Integrally-formed coating-free high-performance composite sleeper

Abstract

The invention relates to the technical field of railway equipment preparation, and discloses an integrally-formed coating-free high-performance composite sleeper which comprises a reinforced core layer, a resin matrix layer and a hydrophobic coating distributed from inside to outside, the reinforced core layer comprises, by weight, 60-70 parts of basalt fibers and 20-30 parts of carbon fibers, and the mass ratio of the basalt fibers to the carbon fibers is 3: 1; the resin matrix layer is prepared from the following components in parts by weight: 90 to 110 parts of polyurethane, 10 to 15 parts of a bismaleimide dynamic cross-linking agent, 3 to 5 parts of graphene oxide, 2 to 4 parts of a TiO2-coated polydopamine core-shell structure additive and 5 to 8 parts of microcapsules; the outer surface of the resin matrix layer is covered with the hydrophobic coating, and the hydrophobic coating is prepared from, by weight, 0.5-1.0 part of fluorine-containing silane; through systematic innovation of fiber directional reinforcement, a dynamic self-repairing network, nano composite protection and a gradient forming process, an integrated breakthrough of light weight, long service life and efficient production is realized.

Description

Technical Field

[0001] This invention relates to the field of urban rail transit technology, specifically to one-piece molded, paint-free, high-performance composite material sleepers. Background Technology

[0002] The rapid development of rail transit has placed higher demands on the performance of railway sleepers. Traditional concrete sleepers, due to their inherent defects such as excessive weight and significant brittleness, are unable to meet the requirements of high-speed railways for vibration reduction, noise reduction, and long-term durability. Fiber-reinforced composite sleepers have become a research hotspot due to their advantages such as lightweight and corrosion resistance, but they still face key technical bottlenecks in practical engineering applications, which restrict their large-scale promotion.

[0003] Existing fiber-reinforced composite railway sleepers generally suffer from limitations in material systems and structural design. The mixing ratio and spatial distribution of fiber reinforcement phases lack scientific optimization, leading to interfacial debonding and delamination failures under complex stress conditions. The resin matrix has insufficient environmental adaptability and cannot effectively inhibit the propagation of microcracks caused by harsh conditions such as damp heat and freeze-thaw cycles. The surface protection system is limited in function and has poor durability, making it difficult to cope with the synergistic effects of acid rain erosion and ultraviolet aging. More importantly, traditional molding processes struggle to achieve sufficient resin impregnation and interfacial bonding strength control under high fiber content conditions, severely impacting product qualification rate and performance stability.

[0004] The aforementioned problems expose systemic deficiencies in the structural design, functional protection, and manufacturing processes of current composite material railway sleepers, resulting in a significant gap between their overall performance and engineering application requirements. Developing novel sleeper materials that combine high mechanical properties, environmental adaptability, and efficient manufacturing processes has become an urgent technical challenge in the rail transit field. To address these challenges, this invention proposes an integrated, paint-free, high-performance composite material railway sleeper. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an integrated, paint-free, high-performance composite material sleeper, which solves the problems of high material density, poor environmental resistance, and manufacturing process defects in traditional sleepers.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an integrated, paint-free, high-performance composite material sleeper, comprising a reinforcing core layer, a resin matrix layer, and a hydrophobic coating distributed from the inside out, wherein:

[0007] The reinforcing core layer is composed of basalt fibers and carbon fibers arranged in an oriented manner, forming a multi-layer fiber structure through a multi-axial guiding system;

[0008] The multilayer fiber structure has a preset layup sequence, which is a symmetrical layup structure, wherein the carbon fiber layers are symmetrically distributed relative to the geometric mid-plane of the reinforcing core layer, so as to suppress or eliminate the warping deformation that may occur in the composite material during curing and use.

[0009] As a preferred structure, the outermost two layers of the symmetrical ply structure are carbon fiber layers, which can enable the reinforcing core layer to obtain higher bending stiffness.

[0010] The resin matrix layer has a cuboid structure and a thickness of 10–40 cm; the reinforcing core layer is uniformly embedded in the resin matrix layer.

[0011] A hydrophobic coating with a thickness of 60-90μm completely covers the outer surface of the resin matrix layer;

[0012] Reinforcing core layer: by weight, it contains 60-70 parts of basalt fiber and 20-30 parts of carbon fiber, with a mass ratio of 3:1 between the two fibers;

[0013] Resin matrix layer: by weight, it contains 90-110 parts of polyurethane, 10-15 parts of bismaleimide dynamic crosslinking agent, 3-5 parts of graphene oxide, 2-4 parts of TiO2@polydopamine core-shell structure additive and 5-8 parts of microcapsules.

[0014] Hydrophobic coating: contains 0.5 to 1.0 parts by weight of fluorosilane.

[0015] Preferably, the bismaleimide dynamic crosslinking agent is formed by a Diels-Alder reaction between furan-modified polyurethane and bismaleimide.

[0016] Preferably, the polyurethane is a polyether-type polyurethane.

[0017] Preferably, the fabrication process of the reinforced core layer includes the following steps:

[0018] C1. Fiber pretreatment: Basalt fiber and carbon fiber are placed in a drying oven and dried at 60-80℃ for 2-4 hours to remove surface moisture;

[0019] C2. The pretreated basalt fiber and carbon fiber are continuously supplied and compounded into a multi-layer fiber structure through a multi-axial guiding and tension control system at a mass ratio of 3:1 and a preset fiber layer direction to form a reinforcing core layer.

[0020] Preferably, the tension of the multi-axial guiding and tension control system in step C2 is 50-80 N.

[0021] Preferably, the microcapsules have a particle size of 20-50 μm, the wall material of the microcapsules is polyurea formaldehyde, and the core of the microcapsules is bismaleimide monomer.

[0022] Preferably, the preparation of the resin matrix layer includes the following steps:

[0023] S1. Synthesis of furan-modified polyurethane: Polyurethane and furan methylamine are mixed at an isocyanate group:amine equivalent ratio of 1:0.8 to 1:1 and reacted at 60-65℃ for 4-6 hours to obtain furan-modified polyurethane.

[0024] S2. Mixing of dynamic crosslinking agent and functional additives: Bismaleimide, graphene oxide, and TiO2@polydopamine core-shell structure are added sequentially to the product of step S1. Vacuum degassing is performed at 50-60℃ for 30-40 min, followed by mechanical stirring at 500-800 rpm for 20-30 min to achieve uniform dispersion.

[0025] S3. Add microcapsules: Add microcapsules and mix by ultrasonic dispersion at a frequency of 40kHz, a power of 200-300W, and a time of 10-15min to obtain a resin matrix liquid.

[0026] Preferably, in step S1, the functional group that reacts with the polyurethane and furanylamine is the isocyanate group of the polyurethane molecular chain. In order to ensure the occurrence of the reaction and the accuracy of the stoichiometry, the content of the isocyanate group (NCO wt%) of the selected polyurethane raw material needs to be determined in advance.

[0027] Preferably, the integration process of the reinforcing core layer and the resin matrix layer includes the following steps:

[0028] T1. Continuous fiber supply and resin impregnation: The reinforcing core layer is continuously introduced into the resin matrix liquid obtained in step S3 and impregnated for 3 to 5 minutes under a vacuum degree ≤100Pa.

