be any material capable of collecting electrical current from the electrode while allowing reactant gasses to pass through, typically a woven or non- woven carbon fiber paper or cloth.
• current collectors In fuel cells, current collectors (GDLs) provide porous access of gaseous reactants and water vapor to the catalyst and membrane, and also collect the electronic current generated in the catalyst layer for powering the external load.
• the current collector in the components and methods described herein may include a microporous layer (MPL) and an electrode backing layer (EBL), where the MPL is disposed between the catalyst layer and the EBL.
• EBLs may be any suitable electrically conductive porous substrate, such as carbon fiber constructions (e.g., woven and non-woven carbon fiber constructions). Examples of commercially available carbon fiber constructions include trade designated "AvCarb P50" carbon fiber paper from Ballard Material Products, Lowell, MA; "Toray” carbon paper which may be obtained from
• EBLs may also be treated to increase or impart hydrophobic properties.
• EBLs may be treated with highly -fluorinated polymers, such as polytetrafluoroethylene (PTFE) and fluorinated ethylene propylene (FEP).
• PTFE polytetrafluoroethylene
• FEP fluorinated ethylene propylene
• the carbon fiber constructions of EBLs generally have coarse and porous surfaces, which exhibit low bonding adhesion with catalyst layers.
• the microporous layer may be coated to the surface of EBLs. This smoothens the coarse and porous surfaces of EBLs, which provides enhanced bonding adhesion with some types of catalyst layers.
• electrolysis cells can be useful in electrochemical devices other than fuel cells, for example, an electrolysis cell, which uses electricity to produce chemical changes or chemical energy. Electrolysis cells are also called electrolyzers.
• An example of an electrolysis cell is a chlor-alkali membrane cell where aqueous sodium chloride is electrolyzed by an electric current between an anode and a cathode. The electrolyte is separated into an anolyte portion and a catholyte portion by a membrane subject to harsh conditions.
• chlor-alkali membrane cells caustic sodium hydroxide collects in the catholyte portion, hydrogen gas is evolved at the cathode portion, and chlorine gas is evolved from the sodium chloride-rich anolyte portion at the anode.
• Separate adhesive strips can be applied to chlor-alkali membranes in some embodiments of the methods and assemblies disclosed herein.
• a flow battery typically uses electrolyte liquids pumped from separate tanks past a membrane between two electrodes.
• the electrolyte solutions are typically acidic and made with 2M to 5M sulfuric acid.
• the method according to the present disclosure may also be useful for an electrode in other electrochemical cells (for example, lithium ion batteries).
• powdered active ingredients can be dispersed in a solvent with a polymer binder and coated onto a metal foil substrate, or current collector.
• the resulting composite electrode contains the powdered active ingredient in the polymer binder adhered to the metal substrate.
• Useful active materials for making negative electrodes include alloys of main group elements and conductive powders such as graphite.
• Example of useful active materials for making a negative electrode include oxides (tin oxide), carbon compounds (e.g., artificial graphite, natural graphite, soil black lead, expanded graphite, and scaly graphite), silicon carbide compounds, silicon-oxide compounds, titanium sulfides, and boron carbide compounds.
• Useful active materials for making positive electrodes include lithium compounds, such as Li 4 /3Ti 5 /30 4 , L1V3O8, LiV 2 0 5 , LiCoo.2Nio.8O2, LiNi0 2 , LiFeP0 4 , LiMnP0 4 , L1C0PO4, LiMn 2 0 4 , and L1C0O2.
• the electrodes can also include electrically conductive diluents and adhesion promoters.
• the separate adhesive strips disclosed herein can be useful, for example, to fill voids in, coat, adhere to, seal, and protect various substrates from chemical permeation, corrosion, and abrasion, for example.
• the method according to the present disclosure can be useful, for example, for hard disk drive assemblies, semiconductor devices, electrolyzers, battery electrode assemblies, and for bonding fluoroelastomer gaskets, for example, to metal in various applications.
• the present disclosure provides a method of making an assembly, the method comprising:
• the present disclosure provides the method of the first embodiment, wherein the adhesive is a transfer tape, the method further comprising removing the backing before applying heat and pressure to the separate strips.
• the present disclosure provides the method of the first or second embodiment, wherein there are at least three (or four) of the separate strips of the adhesive tape adhered to the peripheral portion of the component to surround the interior portion, wherein each one of the at least three (or four) separate strips is adjacent two other of the at least three (or four) separate strips, and wherein applying at least one of heat or pressure to the separate strips of the adhesive tape seals any gaps between the separate strips of the adhesive tape.
