A method for preparing a high-thermal-conductivity thermoplastic bearing sheet

Abstract

A method for preparing a high-thermal-conductivity thermoplastic bearing plate includes the following steps: providing a substrate; providing copper powder and forming a copper powder layer on the substrate; providing graphite columns; providing at least one glass fiber mesh coated with a thermal conductive layer; inserting a plurality of the graphite columns into the at least one glass fiber mesh; providing a thermoplastic composite material formed by mixing a thermoplastic material, PTFE, modified glass fiber coated with a thermal conductive layer, and copper-coated graphite; rolling and fusing the thermoplastic composite material on the surface of the copper powder layer to form a bonding layer; placing the modified glass fiber mesh on the thermoplastic material layer; and performing injection molding to obtain the thermoplastic bearing plate. The thermoplastic bearing plate prepared by the method has good processing and physical properties, and also has good heat dissipation performance.

Description

Technical Field

[0001] This invention relates to the field of bearing material production technology, and in particular to a method for preparing a high thermal conductivity thermoplastic bearing plate. Background Technology

[0002] Thermoplastic materials, such as PA, PEEK, and their mixtures, are widely used in engineering machinery, automotive manufacturing, electrical appliances, and medical manufacturing due to their excellent processing performance, good physical properties, weather resistance, lubricity, wear resistance, fatigue resistance, temperature resistance, and recyclability. However, thermoplastic materials generally have poor thermal conductivity, mainly because their molecular structure is not dense enough, with large gaps between molecules, making it difficult for heat to be conducted away quickly. Therefore, heat dissipation problems may occur when using thermoplastic materials, especially when they are used as friction components, as they have difficulty quickly conducting away the heat generated by friction during use, leading to problems such as equipment overheating.

[0003] Furthermore, in certain specialized applications, such as precision engineering machinery and wind power, including bearings for wind turbine main shafts, the materials need to possess a certain degree of elasticity to withstand potential impacts. Therefore, the thickness of the thermoplastic material layer is crucial, often exceeding 5mm. In such cases, if the thermoplastic material has poor thermal conductivity, heat can easily accumulate during use, rapidly increasing the temperature of the friction surface and thus the severity of the friction environment. Prolonged operation in such a harsh environment can easily lead to failures such as shaft seizure or locking due to excessive temperature, which is unacceptable in applications like wind turbine main shafts.

[0004] Therefore, how to ensure the original material's lubrication performance, friction and wear resistance, and impact and anti-galling performance while also possessing good thermal conductivity and noise reduction performance is a major challenge in this field. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing a high thermal conductivity thermoplastic bearing plate that can solve the above-mentioned technical problems.

[0006] A method for preparing a high thermal conductivity thermoplastic bearing plate includes the following steps:

[0007] STEP101: Provide a substrate;

[0008] STEP102: Provide copper powder and sinter the copper powder onto the substrate to form a copper powder layer;

[0009] STEP103: Provides a graphite column, which is frustoconical in shape, with an axial length of 6mm to 10mm, a diameter of 4mm to 6mm at the large diameter end, and a diameter of 0.5mm to 1.5mm at the small diameter end;

[0010] STEP104: Provide at least one layer of glass fiber mesh, modify the glass fiber mesh to obtain a modified glass fiber mesh with thermal conductivity, wherein a thermally conductive layer is coated on the glass fiber mesh of the modified glass fiber mesh;

[0011] STEP 105: Insert the plurality of graphite pillars onto at least one layer of the modified glass fiber mesh;

[0012] STEP106: Provide a thermoplastic composite material, which is composed of thermoplastic material, PTFE, modified glass fiber, and copper-plated graphite, wherein, per 100 parts, the thermoplastic material accounts for 50-70 parts, the PTFE accounts for 5-15 parts, the modified glass fiber accounts for 20-30 parts, and the copper-plated graphite accounts for 5-10 parts, wherein the modified glass fiber is coated with a thermally conductive layer;

[0013] STEP107: Roll a layer of the thermoplastic composite material onto the surface of the sintered copper powder layer, and heat the rolled sheet until the thermoplastic material in the thermoplastic composite material melts to form an adhesive layer;

[0014] STEP 108: Place the modified glass fiber mesh with the graphite pillars inserted onto the thermoplastic material layer, and cool the graphite pillars after they are inserted into the thermoplastic composite material to form the core layer.

