High-strength carbon fiber needled felt and preparation method thereof

Abstract

The invention discloses a high-strength carbon fiber needled felt and a preparation method thereof, belongs to the technical field of carbon fiber felt processing, and is used for solving the technical problem that the mechanical strength and thermal oxidation resistance of a carbon fiber needled felt in the prior art need to be further improved. Stirring until the system is dissolved, adding PAN-based carbon fibers and asphalt carbon fibers into the reaction system, carrying out ultrasonic dispersion for 20-30 minutes, and adding a sodium hydroxide solution into the reaction system. According to the invention, PAN-based and pitch-based carbon fibers are used as raw materials, ZrO2 is loaded on the surfaces of the fibers, needling is carried out to form a net, boron-modified organic-inorganic hybrid phenolic resin, nano silicon carbide and aluminum oxide are used to reinforce the carbon fiber net, and a compact and stable carbon-ceramic composite structure is constructed. The mechanical strength and the thermal oxidation resistance of the carbon fiber needled felt are obviously improved.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber felt processing technology, specifically to a high-strength carbon fiber needled felt and its preparation method. Background Technology

[0002] Carbon fiber, with its excellent properties such as high specific strength, high specific modulus, low density, high temperature resistance, and corrosion resistance, is widely used in aerospace, automotive industry, rail transportation, energy equipment, and protective materials. Carbon fiber needle-punched felt is a high-performance nonwoven material that combines the high specific strength, high specific modulus, high temperature resistance, and corrosion resistance of carbon fiber with the three-dimensional structural advantages of needle-punching technology. It is widely used in high-end fields such as aerospace thermal protection systems, flame-retardant layers for new energy vehicle batteries, thermal insulation pads for semiconductor silicon furnaces, high-temperature gas filtration, and industrial furnace insulation.

[0003] In existing technologies, carbon fiber needled felt is a porous material prepared from chopped carbon fiber filaments through processes such as web laying, needle punching, and heat treatment. Needle-punched felt mainly relies on the physical entanglement between fibers to achieve bonding. The interfacial interaction between fibers is weak, resulting in limited breaking strength and peel force. Under load and friction conditions, it is prone to delamination or damage. The presence of pores and defects inside the needle-punched felt allows oxygen to easily penetrate and diffuse. Furthermore, carbon fibers are easily oxidized and degraded in high-temperature and oxygen-rich environments, accelerating the oxidation and destruction of the carbon fiber skeleton, thereby causing a rapid decline in material strength. The heat oxidation resistance of the material needs to be further improved. Summary of the Invention

[0004] The purpose of this invention is to provide a high-strength carbon fiber needled felt and its preparation method, which solves the technical problem that the mechanical strength and heat oxidation resistance of carbon fiber needled felt need to be further improved in the prior art.

[0005] The objective of this invention can be achieved through the following technical solution: a method for preparing high-strength carbon fiber needled felt, comprising the following steps:

[0006] S1. Mix zirconium nitrate and deionized water, stir until the system is dissolved, add PAN-based carbon fiber and pitch carbon fiber to the reaction system, ultrasonically disperse for 20-30 min, add sodium hydroxide solution to the reaction system, adjust the pH of the system to 8, and then perform post-treatment to obtain mixed carbon fiber;

[0007] S2. Epoxy-modified carbon fiber is prepared by surface modification of mixed carbon fiber using KH-560. Then, the epoxy-modified carbon fiber is fed into a carding machine, where it is dispersed and arranged in parallel by carding needles. The carded epoxy-modified carbon fiber is then evenly laid into a carbon fiber mesh by a web laying machine.

[0008] S3. Spray the composite phenolic resin solution evenly onto both sides of the carbon fiber mesh at a temperature of 120-130℃ in the form of a spray, and cure for 6-8 minutes to obtain the carbon fiber mesh.

[0009] S4. After stacking several carbon fiber meshes layer by layer, they are needled and fixed to obtain carbon fiber needled felt blanks, and then heat-treated to obtain carbon fiber needled felt.

[0010] Further, in step S1, the ratio of zirconium nitrate, deionized water, PAN-based carbon fiber, and pitch carbon fiber is 3-5g:500mL:20-25g:25-30g, the concentration of sodium hydroxide solution is 3-5mol / L, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed with purified water until neutral and then dried, the filter cake is transferred to a drying oven at a temperature of 80-90℃ and dried to constant weight to obtain mixed carbon fiber.

[0011] Furthermore, in step S2, the fiber mesh density is 20-30 g / m². 2 In step S3, the spraying volume of the composite phenolic resin solution is 30-40 mL / m³. 2 .

