Railway sleeper material of modified polymer, railway sleeper and preparation method of railway sleeper material

Abstract

The invention discloses a railway sleeper material of a modified polymer, a railway sleeper and a preparation method of the railway sleeper material. The railway sleeper material of the modified polymer comprises the following components in percentage by mass: 55-70% of a base material; 15%-30% of a reinforcing phase; 8%-12% of inorganic filler; 0.2%-0.6% of a silane coupling agent; 3%-5% of an environment-friendly flame retardant; and 0.5%-1% of an anti-ultraviolet agent. The sleeper manufactured through the scheme has the comprehensive characteristics of being light, high in strength, excellent in weather resistance, stable in insulating property, environmentally friendly, recyclable and the like.

Description

Technical Field

[0001] This application relates to the field of railway track material manufacturing technology, and in particular to a modified polymer railway sleeper material, railway sleepers and their preparation method. Background Technology

[0002] Railway sleepers are key load-bearing components in track structures. Traditionally, they are mainly made of wood or concrete. Wooden sleepers have drawbacks such as being prone to corrosion and cracking, having a short service life, and consuming high-quality timber; concrete sleepers, on the other hand, are heavy and rigid, resulting in poor vibration damping and insulation performance, and are prone to stress fatigue under long-term cyclic loads, posing safety hazards.

[0003] To overcome the shortcomings of traditional materials, the industry has begun to research the use of polymer composite materials to prepare third-generation railway sleepers. Existing technologies have attempted to prepare sleepers by combining thermoplastics, polyurethanes, and recycled polymers with reinforcing fibers or fillers. However, these existing solutions generally suffer from some common problems: it is difficult to balance the strength, toughness, and fatigue resistance of the material system; poor interfacial compatibility between components affects long-term durability and insulation stability; or the excessive use of recycled materials and fillers in pursuit of low costs leads to a decline in key performance characteristics, making it difficult to meet the stringent requirements of high-frequency, heavy-load vibration in railways. Summary of the Invention

[0004] The embodiments of this application provide a modified polymer railway sleeper material, railway sleepers, and a method for preparing the same.

[0005] In a first aspect, embodiments of this application provide a modified polymer railway sleeper material comprising the following components by weight percentage: Substrate: 55%-70%; Enhanced phase: 15%-30%; Inorganic fillers: 8%-12%; Silane coupling agent: 0.2%-0.6%; Environmentally friendly flame retardant: 3%-5%; UV protectant: 0.5%-1%.

[0006] In one embodiment, the substrate is made of thermoplastic polyurethane elastomer (TPU) or high-density polyethylene (HDPE). When the substrate is thermoplastic polyurethane elastomer (TPU), the hardness of the thermoplastic polyurethane elastomer is 90A; When the substrate is high-density polyethylene, the melt flow rate of high-density polyethylene is 10 g / 10 min.

[0007] In one embodiment, the reinforcing phase is made of glass fiber or carbon fiber; The length of the glass fiber is 10-15mm; The length of carbon fiber is 8-12mm.

[0008] In one embodiment, the inorganic filler is nano-silica (SiO2) or montmorillonite (MMT). The particle size of nano-silica is 50 nm; The montmorillonite used is organically modified montmorillonite.

[0009] In one embodiment, the environmentally friendly flame retardant is a phosphorus-nitrogen compound; Phosphorus-nitrogen compounds are complexes of ammonium polyphosphate and melamine or complexes of phosphonates and guanidine salts; The UV stabilizers are hindered amines or benzotriazoles.

[0010] Secondly, embodiments of this application provide a method for preparing railway sleeper material of modified polymer as described in the first aspect, comprising: Weigh the base material, reinforcing phase, inorganic filler, silane coupling agent, environmentally friendly flame retardant, and UV stabilizer according to the mass percentages described in the first aspect; Inorganic filler was mixed with silane coupling agent, dispersed by high-speed mixer and then dried to obtain pretreated inorganic filler; The base material, pretreated inorganic filler, reinforcing phase, environmentally friendly flame retardant and UV stabilizer are added to a twin-screw extruder for melt blending, extrusion granulation, and modified polymer railway sleeper material is obtained.

[0011] In one embodiment, the high-speed mixer rotates at 1500-2000 rpm, the dispersion time is 15-20 min, the drying temperature is 60-80℃, and the drying time is 2-3 h.

