Bamboo fiber and carbon fiber double-reinforced resin-based friction material and preparation method of friction plate of bamboo fiber and carbon fiber double-reinforced resin-based friction material

Abstract

The invention discloses a bamboo fiber and carbon fiber double-reinforced resin-based friction material and a brake pad preparation method thereof. Through alkali treatment, plasma activation and carbonization modification of bamboo fibers and nitric acid oxidation treatment of carbon fibers, the problems of insufficient strength of natural fibers and weak interface bonding force of synthetic fibers are solved. The double fibers are synergistically enhanced in a ratio of 3: 2, so that the material has high friction stability (the wear rate at 350 DEG C is less than or equal to 0.25 * 10 <-7 > cm < 3 > / (N.m)), low noise (less than or equal to 75 dB (A)) and excellent heat fading performance (the strength retention rate at 350 DEG C is more than 80%). Raw materials comprise 15-25 parts of phenolic resin, 5-15 parts of modified bamboo fibers and 5-10 parts of carbon fibers, and the composite material is prepared through premixing, melt blending, hot press molding and post-curing. The carbon fiber material is suitable for new energy automobiles and high-performance brake pads and has environmental protection and economical efficiency, and the cost is reduced by 30% or above compared with a single carbon fiber material.

Description

Technical Field

[0001] The present invention relates to the technical field of bamboo fiber and carbon fiber double-reinforced resin-based friction materials, and specifically relates to a bamboo fiber and carbon fiber double-reinforced resin-based friction material and a preparation method of a friction plate thereof. Background Art

[0002] Friction materials are the core components of the braking system, and their performance directly affects driving safety. Traditional brake pads mostly use asbestos or metal fiber-reinforced resin-based materials: asbestos fibers have been banned due to carcinogenic risks; although metal fibers have high strength, they have significant problems such as significant decline in high-temperature performance (friction coefficient drops by more than 20% above 300 °C), high noise (noise ≥ 85 dB(A) during braking), and high density (affecting vehicle energy consumption).

[0003] In recent years, natural fibers (such as bamboo fibers) have received attention due to their environmental protection and renewable advantages. Bamboo fibers are rich in cellulose (content ≥ 45%) and have a high aspect ratio (≥ 50). However, the presence of lignin (content 20% - 30%) and hemicellulose on the fiber surface results in a smooth surface, weak binding force with the resin matrix (interfacial shear strength < 15 MPa), and insufficient heat resistance of single bamboo fiber-reinforced materials (strength begins to decline significantly above 200 °C). Although carbon fibers have high modulus (> 200 GPa) and excellent high-temperature resistance (strength retention rate > 90% at 350 °C), they are costly (about 50 times that of bamboo fibers), and have strong surface inertness. When untreated, the interfacial binding force with the resin is only about 10 MPa, which easily leads to delamination failure of the composite material.

[0004] In the prior art, single-fiber-reinforced friction materials are difficult to balance environmental protection, mechanical properties, and thermal stability. For example, Patent CN202411303592.4 uses single bamboo fiber reinforcement, although the cost is reduced, but the wear rate of the material at 300 °C is as high as 0.5×10 -7 cm 3 / (N·m), which cannot meet the high-temperature requirements of high-speed braking; while single carbon fiber-reinforced materials are difficult to promote due to cost issues. Summary of the Invention

[0005] Aiming at the above technical problems, the present application solves the problems of insufficient strength of natural fibers and weak interfacial binding force of synthetic fibers, and realizes the problems of high stability, low noise, and excellent heat fade performance of friction materials.

[0006] In order to achieve the above object, the technical solution adopted in the present application is: a bamboo fiber and carbon fiber double-reinforced resin-based friction material, which is composed of the following raw materials in parts by weight:

[0007] Phenolic resin matrix: 15 - 25 parts; within this range, it can ensure that the material has good formability and a mechanical property foundation.

[0008] Modified bamboo fiber: 5 - 15 parts; After alkali treatment - plasma activation - carbonization treatment, the surface roughness is increased by 200% - 300%, and the bonding force with resin is significantly enhanced. This treatment process is one of the core innovations of the present invention. Through the synergistic effect of multi-step treatment, the performance of bamboo fiber is effectively improved.

[0009] Carbon fiber: 5 - 10 parts; After nitric acid oxidation treatment, the oxygen-containing functional groups on the surface increase, and the interfacial shear strength is increased by more than 40%. This treatment method aims at the problem of strong surface inertness of carbon fiber and is the key to improving its bonding force with resin.