[0012] Furthermore, the preparation method of epoxy-modified carbon fiber is as follows: mixed carbon fiber, KH-560 and anhydrous ethanol are mixed and ultrasonically dispersed for 30-50 min. The temperature of the reaction system is raised to 50-60℃, sodium hydroxide solution is added to the reaction system, and the reaction is kept at the temperature for 60-80 min. After post-treatment, epoxy-modified carbon fiber is obtained.

[0013] Furthermore, the ratio of the mixed carbon fiber, KH-560, anhydrous ethanol, and hydrochloric acid solution is 10g:2.6-3.2g:200mL:20mL, the concentration of the sodium hydroxide solution is 2-3mol / L, and the post-treatment includes: after the reaction is complete, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed with purified water until neutral and then dried, the filter cake is transferred to a drying oven at a temperature of 70-80℃ and dried to constant weight to obtain epoxy modified carbon fiber.

[0014] Furthermore, in step S3, the method for preparing the composite phenolic resin solution is as follows: the composite phenolic resin and toluene are mixed and stirred until the system is dissolved, nano-silicon carbide and nano-alumina are added to the reaction system, and ultrasonically dispersed for 30-50 minutes to obtain the composite phenolic resin solution. The ratio of the amount of the composite phenolic resin, toluene, nano-silicon carbide and nano-alumina is 5g:15mL:1.2-1.4g:1.3-1.5g.

[0015] Furthermore, the composite phenolic resin is obtained through the following steps:

[0016] A1. Mix phenol, formaldehyde solution and alkaline solution, raise the temperature of the reaction system to 60-70℃, keep the reaction at this temperature for 90-110 min, raise the temperature of the reaction system to 80-90℃, add phenylboronic acid to the reaction system, keep the reaction at this temperature for 2-3 h, and then perform post-treatment to obtain boron-modified phenolic resin.

[0017] A2. Mix boron-modified phenolic resin and 1,4-dioxane. Raise the temperature of the reaction system to 60-70℃ and stir until the system dissolves. Add propyltriethoxysilane isocyanate to the reaction system and keep it at the temperature for 70-90 min. Add octamethylcyclotetrasiloxane, tetraethyl orthosilicate, and 3-aminopropyltriethoxysilane to the reaction system and stir to disperse for 20-30 min. Add a catalyst to the reaction system and raise the temperature of the reaction system to 85-95℃. Keep it at the temperature for 2-3 h. After post-treatment, obtain composite phenolic resin.

[0018] Further, in step A1, the ratio of phenol, formaldehyde solution, alkali solution and phenylboronic acid is 5-6g:9-11mL:1.5g:0.9-1.1g, the formaldehyde solution is a 35-37wt% aqueous formaldehyde solution, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is reduced to -0.1MPa, and low-boiling substances are removed by vacuum evaporation to obtain boron-modified phenolic resin.

[0019] Further, in step A2, the ratio of boron-modified phenolic resin, 1,4-dioxane, propyltriethoxysilane isocyanate, octamethylcyclotetrasiloxane, tetraethyl orthosilicate, 3-aminopropyltriethoxysilane, and catalyst is 20g:200mL:2-3g:6-8g:1.9-2.1g:1.6-1.8g:10mL, and the catalyst is 50-60wt% sulfuric acid. The post-treatment includes: after the reaction is complete, the reaction system is evaporated under negative pressure to -0.1MPa, low-boiling substances are removed by vacuum evaporation, toluene is added to the reaction system, and the system is stirred until dissolved. Purified water is added to the reaction system, and the system is stirred and dispersed for 20-30 minutes. The system is allowed to stand and separate the liquids. The organic phase is washed with purified water until neutral and then transferred to a rotary evaporator with a water bath temperature of 80-90℃ to remove low-boiling substances by vacuum evaporation to obtain composite phenolic resin.

[0020] Furthermore, in step S4, the carbon fiber mesh has 5-7 layers and a needle-punching density of 110 needles / cm. 2 The needle-punching depth is 11-12 mm; the heat treatment method is as follows: the carbon fiber needle-punched felt blank is transferred to a hot press at a temperature of 120-130℃ and a pressure of 0.3-0.5MPa, and hot-pressed for 12-15 minutes. Then it is transferred to a calcining furnace, and under an argon atmosphere, the temperature is raised to 800-1000℃ and calcined for 60-80 minutes. It is then naturally cooled to room temperature to obtain carbon fiber needle-punched felt.

[0021] One of them is a high-strength carbon fiber needled felt, which is processed using the above-mentioned method for preparing a high-strength carbon fiber needled felt.

