Method for preparing polymer composite having reduced gas permeability and enhanced durability, and gasket comprising same

Abstract

The present invention relates to a method for preparing a polymer composite for a gasket for a fuel cell or water electrolysis stack, and specifically, a preparation method of the present invention provides a method for preparing a polymer composite that is based on ethylene-propylene diene monomer (EPDM) rubber or polydimethylsiloxane (PDMS) silicone. A polymer composite comprising a PMA-BNNNF nanofiller, prepared by the present invention, uses the PMA-BNNNF nanofiller as a crosslinking agent so as to enable increasing the crosslink density of the crosslinking agent and reducing gas permeability, and has the advantage of having excellent compression set, crosslink density, hydrogen permeability, and acid resistance, and thus may be used for a gasket for a fuel cell or water electrolysis stack having excellent performance.

Description

Method for manufacturing a polymer composite with reduced gas permeability and improved durability, and a gasket including the same

[0001] The present invention relates to a method for manufacturing a polymer composite for a gasket for a fuel cell or water electrolysis stack, and specifically, to a method for manufacturing a polymer composite for a gasket with reduced gas permeability and improved durability.

[0002] Project ID: 2710006251

[0003] Project Number: KN24-94

[0004] Ministry Name: Ministry of Science and ICT

[0005] Project Management (Specialized) Agency Name: National Research Foundation of Korea

[0006] Research Project Name: Nanomaterial Technology Development

[0007] Research Project Title: Control Program for *H / *CO Intermediates for High-Concentration Liquid C2+ Product Production

[0008] Development of Mumble Nanocatalysts and Electrolytic Systems

[0009] Project Executing Organization Name: Korea Research Institute of Chemical Technology

[0010] Research Period: April 1, 2024 – December 31, 2024

[0011] Project ID: Not Assigned

[0012] Project No.: KS2422-20

[0013] Ministry Name: Ministry of Science and ICT

[0014] Project Management (Specialized) Agency Name: Korea Research Institute of Chemical Technology

[0015] Research Project Name: Basic Project

[0016] Research Project Title: Development of Core Materials for Renewable Energy-Linked Energy Conversion

[0017] Project Executing Organization Name: Korea Research Institute of Chemical Technology

[0018] Research Period: April 1, 2024 – December 31, 2024

[0019] Generally, gaskets are products widely used as sealing materials across all industrial sectors, including petrochemicals, power plants, shipbuilding and marine industries, heavy industry, construction, and offshore plants. Their purpose is to prevent fluid leakage within pipes, and in particular, to prevent leakage of byproducts, reactants, and cooling water during the fabrication of fuel cell or water electrolysis stacks.

[0020] Gaskets in use can be classified into metallic, semi-metallic, and non-metallic types, with non-metallic gaskets being the most commonly seen. Non-metallic gaskets are made of materials such as graphite, non-asbestos, Teflon, and rubber, and are called soft gaskets because they are softer than metals. Compared to metal gasket sheets, they are easy to restore after compression and are used at low temperatures and pressures (around 200°C or below, 50K or below).

[0021] Meanwhile, the most important performance characteristics of a gasket are fluid airtightness and heat resistance. In particular, high heat resistance is a key requirement for gaskets in recent years, and major domestic and international users, including developed countries, are demanding improved heat resistance to reduce maintenance and management costs.

[0022] As a related prior art, Korean Published Patent Application No. 10-2009-0116837 describes a gasket using graphite, which aims to improve airtightness, vibration absorption, corrosion resistance, and wear resistance of the gasket by manufacturing the gasket using a mixture of graphite and a binder acting as a binder in a 2:1 ratio. However, in the case of gaskets using graphite or carbon fiber as described in the above prior art, although they can be used under temperature conditions of 500℃, they have problems such as poor flexibility and handling due to the use of carbon material and a binder content of approximately 1 weight%, as well as material costs, poor working environments, and high oxidability.

[0023] Meanwhile, ethylene-propylene diene monomer (EPDM) rubber has traditionally been used as a gasket for fuel cells or water electrolysis. However, due to various problems with EPDM rubber, liquid silicon rubber, which has relatively strong durability, has been developed and is being used.

[0024] However, both EPDM and silicone rubber still require improvement due to their insufficient durability and low gas permeability, and new materials are needed to address the reduced manufacturing costs and volumetric power density of stacks containing these gaskets.

[0025] Therefore, in order to solve this problem, there is a demand in the field for the development of polymer composites that possess low gas permeability and high durability, even when used as thin gaskets.

[0026] The prior art is as follows.

[0027] Korean Publication No. 2024-0122994 (Publication Date: August 13, 2024) relates to a metal adhesive gasket having a sub-sealing structure disposed between a housing and a cover to prevent gas leakage, comprising: a carrier having an upper surface and a lower surface made of metal material; a main sealing bonded to the inner end of the carrier to maintain airtightness inside the housing; and a sub-sealing bonded to the outer end of the carrier to block external fluid penetration.

[0028] Korean Registered Patent No. 10-2678524 (Registration Date June 21, 2024) relates to a composition of a fuel cell gasket and the fuel cell gasket said, characterized by comprising 10 to 20 parts by weight of ethylene-octene copolymer, 30 to 40 parts by weight of carbon black, 2 to 6 parts by weight of a crosslinking agent, and 5 to 20 parts by weight of process oil, based on 100 parts by weight of ethylene-propylene rubber (EPDM), which has a Mooney viscosity of 20 to 30 (ML1+4, 125℃) and is a terpolymer of ethylene, propylene, and ethylidene norbornene.

[0029] Korean Publication No. 2024-0083360 (Publication Date June 12, 2024) relates to a rubber gasket for a CA electrolytic cell for improving durability and a method for manufacturing the same. The invention relates to a rubber gasket for a CA electrolytic cell comprising a rubber layer including a mixed EPDM elastic material in which EPDM rubber and EPDM-g-MA are mixed, a reinforcing layer including a polyamide-based fabric, and a PTFE thin film deposited on three surfaces of the reinforcing layer that come into contact with the electrolyte, and a method for manufacturing the same.

