Composite material for brake pads and method for producing the same

Abstract

The application discloses a composite material for brake pads and a preparation method thereof, and comprises the following raw materials in parts by weight: modified phenolic resin 15-20 parts, modified composite fiber 12-16 parts, aramid fiber 4-7 parts, rubber powder 5-8 parts, steel fiber 3-5 parts, graphite 6-9 parts, modified sepiolite 4-6 parts, aluminum oxide 3-5 parts, silicon carbide 2-3 parts, vermiculite 4-6 parts, potassium titanate whisker 9-13 parts, and barium sulfate 8-11 parts. The modified composite fiber is prepared by mixing basalt fiber and carbon fiber, coating lanthanum gadolinium oxide on the surface through hydrothermal reaction, modifying with silane, and finally reacting with 4,5-diamino-2,6-dimercapto pyrimidine. The composite material for brake pads has good high-temperature resistance and friction performance, and also has excellent wear resistance and low noise, thereby prolonging the service life of the brake pad.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite materials, and particularly relates to a composite material for brake pads and a preparation method thereof. BACKGROUND

[0002] Brake pads are also called brake linings. In the brake system of an automobile, brake pads are the most critical safety parts, and all the effects of braking are determined by the brake pads. Generally, a brake pad is composed of a steel plate, a heat insulation layer and a friction block. The friction block is composed of a friction material and a binder, and is pressed against a brake disc or a brake drum to generate friction during braking, so as to achieve the purpose of vehicle deceleration and braking. Due to the friction, the friction block will be gradually worn out. Generally speaking, the lower the cost of the brake pad, the faster the wear. During emergency braking, the brake pad and the brake disc / brake drum rub against each other violently, which generates a large amount of heat and grinding dust. If the heat generated cannot be cooled in time, the local temperature of the brake pad will be too high to cause oxidation, which greatly reduces the braking performance of the brake pad and affects the safety of driving. In addition, cracks are easily generated due to material fatigue under the action of contact stress, which further damages the surface of the brake pad / brake drum.

[0003] Traditional automobile brake pad friction blocks usually use asbestos friction materials, semi-metallic friction materials or non-asbestos organic friction materials. Due to the unstable high-temperature friction performance, large braking noise, short service life and strong carcinogenicity of asbestos brake pads, they have been replaced by semi-metallic and non-asbestos organic friction materials. However, most of the current semi-metallic and non-asbestos brake pads cannot completely adapt to complex and harsh braking conditions and higher environmental protection requirements, especially in high-speed and heavy-load braking conditions. Semi-metallic brake pads have the problems of large braking noise, easy damage to the mating part, easy rust and easy friction performance degradation. Non-asbestos brake pads release harmful gases and are prone to thermal degradation after high-temperature friction, which causes braking failure and leads to major safety accidents, causing huge economic losses to people. The existing brake pad friction materials gradually achieve the effect of excellent performance of some brake pads by changing and adding various components, but they inevitably have one or more poor performances, which affects the use experience and safety performance of people. Compared with traditional organic friction materials, ceramic materials have great advantages in life, environment and stability, and thus become an important research direction.

[0004] Chinese patent CN107489717A discloses a heat-resistant composite fiber reinforced brake pad, which is made of the following components by weight: phenolic resin 7-23 parts, reinforced composite fiber 5-15 parts, mineral fiber 3-17 parts, glass fiber 2-8 parts, montmorillonite nano powder 3-8 parts, 2,4,6-tris (dimethylaminomethyl) phenol 0.3-0.9 parts, barium sulfate 5-15 parts, butyronitrile powder 3-12 parts, coke powder 4-11 parts, friction powder 5-15 parts, graphite 5-15 parts, tire powder 5-15 parts, carbon black 3-7 parts, nano fluorite powder 4-10 parts, sepiolite 2-7 parts, nano silica aerogel powder 3-9 parts, heavy calcium carbonate 2-6 parts, silane coupling agent 5-15 parts. The non-metallic brake pad of the application has good heat stability, heat decomposition resistance, heat decay resistance, stable friction coefficient, high wear resistance and low braking noise. However, the silica aerogel in the patent is in the form of powder, which is easy to cause uneven mixing, thereby making the product performance very unstable.

[0005] Therefore, it is of great significance to develop a composite material for brake pads with strong heat stability, excellent friction performance and low noise. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a composite material for brake pads and a preparation method thereof, which has good high temperature resistance and friction performance, and also has excellent wear resistance and low noise, thereby improving the service life of the brake pad.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0008] A composite material for brake pads, by weight, comprises the following raw materials:

[0009] 15-20 parts of modified phenolic resin, 12-16 parts of modified composite fiber, 4-7 parts of aramid fiber, 5-8 parts of rubber powder, 3-5 parts of steel fiber, 6-9 parts of graphite, 4-6 parts of modified sepiolite, 3-5 parts of aluminum oxide, 2-3 parts of silicon carbide, 4-6 parts of vermiculite, 9-13 parts of potassium titanate whisker, 8-11 parts of barium sulfate;

[0010] The modified composite fiber is prepared by mixing basalt fiber and carbon fiber, coating lanthanum gadolinium oxide on the surface through hydrothermal reaction, modifying with silane, and finally reacting with 4,5-diamino-2,6-dimercaptopyrimidine.