[0029] T2. Extrusion Molding and Gradient Curing: The impregnated reinforcing core layer and resin matrix liquid are introduced into a three-stage temperature-controlled extrusion die, wherein the three-stage temperature-controlled extrusion die includes:

[0030] Pre-forming zone: Temperature 80-90℃, apply 5-8MPa linear pressure to the fiber-resin system to remove air bubbles and allow the composite to be initially formed;

[0031] Main curing zone: Temperature 120-130℃, radial pressure 12-15MPa applied, traction speed 0.5~1.2m / min, the main curing reaction of the resin matrix liquid occurs in this zone;

[0032] Shaping and post-curing zone: Temperature 90-100℃, maintain holding pressure 8-10MPa to complete the final shaping and further curing of the resin matrix liquid;

[0033] Profile output: The sleeper profile is cooled to below 40°C at a rate of 10-15°C / s by a water cooling system to obtain a composite structure of reinforced core layer and resin matrix.

[0034] Preferably, the preparation process of the hydrophobic coating includes the following steps:

[0035] F1. Surface pretreatment: Oxygen plasma treatment is performed on the outer surface of the resin matrix layer, with a power of 150-200W and a time of 2-3 minutes;

[0036] F2. Preparation of fluorosilane solution: Dissolve fluorosilane in tetrahydrofuran to prepare a 1-2 wt% solution. Stir at 200-300 rpm, add 0.05-0.1 wt% tetrabutyl titanate as a crosslinking promoter, and ultrasonically disperse at a frequency of 26-30 kHz, a power of 130-170 W, and a time of 5-8 min.

[0037] F3. Spraying process: Selective spraying is carried out using a spray gun, with a spraying pressure of 0.2-0.4MPa, and three sprayings are applied. The thickness of each spray is 20-30μm, and the interval between sprayings is 10-15min.

[0038] F4. Low temperature curing: Curing with hot air at 60-70℃ for 3-4 hours.

[0039] Preferably, the TiO2@polydopamine core-shell structure consists of an anatase TiO2 core and a polydopamine shell, and is grafted onto the resin molecular chain using KH-550 silane coupling agent. Its preparation includes the following steps:

[0040] H1. Anatase TiO2 nanoparticles with a particle size of 40-60 nm were synthesized by sol-gel method, and high-purity products were obtained after centrifugation, washing and drying.

[0041] H2. The anatase TiO2 nanoparticles were dispersed in a Tris-HCl buffer solution, sonicated for 25-35 min, and then dopamine hydrochloride was added. The mixture was then magnetically stirred at room temperature in the dark for 12-24 h to promote the in-situ polymerization of polydopamine on the TiO2 surface to form a shell.

[0042] H3. After the reaction is completed, the particles are separated by centrifugation and washed with deionized water and ethanol alternately 3 to 4 times. The drying temperature is controlled at 50 to 60°C and the time is 6 to 12 hours to obtain TiO2@polydopamine core-shell nanoparticles with a shell thickness of 8 to 12 nm.

[0043] H4. The TiO2@polydopamine core-shell nanoparticles obtained in H3 are redispersed in anhydrous ethanol or toluene and ultrasonically treated for 25-35 min. Then, KH-550 silane coupling agent equivalent to 1% to 5% of the mass of TiO2@polydopamine core-shell nanoparticles is added and reacted at 70-80℃ for 4-6 h under an inert atmosphere, so that KH-550 condenses with the phenolic hydroxyl or amino groups on the surface of polydopamine to form a surface grafted structure.

[0044] H5. After centrifugation and washing with ethanol 3-4 times, the product was vacuum dried at 60-70℃ for 6-12 hours to obtain TiO2@polydopamine core-shell nanoparticles grafted with KH-550.

[0045] Preferably, in step H2, the amount of dopamine hydrochloride added is such that the mass ratio of dopamine hydrochloride to the anatase phase TiO2 nanoparticles is 0.5:1 to 2:1.

[0046] Preferably, the concentration of the Tris-HCl buffer solution is 10–50 mM and the pH range is 8.0–8.5.

[0047] Preferably, the microcapsule size is measured by laser diffraction dry method, the opacity is controlled at 5%–10%, and the refractive index is set to the typical value of polyurea formaldehyde.

[0048] This invention provides an integrated, paint-free, high-performance composite material railway sleeper, which has the following advantages:

[0049] 1. This invention utilizes a multi-layered oriented arrangement of basalt fiber and carbon fiber at a mass ratio of 3:1. By complementing the superior elongation at break of basalt fiber with the high modulus of carbon fiber, it enhances impact resistance and significantly reduces material density while maintaining structural strength. This solves the transportation and installation cost problems caused by the excessive density of traditional railway sleeper materials. Simultaneously, graphene oxide forms chemical bonds with fibers and resin through surface functional groups, improving the interfacial bonding state, enabling effective stress transfer from fibers, and reducing the risk of interlayer delamination.

[0050] 2. This invention enables the material to achieve self-repair of microcracks under thermal triggering conditions through the synergistic effect of furan-bismaleimide dynamic covalent network and polyurea formaldehyde microcapsules. The dynamic cross-linked network can adjust the internal stress distribution according to changes in ambient temperature and humidity, effectively delaying interface aging and significantly improving the long-term durability of sleepers under harsh climates such as humid heat and freeze-thaw cycles.

[0051] 3. The TiO2@polydopamine core-shell structure of this invention forms a multi-protection system through ultraviolet shielding and free radical capture mechanisms, combined with the superhydrophobic properties of the fluorosilane hydrophobic coating. This design not only blocks water penetration and chemical corrosion, but also degrades surface contaminants through photocatalysis, ensuring the surface integrity of the sleeper in complex environments. The introduction of furan-bismaleimide dynamic covalent bonds into the resin matrix layer allows for reversible cross-linking reactions in the temperature range of 80-120℃, repairing microcracks. The bismaleimide monomer encapsulated in polyurea formaldehyde microcapsules is released when the material is damaged, reacting with the active groups in the resin to fill macroscopic cracks. These two mechanisms repair damage at different scales.

[0052] The TiO2@polydopamine core-shell structure effectively delays the photoaging process of the resin through its ultraviolet absorption capacity and free radical scavenging mechanism; the adhesion properties of polydopamine significantly improve the bonding force between the substrate layer and the reinforcing core layer; the fluorosilane coating, through the directional arrangement of fluorocarbon chains in its molecular structure, constructs a low surface energy protective layer, and the modification effect of KH-550 coupling agent further ensures the long-term bonding stability between the fluorosilane coating and the substrate layer.

[0053] 4. This invention achieves a continuous production process through a three-stage temperature-controlled extrusion process, which uses staged pressure and temperature control to fully impregnate fibers and precisely cure resins. The pre-forming zone eliminates air bubbles, the main curing zone completes the cross-linking reaction, and the shaping zone stabilizes the product morphology. This process breaks through the technical bottlenecks of easy delamination and uncontrolled porosity in high-fiber-content composite materials, and provides reliable process support for efficient manufacturing. Attached Figure Description

[0054] Figure 1 This is a flowchart of the preparation process of the present invention. Detailed Implementation

[0055] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] The main raw materials and reagents used in the following examples are as follows. Unless otherwise specified, all reagents are commercially available analytical grade or higher grade products.

[0057] Furan methylamine: CAS: 617-89-0;

[0058] Bismaleimide: CAS: 541-59-3;

[0059] Graphene oxide: CAS: 7440-44-0;

[0060] Dopamine hydrochloride: CAS: 62-31-7;

[0061] Formaldehyde solution: CAS: 50-00-0;

[0062] Tetrabutyl titanate: CAS: 5593-70-4;

[0063] Tetrahydrofuran: CAS: 109-99-9;

[0064] Toluene: CAS: 108-88-3.

[0065] Please see the appendix Figure 1 This invention provides an integrated, paint-free, high-performance composite material railway sleeper through three embodiments, the details of which are as follows:

[0066] Example 1:

[0067] The one-piece molded, paint-free, high-performance composite material sleeper comprises a reinforcing core layer, a resin matrix layer, and a hydrophobic coating, wherein:

[0068] The reinforcing core layer is composed of basalt fibers and carbon fibers arranged in an oriented manner, forming a multi-layer fiber structure through a multi-axial guiding system.

