Environment-friendly high-performance copper-free brake pad and processing technology thereof

Abstract

The invention provides an environment-friendly high-performance copper-free brake pad and a machining process of the environment-friendly high-performance copper-free brake pad. The brake pad comprises the following components: 11-18 parts of a composite binder, 20-32 parts of reinforced fibers, 16-30 parts of a friction-increasing lubricant, 27-45 parts of a filler, 9-15 parts of an alginate-butyl rubber-polyamide composite reinforcement, 7-13 parts of polyimide-resin mortar modified graphite and 5-10 parts of a core-shell friction-increasing agent. The composite binder guarantees component bonding and structural integrity, the reinforced fibers improve mechanical strength and resist cracking, the friction-increasing lubricant adjusts the friction coefficient and reduces abrasion, and the filler adjusts the density and assists in friction reduction and heat insulation. The alginate composite reinforcement replaces copper fibers to improve the crack resistance and rust resistance, polyimide modified graphite improves the lubrication durability, the core-shell friction increasing agent stabilizes friction and prevents scratches, and finally copper-free environmental protection and high performance combination are achieved.

Description

Technical Field

[0001] This invention relates to the field of brake pad technology, specifically to an environmentally friendly, high-performance copper-free brake pad and its processing technology. Background Technology

[0002] With the development of the brake pad industry, copper-free (usually requiring copper content <0.5% or completely copper-free) has become a core development trend. At the same time, the market has also put forward high-performance requirements for brake pads, such as friction stability, high wear resistance, low braking noise, low dust and good thermal management.

[0003] In traditional brake pad formulations, copper, with its excellent thermal conductivity, can quickly dissipate heat from the friction interface to prevent thermal degradation. It can also lubricate, regulate the coefficient of friction, and enhance structural strength by forming a transfer film. However, the key challenge in the transition to copper-free brake pads lies in finding a solution that can fully replace the multiple functions of copper mentioned above, while maintaining or even improving the overall performance of the brake pads during the replacement process, and controlling production costs.

[0004] While existing copper-free brake pad formulations attempt to replace copper with materials such as steel fibers and monographite, they have significant technical shortcomings: steel fibers are prone to corrosion, which not only affects the service life of brake pads but may also cause braking noise; monographite is prone to losing lubricating components under high-temperature braking scenarios and has poor compatibility with other components, resulting in insufficient lubrication durability; in addition, the bonding effect between components in some formulations is poor, making it difficult to ensure the overall structural integrity of the brake pad, resulting in insufficient mechanical strength and crack resistance, and making it easy to crack during braking. Ultimately, it is difficult to achieve a synergistic balance between copper-free environmental protection and high performance. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides an environmentally friendly, high-performance copper-free brake pad and its processing technology, so that the brake pad has comprehensive properties such as crack resistance, wear resistance, and rust resistance.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This application discloses an environmentally friendly, high-performance copper-free brake pad. By weight, the brake pad comprises: 11-18 parts of composite binder, 20-32 parts of reinforcing fiber, 16-30 parts of friction-enhancing lubricant, 27-45 parts of filler, 9-15 parts of alginate-butyl rubber-polyamide composite reinforcement, 7-13 parts of polyimide-resin putty modified graphite, and 5-10 parts of core-shell friction enhancer.

[0007] By implementing the above technical solutions, the composite binder ensures effective bonding between the components of the brake pad, guaranteeing the integrity of the overall structure; the reinforcing fibers enhance the mechanical strength and crack resistance of the brake pad, inhibiting the generation and propagation of cracks during braking; the friction-enhancing lubricant can specifically adjust the coefficient of friction while providing lubrication, reducing wear during friction; the filler can adjust the density of the brake pad, assisting in friction reduction and heat insulation; the alginate-butyl rubber-polyamide composite reinforcement can construct an organic-inorganic dual-network reinforcement structure, replacing traditional copper fibers and improving the crack resistance and corrosion resistance of the brake pad; the polyimide-resin putty modified graphite can prevent the loss of lubricating components from graphite at high temperatures, enhance the compatibility of graphite with other components, and improve lubrication durability; the core-shell friction enhancer achieves stable friction enhancement through the core phase component, while the outer structure prevents scratches on the brake disc, ensuring stable friction performance under high-temperature conditions. The synergistic effect of each component achieves a combination of copper-free environmental protection and high performance in brake pads.

[0008] Preferably, based on the total weight parts of the components: the composite adhesive comprises 8-12 parts of butyl rubber modified phenolic resin and 3-6 parts of butyl rubber sealant powder; the reinforcing fiber comprises 3-5 parts of aramid fiber, 7-11 parts of modified ceramic fiber, and 10-16 parts of basalt mineral fiber; the friction-enhancing lubricant comprises 5-9 parts of potassium titanate whiskers, 4-7 parts of antimony sulfide, 3-6 parts of molybdenum disulfide, and 4-8 parts of expanded graphite; and the filler comprises 15-22 parts of barium sulfate, 10-18 parts of barite powder, and 2-5 parts of mica powder.

[0009] By implementing the above technical solutions, butyl rubber modified phenolic resin provides brake pads with high-temperature resistant adhesion and improves toughness; butyl rubber sealant powder fills the pores between components to reduce braking noise and enhance waterproofing; the composite adhesive formed by the two ensures overall structural stability; aramid fiber improves brake pad toughness and inhibits crack propagation; modified ceramic fiber has high-temperature resistance and avoids scratching the brake disc; basalt mineral fiber enhances mechanical strength and has no risk of corrosion; the reinforcing fiber system composed of these three components strengthens the mechanical properties of the brake pads; potassium titanate whiskers stabilize... Antimony sulfide stabilizes the friction coefficient at medium and high temperatures, while molybdenum disulfide provides high-temperature lubrication. Expanded graphite supplements lubrication at high temperatures. The friction-enhancing lubricant formed by these four components can synergistically regulate friction performance and reduce wear. Barium sulfate and barite powder can adjust brake pad density and assist in friction reduction. Mica powder can block heat transfer and absorb braking vibration to achieve heat insulation and noise reduction. The filler system composed of these three components optimizes the brake pad density and heat insulation and noise reduction effects. The combined effect of each component promotes stable bonding, mechanical enhancement, friction regulation, and performance optimization of the brake pads.

[0010] The preferred method for preparing the alginate-butyl rubber-polyamide composite reinforcement is as follows: 1) Weigh out sodium alginate aqueous solution, butyl rubber latex, polyamide short fibers and calcium chloride in a mass ratio of 10:30:5:1; 2) First, add polyamide short fibers to sodium alginate aqueous solution and stir at 300-400 r / min for 20-30 min at 50-55℃. Then add butyl rubber latex and continue stirring at the same temperature and speed for 20-30 min to form a homogeneous latex. 3) Add calcium chloride aqueous solution to the emulsion at a dropping rate of 1-2 mL / min, stir at room temperature for 15-20 min to allow sodium alginate to fully crosslink and form a semi-solid gel. Let the semi-solid gel stand for 30-40 min, then extrude and pelletize it through a twin-screw extruder, and dry it at 60-65℃ for 2-3 h to obtain the alginate-butyl rubber-polyamide composite reinforcement.

[0011] By setting up the above technical solution, the polyamide short fibers are first mixed and stirred with sodium alginate aqueous solution, which can achieve uniform dispersion of polyamide short fibers in sodium alginate system, laying the foundation for the subsequent formation of reinforced structure. Adding butyl rubber emulsion and continuing to stir can fully integrate butyl rubber with sodium alginate aqueous solution and polyamide short fibers to form a homogeneous emulsion, ensuring the uniformity of bonding between components. The addition of calcium chloride can promote the cross-linking of sodium alginate to form a semi-solid gel, giving the system a stable structural morphology. After static aging, extrusion pelletizing and drying, the final composite reinforcement has sodium alginate providing flexibility, butyl rubber providing sealing elasticity, and polyamide short fibers enhancing tensile properties. The synergistic effect of the three makes the composite reinforcement have good reinforcement and crack resistance, which can effectively provide structural support and performance enhancement for brake pads.

