Brake pad friction material for automobile, brake pad and preparation method of brake pad

Abstract

The invention discloses a brake pad friction material for an automobile, a brake pad and a preparation method of the brake pad, and belongs to the technical field of brake pads. The brake pad friction material for the automobile comprises phenolic resin, treated aramid fibers, steel fibers, molybdenum disulfide, graphite powder, brass powder, coke powder, magnesium oxide, silicon dioxide, mica powder, barium sulfate and organic montmorillonite. The preparation method is good in operability, the comprehensive performance of the obtained disc brake pad friction material is good, and the obtained disc brake pad friction material has excellent frictional wear performance and physical performance at the same time.

Description

A friction material for automotive brake pads, brake pads, and a method for preparing brake pads. Technical Field

[0001] This invention relates to the field of brake pad technology, specifically to a friction material for automotive brake pads, brake pads, and a method for preparing brake pads. Background Technology

[0002] Automotive braking friction materials refer to the materials used in automotive braking systems that utilize their frictional properties to convert the vehicle's kinetic energy into heat energy or other forms of energy, thereby achieving braking. Traditional braking systems are mainly divided into disc brake systems and drum brake systems. Disc brake systems utilize the mechanical friction between two mating components, brake pads and brake discs, to achieve braking. Compared to drum brake systems, disc brake systems have superior heat fade performance and friction coefficient stability. Therefore, disc brake pads currently cover almost all braking systems in ordinary passenger cars, and this trend is gradually expanding.

[0003] Disc brake pad friction materials typically consist of four main parts: binder, reinforcing fibers, fillers, and friction modifiers. These four parts, through their unique properties and synergistic interactions, ensure suitable and relatively stable frictional performance and a long wear life within the operating temperature range. The binder encapsulates and bonds the reinforcing fibers, fillers, and friction modifiers together in a thin adhesive film to form the entire friction material. This ensures that the friction material can effectively transfer and balance stress under both applied loads and frictional heat. Currently, phenolic resin is the most widely used binder. The reinforcing fibers form the supporting skeleton of the friction material, ensuring sufficient mechanical strength and certain friction and wear resistance. This allows the friction material to withstand shear forces, pressures, and impacts during production and use, preventing cracking and failure. Currently, [the following text appears to be incomplete and requires further context: "currently used..."] The most widely used reinforcing fibers are organic fibers (aramid fibers, composite mineral fibers, wollastonite fibers, etc.), inorganic fibers (ceramic fibers, steel fibers, whiskers, etc.) and carbon fibers; fillers are divided into functional fillers and space fillers, which play a decisive role in the mechanical and physical properties of friction materials, such as hardness, density, noise, strength, thermal conductivity, impact toughness, and coefficient of thermal expansion; friction performance modifiers are divided into friction-increasing materials and friction-reducing materials. Among them, friction-increasing materials are also known as friction-resistant materials, and their Mohs hardness is generally above 3; friction-reducing materials include non-metallic minerals and soft metals with a Mohs hardness of 1-2 and anisotropic crystal form.

[0004] As a critical safety component in vehicle braking systems, brake pads have attracted widespread attention from research institutions and OEMs regarding the research of high-performance brake pad friction materials. High-performance brake pad friction materials not only require excellent friction and wear performance but also superior physical properties. Friction and wear performance primarily includes the coefficient of friction and wear rate; physical properties mainly include hardness, strength, thermal expansion, and high-temperature resistance. Hardness indirectly reflects the braking noise level of the brake pad friction material; low strength can lead to braking system failure and serious consequences; high thermal expansion can cause incomplete brake release, easily leading to traffic accidents; and poor high-temperature resistance can cause brake fade, affecting braking safety and reliability.

[0005] However, disc brake pad friction materials prepared according to the commonly used composition of disc brake pad friction materials generally suffer from poor overall performance, meaning they are difficult to simultaneously possess excellent friction and wear resistance and physical properties. Analysis of the composition of disc brake pad friction materials reveals the following main reasons: 1. Brake pad friction materials prepared with phenolic resin binders have excessively high hardness and poor high-temperature resistance. Currently, the common method to address this problem is to modify the phenolic resin binder. Modification methods mainly focus on modifying phenolic resin with organic compounds and using nanomaterials. However, as mentioned by Zhong Li and Chen Mengqing in their article "Research Status and Development Trends of Brake Pad Friction Materials," *Synthetic Materials Aging and Application*, December 2017, while modifying phenolic resin with organic compounds can reduce the hardness of brake pad friction materials, its effect on improving the high-temperature resistance of brake pad friction materials is limited. Although nanomaterials can improve the high-temperature resistance of brake pad friction materials, nanomaterials are prone to agglomeration, affecting the modification effect. Furthermore, as mentioned in Xu Wen, Wu Qisheng, Wu Lehua, and Zhu Huajun's article "Montmorillonite Intercalation Modified Phenolic Resin Composites and Their Tribological Properties," *Journal of Materials Science and Engineering*, April 2015, when using montmorillonite modification, in-situ intercalation polymerization of phenolic resin on montmorillonite is required, which is difficult for brake pad friction material manufacturers to operate. Secondly, single reinforcing fibers have serious defects and deficiencies in performance, making it difficult to meet the requirements of current high-performance brake pad friction materials. For example, as mentioned in Huo Chao's article "Preparation and Performance Study of Highly Dispersible Carbon Fiber Reinforced Braking Friction Materials," *Jilin University*, June 2022, aramid fibers have a large specific surface area and advantages such as low density, high strength, and good toughness, but poor dispersion performance; ceramic fibers are lightweight and have good thermal stability, but low thermal conductivity, which easily causes material breakage; steel fibers are prone to adhesive wear, resulting in serious noise problems and vibration problems caused by friction. Furthermore, the poor bonding between the reinforcing fiber and the binder significantly impacts the strength and tribological properties of friction materials. Poor bonding leads to reduced strength and tribological performance. Currently, a common approach to address this issue is chemical modification of aramid fibers. For example, as described in Gu Chenglong's "Research on Aramid Fiber / Phenolic Resin Composites" (Soochow University, May 2012), treating aramid fibers with phosphoric acid can improve the bonding force between the aramid fibers and phenolic resin. The amide bonds on the surface of aramid fibers have a strong electro-electrolytic ability, enhancing the reactivity at the ortho and meta positions. Under the influence of phosphoric acid, electrophilic substitution occurs, generating hydroxyl groups. Simultaneously, the amide bonds undergo a small amount of hydrolysis under the influence of phosphoric acid to generate more polar amino groups.However, as Li Mingzhuan, Wang Jun, Lu Shengjun, et al., "Research Status and Functional Application Progress of Aramid Fibers," *Polymer Bulletin*, January 2018, stated, while the chemical effects are significant, the degree of reaction is difficult to control. Excessive reaction can lead to damage to the internal structure of the fiber, resulting in a loss of fiber strength. Therefore, chemical modification of aramid fibers can easily damage the fiber's internal structure, further affecting its ability to enhance the strength and tribological properties of friction materials. Consequently, the enhancing effect of chemically modified aramid fibers on the strength and tribological properties of friction materials is limited.