[0022] The present invention has the following beneficial effects:

[0023] 1. This invention uses PAN-based carbon fiber and pitch carbon fiber as raw materials for carbon fiber needle-punched felt. After carding and orientation, a stable three-dimensional bridging network is formed during the needle-punching process. Pitch-based fibers have a high degree of graphitization, resulting in high elastic modulus and thermal conductivity, while PAN-based fibers offer better strength, fracture strain, and toughness. When the two are blended in a reasonable ratio, the pitch-based fibers provide a high-modulus skeleton to bear and stabilize the main load, while the PAN-based fibers provide toughening and energy dissipation channels, improving the mechanical strength of the material. KH-560 is used for surface treatment of the mixed carbon fibers. Modification enhances the surface reactivity of the mixed carbon fibers. A composite phenolic resin solution is sprayed onto the carbon fiber mesh via atomization, forming a composite phenolic resin and nano-titanium carbide and nano-alumina coating on the carbon fiber mesh. This constructs an organic-inorganic hybrid matrix, increasing the glass transition temperature and coking yield of the phenolic resin, resulting in a denser matrix after carbonization. The synergistic effect of these three elements significantly improves peel strength and tensile strength, and generates a viscous glass / ceramic protective layer in high-temperature air, slowing down oxygen penetration from the pore channels and improving the heat oxidation resistance of the carbon fiber needle-punched felt.

[0024] 2. This invention prepares boron-modified phenolic resin by embedding boron atoms into a phenolic resin network, and then introduces polysiloxane chains onto the boron-modified phenolic resin backbone to form an organic-inorganic hybrid phenolic resin. The composite phenolic resin is composed of the carbon backbone of the boron-modified phenolic resin, the inorganic structure of the silicon-oxygen network, and the organosilicon segments. The boron-modified phenolic resin itself has a high degree of crosslinking and coking rate. After carbonization, it generates a dense and continuous carbon phase, ensuring effective load transfer between fibers. The polysiloxane network introduced into the composite phenolic resin interacts with the coupling layer on the fiber surface. The combination further strengthens the interfacial bonding. After dispersion, nano-silicon carbide and nano-alumina play a role in crack deflection, stress transfer and micro-anchoring at the microscopic level, inhibiting crack failure and significantly improving the fracture strength of needle-punched felt, resulting in higher load-bearing capacity and smaller strength fluctuations. The high degree of cross-linking and the introduction of inorganic phase enhance the rigidity of the matrix. The polysiloxane chains introduced on the boron-modified phenolic resin skeleton form strong chemical bonds on the fiber surface, while the nanofiller particles embedded in the fiber gaps form "micro-anchoring", which significantly improves the interlayer friction and interfacial shear resistance, and improves the mechanical strength of the material.

[0025] 3. This invention involves preparing a carbon fiber mesh by laying epoxy-modified carbon fibers, followed by needle punching and heat treatment to obtain carbon fiber needle-punched felt. During the heat treatment process, a thin layer of zirconium hydroxide is deposited on the surface of PAN-based carbon fibers or pitch-carbon fibers while the composite phenolic resin is carbonized. In subsequent heat treatment, the zirconium hydroxide is converted into nano-ZrO2 loading. The nano-ZrO2 remains stable after carbonization, has a high melting point and low diffusion coefficient, and forms a discrete but progressively stronger inorganic barrier on the fiber surface. ZrO2, nano-silicon carbide, and nano-alumina, as inorganic fillers, not only act as a skeleton and filler but also effectively improve the thermal stability of the composite system. Stability and antioxidant properties: The BO structure in the composite phenolic resin provides a higher char formation rate and a self-healing B2O3 glass phase. The polysiloxane inorganic network and nanoparticles together form a dense and dispersed barrier structure, which greatly reduces the oxygen permeation path. At the same time, nano-silicon carbide and nano-alumina also play an important role in thermal conduction and structural stability, avoiding local overheating and thermal stress concentration. Combined with the crosslinking between epoxy silane and silane coupling agent, as well as the interfacial anchoring effect of Zr-O-Si bridge, the composite system not only maintains high mechanical strength and interfacial bonding force in high-temperature oxidizing environments, but also effectively inhibits peeling and strength loss. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In this invention, the PAN-based carbon fiber is a polyacrylonitrile-based carbon fiber with a carbon content of 99.9%, a diameter of 7-10 μm, and a length of 4-6 mm;

[0028] In this invention, the carbon content of the pitch carbon fiber is 95.5-98%, the diameter is 7-10 μm, and the length is 7-10 mm;

[0029] In this invention, KH-560 is γ-glycidyl etheroxypropyltrimethoxysilane, CAS number 2530-83-8.

[0030] Example 1

[0031] This embodiment provides a method for preparing high-strength carbon fiber needled felt, including the following steps:

[0032] Step 1: Preparation of epoxy-modified carbon fibers

[0033] Weigh out 30g of zirconium nitrate and 5L of deionized water and add them to the reaction vessel. Stir until the system is dissolved. Add 200g of PAN-based carbon fiber and 250g of pitch carbon fiber to the reaction vessel and sonicate for 20min. Add 3mol / L sodium hydroxide solution to the reaction vessel to adjust the pH of the system to 8. Lower the temperature of the reaction vessel to room temperature, filter, wash the filter cake with purified water until neutral, and then dry it. Transfer the filter cake to a drying oven at 80℃ and dry it to constant weight to obtain mixed carbon fiber.

