Method for improving binding rate of aerogel and fiber reinforced material

Abstract

The invention discloses a method for improving the binding rate of aerogel and a fiber reinforced material, which comprises the following steps: pretreating the surface of the fiber reinforced material, including chemical activation and modification with a coupling agent; an aerogel precursor solution is optimized, wherein compatibility components are introduced, and sol-gel parameters are regulated and controlled; the composite process is innovated and comprises layer-by-layer assembly, in-situ sol-gel and freeze-drying optimization; post-treatment strengthening, including high-temperature heat treatment and surface coating protection; through the steps of specific fiber surface pretreatment, aerogel precursor solution optimization, innovation of a composite process, post-treatment reinforcement and the like, the binding rate of aerogel and a fiber reinforced material is increased, so that the mechanical property of the composite material is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of aerogel preparation technology, and particularly relates to a method for improving the bonding rate of aerogel and fiber reinforcement material. Background Art

[0002] Silica aerogel, a material with high porosity, low density, extremely low thermal conductivity, and excellent adsorption properties, is widely used in thermal protection applications in various fields, including spacecraft, petrochemical pipelines, and new energy vehicle battery cells. Aerogel monomers are brittle and have poor mechanical properties. Combining aerogel with fiber-reinforced materials can significantly improve their mechanical properties during application. However, when combined with fiber-reinforced materials, silica aerogel often suffers from uneven bonding, weak bonding, powder loss, and poor mechanical properties, limiting its comprehensive application as a composite material. Summary of the Invention

[0003] In view of the above problems, the object of the present invention is to provide a method for improving the bonding rate between aerogel and fiber reinforcement material and enhancing the mechanical properties of the composite material.

[0004] The present invention is achieved through the following technical solutions: A method for improving the bonding rate of aerogel and fiber reinforcement material comprises the following steps: Step a, pretreatment of the fiber reinforcement surface: etching the fiber reinforcement surface with an oxidant or alkaline solution, impregnating the etched fiber reinforcement with a silane coupling agent solution, and introducing amino or epoxy groups on the fiber reinforcement surface through a hydrolysis condensation reaction; Step b, aerogel precursor solution optimization: adding a component that reacts with the functional groups on the surface of the fiber reinforcement material to the aerogel precursor solution to promote the co-polycondensation reaction; using an acidic solution to adjust the hydrolysis conditions, using an alkaline solution to adjust the polycondensation conditions, adjusting the solvent ratio and catalyst concentration, and controlling the gelation time to match the fiber impregnation; Step c, compounding the aerogel precursor solution with the fiber reinforcement material: the fiber reinforcement material is alternately immersed in the aerogel precursor solution and the curing agent, a gradient interface layer is constructed through multiple cycles, and then immersed in the aerogel precursor solution for gelation. During the gelation process, ultrasound or vacuum assistance is applied to force the aerogel precursor solution to penetrate into the gaps of the fiber reinforcement material, reduce the porosity, and form an interpenetrating network structure; finally, directional freezing is used to control the growth direction of the ice crystals so that the pores of the aerogel precursor solution are arranged along the axial direction of the fiber reinforcement material to reduce the compressive stress.

[0005] Step d, post-treatment strengthening: annealing at 300-600°C in an inert atmosphere to eliminate residual organic matter on the interface and promote chemical bonding between the fiber reinforcement material and the aerogel precursor solution; depositing a hydrophobic coating after compounding to reduce damage to the interface caused by ambient humidity.

[0006] The fiber reinforcement material described in step a is carbon fiber or glass fiber; the oxidant described in step a is nitric acid or ozone; the alkaline solution described in step a is NaOH solution; and the silane coupling agent solution described in step a is KH550 or KH560.

[0007] The aerogel precursor solution in step b is tetraethyl orthosilicate; the acidic solution in step b is hydrochloric acid or nitric acid; and the alkaline solution in step b is ammonium phosphate, sodium hydroxide, or sodium bicarbonate.

[0008] The directional freezing in step c is liquid nitrogen gradient freezing.

[0009] The deposited hydrophobic coating in step d is hexamethyldisilazane.

