A friction material composition, a friction plate and a method for manufacturing and use thereof

Abstract

The application relates to the technical field of mechanical braking, in particular to a friction material composition, a friction plate and a preparation method and application thereof. The raw material of the friction material composition comprises a friction performance improver, a base material and a binder; the friction performance improver comprises high-hardness ceramic fibers, graphene modified resin, a friction regulator and fillers; the base material comprises an aramid fiber and epoxy resin composite layer, potassium hexatitanate, a coupling agent and a bonding aid; and the binder comprises nitrile rubber, modified phenolic resin, potassium hexatitanate, a coupling agent, talcum powder and a curing accelerator. The friction plate provided by the application has strong friction coefficient stability under high-temperature working conditions, reduces braking noise and vibration, prolongs the service life of the friction plate and the brake disc, adopts environment-friendly materials, and meets the requirements of copper-free and asbestos-free.

Description

Technical Field

[0001] This invention relates to the field of mechanical braking technology, and in particular to a friction material composition, friction pad, preparation method and application thereof. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Currently, friction materials for various mechanical braking systems are typically composed of reinforcing fibers (such as steel fibers and glass fibers), binders (phenolic resins, etc.), and friction-adjusting fillers (graphite, ceramic particles, etc.). In existing technologies, friction pads primarily improve braking performance through optimized material ratios or surface groove designs. These include semi-metallic friction pads, ceramic composite friction pads, and organic friction pads. However, existing friction pad technologies suffer from the following problems: During continuous braking (>350 ℃), the friction coefficient drops sharply due to resin carbonization or filler failure; uneven material hardness or poor interfacial adhesion leads to abnormal braking noise; traditional groove designs easily cause localized stress concentration, accelerating wear; and they contain harmful substances such as copper and asbestos. Summary of the Invention

[0004] In view of this, the present invention provides a friction material composition, a friction pad, a method for preparing the same, and its applications. The friction material composition and friction pad provided by the present invention can improve the stability of the friction coefficient under high-temperature operating conditions, reduce braking noise and vibration, and extend the service life of the friction pad and brake disc; moreover, they use environmentally friendly materials, meeting the requirements of being copper-free and asbestos-free.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a friction material composition, wherein the raw materials of the friction material composition include: a friction performance improver, a base material, and a binder; The friction performance improver includes high-hardness ceramic fibers, graphene-modified resin, friction modifier, and filler; The base material includes an aramid fiber-epoxy resin composite layer, potassium hexatitanate, coupling agent, and adhesive additive. The adhesive includes nitrile rubber, modified phenolic resin, potassium hexatitanate, coupling agent, talc, and curing accelerator.

[0006] Furthermore, in the friction material composition, the friction performance improver accounts for 40%-50% of the total mass, the base material accounts for 30%-40% of the total mass, and the binder accounts for 10%-20% of the total mass.

[0007] Furthermore, the high-hardness ceramic fiber is silicon carbide ceramic fiber.

[0008] Furthermore, the graphene-modified resin is a graphene-modified cashew nutshell oil-modified phenolic resin.

[0009] Furthermore, the friction modifier is a mixture of graphite and antimony sulfide; the mass ratio of graphite to antimony sulfide is 1:0.8-1.2.

[0010] Furthermore, the filler is a mixture of talc and calcium carbonate; the mass ratio is 1-3:1; preferably 2:1.

[0011] Furthermore, the mass ratio of silicon carbide ceramic fiber to graphene-modified resin is 1:1.2~1.5.

[0012] Furthermore, in the friction performance improver, silicon carbide ceramic fiber accounts for 35%-40% of the total mass, graphene modified resin accounts for 48%-52% of the total mass, friction modifier accounts for 10%-13%, and the remainder is filler.

[0013] Furthermore, the mass ratio of the aramid fiber-epoxy resin composite layer to potassium hexatitanate is 1.5~2:1.

[0014] Furthermore, the preparation method of the aramid fiber-epoxy resin composite layer is as follows: After plasma surface treatment, aramid fibers are immersed in a mixture of E-51 epoxy resin and curing agent for impregnation, and then pre-cured to form an aramid fiber-epoxy resin composite layer.

[0015] Furthermore, the adhesive is cashew nut shell oil modified phenolic resin.

[0016] Furthermore, the immersion time is 10-30 minutes; the immersion temperature is 20-30 ℃.

[0017] Furthermore, the pre-curing temperature is 75-85 ℃; the time is 10-20 min.

[0018] Furthermore, the mass ratio of aramid fiber to epoxy resin is 1:0.8~1.

[0019] Furthermore, the curing agent is an amine-based curing agent, preferably diethylenetriamine.

[0020] Furthermore, in the base material, the aramid fiber-epoxy resin composite layer accounts for 55%-60% of the total mass; potassium hexatitanate accounts for 30%-35% of the total mass; and the remainder consists of coupling agent and talc filler.

[0021] Furthermore, the mass ratio of nitrile rubber, modified phenolic resin, and potassium hexatitanate is 1:1.2~1.5:0.5~0.7.

[0022] Furthermore, the curing accelerator is an imidazole curing accelerator, specifically 2-ethyl-4-methylimidazolium; the coupling agent is a silane coupling agent KH550.

[0023] Furthermore, the modified phenolic resin is a cashew nut shell oil-modified phenolic resin, and the preparation method of the modified phenolic resin is as follows: Phenol and formaldehyde are heated, hydrochloric acid is added to react, then cashew nut shell oil is added, and the reaction is continued by heating. After the reaction is completed, the pH is adjusted to 7-8, the mixture is distilled under reduced pressure, and then cooled to obtain the final product.

[0024] Furthermore, the molar ratio of phenol, formaldehyde, and cashew nut shell oil is 1:1.0-1.4:0.2-0.5.

[0025] Further, after reaching 75-85 °C, add hydrochloric acid and react for 60-100 min.

[0026] Further, after adding cashew nut shell oil, the temperature is raised to 90-95 ℃, and the reaction is carried out for 40-80 min.

[0027] Furthermore, the preparation method of the graphene-modified resin is as follows: Graphene powder was added to anhydrous ethanol, stirred, then a coupling agent was added, and the mixture was allowed to stand to obtain a graphene dispersion. The cashew nut shell oil-modified phenolic resin is heated to 50-60 ℃, graphene dispersion is added, and the mixture is stirred at a constant temperature. After stirring, vacuum degassing is performed to obtain the final product.

[0028] Furthermore, the graphene powder has a particle size of ≤ 5 μm.

[0029] Furthermore, the coupling agent is a silane-based coupling agent, preferably KH550.

[0030] Furthermore, the stirring time is 20-40 min; the rotation speed is 1400-1600 r / min.

[0031] Furthermore, the settling time is 8-15 minutes.

[0032] Furthermore, the constant temperature stirring time is 40-80 min; the rotation speed is controlled at 1000-1400 r / min.

[0033] Furthermore, the vacuum degassing time is 20-40 min.

[0034] Secondly, the present invention provides a friction plate, which includes four parts: a back plate, a bottom layer, an intermediate layer and a surface layer. The bottom layer, intermediate layer, and top layer are prepared from the adhesive, base material, and friction modifier described in the first aspect.

[0035] Furthermore, the surface of the friction pad is provided with asymmetrical spiral grooves.

[0036] Furthermore, the asymmetric spiral groove is a conch shell spiral texture, with a width of 0.5-1.2mm, a depth of 0.3-0.8mm, and a groove coverage area of ​​15%-25%.

[0037] Furthermore, the back plate is made of low-carbon steel plate, which is selected from Q235 and SPCC.

[0038] Thirdly, the present invention provides a method for preparing the friction pad described in the second aspect, comprising the following steps: (1) Add the coupling agent to the solvent and stir, let stand, and obtain the coupling agent solution; add talc powder to the solvent and stir to make a filler slurry; The modified phenolic resin is heated to 50-60 ℃, nitrile rubber is added, and the mixture is stirred at a constant temperature to obtain a resin-rubber blend system; coupling agent solution, curing accelerator, filler slurry, and potassium hexatitanate are added in sequence, stirred, allowed to stand, defoamed, coated on the backing plate, and dried. (2) Mix high-hardness ceramic fibers, friction modifiers and fillers, and stir; add graphene-modified resin and continue stirring until particles with a particle size of 2-5 mm are formed to obtain a surface friction performance improver. (3) Mix the aramid fiber-epoxy resin composite layer with potassium hexatitanate and coupling agent, and stir; add the bonding agent and continue stirring to form the intermediate layer base material mixture; (4) Perform the following steps in sequence: extrusion, pressing, heat treatment, grinding, and biomimetic groove forming to obtain the final product.