[0011] Preferably, the modified phenolic resin is boron cashew oil double modified phenolic resin.

[0012] In the present application, through the synergistic effect of various raw materials, the comprehensive performance balance required by the composite material for brake pads is achieved, the modified phenolic resin is used as the base material to bond other components together, the aramid fiber improves the overall strength and impact toughness of the material to prevent brittle fracture, the steel fiber provides excellent structural strength and stiffness while improving the thermal conductivity of the material, which helps to dissipate friction heat and reduce thermal decay, the potassium titanate whisker can effectively stabilize the friction coefficient and improve the wear resistance of the material, the aluminum oxide and silicon carbide are hard abrasives used to provide basic friction, clean the surface of the mating disc, and maintain effective friction contact, the graphite acts as a solid lubricant to form a lubricating film on the friction interface, stabilize the friction coefficient, reduce wear, and help with heat conduction and noise reduction, and the rubber powder, vermiculite and modified sepiolite are used to absorb vibration and reduce brake noise.

[0013] Preferably, a composite material for brake pads comprises the following raw materials by weight: modified phenolic resin 17-20 parts, modified composite fiber 14-16 parts, aramid fiber 5-7 parts, rubber powder 6-8 parts, steel fiber 3-4 parts, graphite 6-8 parts, modified sepiolite 5-6 parts, aluminum oxide 3-4 parts, silicon carbide 2-3 parts, vermiculite 5-6 parts, potassium titanate whisker 11-13 parts, barium sulfate 8-10 parts.

[0014] Preferably, the preparation method of the modified composite fiber comprises the following steps:

[0015] S1, mix basalt fiber and carbon fiber uniformly, then add acidic potassium permanganate solution for immersion treatment, filter, wash and dry after treatment to obtain mixed fiber;

[0016] S2, add the mixed fiber in step S1 to deionized water, then add lanthanum nitrate and gadolinium nitrate, and then add ammonia water for hydrothermal reaction, filter, wash, dry and calcine after reaction to obtain composite fiber;

[0017] S3, add the composite fiber in step S2 to ethanol aqueous solution, then add vinyltriethoxysilane for stirring reaction, filter, wash and dry after reaction to obtain organic composite fiber;

[0018] S4, add the organic composite fiber in step S3 to DMF, then add 4,5-diamino-2,6-dimercaptopyrimidine and benzophenone for constant temperature reaction under ultraviolet irradiation, filter, wash and dry after reaction to obtain modified composite fiber.

[0019] Preferably, the mass ratio of basalt fiber to carbon fiber in step S1 is 8-9:1-2, the mass concentration of the acidic potassium permanganate solution is 3-5%, and the pH is 2-3; the temperature of the immersion treatment is 30-40℃, and the time is 2-3h.

[0020] In the present application, basing on the mixture of basalt fiber and carbon fiber as the basic framework, combining the good mechanical properties, chemical corrosion resistance, relatively low cost of basalt fiber, and the high modulus, high strength, excellent thermal conductivity and inherent good tribological properties of carbon fiber, through acidic potassium permanganate pretreatment, more binding sites are formed on the fiber surface.

[0021] Preferably, the mass fraction of ammonia water in step S2 is 15-20%, the mass ratio of the mixed fiber, deionized water, lanthanum nitrate, gadolinium nitrate, ammonia water is 40-50:600-700:15-25:5-10:30-40; the temperature of the hydrothermal reaction is 150-170℃, and the time is 6-8h; the temperature of the calcination is 400-500℃, and the time is 2-3h.

[0022] In the present application, the hydrothermal reaction and subsequent calcination generate lanthanum / gadolinium composite oxides in situ on the surface of the mixed fiber, and the two form a solid solution which has more excellent comprehensive thermodynamic stability than a single oxide, which endows the fiber surface with better high-temperature resistance and wear resistance.

[0023] Preferably, the mass ratio of the composite fiber and vinyltriethoxysilane in step S3 is 50-60:6-9, and the temperature of the stirring reaction is 60-70℃, and the time is 2-3h.

[0024] Preferably, the mass ratio of the organic composite fiber, 4,5-diamino-2,6-dimercaptopyrimidine, and benzophenone in step S4 is 60-70:5-7:0.3-0.5; the intensity of the ultraviolet irradiation is 10-20mW / cm², the temperature of the constant-temperature reaction is 70-80℃, and the time is 1-2h.

