Shock-absorbing damping rubber EVA foaming material and preparation method thereof

Abstract

This invention relates to the field of EVA foaming material technology, specifically to a shock-absorbing and damping rubber EVA foaming material and its preparation method, comprising the following raw materials in parts by weight: 100 parts ethylene-vinyl acetate resin, 10-15 parts SiO2 aerogel-modified lignin damping material, and 2-4 parts foaming agent AC; wherein, the preparation process of the damping material includes the following steps: preparing silane coupling agent-modified silica aerogel; adding lignin to ethanol and stirring for 30 min, then adding silane coupling agent-modified silica aerogel, reacting at 65℃ for 12 h, to obtain SiO2 aerogel-modified lignin damping material; this invention bridges silica aerogel and lignin with silane coupling agent to construct a "core-shell" structured damping unit: core layer: silica aerogel provides a nanoporous interface, increasing frictional energy dissipation; shell layer: lignin is chemically bonded to aerogel through silane bonds to form a deformable dissipative phase.

Description

Technical Field

[0001] This invention relates to the field of EVA foam material technology, specifically to a shock-absorbing and damping rubber EVA foam material and its preparation method. Background Technology

[0002] Ethylene-vinyl acetate copolymer (EVA) foam materials are widely used in footwear, sports equipment packaging, and building vibration damping due to their lightweight, flexibility, and excellent processing properties. However, traditional EVA foam materials have the following inherent drawbacks:

[0003] Insufficient damping performance: The EVA molecular chain segments have a low energy barrier for motion, resulting in limited energy dissipation under dynamic loads. This leads to unsatisfactory shock absorption and noise reduction effects, making it difficult to meet the impact absorption requirements of high-precision equipment protection or sports equipment.

[0004] The contradiction between mechanical strength and lightweight: In order to improve damping performance, inorganic fillers (such as calcium carbonate, talc) or rubber phases are often added for modification. However, such methods significantly increase the material density and are prone to cause the collapse of the cell structure, resulting in decreased resilience and shortened fatigue life.

[0005] Filler dispersibility and interfacial compatibility issues:

[0006] Nanofillers (such as silica and carbon black) are prone to agglomeration, which becomes stress concentration points during the foaming process, inducing the merging and rupture of foam cells;

[0007] Although biomass fillers (such as lignin) have damping potential, their surface hydrophobicity and poor compatibility with the EVA matrix require treatment with high doses of coupling agents, which in turn inhibits foaming efficiency. Summary of the Invention

[0008] The purpose of this invention is to provide a shock-absorbing and damping rubber EVA foam material and its preparation method. A "core-shell" structure damping unit is constructed by bridging silica aerogel and lignin using a silane coupling agent: Core layer: Silica aerogel provides a nanoporous interface, increasing frictional energy dissipation; Shell layer: Lignin is chemically bonded to the aerogel via silane bonds, forming a deformable dissipative phase; Synergistic effect: The nanopores of the aerogel anchor the lignin molecular chains, inhibiting aggregation; The polar groups of lignin and the ester groups of EVA form a hydrogen bond network, enhancing the interfacial stress transfer efficiency.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] A shock-absorbing and damping rubber EVA foam material comprises the following raw materials in parts by weight:

[0011] 100 parts ethylene-vinyl acetate resin, 10-15 parts SiO2 aerogel modified lignin damping material, 2-4 parts foaming agent AC.

[0012] The preparation process of SiO2 aerogel-modified lignin damping material includes the following steps:

[0013] S1: Preparation of silane coupling agent modified silica aerogel;

[0014] S2: Add lignin to ethanol and stir for 30 min, then add silane coupling agent to modify silica aerogel, and react at 65℃ for 12 h to obtain a SiO2 aerogel modified lignin damping material.

[0015] As a further aspect of the present invention: the preparation process of silane coupling agent modified silica aerogel is as follows:

[0016] Silica aerogel was placed in dichloromethane to form a suspension, and then silane coupling agent KH560 was added to the suspension. The mixture was stirred for 6 hours to obtain silane coupling agent modified silica aerogel.

[0017] As a further aspect of the present invention, the mass ratio of silica aerogel, silane coupling agent KH560 and dichloromethane is 5.0:2.5-3.0:230-270.

[0018] As a further aspect of the present invention, the particle size D50 of the modified silica aerogel is controlled at 1-2 micrometers.

[0019] As a further embodiment of the present invention: the mass ratio of lignin, silane coupling agent modified silica aerogel and ethanol is 70:50:800-1000.

