Brake friction material and preparation method and application thereof

Abstract

The invention relates to the technical field of friction materials, in particular to a brake friction material and a preparation method and application thereof. The brake friction material is mainly prepared from the following components in parts by weight: 1-10 parts of modified coconut fibers, 3-8 parts of sepiolite fibers, 17-23 parts of mineral fibers, 6-12 parts of phenolic resin, 5-13 parts of crystalline flake graphite, 4-10 parts of petroleum coke, 3-9 parts of aluminum oxide, 1-3 parts of friction powder, 10-16 parts of calcium carbonate, 2-8 parts of vermiculite powder, 15-25 parts of precipitated barium sulphate and 0.5-1.5 parts of zinc stearate. According to the brake friction material, specific components are adopted, a proper ratio is controlled, and particularly, the modified coconut fibers, the sepiolite fibers and the mineral fibers in a specific ratio are adopted, so that the heat fading resistance and the recovery performance of the brake friction material can be improved, and the wear rate is reduced.

Description

Technical Field

[0001] This invention relates to the field of friction materials technology, and more specifically, to a braking friction material, its preparation method, and its application. Background Technology

[0002] With the continuous increase in the number of cars in my country, the market demand for brake pads, as a key safety component, is also growing. The performance of the braking system directly affects the safety and driving experience of a vehicle, making the selection and optimization of brake friction materials a focus of research.

[0003] Currently, the most common friction braking materials on the market include metals, ceramics, and organic synthetic materials, each with its own advantages and disadvantages. Among them, metal brake friction materials have the advantage of high thermal conductivity, but their heavy weight reduces fuel efficiency; ceramic brake friction materials have the advantage of high-temperature stability, but their cost is high and their production and preparation processes are complex.

[0004] With the increasing popularity of environmental protection and sustainable development concepts, plant fibers are gaining increasing application value due to their irreplaceable advantages such as lightweight, low cost, and pollution-free properties. Using plant fibers in the preparation of brake friction materials can not only replace some traditional harmful or high-cost materials, reducing overall production costs, but also improve the comprehensive performance of braking systems.

[0005] However, the friction materials produced by existing technologies have poor resistance to thermal degradation and recovery properties, and a high wear rate.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The primary objective of this invention is to provide a braking friction material that, by employing specific components and controlling appropriate proportions, particularly by employing specific proportions of modified coconut fiber, sepiolite fiber, and mineral fiber, can improve the heat fading resistance and recovery performance of the braking friction material and reduce the wear rate.

[0008] The second objective of this invention is to provide a method for preparing a braking friction material.

[0009] A third objective of this invention is to provide the application of braking friction materials in automotive braking systems.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: The present invention first provides a braking friction material, which is mainly composed of the following components by weight: 1-10 parts modified coconut fiber, 3-8 parts sepiolite fiber, 17-23 parts mineral fiber, 6-12 parts phenolic resin, 5-13 parts flake graphite, 4-10 parts petroleum coke, 3-9 parts alumina, 1-3 parts friction powder, 10-16 parts calcium carbonate, 2-8 parts vermiculite powder, 15-25 parts precipitated barium sulfate, and 0.5-1.5 parts zinc stearate.

[0011] Furthermore, the modified coconut fiber comprises 2 to 6 parts.

[0012] Furthermore, the sepiolite fiber content is 4 to 6 parts.

[0013] Furthermore, the mineral fiber content is 19 to 21 parts.

[0014] Furthermore, the method for preparing the modified coconut fiber includes: soaking coconut fiber in water and then crushing it, followed by drying and sieving to obtain short-cut fibers with a particle size of 40-60 mesh; soaking the short-cut fibers in an alkaline solution, reacting, washing and drying to obtain the modified coconut fiber.

[0015] Furthermore, the particle size of the chopped fibers is 40-60 mesh.

[0016] Furthermore, the mass fraction of the alkaline solution is 0.5% to 2%.

[0017] Furthermore, the mass ratio of the chopped fibers to the volume of the alkaline solution is 1:25~35 g / mL.

[0018] Furthermore, the reaction time is 30-60 minutes.

[0019] The present invention also provides a method for preparing the above-mentioned braking friction material, comprising the following steps: mixing the raw materials and then hot pressing them to obtain a pressed product; heat treating the pressed product to obtain a heat-treated material; and machining the heat-treated material to obtain the braking friction material.

[0020] Furthermore, the pressure of the hot pressing process is 10~15MPa.