[0030] Korean Patent Registration No. 10-2662505 (Registration Date: April 26, 2024) relates to a gasket composition having excellent heat resistance, oxidation resistance, and flexibility, a method for manufacturing a gasket using the composition, and a gasket structure manufactured using the method. It provides a non-carbon gasket composition comprising potassium titanate fibers having strength and stiffness equivalent to carbon fibers, an organic binder, reinforcing fibers, an inorganic filler, and an inorganic binder, and relates to a method for manufacturing a gasket and a structure having a structure in which a support layer made of a metal material is inserted between sealing layer sheets made of the composition as described above.

[0031] Korean Patent Registration No. 10-2602857 (Registration Date: November 13, 2023) relates to a gasket for a fuel cell and a fuel cell including the same, and relates to a gasket that may include a polymer base layer formed from a polymer base layer composition including a polymer base and carbon composite material particles, and a fuel cell including the same.

[0032] However, the prior art does not teach or imply a polymer composite for gaskets containing nanofillers that increase the crosslinking density of the crosslinking agent and reduce gas permeability.

[0033] The objective of the present invention is to solve the problems of the prior art by providing a method for manufacturing a polymer composite for gaskets having high durability and low gas permeability.

[0034] Meanwhile, the technical problems to be solved by the present invention are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which the present invention belongs from the description below.

[0035] To achieve the above objective, one aspect of the present invention is a method for manufacturing a polymer composite for a gasket of a fuel cell or a water electrolysis stack, comprising the steps of: mixing and stirring hexagonal boron-nitride (h-BN) and 1-pyrenemethyl methacrylate (PMA) in a solvent to produce exfoliated PMA-BNNNF (1-Pyrenemethyl methacrylate-boronnitride nanoflake) nanofillers (Step 1); adding and stirring dicumyl peroxide and the exfoliated PMA-BNNNF nanofillers obtained in Step 1 to ethylene-propylene diene monomer (EPDM) rubber dissolved in a solvent to produce partially crosslinked PMA-BNNF / EPDM by chemical reaction (Step 2); and drying the produced PMA-BNNF / EPDM rubber to remove the solvent (Step 3). The present invention provides a method comprising the step (step 4) of fully curing the solvent-removed PMA-BNNF / EPDM rubber to produce a PMA-BNNF / EPDM polymer composite.

[0036] In addition, another aspect of the present invention provides a method for manufacturing a polymer composite for a gasket of a fuel cell or a stack for water electrolysis, comprising the steps of: mixing and stirring hexagonal boron-nitride (h-BN) and 1-pyrenemethyl methacrylate (PMA) in a solvent to produce exfoliated PMA-BNNNF nanofillers (Step 1); adding and stirring a polydimethylsiloxane (PDMS) silicon oligomer, a polydimethylsiloxane (PDMS) silicon curing agent, and the exfoliated PMA-BNNNF nanofillers obtained in Step 1 in a solvent to produce partially cross-linked PMA-BNNF / PDMS silicon by chemical reaction (Step 2); drying the produced PMA-BNNF / PDMS silicon to remove the solvent (Step 3); and fully curing the solvent-removed PMA-BNNF / PDMS silicon to produce a PMA-BNNF / PDMS polymer composite (Step 4).

[0037] A preferred embodiment of one aspect or another aspect of the present invention is characterized in that, in step 1, the solvent is N,N-dimethylformamide (DMF) and the weight ratio of PMA to h-BN is 1:1.

[0038] A preferred embodiment of one or another aspect of the present invention is characterized by, after mixing and stirring in step 1, ultrasonically treating using an ultrasonic processor, filtering the solvent through membrane filter filtration to extract PMA-BNNF nanofillers, and evaporating the remaining solvent from the extracted PMA-BNNF nanofillers through vacuum drying to produce exfoliated PMA-BNNF nanofillers.

[0039] A preferred embodiment of one aspect of the present invention is characterized in that, in step 2, the solvent is n-hexane, and the addition, stirring, and crosslinking reaction is carried out at a temperature of 70 to 90°C.

[0040] A preferred embodiment of another aspect of the present invention is characterized in that, in step 2, the solvent is acetone, is added at a temperature of 70 to 90°C, and is stirred and crosslinked at a temperature of 70 to 90°C.

[0041] A preferred embodiment of one or another aspect of the present invention is characterized in that the exfoliated PMA-BNNNF nanofiller is added in a range of 0.3% to 0.6% by weight based on 100% by weight of the polymer composite, and is stirred and crosslinked at a temperature of 70 to 90°C.

[0042] A preferred embodiment of one aspect or another aspect of the present invention is characterized in that the drying is performed in a vacuum oven at 50 to 70°C.

[0043] A preferred embodiment of one aspect or another aspect of the present invention is characterized in that the curing is performed in a hot press at a temperature of 130 to 150°C and a pressure of 1400 bar to 1600 bar.

[0044] Another aspect of the present invention provides a gasket for a fuel cell or water electrolysis stack comprising a polymer composite of the present invention.

[0045] According to the present invention, a polymer composite comprising PMA-BNNNF nanofillers prepared by the present invention can increase the crosslinking density of the crosslinking agent and reduce gas permeability by using PMA-BNNNF nanofillers as a crosslinking agent. Specifically, it has the advantages of excellent thermal properties and improved mechanical properties, as well as excellent permanent compression set, crosslinking density, hydrogen permeability, and acid resistance, and thus can be used as a gasket for a fuel cell or water electrolysis stack having excellent performance.

[0046] However, the effects obtainable from the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description below.

[0047] Figure 1 is a drawing illustrating the ASTM D638 test standard.

[0048] Figure 2 is a graph showing the size distribution of the nanofiller of the present invention.

[0049] Figure 3 is a photograph showing the shape of ① an EPDM-based cross-linked polymer composite and ② a silicon-based cross-linked polymer composite according to the nanofiller content.

[0050] Figure 4 is a graph showing the thermal properties of ① EPDM cross-linked polymer composite and ② silicone-based cross-linked polymer composite.

[0051] Figure 5 is a graph showing the mechanical properties of ① EPDM cross-linked polymer composite and ② silicon-based cross-linked polymer composite.