[0010] Beneficial effects of the present invention: The present invention improves the bonding rate of aerogel and fiber-reinforced materials through steps such as specific fiber surface pretreatment, aerogel precursor solution optimization, innovative composite technology, and post-processing reinforcement, thereby significantly improving the mechanical properties of the composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention will be further described in detail below with reference to the accompanying drawings.

[0012] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0013] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0014] It should be noted that the structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions for the implementation of the present invention. Therefore, they have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the efficacy and purpose of the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle", etc. quoted in this specification are only for the convenience of description and are not used to limit the scope of the implementation of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0015] In the description of the present invention, it should be noted that, unless otherwise expressly specified and limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. It should be noted that the terms "include", "comprise" or any other variants are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also includes elements that are inherent to such process, method, article or device. Example 1

[0016] Step a: Surface pretreatment of the glass fiber reinforced material: Step 1: Soak the glass fiber reinforced material in ethanol to remove surface grease; Step 2: Soak the degreased glass fiber material in 5% HNO3 for 30 minutes; Step 3: Rinse the HNO3-treated glass fiber reinforced material with deionized water until it is neutral; Step 4: Dry the rinsed neutral glass fiber reinforced material at 80°C; Step 5: Soak the dried glass fiber reinforced material in KH550 silane coupling agent for 30 minutes, and then dry it under N2 protection at 100°C for 1 hour, thereby finally obtaining a surface-pretreated glass fiber reinforced material.

[0017] Step b: Optimization of aerogel precursor solution: TEOS: water: methanol: KH550 were mixed in a molar ratio of 1:4:6:0.2, the pH was adjusted to 2-4 with 0.01 M hydrochloric acid, and then maintained at 50-60° C. for 2-4 h to allow for full hydrolysis.

[0018] Step c: Composite aerogel and glass fiber reinforced material: Step 1: Immerse the surface pretreated glass fiber reinforced material in an aerogel precursor solution and keep it at 50°C to 60°C for 2 hours; Step 2: Immerse the material obtained in the first step in hexamethyldisilazane and keep it at 50°C to 60°C for 2 hours; Step 3: Alternately immerse in the aerogel precursor solution and hexamethyldisilazane 4 times, and after multiple cycles, obtain a glass fiber reinforced material with a gradient interface layer; Step 4: Immerse the glass fiber reinforced material with a gradient interface layer The material is immersed in an aerogel precursor solution at 50°C~60°C, and a 0.5M ammonia solution is added to adjust the pH to 8~10. Then, it is subjected to ultrasonic treatment to gel to obtain an aerogel glass fiber reinforced composite wet gel material; in the fifth step, the obtained wet gel material is frozen for 1 hour at room temperature~-20°C in the first stage; frozen for 2 hours at -20°C~-80°C in the second stage; and directly immersed in liquid nitrogen for 2 hours at -80°C~-196°C in the third stage to obtain an aerogel~glass fiber reinforced composite material.

[0019] Step d: Post-treatment strengthening: The obtained aerogel glass fiber reinforced composite material is placed in an inert atmosphere for annealing at 400°C to eliminate residual organic matter on the surface; the annealed aerogel glass fiber reinforced composite material is immersed in a mixed solution of hexamethyldisilazane:n-hexane with a volume ratio of 1:10 for 15 hours, then rinsed with ethanol three times, and dried at 70°C for 6 hours to finally obtain an aerogel glass fiber reinforced composite material with excellent mechanical properties. Example 2

[0020] Step a: Surface pretreatment of carbon fiber reinforced materials: First, ultrasonically clean the carbon fiber reinforced materials with acetone for 10 minutes to remove surface grease. Second, immerse the degreased carbon fiber reinforced materials in a 5% NaOH solution and heat in an 80°C water bath for 1 hour. Third, rinse the NaOH-treated carbon fiber reinforced materials with 1% dilute hydrochloric acid until neutral. Fourth, vacuum dry the neutralized carbon fiber reinforced materials at 100°C for 2 hours. Fifth, immerse the dried carbon fiber reinforced materials in KH560 silane coupling agent under ultrasonic conditions for 30 minutes, and then dry them at 90°C under nitrogen protection for 1.5 hours. Finally, a surface-pretreated carbon fiber reinforced material is obtained.

