Aramid composite foam material and its preparation method
By combining meta-aramid short-cut fibers, meta-aramid precipitates, thermally expanded microspheres, and water-based adhesives, the heat resistance and mechanical strength problems of aramid foam materials under extreme environments were solved, achieving efficient and uniform foam preparation and forming a structurally stable three-dimensional network structure.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TAYHO ADVANCED MATERIALS GRP CO LTD
- Filing Date
- 2026-02-27
- Publication Date
- 2026-05-26
AI Technical Summary
Existing aramid foam materials are difficult to meet the requirements for use in extreme environments in terms of heat resistance, flame retardancy and mechanical strength. Furthermore, traditional preparation methods have problems such as expensive equipment, complex processes, significant impact on material purity, and difficulty in controlling cell size and distribution.
A stable three-dimensional network structure is formed by combining meta-aramid short-cut fibers, meta-aramid precipitates, thermally expandable microspheres, water-based adhesives, and surfactants through uniform dispersion and gradient heating foaming methods, thereby enhancing interfacial bonding and overall material strength.
A aramid composite foam material with uniform structure, low density, high strength, and high temperature resistance and flame retardancy was prepared. It is suitable for high temperature environments and has excellent mechanical properties and self-extinguishing properties.
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Figure CN121736473B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to an aramid composite foam material and its preparation method, belonging to the field of polymer composite materials technology. Background Technology
[0002] Porous foam materials are widely used in high-end fields such as aerospace, transportation, and electronic information due to their heat insulation and sound absorption properties. However, traditional polymer foams (such as polyurethane and polystyrene) often fail to meet the requirements for use in extreme environments in terms of heat resistance, flame retardancy, and mechanical strength.
[0003] Aramid fibers possess high specific strength, high heat resistance, and excellent flame retardant properties, making them an ideal reinforcing material for preparing high-performance composite foams. Traditional aramid foams utilize chopped aramid fibers and precipitated aramid fibers, resulting in weak interfacial bonding and easily leading to uneven material structure and insufficient mechanical properties. However, using precipitated aramid products, which are nanoscale fibrillary aggregates, allows for deep entanglement and bonding of chopped fibers, forming a three-dimensional interlocking network. This results in composite foams with uniform structure, low density, high strength, and high temperature resistance and flame retardancy.
[0004] Aramid foams are primarily produced using physical or chemical foaming methods. While physical foaming is environmentally friendly, the equipment is expensive, the process is complex, and it has poor adaptability to molding high-melting-point, non-melting fibers like aramid, making it difficult to form stable and uniform cell structures. Chemical foaming agents, on the other hand, may produce byproducts during the decomposition and foaming process, affecting material purity. Furthermore, the foaming process is vigorous, making it difficult to precisely control cell size and distribution, which can lead to large variations in the material's mechanical properties. In addition, existing processes often result in poor dispersion and agglomeration of aramid fibers, affecting foam uniformity and final performance.
[0005] Patent application CN118562189A discloses a method for preparing aramid foam. The preparation steps include: 1) washing meta-aramid chopped fibers with a surfactant and then placing them in an oven until completely dried to obtain dried aramid chopped fibers; 2) loosening and filtering the aramid precipitated fibers and the dried aramid chopped fibers to obtain filtered aramid precipitated fibers and aramid chopped fibers; 3) placing the filtered aramid precipitated fibers and aramid chopped fibers into a foaming tank, adding a foaming agent, an aqueous adhesive, and water to obtain a fiber suspension, and foaming to obtain wet foam; 4) after stirring, allowing the wet foam to stand and filter water until no continuous water drips, and then drying to obtain reinforced aramid fiber composite foam. This method only obtains foam by adding a surfactant to agitate air and form bubbles. The foam obtained by this method has poor fluffiness, poor bonding between aramid precipitated fibers and aramid chopped fibers, and mechanical strength that is difficult to meet normal use requirements. Therefore, developing a preparation process for aramid composite foam with uniform structure, excellent performance, and environmental friendliness is of great significance. Summary of the Invention
[0006] To address the shortcomings of existing technologies, this invention provides an aramid composite foam material and its preparation method. The aramid composite foam material has uniform structure, low density, high strength, and temperature resistance and flame retardancy, and the preparation method is green and efficient.
