Caragana microphylla fiber reinforced light copper-free brake friction material and operation method thereof
By replacing copper and glass fibers with citronella fibers, and combining alkali treatment and silane coupling agent treatment, a lightweight, copper-free braking friction material was prepared, solving the problems of environmental pollution and performance instability, and achieving lightweighting and stable friction performance under high temperature and high pressure.
Patent Information
- Application Number
- CN202511883929.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-15
- Publication Date
- 2026-04-14
AI Technical Summary
The use of copper fibers in existing braking friction materials leads to environmental pollution. Furthermore, copper fibers have low mechanical strength and weak bonding with the resin matrix during braking, and their friction coefficient is unstable under high temperature and high pressure, making it difficult to achieve lightweighting and performance optimization.
By replacing copper and glass fibers with citronella fibers, and improving fiber strength and bonding force through alkali treatment and silane coupling agent treatment, pre-formed particles are prepared by combining phenolic resin, sepiolite fiber, composite mineral fiber and other components, and then hot-pressed to form a lightweight copper-free braking friction material.
The density of the friction material was reduced, which improved the lightweight effect of automotive parts. The mechanical strength and interfacial bonding of the material were improved through fiber surface treatment technology, which stabilized the friction performance under high temperature and high pressure.
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Figure CN121851604A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of brake friction materials, and in particular to a lightweight, copper-free brake friction material reinforced with styrax fiber and its operating method. Background Technology
[0002] Braking friction materials are core safety components of braking systems in transportation equipment such as automobiles and rail trains, and their performance directly affects the safe, stable, and efficient operation of the equipment. With the global automotive industry moving towards environmental friendliness and lightweight design, and with increasingly stringent regulations restricting particulate pollution generated during braking, the development of lightweight, high-performance, and environmentally friendly braking friction materials has become an urgent industry need.
[0003] Currently, commercially available semi-metallic braking friction materials typically incorporate 10%–20% copper to improve thermal conductivity, reduce friction coefficient decay, and enhance wear resistance. However, during braking, copper is released into the environment as particulate matter, causing heavy metal pollution to soil and water bodies.
[0004] In the research of copper-free braking friction materials, various reinforcing fibers, such as steel fibers, mineral fibers, and aramid fibers, have been incorporated to compensate for the performance degradation caused by the lack of copper components. However, the introduction of these fibers all has significant limitations. Steel fibers, due to their high density, are not conducive to lightweighting and are prone to scratching the brake disc during braking; aramid fibers are expensive and prone to thermal decomposition under high-temperature conditions during braking, reducing the overall performance of the material; some mineral fibers are also unsuitable for use in friction materials due to potential biosafety risks. Therefore, exploring novel reinforcing fibers that are widely available, low-cost, high-performance, and environmentally friendly is of paramount importance for promoting the development of copper-free braking friction materials.
[0005] Caragana korshinskii, a drought-tolerant and barren-tolerant psammophytic shrub, is widely distributed in Northwest my country. Its branches, produced through coppicing and rejuvenation, are a rich biomass resource. Caragana korshinskii stems are rich in high-strength cellulose fibers, possessing excellent properties such as low density, biodegradability, and renewability, making it a highly promising environmentally friendly reinforcing material. However, the application of Caragana korshinskii fibers in braking friction materials, particularly as a substitute for copper components to construct composite material systems with excellent tribological properties, low environmental impact, and lightweight characteristics, is currently a technological gap. Existing technologies have not yet solved technical challenges such as the low mechanical strength of Caragana korshinskii fibers, weak interfacial bonding with the resin matrix, and the stability of the friction coefficient under high-temperature and high-pressure braking conditions. Summary of the Invention
[0006] The purpose of this invention is to provide a lightweight, copper-free braking friction material reinforced with sage fiber and its operation method, in order to solve the shortcomings of existing resin-based braking friction materials, such as high production cost, high environmental impact, and poor lightweighting effect, as well as the problems of low mechanical strength of sage fiber, weak interfacial bonding with the resin matrix, and instability of friction coefficient under high temperature and high pressure braking conditions.
[0007] To achieve the above objectives, the present invention provides the following technical solution: a lightweight, copper-free braking friction material reinforced with tamarisk fiber, which comprises a resin matrix, reinforcing fibers, fillers, friction modifiers, and processing aids, and contains the following components by mass percentage:
[0008] The resin matrix is phenolic resin accounting for 5%-13% of the total mass;
[0009] The reinforcing fibers include 2%–10% of Caragana korshinskii fiber, 1%–9% of sepiolite fiber and 16%–24% of composite mineral fiber by weight.
