A fibrous felt composite material, its production and use

Abstract

The present application relates to the technical field of fiber felt, and proposes a fiber felt composite material, a preparation method and application thereof.The preparation method of the fiber felt composite material comprises the following steps: dipping the fiber felt in a gel precursor solution, aging, solvent replacement, drying, and obtaining the fiber felt composite material; the preparation method of the gel precursor solution comprises the following steps: A1, mixing a silicon source, a silk fibroin solution, inorganic short fibers, a surfactant and a solvent to obtain a preliminary mixture; A2, after mixing the preliminary mixture with an acid solution, adding an alkali solution for continuous mixing to obtain the gel precursor solution.Through the above technical solution, the problem of poor strength of the fiber felt composite material in the related art is solved.

Description

Technical Field

[0001] This invention relates to the field of fiber felt technology, specifically to a fiber felt composite material, its preparation method, and its application. Background Technology

[0002] Currently, PP (polypropylene) blow-molded air ducts are the mainstream manufacturing solution for air duct systems. They are integrally formed using a blow molding process, offering advantages such as mature technology and low cost. However, with the increasing demand for lightweight, quiet, and multifunctional high-end equipment, the shortcomings of PP blow-molded air ducts are becoming increasingly apparent:

[0003] (1) Limitations of molding process: blow molding molds are expensive. After the product is formed, the end face needs to be cut off by cutting equipment. There are uneven wall thicknesses and low structural strength. It is difficult to achieve high strength in thin-walled structures. The wall thickness needs to be increased or reinforcing ribs need to be added, which leads to an increase in weight. Complex curved surfaces (such as variable cross-section curves and multi-branch structures) need to be blow molded in sections and then spliced ​​again. The splice is prone to air leakage. It may also be necessary to control condensation through secondary processes such as bonding foam, which not only increases costs but may also affect the air quality inside the vehicle due to the volatilization of adhesives. It is impossible to integrate functional structures (such as soundproof holes and heat insulation layers). Additional components or processing are required later, which increases assembly costs.

[0004] (2) Insufficient sound insulation performance: The sound absorption coefficient of PP material alone for mid-to-high frequency noise (1000~4000Hz) is only 0.5~0.6, requiring additional sound insulation cotton to be pasted. Pasting sound insulation cotton relies on adhesives, which are prone to falling off (peel strength <5N / cm) and have excessive volatile matter (TVOC>50μg / m³). 3 Problems such as these increase both weight and cost.

[0005] (3) High temperature environment limitation: PP material is usually used at temperatures below 120℃ for a long time. It is easy to deform in high temperature scenarios (such as car engine compartment). The thermal conductivity of PP is 0.22W / (m•K), which can easily lead to energy loss of hot and cold air in car air conditioning ducts and affect energy efficiency.

[0006] In existing technologies, some solutions attempt to use modified PP or composite materials, but these fail to overcome the inherent defects of the materials. The few ducts using fiber materials are mostly layered and bonded, which can overcome some of the aforementioned problems (such as sound insulation), but still suffer from low strength. Therefore, a fiber-felt composite material that balances lightweight and high strength is needed. Summary of the Invention

[0007] This invention proposes a fiber-felt composite material, its preparation method, and its application, which solves the problem of low strength of fiber-felt composite materials in related technologies.

[0008] The technical solution of the present invention is as follows:

[0009] This invention proposes a method for preparing fiber-felt composite materials, comprising the following steps:

[0010] The fiber felt was impregnated in a gel precursor solution, aged, solvent replaced, and dried to obtain a fiber felt composite material.

[0011] The preparation method of the gel precursor solution includes the following steps:

[0012] A1. Mix the silicon source, silk fibroin solution, inorganic short-cut fibers, surfactant and solvent to obtain a preliminary mixture;

[0013] A2. After adding acid to the initial mixture and mixing, add alkali and continue mixing to obtain the gel precursor solution.

[0014] As a further technical solution, the silicon source includes one or more of methyltrimethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, and 2,5-divinyltrimethoxysilanethiophene;

[0015] The surfactant includes one or both of sodium dodecylbenzenesulfonate and hexadecyltrimethylammonium bromide.

