A rust-resistant and adhesive friction material for automobiles and its preparation method

Abstract

This invention discloses a rust-preventing and bonding friction material for automobiles and its preparation method. The raw materials include: 5-20% phenolic resin, 20-40% reinforcing fiber, 25-45% friction filler, and 15-30% functional filler; the functional filler is zinc hexadecyl phosphate modified nano-silica. Zinc hexadecyl phosphate is added to anhydrous ethanol and heated in a water bath to obtain a ZHP dispersion. The dried nano-silica is added to anhydrous ethanol, heated in a water bath with stirring, and then the ZHP dispersion is added dropwise while stirring. After the addition is complete, the mixture is kept at a constant temperature and refluxed for reaction. After the reaction is complete, the solid product is separated, washed with anhydrous ethanol, and vacuum dried to obtain zinc hexadecyl phosphate modified nano-silica. This invention provides a simple friction material formulation, uses few raw materials, and has a simple preparation method, which can effectively reduce the cost of friction materials and improve their wear resistance, prevent rust adhesion, and extend the service life of braking devices.

Description

Technical Field

[0001] This invention relates to the field of friction pad technology, specifically to a rust-resistant bonding friction material for automobiles and its preparation method. Background Technology

[0002] With the rapid development of the automotive industry and policies encouraging car consumption, the production and sales of automobiles are expected to maintain a positive momentum in the future. Consequently, the demand for friction materials will increase dramatically. Friction materials are functional materials used in automobiles that rely on friction to achieve braking and transmission. During braking, friction materials convert kinetic energy into heat energy through friction with their mating surfaces, thus achieving braking. They are crucial for ensuring the safe and stable operation of automobiles, and their performance directly determines the braking effect.

[0003] Currently, the friction pad materials used in passenger vehicles can be broadly categorized into semi-metallic and low-metallic friction materials, as well as asbestos-free organic (NAO) friction materials (hereinafter referred to as NAO friction materials). Automotive disc brakes, due to the friction pads being exposed to the environment, are subject to complex conditions such as water exposure, rain, and car washes, which can significantly impact brake performance and cause unpredictable problems. Rust adhesion between the friction pads and the brake disc is a typical example. One major reason for rust adhesion between the friction pads and the brake disc is excessive heating, which decomposes organic matter within the pads, promoting the formation of pores on the pad surface. Carbonization enlarges the pores, making them more susceptible to moisture penetration. The iron in the contact area between the brake disc and the friction pad is oxidized, producing iron oxide (Fe2O3 and Fe3O4) between the brake disc and the friction pad, thus causing rust adhesion. Furthermore, semi-metallic and low-metallic friction materials in friction pads, containing steel fibers and iron powder, are highly prone to rusting in water and humid air. Although NAO friction materials do not contain ferrous metals, due to the porous nature of their surface, rust easily penetrates into the surface pores when the brake disc rusts. Rust adhesion causes the brake disc and friction pads to stick together, which in severe cases can render the car immobile or cause the tires to slip on the ground.

[0004] Currently, rust-preventing adhesion mainly relies on physical isolation using graphite and molybdenum disulfide, supplemented by sacrificial anode protection with metal powders such as zinc powder, and further addressed through the compounding of various substances, including passivators. Nano-silica particles are extremely small and can be uniformly dispersed in the matrix of friction materials (such as resin and rubber). Their high specific surface area provides a large contact area with the matrix material, generating strong interfacial interactions that effectively transfer and disperse stress, thereby improving the mechanical strength, hardness, and wear resistance of the friction pads. Furthermore, nano-silica itself possesses high thermal stability and high-temperature resistance. Under the high temperatures generated by braking, it maintains structural stability and is not easily decomposed or failed, helping to maintain the performance of friction materials at high temperatures and slowing down thermal degradation. Although there are some reports of using silica in the manufacture of friction materials, there are no reports of its use for rust-preventing adhesion. If silica could be endowed with rust-preventing adhesion capabilities, the use of anti-adhesion additives could be reduced. Summary of the Invention

[0005] To address the aforementioned limitations of the prior art, the present invention aims to provide a rust-resistant and adhesive friction material for automobiles and its preparation method. This invention uses zinc hexadecyl phosphate modified nano-silica as a functional filler, which not only improves the wear resistance of the friction pads but also makes them hydrophobic, preventing moisture penetration and rust adhesion. The zinc hexadecyl phosphate contains Zn... 2+ It has a certain passivation and rust prevention effect, further preventing rust adhesion. Silica can also improve the heat resistance of friction materials, and the multiple effects work together to prevent rust adhesion.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A first aspect of the present invention provides a rust-resistant and adhesive friction material for automobiles, comprising the following raw materials in weight percentages:

[0008] Phenolic resin 5-20%, reinforcing fiber 20-40%, friction filler 25-45%, functional filler 15-30%;

[0009] The functional filler is zinc hexadecyl phosphate modified nano-silica.