[0015] STEP109: Provide an injection molding machine and place the assembled core layer and substrate together into the injection molding machine for injection molding to obtain the thermoplastic bearing sheet.

[0016] Furthermore, in STEP 104, the fiberglass mesh has three layers, and the three layers of the fiberglass mesh have different mesh sizes.

[0017] Furthermore, in STEP 105, when multiple layers of the glass fiber mesh are present, the mesh size of the glass fiber mesh near the large-diameter end of the graphite column is 5000-6000 μm, the mesh size of the glass fiber mesh in the middle layer is 3000-4000 μm, and the mesh size of the glass fiber mesh near the small-diameter end of the graphite column is 1000-2000 μm.

[0018] Furthermore, the axial direction of the graphite column is perpendicular to the arrangement direction of the multilayer glass fiber mesh.

[0019] Furthermore, the preparation of the modified glass fiber includes the following steps:

[0020] STEP201: Immerse the glass fiber in hydrofluoric acid with a concentration of 0.5-5% to corrode it so that pores appear on the surface of the glass fiber;

[0021] STEP202: Clean and dry the etched glass fibers;

[0022] STEP203: Place the glass fiber into a high-speed mixer containing nano copper powder and mix it with the nano copper powder at high speed. During the mixing process, the nano copper powder and the glass fiber collide at high speed so that the nano copper powder is embedded in the pores formed by corrosion of the glass fiber to coat the glass fiber mesh with a thermally conductive layer.

[0023] Furthermore, in preparing the modified glass fiber, the mixing ratio of the nano-copper powder to the glass fiber is 2-5:1, and the stirring time is 20-30 minutes.

[0024] Furthermore, the concentration of the hydrofluoric acid is 2%.

[0025] Furthermore, the nano-copper powder is uniformly distributed onto the glass fiber surface of the glass fiber mesh under the action of wind shearing.

[0026] Furthermore, in STEP107, the thickness of the adhesive layer is between 1 mm and 2 mm.

[0027] Furthermore, in STEP 108, the axial direction of the graphite pillar is perpendicular to the substrate.

[0028] Compared with the prior art, the method for preparing high thermal conductivity thermoplastic bearing plates provided by the present invention produces thermoplastic bearing plates by adding copper-plated glass fibers to thermoplastic materials, which gives the thermoplastic composite material sufficient thermal conductivity. At the same time, a modified glass fiber mesh is added to the injection-molded thermoplastic composite material, and the glass fibers of the modified glass fiber mesh are also plated with copper powder, thereby forming a thermally conductive network with the copper-plated graphite and copper-plated glass fibers in the thermoplastic composite material. Even if the non-metallic layer containing thermoplastic materials reaches more than 5 mm, it still has a good thermal conductivity. Therefore, the bearing bush or bearing made from the thermoplastic bearing plate not only has good processing performance and physical properties, but also good heat dissipation performance, making it suitable for use in relatively harsh applications. Simultaneously, the upright graphite pillars inserted during the preparation process not only support and space the multiple layers of modified glass fiber mesh, allowing the thermoplastic composite material to fill between the multiple layers of the modified glass fiber mesh during injection molding, but also, because they are perpendicular to the surface of use, allow for observation of the wear mark width on the surface of the grinding shaft during maintenance. This enables the determination of the service condition and remaining life of the bearing bush or bearing made from the thermoplastic bearing plate, achieving timely replacement while ensuring full utilization and avoiding waste. Detailed Implementation

[0029] The following detailed description of specific embodiments of the present invention is based on the accompanying drawings. It should be understood that the description of the embodiments of the present invention herein is not intended to limit the scope of protection of the present invention.

[0030] This invention provides a method for preparing a high thermal conductivity thermoplastic bearing plate, which includes the following steps:

[0031] STEP101: Provide a substrate;

[0032] STEP102: Provide copper powder and sinter the copper powder onto the substrate to form a copper powder layer;

[0033] STEP103: Provides a graphite column, which is frustoconical in shape, with an axial length of 6mm to 10mm, a diameter of 4mm to 6mm at the large diameter end, and a diameter of 0.5mm to 1.5mm at the small diameter end;

[0034] STEP104: Provide at least one layer of glass fiber mesh, modify the glass fiber mesh to obtain a modified glass fiber mesh with thermal conductivity, wherein the glass fibers of the modified glass fiber mesh are coated with a thermally conductive layer.