[0069] The resin matrix layer has a cuboid structure; the reinforcing core layer is uniformly embedded in the resin matrix layer;

[0070] A hydrophobic coating with a thickness of 60 μm completely covers the outer surface of the resin matrix layer;

[0071] The reinforced core layer is prepared as follows:

[0072] C1. Fiber pretreatment: 66 parts of basalt fiber and 22 parts of carbon fiber were dried at 70℃ for 3 hours.

[0073] C2. Reinforced core layer forming: Six layers of basalt fiber and two layers of carbon fiber are continuously laid in a 3:1 mass ratio using a multi-axial guiding system (fiber tension 70N), with the fiber direction of each layer parallel to the long axis of the sleeper.

[0074] The multi-layer fiber structure, consisting of 6 layers of basalt fiber and 2 layers of carbon fiber, has the following layup sequence: [C / B / B / B / B / B / B / C]; where C represents the carbon fiber layer and B represents the basalt fiber layer. This layup sequence is either from top to bottom or from outside to inside. This is a symmetrical layup structure.

[0075] Resin matrix preparation:

[0076] S1. Synthesis of furan-modified polyurethane: 100 parts of polyether polyurethane were tested and found to have an isocyanate group (-NCO) content of 3.2 wt%. Based on the -NCO content, the corresponding furan methylamine was added to make the equivalent ratio of isocyanate group to amine group 1:0.9. After mixing, the mixture was reacted at 63℃ for 5 h to obtain furan-modified polyurethane.

[0077] S2. Dynamic crosslinking agent mixing: Add 12 parts of bismaleimide, 4 parts of graphene oxide, and 3 parts of TiO2@polydopamine to the product of step S1 in sequence, and degas under vacuum at 55°C for 35 min (mechanical stirring at 650 rpm / 25 min).

[0078] S3. Add microcapsules: Add 6.5 parts of microcapsules, disperse by ultrasonication at a frequency of 40kHz, a power of 200-300W, and a mixing time of 10 minutes to obtain a resin matrix liquid.

[0079] The integration process between the reinforcing core layer and the resin matrix layer includes the following steps:

[0080] T1. Continuous fiber supply and resin impregnation: The reinforcing core layer is continuously introduced into the resin matrix liquid obtained in step S3 and impregnated for 3 minutes under a vacuum degree ≤100Pa.

[0081] T2. Extrusion molding and gradient curing: The impregnated reinforcing core layer and resin matrix liquid are introduced into a three-stage temperature-controlled extrusion die.

[0082] The three-stage temperature-controlled extrusion die includes:

[0083] Pre-forming zone: Temperature 80℃, apply 8MPa linear pressure to remove air bubbles and allow the composite to initially form;

[0084] Main curing zone: Temperature 120℃, radial pressure 15MPa applied, traction speed 0.5m / min, the main curing reaction of the resin matrix liquid occurs in this zone;

[0085] Shaping and post-curing zone: Temperature 90℃, maintain holding pressure 8MPa to complete the final shaping and further curing of the resin matrix liquid;

[0086] Profile output: The sleeper profile is cooled to below 40°C at a rate of 10°C / s by a water cooling system to obtain a composite structure of reinforced core layer and resin matrix.

[0087] The preparation process of the hydrophobic coating includes the following steps:

[0088] F1. Surface pretreatment: The outer surface of the resin matrix layer is treated with oxygen plasma at a power of 150W for 3 minutes.

[0089] F2. Preparation of fluorosilane solution: Dissolve fluorosilane in tetrahydrofuran to prepare a 1wt% solution. Stir at 200 rpm, add 0.05wt% tetrabutyl titanate as a crosslinking promoter, and ultrasonically disperse at 26kHz, 130W, for 5 min.

[0090] F3. Spraying process: Selective spraying is carried out using a spray gun, with a spraying pressure of 0.2MPa, and three sprayings are applied. The thickness of each spray is 20μm, and the interval between sprayings is 10min.

[0091] F4. Low temperature curing: Curing with hot air at 60℃ for 4 hours.

[0092] The microcapsules have a particle size of 20 μm, the wall material of the microcapsules is polyurea formaldehyde, and the core of the microcapsules is bismaleimide monomer.

[0093] The TiO2@polydopamine core-shell structure consists of an anatase TiO2 core and a polydopamine shell, and is grafted onto the resin molecular chain using KH-550 silane coupling agent. Its preparation includes the following steps:

[0094] H1. Anatase TiO2 nanoparticles with a particle size of 40 nm were synthesized by sol-gel method, and high-purity products were obtained after centrifugation, washing and drying.

[0095] H2. The anatase TiO2 nanoparticles were dispersed in a Tris-HCl buffer solution with a concentration of 10 mM and a pH of 8.0. After ultrasonic treatment for 25 min, dopamine hydrochloride was added to make the mass ratio of dopamine to the anatase TiO2 nanoparticles 1:1. The mixture was magnetically stirred at room temperature in the dark for 12 h to promote the in-situ polymerization of polydopamine on the TiO2 surface to form a shell.

[0096] H3. After the reaction was completed, TiO2@polydopamine core-shell nanoparticles with a shell thickness of 8 nm were obtained by centrifugation and washing with deionized water and ethanol three times alternately. The drying temperature was controlled at 50℃ for 6 hours.

[0097] H4. The TiO2@polydopamine core-shell nanoparticles obtained in H3 were redispersed in anhydrous ethanol or toluene and sonicated for 25 min. Then, KH-550 silane coupling agent equivalent to 1% of the mass of TiO2@polydopamine core-shell nanoparticles was added and reacted at 70 °C for 4 h under an inert atmosphere to allow KH-550 to condense with the phenolic hydroxyl or amino groups on the surface of polydopamine to form a surface grafted structure.

[0098] H5. After centrifugation and washing with ethanol three times, the product was vacuum dried at 60℃ for 6h to obtain TiO2@polydopamine core-shell nanoparticles grafted with KH-550.

[0099] Example 2:

[0100] The one-piece molded, paint-free, high-performance composite material sleeper comprises a reinforcing core layer, a resin matrix layer, and a hydrophobic coating, wherein:

[0101] The reinforcing core layer is composed of basalt fibers and carbon fibers arranged in an oriented manner, forming a multi-layer fiber structure through a multi-axial guiding system;

[0102] The resin matrix layer has a cuboid structure; the reinforcing core layer is uniformly embedded in the resin matrix layer;

[0103] A hydrophobic coating with a thickness of 90 μm completely covers the outer surface of the resin matrix layer;

[0104] The following steps are taken to prepare the reinforced core layer:

[0105] C1. Fiber pretreatment: 60 parts of basalt fiber and 20 parts of carbon fiber were dried at 60℃ for 2 hours.

[0106] C2. Reinforcing Core Layer Forming: Six layers of basalt fiber and two layers of carbon fiber are continuously laid in a 3:1 mass ratio using a multi-axial guiding system (fiber tension 50N), with the fiber direction of each layer parallel to the long axis of the sleeper. The specific layup sequence of the multi-layer fiber structure consisting of six layers of basalt fiber and two layers of carbon fiber is: [C / B / B / B / B / B / C]. Here, C represents the carbon fiber layer and B represents the basalt fiber layer, and this layup sequence is a top-to-bottom or outside-to-inside stacking order. This is a symmetrical layup structure.