[0025] In the present application, the composite fiber is treated by silane coupling agent to introduce double bond groups on its surface, and then through thiol-ene click chemistry reaction, 4,5-diamino-2,6-dimercaptopyrimidine molecules are added to the fiber surface through addition reaction of one mercapto group, forming stable thioether bonds, and the pyrimidine heterocyclic structure of 4,5-diamino-2,6-dimercaptopyrimidine molecules itself has good thermal stability, which helps to improve the stability of the interface region at high temperature, and 4,5-diamino-2,6-dimercaptopyrimidine molecules have two active amino groups, which can react with active groups (such as hydroxymethyl) in modified phenolic resin during the process of hot-pressing and curing of the composite material, forming firm covalent bonds, greatly enhancing the interfacial bonding strength between the modified composite fiber and the resin matrix, which is much better than the traditional physical adsorption or weak hydrogen bond action.

[0026] Preferably, the preparation method of the modified sepiolite is as follows:

[0027] 50g of the sepiolite is added into a nitric acid solution with a mass fraction of 5-10%, and then soaked for 1-2h, followed by filtration, washing, and drying, and then added into 800mL of an ethanol aqueous solution (the volume ratio of ethanol to water is 3:1), and then 6-8g of γ-aminopropyltrimethoxysilane is added, and then reacted at 60-65℃ for 2-3h, and then filtered, washed, and dried after the reaction is completed, to obtain the organic sepiolite, and then 50g of the organic sepiolite is added into toluene, and then 1,4-butanediol diglycidyl ether 7-10g is added, and then reacted at 50-60℃ for 1-2h, and then filtered, washed, and dried after the reaction is completed, to obtain the modified sepiolite.

[0028] In the present application, the sepiolite is first subjected to acid treatment to remove impurities, increase the specific surface area, and activate the surface hydroxyl groups, and then modified by using a silane coupling agent to obtain sepiolite with amino groups on the surface, and finally the surface-grafted amino groups react with the epoxy groups in the 1,4-butanediol diglycidyl ether, so that a modified sepiolite with a flexible chain segment (butanediol segment) and a reactive epoxy group at the end is introduced on the surface of the sepiolite, which not only enhances the chemical bonding force with the phenolic resin matrix and improves the interfacial compatibility, but also plays a certain toughening effect and helps to dissipate vibration energy, thereby reducing the noise and vibration generated during the friction process of the composite material.

[0029] The present application also protects a preparation method of the composite material for brake pads as described above, which comprises the following steps:

[0030] The raw materials are weighed according to the formula, mixed uniformly in a high-speed mixer to obtain a blended material, and then the blended material is added into a mold for pressing, and then heat treated, to obtain the composite material for brake pads.

[0031] Preferably, the pressing condition is 160-180℃, 30-40MPa, and the pressing time is 6-8min, and the heat treatment is 170-190℃, and the heat preservation time is 4-6h.

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] (1) The composite material for brake pads provided by the present application takes modified phenolic resin as the base resin, introduces composite fibers modified by multiple steps of surface chemical modification as the core reinforcing phase, and scientifically matches other traditional but effective reinforcing fibers, friction regulators and fillers, so that the mechanical properties, wear resistance, thermal stability and friction stability of the composite material are significantly improved under the synergistic effect of multiple components; the modified composite fiber takes basalt / carbon fiber as the base material, and the surface is coated with lanthanum / gadolinium rare earth oxide coating and 4,5-diamino-2,6-dimercaptopyrimidine organic layer grafted by silane and thiol-alkene click chemistry in sequence, so that the mechanical strength, wear resistance and high-temperature stability of the material can be improved at the same time, and the interfacial bonding force between the modified composite fiber and the resin matrix is significantly improved by the introduction of rare earth oxides and amino groups; meanwhile, the formula also contains diversified auxiliary reinforcing fibers such as aramid fiber, steel fiber and potassium titanate whisker, which can further improve the toughness, thermal conductivity and friction stability of the composite material; and the addition of rubber powder, vermiculite and modified sepiolite can be used to absorb vibration, reduce brake noise and improve the comprehensive performance of the brake pad.

[0034] (2) The composite material for brake pads provided by the present application introduces modified composite fibers, which take a mixture of basalt fiber and carbon fiber as the basic framework, are immersed in acidic potassium permanganate for treatment, so that there are more binding sites on the surface of the fiber, then through hydrothermal reaction and subsequent calcination, a uniform lanthanum / gadolinium composite oxide is generated in situ on the surface of the mixed fiber, which can play multiple roles in the friction process, helping to promote the formation of stable friction film and transfer film at low temperature, reducing the surface roughness, and changing the wear mechanism from the destructive adhesive wear to the relatively mild abrasive wear, thereby improving the wear resistance, and at high temperature friction stage, the lanthanum / gadolinium composite oxide can effectively inhibit the thermal degradation of the phenolic resin matrix, improve the overall heat resistance and anti-thermal decay ability of the composite material, and the lanthanum oxide can also react with the aluminum oxide in the formula at high temperature to generate LaAlO3 phase with better thermal stability, further improving the high-temperature friction and wear properties of the composite material under severe braking conditions; then 4,5-diamino-2,6-dimercaptopyrimidine is grafted onto the composite fiber through chemical reaction, the amino groups on the 4,5-diamino-2,6-dimercaptopyrimidine can react with the modified phenolic resin during the curing process to form a firm interfacial chemical bond, greatly enhancing the interfacial bonding strength between the modified composite fiber and the resin matrix, which is beneficial to the effective transmission of stress between the matrix and the reinforcing phase, improving the overall mechanical properties of the composite material, and the grafted pyrimidine heterocyclic aromatic structure itself has good thermal stability, which helps to improve the stability of the interfacial region at high temperature, improving the wear resistance of the composite material at high temperature.