[0010] The filler comprises 9%–17% calcium carbonate, 1%–9% vermiculite powder, and 14%–22% precipitated barium sulfate by total mass.
[0011] The friction performance modifier comprises 4%–12% flake graphite, 3%–11% petroleum coke, 2%–10% alumina, 1%–3% friction powder, and 0.3%–1.7% zinc stearate by weight.
[0012] The process aids include low molecular weight acrylic resin and anhydrous ethanol, and the amount of low molecular weight acrylic resin added is 0.5% to 1.5% of the total mass of the above resin matrix, reinforcing fibers, fillers, and friction modifiers;
[0013] The Caragana korshinskii fiber is treated with alkali and silane coupling agent to replace copper fiber and glass fiber. The Caragana korshinskii fiber is mixed with resin matrix, sepiolite fiber, composite mineral fiber, filler and friction modifier to prepare pre-particles. The pre-particles use anhydrous ethanol as the connecting liquid and low molecular weight acrylic resin as the binder.
[0014] Preferably, the styrax fiber is used to replace copper fiber and glass fiber, reducing the density of the friction material by 6%-12% to improve the lightweighting of automotive parts, and has a diameter of 0.02-0.03 mm and a length of 0.5-2 mm.
[0015] Preferably, the alkali treatment includes the following steps:
[0016] Step 1: Use a 4%–10% sodium hydroxide solution to treat the Caragana korshinskii fiber at 40–60°C for 360–500 minutes.
[0017] Step 2: After treatment, rinse the Caragana fibers in distilled water until the solution pH is 7.
[0018] Step 3: After rinsing, air dry the lemon fiber and then place it in an oven at 90℃ for 24 hours.
[0019] Preferably, the silane coupling agent treatment process includes:
[0020] Alkali-treated Caragana korshinskii fibers were placed in an aminosilane coupling agent solution for treatment. The solution was prepared by mass fraction as follows: 4%–12% distilled water, 68%–76% anhydrous ethanol, and 16%–24% silane coupling agent. The amount of silane coupling agent added was 3%–7% of the mass of the Caragana korshinskii fibers. The treatment time was 60–100 minutes. After treatment, the Caragana korshinskii fibers were washed with distilled water and then placed in an oven to dry at 90°C for 24 hours.
[0021] A method for preparing a lightweight, copper-free braking friction material reinforced with *Caragana korshinskii* fiber, the preparation process including:
[0022] Step (1) Pretreatment of Caragana korshinskii fibers:
[0023] 1) The obtained Caragana fibers are hammered, rubbed and washed to remove the wood and bark. The Caragana fibers are placed in a 4%-10% sodium hydroxide solution and treated at 40-60℃ for 360-500 minutes. They are then washed with distilled water until the solution pH is 7 and dried in an oven at 90℃ for 24 hours.
[0024] 2) After drying, the Caragana spp. fibers are placed in an aminosilane coupling agent solution for 60-100 minutes. After the treatment, the Caragana spp. fibers are washed with distilled water and then placed in an oven to dry at 90°C for 24 hours.
[0025] Step (2) Step mixing:
[0026] 1) Put the pretreated Caragana korshinskii fiber and other reinforcing fibers into a mixer for mixing. The mixing speed is 1300-1500 rpm and the mixing time is 5-15 minutes.
[0027] 2) Add phenolic resin, friction modifier, filler and low molecular weight acrylic resin binder with a mass fraction of 0.5%-1.5% to the above mixture and continue mixing. The stirring speed is 2700-3000 rpm and the mixing time is 10-20 minutes.
[0028] Step (3) Preparation of pre-formed granules:
[0029] The mixture from step (2) is added to a granulator for granulation. Anhydrous ethanol is slowly sprayed in during the granulation process. The entire granulation process is divided into three stages, specifically including:
[0030] The first stage is the nucleation stage, which adopts a low-speed mode with a stirrer speed of 300-400 rpm and a drum speed of 50-70 rpm, lasting for 5-8 minutes.
[0031] The second stage is the particle growth stage, which adopts a medium-speed mode with a stirring blade speed of 300-400 rpm and a drum speed of 110-130 rpm, lasting for 20-30 minutes.
[0032] The third stage is the particle compaction stage, which adopts high-speed mode with a stirring blade speed of 700-800 rpm and a drum speed of 110-130 rpm, lasting for 10-20 minutes.
[0033] Secondly, after granulation, the pre-formed particles are dried at a temperature of 80°C for 24 hours. The pre-formed particles are then sieved using a sieve to obtain particles of different diameter ranges for the next step of preparation.