[0107] The microcapsules have a particle size of 50 μm, the wall material of the microcapsules is polyurea formaldehyde, and the core of the microcapsules is bismaleimide monomer.

[0108] The preparation of the resin matrix layer includes the following steps:

[0109] S1. Synthesis of furan-modified polyurethane: 90 parts of polyurethane were tested, and the content of isocyanate groups (-NCO) was determined to be 2.9 wt%. Based on this -NCO content, the corresponding furan methylamine was added to make the equivalent ratio of isocyanate groups to amine groups 1:0.8. After mixing, the mixture was reacted at 60℃ for 4 h to obtain furan-modified polyurethane.

[0110] S2. Mixing of dynamic crosslinking agent and functional additives: Add 10 parts of bismaleimide, 3 parts of graphene oxide, and 2 parts of TiO2@polydopamine core-shell structure to the product in sequence. Degas at 60℃ for 30 min, then mechanically stir at 800 rpm for 20 min to achieve uniform dispersion.

[0111] S3. Add microcapsules: Add 5 parts of microcapsules and mix by ultrasonic dispersion at a frequency of 40kHz, a power of 300W, and a time of 15min to obtain a resin matrix liquid.

[0112] The integration process between the reinforcing core layer and the resin matrix layer includes the following steps:

[0113] T1. Continuous fiber supply and resin impregnation: The reinforcing core layer is continuously introduced into the resin matrix liquid obtained in step S3 and impregnated for 5 minutes under a vacuum degree ≤100Pa.

[0114] T2. Extrusion Molding and Gradient Curing: The impregnated reinforcing core layer and resin matrix liquid are introduced into a three-stage temperature-controlled extrusion die, wherein the three-stage temperature-controlled extrusion die includes:

[0115] Pre-forming zone: Temperature 80℃, apply 5MPa linear pressure to the fiber-resin system to remove air bubbles and allow the composite to be initially formed;

[0116] Main curing zone: Temperature 120℃, radial pressure 12MPa applied, traction speed 0.6m / min, the main curing reaction of the resin matrix liquid occurs in this zone;

[0117] Shaping and post-curing zone: Temperature 90℃, maintain holding pressure 8MPa to complete the final shaping and further curing of the resin matrix liquid;

[0118] Profile output: The sleeper profile is cooled to below 40°C at a rate of 15°C / s by a water cooling system to obtain a composite structure of reinforced core layer and resin matrix.

[0119] The preparation process of the hydrophobic coating includes the following steps:

[0120] F1. Surface pretreatment: The outer surface of the resin matrix layer is treated with oxygen plasma at a power of 150W for 2 minutes.

[0121] F2. Preparation of fluorosilane solution: Dissolve fluorosilane in tetrahydrofuran to prepare a 1wt% solution. Stir at 250 rpm, add 0.08wt% tetrabutyl titanate as a crosslinking promoter, and ultrasonically disperse at 28kHz, 150W, for 5-8 min.

[0122] F3. Spraying process: Selective spraying is carried out using a spray gun, with a spraying pressure of 0.3MPa, and three sprayings are applied. The thickness of each spray is 30μm, and the interval between sprayings is 12min.

[0123] F4. Low temperature curing: Curing with hot air at 60℃ for 3 hours.

[0124] The TiO2@polydopamine core-shell structure consists of an anatase TiO2 core and a polydopamine shell, and is grafted onto the resin molecular chain using KH-550 silane coupling agent. Its preparation includes the following steps:

[0125] H1. Anatase TiO2 nanoparticles with a particle size of 60 nm were synthesized by sol-gel method, and high-purity products were obtained after centrifugation, washing and drying.

[0126] H2. The anatase TiO2 nanoparticles were dispersed in a Tris-HCl buffer solution with a concentration of 50 mM and a pH of 8.5. After ultrasonic treatment for 35 min, dopamine hydrochloride was added to make the mass ratio of dopamine to anatase TiO2 nanoparticles 2:1. The mixture was stirred magnetically at room temperature in the dark for 24 h to promote the in-situ polymerization of polydopamine on the TiO2 surface to form a shell.

[0127] H3. After the reaction was completed, TiO2@polydopamine core-shell nanoparticles with a shell thickness of 12 nm were obtained by centrifugation and washing with deionized water and ethanol alternately 4 times. The drying temperature was controlled at 60℃ for 12 h.

[0128] H4. The TiO2@polydopamine core-shell nanoparticles obtained in H3 were redispersed in anhydrous ethanol or toluene and sonicated for 35 min. Then, KH-550 silane coupling agent equivalent to 5% of the mass of TiO2@polydopamine core-shell nanoparticles was added and reacted at 80 °C for 6 h under an inert atmosphere to allow KH-550 to condense with the phenolic hydroxyl or amino groups on the surface of polydopamine to form a surface grafted structure.

[0129] H5. After centrifugation and washing with ethanol four times, the product was vacuum dried at 70℃ for 12h to obtain TiO2@polydopamine core-shell nanoparticles grafted with KH-550.

[0130] Example 3:

[0131] The one-piece molded, paint-free, high-performance composite material sleeper comprises a reinforcing core layer, a resin matrix layer, and a hydrophobic coating, wherein:

[0132] The reinforcing core layer is composed of basalt fibers and carbon fibers arranged in an oriented manner, forming a multi-layer fiber structure through a multi-axial guiding system;

[0133] The resin matrix layer has a cuboid structure; the reinforcing core layer is uniformly embedded in the resin matrix layer;

[0134] A hydrophobic coating with a thickness of 75 μm completely covers the outer surface of the resin matrix layer;

[0135] Core layer preparation:

[0136] C1. Fiber pretreatment: 69 parts of basalt fiber and 23 parts of carbon fiber were dried at 80℃ for 4 hours.

[0137] C2. Reinforcing Core Layer Forming: Eight layers of basalt fiber and two layers of carbon fiber are continuously laid at a 3:1 mass ratio using a multi-axial guiding system (fiber tension 80N), with the fiber direction of each layer parallel to the long axis of the sleeper. The specific layup sequence of the multi-layer fiber structure consisting of eight layers of basalt fiber and two layers of carbon fiber is: [C / B / B / B / B / B / B / B / B / C]. Here, C represents the carbon fiber layer and B represents the basalt fiber layer, and this layup sequence is a top-to-bottom or outside-to-inside stacking order. This is a symmetrical layup structure.

[0138] The preparation of the resin matrix layer includes the following steps:

[0139] S1. Synthesis of furan-modified polyurethane: 110 parts of polyurethane were tested and found to have an isocyanate group (-NCO) content of 3.5 wt%. Based on the -NCO content, the corresponding furan methylamine was added to make the equivalent ratio of isocyanate group to amine group 1:1.0. After mixing, the mixture was reacted at 65℃ for 6 h to obtain furan-modified polyurethane.

[0140] S2. Mixing of dynamic crosslinking agent and functional additives: Add 15 parts of bismaleimide, 5 parts of graphene oxide, and 4 parts of TiO2@polydopamine core-shell structure to the product in sequence. Degas at 65℃ for 40 min, and mechanically stir at 700 rpm for 25 min to achieve uniform dispersion.

[0141] S3. Add microcapsules: Add 8 parts of microcapsules and mix by ultrasonic dispersion at a frequency of 40kHz, a power of 300W, and a time of 15min to obtain a resin matrix liquid.

[0142] The integration process between the reinforcing core layer and the resin matrix layer includes the following steps:

[0143] T1. Continuous fiber supply and resin impregnation: The reinforcing core layer is continuously introduced into the resin matrix liquid obtained in step S3 and impregnated for 4 min under a vacuum degree ≤100Pa.