[0006] In summary, given the composition and solutions of commonly used disc brake pad friction materials, it is difficult to obtain disc brake pad friction materials with good overall performance while ensuring good operability. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a friction material for automotive brake pads, brake pads, and a method for preparing brake pads. This method is highly operable and yields a disc brake pad friction material with excellent overall performance, meaning that the obtained disc brake pad friction material possesses both excellent friction and wear properties and physical properties.

[0008] To solve the above technical problems, the present invention adopts the following technical solution: A friction material for automotive brake pads, by weight, is composed of the following raw materials: 9.5-10 parts phenolic resin, 1.8-2 parts treated aramid fiber, 17-18 parts steel fiber, 7-7.5 parts molybdenum disulfide, 7-7.5 parts graphite powder, 3-3.2 parts brass powder, 4-4.2 parts coke powder, 4-4.2 parts magnesium oxide, 0.24-0.25 parts silicon dioxide, 3.7-4 parts mica powder, 18-20 parts barium sulfate, and 1-1.1 parts organo-modified montmorillonite; wherein the phenolic resin is phenolic resin 2123; and the steel fiber has an average length of 1.8-2.2 mm and an average diameter of 90-110 μm. The molybdenum disulfide has an average particle size of 200-300 mesh; the graphite powder has an average particle size of 180-200 mesh; the brass powder has an average particle size of 200-300 mesh; the coke powder has an average particle size of 1100-1250 mesh; the magnesium oxide has an average particle size of 1100-1250 mesh; the silicon dioxide has an average particle size of 1100-1250 mesh; the mica powder has an average particle size of 1100-1250 mesh; and the barium sulfate has an average particle size of 1100-1250 mesh. The method for preparing the treated aramid fiber is as follows: aramid fiber is mixed evenly with acetone, allowed to stand at room temperature for 12-15 hours, the aramid fiber is removed and washed with distilled water, and then mixed with a phosphoric acid aqueous solution. The aramid fibers are uniformly mixed and allowed to stand at 38-42℃ for 50-60 minutes. Then, the aramid fibers are removed and washed with distilled water until neutral. They are then mixed uniformly with a calcium chloride aqueous solution and allowed to stand at room temperature for 10-15 minutes. The aramid fibers are then removed and mixed uniformly with a chitosan acetate aqueous solution and allowed to stand at room temperature for 50-60 minutes. The aramid fibers are then removed and washed with distilled water, and dried to obtain the treated aramid fibers. In the preparation method of the treated aramid fibers, the ratio of aramid fibers to acetone is 100g:1000-1200mL; the ratio of aramid fibers to phosphoric acid aqueous solution is 100g:1000-1200mL; and the ratio of aramid fibers to calcium chloride aqueous solution is 100g:1000-1200mL. 00 mL; the ratio of aramid fiber to chitosan acetate aqueous solution is 100 g: 1000-1200 mL; the average length of the aramid fiber is 1.8-2.2 mm, and the average diameter is 11-13 μm; the mass fraction of the phosphoric acid aqueous solution is 18-22%; the mass fraction of the calcium chloride aqueous solution is 1.8-2.2%; the mass fraction of chitosan and acetic acid in the chitosan acetate aqueous solution is 1.8-2.2%; the degree of deacetylation of chitosan in the chitosan acetate aqueous solution is 85-95%; the preparation method of the organo-modified montmorillonite is to adjust the pH value of the chitosan acetate aqueous solution to 4.8-5 using sodium hydroxide aqueous solution A.2. Obtain the treated chitosan acetate aqueous solution; mix montmorillonite and distilled water, and ultrasonically disperse to obtain a montmorillonite dispersion; while stirring the montmorillonite dispersion at 58-62℃, add the chitosan acetate aqueous solution dropwise to the montmorillonite dispersion. After the addition is complete, continue stirring at 58-62℃ for 24-30 hours, filter, add the filter residue to magnesium sulfate aqueous solution, stir at room temperature for 50-60 minutes, filter, add the filter residue to sodium hydroxide aqueous solution B, stir at room temperature for 50-60 minutes, filter, take the filter residue, wash with distilled water, and dry to obtain organo-modified montmorillonite; in the preparation method of organo-modified montmorillonite, the ratio of chitosan acetate aqueous solution, montmorillonite, distilled water, magnesium sulfate aqueous solution, and sodium hydroxide aqueous solution B is 1000-1200mL:12.5-13g:500- The solution composition is as follows: 550 mL: 1000-1200 mL: 1000-1200 mL; the sodium hydroxide aqueous solution A has a mass fraction of 3.8-4.2%; the chitosan acetate aqueous solution contains 1.8-2.2% chitosan and 1.8-2.2% acetic acid; the degree of deacetylation of chitosan in the chitosan acetate aqueous solution is 85-95%; the montmorillonite is calcium-based montmorillonite with an average particle size of 200-400 mesh; the magnesium sulfate aqueous solution contains 0.9-1.1% magnesium sulfate; the sodium hydroxide aqueous solution B has a mass fraction of 0.9-1.1%; the ultrasonic dispersion is performed at room temperature, at a frequency of 20-30 kHz, and for 1.5-2 h; when adding the chitosan acetate aqueous solution dropwise to the montmorillonite dispersion, the dropping rate is 200-250 mL / h.