[0039] Furthermore, the back panel also includes a pre-processing operation, which includes: selection and cutting of back panel raw materials, precision stamping, and surface treatment.

[0040] Furthermore, the specific operation of selecting and cutting the backing material is as follows: select a backing material with a thickness of 1.5-3 mm according to the friction plate specifications; cut the roll material into a rectangular blank that fits the mold using a shearing machine, with the tolerance controlled within ±0.2 mm.

[0041] Furthermore, the specific operation of the precision stamping forming is as follows: stamping is performed using a progressive die or a compound die to complete the blanking, punching, and bending processes in one go. After forming, the flatness tolerance of the back plate is ≤ 0.1 mm, and the hole diameter tolerance is ± 0.05 mm. After stamping, the burrs are removed, and the edges are treated with a grinding wheel or a chamfering machine.

[0042] Furthermore, the specific operation of the surface treatment is as follows: immerse the back panel in an alkaline degreasing agent at 50-60 ℃ for 10-15 minutes to remove surface oil stains; then rinse with clean water and dry.

[0043] Sandblasting roughening: Quartz sand or alumina sand is used to sandblast the steel backing surface at a pressure of 0.4-0.6 MPa to achieve a surface roughness of Ra 3.2-6.3 μm.

[0044] Furthermore, the alkaline degreasing agent is a mixture of sodium hydroxide and sodium carbonate, wherein the mass ratio of sodium hydroxide to sodium carbonate in the mixture is 1:1 to 1.2.

[0045] Furthermore, in step (1), the coupling agent is a silane coupling agent KH550.

[0046] Furthermore, in step (1), the solvent is anhydrous ethanol.

[0047] Further, in step (1), the curing accelerator is an imidazole curing accelerator, specifically 2-ethyl-4-methylimidazole.

[0048] Further, in step (1), the coupling agent is added to the solvent and stirred for 20-40 min; the stirring speed is 1400-1600 r / min; and it is allowed to stand for 8-15 min.

[0049] Furthermore, in step (1), the mixture is stirred at a constant temperature for 50-70 minutes.

[0050] Further, in step (1), after adding coupling agent solution, curing accelerator, filler slurry and potassium hexatitanate, stir for 40-80 min; let stand for 20-25 h.

[0051] Furthermore, in step (2), the stirring time is 20-30 min.

[0052] Furthermore, in step (2), if the material is loose after adding graphene-modified resin, 5%-8% ethanol can be added as a wetting agent.

[0053] Furthermore, in step (3), the stirring time is 10-20 min; the rotation speed is 1000-1200 r / min.

[0054] Furthermore, in step (3), the adhesive is cashew nut shell oil modified phenolic resin.

[0055] Furthermore, in step (3), the stirring time is continued for 10-30 min.

[0056] Further, in step (4), the extrusion is to sequentially cover and extrude the intermediate base material and the friction performance improver onto the adhesive, forming a four-layer structure of friction performance improver, base material, adhesive and backing plate from top to bottom.

[0057] Furthermore, in step (4), the extrusion temperature is 80-95 ℃ and the extrusion speed is 40-50 m / min.

[0058] Furthermore, in step (4), the pressing pressure is 20 MPa, the temperature is 180 ± 5 ℃, and the holding time is 6-10 minutes; the number of times of venting is 1-3, and the venting time is 10-30 s.

[0059] Further, in step (4), the heat treatment operation is as follows: first, raise the temperature to 160-180 ℃ for 3-5 h, hold the temperature for 3-5 h, then raise the temperature to 180-190 ℃ for 1-3 h, hold the temperature for 3-5 h, then raise the temperature to 200-210 ℃ for 1-2 h, hold the temperature for 2-4 h, then raise the temperature to 220-240 ℃ for 1-2 h, hold the temperature for 1-3 h.

[0060] Furthermore, in step (4), the biomimetic groove is formed with a width of 0.5-1.2 mm, a depth of 0.3-0.8 mm, and a coverage of 15-25%.

[0061] Fourthly, the present invention provides the application of the friction pad described in the second aspect in vehicle disc or drum brakes.

[0062] Compared with the prior art, the present invention has achieved the following beneficial effects: The addition of potassium titanate whiskers to the friction pads provided by this invention can reduce the thermal compression deformation of asbestos-free organic friction materials. Potassium titanate whiskers also stabilize the friction coefficient and improve the material's resistance to thermal degradation at high temperatures. Appropriate addition of potassium titanate whiskers can reduce the high-temperature wear rate of friction materials. Friction materials with 8%~12% potassium hexatitanate exhibit the best overall performance in terms of physical properties, internal shear strength, mechanical properties, wear performance, and transmission noise.

[0063] The friction pad provided by this invention, through the synergistic cooperation of the surface friction material, the intermediate base material, the bottom adhesive and the back plate, has strong friction coefficient stability under high temperature conditions, reduces braking noise and vibration, extends the service life of the friction pad and the brake disc, and uses environmentally friendly materials to meet the requirements of copper-free and asbestos-free. Attached Figure Description

[0064] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0065] Figure 1 This is a schematic diagram of the friction plate composition of the present invention; Figure 2 This is a schematic diagram of the biomimetic groove of the friction plate of the present invention; Figure 3This is a graph showing the effect of potassium hexatitanate content on the porosity and density of friction materials; Figure 4 This is a graph showing the effect of different potassium hexatite contents on the hardness and compressive deformation of friction materials. Detailed Implementation

[0066] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0067] In a first aspect, the present invention provides a friction material composition, wherein the raw materials of the friction material composition include: a friction performance improver, a base material, and a binder; The friction performance improver includes high-hardness ceramic fibers, graphene-modified resin, friction modifier, and filler; The base material includes an aramid fiber-epoxy resin composite layer, potassium hexatitanate, and adhesive additives. The adhesive is composed of nitrile rubber, modified phenolic resin, potassium hexatitanate, coupling agent, talc, and curing accelerator.

[0068] Furthermore, in the friction material composition, the friction performance improver accounts for 40%-50% of the total mass, the base material accounts for 30%-40% of the total mass, and the binder accounts for 10%-20% of the total mass. When the proportion of the friction performance improver is less than 40%, the wear-resistant and high-temperature resistant components are insufficient, leading to accelerated high-temperature thermal decay and faster wear rate of the friction pads; when it is greater than 50%, the material hardness is too high, brittleness increases, easily causing abnormal braking noise, and easily aggravating wear of the mating disc. When the proportion of the base material is less than 30%, the heat insulation and load-bearing buffering effects are insufficient, and frictional heat is easily and quickly conducted to the bottom layer, resulting in decreased thermal decay performance; when it is greater than 40%, the toughness is too high, rigidity is insufficient, braking is prone to fatigue and lag, and excessive porosity leads to poor stability. When the proportion of the binder is less than 10%, the interfacial bonding strength is insufficient, and delamination and peeling failure are prone to occur; when it is greater than 20%, there are too many organic components, which are prone to carbonization and softening at high temperatures, reducing shear strength and increasing braking vibration noise. This ratio range can achieve the synergistic effect of surface wear resistance, middle heat insulation and load bearing, and bottom bonding and buffering, optimize material hardness, porosity and compression deformation, improve the stability of high temperature friction coefficient, reduce braking noise and vibration, and at the same time ensure molding processability and interface bonding strength.

[0069] Furthermore, the high-hardness ceramic fiber is silicon carbide ceramic fiber. Silicon carbide ceramic fiber serves as the core reinforcing component, enhancing the hardness and wear resistance of the friction layer.

