Flame-retardant sealing material for fuel cell and preparation method of flame-retardant sealing material

Abstract

The invention discloses a flame-retardant sealing material for a fuel cell and a preparation method of the flame-retardant sealing material, the process is simple, non-toxic and safe to use, and through an innovative raw material combination and preparation process, inorganic nano powder / long carbon chain coupling agent modified slurry is creatively used as a raw material, so that the flame-retardant sealing material is prepared. According to the flame-retardant sealing material for the fuel cell, the dispersity and the stability of the inorganic nano-powder in the flame-retardant sealing material for the fuel cell are improved, the compatibility of the inorganic nano-powder and other components is improved, a synergistic effect is generated, and active groups on the surface of the modified nano-powder chemically react with monomers in the sealing material in the curing process to form chemical bonds, so that the sealing performance of the sealing material is improved. And the impact strength, the hardness, the water resistance, the corrosion resistance and the flame retardance of the flame-retardant sealing material for the fuel cell after being completely cured are effectively improved.

Description

Technical Field

[0001] The present invention relates to a new material and a preparation method thereof, in particular to a flame-retardant sealing material for fuel cells and a preparation method thereof; and belongs to the technical field of functional materials. Background Art

[0002] Fuel cells are a new type of power system. As a device that directly converts the chemical energy of fuel (such as hydrogen) and oxidant (such as oxygen) into electrical energy, compared with existing fuel engines (gasoline and diesel engines), their energy conversion is not restricted by the Carnot cycle and the only additional product is water. They have significant advantages such as high energy conversion efficiency and environmental friendliness, making them a clean and environmentally friendly energy source that has attracted much attention.

[0003] In fuel cell systems, sealants play a crucial role, and their performance directly affects the overall performance, safety, and service life of the fuel cell. Fuel cells generate electricity through the chemical reaction of hydrogen and oxygen. This process requires that the stack must maintain a high degree of airtightness and stability. As the core material to ensure the isolation of gas and liquid inside the fuel cell and prevent leakage, sealants must meet many stringent performance requirements: (1) High airtightness: to seal hydrogen and oxygen; (2) Low moisture permeability: to allow the polymer membrane to work under saturated water vapor conditions and maintain the acidity inside the battery; (3) Acid resistance: when the battery generates electricity, it is usually in a low pH environment; (4) Moisture resistance: because the polymer membrane is in a saturated water vapor state inside the battery when it is working; (5) Heat resistance: determined by the working environment of the fuel cell; (6) Insulation: to prevent short circuits between cells; (7) Others: resistance to coolant media, and also resistance to methanol media when used in methanol reforming or methanol fuel cells.

[0004] Patent application number 202310359533.8 discloses a UV-curable sealant for fuel cell bipolar plates and its preparation method. The sealant uses methacrylate-terminated polyisobutylene as the main resin, along with highly reactive acrylate oligomers, hard acrylate monomers, soft acrylate monomers, a photoinitiator, an inhibitor, a thixotropic agent, and other raw materials. However, UV curing has limited application due to its difficulty in sealing opaque parts.

[0005] The invention patent with application number 202210769713.9 discloses a high-temperature sealant for a fuel cell humidifier. The sealant is prepared using raw materials such as end-alkoxy polydimethylsiloxane, vinyltrimethoxysilane, filler, adhesion promoter and cross-linking agent, but has the problem of insufficient cohesive strength.

[0006] In view of this, the existing fuel cell sealant technology still faces many challenges in meeting the complex working environment requirements of fuel cells, matching future industrial production processes, and achieving domestic substitution. It is urgently needed to solve these challenges through technological innovation and process improvement to promote the healthy and rapid development of the fuel cell industry. Summary of the Invention

[0007] In order to address the shortcomings of the existing technology, and to address the problems of complex production process, low strength, and poor flame retardancy of existing fuel cell sealing materials, the present invention provides a flame-retardant sealing material for fuel cells and a preparation method thereof. Through raw material optimization and process improvement, the flame retardant properties, mechanical properties, and water and corrosion resistance of the sealing material are synergistically enhanced.