[0021] Furthermore, the temperature of the hot pressing process is 160~180℃.

[0022] Furthermore, the total number of pressure holding times in the hot pressing process is 6, wherein the pressure holding time for the first and second times is 3~8s, the pressure holding time for the third, fourth and fifth times is 8~13s, and the pressure holding time for the sixth time is 800~1000s.

[0023] Furthermore, the total number of venting operations in the hot pressing process is 6, wherein the venting time for the first to fifth venting operations is 3 to 8 seconds, and the venting time for the sixth venting operation is 20 to 40 seconds.

[0024] Furthermore, the heat treatment includes: first holding at 130~150℃ for 0.5~1.5h, then raising the temperature to 150~170℃ and holding for 2~4h, and finally raising the temperature to 170~190℃ and holding for 5~8h.

[0025] Furthermore, the machining process includes cutting and grinding.

[0026] The present invention also provides the application of the above-mentioned braking friction material in automotive braking systems.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: by using specific components and controlling appropriate proportions, especially by using modified coconut fiber, sepiolite fiber and mineral fiber in specific proportions, the present invention can improve the heat fading resistance and recovery performance of braking friction materials and reduce the wear rate. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 Images of modified coconut fiber provided for this invention; Figure 2 Comparison of the degradation test results of the braking friction materials prepared in Examples 1-4 and Comparative Example 1 of the present invention; Figure 3 Comparison of the recovery test results of the braking friction materials prepared in Examples 1-4 and Comparative Example 1 of the present invention; Figure 4 The wear rate of the braking friction material prepared in Examples 1-4 and Comparative Example 1 of this invention varies with temperature. Figure 5 SEM image of the braking friction material prepared in Example 1 of this invention; Figure 6 SEM image of the braking friction material prepared in Example 2 of this invention; Figure 7 SEM image of the braking friction material prepared in Example 3 of this invention; Figure 8SEM image of the braking friction material obtained in Example 4 of this invention; Figure 9 SEM image of the braking friction material prepared in Comparative Example 1 provided by the present invention. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0031] Unless otherwise specified, in this invention, terms such as "first aspect," "second aspect," "third aspect," and "fourth aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, terms such as "first," "second," "third," and "fourth" serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0032] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0033] Unless otherwise specified, in this invention, "one or more" or "at least one" refers to any one, any two, or any two or more of the listed items. "Several" refers to any two or more.

[0034] In a first aspect, the present invention provides a braking friction material, which is a multi-component composite material composed of multiple components, mainly made of the following components by weight: 1-10 parts modified coconut fiber, 3-8 parts sepiolite fiber, 17-23 parts mineral fiber, 6-12 parts phenolic resin, 5-13 parts flake graphite, 4-10 parts petroleum coke, 3-9 parts alumina, 1-3 parts friction powder, 10-16 parts calcium carbonate, 2-8 parts vermiculite powder, 15-25 parts precipitated barium sulfate, and 0.5-1.5 parts zinc stearate.

[0035] Modified coconut fiber is used as a reinforcing plant fiber, combined with sepiolite fiber and mineral fiber. Phenolic resin is used as a binder. Calcium carbonate, vermiculite powder, and precipitated barium sulfate are used as fillers. Flake graphite, petroleum coke, alumina, friction powder, and zinc stearate are used as friction modifiers.

[0036] The modified coconut fiber can be in quantities of 2, 3, 4, 5, 6, 7, 8, or 10 parts; the sepiolite fiber can be in quantities of 3, 4, 5, 6, 7, or 8 parts; the mineral fiber can be in quantities of 18, 19, 20, or 22 parts; the phenolic resin can be in quantities of 7, 8, 9, 10, or 11 parts; the flake graphite can be in quantities of 6, 8, 10, or 12 parts; and the petroleum coke can be in quantities of 5, 6, 7, 8, or 9 parts. The following amounts are used: alumina (e.g., 4, 5, 6, 7, or 8 parts); friction powder (e.g., 1.5, 2, or 2.5 parts); calcium carbonate (e.g., 11, 12, 13, 14, or 15 parts); vermiculite powder (e.g., 3, 4, 5, 6, or 7 parts); precipitated barium sulfate (e.g., 16, 18, 20, 22, 23, or 24 parts); and zinc stearate (e.g., 0.6, 0.8, 1, 1.3, or 1.5 parts).