[0070] Furthermore, the graphene-modified resin is a graphene-modified cashew nutshell oil-modified phenolic resin. Cashew nutshell oil-modified phenolic resin has better toughness and higher heat resistance than ordinary phenolic resin, improving the formability and interfacial bonding performance of friction materials. After modification with graphene, the graphene, with its high thermal conductivity, high strength, and sheet-like barrier effect, can be uniformly dispersed within the resin matrix, effectively improving the resin's heat resistance stability, slowing down the carbonization and decomposition rate of the resin at high temperatures, and reducing thermal decay. Simultaneously, it enhances the interfacial bonding force between the resin and silicon carbide ceramic fibers and friction modifiers, reducing filler shedding and improving overall mechanical strength and impact resistance. It also optimizes the quality of the friction interface transfer film, further stabilizing the friction coefficient, suppressing braking noise, and achieving stable friction performance under wide temperature range conditions.

[0071] Furthermore, the friction modifier is a mixture of graphite and antimony sulfide; the mass ratio of graphite to antimony sulfide is 1:0.8-1.2. Graphite is a layered solid lubricant that can form a continuous lubrication transfer film at the friction interface, reducing abrasive wear and effectively suppressing low-speed braking squealing and vibration noise. Antimony sulfide has excellent high-temperature resistance and is not easily oxidized and decomposed at high temperatures, which can significantly improve the stability of the friction coefficient in the medium and high temperature range and alleviate thermal fade. The combination of the two in this ratio can achieve a synergistic balance between lubrication performance and high-temperature friction stability: too high a proportion of graphite can easily lead to a low friction coefficient and soft braking; too high a proportion of antimony sulfide can easily lead to increased material brittleness and accelerated wear. The limited ratio of this invention can maintain a stable friction coefficient in a wide temperature range from room temperature to 350℃, while reducing damage to mating parts and improving the overall service life of the friction pads.

[0072] Furthermore, the filler is a mixture of talc and calcium carbonate in a mass ratio of 1-3:1.

[0073] Furthermore, the mass ratio of silicon carbide ceramic fiber to graphene-modified resin is 1:1.2~1.5.

[0074] Furthermore, in the friction performance improver, silicon carbide ceramic fiber accounts for 35%-40%, graphene modified resin accounts for 48%-52% of the total mass, friction modifier accounts for 10-13%, and the remainder is filler.

[0075] Furthermore, the mass ratio of the aramid fiber and epoxy resin composite layer to potassium hexatitanate is 1.5~2:1.

[0076] Furthermore, the preparation method of the aramid fiber and epoxy resin composite layer is as follows: After plasma surface treatment, aramid fibers are immersed in a mixture of E-51 epoxy resin and curing agent for impregnation, and then pre-cured to form an aramid fiber-epoxy resin composite layer.

[0077] Aramid fibers possess high strength, high toughness, and good temperature resistance, but their surface inertness and weak interfacial bonding with the matrix resin make them prone to fiber pull-out and delamination failure. This invention activates the aramid fiber surface through plasma surface treatment, increasing surface roughness and the number of active groups. A composite layer is then formed through epoxy resin impregnation and pre-curing, significantly enhancing the interfacial adhesion strength between the aramid fiber and the overall friction material system. The composite layer combines the high toughness of aramid with the adhesiveness of epoxy resin, effectively buffering braking impact stress, inhibiting crack propagation, and improving the fatigue and crack resistance of the friction material. Simultaneously, this composite layer serves as an intermediate transition layer, achieving a rigidity-toughness gradient transition between the surface and the bottom layer, reducing interfacial stress concentration, minimizing braking noise, and synergistically enhancing thermal insulation with potassium hexatitanate, further improving high-temperature friction stability.

[0078] Furthermore, the plasma surface treatment specifically involves low-temperature, ambient-pressure air plasma treatment with a treatment power of 300-400 W, a treatment distance of 8-12 mm, a scanning speed of 8-12 mm / s, and a treatment time of 60-120 s.

[0079] Furthermore, the adhesive is cashew nut shell oil modified phenolic resin.

[0080] Furthermore, the immersion time is 10-30 minutes; the immersion temperature is 20-30 ℃.

[0081] Furthermore, the pre-curing temperature is 75-85 ℃; the time is 10-20 min.

[0082] Furthermore, the mass ratio of aramid fiber to epoxy resin is 1:0.8-1.

[0083] Furthermore, the curing agent is an amine-based curing agent, preferably diethylenetriamine.

[0084] Furthermore, in the base material, the aramid fiber and epoxy resin composite layer accounts for 55%-60% of the total mass; potassium hexatitanate accounts for 30%-35% of the total mass; the remainder is coupling agent and talc filler. The silane coupling agent KH550 can form chemical bonds between the aramid-epoxy composite layer, potassium hexatitanate whiskers, and the resin matrix, improving the inorganic-organic interface compatibility and enhancing the overall bonding strength; talc can adjust the porosity and hardness of the base material, improve the material's molding fluidity, and simultaneously play a role in reducing friction and providing heat insulation. It synergistically optimizes the compression deformation and high-temperature stability of the friction material with potassium hexatitanate. The mass ratio of coupling agent to talc is 1-2:4-8.

[0085] Furthermore, the mass ratio of nitrile rubber, modified phenolic resin, and potassium hexatitanate is 1:1.2-1.5:0.5-0.7.

[0086] Furthermore, the curing accelerator is an imidazole curing accelerator, specifically 2-ethyl-4-methylimidazolium; the coupling agent is a silane coupling agent KH550.

[0087] Furthermore, the modified phenolic resin is a cashew nut shell oil-modified phenolic resin, and the preparation method of the modified phenolic resin is as follows: Phenol and formaldehyde are heated, hydrochloric acid is added to react, then cashew nut shell oil is added, and the reaction is continued by heating. After the reaction is completed, the pH is adjusted to 7-8, the mixture is distilled under reduced pressure, and then cooled to obtain the final product.

[0088] Cashew nut shell oil contains long-chain flexible alkyl structures. After chemical grafting modification of phenolic resin, it can effectively improve the defects of pure phenolic resin, such as high brittleness and poor toughness, and enhance the resin's flexibility and impact resistance. At the same time, the introduction of flexible chain segments can reduce the resin's curing shrinkage rate and reduce internal stress cracking during the molding of friction materials and high-temperature use. The natural components of cashew nut shell oil have excellent heat resistance and stability, which can improve the resin's high-temperature carbonization resistance and reduce the risk of thermal degradation. It can also improve the interfacial wettability between the resin and inorganic fillers and fibers, enhance the overall bonding strength, suppress braking noise and vibration, and achieve bio-based environmentally friendly modification, reducing the content of harmful substances.

[0089] Furthermore, the molar ratio of phenol, formaldehyde, and cashew nut shell oil is 1:1.0-1.4:0.2-0.5.

[0090] Further, after reaching 75-85 °C, add hydrochloric acid and react for 60-100 min.

[0091] Further, after adding cashew nut shell oil, the temperature is raised to 90-95 ℃, and the reaction is carried out for 40-80 min.

[0092] Furthermore, the preparation method of the graphene-modified resin is as follows: Graphene powder was added to anhydrous ethanol, stirred, then a coupling agent was added, and the mixture was allowed to stand to obtain a graphene dispersion. The cashew nut shell oil-modified phenolic resin is heated to 50-60 ℃, graphene dispersion is added, and the mixture is stirred at a constant temperature. After stirring, vacuum degassing is performed to obtain the final product.

[0093] Furthermore, the graphene powder has a particle size of ≤ 5 μm.

[0094] Furthermore, the coupling agent is a silane coupling agent, preferably KH550. The silane coupling agent KH550 has amino functional groups and siloxane groups at both ends of its molecule, which can build chemical bonding bridges between the inorganic phase (potassium hexatitanate, talc, silicon carbide ceramic fibers) and the organic phase (resin, rubber matrix), improving the dispersibility of inorganic fillers in the organic matrix and preventing filler agglomeration; effectively enhancing the bonding strength of the organic-inorganic interface, reducing interface defects and stress concentration; and simultaneously enhancing the anchoring effect between fibers, whiskers, and the resin matrix, reducing filler detachment and interface peeling problems during high-temperature braking, and improving the overall mechanical properties, thermal stability, and wear resistance of the friction material.

[0095] Furthermore, the stirring time is 20-40 min; the rotation speed is 1400-1600 r / min.

[0096] Furthermore, the settling time is 8-15 minutes.

[0097] Furthermore, the constant temperature stirring time is 40-80 min; the rotation speed is controlled at 1000-1400 r / min.