[0012] In one embodiment, when the substrate is a thermoplastic polyurethane elastomer, the temperature of the twin-screw extruder for blending extrusion is set to 180-200°C, with zone 1 at 180°C, zone 2 at 190°C, zone 3 at 200°C, and the die head at 200°C, and the screw speed is 200-300 rpm. When the substrate is high-density polyethylene, the temperature of the twin-screw extruder for blending extrusion is set to 190-220℃, with 190℃ in zone 1, 210℃ in zone 2, 220℃ in zone 3, and 210℃ at the die head, and the screw speed is 300-400 rpm.

[0013] Thirdly, embodiments of this application provide a railway sleeper comprising a railway sleeper material of a modified polymer as described in the first aspect.

[0014] Fourthly, embodiments of this application provide a method for preparing railway sleepers as described in the third aspect, comprising: Railway sleeper materials made of modified polymers are used to prepare sleeper blanks by extrusion molding or injection molding. The sleeper blanks are then subjected to dynamic vulcanization crosslinking treatment at 160-180℃ for 30-60 minutes to obtain finished railway sleepers with a crosslinking density ≥85%.

[0015] This application has the following advantages over the prior art: This application combines a reinforcing phase and inorganic fillers to construct a multi-level reinforcing network within the material. The reinforcing phase acts as the main load-bearing skeleton, while the inorganic fillers fully fill and strengthen the matrix and interfacial regions. Their synergistic effect allows the material to achieve high modulus and high strength while effectively maintaining matrix toughness. Furthermore, the combination of these two components with a silane coupling agent significantly optimizes stress transfer efficiency and prevents interfacial delamination, thus fully leveraging the reinforcing potential of the reinforcing phase and fillers. Moreover, the surface coating modification of the inorganic fillers and reinforcing phase using the silane coupling agent significantly reduces the hygroscopicity of these components in humid environments, ensuring that the composite material maintains stable and excellent insulation resistance characteristics during wet and dry cycles, meeting the long-term reliability requirements of electrified railway sleeper insulation performance. The good dispersion of the inorganic fillers in the matrix forms a dense physical barrier network, effectively delaying the penetration of aging media such as oxygen and water vapor, thereby comprehensively improving the material's resistance to environmental aging. By combining environmentally friendly flame retardants with inorganic fillers, a synergistic effect of condensed-phase flame retardancy is achieved. During combustion, the inorganic fillers promote the formation of a more complete and denser char layer barrier. This barrier effectively insulates against heat and oxygen and prevents the escape of combustible gases, thereby improving overall flame retardant efficiency and smoke suppression while reducing the amount of flame retardant required. Both the environmentally friendly flame retardants and UV stabilizers are selected based on environmental principles, avoiding harmful substances such as halogens, ensuring that the high-performance composite material meets environmental safety standards throughout its entire life cycle. The substrate utilizes silane coupling agents to optimize the interface and employs an optimized dynamic vulcanization process, ensuring high crosslinking density and excellent performance while maintaining a certain degree of thermoplastic processability, overcoming the bottleneck of traditional crosslinked materials being non-recyclable. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic flowchart illustrating the preparation method of railway sleeper material made from modified polymers according to embodiments of this application. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] Embodiments of this application provide a modified polymer railway sleeper material comprising the following components by weight percentage: Substrate: 55%-70%; Enhanced phase: 15%-30%; Inorganic fillers: 8%-12%; Silane coupling agent: 0.2%-0.6%; Environmentally friendly flame retardant: 3%-5%; UV protectant: 0.5%-1%.

[0020] Specifically, the substrate is the main body of the railway sleeper material, used to encapsulate and bond all other components, forming the basis of the composite material. Furthermore, as the continuous phase of the railway sleeper material, the substrate provides the main volume and fundamental properties, such as enabling lightweight sleepers, insulation, and providing basic toughness and chemical resistance for the material system.

[0021] The reinforcing phase is the skeleton of mechanical properties in railway sleeper materials. Its main function is to significantly improve the tensile strength, flexural modulus, stiffness and creep resistance of the material, enabling the composite material to withstand long-term high dynamic loads from trains.

[0022] Inorganic fillers are used to fill volume, reduce material costs, and at the same time improve the stiffness, hardness and dimensional stability of materials.

[0023] Silane coupling agents are used to graft and modify the surface of fillers, improving interfacial bonding. Specifically, one end bonds to the surface of the inorganic material (reinforcing phase, inorganic filler), while the other end interacts chemically or physically with the substrate, thereby establishing a strong interfacial bond between the two. This significantly improves interfacial compatibility, ensuring mechanical properties and durability. KH-550 or KH-570 can be used as silane coupling agents.

