Polyvinylon and polyimide fiber mixed-weaving felt cloth as well as preparation method and application thereof
By preparing polyimide fiber blended felt, the problems of easy degradation and weak interfacial adhesion of traditional fibers in high-temperature environments have been solved, realizing a high-strength and durable composite material suitable for high-temperature structural components and insulation parts.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-30
- Publication Date
- 2026-04-03
AI Technical Summary
Traditional reinforcing fibers such as glass fiber and carbon fiber are prone to degradation at high temperatures. Polyimide fibers have weak adhesion to the resin matrix, leading to interfacial delamination and fiber damage, which limits their application in pultrusion molding.
The preparation method of polyimide fiber blended felt includes the preparation of polyimide fiber, surface etching, woven blending and coating grafting. Through strict spinning and heat treatment processes, combined with the blending of multiple fibers and modified nano-SiO2 coating, the interfacial bonding is enhanced.
It improves the interlaminar shear strength and durability of polyimide fiber blended felt, making it suitable for high-temperature environments and broadening its application in the field of composite materials, especially high-temperature structural components and insulation parts.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of composite material preparation technology, specifically to a polyimide fiber blended felt fabric, its preparation method, and its application. Background Technology
[0002] Pultrusion is a continuous process for producing composite profiles, widely used in the manufacture of structural components, pipes, and profiles. During pultrusion, the reinforcing fiber material needs to possess excellent heat resistance, mechanical strength, and interfacial adhesion to the resin matrix. Traditional reinforcing fibers such as glass fiber and carbon fiber, while possessing high strength, have limited heat resistance and oxidation resistance, and are particularly prone to degradation at high temperatures, affecting the service life of the composite material. Polyimide fiber, as a high-performance organic fiber, exhibits outstanding high-temperature resistance (long-term operating temperature exceeding 300℃), chemical corrosion resistance, and mechanical properties; however, its surface inertness leads to weak adhesion to the resin matrix, making it prone to interfacial delamination and fiber damage during pultrusion, limiting its application. Current technologies often employ fiber blending or surface treatment to improve performance, but simple blending often fails to optimize interfacial bonding, while conventional surface treatments (such as plasma treatment or chemical etching) may damage the fiber structure or have unsustainable effects. Therefore, there is an urgent need for a fiber felt specifically designed for pultrusion molding that can retain the excellent properties of polyimide fibers while enhancing interfacial bonding through surface modification and hybrid design, thereby improving the overall performance of the composite material. Summary of the Invention
[0003] The purpose of this invention is to provide a polyimide fiber blended felt fabric, its preparation method, and its application.
[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a polyimide fiber blended felt fabric includes the following steps: S1. Preparation of polyimide fiber: Polymerize dianhydride monomers and diamine monomers to obtain polyamic acid, then dissolve it in N,N-dimethylacetamide solvent to obtain an initial fiber solution; dry spin, wash, stretch, dry, and perform stepwise heat treatment to obtain polyimide fiber; S2. Surface etching: The polyimide fiber obtained in step S1 is immersed in NaOH solution, then washed with water until neutral and dried for later use. S3. Woven blended fabric: Using polyimide fiber obtained in step S2 as warp and one or more of glass fiber, basalt fiber, aramid fiber and carbon fiber as weft, a blended fabric is woven. S4. Immerse the blended fabric obtained in step S3 into the coating solution for 30 seconds, and then dry it at 120°C for 20 minutes to obtain the polyimide fiber blended felt.
[0005] Further, in step S1, the dianhydride monomer is pyromellitic dianhydride, and the diamine monomer is 4,4'-diaminodiphenyl ether. The mass ratio of dianhydride monomer to diamine monomer to N,N-dimethylacetamide solvent is 1:0.8~1:0.1~0.3.
[0006] 3. The method for preparing a polyimide fiber blended felt fabric according to claim 1, characterized in that, in step S2, the concentration of the NaOH solution is 4 mol / L, the impregnation temperature is 30℃, and the time is 5 min.
[0007] Further, in step S4, the diameter of the warp filament is 16~22μm, the diameter of the weft filament is 20~24μm, and the warp-to-weft density ratio is 1:0.7~1.2.
[0008] Further, in step S4, the coating solution is prepared by mixing modified nano-SiO2, epoxy resin, and polyacrylamide in a weight ratio of 10~20:50~60:10~30 to obtain the coating solution.