[0037] It is understandable that the performance of brake friction materials will vary depending on the proportions of the components and the raw materials used.

[0038] This invention improves the heat fading resistance and recovery performance of braking friction materials and reduces wear rate by using specific components and controlling appropriate proportions, especially by using modified coconut fiber, sepiolite fiber and mineral fiber in specific proportions.

[0039] Natural plant fibers typically contain a large number of hydroxyl groups on their surface, thus exhibiting polarity and hydrophilicity. However, the phenolic resin used in this invention is non-polar and hydrophobic, resulting in poor compatibility and low bonding between the two, which significantly reduces the overall performance of the braking friction material. Therefore, to improve the compatibility of the reinforcing fiber with other components in the formulation, this invention modifies the coconut fiber. This modification reduces its inherent polarity and hydrophilicity, thereby improving the fiber's reinforcing efficiency in braking friction materials.

[0040] Furthermore, the modified coconut fiber, sepiolite fiber, and mineral fiber exhibit a synergistic effect. In some specific embodiments, using the aforementioned braking friction material can reduce the wear rate by 38.2%.

[0041] In some specific embodiments, the modified coconut fiber is 2 to 6 parts, preferably 4 to 6 parts.

[0042] This invention uses modified coconut fiber as the main reinforcing fiber, which can reduce costs and is also beneficial to the environment.

[0043] In some specific embodiments, the sepiolite fiber is 4 to 6 parts, preferably 5 parts.

[0044] In some specific embodiments, the mineral fiber is 19 to 21 parts, preferably 20 parts.

[0045] In some specific embodiments, the method for preparing the modified coconut fiber includes: After soaking coconut fiber in water for 24-48 hours, it is crushed using a pulverizer to expose the fiber. Then, it is dried in a constant temperature oven until constant weight is achieved, and then sieved using a sieve to obtain short-cut fibers with a particle size of 40-60 mesh.

[0046] The chopped fibers were then soaked in an alkaline solution and reacted for 30-60 minutes. After washing, they were dried at 60-80°C (to constant weight) to obtain the modified coconut fiber.

[0047] In this process, alkaline solutions can dissolve most of the non-cellulose components that give plant fibers their polarity and hydrophilicity, such as lignin, gums, hemicellulose, and waxes, thereby enhancing the compatibility of the fiber with other components in the formulation. Furthermore, fibers modified with alkaline solutions have more cellulose exposed, increasing their reactivity and significantly improving their mechanical properties.

[0048] See image for modified coconut fiber Figure 1 As shown.

[0049] In some specific embodiments, the mass fraction of the alkaline solution is 0.5% to 2%, for example, 1% or 1.5%.

[0050] In some specific embodiments, the mass ratio of the chopped fibers to the volume of the alkaline solution is 1:25~35g / mL (i.e., 25~35g of chopped fibers are added per mL of NaOH solution), for example, 1:28g / mL, 1:30g / mL or 1:32g / mL.

[0051] In some specific embodiments, the coconut fiber includes coconut shell fiber from the king coconut tree.

[0052] Among various plant fibers, coconut fiber possesses excellent wear resistance and high heat resistance, maintaining good tribological properties under high-temperature conditions while significantly reducing braking noise. This invention applies plant fibers to braking friction materials, effectively addressing resource waste while also promoting rural economic development.

[0053] In some specific embodiments, during the soaking process of the chopped fibers in the NaOH solution, the mixture is continuously stirred to ensure that the chopped fibers react fully with the NaOH solution.

[0054] In some specific embodiments, the alkaline solution includes, but is not limited to, NaOH solution.

[0055] In some specific embodiments, the washing method includes: continuously rinsing the short-cut fibers soaked in the alkaline solution with distilled water until the pH of the rinsing solution is neutral.

[0056] Secondly, the present invention provides a method for preparing the above-mentioned braking friction material, which includes the following steps: After the raw materials are mixed evenly to obtain a mixed material, they are subjected to hot pressing to obtain a pressed product.

[0057] Specifically, according to the target formula of the braking friction material, the raw materials are weighed in proportion, and then a mixer is used to thoroughly stir the weighed raw materials to ensure that the raw materials are mixed evenly and without agglomeration, thus obtaining a mixed material. The mixed material is then placed into the mold cavity of a hot press for hot pressing molding. Preferably, the weight of the mixed material placed in each mold cavity is 90g. Preferably, because the binder phenolic resin is a thermosetting material, the mold cavity needs to be preheated to above 150°C before hot pressing molding, and the mixed material is quickly poured into it for hot pressing molding to prevent the mixed material from deforming before hot pressing, which would adversely affect the performance of the braking friction material.

