A PA66 / PPE alloy material for wear discs of railway freight car center plates, its preparation method and application

Abstract

This invention discloses a PA66 / PPE alloy material composition for railway freight car core disc wear plates and the PA66 / PPE alloy material prepared therefrom, as well as a railway freight car core disc wear plate and its preparation method. The PA66 / PPE alloy material composition of this invention comprises the following components in parts by weight: 20-80 parts PA66 (Nylon 66), 20-80 parts PPE (polyphenylene ether), 10-30 parts compatibilizer, 2-15 parts lubricant, 0.2-1.0 parts antioxidant, 0.1-0.5 parts coupling agent, and 5-30 parts inorganic filler; wherein the total weight of PA66 and PPE is 100 parts; and the average particle size of the inorganic filler is 40-100 nm. The PA66 / PPE alloy material of this invention possesses excellent mechanical properties, wear resistance, dimensional stability, thermal stability, and environmental adaptability. When used in railway freight car core disc wear plates, it can significantly improve the service life and operational safety of the wear plates.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to an alloy material including polyamides and polyphenylene ethers, its preparation method, and its application. Background Technology

[0002] The center plate wear plate (or center plate wear plate) is a key component of the railway vehicle bogie system. Installed in the middle of the bogie bolster, it works in conjunction with the upper and lower center plates, and together with the side bearings, supports the entire car body. It bears the vertical loads and longitudinal impact loads during train operation, and withstands the relative rotational friction and impact between the two when the vehicle passes through curves. Therefore, the mechanical properties, wear resistance, and dimensional stability of the center plate wear plate material directly affect the safety and service life of the vehicle. Currently, non-metallic composite material center plate wear plates are the mainstream. For example, the industry standard TB / T3270-2020 "Railway Vehicle Center Plates and Wear Plates" specifies that center plate wear plates should be made of nylon material (such as PA6). Currently, railway freight car center plate wear plates are mainly manufactured using a casting molding process, with caprolactam as the matrix material, where caprolactam, catalysts, and other raw materials are directly polymerized and molded within a mold. Although this method is simple, it is an intermittent production process with low production efficiency and poor environmental performance. More importantly, the product is prone to casting defects such as porosity, shrinkage, and cracks, which cause its mechanical properties to fail to meet the design requirements.

[0003] To improve the performance of the core plate wear plate and adapt it to harsh environments such as heavy-load, high-speed, high-altitude, and frigid regions in railways, improvements have been made to the non-metallic composite materials and manufacturing processes used in core plate wear plates in the prior art. For example, Chinese invention patent application CN113717516A (publication date November 30, 2021), entitled "A Composite Material for Core Plate Wear Plate and Core Plate Wear Plate and Its Preparation Method," discloses a composite material reinforced with polytetrafluoroethylene fiber and / or ultra-high molecular weight polyethylene fiber for casting to manufacture core plate wear plates. Another example is Chinese invention patent application CN107606208A (publication date January 19, 2018), entitled "A Preparation Method of Graphene / Nylon Reinforced and Toughened Composite Material for Railway Freight Car Core Plate Wear Plate," which discloses a graphene / nylon 6 reinforced and toughened composite material prepared by extrusion granulation using a twin-screw extruder. This composite material is then used to manufacture railway freight car core plate wear plates through injection molding.

[0004] There have also been attempts in this field to replace PA6 with other engineering plastics. Among them, PA46 (poly(dibutylene adipamide)) has attracted attention due to its excellent overall performance. However, the price of special nylon grades of PA46 is too high, and it was withdrawn from the railway market after being used in the wear discs of the mandrel for a period of time.

[0005] Therefore, there is an urgent need to develop a new type of core disc wear disc material that combines excellent mechanical properties, wear resistance, dimensional stability, and thermal stability. At the same time, this material should have efficient and stable injection molding adaptability and a reasonable cost level to overcome the shortcomings of existing cast PA6 materials, such as low production efficiency, lack of environmental protection, and unstable performance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a PA66 / PPE alloy material for railway freight car core plate wear discs, its preparation method, and its application in the preparation of railway freight car core plate wear discs. Furthermore, this invention also provides a railway freight car core plate wear disc with a novel raw material formulation. The PA66 / PPE alloy material of this invention possesses excellent mechanical properties, wear resistance, dimensional stability, thermal stability, and environmental adaptability. When used in railway freight car core plate wear discs, it can significantly improve the service life and operational safety of the wear discs.

[0007] Therefore, in a first aspect, the present invention provides a PA66 / PPE alloy material composition for wear discs of railway freight car cores, comprising the following components in parts by weight:

[0008] 20-80 parts PA66 (Nylon 66), 20-80 parts PPE (Polyphenylene oxide), 10-30 parts compatibilizer, 2-15 parts lubricant, 0.2-1.0 parts antioxidant, 0.1-0.5 parts coupling agent, 5-30 parts inorganic filler;

[0009] The total weight of PA66 and PPE is 100 parts; the average particle size of the inorganic filler is 40-100 nm.