[0024] The role of environmentally friendly flame retardants is to effectively delay or prevent the combustion of materials under high temperature or flame conditions by absorbing heat, isolating oxygen, or promoting char formation, thereby meeting the fire safety standards for railway materials.

[0025] UV stabilizers prevent photo-oxidative degradation of polymer molecular chains by absorbing or shielding ultraviolet radiation from sunlight. Their function is to effectively delay aging, discoloration, surface chalking, and decline in mechanical properties of materials during long-term outdoor use, ensuring the lifespan of railway sleepers.

[0026] In this embodiment, by combining the reinforcing phase and inorganic filler, a multi-level reinforcing network can be constructed within the material. The reinforcing phase acts as the main load-bearing skeleton, while the inorganic filler fully fills and strengthens the matrix and interface regions. Their synergistic effect allows the material to achieve high modulus and high strength while effectively maintaining matrix toughness. Furthermore, the combination of these two components with a silane coupling agent greatly optimizes stress transfer efficiency and prevents interface delamination, thus fully leveraging the reinforcing potential of the reinforcing phase and filler. Moreover, the silane coupling agent's surface coating modification of the inorganic filler and reinforcing phase significantly reduces the hygroscopicity of these components in humid environments, ensuring that the composite material maintains stable and excellent insulation resistance characteristics during wet and dry cycles, meeting the long-term reliability requirements of electrified railway sleeper insulation performance. The good dispersion of the inorganic filler in the matrix forms a dense physical barrier network, effectively delaying the penetration of aging media such as oxygen and water vapor, thereby improving the overall environmental aging resistance of the material. By combining environmentally friendly flame retardants with inorganic fillers, a synergistic effect of condensed-phase flame retardancy is achieved. During combustion, the inorganic fillers promote the formation of a more complete and denser char layer barrier. This barrier effectively insulates against heat and oxygen and prevents the escape of combustible gases, thereby improving overall flame retardant efficiency and smoke suppression while reducing the amount of flame retardant required. Both the environmentally friendly flame retardants and UV stabilizers are selected based on environmental principles, avoiding harmful substances such as halogens, ensuring that the high-performance composite material meets environmental safety standards throughout its entire life cycle. The substrate utilizes silane coupling agents to optimize the interface and employs an optimized dynamic vulcanization process, ensuring high crosslinking density and excellent performance while maintaining a certain degree of thermoplastic processability, overcoming the bottleneck of traditional crosslinked materials being non-recyclable.

[0027] In one embodiment, the substrate is made of thermoplastic polyurethane elastomer (TPU) or high-density polyethylene (HDPE). When the substrate is thermoplastic polyurethane elastomer (TPU), the hardness of the thermoplastic polyurethane elastomer is 90A; When the substrate is high-density polyethylene, the melt flow rate of high-density polyethylene is 10 g / 10 min.

[0028] Specifically, thermoplastic polyurethane elastomers possess excellent elasticity and energy absorption capabilities. Combined with reinforcement, they can be used to create composite materials that combine rigidity and flexibility. As a high-performance elastic matrix, it is designed to address issues related to dynamic fatigue, vibration reduction, noise reduction, and adaptability to extreme environments in railway sleepers.

[0029] High-density polyethylene (HDPE) itself has higher hardness and stiffness. Combined with reinforcement, it can produce structures with high modulus and high load-bearing capacity, exhibiting excellent dimensional stability under static and slow-speed loads. It is a cost-effective rigid matrix, designed to maximize cost control, corrosion resistance, and the utilization of recyclable resources while ensuring performance standards are met.

[0030] In one embodiment, the reinforcing phase is made of glass fiber or carbon fiber; The length of the glass fiber is 10-15mm; The length of carbon fiber is 8-12mm.

[0031] Specifically, the glass fiber length is set at 10-15mm, providing extremely high cost-effectiveness, significantly improving strength, stiffness and dimensional stability, and fully meeting the stringent requirements of railway sleepers for basic mechanical properties.

[0032] The carbon fiber length is set at 8-12mm. The slightly shorter length ensures ultra-high specific strength, specific modulus and creep resistance, while also reducing the amount added per unit. In addition, carbon fiber is relatively brittle, and the slightly shorter length is less likely to break during processing, which can better maintain its integrity and improve dispersion and reduce damage.

[0033] During the high-temperature, high-shear dynamic vulcanization process, the set fiber length range can remain relatively stable, avoiding excessive degradation. Sufficient length also ensures effective interlocking and stress transfer interfaces with the TPU or HDPE matrix, allowing the composite material to truly embody a balance of rigidity and flexibility.