[0016] As a further technical solution, the mass ratio of the silicon source to the surfactant is 1:0.1~0.3, for example, it can be 1:0.1, 1:0.15, 1:0.2, 1:0.22, 1:0.25, 1:0.28, or 1:0.3;

[0017] The solvent includes a mixture of ethanol and water;

[0018] The molar ratio of the silicon source, ethanol, and water is 1:5:12~16.

[0019] As a further technical solution, the mass ratio of the silicon source, silk fibroin solution and inorganic chopped fibers is 10:2:0.5~2, for example, it can be 10:2:0.5, 10:2:1, 10:2:1.2, 10:2:1.5, 10:2:1.8, or 10:2:2.

[0020] As a further technical solution, the mass ratio of the silicon source, acid solution, and alkaline solution is 1:0.5:0.4~0.6;

[0021] The concentration of the acid solution is 0.1~0.2 mol / L, and the concentration of the alkali solution is 2~2.5 mol / L.

[0022] As a further technical solution, when the silicon source is dimethyldiethoxysilane and 2,5-divinyltrimethoxysilanethiophene, the mass ratio of dimethyldiethoxysilane to 2,5-divinyltrimethoxysilanethiophene is 5:1~2.

[0023] In this invention, dimethyldiethoxysilane and 2,5-divinyltrimethoxysilanethiophene are used as silicon sources to prepare fiber-felt composite materials, which improves the thermal insulation performance of the fiber-felt composite materials. This is because, during the preparation of the fiber-felt composite materials, dimethyldiethoxysilane undergoes hydrolysis and condensation to form a porous siloxane network. The air in the pores effectively hinders heat conduction, while the dimethyl group stabilizes the network structure and enhances the thermal insulation effect. 2,5-divinyltrimethoxysilanethiophene not only participates in the network construction, but its conjugated thiophene ring system absorbs and scatters infrared radiation, reducing heat radiation transfer. The synergistic effect of these two components forms a comprehensive thermal insulation system covering both heat conduction and heat radiation, thus improving the thermal insulation performance of the fiber-felt composite materials.

[0024] As a further technical solution, the length of the inorganic chopped fiber is 0.5~0.8mm and the diameter is 10~15μm;

[0025] The inorganic chopped fibers include one or both of carbon fiber and basalt fiber.

[0026] As a further technical solution, the fiber felt is made of 80%~95% high-temperature resistant fiber and 5%~20% low-melting-point fiber by needle punching, by weight percentage.

[0027] As a further technical solution, the high-temperature resistant fiber includes one or two of PET fiber and basalt fiber.

[0028] PET fiber, or polyethylene terephthalate fiber, has a molecular chain composed of benzene rings and aliphatic segments. It has a high melting point and maintains good morphological stability at relatively high temperatures. Simultaneously, its chemical structure is relatively stable, and it is not prone to thermal decomposition or oxidation within a certain temperature range, exhibiting excellent high-temperature resistance. Basalt fiber is made from natural basalt ore through high-temperature melting and drawing. It is mainly composed of various oxides such as silicon dioxide, alumina, and calcium oxide, forming a stable glassy structure. This gives basalt fiber not only excellent high-temperature resistance but also high strength, high modulus, and good chemical stability. Other high-temperature resistant fibers include aramid fiber, aluminosilicate fiber, and mullite fiber.

[0029] As a further technical solution, the melting point of the low-melting-point fiber is 110~130℃.

[0030] The present invention also proposes a fiber felt composite material, which is prepared by the aforementioned preparation method.

[0031] The present invention also proposes the application of the fiber felt composite material prepared by the above preparation method in ventilation systems.

[0032] In this invention, the ventilation system can be, for example, a car air conditioning duct, a building ventilation duct, or an electronic device heat dissipation duct, which are ventilation systems that require sound insulation, lightweight design, and environmental protection.