• the present disclosure provides the method of any one of the first to third embodiments, wherein the amorphous fluoropolymer comprises a bromo- or iodo- cure site.
• the present disclosure provides the method of any one of the first to fourth embodiments, wherein the adhesive further comprises a crosslinker.
• the present disclosure provides the method of any one of the first to sixth embodiments, wherein the adhesive further comprises a peroxide.
• the present disclosure provides the method of the seventh embodiment, wherein the peroxide is an acyl peroxide or a diacyl peroxide.
• the present disclosure provides the method of any one of the first to eighth embodiments, wherein the assembly is a membrane electrode assembly, and wherein the component comprises at least one of an electrolyte membrane or a current collector.
• the present disclosure provides a component of a membrane electrode assembly, the component comprising:
• an electrolyte membrane or a current collector having an interior portion and a peripheral portion
• a short side of a first strip of the tape backing is positioned adjacent a second strip of the tape backing, wherein an adhesive disposed on the first surfaces of the separate strips of the tape backing seals a gap between the first and second strips of the tape backing and adheres the separate strips to the peripheral portion of the component, and wherein the adhesive comprises a crosslinked amorphous fluoropolymer. None of the separate strips individually can surround the interior portion.
• the present disclosure provides the membrane electrode assembly component of the tenth embodiment, wherein there are at least three (or four) of the separate strips of the tape backing adhered to the peripheral portion of the component to surround the interior portion, wherein each one of the at least three (or four) separate strips is adjacent two other of the at least three (or four) separate strips, and wherein the adhesive disposed on the first surfaces of the separate strips of the tape backing seals gaps between the separate strips of the tape backing.
• the present disclosure provides the membrane electrode assembly component of the tenth or eleventh embodiment, wherein the crosslinked amorphous fluoropolymer is a peroxide-crosslinked amorphous fluoropolymer.
• the present disclosure provides the method or membrane electrode assembly component of any one of the first or third to twelfth embodiments, wherein the adhesive tape is a single-sided adhesive tape.
• the present disclosure provides the method or membrane electrode assembly component of any one of the first or third to twelfth embodiments, wherein the adhesive tape has the adhesive disposed on two opposing surfaces of the backing.
• the present disclosure provides the method or membrane electrode assembly component of any one of the first or third to fourteenth embodiments, wherein the tape backing comprises at least one of a polyamide, a polycarbonate, a modified polyphenylene ether, a polyester, a fluoroplastic, polyphenylene sulfide, polysulfone, polyarylate, polyetherimide, polyimide,
• the present disclosure provides the method or membrane electrode assembly component of any one of the first to fifteenth embodiments, wherein the adhesive further comprises a plasticizer.
• the present disclosure provides the method or membrane electrode assembly component of the sixteenth embodiment, wherein the plasticizer comprises an ionic liquid having an anion and a cation.
• the present disclosure provides the method or membrane electrode assembly component of the seventeenth embodiment, wherein the cation of the ionic liquid is selected from N-ethyl-N'-methylimidazolium N-methyl-N-propylpiperidinium, N,N,N-trimethyl-N- propylammonium, N-methyl-N,N,N-tripropylammonium, N,N,N-trimethyl-N-butylammoniuim, ⁇ , ⁇ , ⁇ - trimethyl-N-methoxyethylammonium, N-methyl-N,N,N-tris(methoxyethyl)ammonium, N-methyl-N,N,N- tributylammonium, N,N,N-trimethyl-N-hexylammonium, N,N-diethyl-N-methyl-N-(2- methoxyethyl)ammonium, 1-propyl-tetrahydrothiophenium,
• the present disclosure provides the method or membrane electrode assembly component of the seventeenth or eighteenth embodiment, wherein the anion of the ionic liquid is selected from bis(trifluoromethanesulfonyl) imide, bis(pentafluoroethanesulfonyl)imide,
• the present disclosure provides the method or membrane electrode assembly component of any one of the first to nineteenth embodiments, wherein the interior portion of the component has a surface area of at least 500 cm 2 .
• the present disclosure provides the method or membrane electrode assembly component of any one of the first to twentieth embodiments, wherein the component is an electrolyte membrane, and wherein the separate strips of the tape backing collectively form a first subgasket on a first peripheral surface of the electrolyte membrane.