[0035] STEP 105: Insert a plurality of the graphite pillars onto at least one layer of the modified glass fiber mesh;

[0036] STEP106: Provide a thermoplastic composite material, which is composed of thermoplastic material, PTFE, modified glass fiber, and copper-plated graphite, wherein, per 100 parts, the thermoplastic material accounts for 50-70 parts, the PTFE accounts for 5-15 parts, the modified glass fiber accounts for 20-30 parts, and the copper-plated graphite accounts for 5-10 parts, wherein the modified glass fiber is coated with a thermally conductive layer;

[0037] STEP107: Roll a layer of the thermoplastic composite material onto the surface of the sintered copper powder layer, and heat the rolled sheet until the thermoplastic material in the thermoplastic composite material melts to form an adhesive layer;

[0038] STEP 108: Place the modified glass fiber mesh with the graphite pillars inserted onto the thermoplastic material layer, and cool the graphite pillars after they are inserted into the thermoplastic composite material to form the core layer.

[0039] STEP109: Provide an injection molding machine and place the assembled core layer and substrate together into the injection molding machine for injection molding to obtain the thermoplastic bearing sheet.

[0040] In step STEP 101, the substrate can be one of a copper plate, a steel plate, a carbon steel plate, a stainless steel plate, or an aluminum plate. In this embodiment, the substrate is a steel plate, and its thickness can be determined according to actual needs.

[0041] In step STEP 102, the copper powder layer is formed by laying copper powder. The copper powder can be made of brass, copper, bronze, or cupronickel. Preferably, the copper powder is made of pure copper powder. The particle size of the copper powder is 0.013 mm to 0.045 mm. The shape of the copper powder is non-spherical or irregular. The purpose of using irregularly shaped copper powder is to increase the contact area, not only to increase the contact area or contact points between the copper powder and the substrate, but also to increase the contact area or contact points between the copper powder and the modified glass fiber mesh, so as to improve the bonding strength between the copper powder and the substrate and the bonding strength between the copper powder and the modified glass fiber mesh after sintering. Therefore, the particle size of the copper powder should be related to its content; the higher the content, the smaller the particle size should be, and vice versa. In this embodiment, the particle size of the copper powder is 0.013 mm to 0.045 mm. Preferably, the particle size of the copper powder is 0.017 mm.

[0042] In step STEP102, the process of sintering copper powder on the substrate should be existing technology and will not be described in detail here.

[0043] In step STEP 103, the graphite column is frustoconical in shape. Using this graphite column achieves lubrication and allows for wear monitoring. The smaller diameter end of the graphite rod, wider at the bottom than the top, faces the bearing's service side. During use, the wear of the bearing can be determined by measuring the width of the wear marks on the bearing surface or by the diameter of the exposed graphite rod, thus determining the bearing's remaining lifespan and replacement time. This helps ensure the normal operation of the equipment. It is understood that the central axis of the graphite column should be perpendicular to the bearing's contact surface. The axial length of the graphite column is 6mm–10mm, the diameter of the larger diameter end is 4mm–6mm, and the diameter of the smaller diameter end is 0.5mm–1.5mm. When the modified glass fiber mesh has multiple layers, the diameter of the graphite column can be varied to create intervals in the multi-layer modified glass fiber mesh, thereby forming heat transfer channels.

[0044] In step STEP 104, when modifying the glass fiber mesh, the specific modification method should be the same as that for modifying the glass fiber, which will be described in detail later.