[0035] (3) The composite material for brake pads provided by the application adds modified sepiolite, which is subjected to double surface treatment of silane coupling agent and 1,4-butanediol diglycidyl ether, so as to improve the compatibility of sepiolite with a phenolic resin matrix and promote the uniform dispersion of sepiolite in the matrix, and the flexible butanediol segment in 1,4-butanediol diglycidyl ether helps sepiolite to effectively exert its structural characteristics to absorb vibration energy generated in the braking process, thereby significantly reducing brake noise. DETAILED DESCRIPTION

[0036] The technical solutions of the application will be clearly and completely described below in combination with the embodiments. Obviously, the described embodiments are only some of the embodiments of the application, but not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0037] Unless otherwise specified, the chemical reagents and materials in the application are purchased through market channels or synthesized from raw materials purchased through market channels.

[0038] The boron cashew oil double-modified phenolic resin is purchased from Jining Tangyi Chemical Co., Ltd., and the model is FBY double-modified high-temperature high-carbon resin; the basalt fiber has a length of 6-8 mm and a diameter of 10-15 μm; the carbon fiber has a length of 3-6 mm and a diameter of 7-12 μm; the aramid fiber has a length of 6-8 mm and a diameter of 10-15 μm; the rubber powder is nitrile rubber powder with a particle size of 100 meshes; the steel fiber has a length of 10 mm and a diameter of 8 μm; the graphite is expandable graphite with a particle size of 325 meshes; the sepiolite has a particle size of 325 meshes; the aluminum oxide has a particle size of 325 meshes, the silicon carbide has a particle size of 400 meshes, the vermiculite has a particle size of 300 meshes, the potassium titanate whisker has a length of 30-40 μm and a diameter of 0.3-0.5 μm; and the barium sulfate has a particle size of 325 meshes.

[0039] Example 1

[0040] A composite material for brake pads comprises the following raw materials in parts by weight:

[0041] Modified phenolic resin 18 parts, modified composite fiber 14 parts, aramid fiber 6 parts, rubber powder 7 parts, steel fiber 4 parts, graphite 8 parts, modified sepiolite 5 parts, aluminum oxide 4 parts, silicon carbide 2.5 parts, vermiculite 5 parts, potassium titanate whisker 11 parts, and barium sulfate 10 parts.

[0042] The preparation method of the modified composite fiber comprises the following steps:

[0043] S1, 85g basalt fiber and 15g carbon fiber are uniformly mixed, then added into acidic potassium permanganate solution (mass concentration of potassium permanganate is 4%) with pH of 2.5, and immersed at 35℃ for 2.5h, after treatment, filtered, washed and dried to obtain mixed fiber;

[0044] S2, 45g mixed fiber in step S1 is added into 650g deionized water, then 20g lanthanum nitrate and 8g gadolinium nitrate are added, followed by adding 35g ammonia water with mass concentration of 20%, and hydrothermal reaction is carried out at 160℃ for 7h, after reaction, filtered, washed and dried, and calcined at 450℃ for 2.5h to obtain composite fiber;

[0045] S3, 55g composite fiber in step S2 is added into 800mL ethanol aqueous solution (volume ratio of ethanol to water is 3:1), then 8g vinyltriethoxysilane is added, and stirred at 65℃ for 2.5h, after reaction, filtered, washed and dried to obtain organic composite fiber;

[0046] S4, 65g organic composite fiber in step S3 is added into 900mL DMF, then 6g 4,5-diamino-2,6-dimercaptopyrimidine and 0.4g benzophenone are added, and constant temperature reaction is carried out under ultraviolet irradiation, the intensity of ultraviolet irradiation is 15mW / cm², the temperature of constant temperature reaction is 75℃, and the time is 1.5h, after reaction, filtered, washed and dried to obtain modified composite fiber.

[0047] The preparation method of the modified sepiolite is as follows:

[0048] 50g sepiolite is added into 8% nitric acid solution, and immersed for 1.5h, then filtered, washed and dried, added into 800mL ethanol aqueous solution (volume ratio of ethanol to water is 3:1), then 7g γ-aminopropyltrimethoxysilane is added, and reacted at 63℃ for 2.5h, after reaction, filtered, washed and dried to obtain organic sepiolite, then 50g organic sepiolite is added into 800mL toluene, then 9g 1,4-butanediol diglycidyl ether is added, and reacted at 55℃ for 1.5h, after reaction, filtered, washed and dried to obtain modified sepiolite.