• the present disclosure provides the method or membrane electrode assembly component of the twenty -first embodiment, wherein the electrolyte membrane further comprises a second set of separate strips of the tape backing having first surfaces adhered to an opposing second peripheral surface of the electrolyte membrane to surround the interior portion, wherein a short side of a fifth strip of the tape backing is positioned adjacent a sixth strip of the tape backing, wherein adhesive comprising a crosslinked amorphous fluoropolymer disposed on the first surfaces of the second set of separate strips of the tape backing seals a gap between the fifth and sixth strips of the tape backing and adheres the second set of separate strips to the opposing second peripheral surface of the electrolyte membrane.
• the present disclosure provides the method or membrane electrode assembly component of any one of the first to twentieth embodiments, wherein the component is an electrolyte membrane.
• the present disclosure provides the method or membrane electrode assembly component of any one of the first to twenty -third embodiments, wherein the component is a catalyst coated membrane.
• the present disclosure provides the method or membrane electrode assembly component of any one of the first to twentieth embodiments, wherein the component is a current collector.
• the present disclosure provides the method or membrane electrode assembly component of any one of the first to twentieth embodiments, wherein the component is a catalyst coated current collector.
• the present disclosure provides an electrochemical cell comprising the membrane electrode assembly component of or made by the method of any one of the first to twenty -sixth embodiments.
• the present disclosure provides a fuel cell comprising the membrane electrode assembly component of or made by the method of any one of the first to twenty-sixth embodiments.
• the present disclosure provides a flow battery comprising the membrane electrode assembly component of or made by the method of any one of the first to twenty-sixth embodiments.
• the present disclosure provides a component of a membrane electrode assembly, the component comprising:
• an electrolyte membrane or a current collector having an interior portion and a peripheral portion
• each of the separate adhesive strips comprises an adhesive comprising an amorphous fluoropolymer. None of the separate strips individually can surround the interior portion.
• the present disclosure provides the component of the thirtieth embodiment, wherein there are at least three or four of the separate adhesive strips disposed on the peripheral portion of the component to surround the interior portion, wherein each one of the at least three or four separate adhesive strips is adjacent two other of the at least three or four separate adhesive strips.
• the present disclosure provides the component of the thirtieth or thirty -first embodiment, wherein the interior portion of the component has a surface area of at least 500 cm 2 .
• the present disclosure provides the component any one of the thirtieth to thirty-second embodiments, wherein the separate adhesive strips each comprise the adhesive disposed on a tape backing.
• the present disclosure provides the component of the thirty -third embodiment, wherein the separate adhesive strips each comprise a single-sided adhesive tape.
• the present disclosure provides the component of the thirty -third embodiment, wherein the separate adhesive strips each comprise the adhesive disposed on two opposing surfaces of the backing.
• the present disclosure provides the component of the thirty -fourth or thirty -fifth embodiment, wherein the tape backing comprises at least one of a polyamide, a polycarbonate, a modified polyphenylene ether, a polyester, a fluoroplastic, polyphenylene sulfide, polysulfone, polyarylate, polyetherimide, polyimide, polyethersulfone, polyether ketone, or polystyrene.
• the present disclosure provides the component of any one of the thirtieth to thirty-sixth embodiments, wherein the amorphous fluoropolymer comprises a bromo- or iodo- cure site.
• the present disclosure provides the component of any one of the thirtieth to thirty -seventh embodiments, wherein the adhesive further comprises a crosslinker.
• the crosslinker comprises at least one of tri(methyl)allyl isocyanurate, triallyl isocyanurate, tri(methyl)allyl cyanurate, poly -triallyl isocyanurate, x
• the present disclosure provides the component of any one of the thirtieth to thirty -ninth embodiments, wherein the adhesive further comprises a peroxide.
• the present disclosure provides the component of the fortieth embodiment, wherein the peroxide is an acyl peroxide or a diacyl peroxide.
• the present disclosure provides the component of any one of the thirtieth to forty -first embodiments, wherein the adhesive further comprises a plasticizer.
• the present disclosure provides the component of the forty-second embodiment, wherein the plasticizer comprises an ionic liquid having an anion and a cation.