[0034] During the reaction, zirconium nitrate is dissolved in deionized water. Ultrasonic dispersion is used to promote the uniform dispersion of zirconium nitrate with PAN-based carbon fibers and pitch carbon fibers. The pH of the system is then adjusted by sodium hydroxide solution, and zirconium ions form zirconium hydroxide, which is loaded onto PAN-based carbon fibers and pitch carbon fibers to form mixed carbon fibers.

[0035] Weigh out 500g of mixed carbon fiber, 130g of KH-560, and 10L of anhydrous ethanol and add them to a reaction vessel. Disperse the mixture ultrasonically for 30min. Raise the temperature of the reaction vessel to 50℃ and add 1L of 2mol / L sodium hydroxide solution. Keep the reaction vessel at this temperature for 60min. Lower the temperature of the reaction vessel to room temperature and filter the mixture. Wash the filter cake with purified water until neutral and then dry it. Transfer the filter cake to a drying oven at 70℃ and dry it to constant weight to obtain epoxy-modified carbon fiber.

[0036] During the reaction, sodium hydroxide promotes the hydrolysis of siloxane bonds on KH-560 molecules to form silanols. The silanols then chemically bond with active sites on the surface of the mixed carbon fibers, forming an epoxy modification on the mixed carbon fibers, thus preparing epoxy-modified carbon fibers.

[0037] Step 2: Preparation of composite phenolic resin solution

[0038] Weigh out 500g of phenol, 900mL of 35wt% formaldehyde aqueous solution and 150g of 25wt% sodium hydroxide solution and add them to the reaction vessel. Stir the reaction vessel and raise the temperature to 60℃. Keep the reaction vessel at this temperature for 90min. Raise the temperature to 80℃ and add 90g of phenylboronic acid to the reaction vessel. Keep the reaction vessel at this temperature for 2h. Then, reduce the pressure in the reaction vessel to -0.1MPa and remove low-boiling substances by vacuum evaporation to obtain boron-modified phenolic resin.

[0039] In the reaction process, in the presence of sodium hydroxide, the hydroxyl groups of phenol are partially deprotonated to generate negatively charged phenoxy ions, which enhances the ortho and para reactivity of the benzene ring. Formaldehyde molecules react with the activated benzene ring at the ortho or para position as electrophiles, introducing hydroxymethyl groups to generate hydroxymethylphenol. The hydroxymethylphenols further undergo condensation reactions and are connected by methylene bridges to form linear or network phenolic resin structures. The boron hydroxyl groups in phenylboronic acid undergo esterification or coordination with the phenolic hydroxyl groups to form BOC bonds. At the same time, boron can also crosslink with other hydroxymethyl or phenolic hydroxyl groups in the resin, embedding boron atoms into the network to obtain boron-modified phenolic resin.

[0040] Weigh out 600g of boron-modified phenolic resin and 6L of 1,4-dioxane and add them to a reaction vessel. Stir the reaction vessel to 60℃ and keep it warm while stirring until the system is dissolved. Add 60g of propyltriethoxysilane isocyanate to the reaction vessel and keep it warm for 70min. Add 180g of octamethylcyclotetrasiloxane, 57g of tetraethyl orthosilicate, and 48g of 3-aminopropyltriethoxysilane to the reaction vessel and stir and disperse for 20min. Add 300mL of 50wt% sulfuric acid to the reaction vessel and raise the temperature of the reaction vessel to 85℃. Keep it warm for 2h. Apply a negative pressure to the reaction vessel to -0.1MPa and remove low-boiling substances by vacuum evaporation. Add 6L of toluene to the reaction vessel and stir until the system is dissolved. Add 2L of purified water to the reaction vessel and stir and disperse for 20min. Let it stand and separate the liquids. Wash the organic phase with purified water until neutral and transfer it to a rotary evaporator with a water bath temperature of 80℃. Remove low-boiling substances by vacuum evaporation to obtain composite phenolic resin.

[0041] In the reaction process, after dissolving the boron-modified phenolic resin, the isocyanate group on propyltriethoxysilane condenses with the oxygen-containing group in the boron-modified phenolic resin, introducing triethoxysilane onto the boron-modified phenolic resin. Subsequently, octamethylcyclotetrasiloxane and 3-aminopropyltriethoxysilane are added. Under the action of strong acid, the cyclic siloxanes undergo ring opening to form linear or partially cross-linked siloxane segments. These segments further condense with silane hydrolysates, gradually embedding into the phenolic skeleton to form an organic-inorganic hybrid structure, thus preparing a composite phenolic resin.