[0052] Figure 6 shows SEM images of the fracture surfaces of ① EPDM cross-linked polymer composites and ② silicon-based cross-linked polymer composites according to nanofiller (crosslinking agent) content.

[0053] Figure 7 is a graph showing the results of the permanent compression set of ① EPDM cross-linked polymer composites and ② silicone-based cross-linked polymer composites according to the nanofiller (crosslinking agent) content.

[0054] Figure 8 is a graph showing the crosslinking density of ① EPDM crosslinked polymer composite and ② silicone-based crosslinked polymer composite according to the nanofiller (crosslinking agent) content.

[0055] Figure 9 is a graph showing the hydrogen permeability of ① EPDM cross-linked polymer composites and ② silicon-based cross-linked polymer composites according to the nanofiller (crosslinking agent) content.

[0056] Figure 10 is a graph showing the results of the chemical accelerated endurance evaluation of ① EPDM cross-linked polymer composites and ② silicone-based cross-linked polymer composites in an acidic solution according to the nanofiller (crosslinking agent) content.

[0057] Figure 11 is a graph showing the results of chemical accelerated endurance evaluation of ① EPDM cross-linked polymer composites and ② silicone-based cross-linked polymer composites in a basic solution according to nanofiller (crosslinking agent) content.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by a skilled expert in the art to which this invention pertains. In general, the nomenclature used herein is well known and commonly used in the art.

[0059] Throughout this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0060] The present invention will be described in detail below.

[0061] One aspect of the present invention provides a method for manufacturing a polymer composite for a gasket of a fuel cell or a stack for water electrolysis. Specifically, the manufacturing method of the present invention provides a method for manufacturing an ethylene-propylene diene monomer (EPDM) rubber-based or polydimethylsiloxane (PDMS) silicone-based polymer composite.

[0062] Method for manufacturing an ethylene-propylene diene monomer (EPDM) rubber-based polymer composite

[0063] The method for manufacturing an ethylene-propylene diene monomer (EPDM) rubber-based polymer composite of the present invention is

[0064] A step of preparing exfoliated PMA-BNNNF (1-Pyrenemethyl methacrylate-boronnitride nanoflake) nanofillers by mixing and stirring hexagonal boron-nitride (h-BN) and 1-pyrenemethyl methacrylate (PMA) in a solvent (Step 1);

[0065] A step of preparing partially crosslinked PMA-BNNF / EPDM rubber by chemical reaction by adding and stirring dicumyl peroxide and the exfoliated PMA-BNNF nanofiller obtained in Step 1 to ethylene-propylene diene monomer (EPDM) rubber dissolved in a solvent (Step 2);

[0066] A step of drying the above-manufactured PMA-BNNF / EPDM rubber to remove the solvent (Step 3); and

[0067] It includes the step (step 4) of fully curing the solvent-removed PMA-BNNF / EPDM rubber to produce a PMA-BNNF / EPDM polymer composite.

[0068] Step 1 involves preparing exfoliated PMA-BNNNF nanofillers by mixing and stirring hexagonal boron nitride (h-BN) and 1-pyrenemethyl methacrylate (PMA) in a solvent. Step 1 is as shown in Reaction Scheme 1 below.

[0069] [Reaction Equation 1]

[0070]

[0071] Here, it is preferable to use N,N-dimethylformamide (DMF) as the solvent, and the weight ratio of PMA to h-BN is preferably 1:1.

[0072] Specifically, Step 1 can be performed as follows.

[0073] PMA and h-BN are mixed and stirred in a solvent, preferably DMF, in a 1:1 ratio, and ultrasonically treated at room temperature using an ultrasonic processor to synthesize exfoliated PMA-BNNF nanofillers. Subsequently, the solvent, preferably DMF, is filtered through membrane filter filtration, preferably using a vacuum filter, to extract only the synthesized PMA-BNNF nanofillers. The extracted PMA-BNNF nanofillers are dried under reduced pressure, preferably in a vacuum oven at 70 to 90°C for 1 to 3 hours, to evaporate the remaining DMF, and finally, the PMA-BNNF nanofillers are synthesized.

[0074] The nanofiller produced through this step 1 is characterized by having nanoparticles having both vinyl groups and pyrene groups that can increase the crosslinking density on the exfoliated h-BN surface, wherein the bonding of the pyrene groups to h-BN and the exfoliation of h-BN can occur simultaneously.

[0075] Step 2 involves adding dicumyl peroxide to ethylene-propylene diene monomer (EPDM) rubber dissolved in a solvent and adding and stirring the exfoliated PMA-BNNF nanofiller obtained in Step 1 to the EPDM rubber mixture obtained in Step 2 to produce partially cross-linked PMA-BNNF / EPDM rubber by chemical reaction.

[0076] Specifically, EPDM rubber is added to a solvent, preferably n-hexane, and stirred at 70 to 90°C, and dicumyl peroxide is added to the EPDM rubber dissolved in the solvent, preferably n-hexane, in a ratio of 8:1 to 12:1 (EPDM rubber:dicumyl peroxide), and stirred at 70 to 90°C to prepare an EPDM rubber mixture.

[0077] Step 2 is as shown in Reaction Scheme 2 below.

[0078] [Reaction Equation 2]

[0079]

[0080] Here, the exfoliated PMA-BNNF nanofiller can be added in a range of 0.3% to 0.6% by weight, preferably 0.5% by weight, based on 100% by weight of the polymer composite. In this case, the formed polymer composite has excellent mechanical properties (tensile strength, permanent compression set), chemical resistance (acidic and basic environments), and hydrogen permeability reduction performance.

[0081] When the above range is exceeded, particularly when 0.7 wt% or 0.9 wt% of exfoliated PMA-BNNF nanofillers are added, problems arise in which mechanical properties (tensile strength, permanent compression set) and hydrogen permeability reduction performance decrease due to the aggregation of nanofillers caused by van der Waals forces within the polymer composite matrix and excessive crosslinking density.

[0082] It is preferable that stirring be performed at a temperature of 70 to 90°C.

[0083] Step 3 involves drying the above-prepared PMA-BNNF / EPDM rubber to remove the solvent.

[0084] Specifically, drying is performed in a vacuum oven at 50 to 70°C under reduced pressure.

