Large-size synthetic sleeper and forming method

Abstract

The application provides a large-size synthetic sleeper and a forming method, and the forming method comprises the following steps: S1, surface pretreatment of a synthetic sleeper semi-finished product; S2, coating of an adhesive; S3, combination and sealing: first, the synthetic sleeper after the coating of the adhesive is combined in position to form a combination; then, the combination is placed in a sealed vacuum bag film system, and the vacuum bag film system forms a sealed cavity; S4, vacuum-assisted bonding and curing: first, the sealed cavity is vacuumized, and the pressure in the cavity is extracted to a vacuum state with a relative atmospheric pressure of-0.1 MPa to-0.09 MPa before the adhesive is gelled; then, the vacuum state is maintained for greater than or equal to 12 hours at room temperature or under heating, the adhesive is gelled first and then solidified to form a bonding layer; and S5, post-treatment. The forming method of the large-size synthetic sleeper has the advantages of uniform pressure, elimination of bubble and cavity defects in the bonding layer, no need of large equipment and tooling, and high bonding quality and production efficiency.

Description

Technical Field

[0001] This invention relates to the field of rail transit materials technology, and more specifically, to a large-size synthetic sleeper and its molding method. Background Technology

[0002] Traditional railway sleepers are mostly made of wood or prestressed concrete. Wooden sleepers are prone to corrosion, have a short lifespan, and consume forest resources; concrete sleepers are heavy, have poor insulation performance, and require high-quality track foundations. Polyurethane foam composite sleepers are composite material sleepers made of glass fiber reinforced rigid polyurethane foam, often simply called composite sleepers. Due to their advantages such as light weight, high toughness, corrosion resistance, excellent insulation performance, and ease of processing and molding, they have become an important development direction for the next generation of sleepers. Currently, composite sleepers in general applications are basically molded in one piece. However, for large-sized composite sleepers used in special applications, with lengths of 9000~12000mm, widths of 400~800mm, and heights of 300~600mm, existing manufacturing technologies cannot produce them in one piece. They all require bonding in the width or height direction, or even bonding in both directions simultaneously, to manufacture the required large-sized composite sleepers.

[0003] Composite railway sleepers are relatively large, and existing bonding technologies generally rely on mechanical pressure methods such as hydraulic, pneumatic, and bolt tightening for bonding. Batch bonding requires numerous bonding fixtures or pressurizing equipment, resulting in significant equipment investment. Furthermore, these pressurizing devices typically apply pressure only to specific areas, failing to pressurize the entire surface of the product. This leads to pressure differences at different locations, causing significant fluctuations in product performance. In addition, the porous foam structure on the surface of polyurethane composite sleepers makes it easy for air to be trapped during adhesive application, forming localized debonding zones. These zones become stress concentration points and fatigue crack initiation points, severely impacting the sleeper's long-term load-bearing capacity and durability.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to propose a large-size synthetic railway sleeper and its molding method to solve the problems of uneven pressure application and air trapping in the adhesive surface, which leads to poor bonding quality, high production costs, and low efficiency in the existing synthetic railway sleeper bonding methods.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A method for molding a large-size synthetic railway sleeper, the method comprising the following steps:

[0008] S1. Surface pretreatment of semi-finished synthetic sleepers: Pretreatment of the surfaces of at least two pre-formed semi-finished synthetic sleepers;

[0009] S2. Apply adhesive: Apply adhesive to the bonding surface of the pre-treated synthetic sleeper semi-finished product;

[0010] S3. Assembly and Sealing: First, align and assemble the glued synthetic sleeper semi-finished products to form an assembly; then place the assembly in a sealed vacuum bag film system, which is placed on a workbench and forms a closed cavity.

[0011] S4. Vacuum-assisted bonding and curing: Start the vacuum pump and first evacuate the sealed cavity. Before the adhesive gels, the pressure inside the cavity is evacuated to a vacuum state of -0.1MPa to -0.09MPa relative to atmospheric pressure. Then, maintain the vacuum state at room temperature or under heating conditions for ≥12 hours. The adhesive first gels and then cures to form an adhesive layer.