[0020] As a further aspect of the present invention, the preparation process of silica aerogel is as follows:

[0021] Methyltrimethoxysilane and methanol were mixed and stirred, and then oxalic acid solution was added dropwise. The mixture was stirred thoroughly at 30°C for 2 hours. Then N,N-dimethylformamide was added dropwise, and then ammonia solution was added dropwise to adjust the pH to 8. The mixture was stirred for 10 minutes and reacted at 40°C for 9 hours to obtain a gel.

[0022] The gel was aged at 50°C for 24 hours, and then isopropanol and n-hexane were added for solvent replacement, each time for 1-2 hours. Finally, it was washed twice with n-hexane. The gel was dried at 60°C for 12 hours to obtain silica aerogel.

[0023] As a further aspect of the present invention, the molar ratio of methyltrimethoxysilane, oxalic acid and methanol is 1:0.00016:22-26.

[0024] As a further embodiment of the present invention: the volume ratio of methyltrimethoxysilane to N,N-dimethylformamide is 100:50.

[0025] A method for preparing shock-absorbing and damping EVA foam material, the method comprising:

[0026] After the ethylene-vinyl acetate resin, the SiO2 aerogel-modified lignin damping material and the foaming agent AC are mixed evenly according to the above weight ratio, the mixture is placed in an extruder for kneading and the material is pressed into thin sheets.

[0027] Thin sheets are placed in a flat vulcanizing machine to obtain shock-absorbing and damping modified EVA material.

[0028] As a further aspect of the present invention: the parameters of the flat vulcanizing machine are 10MPa and 170℃ for molding foaming for 6 minutes.

[0029] The beneficial effects of this invention are:

[0030] This invention modifies silica aerogel with a silane coupling agent and then reacts it with lignin to obtain a SiO2 aerogel-modified lignin damping material. The damping mechanism of lignin mainly relies on its inherent elasticity and shock-resistant properties. Lignin has a high natural frequency and damping ratio, which can rapidly dissipate external impact forces, thereby reducing the transmission and impact of vibrations. Furthermore, lignin has energy absorption capabilities, converting energy into internal deformation and heat energy, thus mitigating the impact of vibrations. Therefore, applying lignin as a bio-based damping agent to EVA foam materials provides environmentally friendly damping effects. Additionally, the aromatic rings and double bonds in the lignin molecular structure can absorb ultraviolet light, thus slowing down its damage and decomposition to molecules. Simultaneously, the aromatic groups in lignin can also counteract the free radical generation caused by ultraviolet light through free radical neutralization reactions, effectively improving the anti-aging and anti-ultraviolet properties of EVA foam materials and mitigating the aging tendency of EVA foam when exposed to ultraviolet light (sunlight) and oxygen environments for extended periods. This causes the surface to turn yellow and its shock-absorbing and damping performance to decrease significantly.

[0031] Due to its unique structure and looseness, SiO2 aerogel has excellent shock absorption properties. Under movement or vibration, the aerogel can quickly absorb the impact force brought by the vibration and disperse it into the interior of the material, thereby reducing the transmission of vibration. Thus, SiO2 aerogel and lignin work synergistically to have a good anti-vibration effect.

[0032] In this invention, the introduction of methyl groups in the SiO2 aerogel reduces the density of the interconnected gel network. The steric hindrance between adjacent methyl groups generates a repulsive force, which makes the aerogel exhibit better elasticity and further improves the shock absorption and damping performance of EVA foam material.

[0033] Furthermore, in the SiO2 aerogel of the present invention, the methyl group is a nonpolar group. The introduction of methyl groups can improve the hydrophobicity of the aerogel, so that the SiO2 aerogel has good hydrophobic properties. Therefore, the introduction of SiO2 aerogel in the present invention will effectively improve the hydrophobicity of lignin and solve the problems of decreased wet damping performance and poor dimensional stability of lignin.

[0034] Therefore, the SiO2 aerogel-modified lignin of this invention, as a damping material, significantly improves energy dissipation efficiency through the synergistic effect of the porous aerogel structure and lignin molecular chains. The nanopores of the aerogel can effectively absorb shock stress waves, and the viscoelasticity of the lignin molecular chains provides multiple energy conversion mechanisms, enabling the composite material to have excellent vibration damping and noise reduction capabilities in a wide frequency range (especially high-frequency vibrations).