[0007] The technical solution of this invention to solve the above-mentioned technical problems is as follows: An aramid composite foam material, wherein, by weight, the raw materials of the aramid composite foam material include: 0.5-1 parts of meta-aramid chopped fibers; 0.2-0.5 parts of meta-aramid precipitation products; 0.05-0.2 parts of thermally expandable microspheres; 2-10 parts of water-based adhesive; 0.5-1 parts of surfactant; and 15-50 parts of deionized water;
[0008] The preparation method of the meta-aramid precipitation product is as follows: after the polymerization reaction of m-phenylenediamine and isophthaloyl chloride in a polar solvent, a meta-formaldehyde solution is obtained. After the meta-formaldehyde solution is fully dispersed in water, the meta-aramid precipitation product is obtained by solid-liquid separation.
[0009] Furthermore, the length of the meta-aramid chopped fiber is 1-10 mm, and the mass ratio of the meta-aramid chopped fiber to the meta-aramid precipitation product is (1.5-4):1.
[0010] Furthermore, the initial foaming temperature of the thermally expanded microspheres is 80-130℃.
[0011] Furthermore, the water-based adhesive is at least one of water-based polyurethane, water-based epoxy adhesive, acrylic adhesive, and carboxymethyl cellulose.
[0012] Furthermore, the surfactant is at least one of sodium dodecyl sulfonate (SDS), hexadecyltrimethylammonium bromide (CTAB), sorbitan fatty acid ester, and dodecyl dimethyl betaine (BS-12).
[0013] Furthermore, in the preparation process of the meta-aramid precipitation product, the meta-solid content is 18-22% by mass and the viscosity is 200-400 Po;
[0014] When the meta-formula is dispersed in water, the volume ratio of the meta-formula to water is 1:(10-15).
[0015] Furthermore, the mass ratio of the meta-aramid short-cut fibers to the thermally expanded microspheres is (4.5-10):1.
[0016] This invention also discloses a method for preparing aramid composite foam material, wherein the preparation method is as follows:
[0017] S1. Add the meta-aramid short-cut fibers and the meta-aramid precipitation product to deionized water containing surfactant and mix thoroughly to obtain a uniform and stable slurry.
[0018] S2. Add water-based adhesive and thermally expanded microspheres to the slurry from step S1, stir gently, and mix evenly;
[0019] S3. After filtration and molding, the material is dried at low temperature to remove moisture. The temperature is then increased to allow the microspheres to expand and the water-based adhesive to cure simultaneously, resulting in an aramid composite foam material.
[0020] Furthermore, in step S1, high-speed stirring is used during mixing, with a stirring speed of 5000-8000 r / min.
[0021] In step S2, the stirring speed for gentle stirring is 2000-3000 r / min.
[0022] Furthermore, in step S3, the temperature for low-temperature drying is 60-70°C;
[0023] The foaming process is carried out using a gradient heating method: first, maintain the temperature at 80-110℃ for 5-15 minutes, and then maintain the temperature at 130-180℃ for 10-30 minutes.
[0024] The beneficial effects of this invention are:
[0025] This invention provides a uniform, low-density, high-strength, temperature-resistant, and flame-retardant aramid composite foam material and its green and efficient preparation method. The method involves mixing the precipitate obtained by dispersing meta-aramid dope in water with meta-aramid chopped fibers. The nanoscale precipitate effectively encapsulates and bridges the millimeter-sized chopped fibers, significantly enhancing the interfacial bonding and integrity of the fiber skeleton. Thermally expandable microspheres are introduced as a foaming agent, and an aqueous adhesive is used as a binder. After foaming, the foam has higher bulkiness, better supporting the aramid chopped fibers and the aramid precipitate skeleton. Combined with the adhesive, this further enhances the strength of the composite foam material. These three elements work synergistically to construct a low-density, high-strength, and uniformly structured stable porous network.