[0012] Preferably, the sodium alginate aqueous solution has a mass fraction of 10 wt%, the butyl rubber latex has a solid content of 30%, and the calcium chloride aqueous solution has a mass volume concentration of 3%-5%.

[0013] By setting up the above technical solution, the sodium alginate aqueous solution has suitable solubility and viscosity, providing a stable matrix for the subsequent uniform mixing with polyamide short fibers and butyl rubber latex, facilitating the formation of a homogeneous system; the butyl rubber latex with 30% solid content can fully participate in the fusion process with sodium alginate aqueous solution and polyamide short fibers, ensuring that its sealing elasticity and toughness are effectively reflected in the composite reinforcement; the 3%-5% mass-volume concentration of calcium chloride aqueous solution can effectively promote the sodium alginate to undergo a full and uniform cross-linking reaction, forming a structurally stable semi-solid gel, laying the foundation for the structural integrity and performance stability of the composite reinforcement after subsequent extrusion pelletizing and drying.

[0014] Preferably, the extrusion conditions for the twin-screw extruder are: screw speed 150-200 r / min, die temperature 50-55℃.

[0015] By setting the above technical solution, the screw speed of the twin-screw extruder at 150-200 r / min can form appropriate shear and conveying force on the semi-solid gel raw material of alginate-butyl rubber-polyamide composite reinforcement, ensuring that sodium alginate, butyl rubber, and polyamide short fibers in the semi-solid gel are fully mixed and evenly dispersed, avoiding component agglomeration. The die temperature of 50-55℃ is consistent with the initial raw material mixing temperature, which can prevent butyl rubber from softening and deforming prematurely due to excessive temperature or sodium alginate from having its cross-linked structure destroyed due to temperature fluctuations, ensuring that the extruded particles have regular shape and uniform size, laying the foundation for the structural stability of the composite reinforcement after subsequent drying.

[0016] The preferred method for preparing polyimide-resin putty modified graphite is as follows: a1. Weigh out flake graphite, polyimide resin, resin putty and N,N-dimethylformamide in a mass ratio of 80:10:8:2; a2. Dissolve the polyimide resin and resin putty in N,N-dimethylformamide and stir at 40-45℃ for 15-20 minutes until a uniformly dispersed mixture is formed; a3. Add flake graphite to the mixture, stir at 400-500 r / min for 40-50 min at 50-55℃, then dry under vacuum conditions of 80-85℃ and -0.08 to -0.09 MPa for 3-4 h, and pulverize to 150-200 mesh to obtain polyimide-resin putty modified graphite.

[0017] By implementing the above technical solutions, N,N-dimethylformamide can dissolve polyimide resin and resin putty, providing a solvent base for the formation of a homogeneous mixture. Dissolving the polyimide resin and resin putty in N,N-dimethylformamide and stirring allows for uniform dispersion of the polyimide resin and resin putty, preparing for subsequent bonding with flake graphite. Adding flake graphite to the mixture and stirring allows the polyimide resin and resin putty to be uniformly adsorbed onto the surface of the flake graphite, achieving modification of the flake graphite. Vacuum drying removes N,N-dimethylformamide from the system, preventing solvent residue from affecting performance, while pulverization ensures the modified graphite reaches a suitable particle size for subsequent dispersion. The resulting polyimide-resin putty modified graphite, leveraging the high-temperature stability of the polyimide resin and the interfacial adhesion of the resin putty, enhances the high-temperature lubrication durability of the flake graphite and its compatibility with other components of the brake pad, providing a stable high-temperature lubrication effect for the brake pad.

[0018] The preferred method for preparing the core-shell friction modifier is as follows: b1. Weigh out zircon powder, trimethylaluminum, hexagonal boron nitride and deionized water in a mass ratio of 100:7:12:5; b2. The zircon powder is ball-milled to nanoscale and placed in an atomic layer deposition device under nitrogen protection. The temperature is raised to 200-220℃, and trimethylaluminum and deionized water are added as reaction raw materials. The deposition is repeated 50-60 times to form a nano-alumina intermediate layer with a thickness of 50-80nm. b3. Cool to 180-200℃, introduce a 5wt% hexagonal boron nitride suspension prepared in proportion, and mechanically stir for 30-40 minutes to uniformly coat the boron nitride on the outside of the nano-alumina intermediate layer. After cooling to room temperature, remove the agglomerates by sieving with a 320-340 mesh filter to obtain the core-shell friction modifier.

[0019] By setting up the above technical solution, zircon powder is ball-milled to the nanoscale, providing a suitable core phase basis for the core-shell friction enhancer, which can leverage its hardness advantage to achieve the friction-enhancing effect. During atomic layer deposition, trimethylaluminum serves as the aluminum source, and deionized water participates in the reaction. The nano-alumina intermediate layer formed by the cyclic deposition of the two under nitrogen protection and heating conditions can improve the dispersibility of zircon powder and provide a good bonding interface for subsequent hexagonal boron nitride coating. After cooling, a hexagonal boron nitride suspension is introduced and stirred, so that the hexagonal boron nitride is uniformly coated on the outside of the nano-alumina intermediate layer. The hexagonal boron nitride can act as a buffer to prevent zircon powder from directly contacting and scratching the brake disc. Finally, agglomerates are removed by sieving to ensure that the core-shell friction enhancer has a uniform particle size, which is convenient for subsequent dispersion in brake pad raw materials. The core-shell structure formed by the synergistic effect of each component can prevent damage to the brake disc while achieving the friction-enhancing effect, ensuring the stability of the friction performance of the brake pad.

[0020] Preferably, the operation steps for cyclic deposition are: TMA pulse 0.5s → nitrogen purging 10s → water pulse 0.5s → nitrogen purging 10s.

[0021] By setting up the above technical solution, a 0.5s TMA (trimethylaluminum) pulse allows trimethylaluminum to uniformly adhere to the surface of zircon powder, providing sufficient aluminum source for the formation of the nano-alumina intermediate layer. A subsequent 10s nitrogen purging removes excess unadsorbed trimethylaluminum from the zircon powder surface, preventing residual aluminum from affecting the purity of subsequent reactions. A 0.5s water pulse allows water to fully react with the adsorbed trimethylaluminum, generating nano-alumina. A further 10s nitrogen purging removes byproducts and unreacted excess water, preventing impurities from damaging the intermediate layer structure. The entire cyclic operation, through multiple alternations of "pulse feeding - nitrogen removal," ensures the orderly and uniform reaction of trimethylaluminum and water on the zircon powder surface, thereby forming a uniformly thick and highly pure nano-alumina intermediate layer, laying the foundation for the subsequent uniform coating of hexagonal boron nitride.

[0022] This application also discloses a processing technology for environmentally friendly, high-performance copper-free brake pads, including the following steps: S1. Dry the reinforcing fiber and the alginate-butyl rubber-polyamide composite reinforcement at 50-55℃ for 2-3 hours until the moisture content is ≤0.5%; S2. Add alginate-butyl rubber-polyamide composite reinforcement and reinforcing fibers to a plow-type mixer. Stir at 1000-1100 r / min for 15-20 min at 50-55℃. Then add composite binder and filler. Stir at 1100-1200 r / min for 20-25 min at 50-55℃. Finally, add polyimide-resin putty modified graphite, core-shell friction modifier and friction lubricant. Stir at 1200-1300 r / min for 25-30 min at 50-55℃ to obtain a mixture. S3. Pour the mixture into a cold mold, apply a pressure of 80-120 kgf / cm², hold the pressure for 30-40 seconds, and press it into a cold block. S4. Place the cold block into a hot press mold with multi-stage venting grooves and process it using the "three-stage heating and pressurization + directional venting" process to obtain the hot press molded part. S5. Cool the hot-pressed part to room temperature, place it in a curing oven, and process it using a "multi-stage heating and heat preservation" process to obtain the cured brake pad. S6. Apply butyl rubber waterproof sealant to the non-friction surface of the cured brake pads with a coating thickness of 0.1-0.2mm. Dry at 80-85℃ for 30-40 minutes to form a sealing layer. Finally, grind, code, and inspect the brake pads to obtain the finished product.