[0034] Step (4) Hot pressing:
[0035] The pre-formed granules of a specified quality are placed into a mold for pressing. The pressing temperature is 150-190℃ and the pressing pressure is 10-12MPa. During the pressing process, multiple venting operations are set, with each venting time being 5-8 seconds. The first and second holding times are 3-5 seconds, the third, fourth, and fifth holding times are 5-15 seconds, and the sixth holding time is 800-1000 seconds.
[0036] Step (5) Heat treatment:
[0037] The pressed sample is placed in a heat treatment chamber for heat treatment to eliminate residual stress and defects inside the material.
[0038] Preferably, the preformed particles are prepared using anhydrous ethanol as a forsythia extract and acrylic resin as a binder.
[0039] Preferably, the pre-particle preparation process in step (3) is divided into three stages, specifically including:
[0040] The first stage is the nucleation stage, which adopts a low-speed mode with a stirrer speed of 300-400 rpm and a drum speed of 50-70 rpm, lasting for 5-8 minutes.
[0041] The second stage is the particle growth stage, which adopts a medium-speed mode with a stirring blade speed of 300-400 rpm and a drum speed of 110-130 rpm, lasting for 20-30 minutes.
[0042] The third stage is the particle compaction stage, which adopts a high-speed mode with a stirring blade speed of 700-800 rpm and a drum speed of 110-130 rpm, lasting for 10-20 minutes.
[0043] Compared with the prior art, the beneficial effects of the present invention are:
[0044] 1. Replacing copper and glass fibers in resin-based brake friction materials with Caragana korshinskii fibers can not only prevent copper shavings generated during braking from harming the aquatic ecosystem, but also increase the added value of agricultural waste Caragana korshinskii, further promote the lightweighting of friction materials, reduce the density of friction materials, and improve the lightweighting effect of automotive parts.
[0045] 2. Based on fiber surface treatment technology, the mechanical strength of Caragana korshinskii fiber and its interfacial bonding with the resin matrix are enhanced through alkali treatment and coupling agent treatment, thereby giving full play to its reinforcing potential. Specifically, alkali treatment removes pectin, waxes, lignin, hemicellulose and other substances from the surface of Caragana korshinskii fiber, thereby improving the mechanical properties of the fiber. Coupling agent treatment increases its interfacial adhesion with the resin matrix and improves its dispersibility in the resin matrix. Attached Figure Description
[0046] Appendix Figure 1 A model diagram of a resin-based friction material reinforced with Caragana korshinskii fiber;
[0047] Appendix Figure 2 Flowchart of the preparation process for resin-based braking friction material reinforced with Caragana korshinskii fiber. Detailed Implementation
[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and 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.
[0049] Please see Figure 1 —2. This invention provides a technical solution: a lightweight, copper-free braking friction material reinforced with sage fiber, which is composed of a resin matrix, reinforcing fibers, fillers, friction performance modifiers, and processing aids, and contains the following components by mass percentage:
[0050] The resin matrix is phenolic resin, accounting for 5%–13% of the total mass;
[0051] The reinforcing fibers include 2%–10% of Caragana korshinskii fiber, 1%–9% of Sepiolite fiber, and 16%–24% of composite mineral fiber by weight.
[0052] The filler comprises 9%–17% calcium carbonate, 1%–9% vermiculite powder, and 14%–22% precipitated barium sulfate by mass.
[0053] The friction performance modifier consists of 4%–12% flake graphite, 3%–11% petroleum coke, 2%–10% alumina, 1%–3% friction powder, and 0.3%–1.7% zinc stearate by mass.
[0054] Processing aids include low molecular weight acrylic resin and anhydrous ethanol. The amount of low molecular weight acrylic resin added is 0.5%–1.5% of the total mass of the above-mentioned resin matrix, reinforcing fibers, fillers, and friction modifiers.
[0055] Among them, the Caragana korshinskii fiber is treated with alkali and silane coupling agent to replace copper fiber and glass fiber. The Caragana korshinskii fiber is mixed with resin matrix, sepiolite fiber, composite mineral fiber, filler and friction performance modifier to prepare pre-granules through pre-granulation technology. Anhydrous ethanol is used as the connecting liquid and low molecular weight acrylic resin is used as the binder for the pre-granules.
[0056] Furthermore, styrax fiber is used to replace copper fiber and glass fiber, reducing the density of friction materials by 6%–12%, thereby improving the lightweighting of automotive parts. It has a diameter of 0.02–0.03 mm and a length of 0.5–2 mm.