[0010] As a preferred embodiment, the present invention provides a PA66 / PPE alloy material composition for wear discs of railway freight car cores, comprising the following components in parts by weight:

[0011] 20-50 parts PA66 (Nylon 66), 50-80 parts PPE (Polyphenylene oxide), 20-30 parts compatibilizer, 8-15 parts lubricant, 0.4-0.6 parts antioxidant, 0.1-0.2 parts coupling agent, 5-15 parts inorganic filler;

[0012] The total weight of PA66 and PPE is 100 parts; the average particle size of the inorganic filler is 40-100 nm.

[0013] Preferably, the relative viscosity of PA66 is 2.0 to 4.5, more preferably 2.5 to 3.0.

[0014] Preferably, the intrinsic viscosity of the PPE is 20–80 dL / g, more preferably 30–50 dL / g.

[0015] The relative viscosity of PA66 in this invention is determined according to the method specified in GB / T 12006.1-2009 "Plastics - Polyamide - Part 1: Determination of Viscosity Number"; the intrinsic viscosity of PPE is determined according to the method specified in GB / T 41874-2022 "Plastics - Polyphenylene Ether (PPE) Resin".

[0016] Preferably, the inorganic filler is selected from one or two of talc powder and nano-calcium carbonate in any proportion.

[0017] More preferably, the inorganic filler is nano-calcium carbonate.

[0018] Preferably, the coupling agent is selected from one or more of titanate coupling agents and silane coupling agents in any proportion.

[0019] More preferably, the titanate coupling agent is GR-201; the silane coupling agent is KH-550.

[0020] Preferably, the compatibilizer is selected from one or more of styrene-maleic anhydride copolymer (SMA), maleic anhydride-grafted polyphenylene ether (PPE-g-MAH), and maleic anhydride-grafted polyolefin elastomer (POE-g-MAH) in any proportion.

[0021] More preferably, the compatibilizer is a styrene-maleic anhydride copolymer (SMA).

[0022] Preferably, the lubricant is selected from one or more of ultra-high molecular weight polyethylene (UHMWPE), polytetrafluoroethylene (PTFE), graphite, and molybdenum disulfide in any proportion.

[0023] More preferably, the lubricant is selected from one or any proportion of ultra-high molecular weight polyethylene (UHMWPE) and polytetrafluoroethylene (PTFE).

[0024] As a preferred embodiment, the lubricant is ultra-high molecular weight polyethylene.

[0025] As an optional embodiment, the lubricant is a combination of ultra-high molecular weight polyethylene and polytetrafluoroethylene, wherein the mass ratio of ultra-high molecular weight polyethylene to polytetrafluoroethylene is 1:0.5 to 2; more preferably 1:1.

[0026] Preferably, the antioxidant is a combination of a primary antioxidant and a secondary antioxidant, with a mass ratio of 1:0.5 to 3; wherein the primary antioxidant is a hindered phenolic antioxidant and the secondary antioxidant is a phosphite antioxidant.

[0027] More preferably, the weight ratio of the primary antioxidant to the secondary antioxidant is 1:0.6 to 0.8.

[0028] Preferably, the primary antioxidant is selected from antioxidant 1010, antioxidant 1076, or antioxidant 2246.

[0029] Preferably, the auxiliary antioxidant is selected from antioxidant 168 or antioxidant 626.

[0030] The second objective of this invention is to provide a PA66 / PPE alloy material for wear discs of railway freight car core plates, which is prepared from the above-mentioned composition through the following steps:

[0031] S-1. Prepare raw materials

[0032] Prepare each component according to the stated weight proportions.

[0033] S-2. Raw material drying

[0034] PA66, PPE, and inorganic fillers were vacuum dried at 80–120°C until the moisture content was below 0.05% (w / w), then sealed and set aside for later use; the lubricant was dried at 60–80°C for 2–4 hours, then sealed and set aside for later use.

[0035] S-3. Surface pretreatment of inorganic fillers

[0036] Dissolve the coupling agent in 2-3 times its weight of anhydrous ethanol, then spray it evenly onto the surface of the inorganic filler dried in step S-2, mix it in a high-speed mixer for no less than 10 minutes, and finally vacuum dry it at 110-120℃ for more than 2 hours to obtain the inorganic filler pretreated with coupling agent.

[0037] S-4. Premixed

[0038] The PA66 and PPE dried in step S-2, the lubricant, the pretreated inorganic filler obtained in step S-3, the compatibilizer and antioxidant are all put into a high-speed mixer and mixed for 300-800 r / min for 3-5 minutes to obtain a premix.

[0039] S-5. Melt Blending Extrusion

[0040] The premix obtained in step S-4 is fed into a twin-screw extruder for melt blending and extrusion. The temperatures of each section of the extruder are set as follows: feeding section 220-240℃, compression section 245-270℃, metering section 260-280℃, and die head temperature 255-275℃; the screw speed is 200-400 r / min, and the average residence time of the material in the extruder is about 1-3 minutes, resulting in extruded strips.

[0041] S-6. Cooling Granulation

[0042] The extruded strip is water-cooled or air-cooled and then cut into pellets to obtain PA66 / PPE alloy pellets;

[0043] S-7. Post-processing

[0044] The PA66 / PPE alloy granules obtained in step S-6 are dried at 80-100°C for 2-4 hours and then sealed and packaged to obtain the final product.