[0045] In step STEP 105, the graphite pillars can be inserted into the modified glass fiber mesh manually or using tooling. The central axis of the graphite pillar should be perpendicular to the plane of the modified glass fiber mesh. The modified glass fiber mesh can be a single layer or multiple layers. When multiple layers are used, the bottommost mesh, i.e., the one closest to the large-diameter end of the graphite pillar, has a size of 5000-6000 μm; the middle layers have a mesh size of 3000-4000 μm; and the layers closest to the small-diameter end of the graphite pillar have a mesh size of 1000-2000 μm. It is conceivable that when using multiple layers, each graphite pillar should pass through multiple layers of the glass fiber mesh and be kept upright. Because the graphite pillars used for positioning are shaped with a smaller top and a larger bottom, by setting the mesh size of the modified glass fiber mesh, the fiber mesh of the modified glass fiber mesh can be easily fixed at different diameters of the graphite pillar, thus allowing multiple layers of the modified glass fiber mesh to be spaced apart. Meanwhile, the grid distribution with smaller meshes at the top and larger meshes at the bottom allows the thermoplastic material to fill the entire space more quickly during injection molding. Because thermoplastic materials such as PA and PEEK are high-molecular polymers with fast crystallization rates and poor flowability, they are prone to defects such as air bubbles, voids, and localized material shortages during injection molding due to their poor flowability. The smaller the grid size, the greater the resistance to material flow. Therefore, the grid size of the modified glass fiber mesh should be no less than 1000 μm. Specifically, in this embodiment, the bottom layer, near the large-diameter end of the graphite pillar, has a grid size of 4000 μm; the middle layer of the modified glass fiber mesh has a grid size of 2000 μm; and the top layer, near the small-diameter end of the graphite pillar, has a grid size of 1000 μm.

[0046] In STEP106, the thermoplastic material can be one or a mixture of several of polyethylene (PE), polyvinylidene fluoride (PVDF), polyphenylene sulfide (PPS), polyoxymethylene (POM), polyimide (PI), polyamide (PA), and polyetheretherketone (PEEK). The thermoplastic material itself is prior art, and its properties and preparation methods are also prior art, and will not be elaborated here. PTFE, or polytetrachloroethylene, is a wear-resistant material, which is prior art. The copper-plated graphite is also prior art, and can be provided by Nangong Jinno Welding Materials Co., Ltd. The modified glass fiber is mainly used to improve thermal conductivity. Although glass fiber has compressive strength, impact strength, and deformation resistance, its thermal conductivity is poor. Therefore, to improve the thermal conductivity of the glass fiber, a metal material is plated on its outer surface. The metal material plated on the outer surface of the glass fiber can be copper, nickel, or other materials with good thermal conductivity, to achieve the purpose of modification. Because the material prepared by this invention is mainly used in sliding bearings or bushings, as well as wind turbine main shafts, etc., the material should primarily focus on friction reduction and wear resistance. Therefore, while maintaining its original friction and wear resistance, it should also achieve better thermal conductivity. Consequently, the PTFE content should be between 5 and 15 parts. If it is too low, the friction reduction effect will be poor; if it is too high, it will affect the overall wear resistance of the material. The modified glass fiber content should be between 20 and 30 parts. If it is too low, a uniform, integral thermally conductive structure cannot be formed in the thermoplastic material, and the wear resistance of the material will be reduced. If the modified glass fiber content is too high, it will affect the friction reduction effect of the thermoplastic material layer and increase the coefficient of friction. The copper-plated graphite is a supplement to the friction reduction, lubrication, and thermal conductivity system of the prepared thermoplastic composite material. Copper-plated graphite can work synergistically with PTFE to achieve lubrication and friction reduction. On the other hand, copper-plated graphite can also form an integral thermally conductive structure with modified glass fiber, thereby improving the thermal conductivity.

[0047] It should be noted that the modified glass fiber and the glass fiber mesh can be modified using the same method. The following description uses the modified glass fiber as an example to illustrate the method for modifying the glass fiber and the glass fiber mesh.

[0048] The following steps are performed when preparing the modified glass fiber:

[0049] STEP201: First, immerse the glass fiber in hydrofluoric acid with a concentration of 0.5% to 5% to etch it so that pores appear on the surface of the glass fiber.

[0050] STEP202: After etching is complete, the glass fiber is cleaned and dried;

[0051] STEP203: Place the glass fiber into a high-speed mixer containing nano-copper powder and mix it with the nano-copper powder at high speed. During the mixing process, the nano-copper powder and glass fiber collide at high speed. At the same time, the nano-copper powder is evenly distributed on the surface of the glass fiber mesh under the action of wind shearing, so that the nano-copper powder is embedded in the pores formed by corrosion of the glass fiber and is also distributed on the surface of the glass fiber. The mixing ratio of nano-copper powder to glass fiber is 2-5:1, and the mixing time is generally 20-30 minutes.