[0085] Step 4 involves fully curing the solvent-removed PMA-BNNF / EPDM rubber to produce a PMA-BNNF / EPDM polymer composite.

[0086] Curing is preferably performed in a hot press machine at a temperature of 130 to 150°C and a pressure of 1400 to 1600 bar, and through this curing, a PMA-BNNF / EPDM polymer composite can be manufactured.

[0087] Method for manufacturing a polydimethylsiloxane (PDMS) silicon-based polymer composite

[0088] In addition, the method for manufacturing a polydimethylsiloxane (PDMS) silicon-based polymer composite of the present invention

[0089] A step of preparing exfoliated PMA-BNNNF nanofillers by mixing and stirring hexagonal boron nitride (h-BN) and 1-pyrenemethyl methacrylate (PMA) in a solvent (Step 1);

[0090] A step of preparing partially cross-linked PMA-BNNF / PDMS silicone by chemical reaction by adding and stirring a polydimethylsiloxane (PDMS) silicone oligomer, a polydimethylsiloxane (PDMS) silicone curing agent, and the exfoliated PMA-BNNF nanofiller obtained in Step 1 in a solvent (Step 2);

[0091] A step of drying the above-prepared PMA-BNNF / PDMS silicone to remove the solvent (Step 3); and

[0092] The method includes the step (step 4) of preparing a PMA-BNNF / PDMS polymer composite by fully curing the solvent-removed PMA-BNNF / PDMS silicone.

[0093] Step 1 involves mixing and stirring hexagonal boron nitride (h-BN) and 1-pyrenemethyl methacrylate (PMA) in a solvent to prepare exfoliated PMA-BNNNF nanofillers. Since this step is identical to Step 1 described above, the description thereof is omitted here to avoid duplication.

[0094] Step 2 involves adding and stirring the polydimethylsiloxane (PDMS) silicone oligomer, the polydimethylsiloxane (PDMS) silicone curing agent, and the exfoliated PMA-BNNF nanofiller obtained in Step 1 in a solvent to produce partially cross-linked PMA-BNNF / PDMS silicone through a chemical reaction.

[0095] Specifically, PDMS silicon oligomer and the exfoliated PMA-BNNNF nanofiller obtained in step 1 are added to a solvent, preferably acetone, and stirred at 70 to 90°C, and PDMS silicon curing agent in a ratio of 8:1 to 12:1 (PDMS silicon oligomer:PDMS silicon curing agent) and the exfoliated PMA-BNNNF nanofiller obtained in step 1 are added to the PDMS silicon oligomer dissolved in a solvent, preferably acetone, and stirred at 70 to 90°C to produce partially cross-linked PMA-BNNF / PDMS silicon.

[0096] Step 2 is as shown in the following reaction scheme 3.

[0097] [Reaction Equation 3]

[0098]

[0099] Here, the exfoliated PMA-BNNF nanofiller can be added in a range of 0.3% to 0.6% by weight, preferably 0.5% by weight, based on 100% by weight of the polymer composite. In this case, the formed polymer composite has excellent mechanical properties (tensile strength, permanent compression set), chemical resistance (acidic and basic environments), and hydrogen permeability reduction performance.

[0100] When the above range is exceeded, particularly when 0.7 wt% or 0.9 wt% of exfoliated PMA-BNNF nanofillers are added, problems arise in which mechanical properties (tensile strength, permanent compression set) and hydrogen permeability reduction performance decrease due to the aggregation of nanofillers caused by van der Waals forces within the polymer composite matrix and excessive crosslinking density.

[0101] It is preferable that stirring be performed at a temperature of 70 to 90°C.

[0102] Step 3 involves drying the prepared PMA-BNNF / PDMS silicon to remove the solvent. This step is identical to Step 4 described above, and therefore, to avoid duplication, the description thereof is omitted here.

[0103] Step 4 involves curing the solvent-removed PMA-BNNF / PDMS silicone to prepare a PMA-BNNF / PDMS polymer composite. Since this step is identical to Step 4 described above, the description thereof is omitted here to avoid duplication.

[0104] The polymer composite produced by the manufacturing method of the present invention can obtain EPDM-based and silicone rubber-based polymer composites with increased crosslinking density and reduced gas permeability by using a nanofiller having a nanoparticle having both vinyl and pyrene groups attached to the surface of the nanofiller as a crosslinking agent to increase the crosslinking density.

[0105] A preferred embodiment of one aspect or another aspect of the present invention is characterized in that the PMA-BNNNF nanofiller exfoliated in step 3 is added in a range of 0.3% to 0.6% by weight based on 100% by weight of the polymer composite, and is stirred and crosslinked at a temperature of 70 to 90°C.

[0106] A preferred embodiment of one aspect or another aspect of the present invention is characterized in that, in step 4, drying is performed in a vacuum oven at 50 to 70°C.

[0107] A preferred embodiment of one aspect or another aspect of the present invention is characterized in that the curing of step 4 is performed in a hot press at a temperature of 130 to 150°C and a pressure of 1400 bar to 1600 bar.

[0108] The polymer composite containing PMA-BNNNF nanofillers prepared according to the present invention can increase the crosslinking density of the crosslinking agent and reduce gas permeability by using PMA-BNNNF nanofillers as a crosslinking agent. Specifically, it can exhibit excellent thermal properties and improved mechanical properties, as well as excellent permanent compression set, crosslinking density, hydrogen permeability, and acid resistance.

[0109] In addition, another aspect of the present invention provides a gasket for a fuel cell or water electrolysis stack comprising a polymer composite of the present invention.

[0110] A fuel cell can generally be composed of a membrane electrode assembly consisting of a polymer electrolyte membrane and electrodes, a gas diffusion layer that delivers the gas used in the reaction (i.e., reaction gas) to the electrodes and discharges reaction products, and a conductive separator that functions to supply reaction gas and cooling water from the outside and separate the anode and cathode. In addition, multiple manifolds are formed on the upper and lower portions of the membrane electrode assembly and the separator, respectively, to supply or discharge hydrogen and air required for the reaction, and cooling water to cool the reaction heat generated through the membrane electrode assembly and the separator. Accordingly, hydrogen, air, and cooling water can be supplied to the electrodes through gas channels formed in the separator of each unit cell, passing through the manifolds of the separator via the stack's external piping.