[0012] S5. Post-processing: After curing, turn off the vacuum pump, disassemble the vacuum bag film system, and post-process to obtain the large-size synthetic sleeper.

[0013] Furthermore, in step S4, the vacuum state is maintained under heating conditions, with the heating temperature being 30~60°C.

[0014] Furthermore, the adhesive is one of epoxy resin adhesive, polyurethane adhesive, and vinyl resin adhesive.

[0015] Furthermore, the adhesive has a viscosity of ≤3000 mPa·s at room temperature and a gel time of 30~90 min.

[0016] Furthermore, the adhesive has a viscosity of 1000~2100 mPa·s at room temperature and a gel time of 30~75 min.

[0017] Furthermore, in step S2, a layer of glass fiber mat is laid on the bonding surface before or during the application of the adhesive.

[0018] Furthermore, the glass fiber mat is at least one of stitch-woven mat, continuous mat, and chopped strand mat, and the areal density of the glass fiber mat is 120~600g / m².

[0019] Furthermore, the semi-finished synthetic sleeper is a glass fiber reinforced polyurethane foam synthetic sleeper, and the density of the semi-finished synthetic sleeper is 640~1400 kg / m³. 3 .

[0020] Furthermore, the adhesive is coated at a density of 300~600 g / m² on the bonding surface. 2 .

[0021] A second aspect of the present invention provides a large-size composite sleeper, wherein the large-size composite sleeper is formed using any one of the forming methods for a large-size composite sleeper described in any one of the claims, and the large-size composite sleeper comprises:

[0022] At least two composite sleeper semi-finished products;

[0023] An adhesive layer is located between the at least two composite sleeper semi-finished products;

[0024] The adhesive layer has a dense structure without air bubbles or voids, and a reinforced interface layer is formed at the interface between the adhesive layer and the semi-finished synthetic sleeper.

[0025] Compared with the prior art, the large-size synthetic railway sleeper and its molding method described in this invention have the following advantages:

[0026] 1. Excellent Adhesion Performance: The vacuum environment completely eliminates air bubbles and voids in the adhesive layer, achieving nearly 100% solid bonding area. This significantly improves the adhesive shear strength and flexural strength, ensuring effective load transfer between the sleeper bonding surfaces. Simultaneously, the negative pressure promotes the adhesive penetration into the open pores of the sleeper surface, forming an anchoring-like reinforced interface layer after curing. This further greatly enhances the adhesive shear strength and flexural strength of the bonding interface, ensuring effective load transfer. The addition of a fiberglass mat reinforcement layer further increases the bonding interface strength.

[0027] 2. Suitable for large-size components: The uniform negative pressure provided by vacuum-assisted bonding overcomes the problem of uneven pressure in mechanical bonding, making it particularly suitable for bonding scenarios with long dimensions and large areas, and solving the key process problems in the manufacturing of large-size synthetic sleepers.

[0028] 3. Improved product performance and reliability: The defect-free bonding structure significantly improves the overall stiffness, fatigue life and long-term durability of the sleepers, and reduces the risk of delamination and cracking during use.

[0029] 4. High process controllability and consistency: Process parameters (vacuum degree, time, temperature) are easy to control precisely, reducing the impact of human factors and ensuring stable product quality in mass production.