[0023] By setting up the above technical solutions, the drying treatment of the reinforcing fiber and the alginate-butyl rubber-polyamide composite reinforcement in S1 can remove excess moisture, avoid the influence of moisture on the bonding effect between subsequent components, and ensure the stability of their performance; the segmented mixing method in S2 first mixes the alginate-butyl rubber-polyamide composite reinforcement with the reinforcing fiber to form a preliminary network, then adds the composite binder and filler, and finally adds polyimide-resin putty modified graphite, core-shell friction modifier, and friction lubricant, which can ensure that all components are uniformly dispersed, avoid stratification due to density differences, and give full play to the function of each component; the cold pressing molding in S3 can fix the shape of the mixture and prevent powder splashing during subsequent hot pressing, thus ensuring the stability of the performance of both components. Hot pressing lays the foundation; the S4 hot pressing process with multi-stage venting grooves can remove low-molecular-weight volatiles from the mixture, avoiding residual air bubbles, making the hot-pressed parts dense and strengthening the bond between the composite binder and other components; the S5 multi-stage curing process can promote the full cross-linking of the composite binder, enhance the interfacial bonding force between reinforcing fibers, alginate-butyl rubber-polyamide composite reinforcement and other components, and improve the structural stability of the brake pads; the S6 sealing layer formed by coating butyl rubber waterproof sealant can prevent moisture and dust from entering, protect the performance of internal components such as polyimide-resin putty modified graphite and core-shell friction modifier, and subsequent grinding and inspection ensure the dimensional accuracy and quality of the finished product.

[0024] The preferred treatment process, which involves "three-stage heating and pressurization + directional exhaust," is as follows: First stage: Temperature 150-155℃, pressure 200-250kgf / cm², pressure holding for 60-80s; directional exhaust 3-4 times, each time for 10-12s, to remove low molecular weight volatiles; Second stage: Heat to 160-165℃, pressurize to 300-350kgf / cm², hold pressure for 100-120s; vent 2-3 times in a directional manner, each time for 8-10s, to promote the melting and bonding of components; The third stage: heat to 165-170℃, pressurize to 350-400 kgf / cm², hold pressure for 200-240 seconds, and complete the hot pressing. The "multi-stage heating and insulation" process is as follows: Room temperature → 80℃: heating time 0.5h, holding time 1h; 80℃→120℃: Heating time 0.5h, holding time 1.5h; 120℃→180℃: Heating time 1 hour, holding time 2 hours; 180℃→230℃: Heating time 1.5h, holding time 3h; Allow to cool naturally from 230℃ to room temperature.

[0025] By setting up the above technical solution, in the "three-stage heating and pressurization + directional degassing" process, the first stage of low temperature and low pressure directional degassing can remove low molecular weight volatiles in the mixture, avoiding residual bubbles that affect the bonding of the composite binder with other components, and ensuring the compactness of the brake pad structure; the second stage of heating and pressurization and directional degassing can promote the melting of the composite binder, allowing it to better coat the reinforcing fibers, alginate-butyl rubber-polyamide composite reinforcement and other components, and strengthen the interfacial bonding force; the third stage of hot pressing at higher temperature and pressure ensures that the polyimide-resin putty modified graphite, core-shell friction modifier and other components are fully integrated into the overall structure, improving the molding quality of the brake pad. The "multi-stage heating and insulation" process allows the composite binder to gradually and fully cross-link through slow heating and segmented insulation, avoiding the generation of internal stress due to excessively rapid heating, enhancing its bonding stability with reinforcing fibers and fillers. Insulation at 230℃ allows the polyimide in the polyimide-resin putty modified graphite to fully cure, and finally, natural cooling prevents the brake pads from cracking due to sudden cooling, ensuring the stable performance of each component and improving the overall structural strength and operational stability of the brake pads.

[0026] The beneficial effects of this invention are as follows: Composite binders ensure effective bonding between brake pad components, guaranteeing overall structural integrity; reinforcing fibers enhance the mechanical strength and crack resistance of brake pads, inhibiting crack generation and propagation during braking; friction-enhancing lubricants specifically adjust the coefficient of friction while providing lubrication, reducing wear during friction; fillers adjust brake pad density, aiding in friction reduction and heat insulation; alginate-butyl rubber-polyamide composite reinforcement constructs an organic-inorganic dual-network reinforcement structure, replacing traditional copper fibers and improving brake pad crack resistance and corrosion resistance; polyimide-resin putty modified graphite prevents the loss of lubricating components at high temperatures, enhances the compatibility of graphite with other components, and improves lubrication durability; core-shell friction enhancers achieve stable friction enhancement through core phase components, while the outer structure prevents scratches on the brake disc, ensuring stable friction performance under high-temperature conditions. The synergistic effect of all components achieves a combination of copper-free environmental protection and high performance in brake pads.

[0027] Polyamide short fibers are first mixed and stirred with sodium alginate aqueous solution to achieve uniform dispersion of polyamide short fibers in the sodium alginate system, laying the foundation for the subsequent formation of a reinforcing structure. Adding butyl rubber emulsion and continuing stirring allows butyl rubber to fully integrate with sodium alginate aqueous solution and polyamide short fibers to form a homogeneous emulsion, ensuring the uniformity of bonding between components. The addition of calcium chloride promotes the cross-linking of sodium alginate to form a semi-solid gel, giving the system a stable structural morphology. After static aging, extrusion pelletizing and drying, the final composite reinforcement contains sodium alginate providing flexibility, butyl rubber providing sealing elasticity, and polyamide short fibers enhancing tensile properties. The synergistic effect of these three components gives the composite reinforcement good reinforcement and crack resistance, effectively providing structural support and performance enhancement for brake pads.

[0028] N,N-Dimethylformamide can dissolve polyimide resin and resin putty, providing a solvent basis for the formation of a homogeneous mixture. Dissolving the polyimide resin and resin putty in N,N-dimethylformamide and stirring allows for uniform dispersion of the polyimide resin and resin putty, preparing them for subsequent bonding with flake graphite. Adding flake graphite to the mixture and stirring allows the polyimide resin and resin putty to be uniformly adsorbed onto the surface of the flake graphite, achieving modification of the flake graphite. Vacuum drying removes N,N-dimethylformamide from the system, preventing solvent residue from affecting performance, while pulverization ensures the modified graphite reaches a suitable particle size for subsequent dispersion. The resulting polyimide-resin putty modified graphite, leveraging the high-temperature stability of the polyimide resin and the interfacial adhesion of the resin putty, improves the high-temperature lubrication durability of the flake graphite and its compatibility with other components of the brake pad, providing a stable high-temperature lubrication effect for the brake pad. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1: This embodiment discloses an environmentally friendly, high-performance copper-free brake pad. By weight, the brake pad comprises: 8 parts butyl rubber modified phenolic resin, 3 parts butyl rubber sealant powder, 3 parts aramid fiber, 7 parts alumina ceramic fiber (modified ceramic fiber), 10 parts basalt mineral fiber, 5 parts potassium titanate whiskers, 4 parts antimony sulfide, 3 parts molybdenum disulfide, 4 parts expanded graphite, 15 parts barium sulfate, 10 parts barite powder, 2 parts mica powder, 9 parts alginate-butyl rubber-polyamide composite reinforcement, 7 parts polyimide-resin putty modified graphite, and 5 parts core-shell friction modifier.

[0031] The preparation method of the alginate-butyl rubber-polyamide composite reinforcement is as follows: 1) Weigh out the following ingredients in a mass ratio of 10:30:5:1: a 10 wt% sodium alginate aqueous solution, a 30% butyl rubber latex, polyamide short fibers, and a 3% calcium chloride solution. 2) First, add polyamide short fibers to sodium alginate aqueous solution and stir at 300 r / min for 20 min at 50℃. Then add butyl rubber latex and continue stirring at the same temperature and speed for 20 min to form a homogeneous latex. 3) Add calcium chloride aqueous solution to the emulsion at a dropping rate of 1 mL / min, stir at room temperature for 15 min to allow sodium alginate to fully crosslink and form a semi-solid gel. Let the semi-solid gel stand for 30 min to age, then extrude and pelletize it in a twin-screw extruder with a screw speed of 150 r / min and a die temperature of 50 °C, and then dry it at 60 °C for 2 h to obtain the alginate-butyl rubber-polyamide composite reinforcement.