[0042] Weigh out 500g of composite phenolic resin and 1500mL of toluene and add them to the reaction vessel. Stir until the system is dissolved. Add 120g of nano silicon carbide and 130g of nano alumina to the reaction vessel and sonicate for 30min to obtain a composite phenolic resin solution.

[0043] Step 3: Preparation of carbon fiber mesh

[0044] Epoxy-modified carbon fibers are fed into a carding machine, where carding needles disperse and arrange the fibers in parallel. The fibers are then passed through a web-laying machine at a density of 20 g / m². 2 The web-laying density is used to evenly lay the combed epoxy-modified carbon fiber into a carbon fiber web.

[0045] The carbon fiber mesh was heated to 120°C, and then the composite phenolic resin solution was applied at a rate of 30 mL / m². 2 The appropriate amount of atomized spray is applied to both sides of the carbon fiber mesh, and cured for 6 minutes to obtain the carbon fiber mesh.

[0046] Step 4: Preparation of carbon fiber needled felt

[0047] The carbon fiber mesh was stacked in layers of 5 and then placed in a needle punching machine, with a fixed needle punching density of 110 needles / cm. 2 The needle-punching depth is 11mm for needle fixation to obtain carbon fiber needle-punched felt blank;

[0048] The carbon fiber needle-punched felt blank is transferred to a hot press at 120℃ and 0.3MPa for 12 minutes, then transferred to a calcining furnace. Under an argon atmosphere, the temperature is raised to 800℃ and calcined for 60 minutes. The blank is then allowed to cool naturally to room temperature to obtain carbon fiber needle-punched felt.

[0049] Example 2

[0050] This embodiment provides a method for preparing high-strength carbon fiber needled felt, including the following steps:

[0051] Step 1: Preparation of epoxy-modified carbon fibers

[0052] Weigh out 40g of zirconium nitrate and 5L of deionized water and add them to the reaction vessel. Stir until the system is dissolved. Add 230g of PAN-based carbon fiber and 230g of pitch carbon fiber to the reaction vessel and sonicate for 25min. Add 4mol / L sodium hydroxide solution to the reaction vessel to adjust the pH of the system to 8. Lower the temperature of the reaction vessel to room temperature, filter, wash the filter cake with purified water until neutral, and then dry it. Transfer the filter cake to a drying oven at 85℃ and dry it to constant weight to obtain mixed carbon fiber.

[0053] Weigh out 500g of mixed carbon fiber, 145g of KH-560, and 10L of anhydrous ethanol and add them to the reaction vessel. Disperse the mixture ultrasonically for 40min. Raise the temperature of the reaction vessel to 55℃ and add 1L of 2.5mol / L sodium hydroxide solution. Keep the reaction vessel at this temperature for 70min. Lower the temperature of the reaction vessel to room temperature, filter the mixture, wash the filter cake with purified water until neutral, and then dry it. Transfer the filter cake to a drying oven at 75℃ and dry it to constant weight to obtain epoxy-modified carbon fiber.

[0054] Step 2: Preparation of composite phenolic resin solution

[0055] Weigh out 550g of phenol, 1000mL of 36wt% formaldehyde aqueous solution and 150g of 30wt% sodium hydroxide solution and add them to the reaction vessel. Stir the mixture and raise the temperature of the reaction vessel to 65℃. Keep the temperature for 100min and raise the temperature of the reaction vessel to 85℃. Add 100g of phenylboronic acid to the reaction vessel and keep the temperature for 2.5h. Bring the temperature of the reaction vessel to a negative pressure of -0.1MPa and remove low-boiling substances by vacuum evaporation to obtain boron-modified phenolic resin.

[0056] Weigh out 600g of boron-modified phenolic resin and 6L of 1,4-dioxane and add them to a reaction vessel. Stir the reaction vessel to 65℃ and keep it warm while stirring until the system is dissolved. Add 75g of propyltriethoxysilane isocyanate to the reaction vessel and keep it warm for 80min. Add 210g of octamethylcyclotetrasiloxane, 60g of tetraethyl orthosilicate, and 51g of 3-aminopropyltriethoxysilane to the reaction vessel and stir and disperse for 25min. Add 300mL of 55wt% sulfuric acid to the reaction vessel and raise the temperature of the reaction vessel to 90℃. Keep it warm for 2.5h. Apply a negative pressure to the reaction vessel to -0.1MPa and remove low-boiling substances by vacuum evaporation. Add 6L of toluene to the reaction vessel and stir until the system is dissolved. Add 2L of purified water to the reaction vessel and stir and disperse for 25min. Let it stand and separate the liquids. Wash the organic phase with purified water until neutral and transfer it to a rotary evaporator with a water bath temperature of 85℃. Remove low-boiling substances by vacuum evaporation to obtain composite phenolic resin.