[0009] A brake pad includes a brake pad backing plate and the aforementioned automotive brake pad friction material.

[0010] A method for preparing brake pads involves adding all raw materials to a mixer according to the aforementioned composition of friction material for automotive brake pads. The mixing speed is controlled at 350-400 rpm, and the mixing time is controlled at 20-30 min. Then, the mixture is transferred to a press with a brake pad backing plate for hot pressing. The hot pressing temperature is controlled at 150-160℃, the hot pressing pressure is controlled at 15-18 MPa, and the hot pressing time is controlled at 250-300 s. The mixture is then transferred to a heat treatment machine for heat treatment. The heat treatment temperature is controlled at 190-200℃, and the heat treatment time is controlled at 7-8 h. Finally, the mixture is processed according to the brake pad dimensions to obtain the brake pad.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention eliminates the need for preparing phenolic resin when preparing brake pad friction materials, thus improving operability. Furthermore, the resulting disc brake pad friction material exhibits excellent overall performance, specifically as follows: the brake pads prepared from the disc brake pad friction material have a friction coefficient of 0.43-0.45 at 100℃, 0.47-0.49 at 150℃, 0.50-0.53 at 200℃, 0.52-0.55 at 250℃, 0.45-0.49 at 300℃, and 0.41-0.44 at 350℃; the wear rate at 100℃ is (0.11-0.12)×10⁻¹⁰. -7 cm 3 / (N•m), the wear rate at 150℃ is (0.14-0.16)×10 -7 cm 3 / (N•m), the wear rate at 200℃ is (0.21-0.24)×10 -7 cm 3 / (N•m), the wear rate at 250℃ is (0.34-0.38)×10 -7 cm 3 / (N•m), the wear rate at 300℃ is (0.54-0.59)×10 -7 cm 3 / (N•m), the wear rate at 350℃ is (0.62-0.64)×10 - 7 cm 3 / (N•m); Hardness (HRL) is 93.2-94.5, and impact strength is 6.78-6.93kJ / m. 2 The coefficient of thermal expansion (400℃) is 0.40-0.42%. Detailed Implementation

[0012] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described.

[0013] Example 1 This example provides a friction material for automotive brake pads, which, by weight, is composed of the following raw materials: 9.5 parts phenolic resin, 1.8 parts treated aramid fiber, 17 parts steel fiber, 7 parts molybdenum disulfide, 7 parts graphite powder, 3 parts brass powder, 4 parts coke powder, 4 parts magnesium oxide, 0.24 parts silicon dioxide, 3.7 parts mica powder, 18 parts barium sulfate, and 1 part organo-modified montmorillonite; the phenolic resin is phenolic resin 2123; the steel fiber has an average length of 2 mm and an average diameter of 100 μm; the molybdenum disulfide has an average particle size of 200 mesh. The graphite powder has an average particle size of 180 mesh; the brass powder has an average particle size of 200 mesh; the coke powder has an average particle size of 1100 mesh; the magnesium oxide has an average particle size of 1100 mesh; the silicon dioxide has an average particle size of 1100 mesh; the mica powder has an average particle size of 1250 mesh; the barium sulfate has an average particle size of 1250 mesh; the preparation method of the treated aramid fiber is as follows: 100g of aramid fiber is mixed evenly with 1000mL of acetone, left to stand at room temperature for 12h, the aramid fiber is then removed and treated with 800mL of distilled water. The aramid fibers were cleaned, mixed thoroughly with 1000 mL of phosphoric acid aqueous solution, and allowed to stand at 40°C for 50 min. The aramid fibers were then removed and washed with distilled water until neutral. The mixture was then mixed thoroughly with 1000 mL of calcium chloride aqueous solution and allowed to stand at room temperature for 10 min. The aramid fibers were then removed and mixed thoroughly with 1000 mL of chitosan acetate aqueous solution and allowed to stand at room temperature for 50 min. The aramid fibers were then removed and washed with 400 mL of distilled water, and dried to obtain the treated aramid fibers. The average length of the aramid fibers was 2 mm, and the average diameter was 12 μm. The mass of the phosphoric acid aqueous solution was... The mass fraction of the chitosan acetate aqueous solution is 20%; the mass fraction of the chitosan acetate aqueous solution is 2%, and the mass fraction of the acetic acid is 2%; the degree of deacetylation of the chitosan acetate aqueous solution is 90%; the preparation method of the organo-modified montmorillonite is as follows: the pH value of 1000 mL of chitosan acetate aqueous solution is adjusted to 5 using sodium hydroxide aqueous solution A to obtain the treated chitosan acetate aqueous solution; 12.5 g of montmorillonite and 500 mL of distilled water are mixed and ultrasonically dispersed at a frequency of 20 kHz at room temperature.After 5 hours, a montmorillonite dispersion was obtained. While stirring the entire montmorillonite dispersion at 60°C, the entire treated chitosan-acetic acid aqueous solution was added dropwise to the entire montmorillonite dispersion at a rate controlled at 200 mL / h. After the addition was complete, stirring continued at 60°C for 24 hours. The mixture was filtered, and the filter residue was added to 1000 mL of magnesium sulfate aqueous solution. The mixture was stirred at room temperature for 50 minutes, filtered again, and then added to 1000 mL of sodium hydroxide aqueous solution B. The mixture was stirred at room temperature for 50 minutes, filtered again, and the filter residue was collected, washed with 80 mL of distilled water, and dried to obtain organo-modified montmorillonite. The sodium hydroxide aqueous solution A had a mass fraction of 4%; the chitosan-acetic acid aqueous solution contained 2% chitosan and 2% acetic acid; the degree of deacetylation of chitosan in the chitosan-acetic acid aqueous solution was 90%; the montmorillonite was calcium-based montmorillonite with an average particle size of 300 mesh; the magnesium sulfate aqueous solution had a mass fraction of 1%; and the sodium hydroxide aqueous solution B had a mass fraction of 1%.