[0026] In the preparation method described in this invention, meta-aramid chopped fibers and meta-aramid precipitates form a stable slurry system in deionized water containing surfactants, ensuring uniform dispersion of the aramid chopped fibers and precipitates and avoiding agglomeration, thereby producing a composite material with a uniform foam structure and consistent pore distribution. The thermally expanding microspheres expand and foam during heating, significantly reducing the material density. Simultaneously, the aqueous adhesive firmly bonds the aramid chopped fibers and precipitate skeleton, forming a three-dimensional network structure, enhancing the material's mechanical strength (such as compressive strength and toughness), achieving a balance between low density and high strength. Meta-aramid itself possesses inherent high-temperature resistance and flame-retardant properties, enabling the composite foam material to maintain structural stability at high temperatures and exhibit self-extinguishing properties, making it suitable for high-temperature applications such as aerospace and electronic protection. The foaming effect of the thermally expanding microspheres increases the foam's fluffiness, better supporting the meta-aramid chopped fibers and meta-aramid precipitate skeleton. Combined with the adhesive bonding, this further enhances the overall strength and durability of the composite foam material. Attached Figure Description
[0027] Figure 1 This is a microscopic morphology image of the aramid precipitation product. Detailed Implementation
[0028] The specific embodiments of the present invention will be described in detail below. The present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed.
[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used is for describing particular embodiments only and is not intended to limit the invention.
[0030] An aramid composite foam material, by weight, comprises the following raw materials: 0.5-1 parts meta-aramid chopped fibers; 0.2-0.5 parts meta-aramid precipitate; 0.05-0.2 parts thermally expandable microspheres; 2-10 parts water-based adhesive; 0.5-1 parts surfactant; and 15-50 parts deionized water.
[0031] The preparation method of the meta-aramid precipitation product is as follows: after the polymerization reaction of m-phenylenediamine and isophthaloyl chloride in a polar solvent, a meta-formaldehyde solution is obtained. After the meta-formaldehyde solution is fully dispersed in water, the meta-aramid precipitation product is obtained by solid-liquid separation.
[0032] Specifically, the length of the meta-aramid chopped fiber is 1-10 mm, and the mass ratio of the meta-aramid chopped fiber to the meta-aramid precipitation product is (1.5-4):1.
[0033] Specifically, the thermally expandable microspheres are microcapsules of low-boiling-point hydrocarbon gases encapsulated in a thermoplastic polymer shell, and the initial foaming temperature of the thermally expandable microspheres is 80-130℃.
[0034] Specifically, the water-based adhesive is at least one of water-based polyurethane, water-based epoxy, acrylic adhesive, and carboxymethyl cellulose.
[0035] Specifically, the surfactant is at least one of sodium dodecyl sulfonate (SDS), hexadecyltrimethylammonium bromide (CTAB), sorbitan fatty acid ester, and dodecyl dimethyl betaine (BS-12).
[0036] Specifically, in the preparation of the meta-aramid precipitation product, N,N-dimethylacetamide is used as a polar solvent, and m-phenylenediamine and isophthaloyl chloride are used to prepare a meta-stock solution with a solid content of 18-22% and a viscosity of 200-400 Po (25°C). The meta-stock solution is slowly dispersed in water using high-speed stirring at a speed of 5000-6000 r / min for 20-30 min. After stirring, it is filtered to obtain the meta-aramid precipitation product.
[0037] When the meta-formula is dispersed in water, the volume ratio of the meta-formula to water is 1:(10-15).
[0038] The preparation of the meta-position stock solution by polymerization of m-phenylenediamine and isophthaloyl chloride can be carried out using conventional polymerization processes. In this embodiment of the invention, the molar ratio of m-phenylenediamine to isophthaloyl chloride is 1:1, and the polymerization reaction temperature is -10~5℃.
[0039] Specifically, the mass ratio of the meta-aramid short-cut fibers to the thermally expanded microspheres is (4.5-10):1.
[0040] This invention also discloses a method for preparing aramid composite foam material, wherein the preparation method is as follows:
[0041] S1. Add the meta-aramid short-cut fibers and the meta-aramid precipitation product to deionized water containing surfactant and mix thoroughly to obtain a uniform and stable slurry.
[0042] S2. Add water-based adhesive and thermal expansion microspheres to the slurry in step S1, stir gently to mix evenly, and avoid the thermal expansion microspheres from breaking.
[0043] S3. After filtration and molding, the material is dried at low temperature to remove moisture. The temperature is then increased to allow the microspheres to expand and the water-based adhesive to cure simultaneously, resulting in an aramid composite foam material.
[0044] Specifically, in step S1, high-speed stirring is used during mixing. The stirring speed of the high-speed stirring is 5000-8000 r / min, and the stirring time is 10-40 min.
[0045] In step S2, the stirring speed for gentle stirring is 2000-3000 r / min, and the stirring time is 20-30 min.