[0058] In order to ensure that the phenolic resin adhesive can be fully cured while eliminating the residual stress and thermal stress inside the friction material after hot pressing, and to prevent deformation and warping of the pressed product, the pressed product is subjected to heat treatment and then cooled (slowly reduced to room temperature) to obtain the heat-treated material.

[0059] To ensure that the dimensions of the friction material meet the requirements of the corresponding performance tests, the heat-treated material is machined using a sample cutting and grinding machine to obtain the braking friction material.

[0060] This preparation method has the advantages of simple operation, short process and low cost, and is suitable for mass production.

[0061] In some specific embodiments, the pressure of the hot pressing process is 10~15MPa, for example 11MPa, 12MPa, 13MPa or 14MPa.

[0062] In some specific embodiments, the temperature of the hot pressing process is 160~180°C, for example 165°C, 170°C or 175°C.

[0063] In some specific embodiments, the total number of holding pressure cycles in the hot pressing process is 6, wherein the holding pressure time for the 1st and 2nd cycles is 3-8s, the holding pressure time for the 3rd, 4th and 5th cycles is 8-13s (e.g., 9s, 10s, 11s or 12s), and the holding pressure time for the 6th cycle is 800-1000s (e.g., 850s, 900s, 950s or 980s).

[0064] In some specific embodiments, the total number of venting operations in the hot pressing process is 6, wherein the venting time for the 1st to 5th operations is 3 to 8 seconds (e.g., 4 seconds, 5 seconds, 6 seconds or 7 seconds), and the venting time for the 6th operation is 20 to 40 seconds (e.g., 25 seconds, 30 seconds, 35 seconds or 38 seconds).

[0065] The reason for venting is that during the hot pressing process, water vapor and volatiles are generated as the material solidifies. If these are not vented in time, cracks and blistering may occur in the brake friction material after hot pressing. To avoid this, intermittent venting is required while maintaining pressure.

[0066] In some specific embodiments, the heat treatment includes: first holding at 130~150℃ (e.g., 135℃, 140℃ or 145℃) for 0.5~1.5h (e.g., 1h), then raising the temperature to 150~170℃ (e.g., 155℃, 160℃ or 165℃) and holding for 2~4h (e.g., 3h), and finally raising the temperature to 170~190℃ (e.g., 175℃, 180℃ or 185℃) and holding for 5~8h (e.g., 6h or 7h).

[0067] In some specific embodiments, the heat treatment is carried out using a heat treatment drying oven (model: JF980S, Jilin Jida Electromechanical Equipment Co., Ltd.), but it is not limited to this.

[0068] In some specific embodiments, the machining includes cutting and grinding.

[0069] Thirdly, the present invention provides the application of the above-mentioned braking friction material in an automotive braking system.

[0070] Using the aforementioned braking friction materials in automotive braking systems, such as brake pads, can not only replace some traditional harmful or high-cost materials and reduce overall production costs, but also improve the comprehensive performance of automotive braking systems, especially their resistance to heat fade and recovery performance, and reduce wear rates.

[0071] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0072] Example 1 The method for preparing the braking friction material provided in this embodiment includes the following steps: (1) After soaking the coconut shell fiber of the king coconut tree in clean water for 24 minutes, it was crushed using a pulverizer to expose the fiber. Then, it was dried in a constant temperature oven to constant weight and sieved using a sieve to obtain short-cut fibers with a particle size of 50 mesh. The short-cut fibers were soaked in a 1% NaOH solution, where the mass ratio of the short-cut fibers to the volume of the NaOH solution was 1:30 g / mL. After stirring continuously and soaking for 30 minutes, the fibers were rinsed continuously with distilled water until the pH of the rinsing solution was neutral. Finally, the fibers were dried at 70°C to constant weight to obtain modified coconut fiber.

[0073] (2) According to the formula in Table 1, weigh each raw material and mix it thoroughly with a mixer to obtain a mixed material. Then, put the mixed material into the mold cavity of the hot press (preheated to 170°C) for hot pressing. The weight of the mixed material put into each mold cavity is 90g, the pressure of the hot pressing is 11MPa, and the temperature is 170°C. The total number of holding pressures in the hot pressing process is 6, with the holding time for the first and second times being 5s, the holding time for the third, fourth and fifth times being 10s, and the holding time for the sixth time being 900s. The total number of venting processes in the hot pressing process is 6, with the venting time for the first to fifth times being 5s, and the venting time for the sixth time being 30s, to obtain the pressed product.