[0057] Weigh out 500g of composite phenolic resin and 1500mL of toluene and add them to the reaction vessel. Stir until the system is dissolved. Add 130g of nano silicon carbide and 140g of nano alumina to the reaction vessel and sonicate for 40min to obtain a composite phenolic resin solution.

[0058] Step 3: Preparation of carbon fiber mesh

[0059] Epoxy-modified carbon fibers are fed into a carding machine, where carding needles disperse and arrange the fibers in parallel. The fibers are then passed through a web-laying machine at a density of 25 g / m². 2 The web-laying density is used to evenly lay the combed epoxy-modified carbon fiber into a carbon fiber web.

[0060] The carbon fiber mesh was heated to 125°C, and then the composite phenolic resin solution was applied at a rate of 35 mL / m. 2 The appropriate amount of atomized spray is applied to both sides of the carbon fiber mesh, and cured for 7 minutes to obtain the carbon fiber mesh.

[0061] Step 4: Preparation of carbon fiber needled felt

[0062] The carbon fiber mesh was stacked in six layers and then placed in a needle punching machine, with a fixed needle punching density of 110 needles / cm. 2 The needles were fixed at a depth of 11.5 mm to obtain a carbon fiber needled felt blank.

[0063] The carbon fiber needle-punched felt blank was transferred to a hot press at 125℃ and 0.4MPa for 13.5 minutes, then transferred to a calcining furnace. Under an argon atmosphere, the temperature was raised to 900℃ and calcined for 70 minutes. The blank was then allowed to cool naturally to room temperature to obtain carbon fiber needle-punched felt.

[0064] Example 3

[0065] This embodiment provides a method for preparing high-strength carbon fiber needled felt, including the following steps:

[0066] Step 1: Preparation of epoxy-modified carbon fibers

[0067] Weigh out 50g of zirconium nitrate and 5L of deionized water and add them to the reaction vessel. Stir until the system is dissolved. Add 250g of PAN-based carbon fiber and 300g of pitch carbon fiber to the reaction vessel and sonicate for 30min. Add 5mol / L sodium hydroxide solution to the reaction vessel to adjust the pH of the system to 8. Lower the temperature of the reaction vessel to room temperature and filter. Wash the filter cake with purified water until neutral and then dry it. Transfer the filter cake to a drying oven at 90℃ and dry it to constant weight to obtain mixed carbon fiber.

[0068] Weigh out 500g of mixed carbon fiber, 160g of KH-560, and 10L of anhydrous ethanol and add them to a reaction vessel. Disperse the mixture ultrasonically for 50min. Raise the temperature of the reaction vessel to 60℃ and add 1L of 3mol / L sodium hydroxide solution. Keep the reaction vessel at this temperature for 80min. Lower the temperature of the reaction vessel to room temperature and filter the mixture. Wash the filter cake with purified water until neutral and then dry it. Transfer the filter cake to a drying oven at 80℃ and dry it to constant weight to obtain epoxy-modified carbon fiber.

[0069] Step 2: Preparation of composite phenolic resin solution

[0070] Weigh out 600g of phenol, 1100mL of 37wt% formaldehyde aqueous solution and 150g of 35wt% sodium hydroxide solution and add them to the reaction vessel. Stir the reaction vessel and raise the temperature to 70℃. Keep the reaction vessel at this temperature for 110min. Raise the temperature to 90℃ and add 110g of phenylboronic acid to the reaction vessel. Keep the reaction vessel at this temperature for 3h. Then, reduce the pressure in the reaction vessel to -0.1MPa and remove low-boiling substances by vacuum evaporation to obtain boron-modified phenolic resin.

[0071] Weigh out 600g of boron-modified phenolic resin and 6L of 1,4-dioxane and add them to a reaction vessel. Stir the reaction vessel to 70℃ and keep it warm while stirring until the system is dissolved. Add 90g of propyltriethoxysilane isocyanate to the reaction vessel and keep it warm for 90min. Add 240g of octamethylcyclotetrasiloxane, 63g of tetraethyl orthosilicate, and 54g of 3-aminopropyltriethoxysilane to the reaction vessel and stir and disperse for 30min. Add 300mL of 60wt% sulfuric acid to the reaction vessel and raise the reaction vessel temperature to 95℃. Keep it warm for 3h. Apply a negative pressure to the reaction vessel to -0.1MPa and remove low-boiling substances by vacuum evaporation. Add 6L of toluene to the reaction vessel and stir until the system is dissolved. Add 2L of purified water to the reaction vessel and stir and disperse for 30min. Let it stand and separate the liquids. Wash the organic phase with purified water until neutral and transfer it to a rotary evaporator with a water bath temperature of 90℃. Remove low-boiling substances by vacuum evaporation to obtain composite phenolic resin.