[0111] In addition, the fuel cell gasket is configured at each end of the separator to maintain airtightness for the unit cell, and also supports the maintenance of airtightness between stacked unit cells. The fuel cell gasket can be manufactured using the polymer composite of the present invention so that it is a thin sheet and possesses heat resistance, acid resistance, and airtightness.

[0112] Meanwhile, a gasket for an electrolytic cell generally comprises a rubber layer; an adhesive layer; a reinforcing layer; and a PTFE reinforcing film. Here, the rubber layer can be manufactured using the polymer composite of the present invention.

[0113] The details of the process of the present invention will be explained below through examples and experimental examples. These are representative examples related to the present invention, and it should be noted that the scope of application of the present invention cannot be limited solely by these examples.

[0114] <Example 1> Method for preparing a nanofiller (crosslinking agent) and a crosslinked polymer composite (PMA-BNNF / EPDM) of the present invention 1

[0115] Step 1:

[0116] 100 mg each of PMA (1-Pyrenemethyl methacrylate) and h-BN (hexagonal boronnitride) were mixed in 100 ml of DMF (N,N-dimethylformamide) in a 1:1 ratio.

[0117] Exfoliated PMA-BNNF (boronnitride nanoflake) nanofillers were synthesized by performing ultrasonic treatment at 20°C for a total of 24 hours under conditions of Amp 30%, pulse 5 seconds - rest 5 seconds using an ultrasonic processor.

[0118] DMF was filtered using a vacuum filter with a membrane filter (0.20 μm) to extract only the synthesized PMA-BNNF nanofiller.

[0119] The extracted PMA-BNNF nanofiller was dried in a vacuum oven at 80°C for 2 hours under reduced pressure to evaporate the remaining DMF, and finally, the PMA-BNNF nanofiller was synthesized.

[0120] The size distribution of the synthesized PMA-BNNF nanofiller is provided in Fig. 2.

[0121] The data indicated in Figure 2 is a size distribution graph, plotting the size of the synthesized PMA-BNNF nanofillers. Based on TEM images, a distribution graph was constructed by measuring the diameter of each PMA-BNNF nanofiller present in the measured TEM images. The differential distribution on the Y-axis represents the number of nanofillers, and the particle diameter on the X-axis represents the size of the nanofillers. When the average value of the distribution graph was calculated, the average size of the nanofillers was confirmed to be 25.2 nm.

[0122] Step 2:

[0123] 20 g of EPDM rubber was added to 100 ml of n-hexane and stirred at 80°C for 2 hours. 2 g of dicumyl peroxide and 22, 66, 110, 154, and 198 mg of PMA-BNNF nanofillers, respectively, were added to the EPDM rubber dissolved in n-hexane and stirred at 80°C for 2 hours.

[0124] Step 3:

[0125] The PMA-BNNF / EPDM rubber synthesized above was dried in a vacuum oven at 60°C for 2 hours under reduced pressure to evaporate n-hexane.

[0126] Step 4:

[0127] The PMA-BNNF / EPDM rubber synthesized above was cured in a hot press at 140°C and 1500 bar for 10 minutes to produce PMA-BNNF / EPDM polymer composites with weights of 0.1, 0.3, 0.5, 0.7, and 0.9 wt%, respectively.

[0128] Figure 3-① is a photograph showing the shape of the prepared PMA-BNNF / EPDM polymer composite, showing that the transparency of the specimen decreases as PMA-BNNF nanofillers are added.

[0129] As a comparative example, Neat EPDM was prepared under the same conditions except for the addition of a nanofiller (crosslinking agent) (Neat EPDM synthesis method).

[0130] Specifically, 20 g of EPDM rubber was added to 100 ml of n-hexane and stirred at 80°C for 2 hours. 2 g of dicumyl peroxide was added to the EPDM rubber dissolved in n-hexane and stirred at 80°C for 1 hour. The EPDM rubber synthesized above was dried in a vacuum oven at 60°C for 2 hours under reduced pressure to remove the n-hexane. The EPDM rubber synthesized above was cured in a hot press at 140°C and 1500 bar for 10 minutes to produce Neat EPDM.

[0131] <Example 2> Method for preparing nanofiller (crosslinking agent) and crosslinked polymer composite (PMA-BNNF / PDMS) 2

[0132] Step 1:

[0133] It was performed in the same manner as Step 1 of Example 1 above.

[0134] Step 2:

[0135] 10 g of PDMS silicon oligomer and 1 g of dicumyl peroxide were added to 100 ml of acetone, and 11, 33, 55, 77, and 99 mg of PMA-BNNF nanofillers, which had been sonicated in 10 ml of acetone using an ultrasonic processor at 20°C for a total of 10 minutes under conditions of Amp 20%, pulse 5 seconds, and resting period 5 seconds, were stirred at 80°C for 1 hour, and then crosslinked by carrying out a chemical reaction in an oil-based mixer at 2000 RPM for 10 minutes.

[0136] Step 3:

[0137] The PMA-BNNF / PDMS silicone synthesized above was placed in a vacuum oven at 40°C for 2 hours under reduced pressure to remove bubbles and acetone.

[0138] Step 4:

[0139] The PMA-NMMF / PDMS silicone dried above was cured in a hot press at 80°C and 1500 bar for 2 hours to produce PMA-BNNF / PDMS polymer composites of 0.1, 0.3, 0.5, 0.7, and 0.9 wt%, respectively.

[0140] Figure 3-② is a photograph showing the shape of the prepared PMA-BNNF / PDMS polymer composite, showing that the transparency of the specimen decreases as PMA-BNNF nanofillers are added.

[0141] For a comparative example, 10 g of DMS silicone oligomer and 1 g of PDMS silicone curing agent (10:1 ratio) were stirred at 20°C for 10 minutes.

[0142] The mixed PDMS silicone was de-aired in a vacuum oven at 20°C for 1 hour under reduced pressure.

[0143] Neat PDMS was prepared by curing the PDMS silicone, from which bubbles were removed in the previous process, in a hot press at 80°C and 1500 bar for 2 hours, and then drying it at 20°C for 8 hours.

