A method for preparing a graphene-reinforced composite brake pad

Abstract

The application provides a preparation method of a graphene reinforced composite brake pad and belongs to the field of friction materials. The brake pad uses graphene as a reinforcing agent to improve high-temperature resistance and thermal conductivity; meanwhile, nano-aluminum oxide and nano-silicon carbide are added to enhance the mechanical properties of the friction material. A hot-pressing sintering process is used to densify the material and improve wear resistance. The brake pad has high wear resistance, high thermal conductivity, a stable friction coefficient and excellent high-temperature heat resistance, and is suitable for high-performance brake systems.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of friction materials, and particularly to a preparation method of a graphene reinforced composite brake pad. BACKGROUND

[0002] Brake pads, as key safety components in automotive, train, motorcycle and industrial braking systems, directly affect the braking effect and safety of vehicles. Currently, brake pads on the market are mainly divided into three categories: metal-based brake pads (semi-metallic, low-metal), ceramic-based brake pads and resin-based brake pads (non-metallic organic brake pads). Different types of brake pads have their own advantages and disadvantages in performance, cost and application environment.

[0003] The main problems of existing brake pads are as follows: metal-based brake pads (such as semi-metallic brake pads) are widely used in high-load working conditions due to their high strength and good heat dissipation. However, they have the following shortcomings: easy to oxidize under high temperature conditions, leading to performance degradation; high hardness, causing large wear on the brake disc and affecting the service life of the braking system; noise or rust problems may occur in low temperature or humid environments. Ceramic-based brake pads are mainly used in high-end cars and racing cars, and have excellent high-temperature resistance and low dust generation. However, they have the following problems: high manufacturing cost, difficult to be popularized to ordinary vehicles on a large scale; the risk of material cracking may occur under extreme working conditions (such as long-time severe braking). Resin-based brake pads are made of phenolic resin as the matrix, adding various fillers and reinforcing materials, and have the advantages of low noise and low dust, and are widely used in passenger cars and commercial vehicles. However, their disadvantages include: poor heat dissipation, prone to friction coefficient decay (thermal decay) in high temperature environments; low wear resistance, short service life; greatly affected by the environment, such as performance degradation in high humidity. Therefore, there is still room for improvement in the high-temperature stability, friction performance and wear resistance of existing brake pads, especially in high-speed and high-load working conditions, traditional brake pads are difficult to balance excellent friction performance and wear resistance.

[0004] In recent years, the introduction of new nanomaterials has provided a new direction for the improvement of brake pad performance. Among them, graphene has great potential in the field of friction materials due to its ultra-high thermal conductivity, mechanical strength and high-temperature resistance. Studies have shown that an appropriate amount of graphene can: improve thermal conductivity, accelerate brake heat dissipation, and reduce thermal decay problems; enhance material strength, improve the wear resistance and impact resistance of the matrix; optimize the friction performance, maintain a stable friction coefficient under high temperature and high speed braking conditions.

[0005] Although the application of graphene in brake pads has great potential, there are still the following technical difficulties: dispersion problem of graphene: graphene is prone to agglomeration, resulting in uneven distribution in the composite material, which ultimately affects the high-temperature resistance of the brake pad, causes obvious thermal decay phenomenon, and unstable friction performance; poor wear resistance, affecting the service life of the brake pad. SUMMARY

[0006] To overcome at least one of the technical problems in the above background art, the present method proposes a preparation method of graphene reinforced composite brake pad, which overcomes the shortcomings of the existing brake pad by the following technical scheme:

[0007] The preparation method of the graphene reinforced composite brake pad is characterized by the following steps:

[0008] (1) batching: each component is weighed according to the proportion of raw materials;

[0009] (2) mixing: graphene, nano-alumina, nano-silicon carbide, fiber reinforced material, filler, phenolic resin matrix, curing agent, lubricant, silane coupling agent and brake pad synergistic additive are added into a high-speed mixer and mixed at 500-1500 rpm for 30-120 min, or wet mixing is performed by a planetary ball mill at 300-800 rpm for 1-4 h;

[0010] (3) preforming: the mixed material is placed in a mold and cold pressed at a pressure of 5-20 MPa, a forming temperature of 25-80℃ and a pressure holding time of 30-300 s;

[0011] (4) hot pressing and sintering: sintering is performed at 150-250℃ and 10-50 MPa for 1-3 h, and the temperature rising rate is 2-10℃ / min, so as to densify the composite material and improve the mechanical properties and wear resistance;

[0012] (5) post-treatment and detection: the finished product is trimmed in size, and the hardness, friction coefficient, wear resistance and other indicators are detected, and then packaged and stored.