[0008] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0009] The present invention first discloses a method for preparing a flame-retardant sealing material for a fuel cell, comprising the following steps:

[0010] (1) Preparation of aliphatic polyurethane acrylate oligomers to provide a flexible skeleton and reactive sites;

[0011] 100 parts by mass of an aliphatic dibasic acid and 70-90 parts by mass of an aliphatic diol are mixed and heated to 150-200° C. for esterification for 2-3 hours, then heated to 210-230° C., vacuum polycondensed for 3-5 hours, cooled to obtain a polyester diol with a molecular weight of 1500-2500, heated to 70-90° C., and an aliphatic diisocyanate is added to cap the polyester diol for 2-4 hours, and then a hydroxyl-containing acrylate is added in an amount equal to the aliphatic diisocyanate and the like, and reacted for 1-3 hours to obtain an aliphatic polyurethane acrylate oligomer;

[0012] (2) Preparation of acrylic acid mixture

[0013] 100 parts by mass of a monofunctional long carbon chain acrylate monomer, 40-90 parts by mass of a multifunctional long carbon chain acrylate monomer, 0.5-2 parts by mass of an initiator, 0.05-0.2 parts by mass of a polymerization inhibitor, and 0.1-0.3 parts by mass of a stabilizer were added to a dispersion kettle, respectively, and stirred and dispersed for 0.5-1.5 hours to obtain an acrylate mixed solution;

[0014] (3) Preparation of inorganic nanopowder / long carbon chain coupling agent modified slurry

[0015] In a four-necked flask equipped with a stirring device, a thermometer, and a condenser, 10 parts by mass of an inorganic nanopowder, 50 parts by mass of a mixed solution of methanol and 0.5-1.5 parts by mass of a long carbon chain coupling agent were added, and the mixture was heated to 50-70°C and refluxed for 12-24 hours. After cooling to room temperature, the product was transferred to a rotary evaporator, and the methanol was removed by heating and distillation. Then, 10-20 parts by mass of the above-mentioned acrylate mixture was added, and ultrasonic dispersion was performed for 1-3 hours to obtain an inorganic nanopowder / long carbon chain coupling agent modified slurry.

[0016] (4) Preparation of flame-retardant sealing materials for fuel cells

[0017] Add 100 parts by mass of the above-mentioned aliphatic polyurethane acrylate oligomer, 10-20 parts by mass of the above-mentioned acrylate mixed liquid, 10-20 parts by mass of the above-mentioned inorganic nanopowder / long carbon chain coupling agent modified slurry, and 10-20 parts by mass of liquid flame retardant into a dispersion kettle, mix them thoroughly, and obtain a flame-retardant sealing material for fuel cells.

[0018] Preferably, the aforementioned aliphatic dibasic acid is one of succinic acid, adipic acid, and sebacic acid, and the aforementioned aliphatic diol is one of diethylene glycol, butanediol, and hexanediol.

[0019] Preferably, the aliphatic diisocyanate is one of hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane-4,4'-diisocyanate.

[0020] Preferably, the hydroxyl-containing acrylate is one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate and hydroxypropyl methacrylate.

[0021] More preferably, the aforementioned monofunctional long carbon chain acrylate monomer is one of dodecyl acrylate, dodecyl methacrylate, tridecyl acrylate, tridecyl methacrylate, hexadecyl acrylate, and hexadecyl methacrylate, and the toughness of the cured sealing material is improved by introducing a flexible long carbon chain.

[0022] More preferably, the aforementioned multifunctional long carbon chain acrylate monomer is one of dodecanediol diacrylate, dodecanediol dimethacrylate, tridecanediol diacrylate, tridecanediol dimethacrylate, hexadecanediol diacrylate, and hexadecanediol dimethacrylate, and the crosslinking density of the cured sealing material is increased by introducing a multifunctional long carbon chain acrylate monomer.