[0049] A preparation method of a composite material for brake pad, comprising the following steps:

[0050] The raw materials are weighed according to the formula, and the raw materials are added into a high-speed mixer and uniformly mixed to obtain a blended material, then the blended material is added into a mold for pressing, and the pressing conditions are 170℃ and 35MPa for 7min, and then heat treatment is carried out, and the heat treatment process is 180℃ for 5h, to obtain the composite material for brake pad.

[0051] Example 2

[0052] A composite material for brake pad, comprising the following raw materials in parts by weight:

[0053] Modified phenolic resin 15 parts, modified composite fiber 12 parts, aramid fiber 4 parts, rubber powder 5 parts, steel fiber 3 parts, graphite 6 parts, modified sepiolite 4 parts, aluminum oxide 3 parts, silicon carbide 2 parts, vermiculite 4 parts, potassium titanate whisker 9 parts, barium sulfate 8 parts.

[0054] The preparation method of the modified composite fiber comprises the following steps:

[0055] S1, 80g basalt fiber and 20g carbon fiber are uniformly mixed, then added into acidic potassium permanganate solution (mass concentration of potassium permanganate is 3%) with pH of 3, immersed and treated at 30℃ for 3h, after treatment, filtered, washed and dried to obtain mixed fiber;

[0056] S2, 40g mixed fiber in step S1 is added into 600g deionized water, then 15g lanthanum nitrate and 5g gadolinium nitrate are added, followed by adding 30g ammonia water with mass concentration of 20%, hydrothermal reaction is carried out at 150℃ for 8h, after reaction, filtered, washed and dried, calcined at 400℃ for 3h to obtain composite fiber;

[0057] S3, 50g composite fiber in step S2 is added into 800mL ethanol aqueous solution (volume ratio of ethanol to water is 3:1), then 6g vinyltriethoxysilane is added, stirred and reacted at 60℃ for 3h, after reaction, filtered, washed and dried to obtain organic composite fiber;

[0058] S4, 60g organic composite fiber in step S3 is added into 900mL DMF, then 5g 4,5-diamino-2,6-dimercaptopyrimidine and 0.3g benzophenone are added, constant temperature reaction is carried out under ultraviolet irradiation, the intensity of ultraviolet irradiation is 10mW / cm², the temperature of constant temperature reaction is 70℃, the time is 2h, after reaction, filtered, washed and dried to obtain modified composite fiber.

[0059] The preparation method of the modified sepiolite is as follows:

[0060] 50g of the sepiolite was added into a 5% by mass nitric acid solution, immersed for 1h, then filtered, washed, dried, added into 800mL of an ethanol aqueous solution (volume ratio of ethanol to water is 3:1), then 6g of γ-aminopropyltrimethoxysilane was added, reacted at 60℃ for 3h, after the reaction was completed, filtered, washed, dried to obtain the organic sepiolite, then 50g of the organic sepiolite was added into 800mL of toluene, then 7g of 1,4-butanediol diglycidyl ether was added, reacted at 50℃ for 2h, after the reaction was completed, filtered, washed, dried to obtain the modified sepiolite.

[0061] A preparation method of a composite material for brake pads, comprising the following steps:

[0062] The raw materials are weighed according to the formula, mixed uniformly in a high-speed mixer to obtain a blended material, then the blended material is added into a mold for pressing, the pressing conditions are 160℃, 30MPa, and 8min, and then heat treatment is performed, the heat treatment process is 170℃ for 6h, thereby obtaining the composite material for brake pads.

[0063] Example 3

[0064] A composite material for brake pads, comprising the following raw materials in parts by weight:

[0065] 20 parts of modified phenolic resin, 6 parts of modified composite fiber, 7 parts of aramid fiber, 8 parts of rubber powder, 5 parts of steel fiber, 9 parts of graphite, 6 parts of modified sepiolite, 5 parts of aluminum oxide, 3 parts of silicon carbide, 6 parts of vermiculite, 13 parts of potassium titanate whisker, and 11 parts of barium sulfate.

[0066] A preparation method of the modified composite fiber, comprising the following steps:

[0067] S1, 90g of basalt fiber and 10g of carbon fiber were uniformly mixed, then added into an acidic potassium permanganate solution (mass concentration of potassium permanganate is 5%) with pH of 2, immersed and treated at 40℃ for 2h, after the treatment was completed, filtered, washed, and dried to obtain mixed fibers;

[0068] S2, 50g of the mixed fibers in step S1 were added into 700g of deionized water, then 25g of lanthanum nitrate and 10g of gadolinium nitrate were added, then 40g of ammonia water with mass concentration of 20% was added, hydrothermal reaction was carried out at 170℃ for 6h, after the reaction was completed, filtered, washed, and dried, calcined at 500℃ for 2h to obtain composite fibers;

[0069] S3, 60g of the composite fibers in step S2 were added into 800mL of an ethanol aqueous solution (volume ratio of ethanol to water is 3:1), then 9g of vinyltriethoxysilane was added, stirred and reacted at 70℃ for 2h, after the reaction was completed, filtered, washed, and dried to obtain organic composite fibers;

[0070] S4, 70 g of the organic composite fiber in step S3 is added into 900 mL of DMF, then 7 g of 4, 5-diamino-2, 6-dimercaptopyrimidine and 0.5 g of benzophenone are added, and a constant temperature reaction is carried out under ultraviolet irradiation, the intensity of the ultraviolet irradiation is 20 mW / cm2, the temperature of the constant temperature reaction is 80℃, the time is 1 h, after the reaction is completed, filtration, washing and drying are carried out, and the modified composite fiber is obtained.