[0033] The working principle and beneficial effects of this invention are as follows:

[0034] In this invention, the addition of silk fibroin solution and inorganic chopped fibers to the gel precursor solution significantly improves the strength of the fiber-felt composite material. During the preparation process, the polar groups in the molecular structure of silk fibroin allow it to tightly bind with the silicon source hydrolysis products and inorganic chopped fibers, not only enhancing the connection between the components within the material but also absorbing energy under stress through its flexibility. The high strength and rigidity of the inorganic chopped fibers provide skeletal support, effectively preventing crack propagation and ensuring the material is not easily deformed under stress. The two work synergistically: silk fibroin promotes the uniform dispersion of inorganic chopped fibers and enhances their bonding with the inorganic network, while the inorganic chopped fibers limit excessive deformation of the silk fibroin network, maintaining the material's rigidity, thus synergistically improving the strength of the fiber-felt composite material. Attached Figure Description

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0036] Figure 1 This is a schematic diagram of an air duct structure used in an application example of the present invention;

[0037] Figure 2 This is a schematic diagram of the upper and lower air duct structures in an application example of the present invention;

[0038] Figure 3 This is a schematic diagram of the air duct cavity structure as an application example of the present invention;

[0039] Figure 4 This is a schematic diagram of a fiber-felt composite material used in the present invention.

[0040] Figure 5 This is a schematic diagram of the air duct assembly containing fiber felt composite material, an application example of the present invention;

[0041] Figure 6 This is a schematic diagram of an air duct structure containing fiber felt composite material, which is an application example of the present invention.

[0042] In the diagram: 100 - air duct shell, 101 - upper air duct shell, 102 - lower air duct shell, 103 - welding flange, 104 - upper air duct shell mold cavity, 105 - lower air duct shell mold cavity, 106 - fiber felt composite material, 107 - upper air duct shell tooling, 108 - lower air duct shell tooling. Detailed Implementation

[0043] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0044] In the following examples and comparative examples, the preparation method of the silk fibroin solution includes the following steps: mixing silk fibroin and a ternary mixed solvent of calcium chloride-ethanol-water (the molar ratio of calcium chloride, ethanol and water is 1:2:8) at 90°C for 1.5 h, and then dialyzing the mixture in a dialysis bag with a molecular weight cutoff of 8000 Da for 6 h to obtain the silk fibroin solution; the mass-volume ratio of silk fibroin and the ternary mixed solvent of calcium chloride-ethanol-water is 1 g:8 mL.

[0045] Example 1

[0046] The preparation method of fiber-felt composite material includes the following steps:

[0047] A1. Dimethyldiethoxysilane, silk fibroin solution, carbon fiber (0.5 mm in length and 10 μm in diameter), hexadecyltrimethylammonium bromide, and solvent are mixed to obtain a preliminary mixture; the mass ratio of dimethyldiethoxysilane to hexadecyltrimethylammonium bromide is 1:0.1, the solvent is a mixture of ethanol and water, the molar ratio of dimethyldiethoxysilane, ethanol, and water is 1:5:12, and the mass ratio of dimethyldiethoxysilane, silk fibroin solution, and carbon fiber is 10:2:0.5.

[0048] A2. After adding hydrochloric acid solution to the initial mixture and mixing, add sodium hydroxide solution and continue mixing to obtain a gel precursor solution; the mass ratio of dimethyldiethoxysilane, hydrochloric acid solution (concentration of 0.1 mol / L), and sodium hydroxide solution (concentration of 2 mol / L) is 1:0.5:0.4.

[0049] A3. The fiber felt is immersed in the gel precursor solution and aged. The aged gel is then replaced with anhydrous ethanol and sealed. It is then placed in a 50°C oven and replaced every 12 hours for a total of two times. After drying, the fiber felt composite material is obtained. By mass percentage, the fiber felt is made of 80% PET fiber and 20% low melting point fiber (polyethylene fiber) through a needle punching process, with a linear density of 1.8 dtex and a felt thickness of 10 mm.

[0050] Example 2

[0051] The preparation method of fiber-felt composite material includes the following steps:

[0052] A1. Dimethyldiethoxysilane, silk fibroin solution, carbon fiber (0.8 mm in length and 10 μm in diameter), hexadecyltrimethylammonium bromide, and solvent are mixed to obtain a preliminary mixture; the mass ratio of dimethyldiethoxysilane to hexadecyltrimethylammonium bromide is 1:0.3, the solvent is a mixture of ethanol and water, the molar ratio of dimethyldiethoxysilane, ethanol, and water is 1:5:16, and the mass ratio of dimethyldiethoxysilane, silk fibroin solution, and carbon fiber is 10:2:2;

[0053] A2. After adding hydrochloric acid solution to the initial mixture and mixing, add sodium hydroxide solution and continue mixing to obtain a gel precursor solution; the mass ratio of dimethyldiethoxysilane, hydrochloric acid solution (concentration of 0.2 mol / L), and sodium hydroxide solution (concentration of 2.5 mol / L) is 1:0.5:0.6.