[0010] Friction performance regulator: 10 - 20 parts; Composed of nano-aluminum oxide, graphene, and molybdenum disulfide in a ratio of 3:2:1. Through the synergistic effect of the three, the stability of the friction coefficient is optimized, and various properties of the friction material can be effectively balanced.

[0011] Filler: 30 - 45 parts; Composed of barite powder, sepiolite powder, and wollastonite powder in a ratio of 4:3:3, adjusting hardness and thermal conductivity. The selection and proportion of different fillers play an important role in regulating the comprehensive properties of the material.

[0012] Coupling agent: 1 - 3 parts. Preferably KH-550 silane coupling agent, enhancing the interfacial bonding between fiber and resin, and its dosage is precisely controlled to achieve the best interfacial modification effect.

[0013] In order to better implement the present invention, further, the preparation method of the modified bamboo fiber includes the following steps:

[0014] Step a. Immerse the bamboo fiber in a NaOH solution with a mass fraction of 5% - 8%, and treat it at 60 - 80 °C for 2 - 4 hours to remove lignin and hemicellulose, and the fiber purity ≥ 90%; This step lays the foundation for subsequent treatment, effectively removing impurities and improving the purity and activity of the fiber.

[0015] Step b. After washing to neutral, immerse the bamboo fiber in a silane coupling agent solution with a concentration of 0.5% - 2% for 1 - 2 hours; Introduce active groups to enable the fiber surface to have the conditions for chemical reaction with resin.

[0016] Step c. After drying at 80 - 100 °C, perform plasma treatment with a power of 300 - 500 W in an argon atmosphere for 5 - 10 minutes to obtain surface-activated modified bamboo fiber. Nanoscale grooves are formed on the surface (the roughness Ra increases from 1.2 μm to 3.5 - 4.0 μm), greatly increasing the specific surface area and active sites on the fiber surface.

[0017] In order to better implement the present invention, further, in step c,

[0018] The plasma-treated bamboo fibers are further placed in a nitrogen-protected atmosphere furnace and heated at a heating rate of 10 °C / min to 400 - 800 °C, and held for 1 - 2 hours to obtain carbonized bamboo fibers with a carbon content of ≥80%. It combines the toughness of natural fibers and the high-temperature resistance of carbon materials. The carbonization treatment endows bamboo fibers with unique properties, enabling them to better synergize with carbon fibers.

[0019] To better implement the present invention, further, the carbon fiber is a polyacrylonitrile-based carbon fiber with a length of 1 - 5 mm, and is used after being oxidized in a 30% - 50% nitric acid solution at 60 °C for 30 minutes.

[0020] To better implement the present invention, further, the friction property regulator is a mixture of nano-aluminum oxide, graphene, and molybdenum disulfide, and the mass ratio of the three is 3:2:1.

[0021] To better implement the present invention, further, the filler includes barite powder, sepiolite powder, and wollastonite powder, and the particle sizes of the three are all 50 - 200 mesh, and the mass ratio is 4:3:3.

[0022] To better implement the present invention, further, the coupling agent is KH-550 silane coupling agent.

[0023] A preparation method of a bamboo fiber and carbon fiber double-reinforced resin-based friction material includes the following steps:

[0024] Step A. Add the modified bamboo fibers, carbon fibers, and filler into a high-speed mixer and premix at a rotation speed of 500 - 1000 r / min for 5 - 10 minutes;

[0025] Step B. Add phenolic resin, coupling agent, and friction property regulator, and melt and blend at 150 - 180 °C for 20 - 30 minutes to form a uniform mixture;

[0026] Step C. Transfer the mixture to a hot pressing mold, and keep the pressure at 15 - 25 MPa and the temperature at 160 - 180 °C for 8 - 15 minutes to hot press and form;

[0027] Step D. Place the formed friction material in an oven and heat it to 200 - 220 °C in a stepwise heating manner, and hold for 4 - 6 hours for post-curing treatment.

[0028] A brake pad uses the aforementioned bamboo fiber and carbon fiber double-reinforced resin-based friction material. The Rockwell hardness of the brake pad is 85 - 95 HRM, the friction coefficient at 350 °C is ≥0.38, and the wear rate is ≤0.25×10 -7 cm 3 / (N·m).

[0029] To better implement the present invention, further, the friction coefficient of the brake pad has a volatility of ≤5% within the temperature range of 100-350°C, and the noise during braking is ≤75 dB(A).