[0071] The preparation method of the modified sepiolite is as follows:

[0072] 50 g of sepiolite is added into a 10% nitric acid solution, immersed for 2 h, then filtered, washed and dried, added into 800 mL of an ethanol aqueous solution (the volume ratio of ethanol to water is 3:1), then 8 g of γ-aminopropyltrimethoxysilane is added, and a reaction is carried out at 65℃ for 2 h, after the reaction is completed, filtration, washing and drying are carried out, and the organic sepiolite is obtained, then 50 g of the organic sepiolite is added into 800 mL of toluene, then 10 g of 1, 4-butanediol diglycidyl ether is added, and a reaction is carried out at 60℃ for 1 h, after the reaction is completed, filtration, washing and drying are carried out, and the modified sepiolite is obtained.

[0073] A preparation method of a composite material for brake pads, comprising the following steps:

[0074] The raw materials are weighed according to the formula, mixed uniformly in a high-speed mixer to obtain a blended material, then the blended material is added into a mold for pressing, the pressing condition is 180℃, 40 MPa, and the pressing time is 6 min, and then heat treatment is carried out, the heat treatment process is 190℃ for 4 h, and the composite material for brake pads is obtained.

[0075] Comparative Example 1

[0076] A composite material for brake pads, comprising the following raw materials in parts by weight:

[0077] Modified phenolic resin 18 parts, modified composite fiber 14 parts, aramid fiber 6 parts, rubber powder 7 parts, steel fiber 4 parts, graphite 8 parts, modified sepiolite 5 parts, aluminum oxide 4 parts, silicon carbide 2.5 parts, vermiculite 5 parts, potassium titanate whisker 11 parts, and barium sulfate 10 parts.

[0078] The preparation method of the modified composite fiber comprises the following steps:

[0079] S1, 85 g of basalt fiber is uniformly mixed with 15 g of carbon fiber, then added into an acidic potassium permanganate solution with a pH of 2.5 (the mass concentration of potassium permanganate is 4%), immersed and treated at 35℃ for 2.5 h, after the treatment is completed, filtration, washing and drying are carried out, and the mixed fiber is obtained;

[0080] S2, 45 g of the mixed fiber in step S1 was added to 650 g of deionized water, followed by the addition of 20 g of lanthanum nitrate, 8 g of gadolinium nitrate, and then 35 g of 20% ammonia water, and then hydrothermal reaction was carried out at 160°C for 7 h. After the reaction was completed, filtration, washing, and drying were performed, and then calcination was carried out at 450°C for 2.5 h to obtain a composite fiber;

[0081] S3, 55 g of the composite fiber in step S2 was added to 800 mL of an ethanol aqueous solution (volume ratio of ethanol to water was 3:1), followed by the addition of 8 g of vinyltriethoxysilane, and then stirring reaction was carried out at 65°C for 2.5 h. After the reaction was completed, filtration, washing, and drying were performed to obtain a modified composite fiber.

[0082] The preparation method of the modified sepiolite is as follows:

[0083] 50 g of sepiolite was added to an 8% nitric acid solution, and then immersed for 1.5 h. Subsequently, filtration, washing, and drying were performed, and then 800 mL of an ethanol aqueous solution (volume ratio of ethanol to water was 3:1) was added, followed by the addition of 7 g of γ-aminopropyltrimethoxysilane, and then reaction was carried out at 63°C for 2.5 h. After the reaction was completed, filtration, washing, and drying were performed to obtain an organic sepiolite. Subsequently, 50 g of the organic sepiolite was added to 800 mL of toluene, followed by the addition of 9 g of 1,4-butanediol diglycidyl ether, and then reaction was carried out at 55°C for 1.5 h. After the reaction was completed, filtration, washing, and drying were performed to obtain a modified sepiolite.

[0084] A preparation method of a composite material for brake pads, comprising the following steps:

[0085] The raw materials were weighed according to the formula, and then mixed uniformly in a high-speed mixer to obtain a blended material. Subsequently, the blended material was added to a mold for pressing, and the pressing conditions were 170°C, 35 MPa, and 7 min. Then, heat treatment was performed at 180°C for 5 h to obtain the composite material for brake pads.

[0086] Compared with Example 1, the comparative example does not introduce 4,5-diamino-2,6-dimercaptopyrimidine on the modified composite fiber.