[0046] Specifically, in step S3, the temperature for low-temperature drying is 60-70℃;
[0047] The temperature-increasing foaming process adopts a gradient heating method: first, it is kept at 80-110℃ for 5-15 minutes to allow the thermal expansion microspheres to initially expand; then, it is kept at 130-180℃ for 10-30 minutes to achieve complete foaming and curing of the adhesive.
[0048] The raw materials involved in the embodiments of the present invention are as follows:
[0049] Thermally expandable microspheres: AkzoNobel's Expancel® 920DU40;
[0050] Waterborne polyurethane adhesive: WANNATE® WD-8210 from Wanhua Chemical;
[0051] Carboxymethyl cellulose adhesive: Zhongtai's T-2000;
[0052] Water-based epoxy adhesive: Alberdingk® D1665 from Opaldi;
[0053] Meta-aramid chopped fiber: Taihe New Materials 1.5D chopped fiber.
[0054] The above-mentioned raw materials do not constitute a limitation on the technical solution of this invention.
[0055] Example 1
[0056] The preparation of an aramid composite foam material is as follows:
[0057] Raw material ratio: by weight, 0.5 parts meta-aramid chopped fiber, 0.2 parts meta-aramid precipitate, 0.05 parts thermally expanded microspheres, 2 parts waterborne polyurethane adhesive, 0.5 parts sodium dodecyl sulfonate surfactant, and 15 parts deionized water.
[0058] The preparation method of the meta-aramid precipitation product is as follows: Using N,N-dimethylacetamide as a polar solvent, a meta-formaldehyde solution with a solid content of 20% and a viscosity of 300 Po (25℃) is prepared using m-phenylenediamine and isophthaloyl chloride. The meta-formaldehyde solution is slowly dispersed in water (volume ratio of meta-formaldehyde solution to water is 1:10) using high-speed stirring at a speed of 5000 r / min for 30 min. After stirring, it is filtered to obtain the meta-aramid precipitation product (microscopic morphology of the aramid precipitation product is shown in Figure 1). Figure 1 (As shown).
[0059] Preparation method:
[0060] S1. Add 0.5 parts of meta-aramid chopped fibers and 0.2 parts of meta-aramid precipitate to a solution containing 0.5 parts of sodium dodecyl sulfonate and 15 parts of deionized water. Stir at 5000 rpm for 20 minutes using a high-speed stirrer to form a uniform and stable slurry.
[0061] S2. Add 2 parts of water-based polyurethane adhesive and 0.05 parts of thermally expanded microspheres to the above slurry. Adjust the stirring speed to 3000 rpm and stir gently for 20 minutes to ensure uniform mixing and avoid rupture of the thermally expanded microspheres.
[0062] S3. Filter and shape the mixed material, then place it in a 70℃ oven to dry for 2 hours to remove moisture. Subsequently, raise the temperature to 90℃, hold for 10 minutes, then raise the temperature to 170℃ and heat treat for 30 minutes to finally form a structurally stable aramid composite foam material.
[0063] Example 2
[0064] The preparation of an aramid composite foam material is as follows:
[0065] Raw material ratio: by weight, 1 part meta-aramid chopped fiber, 0.5 parts meta-aramid precipitate, 0.2 parts thermally expanded microspheres, 10 parts carboxymethyl cellulose adhesive, 1 part cetyltrimethylammonium bromide surfactant, and 50 parts deionized water.
[0066] The preparation method of the meta-aramid precipitation product is as follows: Using N,N-dimethylacetamide as a polar solvent, a meta-formaldehyde solution with a solid content of 22% and a viscosity of 380 Po (25℃) is prepared using m-phenylenediamine and isophthaloyl chloride. The meta-formaldehyde solution is slowly dispersed in water (volume ratio of meta-formaldehyde solution to water is 1:15) using high-speed stirring at a speed of 6000 r / min for 30 min. After stirring, the solution is filtered to obtain the meta-aramid precipitation product.
[0067] Preparation method:
[0068] S1. Add 1 part of meta-aramid short-cut fiber and 0.5 parts of meta-aramid precipitation product to a solution containing 1 part of hexadecyltrimethylammonium bromide and 50 parts of deionized water, and stir at a high speed of 5000 rpm for 20 minutes.
[0069] S2. Add 10 parts of carboxymethyl cellulose adhesive and 0.2 parts of thermally expanded microspheres, and stir at 3000 rpm for 20 minutes.