[0144] T2. Extrusion Molding and Gradient Curing: The impregnated reinforcing core layer and resin matrix liquid are introduced into a three-stage temperature-controlled extrusion die, wherein the three-stage temperature-controlled extrusion die includes:

[0145] Pre-forming zone: Temperature 90℃, apply 8MPa linear pressure to the fiber-resin system to remove air bubbles and allow the composite to be initially formed;

[0146] Main curing zone: Temperature 130℃, radial pressure 15MPa applied, traction speed 0.6m / min, the main curing reaction of the resin matrix liquid occurs in this zone;

[0147] Shaping and post-curing zone: Temperature 100℃, maintaining a holding pressure of 10MPa to complete the final shaping and further curing of the resin matrix liquid;

[0148] Profile output: The sleeper profile is cooled to below 40°C at a rate of 15°C / s by a water cooling system to obtain a composite structure of reinforced core layer and resin matrix.

[0149] The preparation process of the hydrophobic coating includes the following steps:

[0150] F1. Surface pretreatment: Oxygen plasma treatment is performed on the outer surface of the resin matrix layer at a power of 200W for 3 minutes.

[0151] F2. Preparation of fluorosilane solution: Dissolve fluorosilane in tetrahydrofuran to prepare a 1wt% solution. Stir at 200 rpm, add 0.05wt% tetrabutyl titanate as a crosslinking promoter, and ultrasonically disperse at 26kHz, 130W, for 5 min.

[0152] F3. Spraying process: Selective spraying is carried out using a spray gun, with a spraying pressure of 0.2MPa, and three sprayings are applied. The thickness of each spray is 25μm, and the interval between sprayings is 10min.

[0153] F4. Low temperature curing: Curing with hot air at 70℃ for 4 hours.

[0154] The microcapsules have a particle size of 30 μm, the wall material of the microcapsules is polyurea formaldehyde, and the core of the microcapsules is bismaleimide monomer.

[0155] The TiO2@polydopamine core-shell structure consists of an anatase TiO2 core and a polydopamine shell, and is grafted onto the resin molecular chain using KH-550 silane coupling agent. Its preparation includes the following steps:

[0156] H1. Anatase TiO2 nanoparticles with a particle size of 50 nm were synthesized by sol-gel method, and high-purity products were obtained after centrifugation, washing and drying.

[0157] H2. The anatase TiO2 nanoparticles were dispersed in a Tris-HCl buffer solution with a concentration of 30 mM and a pH of 8.2. After ultrasonic treatment for 30 min, dopamine hydrochloride was added to make the mass ratio of dopamine to anatase TiO2 nanoparticles 1.5:1. The mixture was magnetically stirred at room temperature in the dark for 18 h to promote the in-situ polymerization of polydopamine on the TiO2 surface to form a shell.

[0158] H3. After the reaction was completed, TiO2@polydopamine core-shell nanoparticles with a shell thickness of 10 nm were obtained by centrifugation and washing with deionized water and ethanol three times alternately. The drying temperature was controlled at 55℃ for 8 hours.

[0159] H4. The TiO2@polydopamine core-shell nanoparticles obtained in H3 were redispersed in anhydrous ethanol or toluene and sonicated for 30 min. Then, KH-550 silane coupling agent equivalent to 2% of the mass of TiO2@polydopamine core-shell nanoparticles was added, and the reaction was carried out at 75 °C for 5 h under an inert atmosphere, so that KH-550 condensed with the phenolic hydroxyl or amino groups on the surface of polydopamine to form a surface grafted structure.

[0160] H5. After centrifugation and washing with ethanol three times, the product was vacuum dried at 75℃ for 10h to obtain TiO2@polydopamine core-shell nanoparticles with KH-550 grafted on the surface.

[0161] Comparative Examples 1-8:

[0162] Comparative Example 1: Compared with Example 1, the difference is that the mass ratio of basalt fiber to carbon fiber in the reinforcing core layer is changed to 1:1 (45 parts of basalt fiber and 45 parts of carbon fiber).

[0163] Comparative Example 2: No bismaleimide dynamic crosslinking agent was added to the resin matrix.

[0164] Comparative Example 3: No TiO2@polydopamine core-shell structure additive was added to the resin matrix.

[0165] Comparative Example 4: The hydrophobic coating was applied in a single spray and without tetrabutyl titanate catalysis.

[0166] Comparative Example 5: The microcapsule wall material was changed to polyvinyl alcohol (PVA).

[0167] Comparative Example 6: The grafting step with KH-550 silane coupling agent was omitted.

[0168] Test Example 1:

[0169] The fiber content test shall be conducted in accordance with GB / T 2577.

[0170] The apparent total density test was conducted in accordance with GB / T6343.

[0171] The water absorption test shall be conducted in accordance with GB / T1462.

[0172] The flame retardancy test shall be conducted according to Test Method A—Horizontal Burning Test as specified in GB / T2408.

[0173] The breakdown voltage test shall be performed according to the parallel plate electrode in GB / T1408.1.

[0174] Surface resistivity testing shall be conducted in accordance with GB / T1410, with a sample quantity of 5, and the test results shall be the arithmetic mean.

[0175] The average linear expansion coefficient test shall be carried out in accordance with GB / T2572.

[0176] Surface hardness testing was performed according to the Type D Shore hardness tester method in GB / T2411.

[0177] Table 1. Physical Performance Test Data Test Project Example 1 Example 2 Example 3 Fiber mass content (%) 62.3 59.8 64.7 Apparent total density (kg / m³) 1198 1145 1253 Water absorption (%) 3.5 4.9 2.6 Flame retardancy HB HB HB Breakdown voltage (kV / mm) 21.6 19.8 24.3 Surface resistivity (Ω·cm) <![CDATA[2.8×10 10 ]]> <![CDATA[9.5×10 10 ]]> <![CDATA[4.7×10 10 ]]> Average linear expansion coefficient (1 / ℃) <![CDATA[0.85×10 -5 ]]> <![CDATA[1.02×10 -5 ]]> 0.63×10-5 Surface hardness (Shore D) 57 52 61

[0178] The sleeper material of this invention achieves comprehensive optimization of its basic physical properties through multi-level fiber synergistic reinforcement and dynamic network construction. Basalt fiber and carbon fiber are alternately laid in a specific ratio (3:1), combined with a molding and orientation process, ensuring that the fiber mass content is consistently above 60%, and the apparent density is precisely controlled at 1200±60 kg / m³. 3 Within the specified range, the parallel axial arrangement of the fibers effectively enhances the density of the core structure, thereby significantly improving bending stiffness and suppressing water absorption (≤4.9%). This is closely related to the compatibilizing effect of hydrogen bonds through graphene oxide at the fiber / resin interface, and the surface resistivity of all fibers reaches 1×10⁻⁶. 10 With a strength of Ω·cm or higher, it ensures the anti-static requirements in railway scenarios.

[0179] The synergistic effect of the dynamic cross-linked resin matrix and nano-additives further enhances the environmental stability of the material. The furan-bismaleimide dynamic network not only adjusts the coefficient of linear expansion through reversible bonding, but also maintains the integrity of the interface by releasing repair monomers through microcapsules, resulting in a water absorption as low as 2.6% to 3.5%.

[0180] The TiO2@polydopamine core-shell structure plays a key role in ultraviolet shielding and photocatalytic degradation of pollutants. Combined with the hydrophobic treatment of the fluorosilane coating, the surface hardness of the material reaches Shore D50 or higher, and the flame retardancy is stable at HB level, meeting the requirements for long-term service under complex climatic conditions.