[0013] As a preferred embodiment of the preparation method of the present application, the proportion of the raw materials is as follows in terms of mass fraction:

[0014] Graphene: 0.5-5 parts;

[0015] Nano-alumina: 2-10 parts;

[0016] Nano-silicon carbide: 3-12 parts;

[0017] Fiber reinforced material: 5-20 parts;

[0018] Phenolic resin matrix: 20-40 parts;

[0019] Filler: 10-30 parts;

[0020] Curing agent: 3-10 parts;

[0021] Lubricant: 0.5-5 parts;

[0022] Silane coupling agent: 0.1-1 part;

[0023] Brake pad enhancement additive: 0.2-2 parts.

[0024] In a preferred embodiment of the preparation method described in this invention, the graphene is a single-layer or few-layer graphene with a sheet diameter of 0.5-5 μm and a thickness of ≤10 nm.

[0025] In a preferred embodiment of the preparation method described in this invention, the fiber-reinforcing material includes at least one of glass fiber, aramid fiber, and basalt fiber.

[0026] In a preferred embodiment of the preparation method of the present invention, the filler includes at least one of barium sulfate, wollastonite, expanded graphite, and mica powder.

[0027] In a preferred embodiment of the preparation method of the present invention, the curing agent includes at least one of hexamethylenetetramine and benzenesulfonyl chloride.

[0028] In a preferred embodiment of the preparation method of the present invention, the lubricant includes at least one of graphite and MoS2.

[0029] As a preferred embodiment of the preparation method of the present invention, the silane coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane.

[0030] As a preferred embodiment of the preparation method described in this invention, the preparation method of the brake pad synergist is as follows:

[0031] Thiol ring opening: Take 100 parts of 2-[(thiophen-2-ylmethoxy)methyl]epoxyethylene and 120-150 parts of mercaptoacetic ethanolamine into a reaction vessel, add 5-10 parts of sodium hydroxide as a catalyst, and react at 40℃-60℃ for 2-4 hours.

[0032] Selenene addition: Add 100-120 parts allylphenyl selenium and 1-3 parts AIBN to the above system, initiate double bond addition at 60℃-80℃, and react for 3-5 hours to obtain brake pad synergist.

[0033] Technical effects:

[0034] 1) Improve thermal conductivity and reduce thermal decay:

[0035] The high thermal conductivity of graphene allows the heat generated by friction in brake pads to be transferred to the surface and dissipated more quickly, thereby reducing the accumulation of local high temperatures, reducing the problem of decreased friction coefficient (thermal fade) caused by temperature rise, and improving braking stability under high temperature conditions.

[0036] The thioether bonds formed in the synergist have high bond energy, which can effectively enhance the high temperature resistance of brake pads, enabling them to maintain good performance stability in high temperature environments and reduce performance degradation caused by high temperature.

[0037] 2) Enhanced wear resistance and improved brake pad lifespan: The high hardness of nano-alumina and nano-silicon carbide can effectively enhance the wear resistance of the matrix, reduce the wear rate of the material during braking, thereby extending the service life of the brake pads, while reducing dust generation and reducing damage to the brake disc.

[0038] 3) Stable friction performance: The selenium group in allyl phenyl selenium can effectively regulate the friction interface, making the friction coefficient more stable and avoiding excessive fluctuations in the friction coefficient, thus improving the braking performance and safety of the brake pads. Detailed Implementation

[0039] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0040] The reagents used in the embodiments and comparative examples of this invention are all commercially available, but are not limited to these materials.