[0057] Furthermore, the alkali treatment includes the following steps:
[0058] Step 1: Use a 4%–10% sodium hydroxide solution to treat the Caragana korshinskii fiber at 40–60°C for 360–500 minutes.
[0059] Step 2: After treatment, rinse the Caragana fibers in distilled water until the solution pH is 7.
[0060] Step 3: After rinsing, air dry the lemon fiber and then place it in an oven at 90℃ for 24 hours.
[0061] Furthermore, the silane coupling agent treatment process includes:
[0062] Alkali-treated Caragana korshinskii fibers were placed in an aminosilane coupling agent solution for treatment. The solution was prepared by mass fraction as follows: 4%–12% distilled water, 68%–76% anhydrous ethanol, and 16%–24% silane coupling agent. The amount of silane coupling agent added was 3%–7% of the mass of the Caragana korshinskii fibers. The treatment time was 60–100 minutes. After treatment, the Caragana korshinskii fibers were washed with distilled water and then placed in an oven to dry at 90°C for 24 hours.
[0063] A method for preparing a lightweight, copper-free braking friction material reinforced with *Caragana korshinskii* fiber, the preparation process including:
[0064] Step (1) Pretreatment of Caragana korshinskii fibers:
[0065] 1) The obtained Caragana fibers are hammered, rubbed and washed to remove the wood and bark. The Caragana fibers are placed in a 4%-10% sodium hydroxide solution and treated at 40-60℃ for 360-500 minutes. They are then washed with distilled water until the solution pH is 7 and dried in an oven at 90℃ for 24 hours.
[0066] 2) After drying, the Caragana spp. fibers are placed in an aminosilane coupling agent solution for 60-100 minutes. After the treatment, the Caragana spp. fibers are washed with distilled water and then placed in an oven to dry at 90°C for 24 hours.
[0067] Step (2) Step mixing:
[0068] 1) Put the pretreated Caragana korshinskii fiber and other reinforcing fibers into a mixer for mixing. The mixing speed is 1300-1500 rpm and the mixing time is 5-15 minutes.
[0069] 2) Add phenolic resin, friction modifier, filler, and 0.5%–1.5% (by mass) of low molecular weight acrylic resin binder to the above mixture and continue mixing. The agitator speed is 2700–3000 rpm, and the mixing time is 10–20 minutes.
[0070] Step (3) Preparation of pre-formed granules:
[0071] The mixture from step (2) is added to a granulator for granulation. Anhydrous ethanol is slowly sprayed in during the granulation process. The entire granulation process is divided into three stages, specifically including:
[0072] The first stage is the nucleation stage, which adopts a low-speed mode with a stirrer speed of 300-400 rpm and a drum speed of 50-70 rpm, lasting for 5-8 minutes.
[0073] The second stage is the particle growth stage, which adopts a medium-speed mode with a stirring blade speed of 300-400 rpm and a drum speed of 110-130 rpm, lasting for 20-30 minutes.
[0074] The third stage is the particle compaction stage, which adopts high-speed mode with a stirring blade speed of 700-800 rpm and a drum speed of 110-130 rpm, lasting for 10-20 minutes.
[0075] Secondly, after granulation, the pre-formed particles are dried at a temperature of 80°C for 24 hours. The pre-formed particles are then sieved using a sieve to obtain particles of different diameter ranges for the next step of preparation.
[0076] Step (4) Hot pressing:
[0077] The pre-formed granules of a specified quality are placed into a mold for pressing. The pressing temperature is 150-190℃ and the pressing pressure is 10-12MPa. During the pressing process, multiple venting operations are set, with each venting time being 5-8 seconds. The first and second holding times are 3-5 seconds, the third, fourth, and fifth holding times are 5-15 seconds, and the sixth holding time is 800-1000 seconds.
[0078] Step (5) Heat treatment:
[0079] The pressed sample is placed in a heat treatment chamber for heat treatment to eliminate residual stress and defects inside the material.
[0080] Furthermore, the preformed particles are prepared using anhydrous ethanol as a forsythia extract and acrylic resin as a binder.
[0081] Furthermore, the pre-particle preparation process in step (3) is divided into three stages, specifically including:
[0082] The first stage is the nucleation stage, which adopts a low-speed mode with a stirrer speed of 300-400 rpm and a drum speed of 50-70 rpm, lasting for 5-8 minutes.
[0083] The second stage is the particle growth stage, which adopts a medium-speed mode with a stirring blade speed of 300-400 rpm and a drum speed of 110-130 rpm, lasting for 20-30 minutes.
[0084] The third stage is the particle compaction stage, which adopts a high-speed mode with a stirring blade speed of 700-800 rpm and a drum speed of 110-130 rpm, lasting for 10-20 minutes.