[0098] Furthermore, the vacuum degassing time is 20-40 min.

[0099] Secondly, the present invention provides a friction plate, which includes four parts: a back plate, a bottom layer, an intermediate layer and a surface layer. The bottom layer, intermediate layer, and top layer are prepared from the adhesive, base material, and friction modifier described in the first aspect.

[0100] The friction pad provided by this invention, through the synergistic cooperation of the surface friction material, the intermediate base material, the bottom adhesive and the back plate, has a strong friction coefficient stability under high temperature conditions, reduces braking noise and vibration, extends the service life of the friction pad and the brake disc, and uses environmentally friendly materials to meet the requirements of copper-free and asbestos-free.

[0101] Furthermore, the friction pad surface is provided with asymmetric spiral grooves. The conch shell-type asymmetric spiral groove structure achieves uniform chip removal, continuous heat dissipation, and stress relief. The streamlined spiral structure effectively eliminates stress concentration at groove sharp corners, preventing the propagation of micro-cracks at the edges during braking and reducing the wear rate. The grooves can quickly dissipate friction dust and high-temperature heat during high-speed continuous braking, improving interface heat dissipation efficiency and suppressing local overheating and thermal decay. Simultaneously, the asymmetric spiral texture can uniformly disturb the air film at the friction interface and disrupt the resonant frequency, significantly reducing high-frequency braking squeal and vibration. In addition, this groove structure can stabilize the contact state of the friction pair, maintain a stable friction coefficient, improve braking stability under high and low speeds and various dry and wet operating conditions, and extend the mating life of the friction pad and brake disc.

[0102] Furthermore, the asymmetric spiral groove is a conch shell spiral texture, with a width of 0.5-1.2mm, a depth of 0.3-0.8mm, and a groove coverage area of ​​15%-25%.

[0103] Furthermore, the back plate is made of low-carbon steel plate, which is selected from Q235 and SPCC.

[0104] Thirdly, the present invention provides a method for preparing the friction pad described in the second aspect, comprising the following steps: (1) Add the coupling agent to the solvent and stir, let stand, and obtain the coupling agent solution; add talc powder to the solvent and stir to make a filler slurry; The modified phenolic resin is heated to 50-60 ℃, nitrile rubber is added, and the mixture is stirred at a constant temperature to obtain a resin-rubber blend system; coupling agent solution, curing accelerator, filler slurry, and potassium hexatitanate are added in sequence, stirred, allowed to stand, defoamed, coated on the backing plate, and dried. (2) Mix high-hardness ceramic fibers, friction modifiers and fillers, and stir; add graphene-modified resin and continue stirring until particles with a particle size of 2-5 mm are formed to obtain a surface friction performance improver. (3) Mix the aramid fiber and epoxy resin composite layer with potassium hexatitanate and coupling agent, and stir; add adhesive additives and continue stirring to form the intermediate layer base material mixture; (4) Perform the following steps in sequence: extrusion, pressing, heat treatment, grinding, and biomimetic groove forming to obtain the final product.

[0105] Furthermore, the back panel also includes a pre-processing operation, which includes: selection and cutting of back panel raw materials, precision stamping, and surface treatment.

[0106] Furthermore, the specific operation of selecting and cutting the backing material is as follows: select a backing material with a thickness of 1.5-3 mm according to the friction plate specifications; cut the roll material into a rectangular blank that fits the mold using a shearing machine, with the tolerance controlled within ±0.2 mm.

[0107] Furthermore, the specific operation of the precision stamping forming is as follows: stamping is performed using a progressive die or a compound die to complete the blanking, punching, and bending processes in one go. After forming, the flatness tolerance of the back plate is ≤ 0.1 mm, and the hole diameter tolerance is ± 0.05 mm. After stamping, the burrs are removed, and the edges are treated with a grinding wheel or a chamfering machine.

[0108] Further, the specific operation of the surface treatment is as follows: immerse the back panel in an alkaline degreasing agent at 50-60 ℃ for 10-15 minutes to remove surface oil stains; then rinse with clean water and dry. Sandblasting roughening: Quartz sand or alumina sand is used to sandblast the steel backing surface at a pressure of 0.4-0.6 MPa to achieve a surface roughness of Ra 3.2-6.3 μm.

[0109] Furthermore, the alkaline degreasing agent is a mixture of sodium hydroxide and sodium carbonate, with a mass ratio of sodium hydroxide to sodium carbonate of 1:1 to 1.2. Sodium hydroxide is highly alkaline and has a fast degreasing rate, which can quickly saponify and decompose mineral oil, grease, and other oil stains on the backplate surface; sodium carbonate has good buffering properties and a mild and stable alkalinity, which can maintain the pH stability of the degreasing solution, avoid excessive corrosion of the steel backplate surface by strong alkali, and at the same time disperse and emulsify oil stains and prevent secondary adhesion. The two are compounded in this ratio, which has both efficient degreasing and surface protection functions. It can thoroughly remove residual oil stains from the backplate stamping, ensuring a strong bond between subsequent sandblasting and the adhesive layer, while avoiding excessive corrosion of the steel plate and abnormal surface roughness, improving the consistency of backplate pretreatment, and ensuring the overall interface bonding strength and reliability of the friction pad.

[0110] Furthermore, in step (1), the coupling agent is a silane coupling agent KH550.

[0111] Furthermore, in step (1), the solvent is anhydrous ethanol.

[0112] Further, in step (1), the curing accelerator is an imidazole curing accelerator, specifically 2-ethyl-4-methylimidazole. The curing accelerator is mainly used to reduce the curing activation energy of cashew nut shell oil modified phenolic resin and epoxy resin, accelerate the resin crosslinking reaction rate, shorten the heat treatment molding time, make the internal crosslinking of the friction material more complete, and improve the overall density and heat resistance stability. The present invention selects 2-ethyl-4-methylimidazole, which, compared with amine and acid anhydride curing accelerators, has moderate curing activity and a wide applicable temperature range, and can achieve a step-by-step reaction matching of medium and low temperature pre-curing and high temperature deep curing; after curing, the resin crosslinking structure is dense and has excellent heat resistance, which can effectively improve the high temperature carbonization resistance of the friction material; at the same time, the accelerator has good compatibility with nitrile rubber and modified phenolic resin, is not prone to generating by-products, avoids interface defects, improves the shear strength of the adhesive layer and the overall mechanical properties, and reduces the risk of interface failure during braking.

[0113] Further, in step (1), the coupling agent is added to the solvent and stirred for 20-40 min; the stirring speed is 1400-1600 r / min; and it is allowed to stand for 8-15 min.

[0114] Furthermore, in step (1), the mixture is stirred at a constant temperature for 50-70 minutes.

[0115] Further, in step (1), after adding coupling agent solution, curing accelerator, filler slurry and potassium hexatitanate, stir for 40-80 min; let stand for 20-25 h.

[0116] Furthermore, in step (2), the stirring time is 20-30 min.

[0117] Furthermore, in step (2), if the material is loose after adding graphene-modified resin, 5%-8% ethanol can be added as a wetting agent.

[0118] Furthermore, in step (3), the stirring time is 10-20 min; the rotation speed is 1000-1200 r / min.

[0119] Furthermore, in step (3), the adhesive is cashew nut shell oil modified phenolic resin.

[0120] Furthermore, in step (3), the stirring time is continued for 10-30 min.

[0121] Further, in step (4), the extrusion is to sequentially cover and extrude the intermediate base material and the friction performance improver onto the adhesive, forming a four-layer structure of friction performance improver, base material, adhesive and backing plate from top to bottom.

[0122] Furthermore, in step (4), the extrusion temperature is 80-95 ℃ and the extrusion speed is 40-50 m / min.

[0123] Furthermore, in step (4), the pressing pressure is 20 MPa, the temperature is 180 ± 5 ℃, and the holding time is 6-10 minutes; the number of times of venting is 1-3, and the venting time is 10-30 s.

[0124] Further, in step (4), the heat treatment operation is as follows: first, raise the temperature to 160-180 ℃ for 3-5 h, hold the temperature for 3-5 h, then raise the temperature to 180-190 ℃ for 1-3 h, hold the temperature for 3-5 h, then raise the temperature to 200-210 ℃ for 1-2 h, hold the temperature for 2-4 h, then raise the temperature to 220-240 ℃ for 1-2 h, hold the temperature for 1-3 h.