[0070] S3. After filtration and molding, the material is first dried at 70℃ for 2 hours, then the temperature is raised to 100℃ and kept at that temperature for 10 minutes, and then heat-treated at 170℃ for 30 minutes to obtain aramid composite foam material.
[0071] Example 3
[0072] The preparation of an aramid composite foam material is as follows:
[0073] Raw material ratio: by weight, 0.8 parts of meta-aramid chopped fiber, 0.3 parts of meta-aramid precipitate, 0.1 parts of thermally expanded microspheres, 5 parts of waterborne polyurethane adhesive, 0.8 parts of dehydrated sorbitan fatty acid ester surfactant, and 30 parts of deionized water.
[0074] The preparation method of the meta-aramid precipitation product is as follows: Using N,N-dimethylacetamide as a polar solvent, a meta-formaldehyde solution with a solid content of 18% and a viscosity of 220 Po (25℃) is prepared using m-phenylenediamine and isophthaloyl chloride. The meta-formaldehyde solution is slowly dispersed in water (volume ratio of meta-formaldehyde solution to water is 1:10) using high-speed stirring at a speed of 5000 r / min for 30 min. After stirring, the solution is filtered to obtain the meta-aramid precipitation product.
[0075] Preparation method:
[0076] S1. Add 0.8 parts of meta-aramid chopped fibers and 0.3 parts of meta-aramid precipitate to a solution containing 0.8 parts of dehydrated sorbitan fatty acid ester and 15 parts of deionized water. Stir at 5000 rpm for 20 minutes using a high-speed stirrer to form a uniform and stable slurry.
[0077] S2. Add 5 parts of water-based polyurethane adhesive and 0.1 parts of thermally expanded microspheres to the above slurry. Adjust the stirring speed to 3000 rpm and stir gently for 20 minutes to ensure uniform mixing and avoid rupture of the thermally expanded microspheres.
[0078] S3. Filter and shape the mixed materials, then dry them in a 70°C oven for 2 hours to remove moisture. Subsequently, raise the temperature to 80°C, hold for 15 minutes, and then heat-treat at 170°C for 30 minutes to obtain the composite foam material.
[0079] Example 4
[0080] The preparation of an aramid composite foam material is as follows:
[0081] Raw material ratio: by weight, 0.7 parts meta-aramid chopped fiber, 0.4 parts meta-aramid precipitate, 0.15 parts thermally expanded microspheres, 6 parts water-based epoxy adhesive, 0.7 parts dodecyl dimethyl betaine (BS-12) surfactant, and 40 parts deionized water.
[0082] The preparation method of the meta-aramid precipitation product is as follows: Using N,N-dimethylacetamide as a polar solvent, a meta-formaldehyde solution with a solid content of 20% and a viscosity of 300 Po (25℃) is prepared using m-phenylenediamine and isophthaloyl chloride. The meta-formaldehyde solution is slowly dispersed in water (volume ratio of meta-formaldehyde solution to water is 1:10) using high-speed stirring at a speed of 5000 r / min for 30 min. After stirring, the solution is filtered to obtain the meta-aramid precipitation product.
[0083] Preparation method:
[0084] S1. Add 0.7 parts of meta-aramid chopped fibers and 0.4 parts of meta-aramid precipitate to a solution containing 0.7 parts of BS-12 and 40 parts of deionized water. Stir at 5000 rpm for 20 minutes using a high-speed stirrer to form a uniform and stable slurry.
[0085] S2. Add 6 parts of water-based epoxy adhesive and 0.15 parts of thermally expanded microspheres to the above slurry. Adjust the stirring speed to 3000 rpm and stir gently for 20 minutes to ensure uniform mixing and avoid breaking the thermally expanded microspheres.
[0086] S3. Filter and shape the mixed material, then place it in a 70℃ oven to dry for 1.5 hours to remove moisture. Subsequently, raise the temperature to 110℃, hold for 5 minutes, and then heat treat at 180℃ for 10 minutes to finally form a structurally stable aramid composite foam material.
[0087] Comparative Example 1
[0088] Aramid composite foam material was prepared using the same method as in Example 1, except that thermally expandable microspheres were not used in Comparative Example 1.
[0089] Raw material ratio: by weight, 0.5 parts meta-aramid chopped fiber, 0.2 parts meta-aramid precipitate, 2 parts waterborne polyurethane adhesive, 0.5 parts sodium dodecyl sulfonate surfactant, and 15 parts deionized water.