[0009] Furthermore, the preparation method of modified nano-SiO2 is as follows: S41. Pretreatment of nano-SiO2: After drying, the nano-SiO2 is immediately removed and cooled to room temperature for later use; wherein the diameter of the nano-SiO2 particles is 10~50nm. S42. Preparation of coupling agent hydrolysate: Mix anhydrous ethanol, deionized water and glacial acetic acid evenly, and adjust the pH of the mixture to 3-4; slowly add coupling agent dropwise to the mixture, heat the mixture to 40-45℃, and continue stirring for 30-40 minutes to obtain a transparent coupling agent hydrolysate. The coupling agent is selected from one or more of silane coupling agents KH550, KH560, KH570, and KH590, and the mass ratio of anhydrous ethanol:deionized water:glacial acetic acid is 1:0.8:0.05. The dropping rate of the coupling agent is 0.8~1.2 mL / min, and the dropping amount is 1%~3% of the mass of nano-SiO2; S43. Add the pretreated nano-SiO2 from step S41 to anhydrous ethanol and disperse it at 1500-2000 rpm for 15-20 minutes to form a uniform nano-SiO2 / ethanol dispersion. Then, slowly pump the nano-SiO2 / ethanol dispersion into the coupling agent at a pump rate of 5-10 mL / min, while setting the reaction system temperature to 50-55℃ and the stirring speed to 400-500 rpm. Stir at this constant temperature for 1.5-2 hours until the reaction is complete. After the reaction is complete, centrifuge, wash, dry, and pulverize the reaction system to obtain a white powdery modified nano-SiO2. The mass ratio of nano-SiO2 to anhydrous ethanol was 1:0.79; the centrifugation speed was 8000~10000 rpm and the time was 15~20 minutes; the washing process involved repeatedly washing the precipitate with anhydrous ethanol 3~4 times; the drying temperature was 60~65℃ and the time was 4~5 hours, with a vacuum degree of -0.08MPa.
[0010] Furthermore, the preparation method of the coating solution is as follows: (1) Pre-dispersion of modified nano-SiO2: Modified nano-SiO2 is added to anhydrous ethanol and dispersed at a high speed of 1500~2000 rpm for 15~20 minutes to form a modified nano-SiO2 / ethanol dispersion, wherein the solid content of modified nano-SiO2 is 10%~15%; (2) Dissolve polyacrylamide in deionized water to obtain a polyacrylamide aqueous solution with a mass concentration of 5%~8%; stir the polyacrylamide aqueous solution at 300~500 rpm for 30~40 minutes until the solution is transparent and free of flocculent matter; slowly add the dissolved polyacrylamide aqueous solution to the modified nano-SiO2 / ethanol dispersion and continue stirring at 500~800 rpm for 10~15 minutes. (3) Add epoxy resin slowly in 3 to 5 portions to the solution obtained in step (2). After each addition, stir at 300 to 500 rpm for 20 to 30 minutes until the solution is uniformly milky white to obtain the coating solution.
[0011] The polyimide fiber blended felt fabric obtained by the above preparation method has a basis weight of 200g~800g / m².
[0012] The above-mentioned application of polyimide fiber blended felt involves mixing fibers, resins, and the above-mentioned polyimide fiber blended felt, and then using a pultrusion molding process to obtain a polyimide composite material.
[0013] Furthermore, the fiber is one of glass fiber, basalt fiber, or carbon fiber, with a tensile strength of 12-15N; the resin is one of polyurethane, epoxy resin, unsaturated resin, or vinyl ester resin.
[0014] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are: (1) The preparation method of the present invention, through strict spinning and heat treatment processes, produces polyimide fiber with high heat resistance, high strength and stability, which is suitable for high temperature environment of pultrusion molding.
[0015] (2) The preparation method of the present invention significantly improves the interlaminar shear strength and durability of the polyimide fiber blended felt.
[0016] (3) The preparation method of the present invention combines the advantages of various fibers (such as the strength of glass fiber, the corrosion resistance of basalt fiber, and the lightweight and high modulus of carbon fiber) by using a mixed weaving of warp and weft threads, so that the felt is evenly distributed and not easily deformed during the pultrusion process.
[0017] (4) The polyimide fiber blended felt fabric prepared by this invention has a variety of weight specifications, which are suitable for pultrusion molds of different specifications and can produce high-performance composite material products, such as high-temperature resistant structural parts and insulating parts, thus broadening the application of polyimide fiber in the field of composite materials. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the specific embodiments of this invention are described in further detail below. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.
[0019] The first aspect of this invention is to protect a method for preparing a polyimide fiber blended felt, comprising the following steps: S1. Preparation of polyimide methylene fiber, specifically including the following steps: Polyamic acid is obtained by polymerizing dianhydride monomers and diamine monomers, and then dissolved in N,N-dimethylacetamide solvent to obtain an initial fiber solution. The initial fiber solution is then washed with water, stretched, dried, and subjected to stepwise heat treatment to obtain polyimide fiber.
[0020] The dianhydride monomer is pyromellitic dianhydride, and the diamine monomer is 4,4'-diaminodiphenyl ether; the mass ratio of the dianhydride monomer, the diamine monomer and the N,N-dimethylacetamide solvent is 1:0.8~1:0.1~0.3.