[0125] Furthermore, in step (4), the biomimetic groove is formed with a width of 0.5-1.2 mm, a depth of 0.3-0.8 mm, and a coverage of 15-25%.

[0126] Fourthly, the present invention provides the application of the friction pad described in the second aspect in vehicle disc or drum brakes.

[0127] The preparation methods of some materials in the embodiments of the present invention are as follows: (1) Preparation of bio-based cashew nut shell oil modified phenolic resin: Raw materials: phenol, formaldehyde, cashew nut shell oil, molar ratio 1:1.2:0.3, combined with concentrated hydrochloric acid catalyst (36% by mass) and sodium hydroxide (30% by mass solution) neutralizer.

[0128] Polycondensation reaction: Phenol and 37% formaldehyde aqueous solution were added to the reactor, stirred and mixed, and then heated to 80 °C. Concentrated hydrochloric acid catalyst (1% of the mass of phenol) was added dropwise, and the reaction was carried out at a constant temperature and stirred for 90 min. Cashew shell oil was then added, the temperature was raised to 95 °C, and the reaction was carried out at a constant temperature and stirred for 60 min.

[0129] Neutralization and discharge: After the reaction is completed, the temperature is lowered to 65 ℃, and 30% sodium hydroxide aqueous solution is added dropwise to adjust the pH to 7; under vacuum conditions of -0.08~-0.09 MPa and 95-105 ℃, water and low molecular weight volatiles are removed by vacuum distillation, and after cooling, cashew shell oil modified phenolic resin is obtained.

[0130] (2) Preparation of phenolic resin with cashew nut shell oil as the resin matrix in graphene-modified resin: Raw material preparation: Cashew shell oil modified phenolic resin was selected as the matrix resin, multilayer graphene powder (particle size ≤ 5 μm) was selected, and ethanol solvent and silane coupling agent KH550 were used.

[0131] Pre-dispersion treatment: Graphene powder was added to anhydrous ethanol and stirred at 1500 r / min for 30 min. Then, KH550 coupling agent was added and allowed to stand for 10 min to fully disperse the powder and prevent graphene agglomeration. The mass ratio of graphene powder, anhydrous ethanol and KH550 was 1:22:0.15.

[0132] Modified blending: The cashew nut shell oil-modified phenolic resin was heated to 55 °C, and graphene dispersion was slowly added dropwise. The mixture was stirred at a constant temperature for 60 min at a speed controlled at 1200 r / min to ensure that the graphene was uniformly coated in the resin molecular chains. The mass ratio of cashew nut shell oil-modified phenolic resin, graphene, anhydrous ethanol, and KH550 was 100: 3.0: 66.0: 0.45.

[0133] Post-processing: After stirring, vacuum degassing was performed for 30 min to remove solvent residue, and graphene-modified phenolic resin was obtained, with the viscosity controlled at 180-220 mPa·s.

[0134] (3) Preparation of the aramid fiber and epoxy resin composite layer: Fiber pretreatment: Continuous aramid fibers were selected and treated with low-temperature atmospheric pressure air plasma at a power of 350 W, a treatment distance of 10 mm, a scanning speed of 10 mm / s, and a treatment time of 90 s to activate the fiber surface and improve resin wettability.

[0135] Preparation of impregnation solution: E-51 epoxy resin: curing agent (methyltetrahydrophthalic anhydride) = 100:30 by mass ratio, stir evenly at room temperature to obtain epoxy resin impregnation solution.

[0136] Impregnation: The plasma-treated aramid fibers are continuously immersed in the impregnation solution to fully wet them. The amount of resin applied is controlled to be 40% of the mass of the aramid fibers. Excess resin is squeezed out to ensure that the resin evenly coats the fibers.

[0137] Pre-curing (semi-curing): The impregnated fibers are sent into an oven and pre-cured at 85 ℃ for 40 min to obtain a composite layer of aramid fiber and epoxy resin. At this time, the resin is initially cross-linked and does not flow, and can be cut into short fibers or sheets for later use.

[0138] Crush and prepare for use: Cut the aramid fiber and epoxy resin composite layer into short pieces of 3-8 mm for use in the subsequent mixing of intermediate layer base material, ensuring uniform mixing with potassium hexatitanate, talc powder and coupling agent.

[0139] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0140] Example 1 This embodiment provides a method for preparing a friction pad, the specific steps of which are as follows: (1) Selection and cutting of back plate raw materials: Low carbon steel plate (Q235) is selected, and the thickness is set to 1.5-3 mm according to the specifications of the friction plate. The coil is cut into rectangular blanks that fit the mold by a shearing machine, and the tolerance is controlled within ±0.2 mm.

[0141] Precision stamping: Using progressive dies or compound dies for stamping, blanking, punching (positioning holes / mounting holes), and bending (if there is a need for flanging) are completed in one step. The flatness tolerance of the back panel after forming is ≤ 0.1 mm, and the hole diameter tolerance is ± 0.05 mm.

[0142] After stamping, remove burrs and use a grinding wheel or chamfering machine to process the edges to prevent subsequent scratches on the friction layer or assembled parts.

[0143] Surface treatment: Degreasing and greasing. Immerse the steel back in an alkaline degreasing agent (a mixture of sodium hydroxide and sodium carbonate) at 50-60℃ for 10-15 minutes to remove surface oil stains; then rinse with clean water and dry.

[0144] Sandblasting roughening: Quartz sand or alumina sand is used to sandblast the steel backing bonding surface at a pressure of 0.4-0.6 MPa to make the surface roughness reach Ra 3.2-6.3 μm, forming a micro-rough surface and enhancing the mechanical bonding with the base adhesive.

[0145] In alkaline degreasing agents, sodium hydroxide and sodium carbonate are used in a mass ratio of 1:1 to 1:1.2. In actual production, the two alkalis are dissolved in water according to this mass ratio to prepare an alkaline degreasing solution with a concentration of 5%-8%, which is used for degreasing the back panel.

[0146] Ingredients: The components are set according to the formula of the filler in the third part of the raw materials. An automatic weighing and batching system is used for batching. A high-speed shear mixer (2000 rpm) is used instead of a ball mill to shorten the mixing time to 30 minutes.

[0147] (2) Underlayer adhesive The total mass of the bottom adhesive is 20 parts: 10.5 parts modified phenolic resin, 7 parts nitrile rubber, 2.5 parts potassium hexatitanate, 0.2 parts KH550, 2.5 parts talc, and 0.3 parts curing accelerator.

[0148] Add coupling agent KH550 to anhydrous ethanol and stir until homogeneous. Let stand for 10 min to allow it to dissolve completely, thus obtaining a coupling agent solution. Add talc powder to anhydrous ethanol and stir at high speed (1500 r / min) for 30 min to prepare a filler slurry to prevent agglomeration.

[0149] Modified phenolic resin was added to the reactor, the temperature was raised to 50-60 ℃, and nitrile rubber latex was slowly added. The mixture was stirred at a constant temperature for 60 min to form a uniform resin-rubber blend system.

[0150] Add coupling agent solution, 2-ethyl-4-methylimidazole, filler slurry and potassium hexatitanate in sequence; continue stirring for 30 min, control the viscosity of the primer at 150-200 mPa·s to ensure no sagging or pinholes during spraying / rolling; filter with a 200-mesh filter to remove impurities; let stand at room temperature for 24 h to defoam, then it can be used for backplate coating.

[0151] After the adhesive is mixed and prepared, the backing plate is coated and dried: the thickness of the spray or roller coating is controlled at 10-20 μm; put it in the oven and keep it at 120-150 ℃ for 20-30 min to dry, ensuring that the base adhesive is completely cured and there is no dripping.

[0152] (3) Friction performance improver The mixture contains 17 parts silicon carbide ceramic fiber, 22.5 parts graphene-modified resin, 1 part graphite, 0.83 parts antimony sulfide, 2 parts talc, 1 part calcium carbonate, 0.67 parts filler, and a total of 45 parts by weight of friction performance improver.