[0034] Fibers in this length range have a suitable specific surface area, which can be fully coated and modified by silane coupling agents to achieve perfect interfacial bonding, without causing a surge in coupling agent usage or an excessively thick interfacial layer due to excessive surface area, thus avoiding weaknesses.

[0035] In this embodiment, the glass fiber length is set to 10-15mm and the carbon fiber length is set to 8-12mm. This avoids the reinforcing phase being too short or too long. The length setting in this embodiment ensures that the fiber retains a sufficient aspect ratio after processing to efficiently bear the load, while also ensuring good dispersion and processing flowability.

[0036] In one embodiment, the inorganic filler is nano-silica (SiO2) or montmorillonite (MMT). The particle size of nano-silica is 50 nm; The montmorillonite used is organically modified montmorillonite.

[0037] Specifically, the surface of nano-silica is rich in silanol groups. Treatment with silane coupling agents not only achieves perfect dispersion but also establishes a robust covalent bond interface, maximizing the reinforcing efficiency of the nanoparticles. During combustion, nano-SiO2 migrates to the material surface, forming a robust siliceous protective layer that isolates heat and oxygen. Simultaneously, it synergizes with environmentally friendly flame retardants to promote the formation of a more stable and denser char layer, improving flame retardant efficiency. Furthermore, nano-SiO2 scatters and reflects ultraviolet light, effectively shielding it and synergizing with UV stabilizers to provide additional protection for the matrix and delay photoaging. Moreover, an appropriate amount of nano-SiO2 can increase the viscosity and strength of polymer melts, which is beneficial for the molding of complex shapes and dimensional retention.

[0038] The interlayer structure of montmorillonite (MMT) typically requires organic modification (commonly using quaternary ammonium salt intercalating agents) to widen the interlayer spacing and improve compatibility with polymers. Silane coupling agents can synergize with or replace some functions in this organic modification process, further strengthening the interface. Exfoliated nano-MMT sheets can form a dense nano-brick wall structure on the material surface during combustion, significantly delaying the escape of combustible gases and heat transfer, making it a highly efficient physical flame retardant that can significantly reduce the heat release rate and smoke production. Nano-dispersed MMT sheets can greatly extend the penetration path of aging factors such as water vapor and oxygen, thereby physically delaying the thermo-oxidative and water-oxygen aging processes of the matrix.

[0039] In addition, glass fiber or carbon fiber and nanofillers form a macro-nano multi-level reinforcement network. Fibers of a set length serve as the main skeleton, while nanofillers strengthen the matrix and interface. The two complement each other at different scales and work together to improve the overall mechanical properties and durability of the material.

[0040] The inorganic filler nano-silica or montmorillonite used in this embodiment, together with the functionality of environmentally friendly flame retardants and UV stabilizers, creates multiple synergies at the chemical and physical levels, improving the overall durability and safety of the material from multiple dimensions such as barrier, shielding, and carbon layer enhancement.

[0041] In one embodiment, the environmentally friendly flame retardant is a phosphorus-nitrogen compound; Phosphorus-nitrogen compounds are complexes of ammonium polyphosphate and melamine or complexes of phosphonates and guanidine salts; The UV stabilizers are hindered amines or benzotriazoles.

[0042] Specifically, ammonium polyphosphate and melamine work synergistically to form a uniform, dense, and porous expanded char layer on the material surface. This char layer effectively insulates against heat and oxygen transfer and prevents the escape of internal combustible gases, thus achieving excellent flame retardant properties.

[0043] The combination of phosphonates and guanidine salts achieves a dual effect of gas-phase flame retardancy (chemical interruption) and condensed-phase flame retardancy (physical barrier), resulting in high flame retardant efficiency, minimal impact on the mechanical properties of the material, and good thermal stability.

[0044] Using phosphorus-nitrogen compounds as environmentally friendly flame retardants, the char layer formed by the phosphorus-nitrogen flame retardants and the "nano brick wall" structure formed by the migration of nano montmorillonite sheets during combustion can mutually reinforce each other, building a stronger and denser protective barrier, producing a flame retardant synergy of "1+1>2", which can reduce the total amount of flame retardant added.

[0045] For both TPU and HDPE substrates, phosphorus-nitrogen flame retardants have good compatibility, are not prone to precipitation, and can provide long-lasting flame retardant protection.

[0046] Hindered amines are free radical scavengers. They do not directly absorb ultraviolet light, but rather efficiently capture and quench free radicals that cause aging when polymers are excited by ultraviolet light, thus interrupting the chain reaction of photodegradation. They can also repair some damaged molecular chains, exhibiting long-lasting effects and regenerative capabilities.