[0021] The raw fiber solution was dry-spun at 62℃ through a 60-hole spinneret with an orifice diameter of 0.15mm, with a dry-spinning temperature of 202℃ and a nitrogen temperature of 265℃, to obtain the precursor fiber material. The precursor fiber material was then washed with water at 25-30℃ for 15-32 seconds to remove residual N,N-dimethylacetamide solvent. After washing, the precursor fiber material was stretched at 75℃ with a draw ratio of 1.5, followed by rapid drying at 137-143℃ for 1 second, and then subjected to a step-by-step heat treatment consisting of three stages: low-temperature pretreatment, medium-temperature pre-iminolation, and high-temperature final iminolation. The specific operation of the step-by-step heat treatment is as follows: Stage 1: Low-temperature pretreatment at 100℃ for 30 min to remove trace amounts of moisture and residual N,N-dimethylacetamide solvent from the raw fiber material. Stage 2: Medium-temperature pre-iminoization treatment is carried out under a high-purity nitrogen atmosphere at a temperature of 275°C for 15 minutes to initially form imide bonds and improve fiber stability. Stage 3: High-temperature final imidization is carried out on a drawing machine with a draw ratio of 1.5, a hot plate temperature of 545℃~555℃, a fiber running speed of 1m / min, and the initial fiber is cooled to below 100℃ after drawing.
[0022] S2. Surface etching: The polyimide fiber obtained in step S1 is immersed in NaOH solution, then washed with water until neutral, and dried for later use. The concentration of NaOH solution is 4 mol / L, the immersion temperature is 30℃, and the immersion time is 5 min.
[0023] In this invention, NaOH solution is used to etch the surface of polyimide fiber to form a micro-uneven structure on the surface of the polyimide fiber, increasing the roughness by 30% to 50%. This increases the mechanical interlocking area between the polyimide fiber and the resin raw material in subsequent processing, preventing the resin raw material from sliding on the fiber surface. In addition, the etching process partially hydrolyzes the imide bonds on the polyimide molecular chain, generating active groups such as hydroxyl (-OH) and carboxyl (-COOH) groups, which provide anchor points for subsequent chemical bonding with the coating solution and resin, solving the problem of traditional polyimide fibers lacking reactive sites.
[0024] S3, Woven Blend: Using the polyimide fiber obtained in step S2 as the warp and one or more selected from glass fiber, basalt fiber, aramid fiber, and carbon fiber as the weft, a blended fabric is formed by weaving. The diameter of the parallels of latitude is 20~24μm, and the ratio of the longitude to the latitude density of the parallels of longitude is 1:0.7~1.2.
[0025] It should be noted that machine-woven mixed knitting is an existing knitting technology in this field, and its knitting principle will not be elaborated upon in this invention.
[0026] S4. Coating grafting: The blended fabric obtained in step S3 is immersed in the coating solution for 30 seconds and then dried at 120°C for 20 minutes to obtain the polyimide fiber blended felt.
[0027] In this invention, the coating solution is prepared by mixing the modified nano-SiO2, epoxy resin, and epoxy resin in a weight ratio of 10~20:50~60:10~30 to obtain the coating solution.
[0028] In this invention, the modified nano-SiO2, polyacrylamide, and epoxy resin must be fused and dissolved sequentially. This dissolution order cannot be adjusted to ensure the uniformity of the coating solution. The operation is as follows: (1) Pre-dispersion of modified nano-SiO2: Modified nano-SiO2 needs to be added to anhydrous ethanol and dispersed at 1500~2000 rpm for 15~20 minutes to form modified nano-SiO2 / ethanol dispersion. The solid content of modified nano-SiO2 is controlled at 10%~15% to ensure that the particles are monodisperse and there are no visible agglomerates.
[0029] (2) Dissolving polyacrylamide and mixing it with modified nano-SiO2 / ethanol dispersion Polyacrylamide was dissolved in deionized water to obtain a polyacrylamide aqueous solution with a mass concentration of 5% to 8%. The polyacrylamide aqueous solution was dissolved at a low speed of 300 to 500 rpm for 30 to 40 minutes until the solution was transparent and free of flocculent matter. The dissolved polyacrylamide aqueous solution was slowly added to the modified nano-SiO2 / ethanol dispersion and stirred at 500 to 800 rpm for 10 to 15 minutes.
[0030] (3) Add epoxy resin slowly in 3 to 5 portions to the solution obtained in step (2). After each addition, stir at 300 to 500 rpm for 20 to 30 minutes until the solution is uniformly milky white to obtain the coating solution.
[0031] Because epoxy resin has extremely high viscosity, it must be added last to avoid causing a sudden increase in the viscosity of the system and making the system difficult to disperse.
[0032] The preparation method of modified nano-SiO2 is as follows: S41. Pretreatment of nano-SiO2: Place 100.0g of nano-SiO2 with a particle size of 15nm in a vacuum drying oven, set the temperature to 80~85℃ and the vacuum degree to -0.08~-0.09MPa, and dry for 2~3 hours; remove immediately after drying and cool to room temperature for later use.
[0033] In this invention, the nano-SiO2 particles have a diameter of 10-50 nm and are used to enhance the wear resistance and thermal stability of the coating. Nano-SiO2 pretreatment reduces the interference of physically adsorbed water on the subsequent hydrolytic grafting of the coupling agent, ensuring a high chemical grafting ratio.