[0014] This embodiment also provides a brake pad, comprising a brake pad backing plate and the aforementioned automotive brake pad friction material.

[0015] This embodiment also provides a method for preparing brake pads, as follows: According to the aforementioned raw material composition of automotive brake pad friction material, all raw materials are added to a mixer for mixing. The mixing speed is controlled at 350 rpm and the mixing time is controlled at 20 min. Then, the mixture is transferred to a press with a brake pad backing plate for hot pressing. The hot pressing temperature is controlled at 150°C, the hot pressing pressure is controlled at 15 MPa, and the hot pressing time is controlled at 250 s. The mixture is then transferred to a heat treatment machine for heat treatment. The heat treatment temperature is controlled at 190°C and the heat treatment time is controlled at 7 h. Finally, the mixture is processed according to the brake pad dimensions to obtain the brake pad.

[0016] Example 2 This example provides a friction material for automotive brake pads, which, by weight, is composed of the following raw materials: 9.5 parts phenolic resin, 2 parts treated aramid fiber, 17 parts steel fiber, 7 parts molybdenum disulfide, 7 parts graphite powder, 3 parts brass powder, 4 parts coke powder, 4 parts magnesium oxide, 0.24 parts silicon dioxide, 3.7 parts mica powder, 18 parts barium sulfate, and 1 part organo-modified montmorillonite; the phenolic resin is phenolic resin 2123; the steel fiber has an average length of 2 mm and an average diameter of 100 μm; the molybdenum disulfide has an average particle size of 200 mesh; The graphite powder has an average particle size of 180 mesh; the brass powder has an average particle size of 200 mesh; the coke powder has an average particle size of 1100 mesh; the magnesium oxide has an average particle size of 1100 mesh; the silicon dioxide has an average particle size of 1100 mesh; the mica powder has an average particle size of 1250 mesh; the barium sulfate has an average particle size of 1250 mesh; the preparation method of the treated aramid fiber is as follows: 100g of aramid fiber is mixed evenly with 1000mL of acetone, allowed to stand at room temperature for 12h, the aramid fiber is then removed and rinsed with 800mL of distilled water. The aramid fibers were washed and mixed thoroughly with 1000 mL of phosphoric acid aqueous solution, and allowed to stand at 40°C for 50 min. The aramid fibers were then removed and washed with distilled water until neutral. The mixture was then mixed thoroughly with 1000 mL of calcium chloride aqueous solution, and allowed to stand at room temperature for 10 min. The aramid fibers were then removed and mixed thoroughly with 1000 mL of chitosan acetate aqueous solution, and allowed to stand at room temperature for 50 min. The aramid fibers were then removed and washed with 400 mL of distilled water, and dried to obtain the treated aramid fibers. The average length of the aramid fibers was 2 mm, and the average diameter was 12 μm. The mass of the phosphoric acid aqueous solution was... The mass fraction of the chitosan acetate aqueous solution is 20%; the mass fraction of the chitosan acetate aqueous solution is 2%, and the mass fraction of the acetic acid is 2%; the degree of deacetylation of the chitosan acetate aqueous solution is 90%; the preparation method of the organo-modified montmorillonite is as follows: the pH value of 1000 mL of chitosan acetate aqueous solution is adjusted to 5 using sodium hydroxide aqueous solution A to obtain the treated chitosan acetate aqueous solution; 12.5 g of montmorillonite and 500 mL of distilled water are mixed and ultrasonically dispersed at a frequency of 20 kHz at room temperature.After 5 hours, a montmorillonite dispersion was obtained. While stirring the entire montmorillonite dispersion at 60°C, the entire treated chitosan-acetic acid aqueous solution was added dropwise to the entire montmorillonite dispersion at a rate controlled at 200 mL / h. After the addition was complete, stirring continued at 60°C for 24 hours. The mixture was filtered, and the filter residue was added to 1000 mL of magnesium sulfate aqueous solution. The mixture was stirred at room temperature for 50 minutes, filtered again, and then added to 1000 mL of sodium hydroxide aqueous solution B. The mixture was stirred at room temperature for 50 minutes, filtered again, and the filter residue was collected, washed with 80 mL of distilled water, and dried to obtain organo-modified montmorillonite. The sodium hydroxide aqueous solution A had a mass fraction of 4%; the chitosan-acetic acid aqueous solution contained 2% chitosan and 2% acetic acid; the degree of deacetylation of chitosan in the chitosan-acetic acid aqueous solution was 90%; the montmorillonite was calcium-based montmorillonite with an average particle size of 300 mesh; the magnesium sulfate aqueous solution had a mass fraction of 1%; and the sodium hydroxide aqueous solution B had a mass fraction of 1%.

[0017] This embodiment also provides a brake pad, comprising a brake pad backing plate and the aforementioned automotive brake pad friction material.

[0018] This embodiment also provides a method for preparing brake pads, as follows: According to the aforementioned raw material composition of automotive brake pad friction material, all raw materials are added to a mixer for mixing. The mixing speed is controlled at 350 rpm and the mixing time is controlled at 20 min. Then, the mixture is transferred to a press with a brake pad backing plate for hot pressing. The hot pressing temperature is controlled at 150°C, the hot pressing pressure is controlled at 15 MPa, and the hot pressing time is controlled at 250 s. The mixture is then transferred to a heat treatment machine for heat treatment. The heat treatment temperature is controlled at 190°C and the heat treatment time is controlled at 7 h. Finally, the mixture is processed according to the brake pad dimensions to obtain the brake pad.