[0030] The technical solution provided by the present invention has the following beneficial effects compared with the prior art:

[0031] 1. In the present invention, bamboo fibers (aspect ratio > 50) inhibit crack propagation through bridging action and improve toughness (impact strength 8.5 kJ / m 2 , a 60% increase compared to a single fiber system); carbon fibers (modulus > 200 GPa) provide a rigid framework to maintain structural stability at high temperatures (strength retention rate at 350°C > 80%); at the optimal ratio (bamboo fiber:carbon fiber = 3:2), the interfacial bonding force of the composite material is increased by 35%, achieving "rigidity and flexibility combined". Similar synergistic strengthening methods and effects are not involved in the prior art. Through fiber treatment and ratio optimization, a significant improvement in material properties is achieved.

[0032] 2. In the present invention, bamboo fibers are treated with alkali to remove impurities, activated by plasma to increase surface roughness, and treated with a coupling agent to introduce -SiO bonds, forming a chemical bond with phenolic resin; after nitric acid oxidation of carbon fibers, the surface polar groups increase, enhancing the physical entanglement and chemical adsorption with the resin, and the interfacial shear strength is increased from 12 MPa to 17 MPa.

[0033] 3. In the present invention, the wear rate at 350°C is ≤0.25×10 -7 cm 3 / (N·m), a 50% reduction compared to traditional materials; the friction coefficient is stable within the range of 0.38-0.42 from 100-350°C, with a volatility of ≤5% and a thermal fade rate of ≤8%; the thermal decomposition temperature (TGA test) is increased by 120°C compared to the pure resin matrix, reaching above 380°C.

[0034] 4. In the present invention, bamboo fibers come from renewable resources, reducing the dependence on asbestos and metal fibers; the amount of carbon fibers used (5-10 parts) is reduced by 40%-50% compared to a single carbon fiber system, and the cost is reduced by more than 30%. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0036] Figure 1 It is the process flow diagram of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of this application. Components of the embodiments of this application usually described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0038] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of this application claimed, but merely represents selected embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts fall within the scope of protection of this application.

[0039] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0040] In the description of this application, it should be noted that if terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this application is usually placed during use. It is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to this application. In addition, in the description of this application, if terms such as "first", "second", etc. are used only for distinguishing descriptions, they cannot be understood as indicating or implying relative importance.

[0041] In addition, in the description of this application, if terms such as "horizontal" and "vertical" are used, it does not mean that the components are required to be absolutely horizontal or hanging vertically, but can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0042] In the description of this application, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "connected" are used, they 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 directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific situations.

[0043] The present invention provides a bamboo fiber and carbon fiber double-reinforced resin-based friction material, and its raw material composition (by weight) is as follows:

[0044] Phenolic resin matrix: 15 - 25 parts, as a binder to provide matrix support;

[0045] Modified bamboo fiber: 5 - 15 parts, which is treated by alkali treatment - plasma activation - carbonization treatment, the surface roughness is increased by 200% - 300%, and the binding force with the resin is enhanced;

[0046] Carbon fiber: 5 - 10 parts, which is treated by nitric acid oxidation, the oxygen-containing functional groups on the surface are increased, and the interfacial shear strength is increased by more than 40%;

[0047] Friction property regulator: 10 - 20 parts, which is composed of nano-aluminum oxide, graphene, and molybdenum disulfide in a ratio of 3:2:1 to optimize the stability of the friction coefficient;

[0048] Filler: 30 - 45 parts, which is composed of barite powder, sepiolite powder, and wollastonite powder in a ratio of 4:3:3 to adjust the hardness and thermal conductivity;

[0049] Coupling agent: 1 - 3 parts, preferably KH-550 silane coupling agent, to enhance the interfacial bonding between the fiber and the resin.

[0050] The preparation method of the modified bamboo fiber includes:

[0051] Alkali treatment: Treat with 5% - 8% NaOH solution at 60 - 80 °C for 2 - 4 hours to remove lignin and hemicellulose, and the fiber purity ≥ 90%;

[0052] Coupling agent treatment: Immerse in 0.5% - 2% silane coupling agent solution for 1 - 2 hours to introduce active groups;

[0053] Plasma activation: Treat with 300 - 500 W argon plasma for 5 - 10 minutes to form nano-scale grooves on the surface (the roughness Ra is increased from 1.2 μm to 3.5 - 4.0 μm);

[0054] Carbonization treatment: Keep in a nitrogen atmosphere furnace at 400 - 800 °C for 1 - 2 hours to obtain carbonized bamboo fiber (carbon content ≥ 80%), which has both the toughness of natural fiber and the high temperature resistance of carbon materials.

[0055] The carbon fiber is polyacrylonitrile-based, with a length of 1 - 5 mm, and is oxidized with 30% - 50% nitric acid at 60 °C for 30 minutes. Polar groups such as hydroxyl groups and carboxyl groups are generated on the surface, and the interfacial shear strength is increased from 10 MPa to more than 14 MPa.