[0090] Preparation method: The preparation process is the same as in Example 1, but in step S2, thermally expanded microspheres are not added, only water-based adhesive is added and stirred and mixed. The subsequent filtration, drying and heat treatment steps remain unchanged.
[0091] Comparative Example 2
[0092] Aramid composite foam material was prepared using the same method as in Example 1, except that meta-aramid precipitate was not used in Comparative Example 2.
[0093] Raw material ratio: by weight, meta-aramid chopped fibers are 0.5 parts, thermally expanded microspheres are 0.05 parts, water-based polyurethane adhesive is 2 parts, sodium dodecyl sulfonate surfactant is 0.5 parts, and deionized water is 15 parts.
[0094] Preparation method: The preparation process is the same as in Example 1, but in step S1, meta-aramid precipitate is not added, and only the meta-aramid short-cut fibers are stirred and pulped with an aqueous surfactant solution.
[0095] Comparative Example 3
[0096] Aramid composite foam materials were prepared using the same method as in Example 1, except that N,N-dimethylacetamide was used instead of deionized water as the dispersion medium in Comparative Example 3.
[0097] Raw material ratio: by weight, 0.5 parts of meta-aramid chopped fiber, 0.2 parts of meta-aramid precipitate, 0.05 parts of thermally expanded microspheres, 2 parts of waterborne polyurethane adhesive, 0.5 parts of sodium dodecyl sulfonate surfactant, and 15 parts of N,N-dimethylacetamide.
[0098] Preparation method: The preparation steps are exactly the same as in Example 1, but N,N-dimethylacetamide is used instead of deionized water.
[0099] Comparative Example 4
[0100] Aramid composite foam material was prepared using the same method as in Example 1, except that no surfactant was added in Comparative Example 4.
[0101] Raw material ratio: by weight, 0.5 parts of meta-aramid chopped fiber, 0.2 parts of meta-aramid precipitate, 0.05 parts of thermally expanded microspheres, 2 parts of waterborne polyurethane adhesive, and 15 parts of deionized water.
[0102] Preparation method: The preparation process is the same as in Example 1, but in step S1, no surfactant is added. The fiber and precipitated product are directly added to deionized water and stirred. Subsequent steps remain unchanged.
[0103] Comparative Example 5
[0104] Aramid composite foam material was prepared using the same method as in Example 1, except that in Comparative Example 5, meta-aramid precipitated fibers were used instead of meta-aramid precipitated products.
[0105] Raw material ratio: by weight, 0.5 parts meta-aramid chopped fiber, 0.2 parts meta-aramid precipitated fiber (Taihe New Material NF711), 0.05 parts thermally expanded microspheres, 2 parts waterborne polyurethane adhesive, 0.5 parts sodium dodecyl sulfonate surfactant, and 15 parts deionized water.
[0106] Preparation method: The preparation steps are exactly the same as in Example 1, but meta-aramid precipitated fibers are used instead of meta-aramid precipitated products.
[0107] Comparative Example 6
[0108] Aramid composite foam material was prepared using the same method as in Example 1, except that: in Comparative Example 6, when preparing the meta-aramid precipitate, the volume ratio of the meta-form solution to water was 1:5 (the amount of water used was lower than the proportion specified in this invention).
[0109] Raw material ratio: by weight, 0.5 parts meta-aramid chopped fiber, 0.2 parts meta-aramid precipitate, 0.05 parts thermally expanded microspheres, 2 parts waterborne polyurethane adhesive, 0.5 parts sodium dodecyl sulfonate surfactant, and 15 parts deionized water.
[0110] The preparation method of the meta-aramid precipitation product is as follows: Using N,N-dimethylacetamide as a polar solvent, a meta-formaldehyde solution with a solid content of 20% and a viscosity of 300 Po (25℃) is prepared using m-phenylenediamine and isophthaloyl chloride. The meta-formaldehyde solution is slowly dispersed in water (volume ratio of meta-formaldehyde solution to water is 1:5) using high-speed stirring at a speed of 5000 r / min for 30 min. After stirring, the solution is filtered to obtain the meta-aramid precipitation product.
[0111] Preparation method: The preparation process is the same as in Example 1.