[0144] <Experimental Example> Analysis method of nanofillers (crosslinking agents) and crosslinked polymer composites

[0145] Figure 4 is a graph of thermogravimetric analysis (TGA) measurements taken from room temperature (25℃) to 900℃ at a heating rate of 5℃ / min.

[0146] Figure 4-① shows the TGA measurement results for EPDM polymer composites. At 400°C, the temperature at which thermal decomposition is most active, the pure specimen showed 15% thermal decomposition, while the specimen with 0.5 wt% of PMA-BNNF nanofillers showed 10% thermal decomposition. This confirmed that the thermal stability (thermal decomposition resistance) of the specimen with 0.5 wt% of PMA-BNNF nanofillers was improved by 5%. Additionally, the EPDM polymer composite specimen with an excess amount (0.9 wt%) of PMA-BNNF nanofillers showed 14% thermal decomposition at 400°C. It is believed that the nanofillers, which were clustered at the EPDM polymer interface exposed by thermal decomposition, rapidly decomposed as they were exposed to the surface.

[0147] Figure 4-② shows the TGA measurement results for the PDMS polymer composite. At 600°C, the temperature at which thermal decomposition is most active, the pure specimen showed 37% thermal decomposition, while the specimen with 0.5 wt% of PMA-BNNF nanofiller added showed 20% thermal decomposition. Through this, it was confirmed that the thermal stability of the specimen with 0.5 wt% of PMA-BNNF nanofiller added was improved by 17%.

[0148] From the above results, it was confirmed that the thermal stability increased when an appropriate amount (0.5 wt%) of PMA-BNNF was added to the EPDM and PDMS polymer composite.

[0149] - Mechanical properties (experiment using UTM)

[0150] Mechanical property tests were performed using a universal testing machine (UTM) to prepare dogbone specimens of PMA-BNNF / EPDM and PMA-BNNF / PDMS polymer composites according to ASTM D 638 test standards (see Fig. 1), and then tensile strength tests were measured at 20°C and 50% relative humidity with a elongation speed of 50 mm / min and a load drop of 30%.

[0151] The results are provided in Fig. 5.

[0152] Figure 5 shows the results of measuring mechanical properties (tensile strength) as a stress-strain curve. The strain value on the X-axis represents the degree of deformation (elongation) when the specimen is pulled up and down, and the stress value on the Y-axis represents the maximum load that the specimen can withstand when pulled up and down.

[0153] Figure 5-① shows the stress-strain results of EPDM polymer composites. It can be seen that the maximum stress of the Neat specimen was 4 MPa, while the maximum stress of the specimen with 0.5 mass% of PMA-BNNF nanofiller added was 4.9 MPa, indicating an increase in maximum stress of approximately 22%. Additionally, it can be observed that the maximum stress decreased to 2.3 MPa in the specimen with an excess amount (0.9 mass%) of PMA-BNNF nanofiller added.

[0154] Figure 5-2 shows the stress-strain results of the PDMS polymer composite. It can be seen that the maximum stress of the Neat specimen was 5.1 MPa, and the maximum stress of the specimen with 0.5 mass% of PMA-BNNF nanofiller added was 8.2 MPa, indicating an increase of approximately 60% in maximum stress. Additionally, for specimens with an excess amount (0.7 mass% and 0.9 mass%) of PMA-BNNF nanofiller added, the maximum stress values ​​were 5.9 MPa and 5.7 MPa, respectively, which is lower compared to the optimized specimen.

[0155] Based on the above results, it was confirmed that the mechanical properties (tensile strength) of specimens with an appropriate amount (0.5 mass%) of PMA-BNNF nanofillers increased. This is because the PMA-BNNF nanofillers formed strong polymer chains with EPDM and PDMS polymers and formed a denser crosslinking density than the Neat specimens. On the other hand, it was confirmed that the mechanical properties decreased in specimens with an excess amount (0.7 mass% and 0.9 mass%) of PMA-BNNF nanofillers. It is believed that the mechanical properties deteriorated because the tensile stress was concentrated on the fillers that were not fully bonded due to aggregation at the interface of the EPDM and PDMS polymer matrix caused by the unevenly dispersed PMA-BNNF nanofillers.

[0156] Figure 6 is an SEM image of the fracture surface of the specimen after the mechanical property (tensile strength) test of Figure 5.

[0157] Figure 6-① shows the fracture surfaces of specimens after tensile strength testing of EPDM polymer composites, and (a) to (f) are SEM images of the fracture surfaces of specimens with PMA-BNNF nanofiller contents of Neat, 0.1 mass%, 0.3 mass%, 0.5 mass%, 0.7 mass%, and 0.9 mass%, respectively. Looking at the image in Figure 6-① (f), aggregation of PMA-BNNF nanofillers was found on the fracture surface, which confirms that tensile strength decreases when an excess amount (0.7 mass% or more) of PMA-BNNF nanofillers is added to the polymer composite.

[0158] Figure 6-2 shows the fracture surfaces of specimens after tensile strength testing of PDMS polymer composites, and (a) to (f) are SEM images of the fracture surfaces of specimens with PMA-BNNF nanofiller contents of Neat, 0.1 mass%, 0.3 mass%, 0.5 mass%, 0.7 mass%, and 0.9 mass%, respectively. Looking at images (e) and (f) in Figure 6-1, clumping of PMA-BNNF nanofillers was observed similar to the EPDM polymer composite mentioned earlier, and when compared with the tensile strength graph in Figure 5-2, it can be confirmed that the tensile strength decreased in specimens with 0.7 mass% and 0.9 mass% of PMA-BNNF nanofillers added.

[0159] - Measurement of permanent compression set

[0160] To measure the permanent compression set, 20 × 20 × 5 mm specimens of PMA-BNNF / EPDM and PMA-BNNF / PDMS polymer composites were prepared and measured using a Repeat Compression Tester in accordance with ASTM D 395 test standard. Under conditions of 50% relative humidity, a total of three repeated tests were conducted for 20 hours, with one cycle heating from the starting temperature of 20℃ to 80℃ at a heating rate of 0.3℃ / min. The permanent compression set was calculated according to the following Equation 1.