[0023] Further preferably, the aforementioned inorganic nanopowder is one of titanium dioxide nanopowder, silicon dioxide nanopowder, kaolin nanopowder, and calcium carbonate nanopowder, so as to enhance the dispersibility and interface bonding ability.

[0024] Further preferably, the liquid flame retardant is a phosphorus-containing liquid flame retardant, preferably dimethyl methylphosphonate; and the initiator is an azo initiator, preferably azobisisobutyronitrile.

[0025] Still more preferably, the aforementioned long carbon chain coupling agent is one of hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane and octadecyltriethoxysilane.

[0026] More preferably, the polymerization inhibitor is one of hydroquinone, p-benzoquinone, methylhydroquinone, p-hydroxyanisole, 2-tert-butylhydroquinone, and 2,5-di-tert-butylhydroquinone.

[0027] More preferably, the aforementioned stabilizer is one of 4-benzoyl-2,2,6,6-tetramethylpiperidine, sebacate (2,2,6,6-tetramethylpiperidinyl), tris(1,2,2,6,6-pentamethylpiperidinyl)phosphite, 3,5-di-tert-butyl-4-hydroxybenzyl monoethyl phosphate nickel, 2,2-thiobis(4-tert-octylphenol)nickel-n-butylamine, dibutyldithiocarbamate nickel, salicylate, and benzotriazole.

[0028] The present invention also discloses a flame retardant sealing material for a fuel cell prepared by the above method.

[0029] The present invention is beneficial in that:

[0030] (1) The preparation process of the flame-retardant sealing material for fuel cells of the present invention is simple and easy to implement. It does not use solvents or conventional fluorine elements and has the advantages of being non-toxic, safe to use, and not polluting the environment. Conventional gluing methods such as dispensing, scraping, sprinkling, anilox roller gluing, and roller gluing can be used. The construction is convenient and the thermal curing method is used. Changes in thickness, color, humidity, and other factors will not affect the curing effect.

[0031] (2) The present invention, through innovative raw materials, preparation, modification and dispersion processes, creatively uses inorganic nanopowder / long carbon chain coupling agent modified slurry as raw material, thereby improving the dispersibility and stability of inorganic nanopowder in flame-retardant sealing materials for fuel cells, thereby improving the compatibility of inorganic nanopowder with other components, producing a synergistic effect, and the active groups on the surface of the modified nanopowder react chemically with the monomers in the sealing material during the curing process to form chemical bonds, thereby in-situ strengthening the cured product. The resulting sealing material has an oxygen index of ≥28.9%, an impact strength of ≥4.3 kJ / ㎡, a Shore hardness of 77-79, a mass loss rate of ≤1.5% in 40% NaOH solution, a water absorption rate of ≤5.9%, and an expansion rate of ≤0.8%. It can be seen that the preparation method of the present invention effectively improves the comprehensive performance of flame-retardant sealing materials for fuel cells after complete curing, and the impact strength, hardness, water resistance, corrosion resistance and flame retardancy are all significantly improved. DETAILED DESCRIPTION

[0032] The present invention is described in detail below with reference to specific examples. Unless otherwise specified, all raw materials used in the present invention are commercially available.

[0033] Example 1

[0034] The method for preparing the flame-retardant sealing material for fuel cells of this embodiment includes the following steps:

[0035] (1) Preparation of aliphatic polyurethane acrylate oligomers:

[0036] 100 parts by mass of adipic acid and 81 parts by mass of diethylene glycol were mixed and heated to 150° C. for esterification for 3 hours. The temperature was further raised to 210° C. and vacuum polycondensed for 5 hours. The mixture was cooled to obtain a polyester diol with a molecular weight of 2000. The mixture was heated to 70° C. and 16.8 parts by mass of hexamethylene diisocyanate were added to cap the polyester diol for 4 hours. 11.6 parts by mass of hydroxyethyl acrylate were then added and reacted for 3 hours to obtain an aliphatic polyurethane acrylate oligomer.

