Treadmill noise reduction muting method

Abstract

The present application relates to a treadmill noise reduction mute method, a buffer pad body is arranged between a running plate and a frame, the buffer pad body is composed of a buffer pad base body with an axial cavity inside and a shock absorbing filler filled in the axial cavity of the buffer pad base body, the buffer pad base body is made of a low noise TPS elastomer composite material, the low noise TPS elastomer composite material includes the following weight parts 30-50 parts of butenyl-polydiene-styrene block copolymer, 15-25 parts of polypropylene, 30-50 parts of naphthenic oil, 5-15 parts of nano filler, 3-8 parts of plasticizer, the low noise TPS elastomer composite material has a uniform closed cell microcellular structure with a pore size of 50-200 mu m inside. The buffer pad made of the material has excellent shock absorbing and noise reduction performance, and can effectively solve the problems of limited damping performance of traditional rubber materials and easy permanent deformation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of treadmill shock absorption, in particular to a treadmill noise reduction method. BACKGROUND

[0002] As a common indoor fitness equipment, the noise and vibration generated by the running machine have always been a concern. In order to improve the user experience and reduce the interference to the downstairs residents, the existing technology generally erects multiple buffer pads between the frame and the running board of the running machine. These buffer pads have two main functions: first, to absorb the impact force generated by the runner on the running board during running, protecting the user's joints; second, to change the foot feeling of the runner, providing a more comfortable exercise experience.

[0003] Currently, the composite materials used for shock absorption and noise reduction are mostly natural rubber or silicone, such as CN115960400B, CN105367834A, etc. These materials have a certain elasticity, but they have obvious shortcomings in solving the transmission of low-frequency impact noise of the running machine:

[0004] 1. Limited damping performance, the damping coefficient of natural rubber and silicone is relatively fixed, and for the wideband impact vibration generated by running, the energy absorption and dissipation efficiency is not high, resulting in a considerable part of the impact energy being transmitted to the ground and building structure through the running board, frame and foot pad, which is converted into significant abnormal noise affecting the downstairs residents.

[0005] 2. Performance easily attenuates, natural rubber is prone to permanent deformation under repeated compression for a long time, resulting in gradual weakening of the shock absorption effect and exacerbation of the noise problem.

[0006] 3. Single function, traditional solid rubber or silicone pads mainly provide simple cushioning, which is difficult to achieve efficient sound absorption and noise reduction through the material itself structure, and it is difficult to balance the contradiction between "soft foot feeling" and "stable support". SUMMARY

[0007] The purpose of the present application is to overcome the shortcomings of the prior art and provide a treadmill noise reduction method.

[0008] To achieve the above purpose, the present application adopts the following technical solutions:

[0009] A buffer pad is installed between the running board and the frame. The buffer pad consists of a buffer pad matrix with an internal axial cavity and shock-absorbing filler injected into the axial cavity of the buffer pad matrix. The buffer pad matrix is ​​made of low-noise TPS elastomer composite material, which includes the following parts by weight: 30-50 parts butenyl-polydiene-styrene block copolymer, 15-25 parts polypropylene, 30-50 parts naphthenic oil, 5-15 parts nanofiller, and 3-8 parts plasticizer. The low-noise TPS elastomer composite material has a uniform closed-cell micro-foamed structure with a pore size of 50-200 μm.

[0010] This design uses a TPS (butenyl-polydiene-styrene) matrix composed of butenyl-polydiene-styrene block copolymer, polypropylene (PP), and naphthenic oil to form the basic framework of the material. The butenyl-polydiene-styrene block copolymer provides high elasticity and resilience, while the PP forms the hard segments, providing support strength and reducing material costs. The naphthenic oil fully swells the rubber phase of the butenyl-polydiene-styrene block copolymer, improving processing fluidity. The proportions of these three components balance elasticity and rigidity; excessive butenyl-polydiene-styrene block copolymer would result in an overly soft material and increased costs, while excessive PP would sacrifice the necessary flexibility for shock absorption.

[0011] Preferably, the plasticizer is epoxidized soybean oil or phthalate plasticizer.

[0012] Preferably, the nanofiller is a quaternary ammonium salt modified nanofiller with a particle size of 20-100 nm, specifically one of nano-calcium carbonate or quaternary ammonium salt modified nano-montmorillonite.

[0013] The addition of nanofillers mainly plays a role in heterogeneous nucleation and reinforcement. Their uniform dispersion in the matrix can effectively improve the strength of the cell walls and prevent cell merging or collapse during the foaming process. The particle size and content need to be precisely controlled. If the particle size is too low, it will be difficult to form an effective reinforcing network. If the particle size is too high, it will easily agglomerate and become stress concentration points.

[0014] The specific modification process of quaternary ammonium salt modified nano-calcium carbonate or quaternary ammonium salt modified nano-montmorillonite is as follows: Dry nano-calcium carbonate or natural nano-montmorillonite is placed in a high-speed mixer and preheated at 80-90℃ for 15-20 minutes to remove surface adsorbed water. Then, a quaternary ammonium salt modifier (hexadecyltrimethylammonium bromide is suitable for nano-calcium carbonate, and dioctadecyldimethylammonium chloride is suitable for nano-montmorillonite) is slowly added at a ratio of 1.5%-3% by mass of the nanofiller. Simultaneously, 0.5%-1% anhydrous ethanol by mass of the filler is added as a dispersion medium. The modifier is spread and the high-speed mixer is kept at 800-1200 rpm. The mixture is stirred at a constant temperature of 90-110℃ for 40-60 minutes. During this time, the material temperature is monitored in real time by infrared thermography to avoid local overheating. After modification, the material is transferred to a vacuum drying oven and vacuum dried at 105-110℃ and -0.08~-0.09MPa for 2-3 hours to remove residual solvent and moisture. Finally, the material is pulverized at high speed and passed through a 200-mesh sieve to obtain quaternary ammonium salt modified nano-calcium carbonate or nano-montmorillonite with hydrophobic surface and excellent dispersibility.

[0015] For inorganic fillers such as nano-calcium carbonate and nano-montmorillonite in this invention, the core advantage of quaternary ammonium salt modification is that it can reduce the surface polarity of the filler through long-chain alkyl groups, improve its compatibility with non-polar TPS substrates (butenyl-polydiene-styrene block copolymer, polypropylene), completely solve the problem of filler agglomeration, and make it uniformly dispersed at the nanoscale and strengthen the interfacial bonding with the matrix through the "anchoring effect". This not only enhances the strength of the cell wall and the tensile and fatigue properties of the material, avoiding permanent deformation, but also plays the role of dispersant and internal lubricant to optimize the processing rheological properties, helping to accurately control the 50-200μm uniform closed-cell micro-foam structure. At the same time, the interfacial micro-slippage and molecular chain friction between the filler and the matrix synergistically improve the damping performance, efficiently dissipate impact energy, and significantly improve the vibration reduction and noise reduction effect. Moreover, the modification process is simple, cost-controllable, and highly compatible with existing production processes, which is fully adapted to the core technical requirements and industrial application scenarios of this invention.

[0016] Preferably, the plasticizer is epoxidized soybean oil or phthalate plasticizer.

[0017] Plasticizers reduce melt viscosity through the lubrication effect between molecular chains, which is crucial for the uniform nucleation and growth of bubbles during the subsequent foaming process. However, the amount added must be carefully controlled, as excessive amounts can severely weaken the matrix strength and cause foaming to break down.

[0018] Preferably, the preparation method of the low-noise TPS elastomer composite material includes the following steps:

[0019] Raw material preparation and pretreatment: Prepare butenyl-polydiene-styrene block copolymer, polypropylene, naphthenic oil, nanofiller and plasticizer according to the formula weight parts, and pre-dry the butenyl-polydiene-styrene block copolymer and polypropylene.

[0020] Blending and plasticizing: The pretreated components are blended in an internal mixer at 160-180℃ for 8-15 minutes to obtain a premixed blend; then the premixed blend is transferred to a twin-screw extruder and melt-blended and plasticized under screw shear and temperature conditions of 170-190℃. After extrusion, cooling and granulation, a composite masterbatch is obtained.

[0021] Foaming molding: The composite masterbatch is foamed by adding a chemical foaming agent and thermally activating and decomposing it, or by impregnating it with supercritical fluid and then rapidly depressurizing it, or by a combination of chemical and physical composite foaming, so that a uniform closed-cell micro-foamed structure with a pore size of 50-200μm is formed inside it.

[0022] Product post-processing and assembly: The foamed cushioning pad is trimmed, filled with silicone gel or polyurethane foam material, and cured to obtain the final product.

[0023] The core of the preparation process lies in ensuring uniform dispersion of components and precise control of cell structure. High temperature and strong shear force during the blending and plasticizing stage are crucial for achieving nanoscale dispersion of nanofillers in a viscoelastic matrix. Insufficient temperature leads to poor plasticization and defects, while insufficient shear force results in uneven filler dispersion, becoming a structural weakness. Foaming is the final hurdle in achieving the technology. Chemical foaming relies on the decomposition and gasification of the foaming agent at a specific temperature, requiring precise matching of the processing temperature window. Supercritical fluid foaming relies on its penetration into the polymer matrix under high pressure, forming a supersaturated state and inducing nucleation during rapid depressurization. Its pressure and temperature directly determine the solubility and the final cell density and size. Both foaming mechanisms require the matrix to have suitable melt strength; too high a strength will inhibit bubble expansion, while too low a strength will prevent the encapsulation of gas to form closed cells.

[0024] Preferably, the blending and plasticizing process is carried out in a twin-screw extruder with a screw speed of 200-400 rpm and a material residence time of 1-3 min.

[0025] Preferably, the foaming process is chemical foaming: 0.5-2 parts by weight of a chemical foaming agent is added during the blending and plasticizing step, wherein the chemical foaming agent is azodicarbonamide or 4,4'-oxobisbenzenesulfonylhydrazine; the foaming is completed during injection molding or compression molding.

[0026] Preferably, the foaming process is supercritical fluid physical foaming:

[0027] Supercritical fluid impregnation: The composite masterbatch is placed in a high-pressure reactor, and supercritical fluid is introduced. The mixture is kept at a pressure of 10-30 MPa and a temperature of 150-170℃ for 10-30 minutes.

[0028] Rapid depressurization molding: The impregnated masterbatch is transferred to an injection molding machine or mold, and the closed-cell micro-foam structure is formed inside it by rapid depressurization.

[0029] Preferably, the supercritical fluid is supercritical carbon dioxide or supercritical nitrogen.

[0030] Preferably, the foaming process is a chemical-physical composite foaming: 0.2-1 parts by weight of chemical foaming agent is added in the blending and plasticizing step, and supercritical fluid is introduced in the supercritical fluid impregnation step, so that a composite cell structure is formed through the synergistic effect of chemical foaming and physical foaming.

[0031] Preferably, the damping filler is a silicone gel or polyurethane foam material, wherein the silicone gel is a room temperature vulcanizing type with a hardness of 20-30A, and the polyurethane foam has a density of 0.3-0.5 g / cm³. 3 Slow rebound type.

[0032] Compared with the prior art, the advantages of this invention are:

[0033] 1. From a compositional perspective, the technical advantage of this solution lies in the construction of a matrix framework that combines elastic recovery and mechanical support through a specific ratio of butenyl-polydiene-styrene block copolymer, polypropylene, and naphthenic oil. The introduction of quaternary ammonium salt modified nanofillers not only enhances the matrix strength but also provides effective heterogeneous nucleation sites for the subsequent foaming process. The addition of plasticizers precisely controls the processing rheological properties. The synergistic effect of these three types of components lays the material foundation for the formation of a stable micro-foamed structure.

[0034] 2. From a process perspective, this solution adopts a sequence of blending and plasticizing followed by foaming and molding, which avoids the inherent contradiction between material cross-linking and bubble expansion. By separately controlling the temperature and shear parameters in the blending stage and the pressure and depressurization rate in the foaming stage, precise control of cell morphology is achieved. This segmented process design ensures that the material maintains structural integrity and functionality while obtaining lightweight properties. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] General Implementation Examples

[0037] A method for reducing noise and quieting a treadmill involves placing a buffer pad between the running board and the frame. The buffer pad consists of a buffer pad base with an internal axial cavity and shock-absorbing filler injected into the axial cavity of the buffer pad base.

[0038] The cushioning pad substrate is prepared by the following steps, by weight:

[0039] Step 1: Raw material preparation and pretreatment

[0040] Prepare the following ingredients by weight:

[0041] 30-50 parts butenyl-polydiene-styrene block copolymer;

[0042] 15-25 parts polypropylene;

[0043] 30-50 parts naphthenic oil;

[0044] 5-15 parts of quaternary ammonium salt modified nano-calcium carbonate or quaternary ammonium salt modified nano-montmorillonite with a particle size of 20-100nm;

[0045] 3-8 parts epoxidized soybean oil or phthalate plasticizer;

[0046] Foaming agent: Add according to the foaming method;

[0047] Chemical foaming: 0.5-2 parts azodicarbonamide or 4,4'-oxobisbenzenesulfonyl hydrazine;

[0048] Chemical-physical composite foaming: 0.2-1 part azodicarbonamide or 4,4'-oxobisbenzenesulfonyl hydrazine;

[0049] The preparation method of quaternary ammonium salt modified nano-calcium carbonate or quaternary ammonium salt modified nano-montmorillonite is as follows: Dry nano-calcium carbonate or natural nano-montmorillonite is placed in a high-speed mixer and preheated at 80-90℃ for 15-20 minutes to remove surface adsorbed water. Then, a quaternary ammonium salt modifier (hexadecyltrimethylammonium bromide is suitable for nano-calcium carbonate, and dioctadecyldimethylammonium chloride is suitable for nano-montmorillonite) is slowly added at a ratio of 1.5%-3% by mass of the nanofiller. Simultaneously, 0.5%-1% by mass of anhydrous ethanol is added as a dispersion medium to assist in the modification. The agent is spread, and the high-speed mixer is kept at a speed of 800-1200 rpm. The mixture is stirred at a constant temperature of 90-110℃ for 40-60 minutes. During this time, the material temperature is monitored in real time by infrared thermography to avoid local overheating. After the modification is completed, the material is transferred to a vacuum drying oven and vacuum dried at 105-110℃ and -0.08~-0.09MPa for 2-3 hours to remove residual solvent and moisture. Finally, the material is pulverized at high speed and passed through a 200-mesh sieve to obtain quaternary ammonium salt modified nano calcium carbonate or nano montmorillonite with hydrophobic surface and excellent dispersibility.

[0050] Specifically, in the following embodiments, the quaternary ammonium salt modified nano-calcium carbonate is prepared as follows: dried nano-calcium carbonate is placed in a high-speed mixer and preheated at 85°C for 20 min to remove surface adsorbed water. Then, hexadecyltrimethylammonium bromide is slowly added at a mass fraction of 2% of nano-calcium carbonate, and anhydrous ethanol at a mass of 0.8% of nano-calcium carbonate is added as a dispersion medium to assist in spreading. The high-speed mixer is kept at a speed of 1000 rpm and is stirred at 100°C for 50 min. During this period, the material temperature is monitored in real time by infrared thermography to avoid local overheating. After the modification is completed, the material is transferred to a vacuum drying oven and vacuum dried at 108°C and -0.08 MPa for 2.5 h to remove residual solvent. Finally, it is pulverized at high speed and passed through a 200-mesh sieve to obtain quaternary ammonium salt modified nano-calcium carbonate with hydrophobic surface and excellent dispersibility.

[0051] The process for quaternary ammonium salt modified nano-montmorillonite is as follows: Dried nano-montmorillonite calcium is placed in a high-speed mixer and preheated at 85℃ for 20 minutes to remove surface adsorbed water. Then, 2% by mass of nano-montmorillonite is slowly added along with 0.8% by mass of anhydrous ethanol as a dispersion medium and auxiliary modifier. The high-speed mixer is kept at 1000 rpm and stirred at 100℃ for 50 minutes. During this time, the material temperature is monitored in real-time using infrared thermography to prevent localized overheating. After modification, the material is transferred to a vacuum drying oven and vacuum dried at 108℃ and -0.08 MPa for 2.5 hours to remove residual solvent. Finally, it is pulverized at high speed and passed through a 200-mesh sieve to obtain quaternary ammonium salt modified nano-montmorillonite with a hydrophobic surface and excellent dispersibility.

[0052] Step 2: Blending and Plasticizing

[0053] The butenyl-polydiene-styrene block copolymer and polypropylene were pre-dried at 80°C for 4 hours. The butenyl-polydiene-styrene block copolymer, polypropylene, naphthenic oil, nanofiller, and plasticizer were then added sequentially to a mixer according to the formulation ratio. If chemical foaming or chemical-physical composite foaming is used, the corresponding amount of chemical foaming agent is added at this time.

[0054] Internal mixer process parameters: temperature 160-180℃, rotor speed 60-80rpm, mixing time 8-15min. The mixing endpoint is determined by observing the torque change. When the torque stabilizes within the set range, it indicates that the material has reached a homogeneous state, and a premixed blend is obtained.

[0055] The premixed compound was transferred to a co-rotating twin-screw extruder, and the process parameters were set as follows: screw speed 200-400 rpm, barrel temperature zoned control from the feeding section to the die head at 170-190℃, and material residence time 1-3 min. After melt blending, extrusion, water cooling, and pelletizing, a composite masterbatch with uniform particle size was obtained. The water cooling temperature was set to 25±5℃.

[0056] Step 3: Foaming and Molding

[0057] Select the appropriate process route based on the foaming method:

[0058] Chemical foaming route:

[0059] The composite masterbatch is fed into the injection molding machine hopper, and the process parameters are set as follows: barrel temperature is set to 165-180℃, increasing from the rear to the front; mold temperature is set to 140-150℃; injection pressure is set to 80-120MPa; and holding time is set to 30-60 seconds. During injection molding, the foaming agent decomposes under heat, generating gas and forming a closed-cell foam structure inside the material. By controlling the temperature, pressure, and holding time, uniform cell size is ensured, and the pore size is controlled within the range of 50-200μm.

[0060] Supercritical fluid physical foaming route:

[0061] The composite masterbatch is placed in an autoclave, and supercritical carbon dioxide or supercritical nitrogen is introduced. Process parameters are set as follows: pressure 10-30 MPa, temperature 150-170℃, holding time 10-30 min. The saturation concentration of the fluid in the masterbatch is controlled by adjusting the pressure and temperature. The impregnated masterbatch is then rapidly transferred to a preheated mold, and the pressure is rapidly reduced to atmospheric pressure within 1-3 seconds, utilizing the phase change-induced phase separation principle to form a closed-cell micro-foamed structure.

[0062] Chemical-physical composite foaming route:

[0063] After adding 0.2-1 parts of chemical foaming agent during the blending and plasticizing stage, supercritical fluid impregnation is then carried out. The masterbatch is placed in an autoclave and maintained at a pressure of 15-25 MPa and a temperature of 160-170℃ for 15-25 minutes to allow both physical and chemical foaming agents to reach saturation in the matrix simultaneously. Subsequently, it is rapidly transferred to a mold, where the synergistic effect of rapid depressurization and thermal activation forms a bimodal composite cell structure.

[0064] Step 4: Product Post-processing and Assembly

[0065] The foamed cushioning pad substrate is trimmed to remove burrs and gates. Shock-absorbing filler is then injected into the axial cavities within the cushioning pad using an injection molding process. Injection pressure and speed are controlled during filling to avoid damaging the micro-foamed structure. The silicone gel used is a room-temperature vulcanizing type with a hardness of 20-30A, and the polyurethane foam has a density of 0.3-0.5 g / cm³. 3 The slow rebound type is obtained. After filling, it is cured and set at 50-60℃ for 2-4 hours to obtain a low-noise TPS elastomer composite material.

[0066] Example 1

[0067] A method for reducing noise and quieting a treadmill involves placing a buffer pad between the running board and the frame. The buffer pad consists of a buffer pad base with an internal axial cavity and shock-absorbing filler injected into the axial cavity of the buffer pad base.

[0068] The cushioning pad substrate is prepared by the following steps, by weight:

[0069] Step 1: Raw material preparation and pretreatment

[0070] Prepare the following ingredients by weight:

[0071] 40 parts of butenyl-polydiene-styrene block copolymer HYBRAR 7311F;

[0072] 20 parts polypropylene;

[0073] 40 parts naphthenic oil;

[0074] 10 portions of quaternary ammonium salt modified nano-calcium carbonate with a particle size of 50 nm;

[0075] 5.5 parts epoxidized soybean oil;

[0076] 1.25 parts azodicarbonamide.

[0077] Step 2: Blending and Plasticizing

[0078] Butenyl-polydiene-styrene block copolymer and polypropylene were pre-dried at 80°C for 4 hours. Butenyl-polydiene-styrene block copolymer, polypropylene, naphthenic oil, quaternary ammonium salt modified nano-calcium carbonate, epoxidized soybean oil and azodicarbonamide were added sequentially to a mixer according to the formulation ratio.

[0079] Internal mixer process parameters are set as follows: temperature 170℃, rotor speed 70rpm, and mixing time 11.5min. The mixing endpoint is determined by observing the torque change. When the torque stabilizes within the set range, it indicates that the material has reached a homogeneous state, and a premixed blend is obtained.

[0080] The premixed compound was transferred to a co-rotating twin-screw extruder, and the process parameters were set as follows: screw speed 300 rpm, barrel temperature zone control with progressively increasing temperatures from the feeding section to the die head: 170℃, 175℃, 180℃, 185℃, and material residence time 2 min. After melt blending, extrusion, water cooling, and pelletizing, a composite masterbatch with uniform particle size was obtained. The water cooling temperature was set to 25℃.

[0081] Step 3: Foaming and Molding

[0082] The composite masterbatch is fed into the injection molding machine hopper, and the process parameters are set as follows: barrel temperature is set to increase from the rear to the front at 165℃, 170℃, and 175℃; mold temperature is 145℃; injection pressure is 100MPa; and holding time is 45 seconds. During injection molding, the foaming agent decomposes under heat to generate gas, forming a closed-cell foam structure inside the material. By controlling the temperature, pressure, and holding time, uniform cell size is ensured, and the pore size is controlled within the range of 50-200μm.

[0083] Step 4: Product Post-processing and Assembly

[0084] The foamed buffer pad matrix was trimmed to remove flash and gates. Silicone gel was then injected into the axial cavities within the buffer pad. Injection pressure and speed were carefully controlled to avoid damaging the microfoamed structure. A room-temperature curable silicone gel with a hardness of 25A was selected. After filling, the mixture was cured at 55°C for 3 hours to obtain a low-noise TPS elastomer composite material.

[0085] Example 2

[0086] A method for reducing noise and quieting a treadmill involves placing a buffer pad between the running board and the frame. The buffer pad consists of a buffer pad base with an internal axial cavity and shock-absorbing filler injected into the axial cavity of the buffer pad base.

[0087] The cushioning pad substrate is prepared by the following steps, by weight:

[0088] Step 1: Raw material preparation and pretreatment

[0089] Prepare the following ingredients by weight:

[0090] 35 parts of butenyl-polydiene-styrene block copolymer HYBRAR 7311F;

[0091] 25 parts polypropylene;

[0092] 45 parts naphthenic oil;

[0093] 8 portions of quaternary ammonium salt modified nano-montmorillonite;

[0094] 6 parts phthalate plasticizers.

[0095] Step 2: Blending and Plasticizing

[0096] The butenyl-polydiene-styrene block copolymer and polypropylene were pre-dried at 80°C for 4 hours. The butenyl-polydiene-styrene block copolymer, polypropylene, naphthenic oil, quaternary ammonium salt modified nano-montmorillonite, and phthalate plasticizer were added sequentially to a mixer according to the formulation ratio.

[0097] Internal mixer process parameters are set as follows: temperature 165℃, rotor speed 65rpm, mixing time 10min. The mixing endpoint is determined by observing the torque change. When the torque stabilizes within the set range, it indicates that the material has reached a homogeneous state, and a premixed blend is obtained.

[0098] The premixed compound was transferred to a co-rotating twin-screw extruder, and the process parameters were set as follows: screw speed 250 rpm, barrel temperature zone control with increasing temperatures from the feeding section to the die head at 170℃, 175℃, 180℃, and 185℃, and material residence time 1.5 min. After melt blending, extrusion, water cooling, and pelletizing, a composite masterbatch with uniform particle size was obtained, with the water cooling temperature set at 20℃.

[0099] Step 3: Foaming and Molding

[0100] The composite masterbatch was placed in an autoclave, and supercritical carbon dioxide was introduced. Process parameters were set as follows: pressure 20 MPa, temperature 160 °C, and holding time 20 min. The saturation concentration of the fluid in the masterbatch was controlled by adjusting the pressure and temperature. The impregnated masterbatch was then rapidly transferred to a preheated mold, and the pressure was rapidly reduced to atmospheric pressure within 2 seconds, utilizing the phase change-induced phase separation principle to form a closed-cell micro-foamed structure.

[0101] Step 4: Product Post-processing and Assembly

[0102] The foamed cushioning pad matrix is ​​trimmed to remove burrs and gates. Polyurethane foam is then injected into the axial cavities within the cushioning pad. Injection pressure and speed are carefully controlled to avoid damaging the micro-foamed structure. A slow-rebound polyurethane foam with a density of 0.4 g / cm³ is selected. After filling, the mixture is cured at 50°C for 4 hours to obtain a low-noise TPS elastomer composite material.

[0103] Example 3

[0104] A method for reducing noise and quieting a treadmill involves placing a buffer pad between the running board and the frame. The buffer pad consists of a buffer pad base with an internal axial cavity and shock-absorbing filler injected into the axial cavity of the buffer pad base.

[0105] The cushioning pad substrate is prepared by the following steps, by weight:

[0106] Step 1: Raw material preparation and pretreatment

[0107] Prepare the following ingredients by weight:

[0108] 45 parts of butenyl-polydiene-styrene block copolymer HYBRAR 7311F;

[0109] 18 parts polypropylene;

[0110] 35 parts naphthenic oil;

[0111] 12 portions of quaternary ammonium salt modified nano-calcium carbonate;

[0112] 4 parts epoxidized soybean oil;

[0113] 0.6 parts of 4,4'-oxobis(benzenesulfonylhydrazine).

[0114] Step 2: Blending and Plasticizing

[0115] Butenyl-polydiene-styrene block copolymer and polypropylene were pre-dried at 80°C for 4 hours. Butenyl-polydiene-styrene block copolymer, polypropylene, naphthenic oil, quaternary ammonium salt modified nano-calcium carbonate, epoxidized soybean oil and 4,4'-oxobisbenzenesulfonyl hydrazine were added sequentially to a mixer according to the formulation ratio.

[0116] Internal mixer process parameters are set as follows: temperature 175℃, rotor speed 75rpm, mixing time 13min. The mixing endpoint is determined by observing the torque change. When the torque stabilizes within the set range, it indicates that the material has reached a homogeneous state, and a premixed blend is obtained.

[0117] The premixed compound was transferred to a co-rotating twin-screw extruder, and the process parameters were set as follows: screw speed 350 rpm, barrel temperature zone control with increasing temperatures from the feeding section to the die head at 175℃, 180℃, 185℃, and 190℃, and material residence time 2.5 min. After melt blending, extrusion, water cooling, and pelletizing, a composite masterbatch with uniform particle size was obtained, with the water cooling temperature set at 30℃.

[0118] Step 3: Foaming and Molding

[0119] The masterbatch is placed in an autoclave and maintained at 20 MPa and 165°C for 20 minutes to allow both physical and chemical foaming agents to reach saturation in the matrix. Supercritical nitrogen is then introduced, followed by rapid transfer to a mold. Through the synergistic effect of rapid depressurization and thermal activation, a bimodal composite cell structure is formed.

[0120] Step 4: Product Post-processing and Assembly

[0121] The foamed buffer pad substrate is trimmed to remove burrs and gates. Silicone gel is then injected into the axial cavities within the buffer pad. Injection pressure and speed are carefully controlled during filling to avoid damaging the microfoamed structure. A room-temperature curable silicone gel with a hardness of 30A is selected. After filling, the mixture is cured at 60°C for 2 hours.

[0122] Comparative Example 1

[0123] The difference from Example 1 is that the substrate ratio is unbalanced. The substrate ratio is 60 parts of butenyl-polydiene-styrene block copolymer, 10 parts of polypropylene, 30 parts of naphthenic oil, 10 parts of nano calcium carbonate, and 5.5 parts of epoxidized soybean oil.

[0124] Comparative Example 2

[0125] The difference from Example 1 is that the nano-calcium carbonate is replaced with an equal amount of nano-calcium carbonate modified with a silane coupling agent. The specific process is as follows: The dried nano-calcium carbonate is placed in a high-speed mixer and preheated at 85°C for 20 minutes to completely remove surface adsorbed water. Then, KH550 is diluted with anhydrous ethanol at a volume ratio of 1:3 (2% by mass of nano-calcium carbonate) and slowly added dropwise to the nano-calcium carbonate in the high-speed mixer. The mixer is maintained at 1000 rpm and 85°C for 15 minutes to ensure the silane coupling agent is fully hydrolyzed and uniformly adsorbed onto the filler surface. Next, the temperature is raised to 100°C and maintained at the same speed for 35 minutes to promote the chemical bonding reaction between the silane coupling agent and the hydroxyl groups on the surface of the nano-calcium carbonate. During this process, infrared thermography is used to monitor the temperature and prevent localized overheating. After modification, the material is transferred to a vacuum drying oven and vacuum dried at 110°C and -0.08 MPa for 2.5 hours to remove residual ethanol and reaction byproducts. Finally, the material is pulverized at high speed for 200... The nano-calcium carbonate modified with silane coupling agent was obtained by sieving.

[0126] Comparative Example 3

[0127] The difference from Example 1 is that the mixing temperature is 130°C and the twin-screw temperature is 150°C.

[0128] Comparative Example 4

[0129] The difference from Example 1 is that the pressure is set to 5 MPa during physical foaming.

[0130] Comparative Example 5

[0131] The difference from Example 1 is that the silicone gel used is of type 18A hardness.

[0132] Comparative Example 6

[0133] The difference from Example 1 is that no material is filled into the cavity.

[0134] Comparative Example 7

[0135] The difference from Example 1 is that it was not subjected to intensive mixing:

[0136] Blending and plasticizing: After mixing and stirring, the components are directly fed into a twin-screw extruder, where they are melt-blended and plasticized under screw shearing and a temperature of 170-190℃. After extrusion, cooling, and granulation, the composite masterbatch is obtained.

[0137] Performance testing:

[0138] Storage modulus: Reflects the elasticity of the material, and is tested according to the method specified in GB / T 45159.4-2025 "Characteristics of dynamic mechanical properties of viscoelastic materials subjected to mechanical vibration and impact".

[0139] Loss modulus: reflects the viscosity of the material, i.e., damping, and is tested according to the method specified in GB / T45159 "Characterization of dynamic mechanical properties of viscoelastic materials subjected to mechanical vibration and shock".

[0140] Tensile properties: The test was conducted in accordance with the method specified in GB / T1040.2-2006 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics".

[0141] Fatigue performance: The test was conducted in accordance with the method specified in GB / T35465.1-2017 "Test methods for fatigue performance of polymer-based composite materials - Part 1: General rules".

[0142] Vibration reduction and noise reduction effects: An accelerometer was installed on the floor below the treadmill, located at the top of the ceiling, close to the treadmill. A microphone was placed near the accelerometer, pointing towards the ceiling. A decibel meter was placed at a lower position in the room. Simultaneously, the vibration of the ceiling and the noise in the room above were measured when a treadmill was in use. The accelerometer and microphone were connected to a data acquisition card to synchronously collect their acceleration and sound pressure level data signals and record the raw data. Subsequent processing was then performed to obtain the peak value of the main vibration of the floor slab and the peak value of the main frequency of noise in the lower room.

[0143] The test results are shown in Table 1.

[0144] Table 1. Performance test results of the examples and comparative examples:

[0145]

[0146] The performance advantages presented in the embodiments of this invention stem from the fact that the TPS substrate constructed by the specific ratio of butenyl-polydiene-styrene block copolymer, polypropylene and naphthenic oil forms a basic framework that combines elastic recovery and mechanical support. The quaternary ammonium salt modified nanofiller not only improves compatibility with the substrate and avoids agglomeration, but also serves as a heterogeneous nucleation site to ensure the formation of a uniform closed-cell micro-foamed structure. Furthermore, it enhances the mechanical properties and fatigue resistance of the material by strengthening the interfacial bonding. The plasticizer regulates the processing rheological properties and helps to stabilize the foaming process. As a result, the material exhibits excellent performance in terms of elasticity, damping, mechanical strength and fatigue life, and can effectively reduce vibration transmission and noise generation.

[0147] Compared to the examples, Comparative Example 1 suffered from an imbalance in the substrate ratio, with an excess of butenyl-polydiene-styrene block copolymer and an insufficient amount of polypropylene, disrupting the balance between elasticity and rigidity, resulting in insufficient material support and decreased mechanical properties and damping effect. Comparative Example 2 used silane coupling agent to modify the nanofiller, but its hydrophobic modification effect and processing flowability control ability were weaker than quaternary ammonium salts. The uniformity of filler dispersion and interfacial bonding strength were not as good as in the examples, thus affecting the foaming structure and overall performance. In Comparative Example 3, due to insufficient processing temperature, the components were not fully plasticized and mixed, resulting in uneven dispersion of the nanofiller and defects in the matrix structure, leading to a significant reduction in the material's mechanical properties, damping, and fatigue resistance. Comparative Example 4 involved physical foaming. Insufficient pressure resulted in an inadequate saturation concentration of supercritical fluid in the masterbatch, failing to form a uniform and dense closed-cell micro-foam structure, thus impairing vibration damping, noise reduction, and mechanical properties. Comparative Example 5 used silica gel with insufficient hardness as a damping filler, which could not provide effective viscous damping and structural support, leading to a decrease in the overall damping effect and mechanical properties of the material. Comparative Example 6 did not fill with damping filler, missing the key viscous damping link, failing to achieve multi-synergistic damping, and the transmission of vibration and noise was not effectively suppressed. Comparative Example 7 omitted the mixing step, resulting in poor mixing uniformity of the components, uneven dispersion of nanofillers, and stress concentration points inside the matrix, which negatively impacted the material's mechanical properties, damping, and fatigue resistance.

Claims

1. A method for reducing noise and quieting a treadmill, characterized in that, A buffer pad is installed between the running board and the frame. The buffer pad consists of a buffer pad matrix with an internal axial cavity and shock-absorbing filler injected into the axial cavity of the buffer pad matrix. The buffer pad matrix is ​​made of low-noise TPS elastomer composite material. The low-noise TPS elastomer composite material comprises the following parts by weight: 30-50 parts of HYBRAR 7311F, a hydrogenated styrene-isoprene-butadiene block copolymer; 15-25 parts of polypropylene; 30-50 parts of naphthenic oil; 5-15 parts of nanofiller; and 3-8 parts of plasticizer. The low-noise TPS elastomer composite material has a uniform closed-cell micro-foamed structure with a pore size of 50-200μm. The nanofiller is a quaternary ammonium salt modified nanofiller with a particle size of 20-100 nm. The preparation method of the quaternary ammonium salt modified nanofiller is as follows: quaternary ammonium salt modifier is slowly added at a ratio of 1.5%-3% by mass of nanofiller, and anhydrous ethanol at 0.5%-1% by mass of filler is added as a dispersion medium to assist the spreading of the modifier. The high-speed mixer is kept at a speed of 800-1200 rpm and the mixture is stirred at a constant temperature of 90-110℃ for 40-60 min. After modification, the material is transferred to a vacuum drying oven and vacuum dried at 105-110℃ and -0.08~-0.09 MPa for 2-3 h to remove residual solvent and moisture. Finally, the material is pulverized at high speed and passed through a 200-mesh sieve to obtain the quaternary ammonium salt modified nanofiller. The preparation method of the low-noise TPS elastomer composite material includes the following steps: Raw material preparation and pretreatment: Prepare HYBRAR 7311F (hydrogenated styrene-isoprene-butadiene block copolymer), polypropylene, naphthenic oil, nanofiller and plasticizer according to the formula weight parts, and dry HYBRAR 7311F (hydrogenated styrene-isoprene-butadiene block copolymer) and polypropylene. Blending and plasticizing: The pretreated styrene-isoprene-butadiene block copolymer hydride HYBRAR7311F, polypropylene, naphthenic oil, nanofillers, and plasticizer are blended in an internal mixer at 160-180℃ for 8-15 min to obtain a premixed blend; then the premixed blend is transferred to a twin-screw extruder and melt-blended and plasticized at a screw speed of 200-400 rpm and a temperature of 170-190℃; after extrusion, water cooling, and pelletizing, a composite masterbatch is obtained. Foaming molding: The composite masterbatch is foamed by adding a chemical foaming agent and thermally activating and decomposing it, or by impregnating it with supercritical fluid and then rapidly depressurizing it, or by a combination of chemical and physical composite foaming, so that a uniform closed-cell micro-foamed structure with a pore size of 50-200μm is formed inside it. Product post-processing and assembly: The foamed buffer pad matrix is ​​trimmed, and then the buffer pad is filled with shock-absorbing filler. After filling, it is cured and shaped at 50-60℃ for 2-4 hours to obtain a low-noise TPS elastomer composite material. The damping filler is made of silicone gel or polyurethane foam. The silicone gel is selected as a room temperature vulcanizing type with a hardness of 20-30A, and the polyurethane foam has a density of 0.3-0.5 g / cm³. 3 Slow rebound type.

2. The treadmill noise reduction and silencing method as described in claim 1, characterized in that, The plasticizer is epoxidized soybean oil or phthalate plasticizer.

3. The treadmill noise reduction and silencing method as described in claim 1, characterized in that, The blending and plasticizing process is carried out in a twin-screw extruder with a screw speed of 200-400 rpm and a material residence time of 1-3 min.

4. The treadmill noise reduction and quieting method as described in claim 1, characterized in that, The foaming process is chemical foaming, specifically including: adding 0.5-2 parts by weight of a chemical foaming agent in the blending and plasticizing step, wherein the chemical foaming agent is azodicarbonamide or 4,4'-oxobisbenzenesulfonylhydrazine; and then completing the foaming process by heating to decompose the foaming agent during injection molding or compression molding.

5. The treadmill noise reduction and quieting method as described in claim 1, characterized in that, The foaming process is a supercritical fluid physical foaming method, specifically including: Supercritical fluid impregnation: The composite masterbatch is placed in a high-pressure autoclave, and supercritical carbon dioxide or supercritical nitrogen is introduced. The mixture is kept at a pressure of 10-30 MPa and a temperature of 150-170℃ for 10-30 minutes. Rapid depressurization molding: The impregnated masterbatch is transferred to a molding die, and the closed-cell micro-foam structure is formed inside it by rapid depressurization.

6. The treadmill noise reduction and quieting method as described in claim 1, characterized in that, The foaming molding step is a chemical-physical composite foaming: 0.2-1 parts by weight of chemical foaming agent is added in the blending and plasticizing step, and the composite masterbatch is impregnated with supercritical fluid. Then, foaming is completed through the synergistic effect of rapid depressurization and thermal activation.

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