[0045] Optionally, in step S-2, PA66 and PPE are dried separately or mixed and then dried.

[0046] Those skilled in the art should understand that the inorganic filler and the polymer matrix (PA66 and PPE) are dried separately.

[0047] Optionally, when the inorganic filler is a compound composition, each filler can be dried individually or mixed and dried together.

[0048] Alternatively, when the lubricant is a compound composition, each lubricant can be dried individually or mixed and dried together.

[0049] Preferably, in step S-3, the rotational speed of the high-speed mixer is 500-1500 r / min, more preferably 1000-1200 r / min.

[0050] Preferably, in step S-4, the rotational speed of the high-speed mixer is 400-600 r / min.

[0051] Preferably, in step S-5, vacuum exhaust is activated during the extrusion process, and the vacuum level is -0.06 to -0.08 MPa.

[0052] In step S-5, the compression section and metering section can be divided into several zones, each with its own temperature control, which is more conducive to the smooth progress of melt blending extrusion.

[0053] A third objective of this invention is to provide the application of the PA66 / PPE alloy material in the preparation of wear discs for railway freight cars.

[0054] The fourth objective of this invention is to provide a wear disc for railway freight car center plate, which is obtained by injection molding from the PA66 / PPE alloy material described in this invention.

[0055] Therefore, the present invention also provides a method for preparing a wear disc of a railway freight car center plate, using the PA66 / PPE alloy material described in the present invention as raw material, comprising the following steps:

[0056] I. Granular drying

[0057] The PA66 / PPE alloy granules of the present invention are dried at 100-150°C for 3-4 hours to reduce the moisture content to below 0.1%.

[0058] II. Injection Molding

[0059] Select a screw-type injection molding machine with a clamping force ≥ 600 tons, a screw length-to-diameter ratio (L / D) of 20-30, and a compression ratio of 2.0-3.0. Equip it with an oil temperature mold temperature controller, preheat the mold to 70-120℃, feed in the dried PA66 / PPE alloy granules, and injection mold it under the following injection parameters to obtain the core disc wear disc blank:

[0060] 1) Screw back pressure: 0.5~3.0MPa;

[0061] 2) Injection molding machine temperature parameters: feeding section 250~260℃, compression section 265~275℃, metering section 275~285℃, nozzle temperature 270~280℃;

[0062] 3) Injection pressure and speed: Injection pressure 80-160 MPa, injection speed in the initial stage of filling 20-60 mm / s, injection speed in the middle and late stages of filling 40-100 mm / s;

[0063] 4) Holding pressure and cooling: Holding pressure 70-120MPa, holding time 30-60 seconds; the product cools and sets naturally in the mold, cooling time 60-120 seconds;

[0064] III. Demolding and Post-processing

[0065] Open the mold, smoothly eject the core plate and wear plate blank, and let it cool naturally to room temperature on a flat surface; or place it in an oven at 80-100℃ for slow annealing for 2-4 hours, and then let it cool naturally to room temperature.

[0066] IV. Machining

[0067] The worn disc blank processed in step III is machined to the specified dimensions and inspected to pass inspection.

[0068] Preferably, the mold is preheated to 80-100°C.

[0069] This invention uses PA66 and PPE as the main resins, forming an interpenetrating network alloy. PA66 possesses high mechanical strength, stiffness, and abrasion resistance, while PPE exhibits excellent heat resistance, dimensional stability, and low moisture absorption. The addition of PPE effectively reduces the moisture absorption rate of PA66, improves the dimensional stability and heat distortion temperature of the material, and compensates for PA66's insufficient creep resistance. The addition of PA66 improves the processing flowability and oil resistance of PPE. With the aid of a compatibilizer, the two resins achieve complementary and synergistic performance enhancement.

[0070] The present invention preferably uses ultra-high molecular weight polyethylene (UHMWPE) and / or polytetrafluoroethylene (PTFE) as lubricants. Both are excellent solid lubricating materials that can form a uniform and continuous transfer film on the friction surface, effectively reducing the coefficient of friction and wear.

[0071] The addition of inorganic fillers can improve the rigidity, hardness, and dimensional stability of materials while reducing production costs. This invention uses 5-20 parts of filler, a moderate amount that enhances the filling effect without significantly reducing the material's toughness. Nano-calcium carbonate, in particular, with its small particle size and large specific surface area, can form a good interfacial bond with the resin matrix after surface treatment with a coupling agent. Under stress, it can induce crazes and shear yielding, thus providing a toughening effect. Furthermore, nano-calcium carbonate filler can improve the thermal conductivity of the material, facilitating the dissipation of frictional heat.

[0072] In summary, the PA66 / PPE alloy material provided by this invention, through the synergistic effect of its components, endows the alloy material with excellent mechanical properties, wear resistance, dimensional stability, thermal stability and environmental adaptability, making it fully suitable for wear discs of railway freight car discs.

[0073] In addition, it is worth mentioning that the PA66 / PPE alloy material provided by this invention, when the wear disc obtained by injection molding reaches its wear limit, can be recycled, crushed, and then injection molded back into a wear disc, thereby achieving recycling.