[0037] (2) Preparation of acrylic acid ester mixture:

[0038] 100 parts by mass of dodecyl acrylate, 40 parts by mass of hexadecyl glycol dimethacrylate, 0.5 parts by mass of azobisisobutyronitrile, 0.05 parts by mass of hydroquinone, and 0.1 parts by mass of 4-benzoyl-2,2,6,6-tetramethylpiperidine were added to a dispersion kettle respectively, and stirred and dispersed for 0.5 hours to obtain an acrylate mixed solution.

[0039] (3) Preparation of inorganic nanopowder / long carbon chain coupling agent modified slurry:

[0040] In a four-necked flask equipped with a stirrer, thermometer, and condenser, add 10 parts by weight of calcium carbonate nanopowder, a mixed solution of 50 parts by weight of methanol, and 0.5 parts by weight of hexadecyltrimethoxysilane. Heat to 50°C and reflux for 24 hours. After cooling to room temperature, transfer the product to a rotary evaporator and remove the methanol by heating and distillation. Then, add 20 parts by weight of the aforementioned acrylate mixture and ultrasonically disperse for 1 hour to produce an inorganic nanopowder / long carbon chain coupling agent modified slurry.

[0041] (4) Preparation of flame-retardant sealing materials for fuel cells:

[0042] Add 100 parts by mass of the above-mentioned aliphatic polyurethane acrylate oligomer, 10 parts by mass of the above-mentioned acrylate mixed liquid, 20 parts by mass of the above-mentioned inorganic nanopowder / long carbon chain coupling agent modified slurry, and 20 parts by mass of dimethyl methylphosphonate into a dispersion kettle and mix them thoroughly to obtain a flame-retardant sealing material for fuel cells.

[0043] Example 2

[0044] The method for preparing the flame-retardant sealing material for fuel cells of this embodiment includes the following steps:

[0045] (1) Preparation of aliphatic polyurethane acrylate oligomers:

[0046] 100 parts by mass of succinic acid and 90 parts by mass of hexanediol were mixed and heated to 180° C. for esterification for 2.5 hours. The temperature was further raised to 220° C. and vacuum polycondensed for 4 hours. The mixture was cooled to obtain a polyester diol with a molecular weight of 1500. The temperature was raised to 80° C. and 22.2 parts by mass of isophorone diisocyanate were added to cap the polyester diol for 3 hours. 13 parts by mass of hydroxyethyl methacrylate was then added and reacted for 2 hours to obtain an aliphatic polyurethane acrylate oligomer.

[0047] (2) Preparation of acrylic acid ester mixture:

[0048] 100 parts by mass of tridecyl methacrylate, 70 parts by mass of tridecanediol diacrylate, 1 part by mass of azobisisobutyronitrile, 0.1 part by mass of p-hydroxyanisole, and 0.2 part by mass of tris(1,2,2,6,6-pentamethylpiperidinyl)phosphite were added to a dispersion kettle respectively, and stirred and dispersed for 1 hour to obtain an acrylate mixed solution.

[0049] (3) Preparation of inorganic nanopowder / long carbon chain coupling agent modified slurry:

[0050] In a four-necked flask equipped with a stirrer, thermometer, and condenser, add 10 parts by weight of titanium dioxide nanopowder, a mixed solution of 50 parts by weight of methanol, and 1 part by weight of octadecyltrimethoxysilane. Heat to 60°C and reflux for 18 hours. After cooling to room temperature, transfer the product to a rotary evaporator and remove the methanol by heating and distillation. Then, add 15 parts by weight of the aforementioned acrylate mixture and ultrasonically disperse for 2 hours to prepare an inorganic nanopowder / long carbon chain coupling agent modified slurry.