[0153] Add silicon carbide ceramic fibers, a mixture of graphite and antimony sulfide, and a mixture of talc and calcium carbonate to a high-speed mixer and stir at 1000-1500 r / min for 10-15 min at room temperature to initially disperse the solid components. Slowly spray in graphene-modified cashew nut shell oil-modified phenolic resin liquid or add resin powder, and continue stirring for 20-30 min to use the frictional heat of stirring to coat the solid particles with resin. If the material is loose, add 5%-8% ethanol as a wetting agent and stir until particles with a diameter of 2-5 mm are formed to prevent subsequent molding and stratification. Prepare granular material for later use.

[0154] (4) Intermediate layer base material Dosage matching (suitable for a total of 100 parts of friction material system), intermediate layer base material 35 parts by weight, including 20.3 parts of aramid fiber and epoxy resin composite layer, 7.5 parts of potassium hexatitanate, 0.4 parts of KH550 coupling agent, 5.8 parts of talc powder, and 1.0 part of graphene modified cashew nut shell oil modified phenolic resin.

[0155] Aramid fibers and epoxy resin composite layers are cut into short fibers and added to a high-speed mixer along with potassium hexatitanate and KH550 coupling agent. The mixture is stirred at 1200 r / min for 15 min at room temperature to achieve initial dispersion. Cashew nut shell oil-modified phenolic resin is added as a binding agent, and stirring is continued for 20 min to allow potassium hexatitanate whiskers to adhere evenly to the surface of the composite fibers, forming a transition layer mixture (intermediate layer base material). This mixture is then simultaneously composited with the surface and bottom layer components.

[0156] (5) Extrusion: The prepared intermediate base material and friction performance improver are extruded sequentially onto the binder prepared in step (2) through a screw extruder, forming a four-layer structure from top to bottom: friction performance improver, base material, binder, and backing plate. In this process, the screw temperature is controlled at 90 ℃ and the extrusion speed is 45 m / min.

[0157] (6) Pressing: Weigh the product according to the amount of material fed into the 430 / 240 / 3.6 product, and weigh each piece 0.68 kg. Control the winding pattern to 5.3 and make blanks. Control the pressure to 20 MPa and the temperature to 180 ± 5 ℃ during the pressing process; the holding time is 6-10 minutes; release air twice in the middle, and the air release time is 20 s.

[0158] (7) Heat treatment: First, heat to 170℃ for 4 hours and hold for 4 hours. Then heat to 190℃ for 2 hours and hold for 4 hours. Then heat to 210℃ for 1 hour and hold for 3 hours. Then heat to 230℃ for 1 hour and hold for 2 hours. The total heat treatment is 21 hours.

[0159] (8) Grinding discs: Use 40-mesh abrasive belt for roughing, then use 60-mesh abrasive belt for medium-level processing, and finally use 80-mesh abrasive belt for fine processing to ensure that the flatness is within 0.05 mm.

[0160] (9) Drilling and chamfering: According to the hole size required by the drawing, use a fully automatic drilling machine imported from Germany to process the hole and adopt biomimetic grooves with a width of 0.8 mm, a depth of 0.4 mm, and a coverage of 15%. After cleaning the friction plate, spray paint and dry it, and install the alarm, shock absorber, and spring.

[0161] Example 2 The difference between this embodiment and Embodiment 1 lies in the potassium hexatate content. In this embodiment, the total potassium hexatate content is 8%; the mass ratio of the intermediate layer to the bottom layer is 3:1, and any missing mass is made up by filler to ensure that the total mass remains unchanged.

[0162] Example 3 The difference between this embodiment and Example 1 lies in the potassium hexatate content. In this embodiment, the total potassium hexatate content is 12%; the mass ratio of the intermediate layer to the bottom layer is 3:1, and talc powder is reduced to maintain the total mass.

[0163] Figure 1 This is a schematic diagram of the friction plate composition of the present invention; Figure 2 This is a schematic diagram of the biomimetic groove of the friction plate of the present invention; Figure 3 This is a graph showing the effect of potassium hexatitanate content on the porosity and density of friction materials; Figure 4 This is a graph showing the effect of different potassium hexatite contents on the hardness and compressive deformation of friction materials.

[0164] Comparative Example 1 The surface friction material does not use graphene-modified cashew nut shell oil-modified phenolic resin, but is replaced with ordinary unmodified phenolic resin. The remaining components, dosages, and processes are the same as in Example 1.

[0165] Comparative Example 2 The intermediate transition layer does not use an aramid fiber-epoxy resin composite layer, but uses aramid fiber alone. The remaining components, dosages, and processes are the same as in Example 1.

[0166] Comparative Example 3 Potassium hexatitanate whiskers are added only to the intermediate transition layer, and no potassium hexatitanate is added to the bottom adhesive. The total amount added is the same as in the example, and the remaining components and processes are the same as in Example 1.

[0167] Comparative Example 4 Adjust the proportions of the three-layer components: 30% for the top layer, 50% for the middle layer, and 20% for the bottom layer. Keep the internal proportions of the core components unchanged, and keep the rest of the process the same as in Example 1.

[0168] Comparative Example 5 Compared with Example 1, the difference lies in the content of potassium hexatitanate. In this comparative example, potassium hexatitanate is not added, and the missing mass is made up by filler to ensure that the total mass remains unchanged. The rest of the process is the same as in Example 1.

[0169] Comparative Example 6 Compared with Example 1, the difference lies in the potassium hexatitanate content. In this comparative example, the total potassium hexatitanate content is 4%; the mass ratio of the intermediate layer to the bottom layer is 3:1, and the missing mass is made up by filler to ensure that the total mass remains unchanged. The rest of the process is the same as in Example 1.

[0170] Comparative Example 7 Compared with Example 1, the difference lies in the potassium hexatitanate content. In this comparative example, the total potassium hexatitanate content is 16%; the mass ratio of the intermediate layer to the bottom layer is 3:1. If the mass exceeds the limit, the talc powder is reduced to ensure that the total mass remains unchanged. The remaining processes are the same as in Example 1.

[0171] Performance testing: 1. Thermal decay rate: According to the constant speed friction test machine method specified in GB / T 5763-2018 "Automotive Brake Liners", the friction coefficient of the friction material at room temperature and high temperature is determined, and the thermal decay rate is calculated. The specific steps are as follows: (1) Sample preparation: The friction material is processed into a standard sample of 25 mm × 25 mm × 6 mm, the surface is polished and oil and impurities are removed; (2) Reference friction coefficient test: Under the conditions of 100 ℃, 0.98 MPa pressure and 0.42 m / s linear velocity, the friction is stable for 10 min, and the reference friction coefficient at room temperature μ1 is recorded; (3) High temperature decay test: The temperature is raised to 350 ℃, and the friction is stable for 10 min under the same pressure and speed, and the high temperature friction coefficient μ2 is recorded; (4) Calculation of thermal decay rate: (μ1-μ2) / μ2*100%.

[0172] Indicator Explanation: A lower thermal decay rate indicates a smaller decrease in the coefficient of friction at high temperatures, and better high-temperature resistance and thermal stability. The friction material prepared by this invention has a thermal decay rate of ≤12%, which is significantly better than conventional copper-free friction materials.

[0173] 2. Heat recovery rate: (5) Cooling recovery section: After natural cooling down to 100℃, stabilize friction again for 10 minutes, and measure the friction coefficient μ3 after cooling recovery. Heat recovery rate calculation: μ3 / μ1×100%: The closer the heat recovery rate is to 100%, the more fully the friction coefficient rebounds after high temperature heating, and the stronger the stability of repeated braking.

[0174] 3. Wear rate: The wear rate is calculated using the formula (m0-m1) / (ρ×F×L)×100%; Where m0 is the mass of the sample before wear (g), m1 is the mass of the sample after wear (g), and ρ is the measured density of the friction material sample (g / cm³).3 F is the test normal pressure (N, the national standard takes 0.98MPa as the corresponding pressure), and L is the total friction sliding distance (m).

[0175] 4. Interface bonding strength test (refer to ASTM D3164): The shear strength of the friction material adhesive layer and the backing plate (steel) prepared by this invention is ≥15MPa.

[0176] 5. Failure mode: 80% is cohesive failure, indicating that the interfacial bonding is superior to traditional processes.

[0177] 6. Environmental testing: Copper content: ICP-OES test result <0.01wt%; Asbestos detection: XRD full-spectrum analysis did not detect any characteristic peaks of asbestos.