[0085] Example 1
[0086] A lightweight, copper-free braking friction material reinforced with Caragana korshinskii fiber and its preparation method are disclosed. The material is prepared using pre-formed particles of 1-3 mm in size. The Caragana korshinskii fiber accounts for 7% by mass. The contents of the remaining components are as follows: phenolic resin 7%, sepiolite fiber 7%, composite mineral fiber 20%, calcium carbonate 13%, vermiculite powder 5%, precipitated barium sulfate 19%, flake graphite 8%, petroleum coke 7%, alumina 6%, friction powder 2%, and zinc stearate 1%.
[0087] Lightweight, copper-free brake friction material reinforced with citronella fiber is prepared through the following steps:
[0088] (1) The Fiber of Caragana korshinskii was treated with alkali and silane coupling agent. The Fiber was treated with a 7% sodium hydroxide solution at 50°C for 420 minutes. After washing with distilled water until the pH value was 7, the Fiber was treated with silane coupling agent again. The Silane coupling agent solution was prepared in the following mass ratio: Silane coupling agent: Distilled water: Anhydrous ethanol = 8:72:20, and the treatment time was 80 minutes.
[0089] (2) The components are mixed in a stepwise mixing manner. First, the Caragana korshinskii fiber, sepiolite fiber and composite mineral fiber are added to the mixer and mixed for 10 minutes at a speed of 1400 rpm. Then, phenolic resin, friction modifier, filler and 1% of the total mass of low molecular weight acrylic resin binder are added to the above mixture and mixed for another 20 minutes at a speed of 2800 rpm. The mixing process is carried out in an intermittent manner to prevent the high temperature of friction during the mixing process from damaging the structure of each component. The mixing is paused for 10 seconds after 30 seconds.
[0090] (3) The mixture of the above components is added to a granulator to prepare pre-granules. During the stirring process, anhydrous ethanol is slowly sprayed into the bridging liquid. The entire granulation process includes three stages. The first stage is the nucleation stage, with a granulation time of 6 minutes, a stirring speed of 350 rpm, and a drum speed of 60 rpm. The second stage is the particle growth stage, with a granulation time of 25 minutes, a stirring speed of 350 rpm, and a drum speed of 120 rpm. The third stage is the particle densification stage, with a granulation time of 15 minutes, a stirring speed of 750 rpm, and a drum speed of 120 rpm. After granulation, the pre-granules are dried at a temperature of 80°C for 24 hours. The pre-granules are then sieved using a sieve, and particles with a diameter in the range of 1-3 mm are pressed.
[0091] (4) Hot pressing: Weigh the specified mass of pre-made particles and put them into the mold for pressing. The pressing temperature is 160℃ and the pressing pressure is 11MPa. During the pressing process, multiple venting is set, and the venting time is 6 seconds each time. Among them, the first and second holding time is 5 seconds, the third, fourth and fifth holding time is 10 seconds, and the sixth holding time is 1000 seconds.
[0092] (5) Heat treatment: The pressed sample is placed in a heat treatment chamber for heat treatment to remove residual stress and internal defects in the material. The heat treatment time is 18 hours.
[0093] Example 2
[0094] A lightweight, copper-free braking friction material reinforced with Caragana korshinskii fiber and its preparation method are described. The material is prepared using 3-5mm pre-formed particles, wherein the added Caragana korshinskii fiber accounts for 8% by mass; the contents of the remaining components are as follows: phenolic resin 9%, sepiolite fiber 6%, composite mineral fiber 19%, calcium carbonate 12%, vermiculite powder 6%, precipitated barium sulfate 16%, flake graphite 6%, petroleum coke 8%, alumina 7%, friction powder 2%, and zinc stearate 1%.
[0095] Lightweight, copper-free brake friction material reinforced with citronella fiber is prepared through the following steps:
[0096] (1) The Fiber of Caragana korshinskii was treated with alkali and silane coupling agent. The Fiber was treated with an 8% sodium hydroxide solution at 55°C for 450 minutes. After washing with distilled water until the pH value was 7, the Fiber was treated with silane coupling agent again. The ratio of silane coupling agent to distilled water to anhydrous ethanol was 10:70:20. The treatment time was 90 minutes.
[0097] (2) The components are mixed in a stepwise mixing manner. First, the Caragana korshinskii fiber, sepiolite fiber and composite mineral fiber are added to the mixer and mixed for 15 minutes at a stirring speed of 1500 rpm. Then, phenolic resin, friction modifier, filler and 1% of the total mass of low molecular weight acrylic resin binder are added to the above mixture and mixed for another 20 minutes at a stirring speed of 2700 rpm. The mixing process is carried out in an intermittent manner to prevent the high temperature of friction during the mixing process from damaging the structure of each component. The mixing is paused for 15 seconds after 30 seconds.