[0021] Step b: Optimization of aerogel precursor solution: TEOS: water: methanol: KH560 were mixed in a molar ratio of 1:6:8:0.3, the pH was adjusted to 2-4 with 0.05 M HNO3, and then maintained at 50-60°C for 2-4 hours to allow for full hydrolysis.

[0022] Step c aerogel and carbon fiber reinforced material composite: the first step is to immerse the surface pretreated carbon fiber reinforced material in an aerogel precursor solution and keep it at 50~60℃ for 2h; the second step is to immerse the material obtained in the first step in trimethylchlorosilane and keep it at 50℃~60℃ for 2h; the third step is to alternately immerse in the aerogel precursor solution and trimethylchlorosilane 6 times, and after multiple cycles, obtain a carbon fiber reinforced material with a gradient interface layer; the fourth step is to immerse the carbon fiber material with a gradient interface layer in an aerogel precursor solution at 50℃~60℃, add 1M ammonia solution to adjust the pH to 8~10, and perform ultrasonic treatment to gel it to obtain an aerogel carbon fiber reinforced composite wet gel material; the fifth step is to freeze the obtained wet gel material at room temperature~-20℃ for 2h in the first stage; freeze it at -20℃~-80℃ for 3h in the second stage; and directly soak it in liquid nitrogen at -80℃~-196℃ for 3h in the third stage to obtain an aerogel carbon fiber reinforced composite material.

[0023] Step d: Post-treatment strengthening of aerogel carbon fiber reinforced composite materials: the obtained aerogel carbon fiber reinforced composite materials are placed in an inert atmosphere for annealing at 600°C to eliminate residual organic matter on the surface; the annealed aerogel carbon fiber reinforced composite materials are immersed in a mixed solution of trimethylchlorosilane:n-hexane with a volume ratio of 1:9 for 12 hours, and then rinsed with n-hexane twice, and dried at 70°C for 6 hours to finally obtain an aerogel carbon fiber reinforced composite material with excellent mechanical properties.

[0024] Comparative Example 1: (1) Preparation of aerogel precursor solution: Ethyl orthosilicate: water: methanol: methyltrimethoxysilane were mixed in a molar ratio of 1:4:6:0.3, 0.1 M hydrochloric acid was added to adjust the pH to 2-4, and then kept at 50-60 °C for 4-6 h to allow it to be fully hydrolyzed.

[0025] (2) Composite of aerogel and glass fiber reinforced material: The glass fiber reinforced material was immersed in the aerogel precursor solution, and a 1M ammonia solution was added at 50-60°C to adjust the pH to 8-10. The gel was allowed to stand to obtain an aerogel-glass fiber reinforced composite wet gel material. The obtained wet gel material was immersed in a methanol solution for 4 hours to perform solvent replacement, and then supercritical drying was performed at 55-60°C and 14MPa for 4 hours to obtain an aerogel glass fiber reinforced composite material.

[0026] Comparative Example 2: (1) Preparation of aerogel precursor solution: Mix ethyl orthosilicate, water, and methanol in a molar ratio of 1:6:8, add 0.1 M hydrochloric acid to adjust the pH to 2-4, and then keep it at 50-60 °C for 4-6 hours to allow it to be fully hydrolyzed.

[0027] (2) Composite of aerogel and carbon fiber reinforced material: The carbon fiber reinforced material was immersed in the aerogel precursor solution, and a 1M ammonia solution was added at 50-60°C. The gel was allowed to stand to obtain an aerogel-carbon fiber reinforced composite wet gel material. The obtained wet gel material was immersed in a methanol solution for 6 hours for solvent replacement, and then placed in hexamethyldisilazane for 4 hours for hydrophobic modification. It was then supercritically dried at 55-60°C and 14MPa for 6 hours to obtain an aerogel carbon fiber reinforced composite material.