[0052] In STEP201, the concentration of hydrofluoric acid is 0.5% to 2%, preferably 2%. The soaking time is 5 to 10 minutes. If the concentration of hydrofluoric acid is below 0.5%, the longer the soaking time, the lower the production efficiency. If the concentration is above 2%, it is difficult to control the soaking time, which can easily cause the glass fiber to dissolve completely. Therefore, controlling the concentration of hydrofluoric acid and the soaking time within a reasonable range is necessary to achieve optimal corrosion of the glass fiber. Simultaneously, the soaking time should be limited to between 5 and 10 minutes. Excessive soaking time will cause the glass fiber to dissolve, while insufficient soaking time will prevent effective corrosion of the glass fiber surface to form pores that can accommodate the nano-copper powder.

[0053] In STEP202, water can be used to clean the glass fiber. After cleaning, it can be placed in a high-frequency drying oven for drying.

[0054] In STEP203, the nano-copper powder is widely used in conductive adhesives, conductive coatings, and electrode materials. However, in this invention, it is used to give the glass fiber a thermally conductive function. By high-speed mixing in a high-speed mixer, the nano-copper powder is forcefully impacted by the glass fibers, causing it to embed into the pores of the glass fibers. Simultaneously, under the influence of intermolecular forces, the nano-copper powder also adheres to the surface of the glass fibers. Furthermore, the nano-copper powder can be uniformly distributed on the surface of the glass fibers under the action of air shearing. Through these three methods, the nano-copper powder can be uniformly adhered to the surface of the glass fibers, thereby forming a thermally conductive layer on the surface of the glass fibers, thus modifying the glass fibers and improving their thermal conductivity. To ensure that the nano-copper powder is fully embedded in the pores of the glass fibers and adheres to the surface of the glass fibers, the mixing ratio of nano-copper powder to glass fibers should be limited to 2–5:1. If the content of nano-copper powder is too high, such as greater than 5%, it will not only be wasteful, but also cause the nano-copper powder to clump together due to excessive molecular forces, making it difficult to fully disperse and embed itself into the pores of the glass fiber, and even more difficult to adhere to the surface of the glass fiber, thus weakening the thermal conductivity of the glass fiber. The content of nano-copper powder also cannot be too low; if it is too low, it will be difficult to fully cover the glass fiber, i.e., insufficient amount, which will also lead to weakened thermal conductivity of the glass fiber.

[0055] It is understandable that glass fiber mesh is not suitable for stirring with a propeller due to its mesh structure. Therefore, the glass fiber mesh can be suspended in a high-speed mixer, and then nano copper powder is added and stirred at high speed. This allows a thermally conductive layer to be formed on the surface of the glass fibers in the glass fiber mesh, thereby forming the modified glass mesh and improving its thermal conductivity.

[0056] In STEP 107, the thermoplastic composite material prepared in STEP 106 is laid on the copper powder layer by hot rolling to form an adhesive layer. The thickness of this adhesive layer is between 1mm and 2mm. If the thickness is too small, there is a risk to fixing the graphite column; if the thickness is too large, it will be difficult to lay the modified fiber mesh connected to the adhesive layer. Since the adhesive layer only serves an adhesive function, it should reserve as much space as possible for laying the modified glass fiber mesh, because the more layers of modified glass fiber mesh, the better the thermal conductivity. At the same time, the total thickness of the prepared bearing plate is fixed. If the total thickness of the thermoplastic material layer is 10mm, and the thickness of the adhesive layer reaches 5mm, then only one layer of glass fiber mesh may be able to be placed in the remaining 5mm, which is not conducive to the thermal conductivity of the thermoplastic composite material layer. Therefore, the thickness of the adhesive layer cannot be too thick.

[0057] In STEP 108, when placing the modified glass fiber mesh with the inserted graphite pillars, each graphite pillar should be positioned vertically, i.e., perpendicular to the substrate. It is understood that, to achieve this perpendicularity, a tooling can be used to first position each graphite pillar vertically before placing it on the adhesive layer. After cooling, the core layer can be formed.

[0058] In STEP 109, the thermoplastic composite material is injection molded so that it can fill the gaps in the modified glass fiber mesh. The specific injection molding process is prior art and will not be described further here. Injection molding produces a thermally conductive thermoplastic bearing sheet. The injection molding material is also the aforementioned thermoplastic composite material.