[0032] The preparation method of polyimide-resin putty modified graphite is as follows: a1. Weigh out flake graphite, polyimide resin, resin putty and N,N-dimethylformamide in a mass ratio of 80:10:8:2; a2. Dissolve the polyimide resin and resin putty in N,N-dimethylformamide and stir at 40°C for 15 minutes until a uniformly dispersed mixture is formed; a3. Add flake graphite to the mixture, stir at 400 r / min for 40 min at 50℃, then dry under vacuum conditions of 80℃ and -0.08 MPa for 3 h, and pulverize to 150 mesh to obtain polyimide-resin putty modified graphite.

[0033] The preparation method of core-shell friction modifier is as follows: b1. Weigh out zircon powder, trimethylaluminum, hexagonal boron nitride and deionized water in a mass ratio of 100:7:12:5; b2. Zircon powder was ball-milled to nanoscale and placed in an atomic layer deposition device under nitrogen protection. The temperature was raised to 200°C, and trimethylaluminum and deionized water were added as reaction raw materials. The deposition was repeated 50 times to form a 50nm thick nano-alumina intermediate layer. The operation steps for each deposition cycle are as follows: TMA pulse 0.5s → nitrogen purging 10s → water pulse 0.5s → nitrogen purging 10s; b3. Cool to 180℃, introduce a 5wt% hexagonal boron nitride suspension prepared in proportion, and mechanically stir for 30 minutes to uniformly coat the boron nitride on the outside of the nano-alumina intermediate layer. After cooling to room temperature, remove the agglomerates by sieving with a 320-mesh filter to obtain the core-shell friction modifier.

[0034] This embodiment also discloses a processing technology for environmentally friendly, high-performance copper-free brake pads, including the following steps: S1. The reinforcing fiber and the alginate-butyl rubber-polyamide composite reinforcement are dried at 50℃ for 2 hours until the moisture content is ≤0.5%; S2. Add alginate-butyl rubber-polyamide composite reinforcement and reinforcing fibers to the plow-type mixer, stir at 1000 r / min for 15 min at 50℃, then add composite binder and filler, stir at 1100 r / min for 20 min at 50℃, and finally add polyimide-resin putty modified graphite, core-shell friction modifier and friction lubricant, stir at 1200 r / min for 25 min at 50℃ to obtain the mixture; S3. Pour the mixture into a cold mold, apply a pressure of 80 kgf / cm², hold the pressure for 30 seconds, and press it into a cold block. S4. Place the cold block into a hot press mold with multi-stage venting grooves and process it using the "three-stage heating and pressurization + directional venting" process to obtain the hot press molded part. The treatment process of "three-stage heating and pressurization + directional exhaust" is as follows: First stage: Temperature 150℃, pressure 200kgf / cm², pressure held for 60s; directional exhaust 3 times, 10s each time, to remove low molecular weight volatiles; Second stage: Heat to 160℃, pressurize to 300kgf / cm², hold pressure for 100s; vent out the gas twice in a directional manner, 8s each time, to promote the melting and bonding of components; Third stage: Heat to 165℃, pressurize to 350kgf / cm², hold pressure for 200s, and complete hot pressing; S5. Cool the hot-pressed part to room temperature, place it in a curing oven, and process it using a "multi-stage heating and heat preservation" process to obtain the cured brake pad. The "multi-stage heating and insulation" process is as follows: Room temperature → 80℃: heating time 0.5h, holding time 1h; 80℃→120℃: Heating time 0.5h, holding time 1.5h; 120℃→180℃: Heating time 1 hour, holding time 2 hours; 180℃→230℃: Heating time 1.5h, holding time 3h; Allow to cool naturally from 230℃ to room temperature; S6. Apply butyl rubber waterproof sealant to the non-friction surface of the cured brake pads with a coating thickness of 0.1 mm, dry at 80℃ for 30 minutes to form a sealing layer, and finally grind, code, and inspect the brake pads to obtain the finished product.

[0035] Example 2: This embodiment discloses an environmentally friendly, high-performance copper-free brake pad. By weight, the brake pad comprises: 12 parts butyl rubber modified phenolic resin, 6 parts butyl rubber sealant powder, 5 parts aramid fiber, 11 parts alumina ceramic fiber, 16 parts basalt mineral fiber, 9 parts potassium titanate whiskers, 7 parts antimony sulfide, 6 parts molybdenum disulfide, 8 parts expanded graphite, 22 parts barium sulfate, 18 parts barite powder, 5 parts mica powder, 15 parts alginate-butyl rubber-polyamide composite reinforcement, 13 parts polyimide-resin putty modified graphite, and 10 parts core-shell friction modifier.

[0036] The preparation method of the alginate-butyl rubber-polyamide composite reinforcement is as follows: 1) Weigh out the following in a mass ratio of 10:30:5:1: a 10 wt% sodium alginate aqueous solution, a 30% solid content butyl rubber latex, polyamide short fibers, and a 5% mass-volume concentration of calcium chloride. 2) First, add polyamide short fibers to sodium alginate aqueous solution and stir at 400 r / min for 30 min at 55℃. Then add butyl rubber latex and continue stirring at the same temperature and speed for 30 min to form a homogeneous latex. 3) Add calcium chloride aqueous solution to the emulsion at a dropping rate of 2 mL / min, stir at room temperature for 20 min to allow sodium alginate to fully crosslink and form a semi-solid gel. Let the semi-solid gel stand for 30-40 min to age, then extrude and pelletize it in a twin-screw extruder with a screw speed of 200 r / min and a die temperature of 55 ℃, and then dry it at 65 ℃ for 3 h to obtain the alginate-butyl rubber-polyamide composite reinforcement.

[0037] The preparation method of polyimide-resin putty modified graphite is as follows: a1. Weigh out flake graphite, polyimide resin, resin putty and N,N-dimethylformamide in a mass ratio of 80:10:8:2; a2. Dissolve the polyimide resin and resin putty in N,N-dimethylformamide and stir at 45°C for 20 minutes until a uniformly dispersed mixture is formed; a3. Add flake graphite to the mixture, stir at 500 r / min for 50 min at 55℃, then dry under vacuum conditions of 85℃ and -0.09 MPa for 4 h, and pulverize to 200 mesh to obtain polyimide-resin putty modified graphite.

[0038] The preparation method of core-shell friction modifier is as follows: b1. Weigh out zircon powder, trimethylaluminum, hexagonal boron nitride and deionized water in a mass ratio of 100:7:12:5; b2. Zircon powder was ball-milled to nanoscale and placed in an atomic layer deposition device under nitrogen protection. The temperature was raised to 220°C, and trimethylaluminum and deionized water were added as reaction raw materials. The deposition was repeated 60 times to form an 80nm thick nano-alumina intermediate layer. The operation steps for each deposition cycle are as follows: TMA pulse 0.5s → nitrogen purging 10s → water pulse 0.5s → nitrogen purging 10s; b3. Cool to 200℃, introduce a 5wt% hexagonal boron nitride suspension prepared in proportion, and mechanically stir for 40 minutes to uniformly coat the boron nitride on the outside of the nano-alumina intermediate layer. After cooling to room temperature, remove the agglomerates by sieving with a 320-340 mesh filter to obtain the core-shell friction modifier.