[0098] (3) The above-mentioned components were added to a granulator to prepare pre-granules, and anhydrous ethanol was slowly sprayed in during the stirring process. The entire granulation process consisted of three stages. The first stage was the nucleation stage, with a granulation time of 8 minutes, a stirring speed of 400 rpm, and a drum speed of 50 rpm. The second stage was the particle growth stage, with a granulation time of 25 minutes, a stirring speed of 400 rpm, and a drum speed of 130 rpm. The third stage was the particle densification stage, with a granulation time of 20 minutes, a stirring speed of 750 rpm, and a drum speed of 130 rpm. After granulation, the pre-granules were dried at a temperature of 80°C for 24 hours to remove the anhydrous ethanol from the bridging liquid. The pre-granules were sieved with a sieve, and particles with a diameter in the range of 3-5 mm were selected for the next step of preparation.
[0099] (4) Hot pressing: Weigh the specified mass of pre-made particles and put them into the mold for pressing. The pressing temperature is 170℃ and the pressing pressure is 12MPa. During the pressing process, multiple venting is set, and the venting time is 6 seconds each time. Among them, the first and second holding time is 5 seconds, the third, fourth and fifth holding time is 10 seconds, and the sixth holding time is 1000 seconds.
[0100] (5) Heat treatment: The pressed sample is placed in a heat treatment chamber for heat treatment to eliminate internal defects and residual stress of the material. The heat treatment time is 18 hours.
[0101] Example 3
[0102] A lightweight, copper-free braking friction material reinforced with Caragana korshinskii fiber and its preparation method are disclosed. The material is prepared using pre-formed particles of 5-8 mm in size. The Caragana korshinskii fiber accounts for 7% by mass. The contents of the remaining components are as follows: phenolic resin 7%, sepiolite fiber 8%, composite mineral fiber 21%, calcium carbonate 11%, vermiculite powder 5%, precipitated barium sulfate 17%, flake graphite 7%, petroleum coke 6%, alumina 7%, friction powder 2.5%, and zinc stearate 1.5%.
[0103] Lightweight, copper-free brake friction material reinforced with citronella fiber is prepared through the following steps:
[0104] (1) The Fiber of Caragana korshinskii was treated with alkali and silane coupling agent. The Fiber was treated with a 6% sodium hydroxide solution at 45°C for 450 minutes. After washing with distilled water until the pH value was 7, the Fiber was treated with silane coupling agent again. The ratio of silane coupling agent to distilled water to anhydrous ethanol was 6:74:20. The treatment time was 90 minutes.
[0105] (2) The components are mixed in a stepwise mixing manner. First, the Caragana korshinskii fiber, sepiolite fiber and composite mineral fiber are added to the mixer and mixed for 15 minutes at a speed of 1300 rpm. Then, phenolic resin, friction modifier, filler and 1% of the total mass of acrylic resin binder are added to the above mixture and mixed for another 15 minutes at a speed of 3000 rpm. The mixing process is carried out in an intermittent manner to prevent the high temperature of friction during the mixing process from damaging the structure of each component. The mixing is paused for 15 seconds after 30 seconds.
[0106] (3) The above-mentioned components were added to a granulator to prepare pre-granules. During the stirring process, anhydrous ethanol was slowly sprayed into the bridging liquid. The entire granulation process consisted of three stages. The first stage was the nucleation stage, with a granulation time of 8 minutes, a stirring speed of 400 rpm, and a drum speed of 70 rpm. The second stage was the particle growth stage, with a granulation time of 30 minutes, a stirring speed of 400 rpm, and a drum speed of 130 rpm. The third stage was the particle densification stage, with a granulation time of 20 minutes, a stirring speed of 800 rpm, and a drum speed of 130 rpm. After granulation, the pre-granules were dried at a temperature of 80°C for 24 hours. The pre-granules were then sieved using a sieve, and particles with a diameter in the range of 5-8 mm were selected for the next step of preparation.
[0107] (4) Hot pressing: Weigh the specified mass of pre-made particles and put them into the mold for pressing. The pressing temperature is 180℃ and the pressing pressure is 12MPa. During the pressing process, multiple venting is set, and the venting time is 6 seconds each time. Among them, the first and second holding time is 5 seconds, the third, fourth and fifth holding time is 10 seconds, and the sixth holding time is 1000 seconds.