[0178] Test conditions: According to GB / T 5763-2018, constant speed friction tester, pressure 0.98 MPa, linear speed 0.42 m / s; potassium hexatitanate content is the percentage of the total mass of all friction materials (excluding steel backing).

[0179] The performance test results are shown in Tables 1 and 2.

[0180] Table 1 Performance test results of Examples 1-3

[0181] The thermal decay rate, thermal recovery rate, and wear rate of the samples in Examples 1-3 were tested respectively, and the results are as follows: When the total potassium hexatate content is 0% (Comparative Example 5) and 4% (Comparative Example 6), the material lacks a high-temperature resistant reinforcing and insulating phase. At high temperatures, the resin is prone to thermal decomposition, resulting in a significantly increased thermal decay rate, a substantial increase in wear rate, poor thermal recovery performance, and insufficient braking stability. When the total potassium hexatate content is 8%–12% (Examples 1-3), the whisker reinforcement, pore buffering, and thermal insulation / friction stabilization effects achieve the best balance, with a thermal decay rate ≤9.5%, a thermal recovery rate ≥92.8%, and a wear rate ≤0.91×10⁻⁶. -7 cm 3 / / (N·m), with a stable friction coefficient, good high-temperature resistance, and low wear, represents the optimal ratio range for this invention.

[0182] Example 1: With a potassium hexatate content of 10%, the material falls within the optimal range, exhibiting the lowest thermal decay rate, highest thermal recovery rate, and lowest wear rate, resulting in the best overall friction braking performance. When the total potassium hexatate content reaches 16%, excessive inorganic whiskers lead to excessively high material porosity, reducing the effective contact area of ​​the friction pair. Although the thermal decay rate remains low, the thermal recovery rate decreases, the wear rate increases, and the friction coefficient becomes too low, posing a risk of brake fatigue and degrading overall performance.

[0183] In summary, by limiting the total amount of potassium hexatitanate added to 8% to 12%, this invention can significantly reduce the thermal decay of friction materials and improve their high-temperature stability and wear resistance.

[0184] Table 2 Performance test results of Comparative Examples 1-7

[0185] Comparative Example 1 uses ordinary unmodified phenolic resin for the surface layer, lacking the flexible modification of cashew nutshell oil and the thermal conductivity reinforcement of graphene. The resin is brittle, has weak high-temperature carbonization resistance, and exhibits significant friction coefficient decay at high temperatures, resulting in a significantly increased thermal degradation rate, aggravated wear, and poor frictional stability. Comparative Example 2 uses pure aramid fiber directly in the intermediate layer without epoxy resin impregnation and pre-curing to form a composite layer. The fiber-matrix interface has weak bonding, making the fibers prone to pull-out and delamination during friction, leading to increased thermal degradation rate, increased wear rate, and a decline in overall mechanical and frictional properties. In Comparative Example 3, potassium hexatite is only added to the intermediate transition layer and not to the bottom layer. Although the total addition amount is the same as in Example 1, the bottom layer lacks a thermally insulating and friction-stabilizing phase, making the adhesive layer susceptible to thermal aging and failure, increasing the overall thermal degradation rate, and decreasing high-temperature braking stability. Comparative Example 4 shows that adjusting the proportion of the three-layer structure resulted in an excessively low proportion of the surface friction layer, an excessively high proportion of the middle layer, and insufficient thickness of the friction functional layer. This led to unstable friction, accelerated wear, and deterioration of thermal degradation performance during braking. This demonstrates that the optimal protection range of the three-layer structure of the present invention, consisting of 40%-50% surface layer, 30%-40% middle layer, and 10%-20% bottom layer, is achieved.

[0186] In summary, this invention achieves comprehensive frictional performance characterized by low thermal fading, high recovery rate, and low wear through a combination of graphene-cashew shell oil composite modified resin, aramid-epoxy prepreg composite layer, potassium hexatitanate layered compounding, and a limited mass ratio of the three layers.

[0187] In this invention, potassium hexatite whiskers are added as a composite of the bottom binder and the intermediate transition layer, accounting for 0% to 16% of the total mass of the friction material. They are not a single, independent component. The amount of whiskers added directly regulates the material's pore structure, mechanical properties, and high- and low-temperature frictional stability. Room temperature mechanical property test results are as follows... Figure 4 As shown, with the total content of potassium hexatite whiskers increasing from 0% to 4%, the hard whisker skeleton inside the friction material rapidly forms, and the overall hardness of the material significantly improves; as the whisker content continues to increase from 4% to 16%, the material hardness increases slightly and gradually. In the low content range of potassium hexatite (0%–4%), the porosity increase is small, the loss of effective load-bearing area is low, and the hard reinforcement effect of whiskers is dominant; in the high content range (4%–16%), the porosity increases significantly, and the pore structure gradually develops.

[0188] Since there is a negative correlation between the compressive deformation and hardness of materials, the higher the potassium hexatate content, the stronger the material's resistance to elastic-plastic deformation, and the smaller the deformation under external load. The overall compressive deformation of friction materials shows a continuous decreasing trend. Potassium hexatate whiskers possess extremely low thermal conductivity and ultra-high temperature resistance up to 1200 ℃, forming a stable heat-insulating buffer layer at the friction interface. This effectively blocks the conduction of frictional heat to the deeper layers of the material, reducing the rate of temperature rise in the matrix. During friction, the high temperature only causes slight thermal decomposition of the surface resin and rubber, while the deep matrix bonding system maintains structural integrity, significantly inhibiting high-temperature thermal decay. Test results show that the thermal decay rate of samples without added potassium hexatate is as high as 21.6%, while the thermal decay rate of samples in the optimal addition range of 8%–12% can be controlled within 9.5%, significantly improving high-temperature frictional stability.

[0189] When the ambient temperature rises to 250 ℃, the matrix phenolic resin and nitrile rubber begin to undergo thermal decomposition, generating a small amount of gas film at the friction interface, resulting in a slight decrease in the friction coefficient. Above 300 ℃, the thermal decomposition of organic matter intensifies, forming a stable third-body wear debris friction layer at the interface. Above 350 ℃, heat continues to be conducted deeper, further deteriorating the matrix structure; the friction coefficient drops sharply after 400 ℃. Compared to whisker-free modified materials, the composite material of this invention has a higher thermal decay initiation temperature and a more gradual decay rate, with the high-temperature friction coefficient remaining stably above 0.3, demonstrating significant advantages in heat resistance and wear resistance. The friction coefficient exhibits a regular variation with whisker content, pressure, and vehicle speed: under low-speed, low-load conditions, the frictional heat output is low, and the friction coefficient is mainly determined by the effective contact area of ​​the interface.

[0190] Increasing the potassium hexatate content increases the material porosity and reduces the effective bearing area of ​​the first contact surface. Therefore, the friction coefficient decreases slightly with increasing whisker content. Under high-speed and high-load conditions, the thermal effect of the friction interface dominates. The 8%–12% whisker composite system can balance the effects of pore buffering, hard support, and thermal insulation and friction stabilization. The friction coefficient decreases slightly with increasing load and remains stable overall. When the whisker content is too low (0%, 4%), there is a lack of thermal insulation and reinforcement structure, resulting in severe high-temperature thermal decay and a significant increase in wear rate. When the whisker content is too high (16%), the porosity is too large, the effective contact area is insufficient, the braking friction coefficient is low, and braking fatigue occurs. The wear rate also increases simultaneously, further verifying that 8%–12% is the optimal range for overall performance.

[0191] During the repeated engagement and disengagement cycles of the clutch, the friction plate and the mating disc continuously wear down. Microscopic particles on the material surface undergo slight peeling and adsorption onto the mating surface, while the detached particles retain molecular chain connections with the matrix. With increasing cycle count, the interfacial contact state is continuously optimized, the fit improves, and the coefficient of friction exhibits a gradual increase followed by stabilization, ensuring consistent braking performance over long-term use. Furthermore, this invention employs an environmentally friendly solvent-free extrusion process, eliminating the need for organic solvents in the production process, making it green, pollution-free, and highly safe.