[0030] 5. Environmental and Economic Benefits: It helps to eliminate harmful volatile organic compounds, improving the working environment. At the same time, high-quality bonding reduces reliance on excessive adhesives and lowers the scrap rate due to bonding defects. Furthermore, vacuum-assisted bonding reduces complex mechanical pressurization devices, decreasing equipment investment and resulting in high overall economic benefits. Attached Figure Description

[0031] Figure 1This is a schematic flowchart of a molding method for a large-size synthetic railway sleeper according to an embodiment of the present invention;

[0032] Figure 2 This is one of the cross-sectional views of a large-size synthetic railway sleeper according to an embodiment of the present invention;

[0033] Figure 3 for Figure 2 Enlarged structural diagram at point A;

[0034] Figure 4 This is a second cross-sectional view of a large-size synthetic railway sleeper according to an embodiment of the present invention.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1. Composite sleeper semi-finished product; 2. Adhesive layer; 3. Reinforcing interface layer. Detailed Implementation

[0037] To make the technical means and objectives and effects of the present invention easier to understand, the embodiments of the present invention will be described in detail below with reference to specific illustrations.

[0038] It should be noted that in the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0039] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0040] In existing technologies, the bonding methods for synthetic sleepers often result in uneven pressure application and air trapping in the adhesive surface, leading to debonding zones and poor bonding quality. This results in high production costs and low efficiency.

[0041] To address the aforementioned technical problems, the applicant proposes a molding method for large-size synthetic railway sleepers, such as... Figure 1 As shown, the molding method includes the following steps:

[0042] S1. Surface pretreatment of semi-finished synthetic sleeper 1: The surface of the formed semi-finished synthetic sleeper 1 is pretreated; the pretreatment includes grinding, cleaning, removing the surface skin and release agent and other smooth layers to increase its surface energy and roughness, improve the wettability of the adhesive, and then cleaning the surface dust.

[0043] S2. Apply adhesive: Apply a layer of adhesive evenly to the bonding surface of the pre-treated synthetic sleeper semi-finished product 1;

[0044] S3. Assembly and Sealing: Based on the dimensions of the composite sleeper, prepare a workbench of corresponding size and clean the surface. Then, cut vacuum bag film of corresponding size, and glue sealing strips to the edges of the vacuum bag film for later use. At the same time, prepare a vacuum tube of the same length as the composite sleeper for subsequent vacuuming. Assemble the glued composite sleeper semi-finished product 1 in alignment and fix it to form an assembly. Then, place the assembly in the flexible vacuum bag film and cover the vacuum tube inside the vacuum bag film. Finally, use sealing strips to tightly seal the edges of the vacuum bag film to the workbench to form a sealed cavity.

[0045] S4. Vacuum-assisted bonding and curing: Connect the vacuum pump to the sealed cavity and vacuum tube, start the vacuum pump, first evacuate the sealed cavity, and before the adhesive gels, evacuate the pressure inside the cavity to a vacuum state of -0.1MPa to -0.09MPa relative to atmospheric pressure; then maintain the vacuum state at room temperature or under heating conditions for ≥12h, the adhesive first gels and then cures to form bonding layer 2, the adhesive forms a dense, defect-free, and strong bonding layer 2 between the bonding surfaces of the synthetic sleeper semi-finished product 1.

[0046] S5. Post-processing: After curing, turn off the vacuum pump, demold, remove the vacuum bag material, and perform necessary repairs, processing and inspections on the synthetic sleeper to obtain the large-size synthetic sleeper.

[0047] Specifically, the vacuum bag film system includes a vacuum bag film and a vacuum tube, with the vacuum tube encased inside the vacuum bag film, and the edge of the vacuum bag film tightly sealed to the workbench surface by a sealing strip.

[0048] Specifically, in step S4, the vacuum state is maintained under heating conditions, and the heating temperature is 30~60°C.

[0049] This setting can reduce adhesive viscosity, promote flow, and accelerate adhesive curing.

[0050] Specifically, the adhesive is one of epoxy resin adhesive, polyurethane adhesive and vinyl resin adhesive.