[0059] Compared with the prior art, the method for preparing high thermal conductivity thermoplastic bearing plates provided by the present invention produces thermoplastic bearing plates by adding copper-plated glass fibers to thermoplastic materials, which gives the thermoplastic composite material sufficient thermal conductivity. At the same time, a modified glass fiber mesh is added to the injection-molded thermoplastic composite material, and the glass fibers of the modified glass fiber mesh are also plated with copper powder, thereby forming a thermally conductive network with the copper-plated graphite and copper-plated glass fibers in the thermoplastic composite material. Even if the non-metallic layer containing thermoplastic materials reaches more than 5 mm, it still has a good thermal conductivity. Therefore, the bearing bush or bearing made from the thermoplastic bearing plate not only has good processing performance and physical properties, but also good heat dissipation performance, making it suitable for use in relatively harsh applications. Meanwhile, the upright graphite column inserted during the preparation process not only supports and spaces the multiple layers of modified glass fiber mesh, allowing the thermoplastic composite material to fill between the multiple layers of the modified glass fiber mesh during injection molding, but also, because it is perpendicular to the surface of use, allows for observation of the usage status and remaining life of the bearing bush or bearing made from the thermoplastic bearing plate during maintenance, enabling timely replacement while ensuring full utilization and avoiding waste.

[0060] Experimental data

[0061] In the experiments, the main formulations of the examples and comparative examples were the same, both being thermoplastic materials, namely, 70% polyetheretherketone, 15% PTFE, 10% glass fiber (or modified glass fiber), and 5% copper-plated graphite.

[0062] Except for Example 6, the pore sizes of the three layers of glass fiber mesh in the other comparative examples and examples are 1000 μm, 2000 μm, and 4000 μm from top to bottom, respectively, while the pore sizes of the three layers of glass fiber mesh in Example 6 are 4000 μm, 2000 μm, and 1000 μm from top to bottom, respectively.

[0063] Table 1. Composition and filling materials of the examples and comparative examples

[0064]

[0065] It should be noted that, in order to fully illustrate the performance of the bearing plate prepared by the present invention, in Example 5, unmodified "ordinary glass fiber" was specifically used to compare with the bearing plate using "modified glass fiber" to demonstrate the superiority of using both "modified glass fiber" and "modified glass fiber mesh" in the present invention.

[0066] First, a compressive strength test was conducted, comparing the examples with comparative examples to illustrate the relationship between compressive strength and the filling ratio of the modified fiber mesh. As is well known, a higher filling ratio results in stronger compressive strength.

[0067] The test specimen for compression deformation resistance is 20 x 20 x 13 mm (13 is the thickness), the load is 150 MPa, the holding time is 15 seconds, and the difference in wall thickness before and after the test is the amount of compression deformation. It is worth noting that after the holding time is completed, the specimen should be left to stand for 1 hour before the wall thickness is measured to avoid the springback of the material affecting the final test data.

[0068] Table 2. Test results of compressive deformation with different contents of modified glass fiber mesh and without glass fiber mesh.

[0069]

[0070] As shown in Table 2, the addition of the modified glass fiber mesh filler to the thermoplastic material layer significantly improved the overall compressive strength of the product. This demonstrates that filling with glass fiber mesh can significantly enhance the compressive strength of the material, and the higher the filler ratio, the better the compressive strength, thereby further improving the overall load-bearing capacity of the material and broadening the product's application scope.

[0071] Secondly, the injection molding yield was tested. Specifically, the influence of the arrangement of glass fiber mesh with a larger top and a smaller bottom versus a smaller top and a larger bottom on the injection molding yield was illustrated through a comparison between the examples.

[0072] Meanwhile, the formulations used in Examples 3 and 6 in Table 3 are identical, and both the fibers and fiber webs have been modified. The injection molding defect rate was mainly due to defects such as bubbles appearing in the plastic layer.

[0073] Table 3. Injection Molding Defect Rate Test Table with Different Grid Arrangement Methods

[0074]

[0075] The data above shows that a grid layout with smaller pores at the top and larger pores at the bottom results in a lower defect rate. This is mainly because most thermoplastic materials have poor flowability and rapid crystallization. During injection molding, when encountering glass fiber mesh, their flowability drops rapidly, leading to voids at the bottom and defects. When the grid is arranged with smaller pores at the top and larger pores at the bottom, the thermoplastic material, with its relatively low crystallinity, has good flowability and can pass through the smaller pores relatively easily. As crystallinity increases and flowability decreases, the larger pores pass through more easily. Conversely, when the thermoplastic material's crystallinity increases and flowability decreases, it is difficult to pass through the smaller pores, resulting in a higher product defect rate.