[0039] This embodiment also discloses a processing technology for environmentally friendly, high-performance copper-free brake pads, including the following steps: S1. The reinforcing fiber and the alginate-butyl rubber-polyamide composite reinforcement are dried at 55℃ for 3 hours until the moisture content is ≤0.5%; S2. Add alginate-butyl rubber-polyamide composite reinforcement and reinforcing fibers to the plow-type mixer, stir at 1100 r / min for 20 min at 55℃, then add composite binder and filler, stir at 1200 r / min for 25 min at 55℃, and finally add polyimide-resin putty modified graphite, core-shell friction modifier and friction lubricant, stir at 1300 r / min for 30 min at 55℃ to obtain the mixture; S3. Pour the mixture into a cold mold, apply a pressure of 120 kgf / cm², hold the pressure for 40 seconds, and press it into a cold block. S4. Place the cold block into a hot press mold with multi-stage venting grooves and process it using the "three-stage heating and pressurization + directional venting" process to obtain the hot press molded part. The treatment process of "three-stage heating and pressurization + directional exhaust" is as follows: First stage: Temperature 155℃, pressure 250kgf / cm², pressure held for 80s; directional exhaust 4 times, 12s each time, to remove low molecular weight volatiles; Second stage: Heat to 165℃, pressurize to 350kgf / cm², hold pressure for 120s; vent out the gas three times in a directional manner, each time for 10s, to promote the melting and bonding of components; Third stage: Heat to 170℃, pressurize to 400kgf / cm², hold pressure for 240s, and complete hot pressing; S5. Cool the hot-pressed part to room temperature, place it in a curing oven, and process it using a "multi-stage heating and heat preservation" process to obtain the cured brake pad. The "multi-stage heating and insulation" process is as follows: Room temperature → 80℃: heating time 0.5h, holding time 1h; 80℃→120℃: Heating time 0.5h, holding time 1.5h; 120℃→180℃: Heating time 1 hour, holding time 2 hours; 180℃→230℃: Heating time 1.5h, holding time 3h; Allow to cool naturally from 230℃ to room temperature; S6. Apply butyl rubber waterproof sealant to the non-friction surface of the cured brake pads with a coating thickness of 0.2 mm, dry at 85℃ for 40 minutes to form a sealing layer, and finally grind, code, and inspect the brake pads to obtain the finished product.

[0040] Example 3: This embodiment discloses an environmentally friendly, high-performance copper-free brake pad. By weight, the brake pad comprises: 10 parts butyl rubber modified phenolic resin, 4.5 parts butyl rubber sealant powder, 4 parts aramid fiber, 9 parts alumina ceramic fiber, 13 parts basalt mineral fiber, 7 parts potassium titanate whiskers, 5.5 parts antimony sulfide, 4.5 parts molybdenum disulfide, 6 parts expanded graphite, 18.5 parts barium sulfate, 14 parts barite powder, 3.5 parts mica powder, 12 parts alginate-butyl rubber-polyamide composite reinforcement, 10 parts polyimide-resin putty modified graphite, and 7.5 parts core-shell friction modifier.

[0041] The preparation method of the alginate-butyl rubber-polyamide composite reinforcement is as follows: 1) Weigh out the following ingredients in a mass ratio of 10:30:5:1: a 10 wt% sodium alginate aqueous solution, a 30% solid content butyl rubber latex, polyamide short fibers, and a 4% mass-volume concentration of calcium chloride. 2) First, add polyamide short fibers to sodium alginate aqueous solution and stir at 350 r / min for 25 min at 52℃. Then add butyl rubber latex and continue stirring at the same temperature and speed for 25 min to form a homogeneous latex. 3) Add calcium chloride aqueous solution to the emulsion at a dropping rate of 1.5 mL / min and stir at room temperature for 18 min to allow sodium alginate to fully crosslink and form a semi-solid gel. Let the semi-solid gel stand for 35 min to age, and then extrude and pelletize it in a twin-screw extruder with a screw speed of 175 r / min and a die temperature of 52 °C. Then dry it at 62 °C for 2.5 h to obtain the alginate-butyl rubber-polyamide composite reinforcement.

[0042] The preparation method of polyimide-resin putty modified graphite is as follows: a1. Weigh out flake graphite, polyimide resin, resin putty and N,N-dimethylformamide in a mass ratio of 80:10:8:2; a2. Dissolve the polyimide resin and resin putty in N,N-dimethylformamide and stir at 42°C for 17 minutes until a uniformly dispersed mixture is formed; a3. Add flake graphite to the mixture, stir at 450 r / min for 42 min at 52℃, then dry under vacuum conditions of -0.085 MPa at 82℃ for 3.5 h, and pulverize to 150-200 mesh to obtain polyimide-resin putty modified graphite.

[0043] The preparation method of core-shell friction modifier is as follows: b1. Weigh out zircon powder, trimethylaluminum, hexagonal boron nitride and deionized water in a mass ratio of 100:7:12:5; b2. Zircon powder was ball-milled to nanoscale and placed in an atomic layer deposition apparatus under nitrogen protection. The temperature was raised to 210°C, and trimethylaluminum and deionized water were added as reaction raw materials. The deposition was repeated 55 times to form a 65nm thick nano-alumina intermediate layer. The operation steps for each deposition cycle are as follows: TMA pulse 0.5s → nitrogen purging 10s → water pulse 0.5s → nitrogen purging 10s; b3. Cool to 190℃, introduce a 5wt% hexagonal boron nitride suspension prepared in proportion, and mechanically stir for 35 minutes to uniformly coat the boron nitride on the outside of the nano-alumina intermediate layer. After cooling to room temperature, remove the agglomerates by sieving with a 330-mesh filter to obtain the core-shell friction modifier.

[0044] This embodiment also discloses a processing technology for environmentally friendly, high-performance copper-free brake pads, including the following steps: S1. The reinforcing fiber and the alginate-butyl rubber-polyamide composite reinforcement are dried at 52℃ for 2.5h until the moisture content is ≤0.5%; S2. Add alginate-butyl rubber-polyamide composite reinforcement and reinforcing fibers to the plow-type mixer, stir at 1050 r / min for 17 min at 52℃, then add composite binder and filler, stir at 1150 r / min for 22 min at 52℃, and finally add polyimide-resin putty modified graphite, core-shell friction modifier and friction lubricant, stir at 1250 r / min for 27 min at 52℃ to obtain the mixture; S3. Pour the mixture into a cold mold, apply a pressure of 100 kgf / cm², hold the pressure for 35 seconds, and press it into a cold block. S4. Place the cold block into a hot press mold with multi-stage venting grooves and process it using the "three-stage heating and pressurization + directional venting" process to obtain the hot press molded part. The treatment process of "three-stage heating and pressurization + directional exhaust" is as follows: First stage: Temperature 152℃, pressure 225kgf / cm², pressure held for 70s; directional exhaust 3 times, 11s each time, to remove low molecular weight volatiles; Second stage: Heat to 162℃, pressurize to 325kgf / cm², hold pressure for 110s; vent out the gas twice in a directional manner, each time for 9s, to promote the melting and bonding of components; Third stage: Heat to 167℃, pressurize to 375kgf / cm², hold pressure for 220s, and complete hot pressing; S5. Cool the hot-pressed part to room temperature, place it in a curing oven, and process it using a "multi-stage heating and heat preservation" process to obtain the cured brake pad. The "multi-stage heating and insulation" process is as follows: Room temperature → 80℃: heating time 0.5h, holding time 1h; 80℃→120℃: Heating time 0.5h, holding time 1.5h; 120℃→180℃: Heating time 1 hour, holding time 2 hours; 180℃→230℃: Heating time 1.5h, holding time 3h; Allow to cool naturally from 230℃ to room temperature; S6. Apply butyl rubber waterproof sealant to the non-friction surface of the cured brake pads with a coating thickness of 0.15mm, dry at 82℃ for 35 minutes to form a sealing layer, and finally grind, code, and inspect the brake pads to obtain the finished product.

[0045] Comparative Example 1: An environmentally friendly, high-performance copper-free brake pad and its processing technology are disclosed. The only difference between this brake pad and Example 3 is that no alginate-butyl rubber-polyamide composite reinforcement is added.

[0046] Comparative Example 2: An environmentally friendly, high-performance copper-free brake pad and its processing technology are disclosed. The only difference between this brake pad and Example 3 is that polyimide-resin putty modified graphite is not added.

[0047] Comparative Example 3: An environmentally friendly, high-performance copper-free brake pad and its processing technology are disclosed. The only difference between this brake pad and Example 3 is that no core-shell friction enhancer is added.

[0048] Comparative Example 4: An environmentally friendly, high-performance copper-free brake pad and its processing technology are disclosed. The only difference between this brake pad and Example 3 is that the butyl rubber sealant powder is replaced with ordinary rubber powder.