[0161] [Mathematical Formula 1]

[0162]

[0163] The results are provided in Fig. 7.

[0164] Figure 7 shows a graph of the results for the compression set. Each cycle refers to three repeated measurements taken from the starting temperature of 20°C to 80°C. The results for each cycle were measured at 80°C.

[0165] The graph in Figure 7-① shows the permanent compression set of the EPDM polymer composite. When the permanent compression set test was performed three times, the Neat specimen showed a permanent compression set of 94% based on an initial 100%, which was a decrease of 6%, whereas the specimen with 0.5 mass% of PMA-BNNF nanofiller added showed a permanent compression set of 97%, which was a decrease of about 3%.

[0166] The graph in Figure 7-② shows the permanent compression set of the PDMS polymer composite. When the permanent compression set test was performed three times in the same manner as above, the Neat specimen showed a permanent compression set of 99.05% relative to the initial 100%, a decrease of 0.95%, whereas the specimen with 0.5 mass% of PMA-BNNF nanofiller added did not show a permanent compression set of 100%, which was the same as the initial value. However, in the case of the specimen with an excess amount (0.9 mass%) of PMA-BNNF nanofiller added, the permanent compression set decreased by 0.07% to 99.03%.

[0167] Therefore, based on the above results, it can be seen that the mechanical properties (tensile strength, permanent compression set) of the polymer composite with added PMA-BNNF nanofillers are improved. This suggests that the PMA-BNNF nanofillers formed fine crosslinks and a strong crosslink density at the matrix interface of the polymer composite and enhanced the bonding strength of the polymer chains.

[0168] - Method for calculating crosslinking density

[0169] For the crosslinking density calculation experiment, 20 × 20 × 5 mm specimens of PMA-BNNF / EPDM and PMA-BNNF / PDMS polymer composites were prepared and immersed in a toluene solution at 20°C for 72 hours, and the initial volume value and the final volume value after 72 hours of each specimen were calculated using the Flory-Rehner equation (see Equation 2 below).

[0170] [Mathematical Formula 2]

[0171]

[0172] The results are provided in Fig. 8.

[0173] Figure 8-① is a graph of the cross-linking density of EPDM polymer composites, showing the cross-linking density according to the content of each PMA-BNNF nanofiller. It can be seen that the cross-linking density increases as the amount of PMA-BNNF nanofiller is added.

[0174] Figure 8-② is a graph of the crosslinking density of the PDMS polymer composite, showing the crosslinking density according to the content of each PMA-BNNF nanofiller. It can be seen that the crosslinking density increases as the amount of PMA-BNNF nanofiller is added.

[0175] The results of the crosslinking density measurement can be linked with the tensile strength results mentioned above, and it can be observed that the X-axis strain value in Fig. 5 decreases as the crosslinking density of the polymer composite increases. This indicates that the strain decreases as the crosslinking density of the polymer composite becomes denser.

[0176] - Hydrogen permeability measurement method

[0177] Hydrogen permeability was measured using a membrane permeability test station and gas chromatography (GC). PMA-BNNF / EPDM and PMA-BNNF / PDMS polymer composite specimens were prepared with a thickness of 870 μm and a diameter of 5 × 5 mm according to PEM stack cell specifications. The test conditions were measured at 80°C with a hydrogen gas flow rate of 1500 cc / min.

[0178] The results are provided in Fig. 9.

[0179] Figure 9 is a graph regarding hydrogen permeability. The test conditions were measured at 80°C, which is the same as the operating temperature of the fuel cell and water electrolysis cell.

[0180] The graph in Figure 9-① shows the hydrogen permeability of EPDM polymer composites. It was observed that the hydrogen permeability of the Neat specimen was 122 barrer, while that of the specimen with 0.5 mass% of PMA-BNNF nanofiller added was 63 barrer, indicating a 125% decrease in hydrogen permeability of the specimen with 0.5 mass% of PMA-BNNF nanofiller added. However, in the case of specimens with an excess amount (0.7 mass% and 0.9 mass%) of PMA-BNNF nanofiller added, it was observed that the hydrogen permeability increased compared to the optimized specimen with 0.5 mass%. This is believed to be due to the phenomenon of the excess PMA-BNNF nanofiller clumping within the EPDM polymer matrix, causing the hydrogen permeability to rise slightly again.

[0181] The graph in Figure 9-② shows the hydrogen permeability of the PDMS polymer composite. The Neat specimen was 1919 barrer, while the specimen with 0.5 mass% of PMA-BNNF nanofiller added was 1100 barrer. It was confirmed that the hydrogen permeability of the specimen with 0.5 mass% of PMA-BNNF nanofiller added decreased by 74%. Unlike EPDM polymer composites, it was confirmed that in the case of PDMS polymer composites, hydrogen permeability decreased even when an excess amount (0.7 mass% and 0.9 mass%) of PMA-BNNF nanofiller was added.

[0182] The hexagonal boron nitride (BN) containing PMA-BNNF synthesized by the inventors has the characteristic of reducing gas permeability when composited with a polymer.

[0183] - Method for evaluating chemical durability under acidic and basic conditions

[0184] ADT solution and KOH solution were used as methods to evaluate the chemical durability of PMA-BNNF / EPDM and PMA-BNNF / PDMS polymer composites.

[0185] The ADT solution used in the acid resistance test was prepared by mixing 10 ml of 1 M H2SO4 and 10 ml of 10 ppm HF in a 1:1 ratio. 20 ml of the ADT solution was placed in each vial, and PMA-BNNF / EPDM and PMA-BNNF / PDMS specimens were immersed at 80°C for 216 hours. The mass was measured every 12 hours to calculate the mass loss rate.

[0186] For the alkali resistance test, 20 ml of 1 M KOH solution was used to immerse PMA-BNNF / EPDM and PMA-BNNF / PDMS specimens in each vial at 80°C for 216 hours, and the mass was measured at 12-hour intervals to calculate the mass loss rate.

[0187] The results are provided in Figs. 10 and 11.

