Gradient directional porous wave-absorbing / sound-insulating rubber, preparation method and application thereof

Abstract

The application discloses a gradient directional porous wave-absorbing / sound-insulating rubber and a preparation method and application thereof, and belongs to the technical field of rubber. The rubber is prepared from ethylene-propylene-diene rubber, gradient directional porous fillers, zinc oxide, stearic acid, sulfur, an accelerator and an additive. The gradient directional porous fillers are prepared from modified biomass porous carbon and single-crystal ordered bimetallic porous MOF. The modified biomass porous carbon is prepared from biomass through calcination and acidification. The single-crystal ordered bimetallic porous MOF is prepared by the following steps: adding a PS template into a mixed solution of dimethyl imidazole, a cobalt salt, a nickel salt and an organic solvent, vacuum degassing, standing and drying; and then adding a mixed solution of ammonia and an organic solvent, vacuum degassing and drying. The application has the advantages of excellent wave-absorbing / sound-insulating performance.

Description

Technical Field

[0001] This invention belongs to the field of rubber technology, and relates to a type of rubber, particularly a gradient-oriented porous sound-absorbing / sound-insulating rubber, its preparation method, and its application. Background Technology

[0002] With the development of 5G communication, stealth technology, and the integration of electronic devices, flexible polymer materials are facing dual requirements: high mechanical strength and efficient electromagnetic wave absorption. Faced with complex electromagnetic interference and increasingly sophisticated detection methods, the threats to airborne command and control are becoming increasingly significant, making the development of tunable material designs for different scenarios particularly important. Current research on microwave absorbing composite materials largely focuses on the absorber itself, and the materials' functions are relatively singular; for example, mechanical and functional studies are separated, and research on dynamically tunable multifunctional composite materials tailored to different scenarios is limited. Achieving functional integration through micro / nanostructure design and combining it with matrix materials to realize multi-scale material integration, and considering the influence of external dynamic stimuli on the micro / nanostructure, is one of the important means to achieve dynamic tunability. Therefore, the realization of multi-scale material structure design, multi-spectral dynamic tunability, and functional integration of composite materials have become urgent needs for my country's aerospace field and military force development.

[0003] With the rapid development of the rubber industry, rubber (such as natural rubber and silicone rubber) forms a cross-linked network through vulcanization, endowing it with excellent resilience (deformation recovery rate > 90%) and resistance to permanent deformation, as well as stronger stability to oil and chemical media. Due to its unique performance advantages, it shows broad application prospects in military stealth, electronic compatibility, and civilian communications. Among them, EPDM rubber, as a high-performance synthetic rubber, despite its excellent performance in aging resistance, still faces the following key challenges in practical applications and research. To address the issues of poor mechanical properties with excessive filler and low electromagnetic wave absorption performance with insufficient filler, and to achieve a balance between excellent mechanical and electromagnetic wave absorption performance, researchers have increased their research on biomass-derived porous carbon. How to effectively utilize its abundant pore size and large specific surface area for adsorption is particularly important. Therefore, how to further modify biomass and its preparation and molding processes as fillers in rubber composites has broad research background and value.

[0004] Existing technologies enhance mechanical and microwave absorption properties by adding traditional carbon materials or additives, with additives increasing the dispersion between the filler and the rubber matrix. However, achieving a good balance between the mechanical and microwave absorption properties of composite materials by focusing on the filler itself presents a novel approach. How to modify the filler itself and achieve multi-spectral dynamic tunability to meet the demands of complex electromagnetic environments in aerospace is currently a key focus of scientific research. Summary of the Invention

[0005] This invention provides a gradient-oriented porous sound-absorbing / sound-insulating rubber, its preparation method, and its application, in order to overcome the shortcomings of the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a gradient-oriented porous microwave absorbing / sound insulating rubber, which is prepared from EPDM rubber, gradient-oriented porous filler, zinc oxide, stearic acid, sulfur, accelerator and additives; the gradient-oriented porous filler is prepared by assembling modified biomass porous carbon and single-crystal ordered bimetallic porous MOF; the modified biomass porous carbon is prepared by calcining and acidifying biomass; the preparation method of the single-crystal ordered bimetallic porous MOF is as follows: PS template is added to a mixed solution of dimethylimidazole, cobalt salt, nickel salt and organic solvent, vacuum degassing, standing and drying; then a mixed solution of ammonia and organic solvent is added to induce crystal phase formation, vacuum degassing and drying are performed to obtain the final product.

[0008] Further, the preparation method of the PS template is as follows: dissolve PVP in boiling water, add styrene, and stir at 70-80℃ for 20-40 min, preferably at 72℃ and 240 rpm for 30 min under mechanical stirring; add K2S2O8 dissolved in boiling water by sonication, and react for 20-30 h, preferably 24 h, to obtain the template; the ratio of PVP, styrene and K2S2O8 is 1-3 g: 50-70 mL: 0.5-1.5 g, preferably 2 g: 60 mL: 1 g.