[0051] All three types of adhesives possess moderate polar group content and good wetting properties, enabling them to effectively penetrate the open pores of the polished synthetic sleeper surface under the vacuum negative pressure conditions described in this invention. They form a strong chemical bond and mechanical interlocking structure with the glass fiber and polyurethane foam matrix. Simultaneously, these adhesives exhibit a suitable viscosity range (≤3000 mPa·s) and adjustable gel time (30~90 min) at room temperature. This ensures sufficient fluidity and permeability during the vacuum-assisted stage, guaranteeing complete removal of air from the bonding interface. Furthermore, after curing, they form a dense, highly tough adhesive layer capable of withstanding dynamic load impacts and fatigue stresses under rail transit conditions. In addition, these adhesives exhibit excellent compatibility with polyurethane foam materials and low curing shrinkage, effectively avoiding the risk of interfacial debonding due to shrinkage stress, thereby ensuring the long-term stability and reliability of the bonding quality of large-size synthetic sleepers.

[0052] Specifically, the adhesive has a viscosity of ≤3000 mPa·s at room temperature and a gel time of 30~90 min.

[0053] The viscosity was measured at room temperature using a rotational viscometer; the gel time test standard is GB / T7123.1-2002 (23±2℃).

[0054] Preferably, the adhesive has a viscosity of 1000~2100 mPa·s at room temperature and a gel time of 30~75 min.

[0055] Specifically, the adhesive is coated at a density of 300~600 g / m² on the bonding surface. 2 .

[0056] Preferably, the adhesive is coated at a density of 300~400 g / m² on the bonding surface. 2 .

[0057] Coating density is 300~400g / m 2 This ensures that the adhesive can fully penetrate the fiber felt and form a good adhesive layer.

[0058] Specifically, in step S2, before or during the application of the adhesive, a glass fiber mat layer is laid on the bonding surface, the glass fiber mat layer being used to form a reinforcing layer after curing.

[0059] This setting can further increase the strength of the adhesive interface.

[0060] Specifically, the glass fiber mat is at least one of stitch-woven mat, continuous mat, and chopped strand mat, and the areal density of the glass fiber mat is 120~600g / m².

[0061] Specifically, the semi-finished synthetic sleeper 1 is a glass fiber reinforced polyurethane foam synthetic sleeper, and the density of the semi-finished synthetic sleeper 1 is 640~1400 kg / m³. 3 .

[0062] The semi-finished synthetic sleeper 1 is made of glass fiber reinforced polyurethane foam material, which has an open pore structure. During the vacuum-assisted bonding process, the negative pressure not only removes the gas from the bonding interface, but also promotes the adhesive to penetrate into the open pores. After curing, it forms a mechanically interlocked reinforced interface layer, which is one of the important reasons why the bonding strength of this invention is significantly higher than that of traditional mechanical pressure bonding methods.

[0063] More specifically, in this application, the length of the composite sleeper is 9000~12000mm, the width of the composite sleeper is 400~800mm, and the height of the composite sleeper is 300~600mm.

[0064] More specifically, the width of the composite sleeper semi-finished product 1 is 200~450mm, the height is 140~240mm, and the length of the composite sleeper semi-finished product 1 is the same as that of the composite sleeper.

[0065] More specifically, the work surface is a stainless steel work surface or a glass work surface.

[0066] More specifically, the length and width of the workbench are both 400-2000mm larger than the dimensions of the large-size synthetic sleeper.

[0067] Key points of this invention: 1. It creatively applies vacuum-assisted molding technology to the specific scenario of structural bonding of large-size, porous foam composite materials, rather than traditional mechanical pressure bonding of composite materials. 2. The precise control range of adhesive viscosity (1000~2100 mPa·s) and vacuum degree (-0.09 to -0.1 MPa): too low viscosity leads to excessively fast flow and resin leakage, while too high viscosity fails to adequately wet the bonding surface; the resin viscosity range within this vacuum degree range is an optimized range verified by experiments. 3. The integrated process chain of "surface pretreatment in step S1 and vacuum-assisted degassing / wetting-curing in step S4" ensures the high quality of the final bonding interface through synergistic effects.