[0074] In this article, the “parts by weight” of each component refers to the relative proportions of the corresponding components, not the actual mass of the components. Depending on the actual situation, 1 part by weight can be any mass, such as 1g, 10g, 500g, 1kg, or even 1 ton. Detailed Implementation

[0075] The present invention will be described below with reference to specific embodiments. Those skilled in the art will understand that these embodiments are for illustrative purposes only and do not limit the scope of the invention in any way.

[0076] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all raw materials and reagents used in the following examples are commercially available products. The sources of some reagents, raw materials, and equipment are shown in Table 1.

[0077]

[0078] Screw-type injection molding machine: MA16000III, Haitian Plastics Machinery Group Co., Ltd.; Specific parameters: clamping force 1600 tons, screw length-to-diameter ratio (L / D) 20:1, compression ratio 3.2:1.

[0079] Examples 1-8: A PA66 / PPE alloy material

[0080] The raw material composition of PA66 / PPE alloy materials in Examples 1 to 8 is shown in Table 2, where 1 part by weight = 1 kg.

[0081]

[0082] The alloy material is prepared by the following method:

[0083] S-1. Prepare raw materials

[0084] Prepare the raw materials as shown in Table 2.

[0085] S-2. Raw material drying

[0086] Mix PA66 and PPE or dry them separately under vacuum at 110°C for more than 12 hours to reduce the moisture content to below 0.05% (w / w), then seal and set aside. Mix lubricant (UHMWPE and / or PTFE micro powder) or dry them separately under vacuum at 80°C for more than 2 hours, then seal and set aside. Mix inorganic filler (nano-calcium carbonate and / or talc) or dry them separately under vacuum at 110-120°C for more than 4 hours to reduce the moisture content to below 0.05% (w / w), then seal and set aside.

[0087] S-3. Surface pretreatment of inorganic fillers

[0088] The coupling agent was dissolved in anhydrous ethanol at a ratio of 1:2 (w / w), and then sprayed evenly onto the surface of the dried inorganic filler. The mixture was then transferred into a high-speed mixer at a speed of 1000 r / min for at least 10 minutes to ensure that the coupling agent was evenly coated on the surface of the inorganic filler. Finally, the mixture was vacuum dried at 120°C for at least 2 hours to obtain the inorganic filler pretreated with the coupling agent.

[0089] S-4. Premixed

[0090] The dried PA66 and PPE obtained in step S-2, the lubricant, the inorganic filler pretreated with the coupling agent obtained in step S-3, as well as the compatibilizer and antioxidant, are all put into a high-speed mixer (the order of addition is not limited), and mixed for 4 minutes at a speed of 500 r / min to obtain a premix.

[0091] S-5. Melt Blending Extrusion

[0092] The premixed material obtained in step S-4 is fed into the main feed inlet of a co-rotating twin-screw extruder (L / D ratio 40:1). The temperature settings for each section of the extruder are as follows: Zone 1 (feeding section): 230℃; Zone 2: 245℃; Zone 3: 255℃; Zone 4: 260℃; Zone 5: 265℃; Zone 6: 270℃; Zone 7: 275℃; Zone 8: 280℃; Zone 9: 280℃; Zone 10 (die head): 275℃ (Zones 2 to 5 are compression sections, and Zones 6 to 9 are metering sections). The screw speed is set to 300 r / min, and the main feed speed is adjusted according to the output to ensure that the average residence time of the material in the extruder is approximately 2 minutes. Vacuum exhaust is activated during extrusion, with a vacuum level of -0.06 to -0.08 MPa.

[0093] S-6. Cooling Granulation

[0094] The extruded material is cooled in a water tank and then fed into a pelletizer to be pelletized.

[0095] S-7. Post-processing

[0096] The granules obtained in step S-6 are dried at 100°C for 3 hours and then sealed and packaged for later use.

[0097] Comparative Example 1: A cast PA6 core wear disc

[0098] K6 type wear plate, manufactured by Jiangsu Tongqing Vehicle Parts Co., Ltd.

[0099] Comparative Examples 2-5: A Nylon Composite Material

[0100] The raw material composition of the nylon composite materials in Comparative Examples 2 to 5 is shown in Table 3, where 1 part by weight = 1 kg.

[0101]

[0102] Preparation method:

[0103] 1) Comparative Example 2

[0104] PA66 granules were dried at 110℃ for 24 hours and then injection molded into standard test specimens using an injection molding machine. A screw-type injection molding machine was used to injection mold the standard test specimens. Injection temperature settings: feeding section 250℃, compression section 270℃, metering section 280℃, nozzle temperature 275℃; mold temperature 85±5℃; injection pressure 80 MPa; initial injection speed 40 mm / s, mid-to-late filling injection speed 80 mm / s, holding pressure 15–20 seconds; cooling time 25–30 seconds; screw back pressure 2.5 MPa.

[0105] 2) Comparative Examples 3-4

[0106] The granules are prepared by extrusion granulation according to the preparation method described in the embodiments of the present invention, and then sealed and packaged for later use.

[0107] 3) Comparative Example 5

[0108] Except for step S-3, the preparation method described in the embodiments of the present invention is basically followed for extrusion granulation and sealed packaging for later use.