[0049] Comparative Example 5: An environmentally friendly, high-performance copper-free brake pad and its processing technology are disclosed. The only difference between this brake pad and Example 3 is that alumina ceramic fibers are replaced with ordinary ceramic fibers.

[0050] Comparative Example 6: An environmentally friendly, high-performance copper-free brake pad and its processing technology are disclosed. The only difference between this brake pad and Example 3 is that in step S2 of the processing technology, the segmented directional mixing is changed to adding all raw materials at once.

[0051] Comparative Example 7: An environmentally friendly, high-performance copper-free brake pad and its processing technology are disclosed. The only difference between this brake pad and Example 3 is that in step S4 of the processing technology, the gradient hot pressing directional venting is adjusted to ordinary hot pressing (without venting grooves).

[0052] Comparative Example 8: An environmentally friendly, high-performance copper-free brake pad and its processing technology are disclosed. The only difference between this brake pad and Example 3 is that in step S5 of the processing technology, the segmented step curing is changed to one-time curing (room temperature → 230°C, heating for 2 hours).

[0053] Comparative Example 9: An environmentally friendly, high-performance copper-free brake pad and its processing technology are disclosed. The only difference between this brake pad and Example 3 is that butyl rubber waterproof sealant is not used to treat the cured brake pad in the processing technology.

[0054] Comparative Example 10: An environmentally friendly, high-performance copper-free brake pad and its processing technology are disclosed. The only difference between this brake pad and Example 3 is that basalt fiber is replaced with steel fiber.

[0055] Comparative Example 11: An environmentally friendly, high-performance copper-free brake pad and its processing technology are disclosed. The only difference between this brake pad and Example 3 is that antimony sulfide is not added.

[0056] Comparative Example 12: An environmentally friendly, high-performance copper-free brake pad and its processing technology are disclosed. The only difference between this brake pad and Example 3 is that potassium whiskers are not added.

[0057] The brake pads obtained in Examples 1-3 and Comparative Examples 1-12 were subjected to performance tests on their coefficient of friction, wear rate, thermal conductivity, shear strength, noise level, friction coefficient attenuation rate in rainy weather, corrosion rate, and coefficient of thermal expansion. The testing methods are as follows: 1. Coefficient of friction and wear rate According to GB5763-2008 "Automotive Brake Liners", finished brake pads from various embodiments and comparative examples were processed into standard specimens with a diameter of 30 mm and a thickness of 10 mm. A constant-speed friction testing machine was used, with test temperatures set at 25℃ (normal temperature), 300℃ (medium temperature), and 600℃ (high temperature), a rotation speed of 1450 r / min, and a braking pressure of 0.8 MPa. The braking was repeated 10 times at each temperature point, and the friction coefficient for each braking cycle was recorded and averaged. The wear rate (unit: 10) was calculated by weighing (difference in sample mass before and after testing) combined with the number of braking cycles, pressure, and friction radius. -7 cm 3 / N・m).

[0058] 2. Thermal conductivity According to GB / T22310-2008 "Test Method for Thermal Expansion Rate of Automotive Brake Pads", the brake pads were processed into 20mm×20mm×5mm samples. A hot wire thermal conductivity meter was used to measure the temperature change of the sample during the heat conduction process in a constant temperature environment of 400℃. The thermal conductivity (unit: W / (m・K)) was calculated by combining the sample density and specific heat capacity parameters.

[0059] 3. Shear strength According to GB / T22309-2008 "Test Method for Shear Strength of Automotive Brake Pads", finished brake pads (bonding surface area 50mm×50mm) were taken and sheared at a loading rate of 5mm / min using a universal testing machine under normal temperature (25℃) and high temperature (300℃, preheated for 30min) conditions. The maximum load at which the specimen broke was recorded, and the strength value (unit: MPa) was calculated according to "shear strength = maximum load / bonding surface area".

[0060] 4. Noise Level According to SAE J2521 "Automotive Braking Noise Test Method", the brake pads were assembled onto a simulated braking test bench (matched with a standard brake disc), the initial braking speed was set to 60 km / h and the deceleration was 0.8g. A sound level meter was placed 1m away from the friction surface, and the braking was performed 20 times continuously. The noise value of each braking was recorded and the average value was taken (unit: dB(A)).

[0061] 5. Friction coefficient attenuation rate in rainy weather The test was designed according to GB5763-2008: First, the friction coefficient (denoted as μ1) at room temperature (25℃) under dry conditions was tested; the spray device was turned on (spray rate 1.33L / min, water flow is perpendicular to the friction surface), and after spraying for 5 minutes, the friction coefficient at room temperature under wet conditions was measured (denoted as μ2); the attenuation rate was calculated according to "attenuation rate = (μ1-μ2) / μ1×100%".

[0062] 6. Corrosion rate According to GB / T10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test", a sample of the brake pad containing fibers was placed in a neutral salt spray chamber. The salt spray concentration was set to 5% NaCl solution, the temperature to 35℃, and the spray volume to 1.5 mL / (h・80cm²). The test was conducted continuously for 500 hours. After removal, the sample was rinsed with deionized water and dried. The fiber corrosion was observed under a microscope, and the proportion of corroded fibers to the total number of fibers was counted (unit: %).

[0063] 7. Coefficient of thermal expansion According to GB / T22310-2008, brake pads were processed into strip samples of 50mm×5mm×5mm. A thermal expansion apparatus was used to heat the sample from 25℃ to 400℃ (heating rate 5℃ / min), and the length change of the sample at different temperatures was recorded. The thermal expansion coefficient was calculated according to "coefficient of thermal expansion = ΔL / (L0×ΔT)" (ΔL is the length change, L0 is the initial length, and ΔT is the temperature change, unit: μm / ℃).

[0064] The results are shown in Table 1.

[0065] Table 1 Performance parameters of brake pads obtained in Examples 1-3 and Comparative Examples 1-12 Group Coefficient of friction (25℃ / 300℃ / 600℃) <![CDATA[Wear rate (10 - 7 cm 3 / N·m)]]> Thermal conductivity (W / (m・K)) Shear strength (at room temperature / 300℃, MPa) Noise level (dB(A)) Rain-induced attenuation rate (%) Corrosion rate (%) Coefficient of thermal expansion (μm / ℃) Example 1 0.38 / 0.40 / 0.35 0.09 45 4.8 / 2.3 68 10.1 0.25 68 Example 2 0.40 / 0.42 / 0.37 0.08 46 5.0 / 2.5 66 9.8 0.22 66 Example 3 0.42 / 0.44 / 0.39 0.07 48 5.2 / 2.7 63 9.2 0.2 65 Comparative Example 1 0.31 / 0.33 / 0.27 0.35 35 2.9 / 1.5 78 18.0 0.3 85 Comparative Example 2 0.33 / 0.35 / 0.28 0.32 32 3.8 / 2.0 75 16.5 0.25 78 Comparative Example 3 0.29 / 0.31 / 0.25 0.40 40 4.3 / 2.1 73 12.0 0.25 77 Comparative Example 4 0.37 / 0.39 / 0.34 0.15 41 4.5 / 2.2 74 17.0 0.25 74 Comparative Example 5 0.36 / 0.38 / 0.33 0.18 39 4.0 / 1.9 72 11.5 0.25 80 Comparative Example 6 0.36 / 0.37 / 0.32 0.165 41.5 4.1 / 2.05 72 13.0 0.3 77.5 Comparative Example 7 0.34 / 0.36 / 0.31 0.13 38 3.5 / 1.8 71 12.0 0.25 81 Comparative Example 8 0.33 / 0.35 / 0.30 0.14 37 3.6 / 1.7 72 13.5 0.25 78 Comparative Example 9 0.38 / 0.40 / 0.35 0.09 42 4.8 / 2.3 68 16.0 0.8 72 Comparative Example 10 0.41 / 0.43 / 0.38 0.17 46 4.6 / 2.4 74 10.0 3.5 69 Comparative Example 11 0.35 / 0.34 / 0.26 0.22 41 4.4 / 2.2 70 12.5 0.25 76 Comparative Example 12 0.35 / 0.33 / 0.24 0.28 40 4.3 / 2.1 71 13.0 0.25 77 Referring to Table 1, each comparative example is compared with Example 3: In Comparative Example 1, the shear strength at room temperature decreased from 5.2 MPa to 2.9 MPa (a decrease of 44.2%), and the wear rate decreased from 0.07 × 10⁻⁶ MPa. - 7 cm 3 / N・m increased to 0.35×10 -7 cm 3 / N・m (increase of 400%), the coefficient of friction at 600℃ decreased from 0.39 to 0.27 (decrease of 30.8%). The reason is that the alginate-butyl rubber-polyamide composite reinforcement is the core of the "organic-inorganic dual network reinforcement structure". Without it, the fiber system cannot form a continuous load-bearing network. During braking, interlayer delamination is prone to occur, resulting in a decrease in shear strength. At the same time, the lack of flexible support at the friction interface makes cracks easy to propagate and the wear rate to increase sharply. The insufficient stability of the friction layer at high temperature also causes the coefficient of friction to decrease.