[0068] This invention proposes a molding method for vacuum-assisted bonding of synthetic railway sleepers. Steps S1 to S5 are interconnected and work together. By introducing a vacuum environment, this method can effectively eliminate air and volatiles at the bonding interface, ensuring the uniformity and density of large-area bonding. This results in the production of large-size synthetic railway sleepers with high bonding shear strength and flexural strength, no internal defects, and stable and reliable performance, while reducing production costs.

[0069] This invention proposes a molding method for vacuum-assisted bonding of synthetic railway sleepers, which has the following advantages:

[0070] I. Fundamental Improvement in Bonding Quality: The vacuum environment (-0.1MPa~-0.09MPa) forcibly removes air and volatiles from the bonding interface and the foam pores on the sleeper surface before the adhesive gels, fundamentally eliminating debonding defects such as bubbles and voids, achieving nearly 100% effective bonding area, and significantly improving bonding shear strength and flexural strength.

[0071] II. Breakthrough in pressure uniformity: The vacuum bag membrane provides uniform, full-surface, and dead-angle-free pressure (up to approximately 0.1 MPa) to the entire surface of the sleeper through atmospheric pressure, overcoming the inherent defects of traditional mechanical pressurization (hydraulic / pneumatic / bolt) which can only apply pressure locally and has uneven pressure distribution, thus ensuring the consistency of the thickness of the adhesive layer 2.

[0072] 3. Formation of "anchoring" reinforced interface: The negative pressure causes the adhesive to penetrate into the open pores of the surface layer of the synthetic sleeper. After curing, it forms a reinforced interface layer 3 with a mechanical interlocking structure. At the same time, it works in conjunction with the glass fiber felt reinforcement layer to further enhance the bonding interface strength.

[0073] IV. Adaptable to extra-large components: This method is not limited by the length (9000~12000mm), width (400~800mm), or height (300~600mm) of the component, and is particularly suitable for large-area and long-size bonding scenarios.

[0074] In a second aspect, the present invention also provides a large-size synthetic sleeper, which is formed using any one of the forming methods for a large-size synthetic sleeper described in any one of the present inventions.

[0075] More specifically, such as Figure 2 and Figure 3 As shown, the large-size synthetic sleeper includes:

[0076] At least two composite sleeper semi-finished products 1;

[0077] Adhesive layer 2, the adhesive layer 2 is located between the at least two composite sleeper semi-finished products 1, the adhesive layer 2 is used to bond the at least two composite sleeper semi-finished products 1 into one piece;

[0078] The adhesive layer 2 is a dense structure without air bubbles or voids, and an enhanced interface layer 3 is formed at the interface between the adhesive layer 2 and the synthetic sleeper semi-finished product 1, which is formed by the adhesive penetrating into the surface pores of the synthetic sleeper semi-finished product 1.

[0079] More specifically, the adhesive layer 2 also includes a glass fiber mat reinforcement layer.

[0080] Example 1

[0081] In this embodiment, the applicant proposes a method for molding a large-size synthetic railway sleeper. In this embodiment, the synthetic railway sleeper has a length of 9600mm, a width of 450mm, and a height of 320mm. The synthetic railway sleeper semi-finished product 1 has a length of 9600mm, a width of 450mm, and a height of 160mm. Therefore, the molding of the synthetic railway sleeper in this embodiment requires two pre-molded synthetic railway sleeper semi-finished products 1.

[0082] Specifically, the semi-finished synthetic sleeper 1 is a glass fiber reinforced polyurethane foam synthetic sleeper, and the density of the semi-finished synthetic sleeper 1 is 740 kg / m³. 3 .