[0074] (3) The above-mentioned pressed products are subjected to heat treatment, wherein the heat treatment method is as follows: first, the temperature is kept at 140°C for 1 hour, then the temperature is raised to 160°C and kept for 3 hours, and finally the temperature is raised to 180°C and kept for 6 hours. Then the temperature is slowly lowered to room temperature to obtain the heat-treated material.

[0075] (4) The heat-treated material was cut and ground using a sample cutting and grinding machine to obtain the braking friction material (marked as C-2).

[0076] Example 2 Weigh each raw material according to the formula in Table 1 (the amount of modified coconut fiber added varies), and prepare the braking friction material (marked as C-4) according to the method in Example 1.

[0077] Example 3 Weigh each raw material according to the formula in Table 1 (the amount of modified coconut fiber added varies), and prepare the braking friction material (marked as C-6) according to the method in Example 1.

[0078] Example 4 Weigh each raw material according to the formula in Table 1 (the amount of modified coconut fiber added varies), and prepare the braking friction material (marked as C-8) according to the method in Example 1.

[0079] Comparative Example 1 Weigh each raw material (without added modified coconut fiber) according to the formula in Table 1, and prepare the braking friction material (marked as I-0) according to the method in Example 1.

[0080] Table 1 Raw material formulations for various braking friction materials

[0081] Example 5 Weigh each raw material according to the formula in Table 2 (the amount of sepiolite fiber added is different from that in Example 3), and prepare the braking friction material according to the method in Example 1.

[0082] Example 6 Weigh each raw material according to the formula in Table 2 (the amount of mineral fiber added is different from that in Example 3), and prepare the braking friction material according to the method in Example 1.

[0083] Example 7 Weigh each raw material according to the formula in Table 2 (the amount of binder, filler and friction modifier added is different from that in Example 3), and prepare the braking friction material according to the method in Example 1.

[0084] Example 8 Weigh each raw material according to the formula in Table 2 (the amount of binder, filler and friction modifier added is different from that in Example 3), and prepare the braking friction material according to the method in Example 1.

[0085] Table 2 Raw material formulations for various braking friction materials

[0086] Example 9 The method for preparing the braking friction material provided in this embodiment includes the following steps: (1) After soaking the coconut shell fiber of the king coconut tree in clean water for 36 hours, it was crushed using a pulverizer to expose the fiber. Then, it was dried in a constant temperature oven to constant weight and sieved using a sieve to obtain short-cut fibers with a particle size of 60 mesh. The short-cut fibers were soaked in a 1.5% NaOH solution, where the mass ratio of the short-cut fibers to the volume of the NaOH solution was 1:32 g / mL. The solution was stirred continuously and soaked for 40 minutes. Then, it was rinsed continuously with distilled water until the pH of the rinsing solution was neutral. Finally, it was dried at 70°C to constant weight to obtain modified coconut fiber.

[0087] (2)~(4): The steps (2)~(4) of Example 1 are basically the same, except that each raw material is weighed according to the formula of Example 3 in Table 1 and the modified coconut fiber prepared in this example is used.

[0088] Comparative Example 2 Weigh each raw material according to the formula in Table 3 (without the addition of sepiolite fiber compared to Example 1), and prepare the braking friction material according to the method of Example 1.

[0089] Comparative Example 3 Weigh each raw material according to the formula in Table 3 (no mineral fiber was added compared to Example 1), and prepare the braking friction material according to the method of Example 1.

[0090] Comparative Example 4 Weigh each raw material according to the formula in Table 3 (the ratio of each fiber material is different from that in Example 1), and prepare the braking friction material according to the method in Example 1.

[0091] Table 3 Raw material formulations for various braking friction materials

[0092] Comparative Example 5 The formula is basically the same as Example 1, except that the modified coconut fiber in Table 1 is replaced with an equal mass of unmodified coconut shell fiber from the king palm.