[0072] Weigh out 500g of composite phenolic resin and 1500mL of toluene and add them to the reaction vessel. Stir until the system is dissolved. Add 140g of nano silicon carbide and 150g of nano alumina to the reaction vessel and sonicate for 50min to obtain a composite phenolic resin solution.

[0073] Step 3: Preparation of carbon fiber mesh

[0074] Epoxy-modified carbon fibers are fed into a carding machine, where carding needles disperse and arrange the fibers in parallel. The fibers are then passed through a web-laying machine at a density of 30 g / m². 2 The web-laying density is used to evenly lay the combed epoxy-modified carbon fiber into a carbon fiber web.

[0075] The carbon fiber mesh was heated to 130℃, and then the composite phenolic resin solution was applied at a rate of 40 mL / m². 2 The appropriate amount of atomized spray is applied to both sides of the carbon fiber mesh, and cured for 8 minutes to obtain the carbon fiber mesh.

[0076] Step 4: Preparation of carbon fiber needled felt

[0077] The carbon fiber mesh was stacked in 7 layers and then placed in a needle punching machine, with a fixed needle punching density of 110 needles / cm. 2 The needle is fixed by needle punching to a depth of 12mm to obtain carbon fiber needled felt blank;

[0078] The carbon fiber needle-punched felt blank is transferred to a hot press at a temperature of 130℃ and a pressure of 0.5MPa and hot-pressed for 15 minutes. Then it is transferred to a calcination furnace and calcined at 1000℃ under an argon atmosphere for 80 minutes. After cooling naturally to room temperature, carbon fiber needle-punched felt is obtained.

[0079] Comparative Example 1

[0080] The difference between this comparative example and Example 3 is that zirconium nitrate was not added during the preparation of the mixed carbon fibers in step one.

[0081] Comparative Example 2

[0082] The difference between this comparative example and Example 3 is that the mixed carbon fiber in step one is used instead of the epoxy-modified carbon fiber in step three.

[0083] Comparative Example 3

[0084] The difference between this comparative example and Example 3 is that, in step two, boron-modified phenolic resin is used instead of composite phenolic resin in the preparation of the composite phenolic resin solution.

[0085] Comparative Example 4

[0086] The difference between this comparative example and Example 3 is that nano-silicon carbide was not added to the composite phenolic resin solution in step two.

[0087] Performance testing:

[0088] The carbon fiber needled felts prepared in Examples 1-3 and Comparative Examples 1-4 were placed in an oxygen-rich environment at 400℃ and subjected to thermal oxidation treatment for 10 hours. The fracture strength, elongation at break and peel force of the carbon fiber needled felt samples before and after thermal oxidation were measured.

[0089] The breaking strength, elongation at break and peel force of the specimens can be determined with reference to the standard FZ / T 25001-2012 "Industrial Felt". The specific test data are shown in Table 1 below.

[0090]

[0091] Data Analysis:

[0092] Comparative analysis of the data in Table 1 above shows that the carbon fiber needled felt prepared by this invention achieves a tensile strength of 57.2 N / cm before thermo-oxidative aging. 2 The elongation at break decreased to 3.0%, the peel force reached 15.7 N, and the fracture strength of the prepared carbon fiber needled felt after thermo-oxidative aging reached 50.9 N / cm. 2 The retention rate reached 89%, the elongation at break decreased to 2.6%, the retention rate reached 87%, the peel force reached 13.7N, and the retention rate reached 87%. All performance test data were better than the comparative example. This shows that the present invention uses PAN-based and pitch-based carbon fibers as raw materials to form a composite, then loads ZrO2 on the fiber surface for needle punching to form a web, and reinforces it with boron-modified organic-inorganic hybrid phenolic resin, nano-silicon carbide and alumina to construct a dense and stable carbon-ceramic composite structure, thereby significantly improving the mechanical strength and heat oxidation resistance of carbon fiber needle-punched felt.

[0093] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing high-strength carbon fiber needled felt, characterized in that, Includes the following steps: S1. Mix zirconium nitrate and deionized water, stir until the system is dissolved, add PAN-based carbon fiber and pitch carbon fiber to the reaction system, ultrasonically disperse for 20-30 min, add sodium hydroxide solution to the reaction system, adjust the pH of the system to 8, and then perform post-treatment to obtain mixed carbon fiber; S2. Epoxy-modified carbon fibers were prepared by surface modification of the mixed carbon fibers using KH-560. Then, the epoxy-modified carbon fiber is fed into a carding machine, where the carding needles disperse and arrange the epoxy-modified carbon fiber in parallel, and the carded epoxy-modified carbon fiber is evenly laid into a carbon fiber mesh by a web laying machine. S3. Spray the composite phenolic resin solution evenly onto both sides of the carbon fiber mesh at a temperature of 120-130℃ in the form of a spray, and cure for 6-8 minutes to obtain the carbon fiber mesh. S4. After stacking several carbon fiber meshes layer by layer, they are needled and fixed to obtain carbon fiber needled felt blanks, and then heat-treated to obtain carbon fiber needled felt.