[0083] The molding method includes the following steps:

[0084] S1. Surface pretreatment of semi-finished synthetic sleeper 1: The surface of the formed semi-finished synthetic sleeper 1 is pretreated; the pretreatment includes sanding, cleaning, and removing the surface skin and release agent and other smooth layers using a sander;

[0085] S2. Apply adhesive: Apply a layer of adhesive evenly to the bonding surface of the pre-treated synthetic sleeper semi-finished product 1;

[0086] S3. Assembly and Sealing: Based on the dimensions of the composite sleeper, prepare a workbench of the corresponding size and clean the surface. Then, cut vacuum bag film of the corresponding size, and glue sealing strips to the edges of the bag film for later use. At the same time, prepare a vacuum tube of the same length as the composite sleeper for later vacuuming. Assemble the glued composite sleeper semi-finished product 1 in alignment and fix it to form an assembly. Then, place the assembly in the flexible vacuum bag film and cover the vacuum tube inside the vacuum bag film. Finally, use sealing strips to tightly seal the edges of the vacuum bag film to the workbench to form a sealed cavity.

[0087] S4. Vacuum-assisted bonding and curing: Connect the vacuum pump to the sealed cavity and vacuum tube, start the vacuum pump to begin evacuation, and before the adhesive gels, evacuate the pressure inside the cavity to a vacuum state of -0.1MPa to -0.09MPa relative to atmospheric pressure; then maintain the vacuum state at room temperature for 20 hours, the adhesive first gels and then cures to form bonding layer 2, and the adhesive forms a dense, defect-free, and strong bonding layer 2 between the bonding surfaces of the synthetic sleepers.

[0088] S5. Post-processing: After curing, stop vacuuming, demold, remove the vacuum bag material, take out the bonded synthetic sleeper, and perform necessary repairs, processing and inspections on the synthetic sleeper to obtain the large-size synthetic sleeper.

[0089] In this embodiment, the adhesive is a two-component polyurethane adhesive.

[0090] In this embodiment, the viscosity of the adhesive after preparation is 1800±300 mPa·s, and the gel time is 30~40 min.

[0091] In this embodiment, since the adhesive gels for 30 to 40 minutes, in step S4, the vacuum needs to be evacuated to -0.09 to 0.1 MPa within less than 30 minutes.

[0092] More specifically, the adhesive is coated at a density of 400 g / m² on the bonding surface. 2 .

[0093] In this embodiment, the work surface is a glass surface, and the length and width of the work surface are both 1000mm larger than the size of the synthetic sleeper.

[0094] Example 2

[0095] In this embodiment, unlike in embodiment 1, as follows: Figure 4 As shown, the composite sleeper has a length of 12000mm, a width of 700mm, and a height of 420mm.

[0096] In this embodiment, there are three types of composite sleeper semi-finished products 1. The first type of composite sleeper semi-finished product 1 has a width of 240mm and a height of 240mm. The second type of composite sleeper semi-finished product 1 has a width of 350mm and a height of 180mm. The third type of composite sleeper semi-finished product 1 has a width of 220mm and a height of 240mm. The length of all three types of composite sleeper semi-finished products 1 is 12000mm.

[0097] Therefore, the molding of the composite sleeper in this embodiment requires two first-type composite sleeper semi-finished products 1, two second-type composite sleeper semi-finished products 1, and one third-type composite sleeper semi-finished product 1. In total, the molding of the composite sleeper in this embodiment requires five composite sleeper semi-finished products 1.

[0098] Specifically, the density of the synthetic sleeper semi-finished product 1 is 820 kg / m³. 3 .

[0099] The adhesive is a two-component epoxy resin adhesive.

[0100] In this embodiment, the viscosity of the adhesive after preparation is 1200±200 mPa·s, and the gel time is 65~75 min.

[0101] In this embodiment, since the adhesive gels for 65 to 75 minutes, in step S4, the vacuum needs to be evacuated to -0.09 to 0.1 MPa within less than 65 minutes.

[0102] More specifically, the adhesive is coated at a density of 300 g / m² on the bonding surface. 2 .

[0103] Specifically, in this embodiment, in step S2, during the adhesive application process, a layer of glass fiber mat is laid on the bonding surface, wherein the glass fiber mat has an areal density of 300 g / m². 2 Continuous felt.