[0034] S42. Preparation of coupling agent hydrolysate: Mix anhydrous ethanol, deionized water and glacial acetic acid evenly, and adjust the pH of the mixture to 3-4; slowly add coupling agent dropwise to the mixture, heat the mixture to 40-45℃, and continue stirring for 30-40 minutes to obtain a transparent coupling agent hydrolysate. The coupling agent is selected from one or more of silane coupling agents KH550, KH560, KH570, and KH590. The mass ratio of anhydrous ethanol:deionized water:glacial acetic acid is 1:0.8:0.05. As an embodiment of the present invention, the amount of anhydrous ethanol is 400 mL, the amount of deionized water is 80 mL, and the amount of glacial acetic acid is 0.5 mL. The dropping rate of the coupling agent is 0.8~1.2 mL / min, and the dropping amount is 1%~3% of the nano-SiO2 content.
[0035] S43. Add 100.0g of nano-SiO2 after pretreatment in step S41 to a high-speed disperser, add 100mL of anhydrous ethanol, and disperse at 1500~2000rpm for 15~20 minutes to form a uniform nano-SiO2 / ethanol dispersion; the mass ratio of nano-SiO2 to anhydrous ethanol is 1:0.79; the purpose of this step is to avoid the agglomeration of nano-SiO2 particles and ensure that the surface hydroxyl groups are fully exposed. The nano-SiO2 / ethanol dispersion was then slowly pumped into a three-necked flask containing the coupling agent hydrolysate at a pump rate of 5-10 mL / min to avoid localized high concentrations that could lead to agglomeration. Simultaneously, the reaction system temperature was raised to 50-55°C, and the stirring speed was increased to 400-500 rpm. The mixture was stirred at this constant temperature for 1.5-2 hours, with samples taken every 30 minutes to observe the dispersion's state until the reaction was complete. During this process, the silanol groups generated from the coupling agent hydrolysate undergo a dehydration condensation reaction with the hydroxyl groups on the surface of the nano-SiO2, forming Si-O-Si covalent bonds, thus achieving chemical grafting of the coupling agent hydrolysate onto the nano-SiO2 surface.
[0036] S44. After the reaction is completed, the reaction system is centrifuged, washed, dried and pulverized to obtain white powdered modified nano-SiO2.
[0037] In this invention, the centrifugation process is carried out at a speed of 8000~10000 rpm for 15~20 minutes; the washing process involves repeatedly washing the precipitate with anhydrous ethanol 3~4 times to remove ungrafted free coupling agent and impurities, thus preventing pinholes or peeling of the subsequent coating; the drying process is carried out at a temperature of 60~65℃ for 4~5 hours and at a vacuum of -0.08MPa.
[0038] The modified nano-SiO2 obtained by this invention has a particle size of 10~50nm.
[0039] The epoxy resin is a bisphenol A type epoxy resin with a viscosity of 8000~10000 mPa·s and an epoxy value of 0.48~0.56 mol / 100g, ensuring that the coating has good flowability and curing performance.
[0040] In this invention, the coating solution utilizes a selected silane coupling agent, such as KH550, KH560, or KH570, which has a bifunctional structure. One end of the agent can react with -OH and -COOH on the fiber surface and hydroxyl groups on the nano-SiO2 surface to form covalent bonds, while the other end can react with the active groups of the pultrusion resin (such as polyurethane). This effectively establishes a continuous chemical connection between the fiber, coating, and resin, completely eliminating interfacial gaps. Secondly, the use of nano-SiO2 with a particle size of 10-50 nm increases the contact area between the coating and the resin due to its high specific surface area. Simultaneously, the nanoparticles can fill the microscopic gaps between the resin and the fiber, reducing interfacial defects. Finally, the water solubility of polyacrylamide and the viscosity of epoxy resin work synergistically to ensure that the coating solution can uniformly wet the fiber gaps of the blended fabric, avoiding localized dry spots and ensuring that the resin can fully contact the fiber during the pultrusion process.
[0041] The second aspect of this invention is to protect the polyimide fiber blended felt fabric obtained by the above preparation method, wherein the polyimide fiber blended felt fabric has a basis weight of 200g~800g / m² to meet the needs of different application scenarios.
[0042] <Example 1> The preparation method of the coating solution is as follows: S1. Preparation of modified nano-SiO2: S11. Pretreatment of nano-SiO2: Place 100.0g of nano-SiO2 with a particle size of 15nm in a vacuum drying oven, set the temperature to 85℃ and the vacuum degree to 0.09MPa, and dry for 2 hours; remove immediately after drying and cool to room temperature for later use.