[0109] Test case

[0110] 1. Sample preparation

[0111] After drying the alloy granules of Examples 1-8 and Comparative Examples 3-5 at 100°C for 3 hours, they were injection molded into standard test specimens using a screw injection molding machine. Injection temperature settings: feeding section 250°C, compression section 270°C, metering section 280°C, nozzle temperature 275°C; mold temperature 85±5°C; injection pressure 80 MPa; initial injection speed 40 mm / s, mid-to-late filling injection speed 80 mm / s, holding pressure time 15-20 seconds; cooling time 25-30 seconds; screw back pressure 2.5 MPa.

[0112] The PA6 wear disc of Comparative Example 1 was cut into standard test strip sizes for measurement. The test strip of Comparative Example 2 was used directly for measurement.

[0113] 2. Performance Measurement

[0114] Hardness (HD), tensile strength (MPa), tensile strain (%), compressive stress at 25% strain (MPa), flexural strength (MPa), notched impact strength at 23℃ (kJ / m) 2 -50℃ notched impact strength (kJ / m) 2 ), water absorption (water absorption rate), Vicat softening temperature (B120 method) (°C), product friction coefficient, material friction coefficient and wear rate: the corresponding determinations shall be made in accordance with the methods specified in TB / T 46-2020.

[0115] Dimensional change rate: The corresponding determination shall be carried out in accordance with the method specified in GB / T 1034-2008.

[0116] Heat distortion temperature (°C, 1.82 MPa): The corresponding determination shall be carried out in accordance with the method specified in GB / T 1634-2025.

[0117] 3. Measurement Results

[0118] See Tables 4 and 5.

[0119]

[0120]

[0121] Comparing the data in Table 4 and Table 5, we can see that:

[0122] 1) Mechanical properties

[0123] As can be seen from Examples 1-6, with the increase of PPE content (from 20 parts to 80 parts), the hardness of the material gradually decreased from 80 HD to 64 HD, showing a gentle downward trend. This indicates that the introduction of PPE imparts moderate flexibility to the material while maintaining high rigidity. Example 1 exhibits the highest tensile strength (73 MPa). Although it decreased with increasing PPE content, it remained above 53 MPa, meeting the load-bearing requirements of the wear plate. Notably, the tensile strain significantly increased with increasing PPE content, from 78% (Example 1) to 145% (Example 6), indicating that the ductility and deformability of the material are significantly improved under high PPE content, which is beneficial for absorbing impact energy.

[0124] The compressive stress at 25% strain is an important indicator of a material's load-bearing capacity. The compressive stress of Example 1 reached 114 MPa, which is about 46% higher than that of Comparative Example 1 (pure PA6, 78 MPa) and about 12% higher than that of Comparative Example 2 (pure PA66, 102 MPa). This indicates that the alloy material of the present invention has a superior resistance to deformation under compressive loads, which is crucial for the wear disc of the core plate that is subjected to vertical loads for a long time.

[0125] In terms of bending strength, Example 1 reached 121 MPa, and Examples 2-8 all maintained above 83 MPa, which is far superior to Comparative Example 1 (58 MPa) and also has a significant advantage over Comparative Example 2 (98 MPa). This indicates that the PA66 / PPE alloy system has outstanding load-bearing capacity under bending conditions.

[0126] Comparing Example 3 and Comparative Example 3, it can be seen that: the tensile strength of Comparative Example 3 without compatibilizer is only 52 MPa, which is about 20% lower than that of Example 3 (65 MPa); the notched impact strength of Comparative Example 3 at 23°C is 7.5 kJ / m², which is only half of that of Example 3 (15 kJ / m²); the flexural strength and compressive stress of Comparative Example 3 are significantly lower than those of Example 3. This fully demonstrates that the compatibilizer is the key component for achieving effective bonding between PA66 and PPE phases and fully leveraging the synergistic effect, directly determining the final mechanical properties of the alloy material.

[0127] Example 3 contained 15 parts of nano-calcium carbonate, while Comparative Example 5 did not contain nano-calcium carbonate. Comparing the performance test results of Example 3 and Comparative Example 5, the material hardness increased from 69 HD (Comparative Example 5) to 74 HD (Example 3); the flexural strength increased from 81 MPa (Comparative Example 5) to 103 MPa (Example 3), an increase of approximately 27%; and the 25% strain compressive stress increased from 82 MPa (Comparative Example 5) to 98 MPa (Example 3), an increase of approximately 20%. This indicates that the nano-calcium carbonate filler significantly enhances the rigidity and load-bearing capacity of the material.

[0128] 2) Thermal stability

[0129] Based on the Vicat softening temperature (B120 method) data, the Vicat softening temperatures of Examples 1-8 ranged from 181°C to 214°C, all significantly higher than those of Comparative Example 1 (169°C) and Comparative Example 2 (178°C). Example 6 (80 parts PPE) exhibited a Vicat softening temperature as high as 214°C, approximately 27% higher than pure PA6 and approximately 20% higher than pure PA66. The increased Vicat softening temperature indicates stronger dimensional retention of the material under high-temperature conditions.