[0035] The low density of SiO2 aerogel significantly reduces the overall weight of the material. Simultaneously, its three-dimensional network framework, combined with the rigid structure of lignin, forms a reinforcing phase, effectively improving the compressive strength and resilience of the foamed material and overcoming the shortcomings of traditional lightweight materials in terms of mechanical properties. The nanoporous structure of SiO2 aerogel inhibits air convection, giving the material excellent thermal insulation properties and ensuring stable damping performance in environments ranging from -40℃ to 80℃, making it suitable for applications with large temperature variations, such as automotive and construction. Detailed Implementation

[0036] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with 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 skilled in the art without creative effort should fall within the scope of protection of the present invention. Example 1

[0037] The present invention provides a shock-absorbing and damping rubber EVA foam material, comprising the following parts by weight of raw materials:

[0038] 100 parts ethylene-vinyl acetate resin, 10 parts SiO2 aerogel modified lignin damping material, 2 parts foaming agent AC;

[0039] The preparation process of SiO2 aerogel-modified lignin damping material includes the following steps:

[0040] S1: Preparation of silane coupling agent modified silica aerogel;

[0041] Specifically, silica aerogel is placed in dichloromethane to form a suspension, and then silane coupling agent KH560 is added to the suspension. The mixture is stirred and reacted for 6 hours. The solvent is then dried under vacuum and dispersed by grinding to obtain silane coupling agent modified silica aerogel.

[0042] The mass ratio of silica aerogel, silane coupling agent KH560, and dichloromethane is 5.0:2.5:230.

[0043] The particle size D50 of the modified silica aerogel was controlled within 1 micrometer;

[0044] S2: Add lignin to ethanol and stir for 30 min, then add silane coupling agent to modify silica aerogel, and react at 65℃ for 12 h to obtain a damping material of SiO2 aerogel modified lignin.

[0045] The mass ratio of lignin, silane coupling agent modified silica aerogel and ethanol is 70:50:800.

[0046] More specifically, the preparation process of silica aerogel is as follows:

[0047] Methyltrimethoxysilane (MTMS) and methanol were mixed and stirred, and then oxalic acid solution (0.01 mol / L) was added dropwise. The mixture was stirred thoroughly at 30 °C for 2 h. Then N,N-dimethylformamide was added dropwise, and then ammonia solution was added dropwise to adjust the pH to 8. The mixture was stirred for 10 min and reacted at 40 °C for 9 h to obtain a gel.

[0048] The gel was aged at 50°C for 24 hours, and then isopropanol and n-hexane were added for solvent replacement, each time for 1-2 hours. Finally, it was washed twice with n-hexane. It was dried at 60°C for 12 hours to obtain silica aerogel.

[0049] The molar ratio of methyltrimethoxysilane, oxalic acid and methanol is 1:0.00016:22.

[0050] The volume ratio of methyltrimethoxysilane to N,N-dimethylformamide is 100:50.

[0051] This invention also provides a method for preparing a shock-absorbing and damping rubber EVA foam material, comprising the following steps:

[0052] Step 1: Mix ethylene-vinyl acetate resin, SiO2 aerogel modified lignin damping material and foaming agent AC evenly according to the above weight ratio, and place them in a preheated extruder. Extrusion and mixing are carried out under the conditions of 105℃ in each zone and 20rpm. After quickly transferring to an open mill for mixing for 10 minutes, the material is pressed into thin sheets.

[0053] The thin sheet was placed in the preheated mold cavity of the flat vulcanizing machine and molded and foamed at 10MPa and 170℃ for 6 minutes to obtain the shock-absorbing and damping modified EVA material. Example 2

[0054] The present invention provides a shock-absorbing and damping rubber EVA foam material, comprising the following parts by weight of raw materials:

[0055] 100 parts ethylene-vinyl acetate resin, 12 parts SiO2 aerogel modified lignin damping material, 3 parts foaming agent AC;

[0056] The preparation process of SiO2 aerogel-modified lignin damping material includes the following steps:

[0057] S1: Preparation of silane coupling agent modified silica aerogel;

[0058] Specifically, silica aerogel is placed in dichloromethane to form a suspension, and then silane coupling agent KH560 is added to the suspension. The mixture is stirred and reacted for 6 hours. The solvent is then dried under vacuum and dispersed by grinding to obtain silane coupling agent modified silica aerogel.

[0059] The mass ratio of silica aerogel, silane coupling agent KH560, and dichloromethane is 5.0:2.8:250.

[0060] The particle size D50 of the modified silica aerogel was controlled to be 1 micrometer;

[0061] S2: Add lignin to ethanol and stir for 30 min, then add silane coupling agent to modify silica aerogel, and react at 65℃ for 12 h to obtain a damping material of SiO2 aerogel modified lignin.