[0054] A3. The fiber felt is immersed in the gel precursor solution and aged. The aged gel is then replaced with anhydrous ethanol and sealed. It is then placed in a 50°C oven and replaced every 12 hours for a total of two times. After drying, the fiber felt composite material is obtained. By mass percentage, the fiber felt is made of 95% PET fiber and 5% low-melting-point fiber (polyethylene fiber) through a needle punching process, with a linear density of 1.8 dtex and a felt thickness of 10 mm.

[0055] Example 3

[0056] The preparation method of fiber-felt composite material includes the following steps:

[0057] A1. Dimethyldiethoxysilane, silk fibroin solution, carbon fiber (0.5 mm in length and 10 μm in diameter), hexadecyltrimethylammonium bromide, and solvent are mixed to obtain a preliminary mixture; the mass ratio of dimethyldiethoxysilane to hexadecyltrimethylammonium bromide is 1:0.2, the solvent is a mixture of ethanol and water, the molar ratio of dimethyldiethoxysilane, ethanol, and water is 1:5:14, and the mass ratio of dimethyldiethoxysilane, silk fibroin solution, and carbon fiber is 10:2:1.

[0058] A2. After adding hydrochloric acid solution to the initial mixture and mixing, add sodium hydroxide solution and continue mixing to obtain a gel precursor solution; the mass ratio of dimethyldiethoxysilane, hydrochloric acid solution (concentration of 0.15 mol / L), and sodium hydroxide solution (concentration of 2.5 mol / L) is 1:0.5:0.5.

[0059] A3. The fiber felt is immersed in the gel precursor solution and aged. The aged gel is then replaced with anhydrous ethanol and sealed. It is then placed in a 50°C oven and replaced every 12 hours for a total of two times. After drying, the fiber felt composite material is obtained. By mass percentage, the fiber felt is made of 90% PET fiber and 10% low-melting-point fiber (polyethylene fiber) through a needle punching process, with a linear density of 1.8 dtex and a felt thickness of 10 mm.

[0060] Example 4

[0061] The only difference between this embodiment and Example 3 is that dimethyldiethoxysilane is replaced with 2,5-divinyltrimethoxysilanethiophene.

[0062] Example 5

[0063] The only difference between this embodiment and Example 3 is that dimethyldiethoxysilane is replaced with a composite silicon source, which is a mixture of dimethyldiethoxysilane and 2,5-divinyltrimethoxysilanethiophene in a mass ratio of 5:1.

[0064] Example 6

[0065] The only difference between this embodiment and Embodiment 3 is that dimethyldiethoxysilane is replaced with a composite silicon source, which is a mixture of dimethyldiethoxysilane and methyltrimethoxysilane in a mass ratio of 5:1.

[0066] Example 7

[0067] The only difference between this embodiment and Example 3 is that dimethyldiethoxysilane is replaced with a composite silicon source, which is a mixture of dimethyldiethoxysilane and phenyltriethoxysilane in a mass ratio of 5:1.

[0068] Example 8

[0069] The difference between this embodiment and Example 3 is that dimethyldiethoxysilane is replaced with a composite silicon source, which is a mixture of dimethyldiethoxysilane and 2,5-divinyltrimethoxysilanethiophene in a mass ratio of 5:2.