[0066] In Comparative Example 2, the thermal conductivity decreased from 48 W / (m·K) to 32 W / (m·K) (a decrease of 33.3%), the coefficient of friction at 600℃ decreased from 0.39 to 0.28 (a decrease of 28.2%), and the wear rate decreased from 0.07 × 10⁻⁶. -7 cm 3 / N・m increased to 0.32×10 -7 cm 3 / N・m (increased by 357%); the reason is that polyimide-resin putty modified graphite has both "high temperature sealing and lubrication" and "high efficiency heat conduction" functions. After the graphite is missing, it is easy to oxidize and lose at 600℃, resulting in decreased lubricity and increased wear rate. At the same time, the broken heat conduction channel prevents the frictional heat from spreading quickly, and local overheating further causes the friction coefficient to decrease.

[0067] In Comparative Example 3, the coefficient of friction at 25℃ decreased from 0.42 to 0.29 (a decrease of 31.0%), and the coefficient of friction at 600℃ decreased from 0.39 to 0.25 (a decrease of 35.9%), while the wear rate decreased from 0.07 × 10⁻⁶. -7 cm 3 / N・m increased to 0.40×10 -7 cm 3 / N・m (increase of 471%); the reason is that the zircon core of the core-shell friction modifier can provide high-temperature hard points to achieve friction enhancement, and the nano-alumina shell can avoid scratching the brake disc. After the loss, the friction interface lacks stable hard point support, resulting in a sharp drop in the coefficient of friction. In addition, unmodified zircon is prone to agglomeration, which will scratch the friction surface when it falls off, ultimately leading to a sharp increase in the wear rate.

[0068] In Comparative Example 4, the noise level increased from 63 dB(A) to 74 dB(A) (an increase of 17.5%), and the friction coefficient attenuation rate in rainy weather increased from 9.2% to 17.0% (an increase of 84.8%). The reason is that butyl rubber sealant powder can fill the internal pores of brake pads to reduce braking vibration and noise. At the same time, its waterproof groups can enhance waterproofness. After being replaced with ordinary rubber powder, the pore filling effect is worse, the braking vibration is aggravated, resulting in increased noise. Moreover, the lack of waterproof performance makes it easy for water to seep in during rainy weather, ultimately causing the friction coefficient attenuation rate to increase.

[0069] In Comparative Example 5, the high-temperature shear strength decreased from 2.7 MPa to 1.9 MPa (a decrease of 29.6%), while the coefficient of thermal expansion increased from 65 μm / ℃ to 80 μm / ℃ (an increase of 23.1%). This is because alumina ceramic fibers have better thermal stability, while ordinary ceramic fibers have insufficient thermal stability and more significant dimensional changes when heated, ultimately leading to an increase in the coefficient of thermal expansion.

[0070] In Comparative Example 6, the coefficient of friction decreased from 0.42 to 0.36 at 25℃ (a decrease of 14.3%), and the wear rate decreased from 0.07 × 10⁻⁶. -7 cm 3 / N・m increased to 0.165×10 -7 cm 3 / N・m (increase of 135.7%), uniformity deviation >8%; the reason is that segmented directional mixing feeds the components in stages according to their morphology, which can avoid the stratification caused by the density difference between the fiber and the powder. However, when mixing at one time, the density difference between the fiber and the powder is large, which easily leads to the phenomenon of "fiber agglomeration and powder sedimentation", resulting in poor uniformity of the mixture. Ultimately, this leads to a decrease in the friction coefficient and an increase in the wear rate, and all performance indicators show significant fluctuations.

[0071] In Comparative Example 7, the room temperature shear strength decreased from 5.2 MPa to 3.5 MPa (a decrease of 32.7%), while the coefficient of thermal expansion increased from 65 μm / ℃ to 81 μm / ℃ (an increase of 24.6%). The reason is that gradient hot pressing can remove low-molecular-weight volatiles from the billet through multi-stage venting channels, avoiding the retention of air bubbles. However, ordinary hot pressing has no venting structure, and air bubbles are easily retained in the billet, resulting in a loose brake pad structure, reduced shear strength, and further aggravated dimensional changes due to the expansion of air bubbles when heated, thus increasing the coefficient of thermal expansion.

[0072] In Comparative Example 8, the room temperature shear strength decreased from 5.2 MPa to 3.6 MPa (a decrease of 30.8%), and the wear rate decreased from 0.07 × 10⁻⁶ MPa. - 7 cm 3 / N・m increased to 0.14×10 -7 cm 3 / N・m (increase of 100%); the reason is that segmented step curing can avoid the internal stress generated during the resin cross-linking process by slowly raising the temperature, and ensure sufficient curing. However, if the temperature is raised too quickly during one-time curing, the resin cross-linking will be uneven, resulting in a decrease in interfacial bonding force and shear strength. At the same time, insufficient curing will result in poor stability of the brake pad structure, ultimately leading to an increase in wear rate.

[0073] In Comparative Example 9, the friction coefficient attenuation rate increased from 9.2% to 16.0% (an increase of 73.9%) in rainy weather, and the corrosion rate increased from 0.2% to 0.8% (an increase of 300%). The reason is that the butyl sealing layer can form a barrier on the non-friction surface of the brake pad to prevent moisture and dust from entering. Without sealing treatment, moisture can easily seep into the brake pad in rainy weather, leading to an increase in the friction coefficient attenuation rate. At the same time, the humid environment will accelerate the micro-corrosion of the fibers, resulting in a significant increase in the corrosion rate.

[0074] In Comparative Example 10, the corrosion rate increased from 0.2% to 3.5% (an increase of 1650%), and the noise level increased from 63 dB(A) to 74 dB(A) (an increase of 17.5%). Steel fibers are prone to electrochemical corrosion (Fe-2e) in salt spray environments. - =Fe 2+ This leads to a significant increase in the corrosion rate. At the same time, the rigidity of steel fibers is higher than that of basalt fibers, resulting in more intense vibrations during braking and ultimately raising the noise level.

[0075] In Comparative Example 11, the coefficient of friction at 300℃ decreased from 0.44 to 0.34 (a decrease of 22.7%), and the coefficient of friction at 600℃ decreased from 0.39 to 0.26 (a decrease of 33.3%), while the wear rate decreased from 0.07 × 10⁻⁶. -7 cm 3 / N・m increased to 0.22×10 -7 cm 3 / N・m (increase of 214%); the reason is that antimony sulfide can form an antimony transfer film at the interface during the friction process, which stabilizes the friction coefficient at medium and high temperatures. Without antimony sulfide, the transfer film cannot be formed, and the friction interface is prone to "adhesion-peeling" phenomenon, resulting in large fluctuations and severe attenuation of the friction coefficient, and at the same time, wear will also be aggravated.

[0076] In Comparative Example 12, the coefficient of friction decreased from 0.39 to 0.24 at 600℃ (a decrease of 38.5%), and the wear rate decreased from 0.07 × 10⁻⁶. - 7 cm 3 / N・m increased to 0.28×10 -7 cm 3 / N・m (increase of 300%); the reason is that potassium titanate whiskers can enhance the high-temperature structural stability of brake pads, inhibit the decay of the friction coefficient and improve wear resistance. Without them, brake pads are prone to softening at high temperatures, the friction layer structure is easily damaged, resulting in a significant decrease in the friction coefficient and a significant reduction in wear resistance.