[0043] S12. Preparation of coupling agent hydrolysate: Mix 400 mL of anhydrous ethanol, 80 mL of deionized water, and 0.5 mL of glacial acetic acid thoroughly, and adjust the pH of the mixture to 4; slowly add 1.5 g of coupling agent KH560 to the mixture at a dropping rate of 1.0 mL / min, then heat the mixture to 45 °C and continue stirring for 40 minutes to obtain a transparent coupling agent KH560 hydrolysate; S13. Add 100.0g of nano-SiO2 after pretreatment in step S11 to a high-speed disperser, add 100mL of anhydrous ethanol, and disperse at 2000rpm for 20 minutes to form a uniform nano-SiO2 / ethanol dispersion; then slowly pump the nano-SiO2 / ethanol dispersion into the coupling agent KH560 hydrolysate at a pump speed of 10mL / min, raise the temperature of the reaction system to 55℃, increase the stirring speed to 500rpm, and stir at a constant temperature for 2 hours until the reaction is complete. S14. After the reaction is completed, the reaction system is centrifuged, washed, dried and pulverized to obtain white powdered modified nano-SiO2 with a particle size of 15±2nm.
[0044] The centrifugation process involved a speed of 10,000 rpm and a time of 15-20 minutes. The washing process involved repeatedly washing the precipitate four times with anhydrous ethanol to remove ungrafted free coupling agent and impurities, thus preventing pinholes or peeling of the subsequent coating. The drying process involved a temperature of 65°C, a time of 5 hours, and a vacuum of -0.08 MPa.
[0045] S2. Prepare modified nano-SiO2, epoxy resin, and polyacrylamide in a mass ratio of 10:55:20 respectively. Add the modified nano-SiO2 obtained in step S1 to anhydrous ethanol and disperse at a high speed of 1500~2000 rpm for 15~20 minutes to form a modified nano-SiO2 / ethanol dispersion. The solid content of the modified nano-SiO2 is controlled at 10%~15% to ensure that the particles are monodisperse and there are no visible agglomerates.
[0046] S3. Dissolve polyacrylamide in deionized water to obtain a polyacrylamide aqueous solution with a mass concentration of 5%~8%; dissolve the polyacrylamide aqueous solution at a low speed of 300~500 rpm for 30~40 minutes until the solution is transparent and free of flocculent matter; slowly add the dissolved polyacrylamide aqueous solution to the modified nano-SiO2 / ethanol dispersion and continue to stir at 500~800 rpm for 10~15 minutes.
[0047] S4. Slowly add epoxy resin to the solution obtained in step S3 in 3 to 5 portions. After each addition, stir at 300 to 500 rpm for 20 to 30 minutes until the solution is uniformly milky white to obtain the coating solution.
[0048] <Example 2> A method for preparing a polyimide fiber blended felt fabric includes the following steps: S1. After polymerizing pyromellitic dianhydride with 4,4'-diaminodiphenyl ether to obtain polyamic acid, it is dissolved in N,N-dimethylacetamide solvent to obtain an initial fiber solution. The initial fiber solution is then washed with water, stretched, dried, and subjected to stepwise heat treatment to obtain polyimide fiber. The mass ratio of pyromellitic dianhydride, 4,4'-diaminodiphenyl ether, and N,N-dimethylacetamide solvent is 1:0.95:0.12. The specific operation is as follows: The raw fiber solution was dry-spun at 62℃ through a 60-hole spinneret with an orifice diameter of 0.15mm, with a dry-spinning temperature of 202℃ and a nitrogen temperature of 265℃, to obtain the precursor fiber material. The precursor fiber material was then washed with water at 25-30℃ for 15-32 seconds to remove residual N,N-dimethylacetamide solvent. After washing, the precursor fiber material was stretched at 75℃ with a draw ratio of 1.5, followed by rapid drying at 137-143℃ for 1 second, and then subjected to a step-by-step heat treatment consisting of three stages: low-temperature pretreatment, medium-temperature pre-iminolation, and high-temperature final iminolation. The specific operation of the step-by-step heat treatment is as follows: Stage 1: Low-temperature pretreatment at 100℃ for 30 min to remove trace amounts of moisture and residual N,N-dimethylacetamide solvent from the raw fiber material. Stage 2: Medium-temperature pre-iminoization treatment is carried out under a high-purity nitrogen atmosphere at a temperature of 275°C for 15 minutes to initially form imide bonds and improve fiber stability. Stage 3: High-temperature final imidization is carried out on a drawing machine with a draw ratio of 1.5, a hot plate temperature of 545℃~555℃, a fiber running speed of 1m / min, and the initial fiber is cooled to below 100℃ after drawing.
[0049] The monofilament diameter of the polyimide fiber prepared in this step is 18 μm.
[0050] S2. Surface etching: The polyimide fiber obtained in step S1 is immersed in NaOH solution, then washed with water until neutral, and dried for later use. The concentration of NaOH solution is 4 mol / L, the immersion temperature is 30℃, and the immersion time is 5 min.