[0047] Benzotriazoles are ultraviolet absorbers. Their molecular structure strongly absorbs ultraviolet light and converts it into harmless heat energy that is dissipated. They provide polymers with a direct and primary first line of defense, offering high protection efficiency and good durability.

[0048] After benzotriazole absorbers remove most of the ultraviolet light, nano-silica particles can physically reflect and scatter the residual or scattered ultraviolet light, forming a dual protection network of chemical absorption and physical shielding, which greatly improves the reliability of ultraviolet protection.

[0049] Silane coupling agents can achieve good interfacial bonding, ensuring the stable existence of UV stabilizers in the matrix, preventing migration or leakage, and guaranteeing long-term effectiveness.

[0050] For polyolefins such as HDPE, hindered amines offer more effective UV protection, while for polar materials such as TUP, benzotriazoles exhibit better compatibility and efficiency.

[0051] The environmentally friendly flame retardant and UV stabilizer provided in this embodiment, along with the reinforcing, toughening, and interface-modifying components, are integrated into a stable three-dimensional network formed by dynamic vulcanization. Together, they ensure that the sleepers can resist the erosion of multiple aging factors such as fire risk, ultraviolet radiation, heat and oxygen, and humidity during decades of outdoor use, thereby simultaneously achieving long-term durability, environmental safety, and reliability in use.

[0052] like Figure 1 As shown in the embodiments of this application, a method for preparing railway sleeper materials of the above-mentioned modified polymer is also provided, including: S110. Weigh the base material, reinforcing phase, inorganic filler, silane coupling agent, environmentally friendly flame retardant, and UV stabilizer according to the above-mentioned mass percentages. S120. The inorganic filler is mixed with the silane coupling agent, dispersed by a high-speed mixer, and then dried to obtain the pretreated inorganic filler. The speed of the high-speed mixer is 1500-2000 rpm, the dispersion time is 15-20 min, the drying temperature is 60-80℃, and the drying time is 2-3 h.

[0053] S130. The base material, pretreated inorganic filler, reinforcing phase, environmentally friendly flame retardant and UV stabilizer are added to a twin-screw extruder for melt blending, extrusion granulation, and modified polymer railway sleeper material is obtained.

[0054] When the substrate is thermoplastic polyurethane elastomer, the temperature of the twin-screw extruder for blending extrusion is set to 180-200℃, with 180℃ in zone 1, 190℃ in zone 2, 200℃ in zone 3, and 200℃ at the die head, and the screw speed is 200-300 rpm. When the substrate is high-density polyethylene, the temperature of the twin-screw extruder for blending extrusion is set to 190-220℃, with 190℃ in zone 1, 210℃ in zone 2, 220℃ in zone 3, and 210℃ at the die head, and the screw speed is 300-400 rpm.

[0055] This application also provides a railway sleeper, comprising the railway sleeper material of the modified polymer provided in the above embodiments.

[0056] This application also provides a method for preparing railway sleepers, including: Railway sleeper materials made of modified polymers are used to prepare sleeper blanks by extrusion molding or injection molding. The sleeper blanks are then subjected to dynamic vulcanization crosslinking treatment at 160-180℃ for 30-60 minutes to obtain finished railway sleepers with a crosslinking density ≥85%.

[0057] Specifically, when preparing sleeper blanks using injection molding, an injection molding machine can be used for injection molding, with a mold temperature of 80-90℃. Understandably, this temperature can be set according to actual needs.

[0058] When preparing sleeper blanks using extrusion molding, the extrusion speed is 0.5-0.8 m / min. Understandably, this speed can be set according to actual needs.

[0059] Dynamic vulcanization crosslinking treatment can be carried out in a vulcanization tank.

[0060] Understandably, the finished sleeper blanks can also undergo surface anti-slip texture processing and edge trimming. The surface anti-slip texture is processed by milling or rolling, with a texture depth of 2-3mm, which can be set according to actual needs.

[0061] The sleeper blanks produced through the embodiments of this application possess comprehensive characteristics such as being lightweight and high-strength, having excellent weather resistance, stable insulation performance, and being environmentally friendly and recyclable.

[0062] Example 1 Using TPU as the base material, glass fiber reinforcement, and nano-SiO2 as the modifying material, weigh out the following by mass fraction: 60% thermoplastic polyurethane elastomer (TPU) with a hardness of 90A, 27% glass fiber with a length of 10mm, 8% nano-SiO2 with a particle size of 50nm, 0.3% KH-550, 4% ammonium polyphosphate and melamine composite, and 0.7% hindered amines.