[0087] Comparative Example 2

[0088] A composite material for brake pads, comprising the following raw materials in parts by weight:

[0089] Modified phenolic resin 18 parts, modified composite fiber 14 parts, aramid fiber 6 parts, rubber powder 7 parts, steel fiber 4 parts, graphite 8 parts, modified sepiolite 5 parts, aluminum oxide 4 parts, silicon carbide 2.5 parts, vermiculite 5 parts, potassium titanate whisker 11 parts, and barium sulfate 10 parts.

[0090] The preparation method of the modified composite fiber comprises the following steps:

[0091] S1, 85g basalt fibers were mixed with 15g carbon fibers, and then added into an acidic potassium permanganate solution (mass concentration of potassium permanganate was 4%) with pH of 2.5, and immersed at 35℃ for 2.5h, and then filtered, washed and dried to obtain mixed fibers;

[0092] S2, 55g mixed fibers in step S1 were added into 800mL ethanol aqueous solution (volume ratio of ethanol to water was 3:1), and then 8g vinyltriethoxysilane was added, and stirred at 65℃ for 2.5h, and then filtered, washed and dried to obtain organic composite fibers;

[0093] S3, 65g organic composite fibers in step S3 were added into 900mL DMF, and then 6g 4,5-diamino-2,6-dimercaptopyrimidine and 0.4g benzophenone were added, and then reacted under ultraviolet irradiation, the intensity of ultraviolet irradiation was 15mW / cm², the temperature of constant temperature reaction was 75℃, and the time was 1.5h, and then filtered, washed and dried to obtain modified composite fibers.

[0094] The preparation method of the modified sepiolite is as follows:

[0095] 50g sepiolite was added into 8% nitric acid solution, and immersed for 1.5h, and then filtered, washed and dried, and then added into 800mL ethanol aqueous solution (volume ratio of ethanol to water was 3:1), and then 7g γ-aminopropyltrimethoxysilane was added, and reacted at 63℃ for 2.5h, and then filtered, washed and dried to obtain organic sepiolite, and then 50g organic sepiolite was added into 800mL toluene, and then 9g 1,4-butanediol diglycidyl ether was added, and reacted at 55℃ for 1.5h, and then filtered, washed and dried to obtain modified sepiolite.

[0096] A preparation method of a composite material for brake pad, comprising the following steps:

[0097] The raw materials were weighed according to the formula, and then mixed in a high-speed mixer to obtain a blended material, and then the blended material was added into a mold for pressing, and the pressing conditions were 170℃, 35MPa for 7min, and then heat treated at 180℃ for 5h to obtain the composite material for brake pad.

[0098] Compared with Example 1, lanthanum gadolinium oxide was not introduced on the modified composite fibers in the present comparative example.

[0099] Comparative Example 3

[0100] A composite material for brake pad, comprising the following raw materials in parts by weight:

[0101] Modified phenolic resin 18 parts, modified composite fiber 14 parts, aramid fiber 6 parts, rubber powder 7 parts, steel fiber 4 parts, graphite 8 parts, sepiolite 5 parts, aluminum oxide 4 parts, silicon carbide 2.5 parts, vermiculite 5 parts, potassium titanate whisker 11 parts, barium sulfate 10 parts.

[0102] The preparation method of the modified composite fiber comprises the following steps:

[0103] S1, 85g basalt fiber and 15g carbon fiber are uniformly mixed, then added into acidic potassium permanganate solution with pH of 2.5 (mass concentration of potassium permanganate is 4%), and immersed at 35℃ for 2.5h, and after treatment, filtered, washed and dried to obtain mixed fiber;

[0104] S2, 45g mixed fiber in step S1 is added into 650g deionized water, then 20g lanthanum nitrate and 8g gadolinium nitrate are added, followed by adding 35g ammonia water with mass concentration of 20%, and hydrothermal reaction is carried out at 160℃ for 7h, and after reaction, filtered, washed and dried, and calcined at 450℃ for 2.5h to obtain composite fiber;

[0105] S3, 55g composite fiber in step S2 is added into 800mL ethanol aqueous solution (volume ratio of ethanol to water is 3:1), then 8g vinyltriethoxysilane is added, and stirred at 65℃ for 2.5h, and after reaction, filtered, washed and dried to obtain organic composite fiber;

[0106] S4, 65g organic composite fiber in step S3 is added into 900mL DMF, then 6g 4,5-diamino-2,6-dimercaptopyrimidine and 0.4g benzophenone are added, and constant temperature reaction is carried out under ultraviolet irradiation, the intensity of ultraviolet irradiation is 15mW / cm², the temperature of constant temperature reaction is 75℃, and the time is 1.5h, and after reaction, filtered, washed and dried to obtain modified composite fiber.

[0107] A preparation method of a composite material for brake pad, comprising the following steps:

[0108] The raw materials are weighed according to the formula, mixed uniformly in a high-speed mixer to obtain a blended material, then the blended material is added into a mold for pressing, and the pressing conditions are 170℃ and 35MPa for 7min, and then heat treatment is carried out, and the heat treatment process is 180℃ for 5h, to obtain the composite material for brake pad.