[0076] Finally, thermal conductivity tests were conducted. Through comparisons of the examples and comparative examples, as well as between the examples themselves, the ability of modified glass fiber and modified glass fiber mesh to improve thermal conductivity was demonstrated. Ultimately, this resulted in better thermal conductivity in the thermoplastic material layer, leading to more stable and reliable performance during friction and wear, without affecting the original lubrication properties of the thermoplastic material.

[0077] The test method was an end face test. The sample size was 37 x 37 x 12 (unit: mm, 12 is the thickness). The test load was 20 MPa, the test speed was 0.2 m / s, the test time was 3 h, and the lubrication condition was initial grease lubrication. The coefficient of friction, the final temperature, and the wear of the sample were tested during the test.

[0078] Table 4 lists the test results of thermal conductivity and wear amount for the above embodiments and comparative examples.

[0079]

[0080] From Table 4, firstly, based on the experimental data of Comparative Examples 1, 2, 3, and 4, it can be seen that the addition of ordinary unmodified glass fiber mesh has a certain impact on thermal conductivity, because glass fiber mesh has better thermal conductivity than thermoplastic materials, but there is no particularly significant improvement.

[0081] Comparing Comparative Example 2 with Example 1, Comparative Example 3 with Example 2, and Comparative Example 4 with Example 3, it can be seen that, with the same number of glass fiber mesh layers, the test temperature is significantly improved after the glass fibers and glass fiber mesh are modified for thermal conductivity. This indicates that the modification of the thermal conductivity of glass fibers and glass fiber mesh is very helpful in effectively conducting the heat generated during the friction test and further reducing the test temperature.

[0082] As is well known, excessively high test temperatures can adversely affect the friction environment, especially for polymer materials, as high temperatures can cause them to deform or even soften. Unlike metals, polymer materials begin to move when the temperature exceeds their thermal conductivity (Tg), leading to changes in their properties and increasing the risk of failure. Therefore, test temperature is crucial, as it reflects the material's thermal conductivity.

[0083] Comparing Example 4 and Example 5, Example 4 added modified glass fiber but used ordinary glass fiber mesh, while Example 5 added modified glass fiber mesh but used ordinary glass fiber. It can be seen that the modified glass fiber mesh achieves better thermal conductivity than the modified glass fiber itself. This is because the modified glass fiber mesh can form relatively fixed heat transfer channels, thereby quickly and effectively transferring heat away from the friction surface.

[0084] Comparative Examples 4 and 5 were compared with Example 3, where both modified glass fibers and modified glass fiber mesh were added. It can be seen that adding modified glass fibers and glass fiber mesh can form a very effective three-dimensional heat-conducting network structure, which has significant advantages compared to using modified glass fibers or glass fiber mesh alone.

[0085] Finally, when comparing the wear amount, it was unexpectedly found that the addition of modified glass fiber also resulted in an unforeseen improvement in wear resistance. Table 4 shows that the addition of modified glass fiber improves the wear resistance of the material. Furthermore, metallographic and energy dispersive spectroscopy (EDS) analyses of the material surface after the experiment revealed that the friction surface of the test piece was smooth, flat, and glossy. EDS analysis showed the presence of a uniformly mixed substance on this surface, primarily composed of PTFE and nano-copper powder. Analysis concluded that during the friction process, PTFE and nano-copper powder form a very uniform mixture on the material surface, existing as a film between the grinding and testing parts. The PTFE and nano-copper powder not only act as lubricants, but also, through the synergistic effect of the nano-copper powder, enhance the material's load-bearing capacity and further improve its wear resistance. This is mainly because the presence of nano-copper powder in the formed transfer film makes this lubricating transfer film stronger than the transfer film of thermoplastic material + PTFE structure, resulting in better load-bearing capacity and stability, making it less prone to damage, and further reducing the risk of material seizing with the grinding shaft. Energy dispersive spectroscopy analysis of the grinding part surface clearly detected F element representing PTFE material and Cu element representing nano-copper powder, further confirming the above theoretical basis and indirectly demonstrating the effectiveness of nano-copper powder in modifying glass fiber.