[0108] (5) Heat treatment: The pressed sample is placed in a heat treatment chamber for heat treatment to remove internal defects and residual stress of the material. The heat treatment time is 18 hours.
[0109] Example 4
[0110] The lightweight, copper-free braking friction material reinforced with Caragana korshinskii fiber and its operation method are disclosed. The pre-formed particles have a diameter range of 1-8 mm. The Caragana korshinskii fiber accounts for 8% by mass. The contents of the remaining components are as follows: phenolic resin 11%, sepiolite fiber 7%, composite mineral fiber 22%, calcium carbonate 11%, vermiculite powder 4%, precipitated barium sulfate 16%, flake graphite 7%, petroleum coke 6%, alumina 5%, friction powder 2%, and zinc stearate 1%.
[0111] Lightweight, copper-free brake friction material reinforced with citronella fiber is prepared through the following steps:
[0112] (1) The Fiber of Caragana korshinskii was treated with alkali and silane coupling agent. The Fiber was treated with an 8% sodium hydroxide solution at 45°C for 400 minutes. After washing with distilled water until the pH value was 7, the Fiber was treated with silane coupling agent again. The ratio of silane coupling agent to distilled water to anhydrous ethanol was 10:70:20. The treatment time was 80 minutes.
[0113] (2) The components are mixed in a stepwise mixing manner. First, the Caragana korshinskii fiber, sepiolite fiber and composite mineral fiber are added to the mixer and mixed for 15 minutes at a stirring speed of 1500 rpm. Then, phenolic resin, friction modifier, filler and 1% of the total mass of acrylic resin binder are added to the above mixture and mixed for another 20 minutes at a stirring speed of 2800 rpm. The mixing process is carried out in an intermittent manner to prevent the high temperature of friction during the mixing process from damaging the structure of each component. The mixing is paused for 15 seconds after 30 seconds.
[0114] (3) The above-mentioned components were added to a granulator to prepare pre-granules, and anhydrous ethanol was slowly sprayed in during the stirring process. The entire granulation process was divided into three stages. The first stage was the nucleation stage, with a granulation time of 8 minutes, a stirring speed of 350 rpm, and a drum speed of 70 rpm; the second stage was the particle growth stage, with a granulation time of 30 minutes, a stirring speed of 350 rpm, and a drum speed of 130 rpm; the third stage was the particle densification stage, with a granulation time of 20 minutes, a stirring speed of 800 rpm, and a drum speed of 130 rpm; after granulation, the pre-granules were dried at a temperature of 80°C for 24 hours to remove the anhydrous ethanol from the bridging liquid; and the pre-granules were sieved with a sieve, and particles with a diameter in the range of 1-8 mm were taken for the next step of preparation.
[0115] (4) Hot pressing: Weigh the specified mass of pre-made particles and put them into the mold for pressing. The pressing temperature is 180℃ and the pressing pressure is 12MPa. During the pressing process, multiple venting is set, and the venting time is 6 seconds each time. Among them, the first and second holding time is 5 seconds, the third, fourth and fifth holding time is 10 seconds, and the sixth holding time is 900 seconds.
[0116] (5) Heat treatment: The pressed sample is placed in a heat treatment chamber for heat treatment to eliminate internal defects and residual stress of the material. The heat treatment time is 18 hours.
[0117] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A lightweight, copper-free braking friction material reinforced with citronella fiber, comprising a resin matrix, reinforcing fibers, fillers, friction modifiers, and processing aids, characterized in that... Components containing the following mass percentages: The resin matrix is phenolic resin accounting for 5%-13% of the total mass; The reinforcing fibers include 2%–10% of Caragana korshinskii fiber, 1%–9% of sepiolite fiber and 16%–24% of composite mineral fiber by weight. The filler comprises 9%–17% calcium carbonate, 1%–9% vermiculite powder, and 14%–22% precipitated barium sulfate by total mass. The friction performance modifier comprises 4%–12% flake graphite, 3%–11% petroleum coke, 2%–10% alumina, 1%–3% friction powder, and 0.3%–1.7% zinc stearate by weight. The process aids include low molecular weight acrylic resin and anhydrous ethanol, and the amount of low molecular weight acrylic resin added is 0.5% to 1.5% of the total mass of the above resin matrix, reinforcing fibers, fillers, and friction modifiers; The Caragana korshinskii fiber is treated with alkali and silane coupling agent to replace copper fiber and glass fiber. The Caragana korshinskii fiber is mixed with resin matrix, sepiolite fiber, composite mineral fiber, filler and friction modifier to prepare pre-particles. The pre-particles use anhydrous ethanol as the connecting liquid and low molecular weight acrylic resin as the binder.