[0077] In summary, the materials in this solution, such as alginate-butyl rubber-polyamide composite reinforcement, polyimide-resin putty modified graphite, and core-shell friction modifier, along with the segmented directional mixing and gradient hot pressing processes, the butyl sealing layer (cured from butyl rubber waterproof sealant), and basalt fiber, all suffer from significant degradation in key properties of the brake pads, such as shear strength and coefficient of friction, if any component is missing or replaced. Only through the synergistic effect of the components in this application can a brake pad with excellent overall performance be obtained.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An environmentally friendly high-performance copper-free brake pad, characterized in that, The brake pad comprises, in parts by weight: a composite binder 11-18, reinforcing fibers 20-32, a friction-enhancing lubricant 16-30, a filler 27-45, a alginate-butyl rubber-polyamide composite reinforcing body 9-15, a polyimide-resin mastic modified graphite 7-13, and a core-shell friction enhancer 5-10.

2. The environmentally friendly high-performance copper-free brake pad of claim 1, wherein, The total components are in parts by weight: The composite binder comprises, in parts by weight: butyl rubber modified phenolic resin 8-12, butyl rubber sealant powder 3-6; The reinforcing fibers comprise, in parts by weight: aramid fiber 3-5, modified ceramic fiber 7-11, basalt mineral fiber 10-16; The friction-enhancing lubricant comprises, in parts by weight: potassium titanate whisker 5-9, antimony sulfide 4-7, molybdenum disulfide 3-6, expanded graphite 4-8; The filler comprises, in parts by weight: barium sulfate 15-22, barite powder 10-18, mica powder 2-5.

3. The environmentally friendly high performance copper-free brake pad of claim 1, wherein, The alginate-butyl rubber-polyamide composite reinforcing body is prepared as follows: 1) Take sodium alginate aqueous solution, butyl rubber emulsion, polyamide short fiber and calcium chloride according to a mass ratio of 10:30:5:1; 2) First, add the polyamide short fiber into the sodium alginate aqueous solution, stir at 300-400 r / min for 20-30 min at 50-55℃, then add the butyl rubber emulsion, continue to stir at the same temperature and speed for 20-30 min to form a uniform emulsion; 3) Add the calcium chloride aqueous solution to the emulsion at a drop rate of 1-2 mL / min, stir at room temperature for 15-20 min to allow the sodium alginate to crosslink fully to form a semi-solid gel, let the semi-solid gel stand for 30-40 min, then extrude and granulate through a twin-screw extruder, and dry at 60-65℃ for 2-3 h to obtain the alginate-butyl rubber-polyamide composite reinforcing body.

4. The environmentally friendly high performance copper-free brake pad of claim 3, wherein, The mass fraction of the sodium alginate aqueous solution is 10 wt%, the solid content of the butyl rubber emulsion is 30%, and the mass-volume concentration of the calcium chloride aqueous solution is 3%-5%.

5. The environmentally friendly high performance copper-free brake pad of claim 3, wherein, The extrusion conditions of the twin-screw extruder are as follows: screw speed 150-200 r / min, die temperature 50-55℃.

6. The environmentally friendly high performance copper-free brake pad as claimed in claim 1, wherein, The polyimide-resin mastic modified graphite is prepared as follows: a1. Take flake graphite, polyimide resin, resin mastic and N,N-dimethylformamide according to a mass ratio of 80:10:8:2; a2. Dissolve the polyimide resin and the resin mastic in the N,N-dimethylformamide, stir at 40-45℃ for 15-20 min to form a uniformly dispersed mixture; a3. Add the flake graphite to the mixture, stir at 400-500 r / min for 40-50 min at 50-55℃, then dry at 80-85℃ under vacuum conditions of -0.08 to -0.09 MPa for 3-4 h, and crush to 150-200 mesh to obtain the polyimide-resin mastic modified graphite.

7. The environmentally friendly, high-performance copper-free brake pad according to claim 1, characterized in that, The core-shell friction enhancer is prepared as follows: b1. Take zircon powder, trimethylaluminum, hexagonal boron nitride and deionized water according to a mass ratio of 100:7:12:5; b2. Zircon powder is ball milled to nanoscale, and is placed in an atomic layer deposition device under nitrogen protection, heated to 200-220 DEG C, and then trimethylaluminum and deionized water are added as reaction raw materials, and the deposition is recycled for 50-60 times to form a 50-80 nm thick nanometer aluminum oxide intermediate layer; b3. The temperature is lowered to 180-200 DEG C, and a proportionally prepared 5 wt% hexagonal boron nitride suspension is introduced, and mechanical stirring is performed for 30-40 min to uniformly coat the boron nitride on the nanometer aluminum oxide intermediate layer, and after cooling to room temperature, agglomerates are removed by screening with a 320-340 mesh screen to obtain the core-shell friction modifier.

8. The environmentally friendly high performance copper-free brake pad of claim 7, wherein, The operation steps of the cyclic deposition are as follows: TMA pulse 0.5 s→ nitrogen blowing 10 s→ water pulse 0.5 s→ nitrogen blowing 10 s.

9. A processing method of the environment-friendly high-performance copper-free brake pad according to any one of claims 1-8, characterized in that, The method comprises the following steps: S1. The reinforcing fibers and the alginate-butyl rubber-polyamide composite reinforcing body are dried at 50-55 DEG C for 2-3 h until the water content is less than or equal to 0.5%; S2. The alginate-butyl rubber-polyamide composite reinforcing body and the reinforcing fibers are added to a plowshare mixer, and after stirring at 50-55 DEG C at 1000-1100 r / min for 15-20 min, the composite binder and the filler are added, and after stirring at 50-55 DEG C at 1100-1200 r / min for 20-25 min, the polyimide-resin mortar modified graphite, the core-shell friction modifier, and the friction-reducing lubricant are added, and after stirring at 50-55 DEG C at 1200-1300 r / min for 25-30 min, the mixture is obtained; S3. The mixture is poured into a cold mold, and a pressure of 80-120 kgf / cm² is applied, and the pressure is maintained for 30-40 s to press the mixture into a cold block; S4. The cold block is placed in a hot press mold with multiple exhaust grooves, and a "three-stage temperature and pressure increasing + directional exhaust" process is used to process the hot press formed part; S5. The hot press formed part is cooled to room temperature, placed in a curing oven, and subjected to a "multi-stage temperature and holding" process to obtain the cured brake pad; S6. The non-friction surface of the cured brake pad is coated with a butyl rubber waterproof sealant, and the coating thickness is 0.1-0.2 mm, and the coated brake pad is dried at 80-85 DEG C for 30-40 min to form a sealing layer, and finally the brake pad is polished, coded, and detected to obtain the finished product.

10. The processing method of the environmentally friendly high-performance copper-free brake pad according to claim 9, wherein the "three-stage temperature and pressure increasing + directional exhaust" process is as follows: The "three-stage temperature and pressure increasing + directional exhaust" process is as follows: First stage: temperature 150-155 DEG C, pressure 200-250 kgf / cm², pressure maintaining time 60-80 s; directional exhaust 3-4 times, each time 10-12 s, to remove low molecular volatile substances; Second stage: temperature increased to 160-165 DEG C, pressure increased to 300-350 kgf / cm², pressure maintaining time 100-120 s; directional exhaust 2-3 times, each time 8-10 s, to promote the fusion and combination of components; Third stage: temperature increased to 165-170 DEG C, pressure increased to 350-400 kgf / cm², pressure maintaining time 200-240 s, to complete the hot pressing; The "multi-stage temperature and holding" process is as follows: Room temperature→80°C: 0.5h for temperature increase, 1h for temperature maintenance; 80°C→120°C: 0.5h for temperature increase, 1.5h for temperature maintenance; 120°C→180°C: 1h for temperature increase, 2h for temperature maintenance; 180°C→230°C: 1.5h for temperature increase, 3h for temperature maintenance; 230°C natural cooling to room temperature.