[0181] The phased curing and precise functional layer integration technology ensures performance balance. Low-temperature extrusion (80-90℃) avoids fiber damage while vacuum impregnation allows the resin to fully wet the fiber gaps. Directional spraying and plasma pretreatment optimize the bonding strength of the functional layers, and the breakdown voltage is increased to 19.8-24.3kV / mm.

[0182] This invention achieves a breakthrough in the comprehensive performance of railway sleeper materials, characterized by high strength, low moisture absorption, and high weather resistance, through the deep coupling of component design and process control.

[0183] Test Example 2: Explanation of Mechanical Property Comparison Experiment

[0184] The difference in mechanical properties between Example 1 (basalt fiber: carbon fiber = 3:1) and Comparative Example 1 (1:1) was verified to clarify the necessity of fiber ratio optimization.

[0185] Experimental steps:

[0186] Sample preparation: Standard samples (size: 100mm×15mm×4mm) were cut from the core layer of the finished sleepers of Example 1 and Comparative Example 1, with 5 parallel samples in each group.

[0187] Bending strength and modulus of elasticity testing: A three-point bending test (ASTM D790) was used, with a span of 80 mm and a loading rate of 2 mm / min. The maximum load and displacement curves were recorded, and the bending strength (σ = 3FL / 2bh) was calculated. 2 ) and elastic modulus (E=Δσ / Δε).

[0188] Vertical compressive strength test: The axial compression test (ASTM D695) was adopted. The specimen was in vertical contact with the pressure plate (10mm × 10mm), the loading rate was 1.5mm / min, the compression failure load was recorded, and the compressive strength (σ=F / A) was calculated.

[0189] Shear strength test: Short beam shear test (ASTM D2344) was used with a span of 40 mm and a loading rate of 1 mm / min. The interlaminar shear strength was calculated (τ = 3F / 4bh).

[0190] Data processing: Remove outliers (deviation > 15%) and take the arithmetic mean of the remaining samples.

[0191] Table 2. Comparison of Mechanical Properties Test Data Test Project Example 1 Comparative Example 1 Bending strength (MPa) 208.3 185.7 Flexural modulus (GPa) 13.1 10.8 Vertical compressive strength (MPa) 126.5 112.2 Shear strength (MPa) 19.3 16.5

[0192] This invention utilizes a 3:1 basalt / carbon fiber ratio for cross-scale mechanical coupling, significantly improving the load-bearing capacity and deformation resistance of railway sleepers. The high-modulus skeleton of basalt fiber bears the main load, while carbon fiber inhibits crack propagation through bridging. The two work synergistically to optimize stress distribution, resulting in a flexural strength of 208 MPa, exceeding Comparative Example 1 (185 MPa) by 12.3%. The interfacial compatibilization effect of graphene oxide further strengthens the fiber / resin bond, increasing shear strength by 17.0%, verifying the irreplaceable nature of fiber type and ratio design. The mechanical properties of Comparative Example 1 are comprehensively lower than those of Example 1, demonstrating that deviation from the 3:1 ratio leads to material performance degradation, failing to meet the high load-bearing requirements of railway sleepers.

[0193] Test Example 3: Self-Healing Performance Comparison Test

[0194] Experimental steps:

[0195] Pre-cracked specimens: Specimens (size: 50mm×10mm×4mm) were cut from the surface of the finished sleepers of Example 1, Comparative Example 2, and Comparative Example 5. Three parallel specimens were made in each group. A single-sided notch (depth 2mm, width 0.2mm) was pre-made in the middle of the specimen using a blade.

[0196] Self-healing treatment: The sample was placed in an 80℃ oven and heated for 2 hours to trigger microcapsule rupture and dynamic network reconstruction. Another sample from the same batch was not treated and served as a blank control.

[0197] Repair efficiency test: Three-point bending strength recovery rate was used.

[0198] operate:

[0199] Test the flexural strength (σ0) of the original specimen (without cracking).

[0200] The initial bending strength (σ1) of the pre-cracked specimen was tested.

[0201] The repair strength (σ2) was tested after the repair.

[0202] Calculation: Repair efficiency (%) = (σ2 - σ1) / (σ1 - σ0) × 100

[0203] Microcapsule release rate testing: Thermogravimetric analysis (TGA) combined with differential scanning calorimetry (DSC) was used.

[0204] Procedure: Take 20 mg of microcapsule powder, heat it to 200 °C at 10 °C / min, and analyze the core release initiation temperature and weight loss rate.

[0205] Table 3. Self-healing performance comparison test data. Test Project Example 1 Comparative Example 2 Comparative Example 5 Repair efficiency (%) 82.3 18.5 49.7 Microcapsule release initiation temperature (°C) 75.6 - 92.4 Bending strength after repair (MPa) 185.2 132.7 153.8 Microcapsule weight loss rate (%) 68.5 - 41.2

[0206] The above data show the difference in self-healing ability between Example 1 and Comparative Examples 2 and 5.

[0207] The dynamic covalent network of this invention works synergistically with polyurea-formaldehyde microcapsules to achieve a highly efficient self-healing function. The furan-bismaleimide dynamic bond is reversibly broken / recombined at 80°C, repairing the chemical bonds at the interface. The polyurea-formaldehyde wall material responds precisely to temperature changes and releases the repair agent in a controllable manner at 75.6°C. Its weight loss rate (68.5%) indicates that the core is used efficiently.

[0208] Comparative Example 2, lacking a dynamic network, relied solely on physical filling with microcapsules, resulting in a repair efficiency of less than 20%. Comparative Example 5's PVA wall material suffered from poor thermal stability (release temperature 92.4℃), leading to premature release of the repair agent and low utilization. Experimental data demonstrate that the synergistic design of the dynamic network and microcapsules is a necessary condition for achieving self-healing performance, overcoming the limitations of traditional single-mechanism repair methods.

[0209] Test Example 4: Weather Resistance Comparison

[0210] Experimental steps:

[0211] Aging condition simulation:

[0212] UV aging: Following ASTM G154, a UVA-340 lamp (0.76W / m²) was used. 2 @340nm), 1000h of cyclic irradiation (8h irradiation / 4h condensation, 60℃).

[0213] Salt spray aging: Refer to ASTM B117, 5% NaCl solution is continuously sprayed for 480 hours (35℃).

[0214] Damp heat aging: Refer to ASTM D5229, place in an environment of 85℃ / 85%RH for 720 hours.

[0215] Sample preparation: Standard samples (size: 100mm×15mm×4mm) were cut from the finished sleepers of Example 1 and Comparative Example 3, with 3 parallel samples for each aging condition.

[0216] Post-aging performance testing:

[0217] Bending strength and modulus of elasticity: Three-point bending test (ASTM D790), span 80 mm, loading rate 2 mm / min.

[0218] Vertical compressive strength: Axial compression test, loading rate 1.5 mm / min.

[0219] Bond shear strength: lap shear test, aluminum plate bonded specimen, tensile rate 1.3 mm / min.

[0220] Performance retention rate calculation: Retention rate (%) = (strength after aging / original strength) × 100.

[0221] Table 4. Weather Resistance Test Data

[0222] The data above show that Example 1 has higher performance stability after UV, salt spray and damp heat aging compared with Comparative Example 3.

[0223] The TiO2@polydopamine core-shell structure of this invention significantly improves the weather resistance of the material through a dual mechanism of ultraviolet shielding and interface protection. TiO2 nanoparticles absorb ultraviolet light and catalyze the degradation of pollutants, while the polydopamine adhesion layer inhibits the penetration of moisture and corrosive ions. This results in Example 1 exhibiting a mechanical property retention rate of ≥80% after ultraviolet, salt spray, and damp heat aging. Comparative Example 3, lacking this structure, experienced photo-oxidative degradation of the resin matrix and hygroscopic expansion at the interface, leading to a significant decrease in its performance retention rate to the 60%–73% range, a reduction of approximately 15–25 percentage points compared to Example 1. This verifies the crucial role of the nano-core-shell design in adapting to complex environments.