[0056] The preparation process includes:

[0057] Premixing: In a high-speed mixer, the modified bamboo fibers, carbon fibers and fillers are premixed for 5 - 10 minutes to ensure uniform dispersion. The rotation speed and time during premixing are precisely controlled to ensure the uniform distribution of fibers and fillers in the matrix and avoid agglomeration.

[0058] Melt blending: Phenolic resin, coupling agent and friction property regulator are added, and melt blending is carried out at 150 - 180°C for 20 - 30 minutes to form a uniform matrix. The selection of temperature and time in this step is crucial and directly affects the mixing effect of the materials and the melting state of the resin.

[0059] Hot pressing and forming: Pressurize at 15 - 25 MPa, hold the pressure at 160 - 180°C for 8 - 15 minutes for curing and forming. The pressure, temperature and pressure holding time in hot pressing and forming act together to determine the final structure and properties of the material.

[0060] Post-curing: Gradually increase the temperature to 200 - 220°C and keep warm for 4 - 6 hours to improve the material density. The post-curing process adopts a stepwise temperature increase method to effectively avoid internal stress generated by the material due to too rapid temperature change and ensure the stable performance of the material.

[0061]

[0062]

[0063] Now, examples are analyzed as follows:

[0064] Example 1

[0065] Raw material ratio (parts by weight):

[0066] Phenolic resin: 20 parts

[0067] Modified bamboo fibers (by the preparation method of modified bamboo fibers): 10 parts

[0068] Carbon fibers (treated with nitric acid): 7 parts

[0069] Nano-aluminum oxide / graphene / molybdenum disulfide (3:2:1): 15 parts

[0070] Barite / sepiolite / wollastonite (4:3:3): 35 parts

[0071] KH-550 silane coupling agent: 2 parts

[0072] Preparation process:

[0073] 1. Bamboo fiber treatment: Treat with 5% NaOH solution at 70°C for 3 hours, wash with water and then immerse in 1% KH-550 solution for 1.5 hours, followed by plasma treatment (400W, argon, 8 minutes).

[0074] 2. Carbon fiber treatment: oxidized with 40% nitric acid at 60 °C for 30 minutes, then washed and dried.

[0075] 3. Carbonization treatment of bamboo fiber: heated to 800 °C at a rate of 10 °C / min in a nitrogen atmosphere furnace and held for 2 hours to obtain carbonized bamboo fiber.

[0076] 4. Mixing and melting: high-speed shear blending at 160 °C for 25 minutes.

[0077] 5. Hot pressing and forming: pressure 20 MPa, temperature 170 °C, holding pressure for 10 minutes.

[0078] 6. Post-curing: gradually heated to 210 °C and held for 5 hours.

[0079] Performance testing

[0080] Coefficient of friction (SAE J2522 standard): 0.42 (100 °C), 0.39 (350 °C);

[0081] Wear rate: 0.18×10 -7 cm 3 / (N·m);

[0082] Rockwell hardness: 92 HRM;

[0083] Thermal fade rate (300 °C): ≤8%.

[0084] The dual-fiber system forms an interlocking structure at high temperatures. The toughness of bamboo fiber absorbs impact energy, and the carbon fiber skeleton maintains overall rigidity, making the coefficient of friction fluctuation of the brake pad <5% under high-speed braking conditions and reducing the noise by more than 15 dB(A).

[0085] This material is suitable for new energy vehicles and high-performance braking systems, has passed bench test verification (no thermal fade after 1000 consecutive brakings), and the service life is extended by more than 30% compared with traditional materials.

[0086] Example 2

[0087] Friction material (parts by weight)

[0088] Phenolic resin: 20 parts;

[0089] Modified bamboo fiber (prepared in Example 1): 10 parts;

[0090] Carbon fiber (PAN-based, length 3 mm, oxidized with 40% nitric acid at 60 °C for 30 minutes): 7 parts;

[0091] Friction performance regulator: 6 parts of nano-aluminum oxide, 4 parts of graphene, 2 parts of molybdenum disulfide (total 12 parts);

[0092] Filler: 14 parts of barite powder, 10.5 parts of sepiolite powder, 10.5 parts of wollastonite powder (total 35 parts);

[0093] KH-550 coupling agent: 2 parts.