• the present disclosure provides the component of the forty -third embodiment, wherein the cation of the ionic liquid is selected from N-ethyl-N'-methylimidazolium N- methyl-N-propylpiperidinium, N,N,N-trimethyl-N-propylammonium, N-methyl-N,N,N- tripropylammonium, N,N,N-trimethyl-N-butylammoniuim, N,N,N-trimethyl-N-methoxyethylammonium, N-methyl-N,N,N-tris(methoxyethyl)ammonium, N-methyl-N,N,N-tributylammonium, ⁇ , ⁇ , ⁇ -trimethyl- N-hexy lammonium,
• the present disclosure provides the component of the forty -third or forty -fourth embodiment, wherein the anion of the ionic liquid is selected from
• the present disclosure provides the component of any one of the thirtieth to forty -fifth embodiments, wherein the component is an electrolyte membrane.
• the present disclosure provides the component of any one of the thirtieth to forty -fifth embodiments, wherein the component is a catalyst coated membrane.
• the present disclosure provides the component of any one of the thirtieth to forty -fifth embodiments, wherein the component is a current collector.
• the present disclosure provides the component of any one of the thirtieth to forty -fifth embodiments, wherein the component is a catalyst coated current collector.
• the present disclosure provides an electrochemical cell comprising the component of any one of the thirtieth to forty -ninth embodiments.
• the present disclosure provides a fuel cell comprising the component of any one of the thirtieth to forty -ninth embodiments.
• the present disclosure provides a flow battery comprising the component of any one of the thirtieth to forty -ninth embodiments.
• the testing apparatus included two square, aluminum plates of thickness 1.27 cm (0.5 in.) and with 100 mm edges. The center of one square plate was pierced by a threaded hole allowing connection of the plate to a compressed air supply. Centered on the pierced plate was a die-cut elastomer seal, the gasket of an example or counter example laminated to a square piece of KAPTON® film with 101.6 mm (4 in) edges, and the other square plate. The laminated film was placed between the elastomer and aluminum plate, with the tape contacting both the KAPTON® film and the elastomer.
• Peel strength was measured using an INSTRON® Model 1125 Tester, available from Instron Corp.,
• test specimens were either cured with heat and pressure at 130 °C and 275 kPa (40 psi) for 3 min and allowed to cool to room temperature before testing, or tested immediately • The value reported is an average of determinations for three samples
• the gasket was made from 25.4 mm wide adhesive strips cut to 76.2 mm (3 in) lengths. The strips were arranged on a piece of KAPTON® film, with the adhesive side of each strip facing the film, in the arrangement shown in Figure 2.
• the gasket was cured with heat and pressure of 130°C and 275 kPa (40 psi) applied for 3 min using a heat press (obtained from Wabash MPI, Wabash, IN). After cooling to room temperature, the gasket was pressure tested. The results of the pressure test are summarized in Table 2, below.
• a gasket was made and tested as in EX-1 except the gasket was die-cut from adhesive strips made in the same way as CIPG 1951 but not cut to 25.4 mm wide strips.
• the die-cut gasket had a square perimeter with 101.6 mm (4 in) sides and a square of material with 50.8 mm (2 in) sides removed from the center, centered within the perimeter.
• the results of the pressure test are summarized in Table 2.
• the gasket was made as described for EX-1, except that the gasket was not cured with heat and pressure.
• the results of the pressure test are summarized in Table 2.
• the gasket was made as described for IE-1, except that the gasket was not cured with heat and pressure.
• the results of the pressure test are summarized in Table 2.
• Peel strength was measured for strips of CIPG 1951 adhered to a KAPTON® substrate and cured prior to testing. The peel strength is reported in Table 3, below.
• Peel strength was measured for strips of CIPG 1951 adhered to a stainless steel substrate and cured prior to testing. The peel strength is reported in Table 3.
• Peel strength was measured as described for EX-3, except that the strips of CIPG 1951 were not cured prior to testing. The peel strength is reported in Table 3.

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• 2017
  • 2017-06-15 EP EP17814061.2A patent/EP3472885A4/en not_active Withdrawn
  • 2017-06-15 WO PCT/US2017/037604 patent/WO2017218731A1/en not_active Ceased
  • 2017-06-15 KR KR1020197000931A patent/KR20190020032A/ko not_active Ceased
  • 2017-06-15 CN CN201780037600.7A patent/CN109314256A/zh active Pending
  • 2017-06-15 JP JP2018565658A patent/JP2019521483A/ja not_active Withdrawn
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