[0112] Comparative Example 7
[0113] Aramid composite foam material was prepared using the same method as in Example 2, except that the amount of meta-aramid chopped fiber was adjusted in Comparative Example 7 so that the mass ratio of meta-aramid chopped fiber to meta-aramid precipitate was 1:1 (not within the (1.5-4):1 ratio range limited by this invention).
[0114] Raw material ratio: by weight, 0.5 parts of meta-aramid chopped fiber, 0.5 parts of meta-aramid precipitate, 0.2 parts of thermally expanded microspheres, 10 parts of carboxymethyl cellulose adhesive, 1 part of cetyltrimethylammonium bromide surfactant, and 50 parts of deionized water.
[0115] Preparation method: The preparation process is the same as in Example 2.
[0116] Comparative Example 8
[0117] Aramid composite foam material was prepared using the same method as in Example 2, except that the amount of thermally expanded microspheres added was adjusted in Comparative Example 8 so that the mass ratio of meta-aramid short fibers to thermally expanded microspheres was 2.5:1 (not within the range of (4.5-10):1) limited by this invention.
[0118] Raw material ratio: by weight, 0.5 parts meta-aramid chopped fiber, 0.2 parts meta-aramid precipitate, 0.2 parts thermally expanded microspheres, 2 parts waterborne polyurethane adhesive, 0.5 parts sodium dodecyl sulfonate surfactant, and 15 parts deionized water.
[0119] Preparation method: The preparation process is the same as in Example 1.
[0120] The performance of the aramid composite foam materials obtained in Examples 1-4 and Comparative Examples 1-8 was tested, and the test results are shown in the table below. The test methods involved were: density according to ISO 845:2006, compressive strength according to ISO 844:2021, and limiting oxygen index according to GB / T 2406.2-2009.
[0121] Table 1 Performance test results of aramid composite foam materials
[0122]
[0123] As can be seen from the data in the table above, the aramid composite foam materials prepared by the method described in this invention in Examples 1-4 exhibit excellent properties. Their performance indicators, including density (≤0.15 g / cm³), compressive strength (≥1.2 MPa), and limiting oxygen index (LOI≥32%), clearly point to the design goals of "low density," "high strength," and "temperature resistance and flame retardancy." In particular, Example 2, under optimal component ratios, achieved the lowest density and the highest compressive strength, demonstrating the high adjustability and performance potential of the formulation of this invention.
[0124] A comparison of the results from Comparative Example 1 and Example 1 shows that without the addition of thermally expandable microspheres, the material cannot form a porous foam structure, resulting in a sharp increase in density to 0.35 g / cm³, while the compressive strength also drops to a minimum. This fully demonstrates that thermally expandable microspheres, through their thermal expansion properties, can create internal pores in the material, significantly reduce density, and improve the material's mechanical properties.
[0125] The results of Comparative Example 2 show that, without the addition of meta-aramid precipitate, despite the foaming of thermally expanded microspheres, the material density is still higher than that of Example 1, and the compressive strength is significantly lower. This reveals the crucial role of the meta-aramid precipitate: as a micron-sized fibrous material, it interweaves with chopped aramid fibers to form a denser and more uniform three-dimensional network framework. This framework, "supported" by the thermally expanded microspheres, can more effectively bear the load, thus imparting higher strength to the material. Without the precipitate, the integrity of the framework is compromised, leading to performance degradation.
[0126] The results of Comparative Example 3, which used organic solvents, highlight the advantages of this invention from both environmental and process perspectives. Although the material's bulk properties are acceptable, the use of toxic organic solvents is detrimental to environmental protection. All embodiments of this invention use water as a medium, avoiding environmental pollution and making the preparation method more valuable for industrial applications.
[0127] In Comparative Example 4, without the addition of surfactant, severe component agglomeration and structural inhomogeneity were observed, resulting in a high density and the lowest strength. This demonstrates that surfactants are not dispensable additives, but rather crucial factors in ensuring uniform dispersion of components in water, preventing fiber agglomeration, and ultimately forming a homogeneous and stable slurry and a uniform foam structure. Without surfactants, even with a correct formulation, it is impossible to produce a high-performance product.
[0128] The comparison between the results of Comparative Example 5 and Example 1 shows that if meta-aramid precipitated fibers are used to replace meta-aramid precipitated products, the fixed morphology, insufficient specific surface area and bonding ability will prevent the formation of an effective microfiber reinforced network, resulting in increased material density and decreased overall performance.