[0063] Nano-SiO2 and KH-550 were mixed and dispersed in a high-speed mixer. The speed of the high-speed mixer was set to 1500 rpm and the dispersion time was 15 min. The mixture was then dried in an 80℃ oven for 2 h to remove moisture, thus obtaining pretreated nano-SiO2.

[0064] TPU particles, pretreated nano-SiO2, glass fiber, ammonium polyphosphate and melamine composite, and hindered amines are added to a twin-screw extruder. The extrusion temperature is set to 180-200℃ (zone 1 180℃, zone 2 190℃, zone 3 200℃, and die head 200℃), and the screw speed is 300 rpm. After melt blending, the mixture is extruded and granulated to obtain the modified polymer railway sleeper material.

[0065] The modified polymer railway sleeper material was injection molded into sleeper blanks using an injection molding machine with a mold temperature of 80°C. The blanks were then placed in a vulcanizing tank and dynamically vulcanized at 170°C for 45 minutes, with a crosslinking density of 88% measured.

[0066] The surface of the vulcanized sleeper blank is milled to create an anti-slip texture with a texture depth of 2mm, and the edges and burrs are trimmed to obtain the finished sleeper.

[0067] Example 2 Using HDPE as the base material, carbon fiber reinforcement, and montmorillonite as the modifier, the following amounts were weighed by mass fraction: 55% high-density polyethylene (HDPE) with a melt flow rate of 10 g / 10 min, 30% carbon fiber with a length of 8 mm, 9% montmorillonite, 0.5% KH-570, 5% phosphonates and guanidine salt complexes, and 0.5% benzotriazoles.

[0068] Montmorillonite and KH-570 were mixed and dispersed in a high-speed mixer. The mixer speed was set to 2000 rpm and the dispersion time was 20 min. The mixture was then dried in a 60℃ oven for 3 h to remove moisture, resulting in pretreated montmorillonite.

[0069] HDPE granules, pretreated montmorillonite, carbon fibers, phosphinate and guanidine salt complexes, and benzotriazoles are added to a twin-screw extruder. The extrusion temperature is set to 190-220℃ (zone 1: 190℃, zone 2: 210℃, zone 3: 220℃, die head: 210℃), and the screw speed is 350 rpm. After melt blending, the mixture is extruded and granulated to produce modified polymer railway sleeper material.

[0070] The modified polymer railway sleeper material was prepared into sleeper blanks by extrusion molding process, wherein the extrusion speed was 0.5 m / min, and then placed in a vulcanizing tank for dynamic vulcanization at 180℃ for 30 min, and the crosslinking density was measured to be 90%.

[0071] Anti-slip textures are pressed onto the surface of the vulcanized sleeper blanks using a rolling process. The texture depth is 3mm, and the edges and burrs are trimmed to obtain the finished sleepers.

[0072] Example 3 Using TPU as the base material, reinforced with carbon fiber, and modified with organic montmorillonite as the modifier, the following amounts were weighed by mass fraction: 70% thermoplastic polyurethane elastomer (TPU) with a hardness of 90A, 15% carbon fiber with a length of 12mm, 10.4% organically modified montmorillonite, 0.6% KH-550, 3% ammonium polyphosphate and melamine composite, and 1% hindered amines.

[0073] Organically modified montmorillonite and KH-550 were mixed and dispersed in a high-speed mixer. The speed of the high-speed mixer was set to 1800 rpm and the dispersion time was 18 min. The mixture was then dried in a 70℃ oven for 3 h to remove moisture, thus obtaining pretreated montmorillonite.

[0074] TPU particles, pretreated montmorillonite, carbon fiber, ammonium polyphosphate and melamine composite, and hindered amines are added to a twin-screw extruder. The extrusion temperature is set to 180-200℃ (zone 1: 180℃, zone 2: 190℃, zone 3: 200℃, and die head: 200℃), and the screw speed is 200 rpm. After melt blending, the mixture is extruded and granulated to obtain the modified polymer railway sleeper material.

[0075] The modified polymer railway sleeper material was injection molded into sleeper blanks using an injection molding machine with a mold temperature of 80°C. The blanks were then placed in a vulcanizing tank and dynamically vulcanized at 160°C for 60 minutes, with a crosslinking density of 85% measured.

[0076] The surface of the vulcanized sleeper blank is milled to create an anti-slip texture with a texture depth of 2mm, and the edges and burrs are trimmed to obtain the finished sleeper.