2. The method for preparing a high-strength carbon fiber needle-punched felt according to claim 1, characterized in that, In step S1, the ratio of zirconium nitrate, deionized water, PAN-based carbon fiber, and pitch carbon fiber is 3-5g:500mL:20-25g:25-30g, and the concentration of the sodium hydroxide solution is 3-5mol / L; in step S2, the web laying density of the carbon fiber mesh is 20-30g / m². 2 In step S3, the spraying volume of the composite phenolic resin solution is 30-40 mL / m³. 2 .

3. The method for preparing a high-strength carbon fiber needle-punched felt according to claim 1, characterized in that, The preparation method of epoxy modified carbon fiber is as follows: Mixed carbon fiber, KH-560 and anhydrous ethanol are mixed and ultrasonically dispersed for 30-50 min. The temperature of the reaction system is raised to 50-60℃. Sodium hydroxide solution is added to the reaction system and the reaction is kept at the temperature for 60-80 min. After post-treatment, epoxy modified carbon fiber is obtained.

4. The method for preparing a high-strength carbon fiber needled felt according to claim 3, characterized in that, The ratio of the mixed carbon fiber, KH-560, anhydrous ethanol and sodium hydroxide solution is 10g:2.6-3.2g:200mL:20mL, and the concentration of the sodium hydroxide solution is 2-3mol / L.

5. The method for preparing a high-strength carbon fiber needle-punched felt according to claim 1, characterized in that, In step S3, the method for preparing the composite phenolic resin solution is as follows: the composite phenolic resin and toluene are mixed and stirred until the system is dissolved, nano-silicon carbide and nano-alumina are added to the reaction system, and ultrasonically dispersed for 30-50 min to obtain the composite phenolic resin solution. The ratio of the amount of the composite phenolic resin, toluene, nano-silicon carbide and nano-alumina is 5g:15mL:1.2-1.4g:1.3-1.5g.

6. The method for preparing a high-strength carbon fiber needled felt according to claim 5, characterized in that, The composite phenolic resin is obtained by the following steps: A1. Mix phenol, formaldehyde solution and alkaline solution, raise the temperature of the reaction system to 60-70℃, keep the reaction at this temperature for 90-110 min, raise the temperature of the reaction system to 80-90℃, add phenylboronic acid to the reaction system, keep the reaction at this temperature for 2-3 h, and then perform post-treatment to obtain boron-modified phenolic resin. A2. Mix boron-modified phenolic resin and 1,4-dioxane. Raise the temperature of the reaction system to 60-70℃ and stir until the system dissolves. Add propyltriethoxysilane isocyanate to the reaction system and keep it at the temperature for 70-90 min. Add octamethylcyclotetrasiloxane, tetraethyl orthosilicate, and 3-aminopropyltriethoxysilane to the reaction system and stir to disperse for 20-30 min. Add a catalyst to the reaction system and raise the temperature of the reaction system to 85-95℃. Keep it at the temperature for 2-3 h. After post-treatment, obtain composite phenolic resin.

7. The method for preparing a high-strength carbon fiber needled felt according to claim 6, characterized in that, In step A1, the ratio of phenol, formaldehyde solution, alkaline solution and phenylboronic acid is 5-6g:9-11mL:1.5g:0.9-1.1g, and the formaldehyde solution is a 35-37wt% aqueous formaldehyde solution.

8. The method for preparing a high-strength carbon fiber needled felt according to claim 6, characterized in that, In step A2, the ratio of boron-modified phenolic resin, 1,4-dioxane, propyltriethoxysilane isocyanate, octamethylcyclotetrasiloxane, tetraethyl orthosilicate, 3-aminopropyltriethoxysilane, and catalyst is 20g:200mL:2-3g:6-8g:1.9-2.1g:1.6-1.8g:10mL, and the catalyst is 50-60wt% sulfuric acid.

9. The method for preparing a high-strength carbon fiber needle-punched felt according to claim 1, characterized in that, In step S4, the carbon fiber mesh has 5-7 layers, a needle-punching density of 110 needles / cm2, and a needle-punching depth of 11-12mm. The heat treatment method is as follows: the carbon fiber needle-punched felt blank is transferred to a hot press at a temperature of 120-130℃ and a pressure of 0.3-0.5MPa, and hot-pressed for 12-15 minutes. Then it is transferred to a calcining furnace, and under an argon atmosphere, the temperature is raised to 800-1000℃ and calcined for 60-80 minutes. It is then naturally cooled to room temperature to obtain carbon fiber needle-punched felt.

10. A high-strength carbon fiber needle-punched felt, characterized in that, It is obtained by processing using the preparation method of a high-strength carbon fiber needled felt as described in any one of claims 1-9.

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