[0051] (4) Preparation of flame-retardant sealing materials for fuel cells:

[0052] Add 100 parts by mass of the above-mentioned aliphatic polyurethane acrylate oligomer, 20 parts by mass of the above-mentioned acrylate mixed liquid, 10 parts by mass of the above-mentioned inorganic nanopowder / long carbon chain coupling agent modified slurry, and 20 parts by mass of dimethyl methylphosphonate into a dispersion kettle and mix them thoroughly to obtain a flame-retardant sealing material for fuel cells.

[0053] Example 3

[0054] The method for preparing the flame-retardant sealing material for fuel cells of this embodiment includes the following steps:

[0055] (1) Preparation of aliphatic polyurethane acrylate oligomers:

[0056] 100 parts by mass of sebacic acid and 70 parts by mass of butanediol were mixed and heated to 200° C. for esterification for 2 hours. The temperature was further raised to 230° C. and vacuum polycondensed for 3 hours. The mixture was cooled to obtain a polyester diol with a molecular weight of 2500. The mixture was heated to 90° C. and 26.2 parts by mass of dicyclohexylmethane-4,4'-diisocyanate was added to cap the polyester diol for 2 hours. 14.4 parts by mass of hydroxypropyl methacrylate was then added and reacted for 1 hour to obtain an aliphatic polyurethane acrylate oligomer.

[0057] (2) Preparation of acrylic acid ester mixture:

[0058] 100 parts by mass of hexadecyl methacrylate, 90 parts by mass of dodecanediol dimethacrylate, 2 parts by mass of azobisisobutyronitrile, 0.2 parts by mass of 2,5-di-tert-butylhydroquinone, and 0.3 parts by mass of 2,2-thiobis(4-tert-octylphenol)nickel-n-butylamine were added to a dispersion kettle respectively, and stirred and dispersed for 1.5 hours to obtain an acrylate mixed solution.

[0059] (3) Preparation of inorganic nanopowder / long carbon chain coupling agent modified slurry:

[0060] In a four-necked flask equipped with a stirrer, thermometer, and condenser, add 10 parts by weight of silica nanopowder, a mixed solution of 50 parts by weight of methanol, and 1.5 parts by weight of octadecyltriethoxysilane. Heat to 70°C and reflux for 12 hours. After cooling to room temperature, transfer the product to a rotary evaporator and remove the methanol by heating and distillation. Add 10 parts by weight of the aforementioned acrylate mixture and ultrasonically disperse for 1-3 hours to produce an inorganic nanopowder / long carbon chain coupling agent modified slurry.

[0061] (4) Preparation of flame-retardant sealing materials for fuel cells:

[0062] Add 100 parts by mass of the above-mentioned aliphatic polyurethane acrylate oligomer, 20 parts by mass of the above-mentioned acrylate mixed liquid, 20 parts by mass of the above-mentioned inorganic nanopowder / long carbon chain coupling agent modified slurry, and 10 parts by mass of dimethyl methylphosphonate into a dispersion kettle and mix them thoroughly to obtain a flame-retardant sealing material for fuel cells.

[0063] Comparative Example 1

[0064] The preparation method of the flame-retardant sealing material for fuel cells of this comparative example comprises the following steps:

[0065] (1) Preparation of aliphatic polyurethane acrylate oligomers:

[0066] 100 parts by mass of adipic acid and 81 parts by mass of diethylene glycol were mixed and heated to 150° C. for esterification for 3 hours. The temperature was further raised to 210° C. and vacuum polycondensed for 5 hours. The mixture was cooled to obtain a polyester diol with a molecular weight of 2000. The mixture was heated to 70° C. and 16.8 parts by mass of hexamethylene diisocyanate were added to cap the polyester diol for 4 hours. 11.6 parts by mass of hydroxyethyl acrylate were then added and reacted for 3 hours to obtain an aliphatic polyurethane acrylate oligomer.