[0109] Compared with example 1, the sepiolite is not modified in the present comparative example.

[0110] The brake pad composite materials prepared from examples 1-3 and comparative examples 1-3 were tested for performance, wherein the impact strength was tested according to standard GB / T 33835-2017 "Friction material impact strength test method", the bending strength was tested according to standard GB / T 9341-2008, and the friction coefficient and wear amount were tested according to standard GB 5763-2018 "Automobile brake pad", and the test results are shown in Table 1 below.

[0111] Table 1 Performance test results of brake pad composite materials of each group

[0112]

[0113] As can be seen from Table 1, the brake pad composite material prepared by the application has good mechanical properties, stable friction coefficient, good heat resistance and sound absorption performance, and has good application prospect.

[0114] Although embodiments of the application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for producing a composite material for brake pads, characterized by, The method comprises the following steps: The raw materials are weighed according to the formula, and then the raw materials are mixed uniformly in a high-speed mixer to obtain a blended material, and then the blended material is pressed in a mold and then heat treated to obtain the composite material for brake pads. The composite material for brake pads comprises the following raw materials in parts by weight: Modified phenolic resin 15-20 parts, modified composite fiber 12-16 parts, aramid fiber 4-7 parts, rubber powder 5-8 parts, steel fiber 3-5 parts, graphite 6-9 parts, modified sepiolite 4-6 parts, aluminum oxide 3-5 parts, silicon carbide 2-3 parts, vermiculite 4-6 parts, potassium titanate whisker 9-13 parts, barium sulfate 8-11 parts; The preparation method of the modified composite fiber comprises the following steps: S1, mix basalt fiber and carbon fiber uniformly, then immerse in acidic potassium permanganate solution for dipping treatment to obtain mixed fiber; S2, add the mixed fiber into deionized water, then add lanthanum nitrate and gadolinium nitrate, and then add ammonia water to perform hydrothermal reaction, and then calcine to obtain composite fiber; S3, add the composite fiber into ethanol aqueous solution, then add vinyltriethoxysilane to perform stirring reaction to obtain organic composite fiber; S4, add the organic composite fiber into DMF, then add 4,5-diamino-2,6-dimercaptopyrimidine and benzophenone to perform constant temperature reaction under ultraviolet irradiation to obtain modified composite fiber; The mass ratio of the basalt fiber to the carbon fiber in step S1 is 8-9:1-2, the mass concentration of the acidic potassium permanganate solution is 3-5%, and the pH is 2-3; the dipping treatment is performed at a temperature of 30-40℃ for 2-3h.

2. The production method according to claim 1, characterized by, The composite material for brake pads comprises the following raw materials in parts by weight: modified phenolic resin 17-20 parts, modified composite fiber 14-16 parts, aramid fiber 5-7 parts, rubber powder 6-8 parts, steel fiber 3-4 parts, graphite 6-8 parts, modified sepiolite 5-6 parts, aluminum oxide 3-4 parts, silicon carbide 2-3 parts, vermiculite 5-6 parts, potassium titanate whisker 11-13 parts, and barium sulfate 8-10 parts.

3. The preparation method according to claim 1, characterized in that, The mass fraction of the ammonia water in step S2 is 15-20%, and the mass ratio of the mixed fiber, deionized water, lanthanum nitrate, gadolinium nitrate, and ammonia water is 40-50:600-700:15-25:5-10:30-40; the hydrothermal reaction is performed at a temperature of 150-170℃ for 6-8h; and the calcination is performed at a temperature of 400-500℃ for 2-3h.

4. The method of claim 1, wherein, The mass ratio of the composite fiber to vinyltriethoxysilane in step S3 is 50-60:6-9, and the stirring reaction is performed at a temperature of 60-70℃ for 2-3h.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the organic composite fiber, 4,5-diamino-2,6-dimercaptopyrimidine, and benzophenone in step S4 is 60-70:5-7:0.3-0.5; the ultraviolet irradiation has an intensity of 10-20mW / cm², and the constant temperature reaction is performed at a temperature of 70-80℃ for 1-2h.

6. The method of claim 1, wherein, The preparation method of the modified sepiolite is as follows: After 50 g of sepiolite is acid treated and added to an ethanol aqueous solution, 6-8 g of γ-aminopropyltrimethoxysilane is added and reacted at 60-65°C for 2-3 h, and after the reaction is completed, organic sepiolite is obtained, and then 50 g of the organic sepiolite is added to toluene, 7-10 g of 1,4-butanediol diglycidyl ether is added, and reacted at 50-60°C for 1-2 h, and after the reaction is completed, modified sepiolite is obtained.

7. The preparation method according to claim 1, characterized in that, The pressing conditions are 6-8 min at 160-180°C and 30-40 MPa, and the heat treatment is 4-6 h at 170-190°C.

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