2. The lightweight, copper-free braking friction material reinforced with styrax fiber according to claim 1, characterized in that, The aforementioned styrax fiber is used to replace copper fiber and glass fiber, reducing the density of friction materials by 6%-12% and improving the lightweighting of automotive parts. It has a diameter of 0.02-0.03 mm and a length of 0.5-2 mm.
3. The lightweight, copper-free braking friction material reinforced with styrax fiber according to claim 1, characterized in that, The alkaline treatment includes the following steps: Step 1: Use a 4%–10% sodium hydroxide solution to treat the Caragana korshinskii fiber at 40–60°C for 360–500 minutes. Step 2: After treatment, rinse the Caragana fibers in distilled water until the solution pH is 7. Step 3: After rinsing, air dry the lemon fiber and then place it in an oven at 90℃ for 24 hours.
4. The lightweight, copper-free braking friction material reinforced with citronella fiber according to claim 1, characterized in that, The silane coupling agent treatment process includes: Alkali-treated Caragana korshinskii fibers were placed in an aminosilane coupling agent solution for treatment. The solution was prepared by mass fraction as follows: 4%–12% distilled water, 68%–76% anhydrous ethanol, and 16%–24% silane coupling agent. The amount of silane coupling agent added was 3%–7% of the mass of the Caragana korshinskii fibers. The treatment time was 60–100 minutes. After treatment, the Caragana korshinskii fibers were washed with distilled water and then placed in an oven to dry at 90°C for 24 hours.
5. A method for preparing a lightweight, copper-free braking friction material reinforced with *Caragana korshinskii* fiber as described in any one of claims 1-4, characterized in that, The preparation process includes: Step (1) Pretreatment of Caragana korshinskii fibers: 1) The obtained Caragana fibers are hammered, rubbed and washed to remove the wood and bark. The Caragana fibers are placed in a 4%-10% sodium hydroxide solution and treated at 40-60℃ for 360-500 minutes. They are then washed with distilled water until the solution pH is 7 and dried in an oven at 90℃ for 24 hours. 2) After drying, the Caragana spp. fibers are placed in an aminosilane coupling agent solution for 60-100 minutes. After the treatment, the Caragana spp. fibers are washed with distilled water and then placed in an oven to dry at 90°C for 24 hours. Step (2) Step mixing: 1) Put the pretreated Caragana korshinskii fiber and other reinforcing fibers into a mixer for mixing. The mixing speed is 1300-1500 rpm and the mixing time is 5-15 minutes. 2) Add phenolic resin, friction modifier, filler and low molecular weight acrylic resin binder with a mass fraction of 0.5%-1.5% to the above mixture and continue mixing. The stirring speed is 2700-3000 rpm and the mixing time is 10-20 minutes. Step (3) Preparation of pre-formed granules: Add the mixture from step (2) to a granulator for granulation. During the granulation process, slowly spray anhydrous ethanol. After granulation, dry the pre-made particles at a temperature of 80°C for 24 hours. Then, sieve the pre-made particles and take particles of different diameter ranges for the next step of preparation. Step (4) Hot pressing: The pre-formed granules of a specified quality are placed into a mold for pressing. The pressing temperature is 150-190℃ and the pressing pressure is 10-12MPa. During the pressing process, multiple venting operations are set, with each venting time being 5-8 seconds. The first and second holding times are 3-5 seconds, the third, fourth, and fifth holding times are 5-15 seconds, and the sixth holding time is 800-1000 seconds. Step (5) Heat treatment: The pressed sample is placed in a heat treatment chamber for heat treatment to eliminate residual stress and defects inside the material.
6. The method of operating the lightweight, copper-free braking friction material reinforced with sage fiber according to claim 5, characterized in that, The preformed particles are prepared using anhydrous ethanol as a forsythia extract and acrylic resin as a binder.
7. The method of operating the lightweight, copper-free braking friction material reinforced with sage fiber according to claim 5, characterized in that, The pre-particle preparation process in step (3) is divided into three stages, specifically including: The first stage is the nucleation stage, which adopts a low-speed mode with a stirrer speed of 300-400 rpm and a drum speed of 50-70 rpm, lasting for 5-8 minutes. The second stage is the particle growth stage, which adopts a medium-speed mode with a stirring blade speed of 300-400 rpm and a drum speed of 110-130 rpm, lasting for 20-30 minutes. The third stage is the particle compaction stage, which adopts a high-speed mode with a stirring blade speed of 700-800 rpm and a drum speed of 110-130 rpm, lasting for 10-20 minutes.