[0062] The mass ratio of lignin, silane coupling agent modified silica aerogel and ethanol is 70:50:9000.

[0063] More specifically, the preparation process of silica aerogel is as follows:

[0064] Methyltrimethoxysilane (MTMS) and methanol were mixed and stirred, and then oxalic acid solution (0.01 mol / L) was added dropwise. The mixture was stirred thoroughly at 30 °C for 2 h. Then N,N-dimethylformamide was added dropwise, and then ammonia solution was added dropwise to adjust the pH to 8. The mixture was stirred for 10 min and reacted at 40 °C for 9 h to obtain a gel.

[0065] The gel was aged at 50°C for 24 hours, and then isopropanol and n-hexane were added for solvent replacement, each time for 1-2 hours. Finally, it was washed twice with n-hexane. It was dried at 60°C for 12 hours to obtain silica aerogel.

[0066] The molar ratio of methyltrimethoxysilane, oxalic acid and methanol is 1:0.00016:24.

[0067] The volume ratio of methyltrimethoxysilane to N,N-dimethylformamide is 100:50.

[0068] This invention also provides a method for preparing a shock-absorbing and damping rubber EVA foam material, comprising the following steps:

[0069] Step 1: Mix ethylene-vinyl acetate resin, SiO2 aerogel modified lignin damping material and foaming agent AC evenly according to the above weight ratio, and place them in a preheated extruder. Extrusion and mixing are carried out under the conditions of 110℃ in each zone and 20rpm. After quickly transferring to an open mill for mixing for 15min, the material is pressed into thin sheets.

[0070] The thin sheet was placed in the preheated mold cavity of the flat vulcanizing machine and molded and foamed at 10MPa and 170℃ for 6 minutes to obtain the shock-absorbing and damping modified EVA material. Example 3

[0071] The present invention provides a shock-absorbing and damping rubber EVA foam material, comprising the following parts by weight of raw materials:

[0072] 100 parts ethylene-vinyl acetate resin, 15 parts SiO2 aerogel modified lignin damping material, 4 parts foaming agent AC;

[0073] The preparation process of SiO2 aerogel-modified lignin damping material includes the following steps:

[0074] S1: Preparation of silane coupling agent modified silica aerogel;

[0075] Specifically, silica aerogel is placed in dichloromethane to form a suspension, and then silane coupling agent KH560 is added to the suspension. The mixture is stirred and reacted for 6 hours. The solvent is then dried under vacuum and dispersed by grinding to obtain silane coupling agent modified silica aerogel.

[0076] The mass ratio of silica aerogel, silane coupling agent KH560, and dichloromethane is 5.0:3.0:270.

[0077] The particle size D50 of the modified silica aerogel was controlled to be 2 micrometers;

[0078] S2: Add lignin to ethanol and stir for 30 min, then add silane coupling agent to modify silica aerogel, and react at 65℃ for 12 h to obtain a damping material of SiO2 aerogel modified lignin.

[0079] The mass ratio of lignin, silane coupling agent modified silica aerogel and ethanol is 70:50:1000.

[0080] More specifically, the preparation process of silica aerogel is as follows:

[0081] Methyltrimethoxysilane (MTMS) and methanol were mixed and stirred, and then oxalic acid solution (0.01 mol / L) was added dropwise. The mixture was stirred thoroughly at 30 °C for 2 h. Then N,N-dimethylformamide was added dropwise, and then ammonia solution was added dropwise to adjust the pH to 8. The mixture was stirred for 10 min and reacted at 40 °C for 9 h to obtain a gel.

[0082] The gel was aged at 50°C for 24 hours, and then isopropanol and n-hexane were added for solvent replacement, each time for 1-2 hours. Finally, it was washed twice with n-hexane. It was dried at 60°C for 12 hours to obtain silica aerogel.

[0083] The molar ratio of methyltrimethoxysilane, oxalic acid and methanol is 1:0.00016:26.

[0084] The volume ratio of methyltrimethoxysilane to N,N-dimethylformamide is 100:50.

[0085] This invention also provides a method for preparing a shock-absorbing and damping rubber EVA foam material, comprising the following steps:

[0086] After mixing ethylene-vinyl acetate resin, SiO2 aerogel-modified lignin damping material and foaming agent AC evenly according to the above weight ratio, the mixture is placed in a preheated extruder and extruded and mixed under the conditions of 115℃ in each zone and 20rpm. The mixture is then quickly transferred to an open mill and mixed for 20min before being pressed into thin sheets.

[0087] The thin sheet was placed in the preheated mold cavity of the flat vulcanizing machine and molded and foamed at 10MPa and 170℃ for 6 minutes to obtain the shock-absorbing and damping modified EVA material.

[0088] Comparative Example 1

[0089] The difference between Comparative Example 1 and Example 1 is that: no SiO2 aerogel was added to modify the lignin damping material, and shock-absorbing and damping modified EVA material was prepared.

[0090] Performance testing:

[0091] The damping performance of the shock-absorbing and damping modified EVA materials of Examples 1-3 and Comparative Example 1 was tested, and the test data are shown in the table below:

[0092] Test method: Dynamic thermomechanical analysis (DMA)

[0093] Test parameters:

[0094] Temperature range: -40℃ to 80℃;

[0095] Frequency: 1 Hz;

[0096] Strain: 0.1%;

[0097] Test index: Loss factor (tanδ): Characterizes the material's shock absorption capacity (the higher the peak value, the better the damping performance).

[0098] tanδ peak value Example 1 0.35 Example 2 0.33 Example 3 0.34 Comparative Example 1 0.22

[0099] As can be seen from the table above, the present invention adds SiO2 aerogel-modified lignin damping material to EVA foam material, which will effectively improve the shock absorption and damping performance of EVA foam material.

[0100] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A shock-absorbing and damping EVA foam material, characterized in that, Including the following parts by weight of raw materials: 100 parts ethylene-vinyl acetate resin, 10-15 parts SiO2 aerogel modified lignin damping material, 2-4 parts foaming agent AC. The preparation process of SiO2 aerogel-modified lignin damping material includes the following steps: S1: Preparation of silane coupling agent modified silica aerogel; S2: Add lignin to ethanol and stir for 30 min, then add silane coupling agent to modify silica aerogel, and react at 65℃ for 12 h to obtain a damping material of SiO2 aerogel modified lignin. The mass ratio of lignin, silane coupling agent modified silica aerogel and ethanol is 70:50:800-1000.

2. The shock-absorbing and damping rubber EVA foam material according to claim 1, characterized in that, The preparation process of silane coupling agent modified silica aerogel is as follows: Silica aerogel was placed in dichloromethane to form a suspension, and then silane coupling agent KH560 was added to the suspension. The mixture was stirred for 6 hours to obtain silane coupling agent modified silica aerogel.

3. The shock-absorbing and damping rubber EVA foam material according to claim 1, characterized in that, The mass ratio of silica aerogel, silane coupling agent KH560, and dichloromethane is 5.0:2.5-3.0:230-270.

4. The shock-absorbing and damping rubber EVA foam material according to claim 1, characterized in that, The particle size D50 of the modified silica aerogel was controlled at 1-2 micrometers.

5. The shock-absorbing and damping rubber EVA foam material according to claim 1, characterized in that, The preparation process of silica aerogel is as follows: Methyltrimethoxysilane and methanol were mixed and stirred, and then oxalic acid solution was added dropwise. The mixture was stirred thoroughly at 30°C for 2 hours. Then N,N-dimethylformamide was added dropwise, and then ammonia solution was added dropwise to adjust the pH to 8. The mixture was stirred for 10 minutes and reacted at 40°C for 9 hours to obtain a gel. The gel was aged at 50°C for 24 hours, and then isopropanol and n-hexane were added for solvent replacement, each time for 1-2 hours. Finally, it was washed twice with n-hexane. The gel was dried at 60°C for 12 hours to obtain silica aerogel.

6. The shock-absorbing and damping rubber EVA foam material according to claim 5, characterized in that, The molar ratio of methyltrimethoxysilane, oxalic acid and methanol is 1:0.00016:22-26.

7. The shock-absorbing and damping rubber EVA foam material according to claim 6, characterized in that, The volume ratio of methyltrimethoxysilane to N,N-dimethylformamide is 100:

50.

8. A method for preparing a shock-absorbing and damping rubber EVA foam material, characterized in that, This method is used to prepare the EVA foam material according to any one of claims 1-7, and the method includes: After the ethylene-vinyl acetate resin, the SiO2 aerogel-modified lignin damping material and the foaming agent AC are mixed evenly according to the above weight ratio, the mixture is placed in an extruder for kneading and the material is pressed into thin sheets. Thin sheets are placed in a flat vulcanizing machine to obtain shock-absorbing and damping modified EVA material.

9. The shock-absorbing and damping rubber EVA foam material according to claim 8, characterized in that, The parameters of the flat vulcanizing machine are 10MPa and 170℃ for 6 minutes of molding foaming.