[0192] By using specialized equipment to achieve integrated extrusion coating of reinforcing fibers and adhesive layers, compared to traditional impregnation and bonding processes, the adhesive layer coating is more uniform and the thickness is controllable. The process steps are simplified, production costs are reduced, and the uniform and stable fiber-resin interface bonding is ensured, further improving the overall mechanical and frictional durability properties of the friction material from the process perspective. Comparative test results further corroborate the superiority of the technical solution of this invention: ordinary unmodified phenolic resin systems have poor high-temperature resistance and carbonization resistance, resulting in deterioration of thermal decay and wear performance; when pure aramid fibers lack an epoxy composite structure, the interface bonding is weak, and the fibers are easily peeled off; when potassium hexatite is added only as a single layer without using a bottom + middle layer composite structure, the overall heat insulation and friction stabilization effect is insufficient; deviating from the three-layer gradient ratio range defined in this invention leads to structural imbalance between the friction functional layer and the support layer, resulting in decreased braking stability.

[0193] This invention achieves an environmentally friendly friction material with low thermal fading, low wear, high recovery rate, and stable braking by synergistic combination of graphene cashew nut shell oil modified resin, aramid-epoxy composite layer, potassium hexatitanate layered gradient doping, optimized three-layer structure ratio, and green molding process.

[0194] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A friction material composition, characterized in that, The raw materials of the friction material composition include: friction performance improver, base material and binder; The friction performance improver includes high-hardness ceramic fibers, graphene-modified resin, friction modifier, and filler; The base material includes an aramid fiber and epoxy resin composite layer, potassium hexatitanate, coupling agent and adhesive additive. The adhesive includes nitrile rubber, modified phenolic resin, potassium hexatitanate, coupling agent, talc, and curing accelerator.

2. The composition according to claim 1, characterized in that, In the friction material composition, the friction performance modifier accounts for 40%-50% of the total mass, the base material accounts for 30%-40% of the total mass, and the binder accounts for 10%-20% of the total mass. And / or, the high-hardness ceramic fiber is silicon carbide ceramic fiber; And / or, the graphene-modified resin is a graphene-modified cashew nutshell oil-modified phenolic resin. And / or, the friction modifier is a mixture of graphite and antimony sulfide; the mass ratio of graphite to antimony sulfide is 1:0.8-1.2; And / or, the filler is a mixture of talc and calcium carbonate, preferably in a mass ratio of 1-3:1, more preferably 2:1; And / or, the mass ratio of silicon carbide ceramic fiber to graphene-modified resin is 1:1.2~1.

5.

3. The composition according to claim 1, characterized in that, In the friction performance improver, silicon carbide ceramic fiber accounts for 35%-40% of the total mass, graphene modified resin accounts for 48%-52% of the total mass, friction modifier accounts for 10%-13%, and the remainder is filler. And / or, the mass ratio of the aramid fiber and epoxy resin composite layer to potassium hexatitanate is 1.5~2:1; And / or, the preparation method of the aramid fiber and epoxy resin composite layer is as follows: After plasma surface treatment, aramid fibers are immersed in a mixture of E-51 epoxy resin and curing agent for impregnation, and then pre-cured to form an aramid fiber-epoxy resin composite layer.

4. The composition according to claim 3, characterized in that, The adhesive is cashew nut shell oil modified phenolic resin; And / or, the immersion time is 10-30 min; the immersion temperature is 20-30 ℃; And / or, the pre-curing temperature is 75-85 ℃; the time is 10-20 min; And / or, the mass ratio of aramid fiber to epoxy resin is 1:0.8~1; And / or, the curing agent is an amine curing agent, preferably diethylenetriamine.

5. The composition according to claim 1, characterized in that, In the base material, the aramid fiber and epoxy resin composite layer accounts for 55%-60% of the total mass; potassium hexatitanate accounts for 30%-35% of the total mass; the remainder is coupling agent and talc filler. And / or, the mass ratio of nitrile rubber, modified phenolic resin, and potassium hexatitanate is 1:1.2~1.5:0.5~0.7; And / or, the curing accelerator is an imidazole curing accelerator, specifically 2-ethyl-4-methylimidazolium; the coupling agent is a silane coupling agent KH550; And / or, the modified phenolic resin is a cashew nut shell oil modified phenolic resin, and the preparation method of the modified phenolic resin is as follows: Phenol and formaldehyde are heated, hydrochloric acid is added to react, then cashew nut shell oil is added, and the reaction is continued by heating. After the reaction is completed, the pH is adjusted to 7-8, the mixture is distilled under reduced pressure, and then cooled to obtain the final product. And / or, the preparation method of the graphene-modified resin is as follows: Graphene powder was added to anhydrous ethanol, stirred, then a coupling agent was added, and the mixture was allowed to stand to obtain a graphene dispersion. The cashew nut shell oil-modified phenolic resin is heated to 50-60 ℃, graphene dispersion is added, and the mixture is stirred at a constant temperature. After stirring, vacuum degassing is performed to obtain the final product.

6. A friction plate, characterized in that, The friction plate comprises four parts: a back plate, a bottom layer, a middle layer, and a surface layer. The bottom layer, intermediate layer and top layer are prepared from the adhesive, base material and friction performance improver as described in claim 1; And / or, the surface of the friction pad is provided with asymmetrical spiral grooves; And / or, the asymmetric spiral grooves are conch shell spiral textures, with a width of 0.5-1.2 mm, a depth of 0.3-0.8 mm, and a groove coverage area of ​​15%-25%; And / or, the back plate is made of low-carbon steel plate, which is selected from Q235 and SPCC.

7. The method for preparing the friction pad as described in claim 6, characterized in that, Includes the following steps: (1) Add the coupling agent to the solvent and stir, let stand, and obtain the coupling agent solution; add talc powder to the solvent and stir to make a filler slurry; The modified phenolic resin is heated to 50-60 ℃, nitrile rubber is added, and the mixture is stirred at a constant temperature to obtain a resin-rubber blend system; coupling agent solution, curing accelerator, filler slurry, and potassium hexatitanate are added in sequence, stirred, allowed to stand, defoamed, coated on the backing plate, and dried. (2) Mix high-hardness ceramic fibers, friction modifiers and fillers, and stir; add graphene-modified resin and continue stirring until particles with a particle size of 2-5 mm are formed to obtain a surface friction performance improver. (3) Mix the aramid fiber and epoxy resin composite layer with potassium hexatitanate and coupling agent, and stir; add adhesive additives and continue stirring to form the intermediate layer base material mixture; (4) Perform the following steps in sequence: extrusion, pressing, heat treatment, grinding, and biomimetic groove forming to obtain the final product.

8. The preparation method according to claim 7, characterized in that, In step (1), the coupling agent is a silane coupling agent KH550; And / or, in step (1), the solvent is anhydrous ethanol; And / or, in step (1), the curing accelerator is an imidazole curing accelerator, specifically 2-ethyl-4-methylimidazolium; And / or, in step (1), the coupling agent is added to the solvent and stirred for 20-40 min; the stirring speed is 1400-1600 r / min; and it is allowed to stand for 8-15 min. And / or, in step (1), stir at a constant temperature for 50-70 min; And / or, in step (1), after adding coupling agent solution, curing accelerator, filler slurry and potassium hexatitanate, stir for 40-80 min; let stand for 20-25 h.

9. The preparation method according to claim 7, characterized in that, In step (3), the stirring time is 10-20 min; the rotation speed is 1000-1200 r / min; And / or, in step (3), the adhesive is cashew nut shell oil modified phenolic resin; And / or, in step (3), the stirring time is continued for 10-30 min; And / or, in step (4), the extrusion temperature is 80-95 ℃ and the extrusion speed is 40-50 m / min; And / or, in step (4), the pressing pressure is 20 MPa, the temperature is 180 ± 5 ℃, and the holding time is 6-10 minutes; the number of times of venting is 1-3 times and the venting time is 10-30 s. And / or, in step (4), the heat treatment operation is as follows: first, raise the temperature to 160-180 ℃ for 3-5 h, hold the temperature for 3-5 h, then raise the temperature to 180-190 ℃ for 1-3 h, hold the temperature for 3-5 h, then raise the temperature to 200-210 ℃ for 1-2 h, hold the temperature for 2-4 h, then raise the temperature to 220-240 ℃ for 1-2 h, hold the temperature for 1-3 h.

10. The application of the friction pad as described in claim 6 in a vehicle disc or drum brake.

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