[0009] Further, in the preparation method of the single-crystal ordered bimetallic porous MOF, the organic solvent is methanol; the cobalt salt is cobalt nitrate hexahydrate; the nickel salt is nickel nitrate hexahydrate; the mass ratio of PS template, dimethylimidazole, cobalt nitrate hexahydrate and nickel nitrate hexahydrate is 40-60:15-25:10-20:10-20, preferably 50:20:16:16; the first vacuum degassing time is 15-25 min, preferably 20 min, the standing time is 20-30 h, preferably 24 h, and the first drying temperature is 25-35℃, preferably 30℃; in the mixed solution of ammonia and organic solvent, the volume ratio of ammonia to organic solvent is 0.5-1.5:0.5-1.5, preferably 1:1; the second vacuum degassing time is 5-15 min, preferably 10 min, and the second drying temperature is 25-35℃, preferably 30℃.

[0010] Further, the biomass is pine cone; the preparation method of the modified biomass porous carbon is as follows: pine cone is crushed, sieved, heated to 200-300℃ at 1-3℃ / min and kept at this temperature for 1.5-2.5h to remove impurities, preferably heated to 260℃ at 2℃ / min and kept at this temperature for 2h; then heated to 750-850℃ at 1-3℃ / min and kept at this temperature for 1.5-2.5h in a nitrogen atmosphere, preferably heated to 800℃ at 2℃ / min and kept at this temperature for 2h to obtain micron-sized biomass porous carbon; then soaked in an acidic solution with pH 1-3 for acidification for 10-14h, preferably in a nitric acid solution with pH 2 for acidification for 12h, to obtain the final product.

[0011] Furthermore, the preparation method of the gradient-oriented porous filler is as follows: the modified biomass porous carbon is ultrasonically dispersed in water, and then the single-crystal ordered bimetallic porous MOF is added. The single-crystal ordered porous bimetallic MOF and the modified biomass porous carbon are assembled together by electrostatic adsorption effect to obtain the filler. The mass ratio of modified biomass porous carbon to single-crystal ordered porous bimetallic MOF is 1 to 3:1, preferably 2:1.

[0012] Furthermore, the accelerator includes accelerator M and accelerator TMTD; the auxiliary agent is a silane coupling agent.

[0013] Furthermore, the mass ratio of the EPDM rubber, gradient oriented porous filler, zinc oxide, stearic acid, sulfur, accelerator M, accelerator TMTD, and silane coupling agent is 70–130:70–130:3–7:0.5–1.5:1–2:0.2–0.7:1–5:1–3, preferably 100:100:5:1:1.5:0.5:3:2.

[0014] Secondly, this aspect provides a method for preparing the aforementioned gradient-oriented porous microwave absorbing rubber: the EPDM rubber, gradient-oriented porous filler, zinc oxide, stearic acid, sulfur, accelerator and additives are added to an open mill, mixed evenly, cut, and placed in a flat vulcanizing machine for vulcanization at 150-200°C for 5-15 minutes, preferably at 170°C for 10 minutes, to obtain the product.

[0015] Thirdly, this aspect provides a method for preparing the aforementioned gradient-oriented porous sound-insulating rubber: EPDM rubber, gradient-oriented porous filler, zinc oxide, stearic acid, sulfur, accelerator, and additives are added to an open mill, mixed evenly, cut, and placed in a flat vulcanizing machine for vulcanization at 150–200°C for 5–15 minutes, preferably at 170°C for 10 minutes; the obtained rubber is then inflated to obtain the final product.

[0016] Fourthly, the present invention provides the application of the above-mentioned gradient-oriented porous absorbing / sound-insulating rubber in absorbing / sound insulation.