[0130] Regarding the heat distortion temperature (1.82 MPa), the values ​​for Examples 1-8 range from 108℃ to 178℃, representing a significant improvement over Comparative Example 1 (62℃) and Comparative Example 2 (68℃). Example 3 achieved a heat distortion temperature of 138℃, approximately 123% higher than pure PA6; Example 6 reached 178℃, approximately 187% higher than pure PA6. This data clearly demonstrates that the introduction of PPE significantly enhances the material's resistance to deformation under high temperature and high load conditions, meeting the requirements for use in the wear disc under extreme conditions such as frictional heat generation and high-temperature exposure in summer, fundamentally solving the performance degradation problem caused by the poor thermal stability of PA6 material.

[0131] 3) Friction and wear performance

[0132] Data on the coefficient of friction of the products and the coefficient of friction of the materials show that the coefficients of friction of Examples 1 to 8 are in the range of 0.18 to 0.22, all lower than those of Comparative Example 1 (0.24 to 0.25), and significantly lower than those of Comparative Example 2 (0.31 to 0.32). The coefficient of friction of the product in Example 5 is as low as 0.18, which is about 28% lower than that of pure PA6.

[0133] The wear rate data more intuitively demonstrates the wear resistance advantages of this invention. The wear rate for all embodiments is 2 × 10⁻⁶. -8 It was the same as Comparative Example 1, but much lower than Comparative Example 2 (2.9 × 10⁻⁶). -8 Comparative Example 3 (5×10) -8 ) and Comparative Example 4 (6.5 × 10 -8 Comparative Example 4 (without lubricant) showed a wear rate as high as 6.5 × 10⁻⁶. -8 The wear rate was approximately 3.25 times that of the example, demonstrating that the addition of ultra-high molecular weight polyethylene and / or polytetrafluoroethylene as solid lubricants effectively transferred a lubricating film onto the friction surface, significantly reducing the material's wear rate. The wear rate of Comparative Example 5 (without calcium carbonate) was 3 × 10⁻⁶. -8 The results were also higher than in the previous example, indicating that the addition of calcium carbonate filler helps improve the wear resistance of the material.

[0134] 4) Hygroscopicity and dimensional stability

[0135] The water absorption test results show that the water absorption rate of the examples is between 0.4% and 1.0%, significantly lower than that of Comparative Example 2 (pure PA66, 1.1%). The water absorption rate of Examples 3-6 is even more stable at 0.4%, a reduction of about 64% compared to pure PA66. It should be noted that although the water absorption rate of Comparative Example 1 (PA6) (0.8%) is lower than that of Comparative Example 2 in the table, this may be due to the shorter test period (24h); in actual long-term use, the equilibrium water absorption rate of PA6 is much higher than this value. The alloy material of the present invention, because the PPE phase itself does not absorb water, and a dense phase interface structure is formed under the action of the compatibilizer, effectively blocks the penetration path of water into the PA66 phase, thereby significantly reducing the overall hygroscopicity of the material.

[0136] Correspondingly, the dimensional change rate data also confirms this advantage. The dimensional change rates of Examples 1-8 are 0.12%-0.35%, far less than Comparative Example 1 (1.05%) and Comparative Example 2 (0.85%). The dimensional change rate of Example 6 is only 0.12%, which is about 89% lower than that of pure PA6. This characteristic fundamentally solves the problems of dimensional accuracy loss and loose assembly caused by moisture absorption and expansion of PA6 material, ensuring that the wear plate can maintain stable dimensions under different humidity environments, and significantly improving the product's adaptability to all climate environments.

[0137] 5) Low-temperature toughness

[0138] As can be seen from the -50℃ notch impact strength data, the low-temperature impact strength of all embodiments (6~12 kJ / m) 2 Both are superior to Comparative Example 1 (4 kJ / m 2 ) and Comparative Example 2 (3.5 kJ / m 2 Example 6 showed an impact strength of up to 12 kJ / m at -50°C. 2 It is 3 times that of pure PA6 and approximately 3.4 times that of pure PA66. Comparative Example 3 (7 kJ / m³) 2 ) and Comparative Example 3 (without compatibilizer, 2.5 kJ / m 2 As can be seen, the addition of the compatibilizer increases the low-temperature impact strength by approximately 180%. This result indicates that the present invention, through the effective compatibilization and composite of PA66 and PPE, forms a two-phase structure with good low-temperature toughness, making the core disc wear disc less prone to brittle fracture when used in extremely cold regions, thus solving the prominent problem of high breakage risk of existing PA6 and PA66 material core disc wear discs in low-temperature environments.

[0139] 6) Overall effect evaluation

[0140] Based on the above analysis, the PA66 / PPE alloy material of the present invention achieves the following significant technical effects through the synergistic effect between its components:

[0141] ① Excellent load-bearing and mechanical properties: 25% strain compressive stress reaches 72-114 MPa, and flexural strength reaches 83-121 MPa, which is significantly better than pure PA6 and pure PA66 materials, ensuring that the core disc wear disc has sufficient load-bearing capacity and deformation resistance under heavy load conditions.