[0028] Table 1 is the comparison of thermal conductivity (25℃)

[0029] Table 1 From Table 1, it can be seen that the thermal conductivity coefficients of Example 1 (0.02034 W / (m・K)) and Example 2 (0.02116 W / (m・K)) are both lower than those of Comparative Example 1 (0.02425 W / (m・K)) and Comparative Example 2 (0.02357 W / (m・K)), indicating that the materials of the examples have better thermal conductivity at 25°C and relatively slower heat transfer.

[0030] Table 2 is the comparison of shear strength (25℃)

[0031] Table 2 The shear strengths of Example 1 (0.86 MPa) and Example 2 (1.21 MPa) are much higher than those of Comparative Example 1 (0.37 MPa) and Comparative Example 2 (0.65 MPa), indicating that the materials of Examples 1 and 2 have stronger ability to resist shear deformation at 25°C and better mechanical properties.

[0032] In general, compared with the comparative example, the process method adopted by the present invention, Examples 1 and 2, in an environment of 25°C, has both lower thermal conductivity (beneficial for scenarios such as thermal insulation) and higher shear strength (to ensure structural mechanical properties), and has better comprehensive performance. In application scenarios with requirements for thermal conductivity and mechanical properties, the materials related to the embodiments may perform better.

[0033] The protection scope of the present invention is not limited to the technical solutions disclosed in the specific implementation methods. Any modifications, equivalent replacements, improvements, etc. made to the above embodiments based on the technical essence of the present invention fall within the protection scope of the present invention.

Claims

1. A method for improving the bonding rate of aerogel and fiber reinforcement material, characterized by: The following steps are involved: Step a, pretreatment of the fiber reinforcement surface: etching the fiber reinforcement surface with an oxidant or alkaline solution, impregnating the etched fiber reinforcement with a silane coupling agent solution, and introducing amino or epoxy groups on the fiber reinforcement surface through a hydrolysis condensation reaction; Step b, aerogel precursor solution optimization: adding a component that reacts with the functional groups on the surface of the fiber reinforcement material to the aerogel precursor solution to promote the co-polycondensation reaction; using an acidic solution to adjust the hydrolysis conditions, using an alkaline solution to adjust the polycondensation conditions, adjusting the solvent ratio and catalyst concentration, and controlling the gelation time to match the fiber impregnation; Step c, compounding the aerogel precursor solution with the fiber reinforcement material: the fiber reinforcement material is alternately immersed in the aerogel precursor solution and the curing agent, a gradient interface layer is constructed through multiple cycles, and then immersed in the aerogel precursor solution for gelation. During the gelation process, ultrasound or vacuum assistance is applied to force the aerogel precursor solution to penetrate the gaps between the fiber reinforcement material, reducing the porosity and forming an interpenetrating network structure; finally, directional freezing is used to control the growth direction of ice crystals so that the pores of the aerogel precursor solution are arranged along the axial direction of the fiber reinforcement material, thereby reducing the compressive stress; Step d, post-treatment strengthening: annealing at 300-600°C in an inert atmosphere to eliminate residual organic matter on the interface and promote chemical bonding between the fiber reinforcement material and the aerogel precursor solution; depositing a hydrophobic coating after compounding to reduce damage to the interface caused by ambient humidity.

2. The method for improving the bonding rate between aerogel and fiber-reinforced materials according to claim 1, characterized in that: The fiber reinforcement material described in step a is carbon fiber or glass fiber; the oxidant described in step a is nitric acid or ozone; the alkaline solution described in step a is NaOH solution; and the silane coupling agent solution described in step a is KH550 or KH560.

3. The method for improving the bonding rate of aerogel and fiber-reinforced materials according to claim 1, characterized in that: The aerogel precursor solution in step b is tetraethyl orthosilicate; the acidic solution in step b is hydrochloric acid or nitric acid; and the alkaline solution in step b is ammonium phosphate, sodium hydroxide, or sodium bicarbonate.

4. The method for improving the bonding rate of aerogel and fiber-reinforced materials according to claim 1, characterized in that: The directional freezing in step c is liquid nitrogen gradient freezing.

5. The method for improving the bonding rate of aerogel and fiber-reinforced materials according to claim 1, characterized in that: The deposited hydrophobic coating in step d is hexamethyldisilazane.

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