[0041] Example 1

[0042] Raw material composition:

[0043] Graphene: 1.0 kg

[0044] Nano-alumina: 5.0kg

[0045] Nano-silicon carbide: 6.0 kg

[0046] Fiberglass: 10.0kg

[0047] Phenolic resin matrix: 30.0 kg

[0048] Filler (wollastonite + mica powder = 1:1): 20.0 kg

[0049] Curing agent (hexamethylenetetramine): 5.0 kg

[0050] Lubricant (graphite + MoS2 = 1:1): 2.0 kg

[0051] Silane coupling agent (γ-aminopropyltriethoxysilane): 0.5 kg

[0052] Brake pad performance enhancer: 0.5kg

[0053] Preparation method of brake pad enhancement agent: Thiol ring opening: Take 1000g of 2-[(thiophene-2-ylmethoxy)methyl]ethylene oxide and 1200g of mercaptoacetic acid ethanolamine and add them to the reaction vessel. Add 50g of sodium hydroxide as a catalyst and react at 40℃ for 4 hours; Selenene addition: Add 1000g of allyl phenyl selenium and 10g of AIBN to the above system and initiate double bond addition at 60℃. React for 5 hours to obtain brake pad enhancement agent.

[0054] Preparation steps:

[0055] 1. Mixing: Add the above raw materials to a high-speed mixer and stir at 1000 rpm for 60 minutes;

[0056] 2. Pre-forming: The mixture is cold-pressed at a pressure of 10 MPa, a temperature of 60℃, and a holding time of 150 s;

[0057] 3. Hot pressing sintering: heating rate 5℃ / min, temperature 200℃, pressure 30MPa, holding time 2h;

[0058] 4. Post-processing: Perform dimensional trimming and friction performance testing.

[0059] Example 2

[0060] Raw material composition:

[0061] Graphene: 2.5kg

[0062] Nano-alumina: 7.0kg

[0063] Nano-silicon carbide: 10.0 kg

[0064] Aramid fiber: 15.0kg

[0065] Phenolic resin matrix: 35.0 kg

[0066] Filler (expanded graphite): 25.0 kg

[0067] Curing agent (benzenesulfonyl chloride): 6.0 kg

[0068] Lubricant (MoS2): 3.0 kg

[0069] Silane coupling agent (γ-methacryloyloxypropyltrimethoxysilane): 0.7 kg

[0070] Brake pad performance enhancer: 1.0kg

[0071] Preparation method of brake pad enhancement agent: Thiol ring opening: Take 1000g of 2-[(thiophene-2-ylmethoxy)methyl]ethylene oxide and 1300g of mercaptoacetic acid ethanolamine and add them to the reaction vessel. Add 65g of sodium hydroxide as a catalyst and react at 50℃ for 3 hours; Selenene addition: Add 1100g of allyl phenyl selenium and 20g of AIBN to the above system and initiate double bond addition at 70℃. React for 4 hours to obtain the brake pad enhancement agent.

[0072] Preparation steps:

[0073] 1. Mixing: The raw materials are wet-mixed using a planetary ball mill at 400 rpm for 3 hours;

[0074] 2. Pre-forming: Pressure 15MPa, temperature 40℃, holding time 180s;

[0075] 3. Hot pressing sintering: heating rate 6℃ / min, sintering temperature 220℃, pressure 40MPa, time 2.5h;

[0076] 4. Post-processing and testing: After polishing, test the coefficient of friction and wear resistance.

[0077] Example 3

[0078] Raw material composition:

[0079] Graphene: 0.8kg

[0080] Nano-alumina: 3.0kg

[0081] Nano-silicon carbide: 4.5kg

[0082] Basalt fiber: 8.0 kg

[0083] Phenolic resin matrix: 25.0 kg

[0084] Filler (barium sulfate + mica powder = 2:1): 15.0 kg

[0085] Curing agent (hexamethylenetetramine): 4.0 kg

[0086] Lubricant (graphite): 1.0 kg

[0087] Silane coupling agent (γ-glycidoxypropyltrimethoxysilane): 0.3 kg

[0088] Brake pad performance enhancer: 1.5kg

[0089] Preparation method of brake pad enhancement agent: Thiol ring opening: Take 1000g of 2-[(thiophen-2-ylmethoxy)methyl]ethylene oxide and 1400g of mercaptoacetic acid ethanolamine and add them to the reaction vessel. Add 80g of sodium hydroxide as a catalyst and react at 50℃ for 3 hours; Selenene addition: Add 1100g of allyl phenyl selenium and 20g of AIBN to the above system and initiate double bond addition at 70℃. React for 4 hours to obtain the brake pad enhancement agent.