[0077] Example 4 Using HDPE as the base material, glass fiber reinforcement, and montmorillonite as the modifier, the following amounts were weighed by mass fraction: 65% high-density polyethylene (HDPE) with a melt flow rate of 10 g / 10 min, 17% glass fiber with a length of 15 mm, 12% montmorillonite, 0.2% KH-570, 5% phosphonates and guanidine salt complexes, and 0.8% benzotriazoles.

[0078] Montmorillonite and KH-570 were mixed and dispersed in a high-speed mixer. The speed of the high-speed mixer was set to 1700 rpm and the dispersion time was 16 min. The mixture was then dried in a 60℃ oven for 2 h to remove moisture, resulting in pretreated montmorillonite.

[0079] HDPE granules, pretreated montmorillonite, glass fiber, phosphinate and guanidine salt complex, and benzotriazoles are added to a twin-screw extruder. The extrusion temperature is set to 190-220℃ (zone 1: 190℃, zone 2: 210℃, zone 3: 220℃, die head: 210℃), and the screw speed is 400 rpm. After melt blending, the mixture is extruded and granulated to obtain the modified polymer railway sleeper material.

[0080] Railway sleeper materials made of modified polymers were prepared into sleeper blanks by extrusion molding at a speed of 0.5 m / min. The blanks were then placed in a vulcanizing tank and dynamically vulcanized at 180°C for 30 min, and the crosslinking density was measured to be 89%.

[0081] Anti-slip textures are pressed onto the surface of the vulcanized sleeper blanks using a rolling process. The texture depth is 3mm, and the edges and burrs are trimmed to obtain the finished sleepers.

[0082] Referring to the quality standard for railway sleepers TB / T1879, the finished sleepers prepared in Examples 1-4 above were subjected to performance tests, and the results are as follows: Mechanical properties: Tensile strength ≥45MPa, flexural strength ≥60MPa, impact strength (notched) ≥80kJ / m 2 It meets the load-bearing and impact resistance requirements of railway sleepers.

[0083] Weather resistance: After artificial accelerated aging test (1000h UV irradiation), the tensile strength retention rate is ≥90%, and there is no obvious discoloration or cracking.

[0084] Insulation performance: Volume resistivity ≥10 14Ω•cm, dielectric constant 3.0-3.5 (1MHz), conforming to the insulation standards for electrified railways.

[0085] Flame retardancy: Vertical burning rating reaches UL94 V-0, oxygen index ≥30%.

[0086] Dimensional stability: After a heat distortion temperature of ≥120℃ and a cyclic test from -40℃ to 80℃, the dimensional change rate is ≤0.5%.

[0087] Comparative Example 1 The components do not contain silane coupling agents, and the remaining components are exactly the same as those in Example 1.

[0088] During the preparation process, after obtaining the sleeper blank, it was placed in an oven and statically dried at 180°C for 30 minutes (i.e., dynamic shearing was eliminated), and the crosslinking density was measured to be only 62%. The remaining processes were the same as in Example 1.

[0089] The crosslinking density of the finished sleepers prepared in Comparative Example 1 was significantly reduced. Due to the lack of silane coupling agent, the interface bonding between the inorganic filler and the reinforcing phase and the matrix was extremely weak, resulting in a significant decrease in flexural strength to 40 MPa; the toughness was also severely insufficient, with a notched impact strength of only 40 kJ / m. 2 The volume resistivity is 9×10⁻⁶. 12 The insulation stability is poor (Ω•cm); the weather resistance is also significantly worse than in Example 1, and the flame retardant efficiency is reduced.

[0090] Comparative Example 1 demonstrates that silane coupling agents are crucial components for ensuring a robust interface between reinforcing fibers, inorganic fillers, and the substrate. Their absence directly leads to a comprehensive deterioration in the material's mechanical strength, toughness, and long-term environmental stability (insulation and weather resistance). Dynamic vulcanization is a key process for achieving high and uniform crosslinking density. Compared to static heat drying, it efficiently constructs a stable three-dimensional network, which is fundamental to the material's excellent creep resistance, dimensional stability, and durability.

[0091] Comparative Example 2 The reinforcing phase in this composition is short-cut glass fiber with a length of 3 mm, and the filler is ordinary heavy calcium carbonate with a mesh size of 800. Other components and processes are exactly the same as in Example 4.