[0051] S3. Woven blended fabric: Using polyimide fiber obtained in step S2 as warp and glass fiber as weft, with the warp and weft in a 1:1 warp-to-weft density ratio, a plain weave process is used to make a blended fabric with a weight of 400 g / m². S4. Coating Grafting: The blended fabric is immersed in the coating solution prepared in Example 1 for 30 seconds, then dried at 120°C for 20 minutes to obtain a polyimide fiber blended felt. The epoxy resin has a viscosity of 9000 mPa. s, epoxy value is 0.52mol / 100g.
[0052] <Example 3> Compared with the preparation method of Example 2, the preparation method of the polyimide fiber blended felt in this example is as follows: in S3, the weft yarn is carbon fiber with a single filament diameter of 7μm, and the warp and weft yarns are in a warp-weft density ratio of 1:1.2, and the weight of the blended fabric is 600g / m. In S4, the coupling agent is KH550, and the modified nano-SiO2 particle size is 30nm; the modified nano-SiO2, epoxy resin, and polyacrylamide are mixed in a mass ratio of 8:55:17, and the viscosity of the epoxy resin is 8500mPa. s, epoxy value is 0.50mol / 100g.
[0053] <Example 4> Compared with the preparation method in Example 2, the preparation method of the polyimide fiber blended felt in this example has the following steps: in S1, the ratio of pyromellitic dianhydride, 4,4'-diaminodiphenyl ether and N,N-dimethylacetamide solvent is 1:0.93:0.17, and the polyimide fiber monofilament diameter is 18μm.
[0054] In S3, the weft yarn is basalt fiber with a single filament diameter of 15μm, and the warp and weft yarns are in a warp-weft density ratio of 1:0.8, with a fabric weight of 200g / m. In S4, the coupling agent is KH570, and the modified nano-SiO2 particle size is 50nm; the modified nano-SiO2, epoxy resin, and polyacrylamide are mixed in a mass ratio of 12:58:20, and the pressure is 9500mPa. s, epoxy value is 0.54mol / 100g.
[0055] <Comparative Example 1> It uses commercially available E-glass fiber plain weave fabric with a weight of 400g / m².
[0056] <Comparative Example 2> A method for preparing a polyimide fiber blended felt fabric includes the following steps: S1. Polymerize pyromellitic dianhydride with 4,4'-diaminodiphenyl ether to obtain polyamic acid, then dissolve it in N,N-dimethylacetamide solvent to obtain an initial fiber solution; wash the initial fiber solution with water, stretch, dry, and perform stepwise heat treatment to obtain polyimide fiber.
[0057] The mass ratio of pyromellitic dianhydride, 4,4'-diaminodiphenyl ether, and N,N-dimethylacetamide solvent was 1:0.93:0.17 to prepare polyimide fiber monofilaments with a diameter of 18 μm. Other preparation conditions were the same as those in Example 2.
[0058] S2. Surface etching: The polyimide fiber obtained in step S1 is immersed in NaOH solution, then washed with water until neutral, and dried for later use. The concentration of NaOH solution is 4 mol / L, the immersion temperature is 30℃, and the immersion time is 5 min.
[0059] S3. Woven Blend: Using polyimide fiber obtained in step S2 as warp and glass fiber as weft, with a warp-to-weft density ratio of 1:1, a blended fabric is made using a plain weave process. The weight of the blended fabric is 400 g / m².
[0060] <Comparative Example 3> S1. Polymerize pyromellitic dianhydride with 4,4'-diaminodiphenyl ether to obtain polyamic acid, then dissolve it in N,N-dimethylacetamide solvent to obtain an initial fiber solution; wash the initial fiber solution with water, stretch, dry, and perform stepwise heat treatment to obtain polyimide fiber.
[0061] The ratio of pyromellitic dianhydride, 4,4'-diaminodiphenyl ether, and N,N-dimethylacetamide solvent was 1:0.92:0.18. Other preparation conditions were the same as in Example 2, and the diameter of the polyimide fiber monofilament was 18 μm.
[0062] S2. Surface etching: The polyimide fiber obtained in step S1 is immersed in a 30% HCl solution for acid etching. The immersion temperature is 30℃ and the time is 5min. Then, it is washed with water until neutral and dried for later use.
[0063] S3. Woven Blend: Using polyimide fiber obtained in step S2 as the warp and polyimide fiber (monofilament diameter 20μm) as the weft, with the warp and weft in a warp-to-weft density ratio of 1:1.2, a plain weave process is used to make a blended fabric with a weight of 600g / m². S4. Coating Grafting: The blended fabric is immersed in epoxy resin for 30 seconds and then dried at 120℃ for 20 minutes to obtain a polyimide fiber blended felt. The epoxy resin has a viscosity of 8500 mPa. s, epoxy value is 0.50mol / 100g.