[0070] Comparative Example 1

[0071] The preparation method of fiber-felt composite material includes the following steps:

[0072] A1. Dimethyldiethoxysilane, carbon fibers (0.5 mm in length and 10 μm in diameter), hexadecyltrimethylammonium bromide, and a solvent are mixed to obtain a preliminary mixture; the mass ratio of dimethyldiethoxysilane to hexadecyltrimethylammonium bromide is 1:0.2, the solvent is a mixture of ethanol and water, the molar ratio of dimethyldiethoxysilane, ethanol, and water is 1:5:14, and the mass ratio of dimethyldiethoxysilane to carbon fibers is 10:3;

[0073] A2. After adding hydrochloric acid solution to the initial mixture and mixing, add sodium hydroxide solution and continue mixing to obtain a gel precursor solution; the mass ratio of dimethyldiethoxysilane, hydrochloric acid solution (concentration of 0.15 mol / L), and sodium hydroxide solution (concentration of 2.5 mol / L) is 1:0.5:0.5.

[0074] A3. The fiber felt is immersed in the gel precursor solution and aged. The aged gel is then replaced with anhydrous ethanol and sealed. It is then placed in a 50°C oven and replaced every 12 hours for a total of two times. After drying, the fiber felt composite material is obtained. By mass percentage, the fiber felt is made of 90% PET fiber and 10% low-melting-point fiber (polyethylene fiber) through a needle punching process, with a linear density of 1.8 dtex and a felt thickness of 10 mm.

[0075] Comparative Example 2

[0076] The preparation method of fiber-felt composite material includes the following steps:

[0077] A1. Dimethyldiethoxysilane, silk fibroin solution, hexadecyltrimethylammonium bromide, and solvent are mixed to obtain a preliminary mixture; the mass ratio of dimethyldiethoxysilane to hexadecyltrimethylammonium bromide is 1:0.2, the solvent is a mixture of ethanol and water, the molar ratio of dimethyldiethoxysilane, ethanol, and water is 1:5:14, and the mass ratio of dimethyldiethoxysilane to silk fibroin solution is 10:3;

[0078] A2. After adding hydrochloric acid solution to the initial mixture and mixing, add sodium hydroxide solution and continue mixing to obtain a gel precursor solution; the mass ratio of dimethyldiethoxysilane, hydrochloric acid solution (concentration of 0.15 mol / L), and sodium hydroxide solution (concentration of 2.5 mol / L) is 1:0.5:0.5.

[0079] A3. The fiber felt is immersed in the gel precursor solution and aged. The aged gel is then replaced with anhydrous ethanol and sealed. It is then placed in a 50°C oven and replaced every 12 hours for a total of two times. After drying, the fiber felt composite material is obtained. By mass percentage, the fiber felt is made of 90% PET fiber and 10% low-melting-point fiber (polyethylene fiber) through a needle punching process, with a linear density of 1.8 dtex and a felt thickness of 10 mm.

[0080] Experimental Example 1

[0081] The tensile strength of the fiber-felt composite materials prepared in Examples 1-8 and Comparative Examples 1-2 were tested according to the standard GB / T 34336-2017 "Nanoporous Aerogel Composite Thermal Insulation Products". The test results are shown in Table 1 below.

[0082] Table 1 Performance Test Results

[0083]

[0084] Compared with Comparative Examples 1-2, the fiber felt composite materials prepared in Examples 1-8 have higher tensile strength, indicating that the fiber felt composite materials prepared by co-doping silica aerogel with silk fibroin solution and inorganic chopped fibers significantly improve the strength of the fiber felt composite materials.

[0085] Experiment Example 2

[0086] According to the standard GB / T 34336-2017 "Nanoporous Aerogel Composite Thermal Insulation Products", the thermal conductivity of the fiber felt composite materials prepared in Examples 3 to 8 was tested at an average temperature of 20°C. The results are shown in Table 2 below.

[0087] Table 2 Performance Test Results

[0088]

[0089] Compared with Examples 3-4 and 6-7, the fiber felt composite materials prepared in Examples 5 and 8 have a lower thermal conductivity, indicating that the silicon source used in the preparation of the fiber felt composite material is dimethyldiethoxysilane and 2,5-divinyltrimethoxysilanethiophene, which improves the thermal insulation performance of the fiber felt composite material.

[0090] Application examples

[0091] The fiber-felt composite material prepared in Example 8 is applied to a ventilation system, including the following steps:

[0092] After the fiber felt composite material is cut, it is placed into the upper and lower molds, heated, and then molded by compression molding (the compression molding process parameters are: temperature 220℃, pressure 20MPa, and holding time 50 seconds) to form the upper air duct shell and the lower air duct shell. The shell includes the air duct body, welded flanges, and optional functional structures.