[0092] In Comparative Example 2, due to the insufficient aspect ratio of the 3mm chopped glass fibers, which are close to a granular filling state, they cannot effectively bear and transfer loads. Furthermore, calcium carbonate is a common filler, which only has an incremental filling effect and lacks the reinforcing effect of montmorillonite. Therefore, the flexural strength is significantly reduced. The excessively short fibers and poor reinforcement effect of the filler lead to a decrease in the material's resistance to deformation and a decrease in flexural modulus. The chopped fibers and fillers cannot effectively hinder and passivate crack propagation, resulting in increased brittleness and reduced notched impact strength. Compared with Example 4, Comparative Example 2 has lower heat resistance and reduced flame retardant efficiency.

[0093] This comparative example shows that when the reinforcing fibers are too short, their reinforcing efficiency drops sharply, failing to meet the requirements of high strength and high stiffness for railway sleepers. Montmorillonite not only provides reinforcement but also offers multifunctional effects such as barrier properties, heat resistance, and synergistic flame retardancy through its nanosheet structure, making it key to achieving the comprehensive performance of railway sleepers, including lightweight, high strength, high weather resistance, and high flame retardancy.

[0094] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A modified polymer railway sleeper material, characterized in that, Includes the following components by mass percentage: Substrate: 55%-70%; Enhanced phase: 15%-30%; Inorganic fillers: 8%-12%; Silane coupling agent: 0.2%-0.6%; Environmentally friendly flame retardant: 3%-5%; UV protectant: 0.5%-1%.

2. The modified polymer railway sleeper material according to claim 1, characterized in that, The substrate is made of thermoplastic polyurethane elastomer (TPU) or high-density polyethylene (HDPE). When the substrate is the thermoplastic polyurethane elastomer (TPU), the hardness of the thermoplastic polyurethane elastomer is 90A; When the substrate is high-density polyethylene, the melt flow rate of the high-density polyethylene is 10 g / 10 min.

3. The railway sleeper material of the modified polymer according to claim 1, characterized in that, The reinforcing phase is made of glass fiber or carbon fiber; The length of the glass fiber is 10-15 mm; The length of the carbon fiber is 8-12 mm.

4. The railway sleeper material of the modified polymer according to claim 1, characterized in that, The inorganic filler is nano-silica (SiO2) or montmorillonite (MMT). The particle size of the nano-silica is 50 nm; The montmorillonite used is organically modified montmorillonite.

5. The railway sleeper material of the modified polymer according to claim 1, characterized in that, The environmentally friendly flame retardant is a phosphorus-nitrogen compound; The phosphorus-nitrogen compounds are complexes of ammonium polyphosphate and melamine or complexes of phosphonates and guanidine salts. The UV stabilizer is a hindered amine or a benzotriazole.

6. A method for preparing railway sleeper material of a modified polymer as described in any one of claims 1-5, characterized in that, include: Weigh the substrate, reinforcing phase, inorganic filler, silane coupling agent, environmentally friendly flame retardant, and UV stabilizer according to the mass percentages described in claim 1. The inorganic filler is mixed with the silane coupling agent, dispersed by a high-speed mixer, and then dried to obtain the pretreated inorganic filler. The substrate, the pretreated inorganic filler, the reinforcing phase, the environmentally friendly flame retardant, and the UV stabilizer are added to a twin-screw extruder for melt blending, followed by extrusion granulation to obtain a modified polymer railway sleeper material.

7. The method for preparing railway sleeper material of modified polymer according to claim 6, characterized in that, The high-speed mixer operates at a speed of 1500-2000 rpm and a dispersion time of 15-20 min; the drying temperature is 60-80℃ and the drying time is 2-3 h.

8. The method for preparing railway sleeper material of modified polymer according to claim 6, characterized in that, When the substrate is the thermoplastic polyurethane elastomer, the temperature of the twin-screw extruder for blending extrusion is set to 180-200℃, with zone 1 at 180℃, zone 2 at 190℃, zone 3 at 200℃, and the die head at 200℃, and the screw speed is 200-300 rpm. When the substrate is high-density polyethylene, the temperature of the twin-screw extruder for blending extrusion is set to 190-220℃, with zone 1 at 190℃, zone 2 at 210℃, zone 3 at 220℃, and the die head at 210℃, and the screw speed is 300-400 rpm.

9. A railway sleeper, characterized in that, Railway sleeper materials including the modified polymers as described in any one of claims 1-5.

10. A method for preparing railway sleepers as described in claim 9, characterized in that, include: Railway sleeper materials made of modified polymers are used to prepare sleeper blanks by extrusion molding or injection molding. The sleeper blanks are then subjected to dynamic vulcanization crosslinking treatment at 160-180℃ for 30-60 minutes to obtain finished railway sleepers with a crosslinking density ≥85%.

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