[0067] (2) Preparation of acrylic acid ester mixture:

[0068] 100 parts by mass of dodecyl acrylate, 40 parts by mass of hexadecyl glycol dimethacrylate, 0.5 parts by mass of azobisisobutyronitrile, 0.05 parts by mass of hydroquinone, and 0.1 parts by mass of 4-benzoyl-2,2,6,6-tetramethylpiperidine were added to a dispersion kettle respectively, and stirred and dispersed for 0.5 hours to obtain an acrylate mixed solution.

[0069] (3) Preparation of sealing materials for proton exchange fuel cells:

[0070] 100 parts by mass of the above-mentioned aliphatic polyurethane acrylate oligomer, 20 parts by mass of the above-mentioned acrylate mixed solution, 10 parts by mass of calcium carbonate nanopowder, and 20 parts by mass of dimethyl methylphosphonate were added to a dispersion kettle and mixed thoroughly to obtain a flame-retardant sealing material for fuel cells.

[0071] Comparative Example 2

[0072] The preparation method of the flame-retardant sealing material for fuel cells of this comparative example comprises the following steps:

[0073] (1) Preparation of aliphatic polyurethane acrylate oligomers:

[0074] 100 parts by mass of adipic acid and 81 parts by mass of aliphatic diol were mixed and heated to 150°C for esterification for 3 hours, then the temperature was further raised to 210°C and vacuum polycondensed for 5 hours. The mixture was cooled to obtain a polyester diol with a molecular weight of 2000. The mixture was heated to 70°C and 16.8 parts by mass of hexamethylene diisocyanate were added to cap the polyester diol for 4 hours. 11.6 parts by mass of hydroxyethyl acrylate were then added and reacted for 3 hours to obtain an aliphatic polyurethane acrylate oligomer.

[0075] (2) Preparation of acrylic acid ester mixture:

[0076] 100 parts by mass of butyl acrylate, 40 parts by mass of ethylene glycol dimethacrylate, 0.5 parts by mass of azobisisobutyronitrile, 0.05 parts by mass of hydroquinone, and 0.1 parts by mass of 4-benzoyl-2,2,6,6-tetramethylpiperidine were added to a dispersion kettle respectively, and stirred and dispersed for 0.5 hours to obtain an acrylate mixed solution.

[0077] (3) Preparation of sealing materials for proton exchange fuel cells:

[0078] 100 parts by mass of the above-mentioned aliphatic polyurethane acrylate oligomer, 10 parts by mass of the above-mentioned acrylate mixed solution, and 20 parts by mass of dimethyl methylphosphonate were added to a dispersion kettle and mixed thoroughly to obtain a flame-retardant sealing material for a fuel cell.

[0079] Performance testing

[0080] After the sealing materials of Examples 1-3 and Comparative Examples 1-2 were completely cured, the following performance tests were performed:

[0081] (1) Impact strength test: Use a cantilever beam impact tester to perform the impact strength test, and calculate the impact strength according to formula (1):

[0082]

[0083] (2) Hardness test: The hardness of the sample was measured using a Shore hardness tester.

[0084] (3) Water absorption rate: Before the experiment, weigh the mass M1 of the sample, immerse the sample in water for 48 hours, remove it, wipe the surface water of the sample with filter paper, weigh the mass M2 of the sample, and calculate the water absorption rate Y(W) according to formula (2):

[0085]

[0086] (4) Expansion rate: Before the experiment, use a vernier caliper to measure the length, width, and height of the sample (accurate to 0.02 mm) and calculate its volume V1. After immersing the sample in water for 48 hours, remove it and wipe off the droplets on the surface of the sample with filter paper. Then measure its length, width, and height again and calculate its volume V2. Calculate the expansion rate Y(B) according to formula 3:

[0087]

[0088] (5) Corrosion resistance: Before the experiment, weigh the sample M3 and immerse it in a 40% sodium hydroxide aqueous solution for 48 h. Then take it out and soak it in deionized water for 24 h. After washing, dry it in an oven to constant weight. Weigh its mass M4 and calculate the mass loss rate Y(C) according to formula (4):

[0089]

[0090] (6) Oxygen index: The oxygen index of the sample was tested in accordance with GB / T2406.2-2009 “Determination of combustion behavior of plastics by oxygen index method”. The sample size was 130 mm in length, 10 mm in width and 4 mm in thickness.