[0093] Experimental Example The degradation test results of the braking friction materials prepared in Examples 1-4 and Comparative Example 1 are as follows: Figure 2As shown, it can be seen that with increasing temperature, the friction coefficient of the unmodified coconut fiber (Comparative Example 1) gradually decreases, while the braking friction materials with modified coconut fiber (Examples 1-4) show a trend of first increasing and then decreasing. In the range of 100℃ to 150℃, the friction coefficient of the examples containing modified coconut fiber increases slightly; as the temperature further increases, its value gradually decreases. This may be because, in the range of 100℃ to 150℃, the exposed fibers and some hard particles on the friction surface increase the friction between the friction disc and the friction material, thus manifesting as an increase in the friction coefficient; when the temperature is increased to 150℃ to 350℃, the modified coconut fiber, sepiolite fiber, and phenolic resin undergo carbonization, thereby reducing the friction coefficient through their lubricating effect.

[0094] The degradation rate F of the braking friction material is calculated as follows: F = (μF100 - μF350) / μF100 × 100%; where μF100 is the friction coefficient of the braking friction material at 100℃ during the degradation test, and μF350 is the friction coefficient of the braking friction material at 350℃ during the degradation test. The degradation rate F results of the braking friction materials obtained in each embodiment and comparative example are shown in Table 4.

[0095] The recovery test results of the braking friction materials prepared in Examples 1-4 and Comparative Example 1 are as follows: Figure 3 As shown, the friction coefficients of various braking friction materials exhibit similar trends. As the temperature decreases from 300℃ to 100℃, the friction coefficients of each braking friction material first decrease, then increase, and then decrease again. Among them, sample C-6 (Example 3) has the highest friction coefficient, and the friction coefficient of the braking friction material at this fiber content fluctuates between 0.439 and 0.461.

[0096] The fade rate R (also known as recovery rate) of braking friction materials is calculated as follows: R = μ R100 / μ F100×100% ; where μ R100 The friction coefficient of the braking friction material at 100℃ during the degradation test phase, μ F100 To restore the friction coefficient of the braking friction material at 100°C during the experimental phase, the degradation rate R of the braking friction material obtained in each embodiment and comparative example is shown in Table 4.

[0097] Figure 4 The figures show the wear rate as a function of temperature for the braking friction materials prepared in Examples 1-4 and Comparative Example 1. Figure 4It is known that the wear rate of brake friction materials is significantly affected by temperature. The wear rate increases with increasing temperature, possibly because the phenolic resin undergoes thermal decomposition at higher temperatures, weakening the bond between the components. This causes the hard filler particles, such as precipitated barium sulfate and calcium carbonate, to be detached during operation, exacerbating wear and leading to the increasing wear rate with temperature. The wear rate of the I-0 brake friction material sample (Comparative Example 1) was higher than that of brake friction material samples with other fiber contents (Examples 1-4) at all temperatures, indicating that adding modified coconut fiber can significantly improve the wear resistance of brake friction materials. The wear rate results of the brake friction materials obtained in each example and comparative example at 250°C are shown in Table 4.

[0098] Furthermore, the wear debris, hard materials, and abrasive fragments generated during the operation of braking friction materials form primary and secondary contact plateaus after compaction. Analyzing the contact plateaus, microcracks, wear debris, and deformation on the wear surface of friction materials provides a reliable basis for understanding the tribological properties of braking friction materials. In this invention, to investigate the influence of modified coconut fiber on the wear behavior of braking friction materials, scanning electron microscopy was used to detect and analyze the microstructure of the wear surface of braking friction materials with different modified coconut fibers and their varying contents. The SEM image of the braking friction material prepared in Example 1 is shown below. Figure 5 As shown, the SEM image of the braking friction material prepared in Example 2 is shown below. Figure 6 As shown, the SEM image of the braking friction material prepared in Example 3 is shown below. Figure 7 As shown, the SEM image of the braking friction material prepared in Example 4 is shown below. Figure 8 As shown, the SEM image of the braking friction material prepared in Comparative Example 1 can be found in [reference]. Figure 9 As shown.

[0099] Compared to the I-0 sample (Comparative Example 1) without modified coconut fiber, the wear surfaces of other braking friction material samples (Examples 1-4) were relatively smooth, with fewer spalling pits and wear debris. The main reason for this phenomenon is that the addition of modified coconut fiber improved the bonding between the various raw materials and created a mechanical self-locking mechanism with the matrix material, leading to improved strength and tribological properties of the braking friction material. Figures 5-9 It can be seen that as the modified coconut fiber content increases, the wear of the brake friction material samples gradually decreases. Among them, the C-6 brake friction material sample (Example 3) has the smoothest wear surface, with more secondary contact plateaus and relatively fewer wear debris and hard particles, which is consistent with the lowest wear rate data of this brake friction material. However, when the modified coconut fiber content is too high (Example 4), Figure 8Then, a certain amount of wear debris and hard particles appeared, and scratches and peeling pits appeared along the friction direction. This is mainly because the high content of modified coconut fiber reduces the bonding effect of phenolic resin binder, which reduces the strength of the entire braking friction material and makes it easy to break or fall off under the action of high temperature and shear force.