[0093] Vibration friction welding is performed on the welding flanges (welding flange width 6mm) of the upper and lower shells to form a complete air duct;

[0094] A schematic diagram of the air duct is shown below. Figures 1-6 As shown in the figure, the air duct shell 100 is divided into an upper air duct shell 101 and a lower air duct shell 102 along the longitudinal direction, and welding flanges 103 are made on each. The upper air duct shell mold cavity 104 and the lower air duct shell mold cavity 105 are processed according to the split upper air duct shell 101 and lower air duct shell 102 respectively. The size of the fiber felt composite material 106 is determined. After heating the fiber felt composite material 106, it is placed in the upper air duct shell mold cavity 104 and the lower air duct shell mold cavity 105. The mold is closed and pressure is applied. The upper air duct shell 101 and the lower air duct shell 102 are molded. The molded upper air duct shell 101 and the lower air duct shell 102 are placed in the vibration friction welding upper air duct shell tooling 107 and the lower air duct shell tooling 108 respectively. The upper air duct shell 101 and the lower air duct shell 102 are connected by vibration friction welding to form a complete fiber felt air duct.

[0095] Performance of a complete fiber felt air duct:

[0096] Weight: The weight of a single air duct is 0.23kg (compared to 0.28kg for PP air ducts of the same specification, a weight reduction of 17.8%).

[0097] Sound insulation: 28dB (40% improvement compared to 20dB for PP ducts of the same specifications);

[0098] Temperature resistance test: No deformation after 24 hours at 120℃, meeting the airflow requirements around the engine compartment of a car.

[0099] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a fiber-felt composite material, characterized in that, Includes the following steps: The fiber felt was impregnated in a gel precursor solution, aged, solvent replaced, and dried to obtain a fiber felt composite material. The preparation method of the gel precursor solution includes the following steps: A1. Mix the silicon source, silk fibroin solution, inorganic short-cut fibers, surfactant and solvent to obtain a preliminary mixture; A2. After adding acid to the initial mixture and mixing, add alkali and continue mixing to obtain the gel precursor solution; The silicon source includes one or more of methyltrimethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, and 2,5-divinyltrimethoxysilanethiophene. The mass ratio of the silicon source, silk fibroin solution, and inorganic short-cut fibers is 10:2:0.5~2; The inorganic chopped fibers have a length of 0.5~0.8mm and a diameter of 10~15μm; The inorganic chopped fibers include one or both of carbon fiber and basalt fiber.

2. The method for preparing a fiber-felt composite material according to claim 1, characterized in that, The surfactant includes one or both of sodium dodecylbenzenesulfonate and hexadecyltrimethylammonium bromide.

3. The method for preparing a fiber-felt composite material according to claim 1, characterized in that, The mass ratio of the silicon source to the surfactant is 1:0.1~0.3; The solvent includes a mixture of ethanol and water; The molar ratio of the silicon source, ethanol, and water is 1:5:12~16.

4. The method for preparing a fiber-felt composite material according to claim 1, characterized in that, The mass ratio of the silicon source, acid solution, and alkali solution is 1:0.5:0.4~0.6; The concentration of the acid solution is 0.1~0.2 mol / L, and the concentration of the alkali solution is 2~2.5 mol / L.

5. The method for preparing a fiber-felt composite material according to claim 1, characterized in that, When the silicon source is dimethyldiethoxysilane and 2,5-divinyltrimethoxysilanethiophene, the mass ratio of dimethyldiethoxysilane to 2,5-divinyltrimethoxysilanethiophene is 5:1~2.

6. The method for preparing a fiber-felt composite material according to claim 1, characterized in that, The fiber felt is made of 80% to 95% high-temperature resistant fibers and 5% to 20% low-melting-point fibers by needle punching, by weight percentage. The high-temperature resistant fiber includes one or two of PET fiber and basalt fiber; The melting point of the low-melting-point fiber is 110~130℃.

7. A fiber-felt composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the fiber felt composite material prepared by the preparation method according to any one of claims 1 to 6 in a ventilation system.

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