[0091] The results are shown in Table 1 below:

[0092]

[0093] Table 1 Sealing material performance test results

[0094] As can be seen from Table 1, compared with Comparative Examples 1-2, the impact strength, hardness, water resistance, corrosion resistance, and flame retardancy of the flame-retardant fuel cell sealing materials of Examples 1-3 were significantly improved. The applicants analyze that this is because the improved preparation, modification, and dispersion processes allow the nanopowder to be more evenly dispersed in the sealing material. In addition, the active groups on the surface of the modified nanopowder react chemically with the monomers in the sealing material during the curing process, forming chemical bonds and strengthening the cured product in situ, thereby improving the strength, water resistance, and corrosion resistance of the cured sealing material.

[0095] It should be noted that the addition of an inorganic nanopowder / long carbon chain coupling agent modified slurry in Example 1 further improves the dispersibility and stability of the inorganic nanopowder in the flame-retardant sealing material for fuel cells, thereby improving the compatibility of the inorganic nanopowder with other components, producing a synergistic effect, and effectively improving the impact strength, hardness, water resistance, corrosion resistance, and flame retardancy of the flame-retardant sealing material for fuel cells after complete curing. Comparative Example 1, relative to Example 1, adds the same amount of unmodified nanopowder and flame retardant, resulting in poor compatibility of the inorganic nanopowder with other components. Although it has certain flame retardant properties, the flame retardant effect is obviously not as good as that of Example 1. Comparative Example 2, relative to Example 1, does not use long carbon chain acrylates and does not add nanopowders, and the resulting sealing material has poor toughness and water resistance.

[0096] In summary, the present invention optimizes the raw material ratio and modification process to make the material have excellent flame retardant properties (oxygen index ≥ 28.9%), acid and alkali resistance (mass loss rate ≤ 1.5%) and mechanical properties (impact strength ≥ 4.3kJ / m 2 , hardness ≥77%), and the preparation process is simple, and no toxic solvent is released during the entire process. It is a non-toxic and pollution-free environmentally friendly sealing material, suitable for industrial production, and has broad industrial application prospects.

[0097] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solutions obtained by equivalent replacement or equivalent transformation fall within the scope of protection of the present invention.

Claims

1. A method for preparing a flame-retardant sealing material for a fuel cell, characterized in that: The steps include: (1) Preparation of aliphatic polyurethane acrylate oligomers 100 parts by mass of an aliphatic dibasic acid and 70-90 parts by mass of an aliphatic diol are mixed and heated to 150-200° C. for esterification for 2-3 hours, then heated to 210-230° C., vacuum-polymerized for 3-5 hours, and cooled to obtain a polyester diol with a molecular weight of 1500-2500. The polyester diol is heated to 70-90° C., and an aliphatic diisocyanate is added to cap the polyester diol for 2-4 hours. Then, a hydroxyl-containing acrylate is added in an amount equal to the aliphatic diisocyanate and reacted for 1-3 hours to obtain an aliphatic polyurethane acrylate oligomer. (2) Preparation of acrylic acid mixture 100 parts by mass of a monofunctional long carbon chain acrylate monomer, 40-90 parts by mass of a multifunctional long carbon chain acrylate monomer, 0.5-2 parts by mass of an initiator, 0.05-0.2 parts by mass of a polymerization inhibitor, and 0.1-0.3 parts by mass of a stabilizer were added to a dispersion kettle, respectively, and stirred and dispersed for 0.5-1.5 hours to obtain an acrylate mixed solution; (3) Preparation of inorganic nanopowder / long carbon chain coupling agent modified slurry In a four-necked flask equipped with a stirring device, a thermometer, and a condenser, 10 parts by mass of an inorganic nanopowder, 50 parts by mass of a mixed solution of methanol and 0.5-1.5 parts by mass of a long carbon chain coupling agent were added, and the mixture was heated to 50-70°C and refluxed for 12-24 hours. After cooling to room temperature, the product was transferred to a rotary evaporator, and the methanol was removed by heating and distillation. Then, 10-20 parts by mass of the above-mentioned acrylate mixture was added, and ultrasonic dispersion was performed for 1-3 hours to obtain an inorganic nanopowder / long carbon chain coupling agent modified slurry. (4) Preparation of flame-retardant sealing materials for fuel cells Add 100 parts by mass of the above-mentioned aliphatic polyurethane acrylate oligomer, 10-20 parts by mass of the above-mentioned acrylate mixed liquid, 10-20 parts by mass of the above-mentioned inorganic nanopowder / long carbon chain coupling agent modified slurry, and 10-20 parts by mass of liquid flame retardant into a dispersion kettle, mix them thoroughly, and obtain a flame-retardant sealing material for fuel cells.