[0090] Preparation steps:

[0091] 1. Mixing: Mix using a high-speed mixer at 750 rpm for 90 minutes;

[0092] 2. Pre-forming: Pressure 12MPa, forming temperature 50℃, holding time 200s;

[0093] 3. Hot pressing sintering: heating rate 4℃ / min, sintering temperature 180℃, pressure 20MPa, holding time 2h;

[0094] 4. Post-processing and testing: Inspect hardness and friction and wear properties.

[0095] Example 4

[0096] Raw material composition:

[0097] Graphene: 4.0 kg

[0098] Nano-alumina: 9.0 kg

[0099] Nano-silicon carbide: 11.0 kg

[0100] Aramid fiber + glass fiber blend (1:1): 18.0 kg

[0101] Phenolic resin matrix: 38.0 kg

[0102] Filler (expanded graphite + mica powder = 3:2): 28.0 kg

[0103] Curing agent (benzenesulfonyl chloride): 8.0 kg

[0104] Lubricant (graphite + MoS2 = 2:1): 4.0 kg

[0105] Silane coupling agent (γ-aminopropyltriethoxysilane): 1.0 kg

[0106] Brake pad performance enhancer: 2.0kg

[0107] Preparation method of brake pad enhancement agent: Thiol ring opening: Take 1000g of 2-[(thiophene-2-ylmethoxy)methyl]ethylene oxide and 1500g of mercaptoacetic acid ethanolamine and add them to the reaction vessel. Add 100g of sodium hydroxide as a catalyst and react at 60℃ for 2 hours; Selenene addition: Add 1200g of allyl phenyl selenium and 30g of AIBN to the above system and initiate double bond addition at 80℃. React for 3 hours to obtain the brake pad enhancement agent.

[0108] Preparation steps:

[0109] 1. Mixing: Wet mixing in a planetary ball mill at 600 rpm for 4 hours;

[0110] 2. Pre-forming: Pressure 18MPa, forming temperature 70℃, holding time 250s;

[0111] 3. Hot pressing sintering: heating rate 8℃ / min, temperature 240℃, pressure 45MPa, time 3h;

[0112] 4. Post-processing: Deburring, polishing, and comprehensive inspection.

[0113] Comparative Example 1

[0114] In this example, no brake pad enhancement additive is added, and the remaining steps are the same as in Example 1.

[0115] Comparative Example 2

[0116] In this example, 2-[(thiophene-2-ylmethoxy)methyl]ethylene oxide is not added during the preparation of the brake pad enhancement agent; the remaining steps are the same as in Example 1.

[0117] Comparative Example 3

[0118] In this example, mercaptoacetic acid ethanolamine is not added during the preparation of the brake pad enhancement agent, and the remaining steps are the same as in Example 1.

[0119] Test method:

[0120] (1) Friction performance test

[0121] Test standard: SAE J661 friction performance test standard

[0122] Testing equipment: Friction testing machine

[0123] Test conditions: Initial temperature 25℃, friction surface temperature rises to 300℃, and the coefficient of friction is measured.

[0124] Table 1: Tribological Performance Test Results of Examples and Comparative Examples

[0125] 25℃ 100℃ 200℃ 300℃ Example 1 0.38 0.39 0.40 0.39 Example 2 0.39 0.41 0.42 0.40 Example 3 0.41 0.42 0.43 0.42 Example 4 0.42 0.43 0.44 0.43 Comparative Example 1 0.34 0.35 0.33 0.30 Comparative Example 2 0.36 0.37 0.35 0.32 Comparative Example 3 0.36 0.36 0.35 0.33

[0126] (2) Abrasion resistance test

[0127] Test standard: ISO 7148-2 Abrasion resistance test

[0128] Testing equipment: Friction and wear testing machine

[0129] Test method: Under constant pressure of 1.5 MPa and rotation speed of 500 rpm, the brake pads were subjected to 10,000 consecutive friction cycles to determine the mass loss.