[0010] Preferably, the phenolic resin is pure phenolic resin, cashew oil-modified phenolic resin, or boron-modified phenolic resin.

[0011] Preferably, the reinforcing fiber is at least one of ceramic fiber, aramid fiber, and mineral fiber; the mineral fiber is a non-asbestos mineral fiber.

[0012] Preferably, the friction filler is selected from at least one of graphite, molybdenum disulfide, barium sulfate, zirconium oxide, alumina, zirconium silicate, or calcium carbonate.

[0013] Preferably, the zinc hexadecyl phosphate modified nano-silica is prepared by the following method:

[0014] Zinc hexadecyl phosphate was added to anhydrous ethanol and heated in a water bath to obtain a ZHP dispersion. Dried nano-silica was added to anhydrous ethanol and heated in a water bath with stirring. Then, the ZHP dispersion was added dropwise with stirring. After the addition was complete, the mixture was kept warm and refluxed. After the reaction was completed, the solid product was separated, washed with anhydrous ethanol, and dried under vacuum to obtain zinc hexadecyl phosphate modified nano-silica.

[0015] Preferably, the mass ratio of zinc hexadecyl phosphate to nano silica is 1~3:10; the particle size of the nano silica is 10~40nm; and the dropping rate is 1~2mL / min.

[0016] Preferably, the water bath heating temperature is 60~70℃; the reflux reaction time is 8~16h; and the vacuum drying temperature is 60℃ for 4~8h.

[0017] A second aspect of the present invention provides a method for preparing a rust-resistant and adhesive friction material for automobiles, the method comprising:

[0018] The weighed phenolic resin, reinforcing fibers, friction filler, and functional filler are mixed together to obtain the mixture.

[0019] The friction material is obtained by hot pressing and then curing.

[0020] Preferably, the hot pressing temperature is 150~170℃, the pressure is 20~30MPa, and the time is 5~15min; the curing temperature is 180℃, and the time is 6~8h.

[0021] A third aspect of the invention provides the application of rust-resistant bonding friction materials for automobiles in reducing rust adhesion between friction pads and brake discs.

[0022] The beneficial effects of this invention are:

[0023] (1) This invention uses zinc hexadecyl phosphate modified nano-silica as a functional filler, which can not only improve the wear resistance of the friction plate, but also make the friction plate hydrophobic, preventing water vapor from penetrating into the friction plate and causing rust adhesion. The Zn in zinc hexadecyl phosphate 2+ It has a certain passivation and rust prevention effect, further preventing rust adhesion. Silica can also improve the heat resistance of friction materials, and the multiple effects work together to prevent rust adhesion.

[0024] (2) The friction material of the present invention has a simple formulation, few types of raw materials, and a simple preparation method, which can effectively reduce the cost of friction materials and improve their wear resistance and prevent rust adhesion. It also extends the service life of the braking device. Attached Figure Description

[0025] Figure 1 Photographs of the friction plates prepared in Example 1 and Comparative Examples 1-3 after rust adhesion tests. Detailed Implementation

[0026] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0027] As described in the background section, the two key factors causing rust adhesion are high temperature and moisture. Therefore, to avoid rust adhesion, zinc powder with good thermal conductivity or lubricating materials such as graphite are usually added to the friction material to reduce adhesion points on the friction plate surface. Silica is a good wear-resistant and high-temperature resistant material, but it has not been used in rust adhesion prevention.

[0028] Based on this, the purpose of this invention is to provide a rust-resistant and adhesive friction material for automobiles and its preparation method. This invention modifies nano-silica for use as a functional filler, which can improve the wear resistance of the friction material and prevent rust adhesion. However, nano-silica is prone to agglomeration; modification can solve this agglomeration problem, achieving multiple benefits. Specifically, this application selected zinc hexadecyl phosphate (ZHP) to modify silica. Zinc hexadecyl phosphate is an amphiphilic material composed of long-chain alkyl groups and phosphate groups, with a molecular structure containing a hydrophilic head phosphate group and a long-chain alkyl hydrophobic tail. The silica surface is rich in silanol groups (-SiOH). Strong coordination and electrostatic interactions exist between the phosphate group (-PO4²⁻) of the ZHP molecule, the silanol groups (-SiOH) on the silica surface, and the zinc ions of ZHP itself. Phosphate ions can partially replace the protons of silanol groups and form strong bonds with or through zinc ions on the surface, such as SiO⁻...Zn²⁺...⁻O3P-OR or SiOH...⁻O3P-OR, thus anchoring ZHP molecules to the silica surface. The long-chain alkyl groups extend outwards, imparting hydrophobicity to the material. Thus, zinc hexadecyl phosphate modified nano-silica (ZHP@SiO2) has a hydrophobic surface, preventing silica agglomeration and providing hydrophobicity and isolation to the friction material, making it less prone to moisture binding and preventing rust adhesion. Furthermore, the Zn in zinc hexadecyl phosphate... 2+It has a certain passivation and rust-preventing effect, protecting iron from oxidation and rusting. Therefore, ZHP@SiO2, as a functional filler, can not only improve the wear resistance, mechanical strength, hardness, and maintain structural stability of friction materials, but also make the friction materials hydrophobic and protect iron from oxidation, thus playing a role in rust prevention and adhesion.