2. The method for preparing a flame-retardant sealing material for a fuel cell according to claim 1, characterized in that: The aliphatic dibasic acid is one of succinic acid, adipic acid, and sebacic acid; the aliphatic diol is one of diethylene glycol, butanediol, and hexanediol.

3. The method for preparing a flame-retardant sealing material for a fuel cell according to claim 1, characterized in that: The aliphatic diisocyanate is one of hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, and dicyclohexylmethane-4,4'-diisocyanate.

4. The method for preparing a flame-retardant sealing material for a fuel cell according to claim 1, characterized in that: The hydroxyl-containing acrylate is one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate and hydroxypropyl methacrylate.

5. The method for preparing a flame-retardant sealing material for a fuel cell according to claim 1, characterized in that: The monofunctional long carbon chain acrylate monomer is one of dodecyl acrylate, dodecyl methacrylate, tridecyl acrylate, tridecyl methacrylate, hexadecyl acrylate, and hexadecyl methacrylate.

6. The method for preparing a flame-retardant sealing material for a fuel cell according to claim 1, characterized in that: The multifunctional long carbon chain acrylate monomer is one of dodecanediol diacrylate, dodecanediol dimethacrylate, tridecanediol diacrylate, tridecanediol dimethacrylate, hexadecanediol diacrylate, and hexadecanediol dimethacrylate.

7. The method for preparing a flame-retardant sealing material for a fuel cell according to claim 1, characterized in that: The inorganic nanopowder is one of titanium dioxide nanopowder, silicon dioxide nanopowder, kaolin nanopowder, and calcium carbonate nanopowder; the liquid flame retardant is a phosphorus-containing liquid flame retardant, preferably dimethyl methylphosphonate; the initiator is an azo initiator, preferably azobisisobutyronitrile.

8. The method for preparing a flame-retardant sealing material for a fuel cell according to claim 1, characterized in that: The long carbon chain coupling agent is one of hexadecyltrimethoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, and octadecyltriethoxysilane; the polymerization inhibitor is one of hydroquinone, p-benzoquinone, methylhydroquinone, p-hydroxyanisole, 2-tert-butylhydroquinone, and 2,5-di-tert-butylhydroquinone.

9. The method for preparing a flame-retardant sealing material for a fuel cell according to claim 1, characterized in that: The stabilizer is one of 4-benzoyl-2,2,6,6-tetramethylpiperidine, sebacate (2,2,6,6-tetramethylpiperidinyl), tris(1,2,2,6,6-pentamethylpiperidinyl)phosphite, 3,5-di-tert-butyl-4-hydroxybenzyl monoethyl phosphate nickel, 2,2-thiobis(4-tert-octylphenol)nickel-n-butylamine, dibutyldithiocarbamate nickel, salicylate, and benzotriazole.

10. The flame-retardant sealing material for fuel cells obtained by the preparation method according to any one of claims 1 to 9.

Images