[0104] Example 3

[0105] In this embodiment, unlike in embodiment 2, in step S4, the vacuum state is maintained for 12 hours under heating conditions, and the heating temperature is 50°C.

[0106] Comparative Example 1

[0107] In this comparative example, steps S1 and S2 are the same as in Example 1, and will not be repeated here.

[0108] Unlike Example 1, step S3 involves mechanical pressure-assisted bonding and curing: the glued synthetic sleepers are initially fixed in alignment to form an assembly, and then the assembly is placed in a mechanical bonding and pressure-applying fixture composed of channel steel and bolts and nuts. Pressure is applied by the mechanical pressure-applying fixture, with an average pressure of 0.1 MPa or higher. The mechanical pressure is maintained at room temperature for 22 hours to allow the adhesive to fully cure, and the adhesive cures between the bonding surfaces of the synthetic sleepers to form an adhesive layer 2.

[0109] Step S4 Post-processing: After curing, disassemble the mechanical bonding and pressure fixture, remove the bonded composite sleeper, and perform necessary repairs and processing on the composite sleeper to obtain a large-size composite sleeper.

[0110] Since the specific structure and assembly relationship of the relevant components of the mechanical bonding pressure tool are existing technologies, they will not be described in detail here.

[0111] Comparative Example 2

[0112] In this comparative example, steps S1 and S2 are the same as in Example 2, and will not be repeated here.

[0113] Unlike Example 2, step S3 involves mechanical pressure-assisted bonding and curing: the composite sleepers after applying adhesive are initially fixed in alignment to form an assembly, and then the assembly is placed in a mechanical bonding and pressure-applying fixture composed of channel steel and bolts and nuts. Pressure is applied by the mechanical pressure-applying fixture, with an average pressure of 0.1 MPa or more; under mechanical pressure for 22 hours, the adhesive is completely cured at room temperature, and the adhesive is cured between the bonding surfaces of the composite sleepers to form bonding layer 2.

[0114] Step S4 Post-processing: After curing, disassemble the mechanical bonding and pressure fixture, remove the bonded composite sleeper, and perform necessary repairs and processing on the composite sleeper to obtain a large-size composite sleeper.

[0115] Performance testing

[0116] The synthetic sleeper products obtained in Examples 1-3 and Comparative Examples 1-2 were tested according to the CJ / T399-2012 standard "Roll Paper Foam Synthetic Sleeper". The adhesive shear strength (50×52×40mm) and bending strength (400×50×20mm) samples were taken from the bonding surface. Ten parallel samples were taken for each group of tests. The adhesive shear strength and bending performance of the samples were tested according to the standard. The average value and variance were calculated. The results are shown in Table 1.

[0117] Table 1 Performance data of synthetic sleepers

[0118]

[0119] As can be seen from the data in Table 1:

[0120] 1. Increased Strength: Whether using polyurethane adhesive (Example 1) or epoxy resin adhesive (Example 2), the average bond shear strength and flexural strength of the samples prepared using the vacuum-assisted bonding method of this invention are significantly higher than those of the corresponding mechanically compressed comparative examples. In particular, the bond shear strength of Example 2 is approximately 46% higher than that of Comparative Example 2, and the flexural strength is approximately 13.5% higher.

[0121] 2. Excellent stability: In Examples 1 and 2 using the method of this invention, the variance of various strength data is much smaller than that of the corresponding comparative examples. This indicates that the vacuum-assisted bonding method ensures excellent consistency in bonding quality and process stability, overcoming the defects of large fluctuations in product performance caused by uneven pressure in mechanical pressing.

[0122] 3. Comparing Example 2 (cured at room temperature for 20 hours) and Example 3 (cured at 50°C for 12 hours), it can be seen that the bond shear strength (15.86 MPa vs 15.59 MPa) and flexural strength (152.8 MPa vs 151.7 MPa) are highly similar, with relative deviations within 2%. This indicates that, provided sufficient curing time is ensured, both room temperature curing and heat curing can achieve equally excellent bonding effects. Heat curing can shorten the curing time from 20 hours to 12 hours, effectively improving production efficiency and providing a more flexible process option for industrial mass production. Furthermore, the high consistency of product performance under the two curing methods further demonstrates that the method of this invention has an extremely wide process window and good adaptability.