[0130] Table 2: Abrasion resistance test results of the examples and comparative examples

[0131] Mass loss mg Example 1 25 Example 2 23 Example 3 21 Example 4 20 Comparative Example 1 33 Comparative Example 2 30 Comparative Example 3 29

[0132] (3) High temperature stability test

[0133] Test Standard: JASOC406 High Temperature Degradation Test

[0134] Testing equipment: High-temperature friction testing machine

[0135] Test method: The brake pads were kept at 400℃ for 10 minutes, and the change in the coefficient of friction was measured.

[0136] Table 3: High-Temperature Stability Test Results of Examples and Comparative Examples

[0137] Friction coefficient reduction rate (%) Example 1 5.2 Example 2 4.7 Example 3 4.4 Example 4 4.2 Comparative Example 1 6.7 Comparative Example 2 6.0 Comparative Example 3 6.1

[0138] As can be seen from the above embodiments and test results, this method effectively improves the friction performance, wear resistance and high temperature stability of brake pads.

[0139] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing graphene-reinforced composite brake pads, characterized in that, The preparation is carried out using the following steps: (1) Ingredients: Weigh each component according to the proportion of raw materials; (2) Mixing: Add graphene, nano alumina, nano silicon carbide, fiber reinforcement material, filler, phenolic resin matrix, curing agent, lubricant, silane coupling agent and brake pad synergist into a high-speed mixer and mix at 500-1500 rpm for 30-120 min, or use a planetary ball mill to wet mix at 300-800 rpm for 1-4 h; (3) Pre-forming: The mixed material is placed in a mold and cold-pressed under a pressure of 5-20 MPa. The molding temperature is 25-80℃ and the holding time is 30-300 s. (4) Hot pressing sintering: Sintering at 150-250℃ and 10-50 MPa for 1-3 h with a heating rate of 2-10℃ / min to densify the composite material and improve its mechanical properties and wear resistance. (5) Post-processing and inspection: The finished product is dimensionally adjusted, and its hardness, friction coefficient, wear resistance and other indicators are tested and packaged for storage; The brake pad enhancement agent is prepared by reacting 2-[(thiophene-2-ylmethoxy)methyl]ethylene oxide, mercaptoacetic acid ethanolamine, sodium hydroxide, allylphenyl selenide, and AIBN. The preparation method of the brake pad enhancement additive: Thiol ring opening: Take 100 parts of 2-[(thiophen-2-ylmethoxy)methyl]epoxyethylene and 120-150 parts of mercaptoacetic ethanolamine into a reaction vessel, add 5-10 parts of sodium hydroxide as a catalyst, and react at 40℃-60℃ for 2-4 hours. Selenene addition: Add 100-120 parts allylphenyl selenium and 1-3 parts AIBN to the above system, initiate double bond addition at 60℃-80℃, and react for 3-5 hours to obtain brake pad synergist.

2. The method for preparing a graphene-reinforced composite brake pad according to claim 1, characterized in that: The proportions of the raw materials are as follows (parts by mass): Graphene: 0.5-5 parts; Nano-alumina: 2-10 parts; Nano-silicon carbide: 3-12 parts; Fiber-reinforced material: 5-20 parts; Phenolic resin matrix: 20-40 parts; Filler: 10-30 parts; Hardener: 3-10 parts; Lubricant: 0.5-5 parts; Silane coupling agent: 0.1-1 part; Brake pad enhancement additive: 0.2-2 parts.

3. The method for preparing a graphene-reinforced composite brake pad according to claim 1, characterized in that: The graphene is a single-layer or few-layer graphene with a sheet diameter of 0.5-5 μm and a thickness of ≤10 nm.

4. The method for preparing a graphene-reinforced composite brake pad according to claim 1, characterized in that: The fiber-reinforced material includes at least one of glass fiber, aramid fiber, and basalt fiber.

5. The method for preparing a graphene-reinforced composite brake pad according to claim 1, characterized in that: The filler includes at least one of barium sulfate, wollastonite, expanded graphite, and mica powder.

6. The method for preparing a graphene-reinforced composite brake pad according to claim 1, characterized in that: The curing agent includes at least one of hexamethylenetetramine and benzenesulfonyl chloride.

7. The method for preparing a graphene-reinforced composite brake pad according to claim 1, characterized in that: The lubricant includes at least one of graphite and MoS2.

8. The method for preparing a graphene-reinforced composite brake pad according to claim 1, characterized in that: The silane coupling agent includes at least one of γ-aminopropyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane.