A damping rubber composition for rail fasteners and preparation method thereof

Abstract

The present invention discloses a damping rubber composition for rail fasteners and its preparation method. The damping rubber composition is characterized by comprising the following raw materials, measured by weight: 100 parts of composite rubber, 25-35 parts of damping particles, 15-20 parts of sheet structure filler, 5-10 parts of plasticizer, 5-10 parts of tackifier, 3-5 parts of high-temperature resistant fiber, 2-4 parts of vulcanizer, 3-5 parts of activator, 2-2.5 parts of accelerator, and 1-3 parts of antioxidant. The composite rubber is a composite of EPDM rubber, natural rubber, and nitrile rubber. The damping particles are elastic particles obtained by filling aerogel nanopores with asphalt and a glycidyl methacrylate-modified elastomer. The damping particles are dispersed in the rubber system, enhancing the mobility of the rubber molecular chains, generating significant internal friction to dissipate energy and induce hysteretic deformation. The elastic pad used in rail fasteners exhibits excellent damping performance, aging resistance, and load impact fatigue resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of rail transportation, and in particular to a damping rubber composition for rail fasteners and a preparation method thereof. Background Art

[0002] The rapid development of rail transit has placed higher technical demands on track structures and related components. High-speed and heavy-load trains, in particular, require not only sufficient track support but also excellent vibration damping and isolation performance. High-performance damping reduces noise and vibration during train operation, enhancing passenger comfort. Furthermore, it prevents fatigue from repeated loads, ensuring the lifespan and operational safety of high-speed trains.

[0003] Rail fasteners are essential components for securing rails to sleepers, and subrail rubber pads are crucial elastic elements in the rail fastening system. The subrail rubber pads used in the fastening system provide crucial support for the smooth and safe operation of trains. During train operation, tracks are subject to significant pressure and frequent alternating shocks. The high elasticity and excellent damping properties of the subrail rubber pads effectively mitigate the impact forces between rails and sleepers, improving train operation smoothness and comfort, extending track life, and reducing the frequency of repairs and replacements.

[0004] Currently, rail fastener pads are widely used in rail transit systems, including high-speed railways, heavy-haul railways, and urban rail transit. Ballastless track, in particular, is gaining popularity, where the entire track system's vibration damping protection is provided by the fastener pads. Consequently, higher requirements are placed on the pads' aging resistance, long-term serviceability, high-load damping performance, and effective damping temperature range.

[0005] According to the technical requirements of existing rail fastener elastic pads, in accordance with GB / T21527-2008, "Elastic Pads for Rail Transit Fastener Systems," EPDM rubber is typically used to manufacture the pads, which effectively absorbs vibration energy. However, with the increasing demand for higher-level vibration damping, the damping performance of EPDM alone is limited, and it is prone to aging and cracking over time, leading to a gradual decline in its shock absorption and vibration isolation performance. Patent Publication No. CN107337814B discloses a high-damping rubber material. This material utilizes a combination of hindered phenols and hindered amines to enhance weak bond formation, thereby improving the damping performance of the rubber material. Lamellar fillers also create a barrier effect against external heat, oxygen, and ozone, preventing aging of the rubber material. Patent Publication No. CN106543510B discloses a high-damping rubber material and its preparation method. By introducing multiple hydrogen-bonding units or metal ligands into the rubber's molecular chain, the material utilizes the reversible breakage and regeneration of multiple hydrogen bonds and metal coordination bonds, thereby dissipating energy and improving the rubber's damping performance.

[0006] While existing technologies have improved the damping performance of rubber, their effective damping temperature range is relatively narrow, and their fatigue resistance and mechanical properties under high loads remain significantly deficient. To further enhance the damping performance of rail fastener elastic pads, improve train operation smoothness, and enhance high-load impact resistance and fatigue resistance, the proposed group standard T / ZZB 1443-2019, "Rail Fastener Underrail (Rubber Composite) Pads," sets higher technical requirements for the comprehensive performance of rail rubber pads. Summary of the Invention

[0007] In order to improve the damping effect and load impact fatigue resistance of rubber used in rail fasteners, the present invention discloses a damping rubber for rail fasteners. The rubber is improved by damping particles. When used in the pad of the rail fastener, the damping rubber has good mechanical properties and the ability to resist rapid impact loads; the effective damping temperature range is broadened, and the better damping performance effectively absorbs and alleviates the impact caused by high-speed vibration, thereby maintaining the stability of the train.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] The present invention provides a damping rubber for rail fasteners, characterized in that it comprises the following raw materials measured by weight: 100 parts of composite rubber, 25-35 parts of damping particles, 15-20 parts of sheet structure filler, 5-10 parts of plasticizer, 5-10 parts of tackifier, 3-5 parts of high-temperature resistant fiber, 2-4 parts of vulcanizer, 3-5 parts of activator, 2-2.5 parts of accelerator, and 1-3 parts of antioxidant; wherein:

[0010] The composite rubber is a compound of EPDM rubber, natural rubber and nitrile rubber;

[0011] The damping particles are elastic particles obtained by filling aerogel nanopores with asphalt and glycidyl methacrylate modified elastomer.

[0012] Preferably, the composite rubber is a mixture of EPDM, natural rubber, and nitrile rubber in a mass ratio of 10:(3-8):(1-2). EPDM has excellent resistance to high and low temperatures, maintaining good elasticity at both high and low temperatures. It also exhibits excellent ozone and UV resistance, making it suitable for long-term outdoor use. Natural rubber has excellent elasticity, stretchability, and abrasion resistance, which aids the rubber in improving damping performance. Nitrile rubber has excellent heat resistance and a high glass transition temperature, which aids the rubber in improving rebound performance at high temperatures. The composite rubber broadens the damping temperature range, thereby maintaining a stable damping effect over a wide temperature range.

[0013] Preferably, the damping particles are elastic particles obtained by filling aerogel nanopores with a viscoelastic body formed by blending asphalt with a glycidyl methacrylate modified elastomer; wherein the aerogel is at least one of silica aerogel, alumina aerogel, and polyimide aerogel.

[0014] Further preferably, the aerogel has a porosity greater than 75% and a pore size less than 100 nm. Particularly preferably, the aerogel has a pore size less than 50 nm. Aerogels have a rich nanoporous structure, which, when used in rubber, forms abundant micropores. These nanopores effectively absorb energy generated by vibration, thereby reducing vibration in structures. The present invention produces elastic particles (i.e., damping particles) by pre-filling the aerogel's nanopores with a blend of asphalt and a glycidyl methacrylate-modified elastomer. Most of the asphalt and glycidyl methacrylate-modified elastomer are adsorbed within the aerogel's nanopores, forming a distribution pattern similar to nanocapsules. When the damping particles are dispersed in a rubber system, the asphalt / glycidyl methacrylate-modified elastomer blend within the aerogel's nanopores exhibits excellent viscoelastic properties, effectively dissipating energy generated by rubber vibration, reducing vibration noise and significantly improving the rubber's damping performance. The aerogel's excellent interfacial properties increase the dispersion interface of the damping particles in the rubber, creating a dispersion pattern similar to that of nanocapsules. This increases the contact surface and enhances the material's internal friction, thereby dissipating energy. Viscoelastic damping particles have the characteristics of both viscoelastic energy dissipation and elastic energy storage. When subjected to external force, they will produce hysteretic deformation, instantly dissipating energy and playing a role in vibration reduction.

[0015] More preferably, the damping particles are formed by blending asphalt with glycidyl methacrylate modified elastomer to form a viscoelastic body and aerogel in a volume ratio of 2:(3-4), and the viscoelastic body is pre-filled in the nanopores of the aerogel by hot melting.

[0016] More preferably, the viscoelastic material is a composite of asphalt and a glycidyl methacrylate-modified elastomer in a mass ratio of 10:(2-5). Asphalt is a non-Newtonian fluid. When used in rubber filled aerogels, its ability to resist deformation increases under impact or increased load, resulting in more efficient energy absorption and cushioning. Particularly preferably, the asphalt is 70# or 90# asphalt, which has a low kinematic viscosity and excellent high-load impact resistance.

[0017] Preferably, the glycidyl methacrylate-modified elastomer is a glycidyl methacrylate (GMA)-modified elastomer, such as the commercially available GMA-modified vinyl elastomer Fine-Blend® SOG-03. The introduction of polar groups allows the damping particles to be evenly dispersed within the rubber matrix, broadening the effective damping temperature range and enhancing damping performance. Further preferably, the glycidyl methacrylate-modified elastomer is at least one of a GMA-modified thermoplastic polyester elastomer, a GMA-modified thermoplastic polyurethane elastomer, a GMA-modified styrene-butadiene-styrene triblock copolymer, a GMA-modified ethylene acrylic acid copolymer, and a GMA-modified ethylene-vinyl acetate copolymer.

[0018] Preferably, the sheet structure filler is at least one of mica powder, kaolin, montmorillonite, and pyrophyllite. By dispersing the layered inorganic matter, the internal friction of the rubber material is increased to dissipate energy, thereby achieving the effects of energy absorption, vibration reduction, and preventing aging.

[0019] Preferably, the plasticizer is at least one of pine tar, dioctyl phthalate, and aromatic oil.

[0020] Preferably, the tackifier is at least one of coumarone resin, rosin resin, alkylphenolic resin, petroleum resin, and terpene resin. Tackifiers have the functions of softening, reinforcing, plasticizing, increasing viscosity, and dispersing rubber. They can enhance the adhesion between rubber and fibers and fillers, improving the uniformity of rubber extrusion.

[0021] Preferably, the high-temperature-resistant fiber is ceramic fiber, glass fiber, or a polymer fiber that can withstand temperatures exceeding 190°C for a long time. The polymer fiber that can withstand temperatures exceeding 190°C for a long time is preferably at least one of polyphenylene sulfide fiber and polytetrafluoroethylene fiber. These fibers can effectively enhance the tensile strength and stiffness of rubber, enabling it to withstand greater tension and pressure while maintaining good damping properties. Selecting polymer fibers that can withstand temperatures exceeding 190°C for a long time ensures that the fibers will not break during high-temperature vulcanization.

[0022] More preferably, the high temperature resistant fiber is a fiber with a diameter of 10-20 μm and a length of 3-6 mm.

[0023] Preferably, the vulcanizing agent is sulfur.

[0024] Preferably, the activator is at least one of zinc oxide, stearic acid, zinc carbonate, and magnesium oxide; the activator is dispersed in the rubber to mainly assist in the later vulcanization molding, enhance the vulcanization activity, accelerate the vulcanization reaction, and shorten the vulcanization time.

[0025] Preferably, the accelerator is selected from at least one of CZ (N-cyclohexyl-2-benzothiazole sulfenamide), TBBS (N-tert-butyl-2-benzothiazole sulfenamide), NOBS (N-oxydiethylene-2-benzothiazole sulfenamide), DZ (N,N'-dicyclohexyl-2-benzothiazole sulfenamide, TMTD (tetramethylthiuram disulfide), TMTM (tetramethylthiuram monosulfide), TETD (tetraethylthiuram disulfide), DPTT (pentamethylenethiuram hexasulfide), ZDC (zinc diethyldithiocarbamate), BZ (zinc dibutyldithiocarbamate), and PZ (zinc dimethyldithiocarbamate). The addition of the accelerator accelerates the cross-linking reaction between the vulcanizing agent and the rubber molecules during vulcanization molding, thereby shortening the vulcanization time and reducing the vulcanization temperature.

[0026] Preferably, the antioxidants are selected from antioxidant RD, antioxidant NBC, and antioxidant DNP in a mass ratio of 10:(3-5):(2-3). Antioxidant RD has multiple effects of anti-oxidation, anti-ozone, heat aging, and hydrolysis; antioxidant NBC has air aging resistance; and antioxidant DNP has heat and oxygen aging resistance. It can absorb and neutralize free radicals in the environment, thereby preventing damage to the material caused by free radicals and preventing heat and oxygen aging. Through this synergistic effect, rubber aging can be effectively delayed, extending the service life of the rubber.

[0027] The present invention also provides a method for preparing the damping rubber for rail fasteners, which is characterized in that the specific preparation method is as follows:

[0028] S1. Asphalt and glycidyl methacrylate-modified elastomer were mixed uniformly and added to a co-rotating twin-screw extruder for hot melt extrusion. A feeding port was set in the fifth section of the co-rotating twin-screw extruder, and aerogel was continuously added by volume measured using a loss-in-weight scale. The aerogel micropores absorbed the completely hot-melt asphalt and glycidyl methacrylate-modified elastomer and extruded into sheets through a die to obtain damping particles.

[0029] S2. Add 100 parts of composite rubber, 5-10 parts of plasticizer, and 5-10 parts of tackifier into an internal mixer and mix for 3-5 minutes, then add 25-35 parts of damping particles, 10-15 parts of sheet structure filler, 3-5 parts of high temperature resistant fiber, 3-5 parts of activator, and 1-3 parts of antioxidant and continue mixing for 5-8 minutes, and control the rotor temperature of the internal mixer to be lower than 120°C; put the rubber material into an open mill, and control the roller temperature of the open mill to 50-60°C with circulating cooling water in the roller. When the rubber material forms a continuous roll, add 2-4 parts of vulcanizer and 2-2.5 parts of accelerator, make triangular packages 3-5 times, and then thinly pass 3 times to evenly disperse the material before unrolling to obtain a damping rubber composition for rail fasteners.

[0030] For the above-mentioned damping rubber composition, when it is used to make elastic pads for track fasteners, the operating process adopted is as follows: the damping rubber composition is added to a pin-type cold feed extruder, and the screw temperature is controlled: the temperature of zone 1 is 65°C, the temperature of zone 2 is 60°C, the temperature of zone 3 is 55°C, and the temperature of the die head is 70°C; the rubber material is homogenized and kneaded by being divided and sheared by multiple pins on the screw, and different die openings are set at the die to obtain sheet-like rubber blanks with a thickness of 2-16 mm, which are placed on a louver machine for 4-24 hours, cut and placed in a mold, and vulcanized for 10-15 minutes under a pressure of 10-15 MPa and a temperature of 170°C-180°C to obtain elastic pads for track fasteners.

[0031] Compared with the prior art, the damping rubber composition and preparation method for rail fasteners of the present invention have the following beneficial effects:

[0032] 1. The present invention creatively blends asphalt and glycidyl methacrylate modified elastomer, pre-fills the aerogel nanopores to obtain damping particles, and disperses the damping particles in the rubber system. On the one hand, the nanostructure and high interface of the aerogel enable the asphalt / glycidyl methacrylate modified elastomer to be dispersed in the rubber system in the form of nano-microcapsules, thereby enhancing the mobility of the rubber molecular chains. When subjected to external forces, significant internal friction will be generated to dissipate energy and cause hysteresis deformation, thereby playing a vibration reduction role. On the other hand, the asphalt / glycidyl methacrylate modified elastomer filled in the aerogel nanostructure can prevent thermal and oxygen aging, thereby ensuring the long life of the rubber pad and long-term damping stability.

[0033] 2. The present invention compounds EPDM rubber, natural rubber and nitrile rubber to broaden the damping temperature range, thereby maintaining a stable damping effect in a wider temperature range.

[0034] 3. The present invention uses the synergy of damping particles, sheet-structured fillers, and high-temperature resistant fibers to enable the rubber to have good mechanical properties and dynamic viscoelastic behavior, and has excellent deformation resistance, impact resistance, and fatigue resistance under alternating track loads. At the same time, it maintains excellent damping performance to reduce vibration amplitude and improve system stability and comfort.

[0035] 4. The technology of the present invention is easy to implement on a large scale, and the equipment and raw materials used are all conventionally available raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 tanδ-T is a graph showing the relationship between the damping factor and temperature of the samples of Examples 1-4 of the present invention. DETAILED DESCRIPTION

[0037] In order to make those skilled in the art further understand the technical means, technical objectives and technical effects achieved by the present invention, the present invention is described in detail below in conjunction with the embodiments. For raw materials, equipment and processes for which technical parameters are not specified, they are all conventional choices in the art.

[0038] Technical parameters of some raw materials and equipment used in the implementation plan:

[0039] EPDM rubber: brand EPDM 722P, ethylene content 70%, Mooney viscosity [ML(1+4)125℃] is 20MU, Dow, USA.

[0040] Glycidyl methacrylate modified elastomer: GMA modified vinyl elastomer, model Fine-Blend® SOG-03, GMA functional group content 2.0-3.0%, provided by Jiayirong Polymer (Shanghai) Co., Ltd.

[0041] Silica aerogel: Porosity greater than 90%, pore size 25-45nm.

[0042] Parallel co-rotating twin-screw extruder: Model SJWA-65, screw diameter Φ65mm, L / D=44, Changzhou JWELL Intelligent Chemical Equipment Co., Ltd.

[0043] Pin-type cold feed extruder: Model XJD-65, screw diameter Φ65mm, length-to-diameter ratio 12:1, Changzhou Daban Machinery Co., Ltd.

[0044] Double-roll mill: Model XK-660, Qingdao Junlin Machinery Co., Ltd.

[0045] Example 1

[0046] S1. 70# asphalt and GMA-modified vinyl elastomer SOG-03 were uniformly mixed in a mass ratio of 10:2 and added to a parallel co-rotating twin-screw extruder to form a viscoelastic mixture. The extrusion temperature of each screw zone was controlled as follows: 90°C in zone 1; 100°C in zone 2; 120°C in zone 3; 140°C in zone 4; 150°C in zone 5; 130°C in zone 6; 120°C in zone 7; 120°C in zone 8; 110°C in zone 9; and 110°C in zone 10. A feed port was set in the fifth zone of the parallel co-rotating twin-screw extruder. The viscoelastic mixture and silica aerogel were compounded in a volume ratio of 2:3. Silica aerogel was continuously added by volume using a loss-in-weight scale. The completely hot-melt asphalt and GMA-modified vinyl elastomer SOG-03 were adsorbed by the micropores of the silica aerogel and extruded through a die to form a sheet to obtain damping particles.

[0047] S2. EPDM rubber, natural rubber, and nitrile rubber are prepared into a composite rubber in a mass ratio of 10:3:2. 100 parts of the composite rubber, 6 parts of an aromatic oil plasticizer, and 5 parts of a coumarone resin tackifier are added to an internal mixer and kneaded for 5 minutes. Then, 25 parts of damping particles, 15 parts of mica powder, 5 parts of glass fiber (10 μm in diameter, 5 mm in length), 3 parts of a zinc oxide activator, and 2 parts of an antioxidant (antioxidant RD, antioxidant NBC, and antioxidant DNP are compounded in a mass ratio of 10:5:3) are added and kneaded for another 5 minutes. The rotor temperature of the internal mixer is controlled below 120°C. The rubber compound is placed on an open mill, and the roller temperature of the open mill is controlled to 50-60°C by circulating cooling water in the rollers. When the rubber compound forms a continuous roll, 2.5 parts of sulfur and 2 parts of a TMTD accelerator are added. The rubber compound is triangularly packaged four times, then thinly passed three times to evenly disperse the material before being removed from the roll to obtain a damping rubber composition for rail fasteners.

[0048] Example 2

[0049] S1. 70# asphalt and GMA-modified thermoplastic polyurethane elastomer were uniformly mixed in a mass ratio of 10:3, and added to a parallel co-rotating twin-screw extruder to be hot-melted into a viscoelastic body. The extrusion temperature of each zone of the screw was controlled as follows: 90°C in zone 1; 120°C in zone 2; 130°C in zone 3; 140°C in zone 4; 155°C in zone 5; 140°C in zone 6; 130°C in zone 7; 120°C in zone 8; 110°C in zone 9; and 110°C in zone 10. A feeding port was set in the fifth zone of the parallel co-rotating twin-screw extruder. The viscoelastic body and silica aerogel were composited in a volume ratio of 2:4. Silica aerogel was continuously added by volume using a loss-in-weight scale. The completely hot-melted asphalt and GMA-modified thermoplastic polyurethane elastomer were adsorbed by the micropores of the silica aerogel and extruded into sheets through a die to obtain damping particles.

[0050] S2. EPDM rubber, natural rubber, and nitrile rubber are prepared into a composite rubber in a mass ratio of 10:8:2. 100 parts of the composite rubber, 5 parts of an aromatic oil plasticizer, and 8 parts of a terpene resin tackifier are added to an internal mixer and kneaded for 3 minutes. Then, 30 parts of damping particles, 18 parts of mica powder, 5 parts of glass fiber (diameter 10 μm, length 5 mm), 5 parts of a zinc oxide activator, and 1 part of an antioxidant (antioxidant RD, antioxidant NBC, and antioxidant DNP are compounded in a mass ratio of 10:3:3) are added and kneaded for 8 minutes. The temperature of the internal mixer rotor is controlled below 120°C. The rubber compound is placed on an open mill, and the roller temperature of the open mill is controlled to 50-60°C by circulating cooling water in the roller. When the rubber compound forms a continuous roll, 2.8 parts of sulfur and 2 parts of a DZ accelerator are added. The rubber compound is triangularly packaged 5 times, then thinly passed 3 times to evenly disperse the material before being removed from the roll to obtain a damping rubber composition for rail fasteners.

[0051] Example 3

[0052] S1. 120# asphalt and GMA-modified vinyl elastomer SOG-03 were mixed uniformly in a mass ratio of 10:2 and added to a parallel co-rotating twin-screw extruder to form a viscoelastic body. The extrusion temperature of each zone of the screw was controlled as follows: 90°C in zone 1; 100°C in zone 2; 120°C in zone 3; 140°C in zone 4; 150°C in zone 5; 130°C in zone 6; 120°C in zone 7; 120°C in zone 8; 110°C in zone 9; and 110°C in zone 10. A feeding port was set in the fifth section of the parallel co-rotating twin-screw extruder. The viscoelastic body and silica aerogel were compounded in a volume ratio of 2:3. Silica aerogel was continuously added by volume using a loss-in-weight scale. The completely hot-melt asphalt and GMA-modified vinyl elastomer SOG-03 were adsorbed by the micropores of the silica aerogel and extruded into sheets through a die to obtain damping particles.

[0053] S2. EPDM rubber, natural rubber, and nitrile rubber are prepared into a composite rubber in a mass ratio of 10:4:2. 100 parts of the composite rubber, 10 parts of a pine tar plasticizer, and 5 parts of a rosin resin tackifier are added to an internal mixer and kneaded for 5 minutes. Then, 35 parts of damping particles, 20 parts of pyrophyllite, 5 parts of polyphenylene sulfide fibers (10 μm in diameter, 3 mm in length), 3 parts of a stearic acid activator, and 2 parts of an antioxidant (antioxidant RD, antioxidant NBC, and antioxidant DNP are compounded in a mass ratio of 10:5:2) are added and kneaded for 8 minutes. The temperature of the internal mixer rotor is controlled below 120°C. The rubber compound is placed on an open mill, and the roller temperature of the open mill is controlled to 50-60°C by circulating cooling water in the rollers. When the rubber compound forms a continuous roll, 2.5 parts of sulfur and 2 parts of a TMTD accelerator are added. The rubber compound is triangularly packaged three times, then thinly passed three times to evenly disperse the material before being removed from the roll to obtain a damping rubber composition for rail fasteners.

[0054] Example 4

[0055] S1. 70# asphalt and GMA-modified vinyl elastomer SOG-03 were uniformly mixed in a mass ratio of 10:5 and added to a parallel co-rotating twin-screw extruder to form a viscoelastic mixture. The extrusion temperature of each zone of the screw was controlled as follows: 90°C in zone 1; 100°C in zone 2; 120°C in zone 3; 140°C in zone 4; 150°C in zone 5; 130°C in zone 6; 120°C in zone 7; 120°C in zone 8; 110°C in zone 9; and 110°C in zone 10. A feed port was set in the fifth section of the parallel co-rotating twin-screw extruder. The viscoelastic mixture and silica aerogel were weighed in a volume ratio of 2:4. Silica aerogel was continuously added by volume using a loss-in-weight scale. The completely hot-melt asphalt and GMA-modified vinyl elastomer SOG-03 were adsorbed by the micropores of the silica aerogel and extruded through a die to form a sheet to obtain damping particles.

[0056] S2. Prepare composite rubber by mixing EPDM rubber, natural rubber, and nitrile rubber in a mass ratio of 10:5:2. Add 100 parts of composite rubber, 5 parts of aromatic oil plasticizer, and 10 parts of coumarone resin tackifier into an internal mixer and mix for 5 minutes. Then add 35 parts of damping particles, 20 parts of mica powder, 5 parts of glass fiber (diameter 10 μm, length 5 mm), 3 parts of magnesium oxide activator, and antioxidants (anti-aging agent RD, antioxidant NBC, and antioxidant DNP). The rubber compound is compounded in a mass ratio of 10:5:3) and 1-3 parts thereof are continuously mixed for 5 minutes, and the temperature of the internal mixer rotor is controlled below 120°C; the rubber compound is put into an open mixer, and the roller temperature of the open mixer is controlled to 50-60°C by circulating cooling water in the roller. When the rubber compound forms a continuous roll, sulfur 3.0, 1 part of CZ accelerator, and 1 part of TMTD accelerator are added, and the rubber compound is triangularly packaged 5 times, and then thinly passed 3 times to evenly disperse the material before being unrolled to obtain a damping rubber composition for rail fasteners.

[0057] Comparative Example 1

[0058] During the implementation of Example 1, the damping particles were removed, and the performance changes of the damping rubber after removing the damping particles were analyzed.

[0059] Comparative Example 2

[0060] In the implementation process of Example 1, prefabricated damping particles were eliminated, and instead 70# asphalt, SOG-03, and silica aerogel were directly added in equal amounts in step S2.

[0061] Comparative Example 3

[0062] During the implementation of Example 1, the fibers were removed, and the performance changes of the damping rubber after the fibers were removed were analyzed.

[0063] Comparative Example 4

[0064] During the implementation of Example 1, calcium carbonate was used to replace mica, and the performance changes of the damping rubber were analyzed.

[0065] Comparative Example 5

[0066] During the implementation of Example 1, the GMA-modified vinyl elastomer was omitted when prefabricating the damping particles in step S1, and the performance changes of the damping rubber were analyzed.

[0067] Performance evaluation and analysis test:

[0068] The damping rubber compositions of Examples 1-4 and Comparative Examples 1-5 were added to a pin-type cold feed extruder. The screw temperatures were controlled at 65°C in Zone 1, 60°C in Zone 2, 55°C in Zone 3, and 70°C in the die. Sheets were extruded through the die through shearing and kneading, placed on a louver machine for 24 hours, cut, and placed in a mold. Test specimens were vulcanized for 15 minutes at a pressure of 15 MPa and a temperature of 170°C to obtain the test specimens. The comprehensive performance of the materials was evaluated by testing the specimens' basic mechanical properties, hardness, aging resistance, load impact fatigue resistance, and damping performance.

[0069] (1) Shore hardness test

[0070] The Shore A hardness of the samples was measured according to GB / T 531.1-2008, "Rubber, vulcanized or thermoplastic—Test method for indentation hardness—Part 1: Shore durometer method (Shore hardness)." The test results are shown in Table 1.

[0071] (2) Basic mechanical properties test

[0072] With reference to the standard GB / T528 “Determination of tensile stress-strain properties of vulcanized or thermoplastic rubber”, after punching out the specimens, the tensile strength, elongation at break, and 200% modulus of elongation were tested at room temperature at a tensile rate of 500 mm / min. The test results are shown in Table 1.

[0073] (3) Aging resistance test

[0074] According to the standard GB / T 3512, "Vulcanized rubber or thermoplastic rubber - Accelerated aging and heat resistance tests in hot air," the hardness and mechanical properties of the samples were tested after aging at 100°C for 72 hours under air supply conditions. The test results are shown in Table 1.

[0075] Table 1 Mechanical properties and aging resistance of samples

[0076]

[0077] (IV) Damping performance test

[0078] When vulcanized rubber specimens are subjected to alternating stress, the strain lags behind the stress due to the movement of the molecular chains. This hysteresis causes the material to lose mechanical energy, resulting in damping properties. The damping factor, tanδ, the tangent of the phase angle δ between the strain lag and the stress, is used to characterize the damping properties.

[0079] Referring to the standard GB / T 9870 "Rubber, vulcanized or thermoplastic — Determination of dynamic properties — Part 2: Low-frequency torsional pendulum method" and the forced vibration method, the loss modulus E″ and storage modulus E′ of the samples were tested at a frequency of 100 Hz at -50°C, -30°C to 10°C, 10°C, 30°C, and 50°C. The damping factor, tan δ, was calculated by calculating the ratio of the loss modulus E″ to the storage modulus E′. The test results are shown in Table 2.

[0080] Table 2 Damping performance of samples

[0081]

[0082] (5) High load impact fatigue test

[0083] Following the test method in Appendix C of GB-T21527, "Elastic Pads for Rail Transit Fastener Systems," a load of 150 kN was applied to the specimens at a frequency of 4 Hz for 3 million cycles. The specimens' permanent deformation and change in static stiffness were measured to assess their ability to withstand the load impact. Permanent deformation less than 10% and change in static stiffness less than 15% were considered acceptable. The test results are shown in Table 3.

[0084] Table 3 Load impact fatigue resistance of samples

[0085]

[0086] The above test data show that the damping rubber of the present invention has excellent mechanical properties and heat-resistant oxidation properties; it has significant viscoelastic characteristics, so that its strain lags significantly behind the stress and has good damping performance. Figure 1 The figure shows the relationship between the damping factor and temperature, tanδ-T, for Examples 1-4. The damping factor, tanδ, reaches its peak at approximately 10°C and remains stable. Within the temperature range of -50°C to 50°C, the damping factor, tanδ, remains ≥ 0.3, demonstrating a wide effective damping temperature range and strong adaptability to operating conditions. In particular, under load impact, the samples exhibit minimal permanent deformation and a low rate of change in static stiffness, demonstrating excellent long-term resistance to impact deformation and fatigue.

[0087] The basic principles, main features and advantages of the present invention are shown and described above. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A damping rubber for rail fasteners, characterized in that: The invention comprises the following raw materials measured by weight: 100 parts of composite rubber, 25-35 parts of damping particles, 15-20 parts of sheet structure filler, 5-10 parts of plasticizer, 5-10 parts of tackifier, 3-5 parts of high temperature resistant fiber, 2-4 parts of vulcanizing agent, 3-5 parts of activator, 2-2.5 parts of accelerator, and 1-3 parts of antioxidant; wherein: The composite rubber is a compound of EPDM rubber, natural rubber and nitrile rubber; The damping particles are elastic particles obtained by filling aerogel nanopores with a viscoelastic body formed by blending asphalt and a glycidyl methacrylate modified elastomer; wherein the viscoelastic body and the aerogel are filled and compounded in a volume ratio of 2:(3-4); the viscoelastic body is formed by blending asphalt and a glycidyl methacrylate modified elastomer in a mass ratio of 10:(2-5); the aerogel is at least one of silica aerogel, alumina aerogel, and polyimide aerogel, having a porosity greater than 75% and a pore size less than 100 nm; The sheet structure filler is at least one of mica powder, kaolin, montmorillonite and pyrophyllite.

2. The damping rubber for rail fasteners according to claim 1, characterized in that: The composite rubber is a compound of EPDM rubber, natural rubber and nitrile rubber in a mass ratio of 10:(3-8):(1-2).

3. The damping rubber for rail fasteners according to claim 1, characterized in that: The glycidyl methacrylate modified elastomer is at least one of a GMA-modified thermoplastic polyester elastomer, a GMA-modified thermoplastic polyurethane elastomer, a GMA-modified styrene-butadiene-styrene triblock copolymer, a GMA-modified ethylene acrylic acid copolymer, and a GMA-modified ethylene-vinyl acetate copolymer.

4. The damping rubber for rail fasteners according to claim 1, characterized in that: The plasticizer is at least one of pine tar, dioctyl phthalate, and aromatic oil; the tackifier is at least one of coumarone resin, rosin resin, alkylphenol-formaldehyde resin, petroleum resin, and terpene resin; the vulcanizing agent is sulfur; the activator is at least one of zinc oxide, stearic acid, zinc carbonate, and magnesium oxide; the accelerator is at least one of CZ, TBBS, NOBS, DZ, TMTD, TMTM, TETD, DPTT, ZDC, BZ, and PZ; and the antioxidant is selected from antioxidant RD, antioxidant NBC, and antioxidant DNP in a mass ratio of 10:(3-5):(2-3).

5. The damping rubber for rail fasteners according to claim 1, characterized in that: The high temperature resistant fiber is at least one of ceramic fiber, glass fiber, polyphenylene sulfide fiber and polytetrafluoroethylene fiber with a diameter of 10-20 μm and a length of 3-6 mm.

6. A method for preparing a damping rubber for rail fasteners according to any one of claims 1 to 5, characterized in that: The specific preparation method is as follows: S1. Asphalt and glycidyl methacrylate-modified elastomer were mixed uniformly and added to a co-rotating twin-screw extruder for hot melt extrusion. A feeding port was set in the fifth section of the co-rotating twin-screw extruder, and aerogel was continuously added by volume measured using a loss-in-weight scale. The aerogel micropores absorbed the completely hot-melt asphalt and glycidyl methacrylate-modified elastomer and extruded into sheets through a die to obtain damping particles. S2. Add 100 parts of composite rubber, 5-10 parts of plasticizer, and 5-10 parts of tackifier into an internal mixer and mix for 3-5 minutes, then add 25-35 parts of damping particles, 10-15 parts of sheet structure filler, 3-5 parts of high temperature resistant fiber, 3-5 parts of activator, and 1-3 parts of antioxidant and continue mixing for 5-8 minutes, and control the rotor temperature of the internal mixer to be lower than 120°C; put the rubber material into an open mill, and control the roller temperature of the open mill to 50-60°C with circulating cooling water in the roller. When the rubber material forms a continuous roll, add 2-4 parts of vulcanizer and 2-2.5 parts of accelerator, make triangular packages 3-5 times, and then thinly pass 3 times to evenly disperse the material before unrolling to obtain a damping rubber composition for rail fasteners.

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