[0064] The materials obtained in Examples 2-7 and Comparative Examples 1-3 were subjected to performance tests. In this invention, GB / T33579-2017 "Test Method for Interlaminar Shear Strength of Fiber Reinforced Plastics" was used to test the interlaminar shear strength (ILSS) between the fiber and the polyurethane resin; thermogravimetric analysis (TGA) was used to test the 5% mass loss temperature; after a xenon lamp aging test (1000h, irradiation intensity 1000W / m²), the tensile strength retention rate and UV resistance were tested; the mechanical strength of the materials was tested according to GB / T 3923.1-2013 "Textiles - Tensile Properties of Fabrics - Part 1: Determination of Breaking Strength and Elongation at Break (Strip Method)". The test results are shown in Table 1. Table 1
[0065] As shown in Table 1, in terms of interfacial bonding strength, the interlaminar shear strength of Examples 2-4 is significantly higher than that of the comparative examples. Among them, Example 3 reaches 48.9 MPa, which is 72.8% higher than that of Comparative Example 1 and 38.9% higher than that of Comparative Example 3. This is because NaOH etching increases the surface roughness of the fiber, and the coupling agent modified nano-SiO2 coating constructs a chemical bonding bridge, which greatly improves the compatibility between the fiber and the resin.
[0066] In terms of heat resistance, the 5% mass loss temperature of each embodiment exceeded 530°C, while that of Comparative Example 1 was only 385°C. The heat resistance of Comparative Example 3 decreased to 498°C due to the lack of optimization in the fiber preparation process. This indicates that the spinning, heat treatment process and nano-coating of the present invention jointly improved the high-temperature stability of the material.
[0067] In terms of UV resistance, the tensile strength retention rate of each embodiment exceeded 91%, which is much higher than 75.6% of Comparative Example 1 and 82.4% of Comparative Example 2, demonstrating the UV resistance of the polyimide fiber itself and the protective effect of the coating on the fiber.
[0068] In terms of mechanical strength, Example 3 has the highest breaking strength (98.7 kN / m), which is combined with the high modulus advantage of carbon fiber and the fact that the fiber structure was not damaged throughout the process. Comparative Example 1 has the lowest breaking strength due to the single fiber type, which verifies the synergistic reinforcement effect of the hybrid structure.
[0069] This invention employs a comprehensive process design involving "customized polyimide fiber preparation + surface etching + multi-element blending + functional coating" to ensure that the blended felt fabric meets the stringent requirements of pultrusion molding in terms of interfacial adhesion, heat resistance, UV resistance, and mechanical strength. Among these, the combination of polyimide fiber and carbon fiber (Example 3) exhibits the best overall performance and is suitable for high-end applications such as aerospace; the combination of polyimide fiber and glass fiber (Example 2) offers excellent cost-effectiveness and is suitable for general applications such as construction and automotive.
[0070] The third aspect of this invention is the application of the polyimide fiber blended felt, specifically including the following steps: impregnating fibers in resin, passing the impregnated fibers through a pre-forming mold and the polyimide fiber blended felt, and then cutting it to a specified length after traction and high-temperature curing to obtain a polyimide composite material. The fibers can be one of glass fiber, basalt fiber, or carbon fiber, with a tensile strength of 12-15 N; the resin can be one of polyurethane, epoxy resin, unsaturated resin, or vinyl ester resin.
[0071] The specific process flow is as follows: Fiber → Fiber impregnated with resin → Resin-impregnated fiber and felt are combined, cured at high temperature in a heated mold, and then cut.
[0072] The preform mold is designed to be made of ceramic / alumina and polytetrafluoroethylene.
[0073] The length of the heating mold is 1.3m; the total length of the heating zone of the heating mold is 80cm, which is divided into 3 temperatures: the first temperature zone is 15cm long and the heating temperature is 100~120℃; the second temperature zone is 20cm long and the temperature is 140~160℃; the third temperature zone is 25cm long and the temperature is 160~190℃.
[0074] The pultrusion machine is a tracked pultrusion machine with a traction speed of 600~1500mm / min. The pultrusion length of the tracked pultrusion machine is 1200mm, and the pressure is set at 10000~15000N.
[0075] The aforementioned polyimide composite materials can be applied to fields such as aerospace, new energy, rail transportation, and chemical corrosion prevention production processes, making up for the performance shortcomings of traditional metal and single-fiber composite materials.
[0076] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.
Claims
1. A method for preparing a polyimide-styrene fiber blended felt, characterized in that, Includes the following steps: S1. Preparation of polyimide fiber: Polymerize dianhydride monomers and diamine monomers to obtain polyamic acid, then dissolve it in N,N-dimethylacetamide solvent to obtain an initial fiber solution; dry spin, wash, stretch, dry, and perform stepwise heat treatment to obtain polyimide fiber; S2. Surface etching: The polyimide fiber obtained in step S1 is immersed in NaOH solution, then washed with water until neutral and dried for later use. S3. Woven blended fabric: Using polyimide fiber obtained in step S2 as warp and one or more of glass fiber, basalt fiber, aramid fiber and carbon fiber as weft, a blended fabric is woven. S4. Immerse the blended fabric obtained in step S3 into the coating solution for 30 seconds, and then dry it at 120°C for 20 minutes to obtain the polyimide fiber blended felt.