[0094] Preparation steps:

[0095] Premixing: Add the modified bamboo fiber, carbon fiber, and filler to a high-speed mixer (rotation speed 800 r / min) and mix for 8 minutes;

[0096] Melting and blending: Add phenolic resin, coupling agent, and friction property regulator, heat and stir at 160 °C for 25 minutes to form a uniform material;

[0097] Hot pressing and forming: Pour the material into a mold (size 100 mm × 100 mm × 5 mm), keep the pressure at 20 MPa and the temperature at 170 °C for 10 minutes;

[0098] Post-curing: In an oven, heat up to 120 °C at a rate of 5 °C / min (hold for 2 h) → 160 °C (hold for 2 h) → 210 °C (hold for 5 h), and then cool naturally to room temperature.

[0099] Performance testing

[0100] Friction property (SAE J2522 standard):

[0101] Friction coefficient at 100 °C: 0.42; friction coefficient at 350 °C: 0.39; volatility: 2.5%;

[0102] Wear rate (at 350 °C): 0.18×10 -7 cm 3 / (N·m);

[0103] Mechanical properties:

[0104] Impact strength: 8.5 kJ / m 2 ; Rockwell hardness: 92 HRM;

[0105] Thermal properties:

[0106] Thermal decomposition temperature (5% weight loss): 385 °C; strength retention rate at 350 °C: 82%;

[0107] Noise test: Noise ≤ 70 dB(A) during braking, which is more than 15 dB lower than that of traditional metal fiber materials.

[0108] Example 3

[0109] Table 1 Comparison of different fiber ratios

[0110]

[0111] The results show that when the weight ratio of bamboo fiber to carbon fiber is 3:2, the comprehensive performance of the composite material is optimal, verifying the best ratio of the dual-fiber synergistic effect.

[0112] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A bamboo fiber and carbon fiber double-reinforced resin-based friction material, characterized in that: It consists of the following raw materials in parts by weight: Phenolic resin matrix: 15 - 25 parts; Modified bamboo fiber: 5 - 15 parts; Carbon fiber: 5 - 10 parts; Friction property regulator: 10 - 20 parts; Filler: 30 - 45 parts; Coupling agent: 1 - 3 parts.

2. The bamboo fiber and carbon fiber double-reinforced resin-based friction material according to claim 1, wherein: The preparation method of the modified bamboo fiber includes the following steps: Step a. Immerse the bamboo fiber in a NaOH solution with a mass fraction of 5% - 8%, and treat it at 60 - 80 °C for 2 - 4 hours to remove lignin and hemicellulose; Step b. After washing with water until neutral, soak the bamboo fiber in a 0.5% - 2% silane coupling agent solution for 1 - 2 hours; Step c. After drying at 80 - 100 °C, perform plasma treatment with a power of 300 - 500 W in an argon atmosphere for 5 - 10 minutes to obtain surface-activated modified bamboo fiber.

3. A bamboo fiber and carbon fiber double-reinforced resin-based friction material according to claim 1, characterized in that: In step c, The plasma-treated bamboo fiber is further placed in a nitrogen-protected atmosphere furnace, heated to 400 - 800 °C at a heating rate of 10 °C / min, and kept warm for 1 - 2 hours to obtain carbonized bamboo fiber with a carbon content of ≥80%.

4. A bamboo fiber and carbon fiber double-reinforced resin-based friction material according to claim 1, characterized in that: The carbon fiber is a polyacrylonitrile-based carbon fiber with a length of 1 - 5 mm, and is used after being oxidized in a 30% - 50% nitric acid solution at 60 °C for 30 minutes.

5. A bamboo fiber and carbon fiber double-reinforced resin-based friction material according to claim 1, characterized in that: The friction property regulator is a mixture of nano-aluminum oxide, graphene, and molybdenum disulfide, and the mass ratio of the three is 3:2:

1.

6. The bamboo fiber and carbon fiber double-reinforced resin-based friction material according to claim 1, characterized in that: The filler includes barite powder, sepiolite powder, and wollastonite powder. The particle sizes of the three are all 50 - 200 mesh, and the mass ratio is 4:3:

3.

7. A bamboo fiber and carbon fiber double-reinforced resin-based friction material according to claim 1, characterized in that: The coupling agent is KH-550 silane coupling agent.

8. A brake pad, characterized in that: Adopt a bamboo fiber and carbon fiber double-reinforced resin-based friction material as described in any one of claims 1-7, the Rockwell hardness of the brake pad is 85-95 HRM, the friction coefficient at 350 °C is ≥ 0.38, and the wear rate is ≤ 0.25×10 -7 cm 3 / (N·m).

9. The brake pad according to claim 8, characterized in that: The friction coefficient of the brake pad has a volatility of ≤5% in the temperature range of 100 - 350 °C, and the noise during braking is ≤75 dB(A).

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