[0188] Figure 10 is data evaluating the chemical resistance (acid resistance) of polymer composites prepared according to the content of each PMA-BNNF nanofiller by measuring the weight loss of EPDM and PDMS polymer composites by exposing them to an ADT solution (acidic) prepared by the above-described method at 12-hour intervals for a total of 216 hours.

[0189] Figure 10-① shows the data evaluating the chemical resistance of specimens prepared according to the content of PMA-BNNF nanofillers in EPDM polymer composites to ADT solution. When the Neat specimen was exposed to ADT solution for 216 hours, a mass loss of 8.8% occurred, and it was confirmed that the optimized specimen with 0.5 mass% of PMA-BNNF nanofillers added showed a mass loss of 6.6%.

[0190] Figure 10-2 shows the data evaluating the chemical resistance of specimens prepared according to the content of PMA-BNNF nanofillers in PDMS polymer composites to ADT solution. When the Neat specimen was exposed to ADT solution for 216 hours, a mass loss of 1.1% occurred, and it was confirmed that the optimized specimen with 0.5 mass% of PMA-BNNF nanofillers added showed a mass loss of 0.2%.

[0191] Figure 11 is data evaluating the corrosion resistance (alkaline resistance) of polymer composites prepared according to the content of each PMA-BNNF nanofiller by measuring the mass loss rate after exposing EPDM and PDMS polymer composites to a KOH solution (alkaline) prepared by the above-described method at 12-hour intervals for a total of 216 hours.

[0192] Figure 11-① shows the data evaluating the corrosion resistance of specimens prepared according to the content of PMA-BNNF nanofillers in EPDM polymer composites to KOH solution. When the Neat specimen was exposed to KOH solution for 216 hours, a mass loss of 10% occurred, and it was confirmed that the optimized specimen with 0.5 mass% of PMA-BNNF nanofillers added experienced a mass loss of 3.5%.

[0193] Figure 11-② shows the data evaluating the corrosion resistance of specimens prepared according to the content of PMA-BNNF nanofillers in PDMS polymer composites to KOH solution. When the Neat specimen was exposed to KOH solution for 216 hours, a mass loss of 3.1% occurred, and it was confirmed that the optimized specimen with 0.5 mass% of PMA-BNNF nanofillers added experienced a mass loss of 2.1%. In addition, a mass loss of 4.6% occurred in the specimen with an excess amount (0.9 mass%) of PMA-BNNF nanofillers added. It is believed that the excess PMA-BNNF nanofillers were not evenly dispersed within the matrix of the polymer composite, and the nanofillers clumped together at the interface detached from the exposed surface as the polymer corroded, resulting in a rapid mass loss.

[0194] Based on the chemical resistance and corrosion resistance evaluation results in Figures 10 and 11 above, it was found that chemical resistance and corrosion resistance can be improved by compounding an appropriate amount (0.5 mass%) of PMA-BNNF with EPDM and PDMS polymers.

Claims

1. A method for manufacturing a polymer composite for a gasket of a fuel cell or water electrolysis stack, wherein A step of preparing exfoliated PMA-BNNNF (1-Pyrenemethyl methacrylate-boronnitride nanoflake) nanofillers by mixing and stirring hexagonal boron-nitride (h-BN) and 1-pyrenemethyl methacrylate (PMA) in a solvent (Step 1); A step of preparing partially crosslinked PMA-BNNF / EPDM by chemical reaction by adding and stirring dicumyl peroxide and the exfoliated PMA-BNNF nanofiller obtained in Step 1 to ethylene-propylene diene monomer (EPDM) rubber dissolved in a solvent (Step 2); A step of drying the above-manufactured PMA-BNNF / EPDM rubber to remove the solvent (Step 3); and A method comprising the step (step 4) of fully curing solvent-removed PMA-BNNF / EPDM rubber to produce a PMA-BNNF / EPDM polymer composite.

2. A method for manufacturing a polymer composite for a gasket of a fuel cell or water electrolysis stack, wherein A step of preparing exfoliated PMA-BNNNF nanofillers by mixing and stirring hexagonal boron nitride (h-BN) and 1-pyrenemethyl methacrylate (PMA) in a solvent (Step 1); A step of preparing partially cross-linked PMA-BNNF / PDMS silicone by chemical reaction by adding and stirring a polydimethylsiloxane (PDMS) silicone oligomer, a polydimethylsiloxane (PDMS) silicone curing agent, and the exfoliated PMA-BNNF nanofiller obtained in Step 1 in a solvent (Step 2); A step of drying the above-prepared PMA-BNNF / PDMS silicone to remove the solvent (Step 3); and A method comprising the step (step 4) of preparing a PMA-BNNF / PDMS polymer composite by fully curing the solvent-removed PMA-BNNF / PDMS silicone.

3. A method according to claim 1 or 2, characterized in that in step 1, the solvent is N,N-dimethylformamide (DMF) and the weight ratio of PMA to h-BN is 1:

1.

4. In claim 1 or 2, after mixing and stirring in step 1, Ultrasonic treatment is performed using an ultrasonic processor, and PMA-BNNF nanofillers are extracted by filtering the solvent through membrane filter filtration, and A method characterized by preparing exfoliated PMA-BNNF nanofillers by evaporating the residual solvent through vacuum drying of the extracted PMA-BNNF nanofillers.

5. A method according to claim 1, characterized in that in step 2, the solvent is n-hexane, and the addition, stirring, and crosslinking reaction is carried out at a temperature of 70 to 90°C.

6. A method according to claim 2, characterized in that in step 2, the solvent is acetone, is added at a temperature of 70 to 90°C, and is stirred and crosslinked at a temperature of 70 to 90°C.

7. A method according to claim 1 or 2, characterized in that the exfoliated PMA-BNNNF nanofiller is added in a range of 0.3% to 0.6% by weight based on 100% by weight of the polymer composite, and the reaction is stirred and crosslinked at a temperature of 70 to 90°C.

8. A method according to claim 1 or 2, characterized in that the drying is performed in a vacuum oven at 50 to 70°C.

9. A method according to claim 1 or 2, characterized in that the curing is performed in a hot press at a temperature of 130 to 150°C and a pressure of 1400 to 1600 bar.

10. A gasket for a fuel cell or water electrolysis stack comprising the polymer composite of claim 1 or 2.

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