[0142] ② Good toughness and ductility: tensile strain can reach 78%~145%, and notched impact strength at 23℃ reaches 12~21kJ / m 2 It combines high strength with good toughness, solving the problem of low impact toughness (6.5 kJ / m²) in pure PA66 material.

[0143] ③ Excellent thermal stability: Vicat softening temperature is 181~214℃, and heat distortion temperature (1.82 MPa) is 108~178℃, which is much higher than that of pure PA6 (62℃) and pure PA66 (68℃), and can meet the requirements of high temperature working conditions and long-term frictional heat generation conditions.

[0144] ④ Outstanding wear resistance: The product has a low coefficient of friction of 0.18 to 0.22, and the wear rate is stable at 2×10⁻⁶. -8 Compared to a lubricant-free system, it reduces wear by approximately 69%, significantly extending the service life of the core disc wear plate.

[0145] ⑤ Extremely low hygroscopicity and excellent dimensional stability: The water absorption rate is as low as 0.4% to 1.0% in 24 hours, and the dimensional change rate is only 0.12% to 0.35%, which solves the performance fluctuation and dimensional accuracy problems caused by the moisture absorption-water loss cycle of PA materials and meets the requirements for use in all climate environments.

[0146] ⑥ Excellent low-temperature toughness: Notched impact strength at -50℃ reaches 6~12 kJ / m 2 It is 1.5 to 3 times that of pure PA6, ensuring safe and reliable application in extremely cold regions.

[0147] ⑦ Flexible and adjustable formulation design: By adjusting the ratio of PA66 to PPE, the hardness, strength, toughness and heat resistance of the material can be adjusted within a wide range to adapt to different working conditions and usage requirements, and it has good engineering adaptability.

[0148] ⑧ Taking all performance characteristics into account, the PA66 / PPE alloy materials in Examples 3 to 6 are the preferred embodiments of the present invention.

[0149] Example 9: A wear disc for railway freight car cores

[0150] Using PA66 / PPE alloy material prepared in any one of Examples 1-8 as raw material, dry at 100°C for 3 hours to reduce the moisture content to below 0.1%. Select an appropriate mold and use the injection molding machine and injection molding process parameters described in the test examples to obtain a core plate wear plate blank through injection molding (the above injection molding process parameters are incorporated into this paragraph by reference). Open the mold, smoothly eject the core plate wear plate blank, and allow it to cool naturally to room temperature on a flat surface. Then machine it to the specified dimensions, inspect it, and if it passes the inspection, the railway freight car core plate wear plate is obtained.

[0151] In summary, this invention provides a novel PA66 / PPE alloy material and a wear disc for railway freight cars prepared from it. The PA66 / PPE alloy material of this invention possesses excellent load-bearing and mechanical properties, good toughness and ductility, outstanding thermal stability, remarkable wear resistance, extremely low moisture absorption, excellent dimensional stability, and excellent low-temperature toughness; all these properties are superior to those of cast PA6 wear discs.

Claims

1. A PA66 / PPE alloy material composition for wear discs of railway freight car center plates, comprising the following components in parts by weight: 20-80 parts PA66, 20-80 parts PPE, 10-30 parts compatibilizer, 2-15 parts lubricant, 0.2-1.0 parts antioxidant, 0.1-0.5 parts coupling agent, 5-30 parts inorganic filler; The total weight of PA66 and PPE is 100 parts; the average particle size of the inorganic filler is 40-100 nm.

2. The PA66 / PPE alloy material composition according to claim 1, characterized in that, The PA66 / PPE alloy material composition comprises the following components in parts by weight: 20-50 parts PA66, 50-80 parts PPE, 20-30 parts compatibilizer, 8-15 parts lubricant, 0.4-0.6 parts antioxidant, 0.1-0.2 parts coupling agent, 5-15 parts inorganic filler; The total weight of PA66 and PPE is 100 parts; the average particle size of the inorganic filler is 40-100 nm.

3. The PA66 / PPE alloy material composition according to claim 1 or 2, characterized in that, The relative viscosity of the PA66 is 2.0 to 4.5, more preferably 2.5 to 3.0; Preferably, the intrinsic viscosity of the PPE is 20–80 dL / g, more preferably 30–50 dL / g.

4. The PA66 / PPE alloy material composition according to claim 1 or 2, characterized in that, The inorganic filler is selected from one or two of talc powder and nano calcium carbonate in any proportion. Preferably, the inorganic filler is nano-calcium carbonate; Preferably, the coupling agent is selected from one or more of titanate coupling agents and silane coupling agents in any proportion; More preferably, the titanate coupling agent is GR-201; the silane coupling agent is KH-550.