[0129] The comparison between the results of Comparative Example 6 and Example 1 shows that if the proportion of water used in the preparation of meta-aramid precipitate is reduced, the original solution will not be sufficiently dispersed, the precipitate will be coarse and uneven in shape, and the dispersion in the matrix will be poor, thus deteriorating the structure and performance of the final foam.
[0130] The comparison between the results of Comparative Example 7 and Example 1 shows that if the mass ratio of meta-aramid chopped fibers to meta-aramid precipitate is not appropriate, the fibers will be over-wrapped, weakening the rigid support of the skeleton and resulting in a significant reduction in material strength. Therefore, the dosage ratio specified in this invention is more conducive to obtaining aramid composite foam materials with excellent comprehensive performance.
[0131] The comparison between the results of Comparative Example 8 and Example 1 shows that if the mass ratio of meta-aramid chopped fibers to thermally expanded microspheres is not appropriate and the proportion of thermally expanded microspheres is too high, excessive foaming will occur, which will seriously damage the integrity of the fiber network, making the material structure too loose and fragile, and reducing both strength and flame retardancy. Therefore, the dosage ratio specified in this invention is more conducive to maintaining structural stability and strength while reducing density, and is more conducive to obtaining aramid composite foam materials with excellent comprehensive performance.
[0132] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0133] For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims.
Claims
1. An aramid composite foam material, characterized by, The raw materials of the aramid composite foam material, by weight, include: 0.5-1 parts of meta-aramid chopped fibers; 0.2-0.5 parts of meta-aramid precipitate; 0.05-0.2 parts of thermally expandable microspheres; 2-10 parts of water-based adhesive; 0.5-1 parts of surfactant; and 15-50 parts of deionized water. The preparation method of the meta-aramid precipitation product is as follows: after the polymerization reaction of m-phenylenediamine and isophthaloyl chloride in a polar solvent, a meta-formaldehyde solution is obtained. After the meta-formaldehyde solution is fully dispersed in water, the meta-aramid precipitation product is obtained by solid-liquid separation. The mass ratio of the meta-aramid short-cut fibers to the meta-aramid precipitate is (1.5-4):1; In the preparation of the meta-aramid precipitation product, the meta-solvent has a solid content of 18-22% and a viscosity of 200-400 Po. When the meta-formula is dispersed in water, the volume ratio of the meta-formula to water is 1:(10-15). The mass ratio of the meta-aramid short-cut fibers to the thermally expanded microspheres is (4.5-10):
1.
2. The aramid composite foam material according to claim 1, characterized in that, The length of the meta-aramid short-cut fibers is 1-10 mm.
3. The aramid composite foam material according to claim 1, characterized in that, The initial foaming temperature of the thermally expanded microspheres is 80-130℃.
4. The aramid composite foam material according to claim 1, characterized in that, The water-based adhesive is at least one of water-based polyurethane, water-based epoxy, acrylic adhesive, and carboxymethyl cellulose.
5. The aramid composite foam material according to claim 1, characterized in that, The surfactant is at least one of sodium dodecyl sulfonate, hexadecyltrimethylammonium bromide, sorbitan fatty acid ester, and dodecyl dimethyl betaine.
6. A method for preparing an aramid composite foam material according to any one of claims 1-5, characterized in that, The preparation method is as follows: S1. Add the meta-aramid short-cut fibers and the meta-aramid precipitation product to deionized water containing surfactant and mix thoroughly to obtain a uniform and stable slurry. S2. Add water-based adhesive and thermally expanded microspheres to the slurry from step S1, stir gently, and mix evenly; S3. After filtration and molding, the material is dried at low temperature to remove moisture. The temperature is then increased to allow the microspheres to expand and the water-based adhesive to cure simultaneously, resulting in an aramid composite foam material.
7. The method for preparing an aramid composite foam material according to claim 6, characterized in that, In step S1, high-speed stirring is used during mixing, with a stirring speed of 5000-8000 r / min; In step S2, the stirring speed for gentle stirring is 2000-3000 r / min.
8. The method for preparing an aramid composite foam material according to claim 6, characterized in that, In step S3, the temperature for low-temperature drying is 60-70℃; The foaming process is carried out using a gradient heating method: first, maintain the temperature at 80-110℃ for 5-15 minutes, and then maintain the temperature at 130-180℃ for 10-30 minutes.