2. The method for preparing a polyimide fiber blended felt fabric according to claim 1, characterized in that, In step S1, the dianhydride monomer is pyromellitic dianhydride, and the diamine monomer is 4,4'-diaminodiphenyl ether. The mass ratio of dianhydride monomer to diamine monomer to N,N-dimethylacetamide solvent is 1:0.8~1:0.1~0.
3.
3. The method for preparing a polyimide fiber blended felt fabric according to claim 1, characterized in that, In step S2, the concentration of the NaOH solution is 4 mol / L, the immersion temperature is 30℃, and the immersion time is 5 min.
4. The method for preparing a polyimide fiber blended felt fabric according to claim 1, characterized in that, In step S4, the diameter of the warp filament is 16~22μm, the diameter of the weft filament is 20~24μm, and the warp-to-weft density ratio is 1:0.7~1.
2.
5. The method for preparing a polyimide fiber blended felt fabric according to claim 1, characterized in that, In step S4, the coating solution is prepared by mixing modified nano-SiO2, epoxy resin, and polyacrylamide in a weight ratio of 10~20:50~60:10-30 to obtain the coating solution.
6. The method for preparing a polyimide fiber blended felt fabric according to claim 5, characterized in that, The preparation method of modified nano-SiO2 is as follows: S41. Pretreatment of nano-SiO2: After drying, the nano-SiO2 is immediately removed and cooled to room temperature for later use; wherein the diameter of the nano-SiO2 particles is 10~50nm. S42. Preparation of coupling agent hydrolysate: Mix anhydrous ethanol, deionized water and glacial acetic acid evenly, and adjust the pH of the mixture to 3-4; slowly add coupling agent dropwise to the mixture, heat the mixture to 40-45℃, and continue stirring for 30-40 minutes to obtain a transparent coupling agent hydrolysate. The coupling agent is selected from one or more of silane coupling agents KH550, KH560, KH570, and KH590, and the mass ratio of anhydrous ethanol:deionized water:glacial acetic acid is 1:0.8:0.
05. The dropping rate of the coupling agent is 0.8~1.2 mL / min, and the dropping amount is 1%~3% of the mass of nano-SiO2; S43. Add the pretreated nano-SiO2 from step S41 to anhydrous ethanol and disperse it at 1500-2000 rpm for 15-20 minutes to form a uniform nano-SiO2 / ethanol dispersion. Then, slowly pump the nano-SiO2 / ethanol dispersion into the coupling agent at a pump rate of 5-10 mL / min, while setting the reaction system temperature to 50-55℃ and the stirring speed to 400-500 rpm. Stir at this constant temperature for 1.5-2 hours until the reaction is complete. After the reaction is complete, centrifuge, wash, dry, and pulverize the reaction system to obtain a white powdery modified nano-SiO2. The mass ratio of nano-SiO2 to anhydrous ethanol was 1:0.79; the centrifugation speed was 8000~10000 rpm and the time was 15~20 minutes; the washing process involved repeatedly washing the precipitate with anhydrous ethanol 3~4 times; the drying temperature was 60~65℃ and the time was 4~5 hours, with a vacuum degree of -0.08MPa.
7. The method for preparing a polyimide fiber blended felt fabric according to claim 6, characterized in that, The preparation method of the coating solution is as follows: (1) Pre-dispersion of modified nano-SiO2: Modified nano-SiO2 is added to anhydrous ethanol and dispersed at a high speed of 1500~2000 rpm for 15~20 minutes to form a modified nano-SiO2 / ethanol dispersion, wherein the solid content of modified nano-SiO2 is 10%~15%; (2) Dissolve polyacrylamide in deionized water to obtain a polyacrylamide aqueous solution with a mass concentration of 5%~8%; stir the polyacrylamide aqueous solution at 300~500 rpm for 30~40 minutes until the solution is transparent and free of flocculent matter; slowly add the dissolved polyacrylamide aqueous solution to the modified nano-SiO2 / ethanol dispersion and continue stirring at 500~800 rpm for 10~15 minutes. (3) Add epoxy resin slowly in 3 to 5 portions to the solution obtained in step (2). After each addition, stir at 300 to 500 rpm for 20 to 30 minutes until the solution is uniformly milky white to obtain the coating solution.
8. The polyimide fiber blended felt fabric obtained by any one of the preparation methods of claims 1-7, characterized in that, The weight of the polyimide fiber blended felt is 200g~800g / m².
9. The application of the polyimide fiber blended felt fabric as described in claim 8, characterized in that, The polyimide composite material is obtained by mixing fibers, resins and the polyimide fiber blended felt fabric as described in claim 8, and then processing it by extrusion molding.
10. The application of the polyimide fiber blended felt fabric as described in claim 9, characterized in that, The fiber is one of glass fiber, basalt fiber, or carbon fiber, with a tensile strength of 12~15N; the resin is one of polyurethane, epoxy resin, unsaturated resin, or vinyl resin.