[0224] Test Example 5: Comparison of Hydrophobic Coating Performance

[0225] Experimental steps:

[0226] Contact angle test: The static drop method (ASTM D7334) was used. 5 μL of deionized water was dropped onto the coating surface, and the droplet morphology was recorded by a high-speed camera. The static contact angle was calculated (the average of 3 measurements was taken).

[0227] Abrasion resistance test: The sandpaper abrasion method (ASTM D4060) was used.

[0228] Procedure: The sample is fixed in the friction testing machine with a load of 500g and rubbed 1000 times with 800-grit sandpaper at a speed of 50mm / s. The mass difference before and after friction is measured, and the mass loss rate (mg / cycle) is calculated.

[0229] Coating thickness measurement: A non-contact laser thickness gauge was used. The thickness was measured at 5 points on the coating surface, and the average value was taken after removing outliers.

[0230] Adhesion test: Cross-cut test (ASTM D3359). A 1mm × 1mm grid is cut with a blade, 3M tape is applied and peeled vertically, the area of ​​coating peeling is observed and rated (0B-5B, 5B is no peeling).

[0231] Chemical resistance test: The acid-base immersion method (ISO2812) was used. The sample was immersed in H2SO4 solution with pH=2 and NaOH solution with pH=12 for 24 hours each. After rinsing and drying, the surface blistering and peeling phenomena were observed.

[0232] Table 5. Comparison Test Data of Hydrophobic Coating Performance Test Project Example 1 Comparative Example 4 Static contact angle (°) 153.2 128.7 Abrasion resistance mass loss (mg) 4.8 12.3 Coating thickness (μm) 59.2 9.7 Adhesion rating (0B-5B) 5B 2B Contact angle retention rate after acid resistance (%) 89.4 63.2 Contact angle retention rate after alkali resistance (%) 91.7 68.5

[0233] As can be seen from the data above, compared with Comparative Example 4, the hydrophobic coating of Example 1 shows significant advantages in terms of hydrophobicity, abrasion resistance, adhesion and chemical resistance.

[0234] The multi-coating process of this invention, combined with tetrabutyl titanate catalysis, achieves a balance between high hydrophobicity and wear resistance through gradient film formation and chemical crosslinking optimization. Plasma pretreatment and KH-550 coupling agent enhance the coating / substrate interface bonding, resulting in a low mass loss of only 4.8 mg after friction and an adhesion rating of 5B. Tetrabutyl titanate catalyzes the hydrolysis and condensation of fluorosilanes, forming a dense three-dimensional network, increasing the contact angle to 153.2°, and achieving a retention rate of >89% after acid and alkali immersion. Comparative Example 4, due to process simplification, resulted in a loose and porous coating, verifying the irreplaceable nature of multi-coating and the catalyst. Its performance degradation demonstrates the crucial role of the process design of this invention in the stability of the functional layer.

[0235] Test Example 6: Nanoparticle Dispersion and Interfacial Properties

[0236] Experimental steps:

[0237] Repair agent release rate test: Spectrophotometry was used (refer to GB / T23986).

[0238] Procedure: Immerse the sample containing microcapsules in 50 mL of ethanol and shake at 25 °C (200 rpm); take 1 mL of solution every 10 min and detect the concentration of the repair agent using a UV spectrophotometer (λ=280 nm) and plot the release curve.

[0239] Repair efficiency test: The crack closure rate and strength recovery rate are used for comprehensive evaluation.

[0240] operate:

[0241] Pre-crack: Cut a standard crack (10 mm long and 1 mm deep) on the surface of the sample.

[0242] Repair treatment: Heating at 80℃ for 2 hours to trigger microcapsule rupture.

[0243] Crack closure rate: Crack width change (%) measured by microscope = (initial width - width after repair) / initial width × 100.

[0244] Strength recovery rate: The ratio (%) of the repaired strength to the original strength as determined by the three-point bending test (ASTM D790).

[0245] Solvent resistance test of microcapsules: The solvent immersion method was used. The microcapsule powder was immersed in acetone for 24 hours, filtered, dried, and weighed. The mass loss rate (%) was calculated.

[0246] Table 6. Test data on the repair performance of microcapsules Test Project Example 1 Comparative Example 5 Repair agent release rate (30 min, %) 78.3 92.5 Crack closure rate (%) 84.7 63.2 Strength recovery rate (%) 81.5 58.9 acetone resistance of microcapsules - mass loss rate (%) 12.4 38.7 Release equilibrium time (min) 45 20

[0247] The data above show that, in terms of both the release behavior of the repair agent and the final repair effect, Example 1, which uses polyurea formaldehyde wall material, is significantly better than Comparative Example 5, which uses PVA wall material.

[0248] The polyurea-formaldehyde wall material of this invention achieves controlled and sustained release of the repair agent through hydrophobic modification and crosslinking density regulation. Its dense structure delays ethanol penetration, controlling the release rate to 78.3% within 30 minutes, ensuring uniform diffusion of the repair agent in the crack area, with crack closure rate and strength recovery rate reaching 84.7% and 81.5%, respectively. In contrast, the PVA wall material of Comparative Example 5, due to its strong hydrophilicity and poor solvent resistance, experienced premature release of the repair agent (92.5%) and severe degradation in the solvent, leading to a significant deterioration in repair performance. Experimental data demonstrate that the design of the polyurea-formaldehyde wall material is key to its long-term stable repair function, overcoming the technical bottleneck of uncontrollable release in traditional wall materials.

[0249] Test Example 7: The Impact of Interface Grafting (KH-550) on Dynamic Network Performance

[0250] Experimental steps:

[0251] Self-healing cycle test: Multi-cycle repair efficiency verification was performed (refer to ASTM D790).

[0252] operate:

[0253] Pre-fabricated standard crack: Cut a single-sided notch (15mm long, 2mm deep) on the surface of the specimen.

[0254] Repair treatment: Heating at 80℃ for 2 hours triggers dynamic network reconstruction, and after cooling to room temperature, the bending strength recovery rate is tested.

[0255] Repeat step 2 for 3 cycles of repair and record the recovery rate for each cycle.

[0256] Stress relaxation test: The constant strain relaxation test (ASTM D6048) was used.

[0257] Procedure: Stretch the specimen to 5% strain and hold, record the stress decay curve within 30 minutes; calculate the relaxation rate (%) = (initial stress - residual stress) / initial stress × 100.

[0258] Low-temperature toughness test: Notched impact test (ASTM D6110).

[0259] Procedure: Pre-treat the sample at -20℃ for 4 hours; impact the V-notch sample with a pendulum and record the impact absorbed energy (kJ / m²). 2 ).

[0260] Table 7 Test Data on the Impact of Interface Grafting on Dynamic Network Performance Test Project Example 1 Comparative Example 6 Initial repair efficiency (%) 84.3 72.6 Third repair efficiency (%) 78.5 53.2 Stress relaxation rate (%) 22.7 38.4 <![CDATA[-20 °C impact energy absorption (kJ / m 2 )]]> 5.8 6.9

[0261] The data above show that Example 1, which uses KH-550 for interface grafting, is significantly better than Comparative Example 6, which does not undergo grafting, in terms of cyclic repair stability and stress relaxation performance.