[0029] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0030] The test materials used in the embodiments of this invention are all conventional test materials in the art and can be purchased through commercial channels.

[0031] Example 1

[0032] (1) Place silica particles with a particle size of 10~40nm in a vacuum oven and dry them at 120℃ for 6h to obtain dried nano silica. Add 0.8g of zinc hexadecyl phosphate to 50mL of anhydrous ethanol, stir and sonicate in a 60℃ water bath for 20min to obtain ZHP dispersion. Add 4g of dried nano silica to 200mL of anhydrous ethanol, heat to 70℃ in a water bath and stir for 30min to obtain SiO2 dispersion. Add the ZHP dispersion dropwise to the SiO2 dispersion at a rate of 1mL / min, and reflux at 70℃ for 10h. After the reaction is complete, filter to obtain the precipitate, wash repeatedly with anhydrous ethanol 3~4 times to wash away unreacted ZHP; then dry in a vacuum oven at 60℃ for 6h to obtain zinc hexadecyl phosphate modified nano silica (ZHP@SiO2).

[0033] (2) Weigh the following by weight percentage: 12% phenolic resin, 20% ceramic fiber, 6% aramid fiber, 5% alumina, 5% zirconium oxide, 10% graphite, 12% barium sulfate, and 30% ZHP@SiO2 prepared in step (1). Add these to a mixer and mix to obtain a mixture. Put the mixture into a hot press and hot press at 160℃ and 25 MPa for 10 min. Place the hot-pressed product in an oven and cure at 180℃ for 7 h to obtain a friction pad (i.e., friction material).

[0034] Comparative Example 1

[0035] The difference from Example 1 is that an equal amount of nano-silica is used instead of ZHP@SiO2. The final product is a friction pad (i.e., friction material).

[0036] Comparative Example 2

[0037] The difference from Example 1 is that nano-silica + ZHP (the same amount of nano-silica and ZHP as in ZHP@SiO2) is used instead of ZHP@SiO2, and the mass ratio of nano-silica to ZHP is 5:1. The final product is a friction pad (i.e., friction material).

[0038] Comparative Example 3

[0039] The difference from Example 1 is that an equal amount of nano-silicon carbide (particle size 10~40nm) is used instead of ZHP@SiO2. The final product is a friction pad (i.e., friction material).

[0040] Experimental Example 1

[0041] The friction properties of the friction plates prepared in Example 1 and Comparative Examples 1-3 were tested:

[0042] (1) Coefficient of friction

[0043] The friction coefficients of the friction plates of Example 1 and Comparative Examples 1-3 were tested according to the AK-Master (SAE J2522-2013) standard, and the results are shown in Table 1.

[0044] Table 1 Friction properties

[0045]

[0046] As shown in Table 1, compared with Comparative Examples 1 and 2, the friction coefficient of the friction sheet prepared in Example 1 is more stable at both low and high temperatures. The stability of the friction coefficient of Example 1 is close to that of Comparative Example 3, indicating that the friction material prepared by this invention has better friction performance.

[0047] (2) Wear amount

[0048] The wear of the friction pads prepared in Example 1 and Comparative Examples 1-3 was tested according to the method in "JASO C427-2009 Automotive Components - Brake Pads and Disc Brake Shoes - Wear Tests on Inertial Measurement Machines". The results are shown in Table 2.

[0049] Table 2 Wear Amount

[0050]

[0051] As shown in Table 2, the wear amount of the friction pad prepared in Example 1 is close to that of Comparative Example 3. Comparative Example 3 uses nano-silicon carbide, which has a higher Mohs hardness than nano-silica. Although Comparative Example 3 has a lower wear amount, it generates more noise and vibration during vehicle braking. The wear amount of Comparative Example 2 is lower than that of Comparative Example 1, which is related to the fact that ZHP, as a surfactant, can reduce the agglomeration of silica.