[0123] In summary, this invention provides a large-size synthetic railway sleeper and a molding method therefor, which effectively solves the problem of bonding large-size synthetic railway sleepers, significantly improves the bonding strength, mechanical properties and reliability of the product, and ensures the quality stability of mass production.

[0124] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for molding large-size synthetic railway sleepers, characterized in that, The molding method includes the following steps: S1. Surface pretreatment of semi-finished synthetic sleeper (1): Pretreatment of the surface of at least two pre-formed semi-finished synthetic sleeper (1); S2, Apply adhesive: Apply adhesive to the bonding surface of the pre-treated synthetic sleeper semi-finished product (1); S3. Assembly and sealing: First, align and assemble the glued synthetic sleeper semi-finished product (1) to form an assembly; then place the assembly in a sealed vacuum bag film system, which is placed on a workbench and forms a closed cavity. S4. Vacuum-assisted bonding and curing: Start the vacuum pump and first evacuate the sealed cavity. Before the adhesive gels, the pressure inside the cavity is evacuated to a vacuum state of -0.1MPa to -0.09MPa relative to atmospheric pressure. Then, maintain the vacuum state for ≥12h under room temperature or heating conditions. The adhesive gels first and then cures to form an adhesive layer (2). S5. Post-processing: After curing, turn off the vacuum pump, disassemble the vacuum bag film system, and post-process to obtain the large-size synthetic sleeper.

2. The molding method for a large-size synthetic railway sleeper according to claim 1, characterized in that, In step S4, the vacuum state is maintained under heating conditions, and the heating temperature is 30~60°C.

3. The molding method for a large-size synthetic railway sleeper according to claim 1, characterized in that, The adhesive is one of epoxy resin adhesive, polyurethane adhesive and vinyl resin adhesive.

4. The molding method for a large-size synthetic railway sleeper according to claim 1, characterized in that, The adhesive has a viscosity of ≤3000 mPa·s at room temperature and a gel time of 30~90 min.

5. The molding method for a large-size synthetic railway sleeper according to claim 4, characterized in that, The adhesive has a viscosity of 1000~2100 mPa·s at room temperature and a gel time of 30~75 min.

6. The molding method for a large-size synthetic railway sleeper according to claim 1, characterized in that, In step S2, a layer of glass fiber mat is laid on the bonding surface before or during the application of the adhesive.

7. The molding method for a large-size synthetic railway sleeper according to claim 6, characterized in that, The glass fiber mat is at least one of stitch-woven mat, continuous mat, and chopped strand mat, and the areal density of the glass fiber mat is 120~600g / m².

8. The molding method for a large-size synthetic railway sleeper according to claim 1, characterized in that, The semi-finished synthetic sleeper (1) is a glass fiber reinforced polyurethane foam synthetic sleeper, and the density of the semi-finished synthetic sleeper (1) is 640~1400 kg / m³. 3 .

9. The molding method for a large-size synthetic railway sleeper according to claim 1, characterized in that, The adhesive is coated at a density of 300~600 g / m² on the bonding surface. 2 .

10. A large-size synthetic railway sleeper, characterized in that, The large-size composite sleeper is formed using the molding method for a large-size composite sleeper according to any one of claims 1 to 9, and the large-size composite sleeper comprises: At least two synthetic sleeper semi-finished products (1); An adhesive layer (2) is located between the at least two synthetic sleeper semi-finished products (1); The adhesive layer (2) is a dense structure without air bubbles or voids, and an enhanced interface layer (3) is formed at the interface between the adhesive layer (2) and the synthetic sleeper semi-finished product (1).

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