[0086] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions or improvements within the spirit of the present invention are covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a high thermal conductivity thermoplastic bearing plate, comprising the following steps: STEP101: Provide a substrate; STEP102: Provide copper powder and sinter the copper powder onto the substrate to form a copper powder layer; STEP103: Provides a graphite column, which is frustoconical in shape, with an axial length of 6mm to 10mm, a diameter of 4mm to 6mm at the large diameter end, and a diameter of 0.5mm to 1.5mm at the small diameter end; STEP104: Provide at least one layer of glass fiber mesh, modify the glass fiber mesh to obtain a modified glass fiber mesh with thermal conductivity, wherein a thermally conductive layer is coated on the glass fiber mesh of the modified glass fiber mesh; STEP 105: Insert the plurality of graphite pillars onto at least one layer of the modified glass fiber mesh; STEP106: Provide a thermoplastic composite material, which is composed of thermoplastic material, PTFE, modified glass fiber, and copper-plated graphite, wherein, per 100 parts, the thermoplastic material accounts for 50-70 parts, the PTFE accounts for 5-15 parts, the modified glass fiber accounts for 20-30 parts, and the copper-plated graphite accounts for 5-10 parts, wherein the modified glass fiber is coated with a thermally conductive layer; STEP107: Roll a layer of the thermoplastic composite material onto the surface of the sintered copper powder layer, and heat the rolled sheet until the thermoplastic material in the thermoplastic composite material melts to form an adhesive layer; STEP 108: Place the modified glass fiber mesh with the graphite pillars inserted onto the thermoplastic material layer, and cool the graphite pillars after they are inserted into the thermoplastic composite material to form the core layer. STEP109: Provide an injection molding machine and place the assembled core layer and substrate together into the injection molding machine for injection molding to obtain the thermoplastic bearing sheet.

2. The method for preparing the high thermal conductivity thermoplastic bearing plate as described in claim 1, characterized in that: In STEP104, the fiberglass mesh has three layers, and the three layers of fiberglass mesh have different mesh sizes.

3. The method for preparing the high thermal conductivity thermoplastic bearing plate as described in claim 1, characterized in that: In STEP105, when multiple layers of the glass fiber mesh are present, the mesh size of the glass fiber mesh near the large-diameter end of the graphite column is 5000-6000 μm, the mesh size of the glass fiber mesh in the middle layer is 3000-4000 μm, and the mesh size of the glass fiber mesh near the small-diameter end of the graphite column is 1000-2000 μm.

4. The method for preparing the high thermal conductivity thermoplastic bearing plate as described in claim 3, characterized in that: The axial direction of the graphite column is perpendicular to the arrangement direction of the multiple layers of glass fiber mesh.

5. The method for preparing the high thermal conductivity thermoplastic bearing plate as described in claim 1, characterized in that: The preparation of the modified glass fiber includes the following steps: STEP201: Immerse the glass fiber in hydrofluoric acid with a concentration of 0.5-5% to corrode it so that pores appear on the surface of the glass fiber; STEP202: Clean and dry the etched glass fibers; STEP203: Place the glass fiber into a high-speed mixer containing nano copper powder and mix it with the nano copper powder at high speed. During the mixing process, the nano copper powder and the glass fiber collide at high speed so that the nano copper powder is embedded in the pores formed by corrosion of the glass fiber to coat the glass fiber mesh with a thermally conductive layer.

6. The method for preparing the high thermal conductivity thermoplastic bearing plate as described in claim 5, characterized in that: In preparing the modified glass fiber, the mixing ratio of the nano-copper powder to the glass fiber is 2-5:1, and the stirring time is 20-30 minutes.

7. The method for preparing the high thermal conductivity thermoplastic bearing plate as described in claim 5, characterized in that: The concentration of the hydrofluoric acid is 2%.

8. The method for preparing the high thermal conductivity thermoplastic bearing plate as described in claim 5, characterized in that: The nano-copper powder is evenly distributed onto the glass fiber surface of the glass fiber mesh under the action of wind shearing.

9. The method for preparing the high thermal conductivity thermoplastic bearing plate as described in claim 1, characterized in that: In STEP107, the thickness of the adhesive layer is between 1 mm and 2 mm.

10. The method for preparing the high thermal conductivity thermoplastic bearing plate as described in claim 1, characterized in that: In STEP108, the axis of the graphite pillar is perpendicular to the substrate.

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