5. The PA66 / PPE alloy material composition according to claim 1 or 2, characterized in that, The compatibilizer is selected from one or more of styrene-maleic anhydride copolymer, maleic anhydride-grafted polyphenylene ether, and maleic anhydride-grafted polyolefin elastomer in any proportion. Preferably, the compatibilizer is a styrene-maleic anhydride copolymer; Preferably, the lubricant is selected from one or more of ultra-high molecular weight polyethylene, polytetrafluoroethylene, graphite and molybdenum disulfide in any proportion; More preferably, the lubricant is selected from one or two of ultra-high molecular weight polyethylene and polytetrafluoroethylene in any proportion; Preferably, the lubricant is ultra-high molecular weight polyethylene; More preferably, the lubricant is a combination of ultra-high molecular weight polyethylene and polytetrafluoroethylene, wherein the mass ratio of ultra-high molecular weight polyethylene to polytetrafluoroethylene is 1:0.5 to 2; more preferably, it is 1:

1. Preferably, the antioxidant is a combination of a primary antioxidant and a secondary antioxidant, with a mass ratio of 1:0.5 to 3; wherein the primary antioxidant is a hindered phenolic antioxidant, and the secondary antioxidant is a phosphite antioxidant. More preferably, the weight ratio of the primary antioxidant to the secondary antioxidant is 1:0.6 to 0.8; Preferably, the primary antioxidant is selected from antioxidant 1010, antioxidant 1076, or antioxidant 2246; Preferably, the auxiliary antioxidant is selected from antioxidant 168 or antioxidant 626.

6. A PA66 / PPE alloy material for wear discs of railway freight car center plates, prepared from the PA66 / PPE alloy material composition of any one of claims 1 to 5 through the following steps: S-1. Prepare raw materials Prepare each component according to the stated weight proportions. S-2. Raw material drying PA66, PPE, and inorganic fillers were vacuum dried at 80–120°C until the moisture content was below 0.05% (w / w), then sealed and set aside for later use; the lubricant was dried at 60–80°C for 2–4 hours, then sealed and set aside for later use. S-3. Surface pretreatment of inorganic fillers Dissolve the coupling agent in 2-3 times its weight of anhydrous ethanol, then spray it evenly onto the surface of the inorganic filler dried in step S-2, mix it in a high-speed mixer for no less than 10 minutes, and finally vacuum dry it at 110-120℃ for more than 2 hours to obtain the inorganic filler pretreated with coupling agent. S-4. Premixed The PA66 and PPE dried in step S-2, the lubricant, the pretreated inorganic filler obtained in step S-3, the compatibilizer and antioxidant are all put into a high-speed mixer and mixed for 300-800 r / min for 3-5 minutes to obtain a premix. S-5. Melt Blending Extrusion The premix obtained in step S-4 is fed into a twin-screw extruder for melt blending and extrusion. The temperatures of each section of the extruder are set as follows: feeding section 220-240℃, compression section 245-270℃, metering section 260-280℃, and die head temperature 255-275℃; the screw speed is 200-400 r / min, and the average residence time of the material in the extruder is about 1-3 minutes, resulting in extruded strips. S-6. Cooling Granulation The extruded strip is water-cooled or air-cooled and then cut into pellets to obtain PA66 / PPE alloy pellets; S-7. Post-processing The PA66 / PPE alloy granules obtained in step S-6 are dried at 80-100°C for 2-4 hours and then sealed and packaged to obtain the final product.

7. The PA66 / PPE alloy material according to claim 6, characterized in that, In step S-3, the rotational speed of the high-speed mixer is 500-1500 r / min, more preferably 1000-1200 r / min; Preferably, in step S-4, the rotational speed of the high-speed mixer is 400–600 r / min; Preferably, in step S-5, vacuum exhaust is activated during the extrusion process, and the vacuum level is -0.06 to -0.08 MPa.

8. The application of the PA66 / PPE alloy material as described in claim 6 or 7 in the preparation of wear discs for railway freight cars.

9. A wear disc for railway freight cars, obtained by injection molding from the PA66 / PPE alloy material as described in claim 6 or 7.

10. A method for preparing a wear disc for a railway freight car center plate, using the PA66 / PPE alloy material as described in claim 6 or 7 as raw material, comprising the following steps: I. Granular drying The PA66 / PPE alloy granules of the present invention are dried at 100-150°C for 3-4 hours to reduce the moisture content to below 0.1%. II. Injection Molding Select a screw-type injection molding machine with a clamping force ≥ 600 tons, a screw length-to-diameter ratio of 20-30, and a compression ratio of 2.0-3.

0. Equip it with an oil temperature mold temperature controller. Preheat the mold to 70-120℃, feed in dried PA66 / PPE alloy granules, and injection mold under the following injection parameters to obtain the core disc wear disc blank: 1) Screw back pressure: 0.5~3.0MPa; 2) Injection molding machine temperature parameters: feeding section 250~260℃, compression section 265~275℃, metering section 275~285℃, nozzle temperature 270~280℃; 3) Injection pressure and speed: Injection pressure 80-160 MPa, injection speed in the initial stage of filling 20-60 mm / s, injection speed in the middle and late stages of filling 40-100 mm / s; 4) Holding pressure and cooling: Holding pressure 70-120MPa, holding time 30-60 seconds; the product cools and sets naturally in the mold, cooling time 60-120 seconds; III. Demolding and Post-processing Open the mold, smoothly eject the core plate and wear plate blank, and let it cool naturally to room temperature on a flat surface; or place it in an oven at 80-100℃ for slow annealing for 2-4 hours, and then let it cool naturally to room temperature. IV. Machining The worn disc blank processed in step III is machined to the specified dimensions and inspected to pass inspection. Preferably, the mold is preheated to 80-100°C.

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