[0100] Table 4. Test results of wear rate F, wear rate R, and wear rate at 250℃ for various braking friction materials.

[0101] Understandably, a lower degradation rate F indicates better resistance to thermal degradation. A degradation rate R closer to 100% indicates better recovery performance.

[0102] As can be seen from Table 4, compared with the comparative examples, the braking friction materials obtained in each embodiment have better resistance to thermal fading and recovery performance, and lower wear rate.

[0103] However, due to the absence of modified coconut fiber, sepiolite fiber, or mineral fiber, unsuitable fiber ratios, or the use of unmodified coconut shell fiber from the king coconut tree, or the use of unsuitable fiber types, the heat fading resistance and recovery performance decreased, and the wear rate increased.

[0104] In summary, by employing specific components and controlling appropriate proportions, especially by using modified coconut fiber, sepiolite fiber, and mineral fiber in specific proportions, the present invention can improve the heat fading resistance and recovery performance of braking friction materials and reduce the wear rate through the synergistic effect of these three components.

[0105] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A braking friction material, characterized in that, It is mainly composed of the following components by weight: 1-10 parts modified coconut fiber, 3-8 parts sepiolite fiber, 17-23 parts mineral fiber, 6-12 parts phenolic resin, 5-13 parts flake graphite, 4-10 parts petroleum coke, 3-9 parts alumina, 1-3 parts friction powder, 10-16 parts calcium carbonate, 2-8 parts vermiculite powder, 15-25 parts precipitated barium sulfate, and 0.5-1.5 parts zinc stearate.

2. The braking friction material according to claim 1, characterized in that, The modified coconut fiber is 2 to 6 parts.

3. The braking friction material according to claim 1, characterized in that, The sepiolite fiber content is 4 to 6 parts.

4. The braking friction material according to claim 1, characterized in that, The mineral fiber content is 19-21 parts.

5. The braking friction material according to any one of claims 1 to 4, characterized in that, The method for preparing the modified coconut fiber includes: soaking coconut fiber in water and then crushing it, followed by drying and sieving to obtain chopped fiber; soaking the chopped fiber in an alkaline solution, reacting it, washing it, and drying it to obtain the modified coconut fiber.

6. The braking friction material according to claim 5, characterized in that, At least one of the following conditions must be met: (1) The particle size of the chopped fibers is 40~60 mesh; (2) The mass fraction of the alkaline solution is 0.5%~2%; (3) The ratio of the mass of the chopped fiber to the volume of the alkaline solution is 1:25~35 g / mL; (4) The reaction time is 30~60 min.

7. The method for preparing the braking friction material according to any one of claims 1 to 6, characterized in that, Includes the following steps: The raw materials are mixed and then hot-pressed to obtain the pressed product. The pressed product is subjected to heat treatment to obtain heat-treated material; The heat-treated material is then machined to obtain the braking friction material.

8. The method for preparing the braking friction material according to claim 7, characterized in that, At least one of the following conditions must be met: (1) The pressure of the hot pressing process is 10~15MPa; (2) The temperature of the hot pressing process is 160~180℃; (3) The total number of holding pressures in the hot pressing process is 6 times, wherein the holding pressure time for the first and second times is 3~8s, the holding pressure time for the third, fourth and fifth times is 8~13s, and the holding pressure time for the sixth time is 800~1000s; (4) The total number of venting times in the hot pressing molding process is 6, wherein the venting time for the first to fifth times is 3 to 8 seconds, and the venting time for the sixth time is 20 to 40 seconds.

9. The method for preparing the braking friction material according to claim 7, characterized in that, At least one of the following conditions must be met: (1) The heat treatment includes: first holding at 130~150℃ for 0.5~1.5h, then raising the temperature to 150~170℃ and holding for 2~4h, and finally raising the temperature to 170~190℃ and holding for 5~8h; (2) The machining includes cutting and grinding.

10. The application of the braking friction material as described in any one of claims 1 to 6 in an automotive braking system.

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