[0052] Experimental Example 2

[0053] The rust adhesion properties of the friction plates prepared in Example 1 and Comparative Examples 1-3 were tested:

[0054] (1) The rust adhesion test procedure is as follows: the speed is 250 r / min, and the brake is applied every 30 seconds to 0 r / min. After 30 test cycles, the brake and brake disc are immersed in 5% salt water. After 1 minute, they are taken out and the assembly and fastening are simulated on the actual vehicle with a clamping force of 17.5 KN. The brake disc is placed in a 5% salt spray chamber at a temperature of 35℃ and a humidity of 96% for 96 hours. The maximum pull-out force between the brake friction pad and the brake disc after the test is shown in Table 3. The photos of the friction pad after the test are shown in Table 3. Figure 1 .

[0055] (2) Simulated rust adhesion caused by abnormal braking system: The friction mode of the handbrake not being fully released was simulated using a LINK bench tester (LINK3000, USA). The handbrake was not fully released, resulting in friction braking equivalent to a driving distance of 20km, which caused carbonization of the friction pads. The test temperature was as follows: the highest temperature of the brake disc was 615℃, and the highest temperature of the friction pads was 153℃. After the test, the temperature was reduced to 40℃ and the pads were sprayed with water for 1 minute. The surface hardness of the friction pads before and after the test was tested, and the results are shown in Table 3.

[0056] Table 3 Rust Adhesion

[0057]

[0058] As shown in Table 3, the maximum pull-out force between the brake friction block and the brake disc after the test in Example 1 was much lower than that in Comparative Examples 1-3, indicating that Example 1 had the best rust-preventing and adhesion performance. The rust-adhesion performance of Comparative Example 2 was slightly higher than that of Comparative Example 1. This is because zinc hexadecyl phosphate is also a surfactant, which can reduce the aggregation of silica. However, it also has both hydrophobic and hydrophilic groups, thus slightly reducing rust adhesion. When the hydrophilic matrix of zinc hexadecyl phosphate is combined with silica, the modified silica only has hydrophobic groups, greatly improving the hydrophobicity of the friction material.

[0059] according to Figure 1 It can be seen that the friction pad of Example 1 showed neither a large number of pores nor obvious rust after the rust adhesion test, while the friction pads of Comparative Examples 1 to 3 showed obvious rust. According to Table 3, the simulation of braking system anomalies shows that Example 1 had the smallest change in hardness before and after the simulation, indicating that carbonization and water spray caused little compressive deformation to the friction pad, indicating that the friction pad had good anti-rust adhesion performance.

[0060] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A rust-resistant and adhesive friction material for automobiles, characterized in that, Including the following raw materials by weight percentage: Phenolic resin 5-20%, reinforcing fiber 20-40%, friction filler 25-45%, functional filler 15-30%; The functional filler is zinc hexadecyl phosphate modified nano-silica; The zinc salt-modified hexadecyl phosphate nano-silica was prepared by the following method: Zinc hexadecyl phosphate was added to anhydrous ethanol and heated in a water bath to obtain a ZHP dispersion. Dried nano-silica was added to anhydrous ethanol and heated in a water bath with stirring. Then, the ZHP dispersion was added dropwise with stirring. After the addition was complete, the mixture was kept warm and refluxed. After the reaction was completed, the solid product was separated, washed with anhydrous ethanol, and dried under vacuum to obtain zinc hexadecyl phosphate modified nano-silica. The reinforcing fiber is at least one of ceramic fiber, aramid fiber, and mineral fiber; The friction filler is selected from at least one of graphite, molybdenum disulfide, barium sulfate, zirconium oxide, alumina, zirconium silicate, or calcium carbonate; The rust-resistant and adhesive automotive friction material is prepared by the following method: The weighed phenolic resin, reinforcing fiber, friction filler, and functional filler are mixed together, and the resulting mixture is hot-pressed and then cured to obtain the friction material.

2. The anti-rust bonding friction material for automobiles according to claim 1, characterized in that, The phenolic resin is pure phenolic resin, cashew oil-modified phenolic resin, or boron-modified phenolic resin.

3. The anti-rust bonding friction material for automobiles according to claim 1, characterized in that, The mineral fibers are non-asbestos mineral fibers.

4. The anti-rust bonding friction material for automobiles according to claim 1, characterized in that, The mass ratio of zinc hexadecyl phosphate to nano silica is 1~3:10; the particle size of the nano silica is 10~40nm; and the dropping rate is 1~2mL / min.

5. The anti-rust bonding friction material for automobiles according to claim 1, characterized in that, The water bath heating temperature is 60~70℃; the reflux reaction time is 8~16h; the vacuum drying temperature is 60℃ and the time is 4~8h.

6. The anti-rust bonding friction material for automobiles according to claim 1, characterized in that, The hot pressing temperature is 150~170℃, the pressure is 20~30MPa, and the time is 5~15min; the curing temperature is 180℃ and the time is 6~8h.

7. The application of the anti-rust bonding friction material for automobiles according to any one of claims 1 to 6 in reducing rust adhesion between friction pads and brake discs.

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