[0019] Example 3 This example provides a friction material for automotive brake pads, which, by weight, is composed of the following raw materials: 10 parts phenolic resin, 2 parts treated aramid fiber, 18 parts steel fiber, 7.5 parts molybdenum disulfide, 7.5 parts graphite powder, 3.2 parts brass powder, 4.2 parts coke powder, 4.2 parts magnesium oxide, 0.The mixture comprises 25 parts silica, 4 parts mica powder, 20 parts barium sulfate, and 1 part organo-modified montmorillonite; the phenolic resin is phenolic resin 2123; the steel fiber has an average length of 2 mm and an average diameter of 100 μm; the molybdenum disulfide has an average particle size of 200 mesh; the graphite powder has an average particle size of 180 mesh; the brass powder has an average particle size of 200 mesh; the coke powder has an average particle size of 1100 mesh; the magnesium oxide has an average particle size of 1100 mesh; the silica has an average particle size of 1100 mesh; the mica powder has an average particle size of 1250 mesh; and the barium sulfate has an average particle size of 1250 mesh. The preparation method of the treated aramid fiber is as follows: 100 g of aramid fiber is mixed evenly with 1200 mL of acetone. After standing at room temperature for 15 hours, the aramid fibers were removed and washed with 1000 mL of distilled water. They were then mixed thoroughly with 1200 mL of phosphoric acid aqueous solution and allowed to stand at 40°C for 60 minutes. The aramid fibers were then removed and washed with distilled water until neutral. They were then mixed thoroughly with 1200 mL of calcium chloride aqueous solution and allowed to stand at room temperature for 15 minutes. The aramid fibers were then removed and mixed thoroughly with 1200 mL of chitosan acetate aqueous solution and allowed to stand at room temperature for 60 minutes. The aramid fibers were then removed and washed with 500 mL of distilled water and dried to obtain the treated aramid fibers. The average length of the aramid fibers was 2 mm, and the average diameter was 12 μm. The mass fraction of the phosphoric acid aqueous solution was 20%, the mass fraction of the calcium chloride aqueous solution was 2%, and the mass fraction of the chitosan acetate solution was... The aqueous solution contains 2% chitosan and 2% acetic acid by mass; the degree of deacetylation of chitosan in the chitosan-acetic acid aqueous solution is 90%; the preparation method of the organo-modified montmorillonite is as follows: the pH of 1200 mL of chitosan-acetic acid aqueous solution is adjusted to 5 using sodium hydroxide aqueous solution A to obtain the treated chitosan-acetic acid aqueous solution; 13 g of montmorillonite and 550 mL of distilled water are mixed and ultrasonically dispersed at 30 kHz for 2 h at room temperature to obtain a montmorillonite dispersion; while stirring the entire obtained montmorillonite dispersion at 60 °C, the entire obtained treated chitosan-acetic acid aqueous solution is added dropwise to the entire obtained montmorillonite dispersion, and the dropping rate is controlled at 250 mL / h. After the addition is complete... Continue stirring at 60℃ for 30 hours, filter, add the filter residue to 1200 mL of magnesium sulfate aqueous solution, stir for 60 minutes at room temperature, filter, add the filter residue to 1200 mL of sodium hydroxide aqueous solution B, stir for 60 minutes at room temperature, filter, take the filter residue, wash with 100 mL of distilled water, and dry to obtain organo-modified montmorillonite; the mass fraction of sodium hydroxide aqueous solution A is 4%; the mass fraction of chitosan in the chitosan acetate aqueous solution is 2%, and the mass fraction of acetic acid is 2%; the degree of deacetylation of chitosan in the chitosan acetate aqueous solution is 90%; the montmorillonite is calcium-based montmorillonite with an average particle size of 300 mesh; the mass fraction of magnesium sulfate aqueous solution is 1%; the mass fraction of sodium hydroxide aqueous solution B is 1%.

[0020] This embodiment also provides a brake pad, comprising a brake pad backing plate and the aforementioned automotive brake pad friction material.

[0021] This embodiment also provides a method for preparing brake pads, as follows: According to the aforementioned raw material composition of automotive brake pad friction material, all raw materials are added to a mixer for mixing. The mixing speed is controlled at 400 rpm and the mixing time is controlled at 30 min. Then, the mixture is transferred to a press with a brake pad backing plate for hot pressing. The hot pressing temperature is controlled at 160°C, the hot pressing pressure is controlled at 18 MPa, and the hot pressing time is controlled at 300 s. The mixture is then transferred to a heat treatment machine for heat treatment. The heat treatment temperature is controlled at 200°C and the heat treatment time is controlled at 8 h. Finally, the mixture is processed according to the brake pad dimensions to obtain the brake pad.

[0022] Example 4 This example provides a friction material for automotive brake pads, which, by weight, is composed of the following raw materials: 10 parts phenolic resin, 2 parts treated aramid fiber, 18 parts steel fiber, 7.5 parts molybdenum disulfide, 7.5 parts graphite powder, 3.2 parts brass powder, 4.2 parts coke powder, 4.2 parts magnesium oxide, 0.25 parts silicon dioxide, 4 parts mica powder, 20 parts barium sulfate, 1.One part of organic montmorillonite; the phenolic resin is phenolic resin 2123; the steel fiber has an average length of 2 mm and an average diameter of 100 μm; the molybdenum disulfide has an average particle size of 200 mesh; the graphite powder has an average particle size of 180 mesh; the brass powder has an average particle size of 200 mesh; the coke powder has an average particle size of 1100 mesh; the magnesium oxide has an average particle size of 1100 mesh; the silicon dioxide has an average particle size of 1100 mesh; the mica powder has an average particle size of 1250 mesh; the barium sulfate has an average particle size of 1250 mesh; the preparation method of the treated aramid fiber is as follows: 100 g of aramid fiber is mixed evenly with 1200 mL of acetone, left to stand at room temperature for 15 h, and then the aramid fiber is removed. The aramid fibers were washed with 1000 mL of distilled water, mixed thoroughly with 1200 mL of phosphoric acid aqueous solution, and allowed to stand at 40°C for 60 min. The aramid fibers were then removed and washed with distilled water until neutral, mixed thoroughly with 1200 mL of calcium chloride aqueous solution, and allowed to stand at room temperature for 15 min. The aramid fibers were then removed and mixed thoroughly with 1200 mL of chitosan acetate aqueous solution, allowed to stand at room temperature for 60 min, and then washed with 500 mL of distilled water and dried to obtain the treated aramid fibers. The average length of the aramid fibers was 2 mm, and the average diameter was 12 μm. The mass fraction of the phosphoric acid aqueous solution was 20%, the mass fraction of the calcium chloride aqueous solution was 2%, and the mass fraction of chitosan in the chitosan acetate aqueous solution was [not specified]. The mass fraction of the chitosan acetate solution is 2%, and the mass fraction of the acetic acid solution is 2%. The degree of deacetylation of chitosan in the chitosan acetate aqueous solution is 90%. The preparation method of the organo-modified montmorillonite is as follows: the pH value of 1200 mL of chitosan acetate aqueous solution is adjusted to 5 using sodium hydroxide aqueous solution A to obtain the treated chitosan acetate aqueous solution; 13 g of montmorillonite and 550 mL of distilled water are mixed and ultrasonically dispersed at a frequency of 30 kHz for 2 h at room temperature to obtain a montmorillonite dispersion; while stirring the entire obtained montmorillonite dispersion at 60 °C, the entire obtained treated chitosan acetate aqueous solution is added dropwise to the entire obtained montmorillonite dispersion, and the dropping rate is controlled at 250 mL / h. After the addition is completed, the mixture is stirred at 60 °C. Stirred at ℃ for 30 h, filtered, and the filter residue was added to 1200 mL of magnesium sulfate aqueous solution, stirred at room temperature for 60 min, filtered again, and the filter residue was added to 1200 mL of sodium hydroxide aqueous solution B, stirred at room temperature for 60 min, filtered again, and the filter residue was collected, washed with 100 mL of distilled water, and dried to obtain organo-modified montmorillonite; the mass fraction of sodium hydroxide aqueous solution A was 4%; the mass fraction of chitosan in the chitosan acetate aqueous solution was 2%, and the mass fraction of acetic acid was 2%; the degree of deacetylation of chitosan in the chitosan acetate aqueous solution was 90%; the montmorillonite was calcium-based montmorillonite with an average particle size of 300 mesh; the mass fraction of magnesium sulfate aqueous solution was 1%; and the mass fraction of sodium hydroxide aqueous solution B was 1%.

[0023] This embodiment also provides a brake pad, comprising a brake pad backing plate and the aforementioned automotive brake pad friction material.

[0024] This embodiment also provides a method for preparing brake pads, as follows: According to the aforementioned raw material composition of automotive brake pad friction material, all raw materials are added to a mixer for mixing. The mixing speed is controlled at 400 rpm and the mixing time is controlled at 30 min. Then, the mixture is transferred to a press with a brake pad backing plate for hot pressing. The hot pressing temperature is controlled at 160°C, the hot pressing pressure is controlled at 18 MPa, and the hot pressing time is controlled at 300 s. The mixture is then transferred to a heat treatment machine for heat treatment. The heat treatment temperature is controlled at 200°C and the heat treatment time is controlled at 8 h. Finally, the mixture is processed according to the brake pad dimensions to obtain the brake pad.

[0025] Based on the technical solution of Example 1, the preparation method of the treated aramid fiber in Example 1 was modified as follows: 100g of aramid fiber was mixed evenly with 1000mL of acetone and allowed to stand at room temperature for 12h. The aramid fiber was then removed and washed with 800mL of distilled water, mixed evenly with 1000mL of calcium chloride aqueous solution, allowed to stand at room temperature for 10min, removed and mixed evenly with 1000mL of chitosan acetate aqueous solution, allowed to stand at room temperature for 50min, removed and washed with 400mL of distilled water, and dried to obtain the treated aramid fiber. The average length of the aramid fiber was 2mm and the average diameter was 12μm. The mass fraction of the calcium chloride aqueous solution was 2%. The mass fraction of chitosan in the chitosan acetate aqueous solution was 2%, and the mass fraction of acetic acid was 2%. The degree of deacetylation of chitosan in the chitosan acetate aqueous solution was 90%.

[0026] The remaining technical solutions are consistent with those in Example 1.

[0027] Comparative Example 2, based on the technical solution of Example 1, modifies the preparation method of the treated aramid fiber in Example 1 as follows: 100g of aramid fiber is mixed evenly with 1000mL of acetone and allowed to stand at room temperature for 12h. The aramid fiber is then removed and washed with 800mL of distilled water, mixed evenly with 1000mL of phosphoric acid aqueous solution, and allowed to stand at 40℃ for 50min. The aramid fiber is then removed and washed with distilled water until neutral, mixed evenly with 1000mL of chitosan acetate aqueous solution, and allowed to stand at room temperature for 50min. The aramid fiber is then removed and washed with 400mL of distilled water, and dried to obtain the treated aramid fiber. The average length of the aramid fiber is 2mm, and the average diameter is 12μm. The mass fraction of the phosphoric acid aqueous solution is 20%. The mass fraction of chitosan in the chitosan acetate aqueous solution is 2%, and the mass fraction of acetic acid is 2%. The degree of deacetylation of chitosan in the chitosan acetate aqueous solution is 90%.

[0028] The remaining technical solutions are consistent with those in Example 1.

[0029] Comparative Example 3, based on the technical solution of Example 1, modifies the preparation method of the treated aramid fiber in Example 1 as follows: 100g of aramid fiber is mixed evenly with 1000mL of acetone and allowed to stand at room temperature for 12h. The aramid fiber is then removed and washed with 800mL of distilled water, mixed evenly with 1000mL of phosphoric acid aqueous solution, and allowed to stand at 40℃ for 50min. The aramid fiber is then removed and washed with distilled water until neutral, mixed evenly with 1000mL of 2% calcium chloride aqueous solution, and allowed to stand at room temperature for 10min. The aramid fiber is then removed and washed with 400mL of distilled water, and dried to obtain the treated aramid fiber. The average length of the aramid fiber is 2mm and the average diameter is 12μm. The mass fraction of the phosphoric acid aqueous solution is 20%.

[0030] The remaining technical solutions are consistent with those in Example 1.

[0031] Comparative Example 4, based on the technical solution of Example 1, modifies the preparation method of the treated aramid fiber in Example 1 as follows: 100g of aramid fiber is mixed evenly with 1000mL of acetone, left to stand at room temperature for 12h, the aramid fiber is taken out and washed with 800mL of distilled water, and dried to obtain the treated aramid fiber; the average length of the aramid fiber is 2mm and the average diameter is 12μm.

[0032] The remaining technical solutions are consistent with those in Example 1.

[0033] Comparative Example 5, based on the technical solution of Example 1, modifies the preparation method of the organic montmorillonite in Example 1 as follows: The pH of 1000 mL of chitosan acetate aqueous solution is adjusted to 5 using sodium hydroxide aqueous solution to obtain the treated chitosan acetate aqueous solution; 12.5 g of montmorillonite and 500 mL of distilled water are mixed and ultrasonically dispersed at a frequency of 20 kHz for 1.5 h at room temperature to obtain a montmorillonite dispersion; while stirring the montmorillonite dispersion at 60 °C, all the obtained treated chitosan acetate aqueous solution is added dropwise. The sodium hydroxide solution was added to the obtained montmorillonite dispersion, and the dropping rate was controlled at 200 mL / h. After the addition was completed, the mixture was stirred at 60 °C for 24 h. The mixture was then filtered, and the filter residue was washed with 80 mL of distilled water and dried to obtain organo-modified montmorillonite. The sodium hydroxide aqueous solution had a mass fraction of 4%. The chitosan acetate aqueous solution had a mass fraction of 2% chitosan and 2% acetic acid. The degree of deacetylation of chitosan in the chitosan acetate aqueous solution was 90%. The montmorillonite was calcium-based montmorillonite with an average particle size of 300 mesh.

[0034] The remaining technical solutions are consistent with those in Example 1.

[0035] Comparative Example 6 is based on the technical solution of Example 1, except that the organic montmorillonite used in Example 1 is replaced with calcium-based montmorillonite with an average particle size of 300 mesh.

[0036] The remaining technical solutions are consistent with those in Example 1.

[0037] The test examples examined the friction and wear properties and physical properties of the brake pads obtained in Examples 1-4 and Comparative Examples 1-6. Specific indicators included the coefficient of friction at 100℃, 150℃, 200℃, 250℃, 300℃, and 350℃; wear rate at 100℃, 150℃, 200℃, 250℃, 300℃, and 350℃; hardness; impact strength; and coefficient of thermal expansion. For the coefficient of friction and wear rate tests, the standard GB 5763-2018 was followed, with a friction disc rotation speed of 480 rpm and a friction area of ​​25 mm × 25 mm. The impact strength test was conducted according to GB / T 33835-2017. The coefficient of thermal expansion test was conducted according to GB / T... Tested according to the 22310-2023 standard; the final test results are as follows:

[0038] The results in the table above show that the brake pads obtained in Examples 1-6 have worse friction and wear properties and physical properties than those obtained in Examples 1-4.

[0039] Compared with Example 1, in the preparation method of the treated aramid fiber, Comparative Example 1 did not use an aqueous solution of phosphoric acid to treat the aramid fiber; in the preparation method of the treated aramid fiber, Comparative Example 2 did not use an aqueous solution of calcium chloride to treat the aramid fiber; in the preparation method of the treated aramid fiber, Comparative Example 3 did not use an aqueous solution of chitosan acetate to treat the aramid fiber; in the preparation method of the treated aramid fiber, Comparative Example 4 did not use an aqueous solution of phosphoric acid, an aqueous solution of calcium chloride, or an aqueous solution of chitosan acetate to treat the aramid fiber; in the preparation method of the organo-modified montmorillonite, Comparative Example 5 did not use an aqueous solution of magnesium sulfate and an aqueous solution of sodium hydroxide to treat the montmorillonite; and in the preparation method of the organo-modified montmorillonite, Comparative Example 6 did not use an aqueous solution of chitosan acetate, an aqueous solution of magnesium sulfate, or an aqueous solution of sodium hydroxide to treat the montmorillonite.

[0040] Analysis revealed that the preparation method of the treated aramid fibers involved first cleaning the aramid fibers with acetone to promote their dispersion, then treating them with a phosphoric acid aqueous solution (hydrolysis). During hydrolysis, amino and hydroxyl groups appeared on the aramid surface. Next, the aramid fibers were treated with a calcium chloride aqueous solution, where calcium ions bound to the aramid fiber surface through interaction with the amino and hydroxyl groups. Finally, the aramid fibers were treated with a chitosan acetate aqueous solution, where chitosan bound to the aramid fiber surface through interaction with calcium ions. Through layer-by-layer self-assembly, a layer of chitosan was coated onto the aramid fiber surface. Chitosan can improve the dispersion of aramid fibers in phenolic resin and the bonding force between the aramid fibers and the phenolic resin, further improving the friction and wear performance and physical properties of the resulting brake pads.

[0041] In the preparation method of organo-modified montmorillonite, the chitosan-montmorillonite intercalation composite material was first prepared according to the method described in Zhang Lina, Zhang Qian, Sun Shanshan, et al., "Study on the Preparation of Methotrexate Sustained-Release Microspheres and Their In Vitro Release from Chitosan-Montmorillonite Intercalation Composite Material". Chinese Pharmaceutical Journal, December 2017. Then, according to the method described in Fu Minglian, Chen Zhangxu, Zheng Bingyun, et al., "Study on Treatment of Simulated Printing and Dyeing Wastewater with Magnesium Hydroxide / Chitosan Composite Flocculant". New Chemical Materials, October 2014. The chitosan-montmorillonite intercalation composite material was further compounded with magnesium hydroxide to obtain a chitosan, montmorillonite, and magnesium hydroxide composite material. First, chitosan can interact with phenolic resin through phase... The interaction between magnesium hydroxide and phenolic resin enhances the heat resistance of the phenolic resin. Furthermore, according to Chen Yuzhu, Chu Fuxiang, Fan Dongbin, et al., Research on Composite Phenolic Resin Curing Agents, Journal of Nanjing Forestry University (Natural Science Edition), January 2015, the orientation effect of magnesium hydroxide on the phenolic structure can improve the reactivity between the less reactive ortho-position groups in the phenolic resin. Therefore, through the interaction between magnesium hydroxide and phenolic resin, organic montmorillonite is incorporated into the phenolic resin, thereby improving the heat resistance of the phenolic resin. Simultaneously, it also enhances the bonding force between the phenolic resin and montmorillonite, further improving the friction and wear performance and physical properties of the resulting brake pads.

Claims

1. A friction material for automotive brake pads, characterized in that, The product, by weight, comprises the following raw materials: 9.5-10 parts phenolic resin, 1.8-2 parts treated aramid fiber, 17-18 parts steel fiber, 7-7.5 parts molybdenum disulfide, 7-7.5 parts graphite powder, 3-3.2 parts brass powder, 4-4.2 parts coke powder, 4-4.2 parts magnesium oxide, 0.24-0.25 parts silicon dioxide, 3.7-4 parts mica powder, 18-20 parts barium sulfate, and 1-1.1 parts organo-modified montmorillonite. The method for preparing the treated aramid fiber is as follows: aramid fiber is mixed evenly with acetone, allowed to stand at room temperature, removed and washed, mixed evenly with a phosphoric acid aqueous solution, allowed to stand at 38-42°C, removed and washed, mixed evenly with a calcium chloride aqueous solution, and allowed to stand at room temperature. The aramid fibers were removed, mixed evenly with a chitosan acetate aqueous solution, allowed to stand at room temperature, removed, washed, and dried to obtain the treated aramid fibers. The preparation method of the organo-modified montmorillonite was as follows: the pH value of the chitosan acetate aqueous solution was adjusted to 4.8-5.2 to obtain the treated chitosan acetate aqueous solution; montmorillonite and distilled water were mixed and ultrasonically dispersed to obtain a montmorillonite dispersion; the montmorillonite dispersion was stirred at 58-62℃, the chitosan acetate aqueous solution was added dropwise to the montmorillonite dispersion, stirred at 58-62℃, filtered, the filter residue was added to a magnesium sulfate aqueous solution, stirred at room temperature, filtered, the filter residue was added to a sodium hydroxide aqueous solution, stirred at room temperature, filtered, the filter residue was taken, washed, and dried to obtain the organo-modified montmorillonite.

2. The friction material for automotive brake pads according to claim 1, characterized in that, The phenolic resin is phenolic resin 2123; the steel fiber has an average length of 1.8-2.2 mm and an average diameter of 90-110 μm.

3. The friction material for automotive brake pads according to claim 1, characterized in that, The molybdenum disulfide has an average particle size of 200-300 mesh; the graphite powder has an average particle size of 180-200 mesh; the brass powder has an average particle size of 200-300 mesh; the coke powder has an average particle size of 1100-1250 mesh; the magnesium oxide has an average particle size of 1100-1250 mesh; the silicon dioxide has an average particle size of 1100-1250 mesh; the mica powder has an average particle size of 1100-1250 mesh; and the barium sulfate has an average particle size of 1100-1250 mesh.

4. The friction material for automotive brake pads according to claim 1, characterized in that, In the method for preparing the treated aramid fiber, the ratio of aramid fiber to acetone is 100g:1000-1200mL; the ratio of aramid fiber to phosphoric acid aqueous solution is 100g:1000-1200mL; the ratio of aramid fiber to calcium chloride aqueous solution is 100g:1000-1200mL; and the ratio of aramid fiber to chitosan acetate aqueous solution is 100g:1000-1200mL.

5. The friction material for automotive brake pads according to claim 1, characterized in that, In the method for preparing the treated aramid fiber, the average length of the aramid fiber is 1.8-2.2 mm, and the average diameter is 11-13 μm; the mass fraction of the phosphoric acid aqueous solution is 18-22%; the mass fraction of the calcium chloride aqueous solution is 1.8-2.2%; the mass fraction of chitosan in the chitosan acetate aqueous solution is 1.8-2.2%, and the mass fraction of acetic acid is 1.8-2.2%; the degree of deacetylation of chitosan in the chitosan acetate aqueous solution is 85-95%.

6. The friction material for automotive brake pads according to claim 1, characterized in that, In the preparation method of the organic montmorillonite, the ratio of chitosan acetate aqueous solution, montmorillonite, distilled water, magnesium sulfate aqueous solution, and sodium hydroxide aqueous solution is 1000-1200mL:12.5-13g:500-550mL:1000-1200mL:1000-1200mL.

7. The friction material for automotive brake pads according to claim 1, characterized in that, In the preparation method of the organo-modified montmorillonite, the chitosan-acetic acid aqueous solution contains 1.8-2.2% chitosan by mass and 1.8-2.2% acetic acid by mass; the degree of deacetylation of chitosan in the chitosan-acetic acid aqueous solution is 85-95%; the montmorillonite is calcium-based montmorillonite with an average particle size of 200-400 mesh; the magnesium sulfate aqueous solution contains 0.9-1.1% magnesium sulfate by mass; the sodium hydroxide aqueous solution contains 0.9-1.1% sodium hydroxide by mass; the ultrasonic dispersion is performed at room temperature, at a frequency of 20-30 kHz, and for 1.5-2 h; when the chitosan-acetic acid aqueous solution is added dropwise to the montmorillonite dispersion, the dropping rate is 200-250 mL / h.

8. A brake pad, characterized in that, It includes a brake pad backing plate and the friction material for automotive brake pads as described in any one of claims 1-7.

9. A method for preparing brake pads, characterized in that, According to the raw material composition of the automotive brake pad friction material as described in any one of claims 1-7, all raw materials are added to a mixer and mixed at room temperature. The mixture is then transferred to a press with the brake pad backing plate for hot pressing. The hot pressing temperature is controlled to 150-160℃, the hot pressing pressure is controlled to 15-18MPa, and the hot pressing time is controlled to 250-300s. The mixture is then transferred to a heat treatment machine for heat treatment. The heat treatment temperature is controlled to 190-200℃, and the heat treatment time is controlled to 7-8h. The mixture is then processed according to the brake pad dimensions to obtain the brake pad.

Images