[0262] Data demonstrates that the interfacial grafting of KH-550 is crucial for ensuring the long-term stability of the dynamic network and achieving efficient cyclic self-healing. Through KH-550, a strong interfacial bond is formed between the inorganic filler and the polymer matrix, effectively anchoring the entire dynamic cross-linked network. This highly integrated and robust network structure significantly limits the disordered slippage of chain segments, resulting in a lower stress relaxation rate (22.7%). Furthermore, it ensures the network maintains structural integrity during multiple thermal repair cycles, maintaining a repair efficiency of up to 78.5% after three cycles. This strong interfacial interaction also alters the energy absorption and transfer mechanism of the material under impact loads, ultimately achieving structural stability and cyclic repair durability—crucial for the long-term reliability of railway sleepers.

[0263] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An integrated, paint-free, high-performance composite material railway sleeper, characterized in that: It includes a reinforcing core layer, a resin matrix layer, and a hydrophobic coating, wherein: The reinforcing core layer is composed of basalt fibers and carbon fibers arranged in an oriented manner, forming a multi-layer fiber structure through a multi-axial guiding system; The resin matrix layer has a cuboid structure; the reinforcing core layer is uniformly embedded in the resin matrix layer; The hydrophobic coating completely covers the outer surface of the resin matrix layer with a thickness of 60-90μm.

2. The integrated molded, paint-free, high-performance composite material sleeper according to claim 1, characterized in that, The reinforcing core layer comprises, by weight, 60-70 parts of basalt fiber and 20-30 parts of carbon fiber, with a mass ratio of 3:1 between the two fibers. The resin matrix layer comprises, by weight, 90-110 parts of polyurethane, 10-15 parts of bismaleimide dynamic crosslinking agent, 3-5 parts of graphene oxide, 2-4 parts of TiO2@polydopamine core-shell structure additive, and 5-8 parts of microcapsules. The hydrophobic coating: covers the outer surface of the resin matrix layer and contains 0.5 to 1.0 parts by weight of fluorosilane.

3. The integrated molded, paint-free, high-performance composite material sleeper according to claim 1, characterized in that, The bismaleimide dynamic crosslinking agent is formed by the Diels-Alder reaction of furan-modified polyurethane and bismaleimide.

4. The integrated molded, paint-free, high-performance composite material sleeper according to claim 1, characterized in that, The process for preparing the reinforced core layer includes the following steps: C1. Fiber pretreatment: Basalt fiber and carbon fiber are placed in a drying oven and dried at 60-80℃ for 2-4 hours to remove surface moisture; C2. The pretreated basalt fiber and carbon fiber are continuously supplied and compounded into a multi-layer fiber structure through a multi-axial guiding and tension control system at a mass ratio of 3:1 and a preset fiber layer direction to form a reinforcing core layer.

5. The integrated molded, paint-free, high-performance composite material sleeper according to claim 2, characterized in that, The microcapsules have a particle size of 20-50 μm, the wall material of the microcapsules is polyurea formaldehyde, and the core of the microcapsules is bismaleimide monomer.

6. The integrated molded, paint-free, high-performance composite material sleeper according to claim 2, characterized in that, The preparation of the resin matrix layer includes the following steps: S1. Synthesis of furan-modified polyurethane: Polyurethane and furan methylamine are mixed at an isocyanate group:amine equivalent ratio of 1:0.8 to 1:1 and reacted at 60-65℃ for 4-6 hours to obtain furan-modified polyurethane. S2. Mixing of dynamic crosslinking agent and functional additives: Bismaleimide, graphene oxide, and TiO2@polydopamine core-shell structure are added sequentially to the product of step S1. Vacuum degassing is performed at 50-60℃ for 30-40 min, followed by mechanical stirring at 500-800 rpm for 20-30 min to achieve uniform dispersion. S3. Add microcapsules: Add microcapsules and mix by ultrasonic dispersion at a frequency of 40kHz, a power of 200-300W, and a time of 10-15min to obtain a resin matrix liquid.

7. The integrated molded, paint-free, high-performance composite material sleeper according to claim 6, characterized in that, The integration process of the reinforced core layer and the resin matrix layer includes the following steps: T1. Continuously introduce the reinforcing core layer into the resin matrix liquid obtained in step S3, and impregnate for 3 to 5 minutes under a vacuum degree ≤100Pa. T2. The impregnated reinforced core layer and resin matrix liquid are introduced into a three-stage temperature-controlled extrusion die, wherein the three-stage temperature-controlled extrusion die includes: Pre-forming zone: Temperature 80-90℃, apply 5-8MPa linear pressure to the fiber-resin system to remove air bubbles and allow the composite to be initially formed; Main curing zone: Temperature 120-130℃, radial pressure 12-15MPa applied, traction speed 0.5~1.2m / min, the main curing reaction of the resin matrix liquid occurs in this zone; Shaping and post-curing zone: Temperature 90-100℃, maintain holding pressure 8-10MPa to complete the final shaping and further curing of the resin matrix liquid; Profile output: The sleeper profile is cooled to below 40°C at a rate of 10-15°C / s by a water cooling system to obtain a composite structure of reinforced core layer and resin matrix liquid.

8. The integrated molded, paint-free, high-performance composite material sleeper according to claim 2, characterized in that, The preparation process of the hydrophobic coating includes the following steps: F1. Surface pretreatment: Oxygen plasma treatment is performed on the outer surface of the resin matrix layer, with a power of 150-200W and a time of 2-3 minutes; F2. Preparation of fluorosilane: Dissolve fluorosilane in tetrahydrofuran to prepare a 1-2 wt% solution, stir at 200-300 rpm, add 0.05-0.1 wt% tetrabutyl titanate as a crosslinking promoter, and ultrasonically disperse at a frequency of 26-30 kHz, a power of 130-170 W, and a time of 5-8 min. F3. Spraying process: Selective spraying is carried out using a spray gun, with a spraying pressure of 0.2-0.4MPa, and three sprayings are applied. The thickness of each spray is 20-30μm, and the interval between sprayings is 10-15min. F4. Low temperature curing: Curing with hot air at 60-70℃ for 3-4 hours.

9. The integrated molded, paint-free, high-performance composite material sleeper according to claim 2, characterized in that, The TiO2@polydopamine core-shell structure consists of an anatase TiO2 core and a polydopamine shell, and is grafted onto the resin molecular chain using KH-550 silane coupling agent. Its preparation includes the following steps: H1. Anatase TiO2 nanoparticles with a particle size of 40-60 nm were synthesized by sol-gel method, and high-purity products were obtained after centrifugation, washing and drying. H2. The anatase TiO2 nanoparticles were dispersed in Tris-HCl buffer solution, ultrasonicated for 25-35 min, and then dopamine hydrochloride was added. The mixture was stirred magnetically at room temperature in the dark for 12-24 h to promote the in-situ polymerization of polydopamine on the TiO2 surface to form a shell. H3. After the reaction is completed, the particles are separated by centrifugation and washed with deionized water and ethanol alternately 3 to 4 times. The drying temperature is controlled at 50 to 60°C and the time is 6 to 12 hours to obtain TiO2@polydopamine core-shell nanoparticles with a shell thickness of 8 to 12 nm. H4. The TiO2@polydopamine core-shell nanoparticles obtained in H3 are redispersed in anhydrous ethanol or toluene and ultrasonically treated for 25-35 min. Then, KH-550 silane coupling agent equivalent to 2% of the mass of TiO2@polydopamine core-shell nanoparticles is added. The reaction is carried out at 70-80℃ for 4-6 h under an inert atmosphere, so that KH-550 condenses with the phenolic hydroxyl or amino groups on the surface of polydopamine to form a surface grafted structure. H5. After centrifugation and washing with ethanol 3-4 times, the product was vacuum dried at 60-70℃ for 6-12 hours to obtain TiO2@polydopamine core-shell nanoparticles grafted with KH-550.

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