[0017] The beneficial effects of this invention are as follows: This invention provides a gradient-oriented porous microwave absorbing / sound insulating rubber, its preparation method, and its application. By thermodynamically controlling the pore size of biomass, micron-sized modified biomass porous carbon is obtained. Then, utilizing the electrostatic adsorption effect, single-crystal ordered bimetallic porous MOF is assembled with the modified biomass porous carbon, achieving a gradient change in macropores, mesopores, and micropores, thereby achieving excellent impedance matching to improve electromagnetic wave absorption efficiency. Specifically, the micron-sized modified biomass porous carbon serves as a framework, inhibiting the aggregation of single-crystal ordered MOF through pore confinement effect, improving the dispersibility of fillers in the rubber. The high specific surface area of ​​the modified biomass porous carbon adsorbs vulcanizing agents, achieving slow-release vulcanization and avoiding the uneven vulcanization caused by excessive fillers in traditional systems. Furthermore, when the vulcanized rubber is inflated, the tension of the rubber-based composite structure changes with the increase of internal gas, causing a shift in the natural frequency of the rubber composite structure. The internal asymmetric pore gradient generates an impedance abrupt change interface, enhancing sound wave reflection and improving high-frequency sound insulation, thus obtaining a sound insulating rubber. By controlling the degree of bulging with air pressure, dynamic tuning of wave absorption / sound insulation is achieved. That is, the high-frequency sound insulation performance is excellent when inflated, and the electromagnetic wave absorption is enhanced when deflated. The final EPDM composite rubber-based device can achieve dynamic tuning of wave absorption / sound insulation according to different scenario requirements. Attached Figure Description

[0018] Figure 1 This is a SEM image of modified biomass porous carbon;

[0019] Figure 2 This is a SEM image of modified biomass porous carbon;

[0020] Figure 3 This is a schematic diagram of rubber inflation. a is a schematic diagram of the base, and b is a schematic diagram of the base and rubber inflation. Detailed Implementation

[0021] The present invention will be further described below with reference to specific embodiments.

[0022] Example 1

[0023] This embodiment provides a gradient-oriented porous sound-absorbing / sound-insulating rubber, the preparation method of which is as follows:

[0024] S1. The pine cones were pulverized using a pulverizer and then filtered through a sieve to obtain a uniform powder. First, the powder was placed in a muffle furnace and heated to 260℃ at 2℃ / min for 2 hours to remove impurities. Then, it was heated to 800℃ at 2℃ / min in a nitrogen atmosphere and held for 2 hours. Next, it was soaked in a nitric acid solution with pH=2 for acidification for 12 hours. After drying, modified biomass porous carbon was obtained. SEM images at different scales are shown below. Figure 1 and Figure 2 As shown.

[0025] S2. First, styrene was washed sequentially with 10wt% NaOH solution and deionized water to remove the stabilizer. Then, 2g of PVP was dissolved in 500mL of boiling deionized water and poured into a 1L three-necked flask. Subsequently, 60mL of washed styrene was added, and the mixture was equilibrated for 30min under mechanical stirring at 72℃ and 240rpm. Finally, 1g of K2S2O8 was dissolved in 50mL of boiling water using an acoustic method, and then poured into the three-necked flask to initiate polymerization. After reacting for 24h, the resulting emulsion was collected as the desired monodisperse polystyrene spheres, vacuum filtered to obtain a three-dimensionally ordered PS template, and dried overnight.

[0026] S3. Weigh 0.328g of dimethylimidazole, 0.263g of cobalt nitrate hexahydrate and 0.263g of nickel nitrate hexahydrate, pour them into 20mL of methanol solution, add 0.82g of PS template, degas under vacuum for 20min, let stand for 24h, dry in an oven at 30℃, then add 50mL of a 1:1 mixture of ammonia and methanol to induce crystal phase formation, degas under vacuum for 10min, and then dry in an oven at 30℃ to obtain a single-crystal ordered bimetallic porous MOF.

[0027] S4. Two parts of modified biomass porous carbon were ultrasonically dispersed in deionized water, and then one part of single-crystal ordered bimetallic porous MOF was added. Using the electrostatic adsorption effect, the single-crystal ordered porous bimetallic MOF and biomass porous carbon were assembled together to obtain gradient oriented porous packing.

[0028] S5. Then, add 100 parts of gradient oriented porous filler, 100 parts of EPDM rubber, 5 parts of zinc oxide, 1 part of stearic acid, 1.5 parts of sulfur, 0.5 parts of accelerator M, 3 parts of accelerator TMTD and 2 parts of silane coupling agent to the open mill. After they are fully mixed, cut them into regular strips and put them into the mold. Then put them into the flat vulcanizing machine and vulcanize at 170°C for 10 minutes to obtain EPDM rubber.

[0029] S6, such as Figure 3 As shown, EPDM rubber is fixed on the base, and the inside of EPDM rubber is inflated by adjusting the air pump and flow rate controller. The inflation pressure is 0.1MPa, resulting in gradient directional porous sound-absorbing / sound-insulating rubber.

[0030] Example 2

[0031] This embodiment provides a gradient-oriented porous sound-absorbing / insulating rubber. The preparation method is basically the same as that in Example 1, except that the inflation pressure in S6 is 0.2 MPa.

[0032] Example 3

[0033] This embodiment provides a gradient-oriented porous sound-absorbing / insulating rubber. The preparation method is basically the same as that in Example 1, except that the inflation pressure in S6 is 0.3 MPa.

[0034] Example 4

[0035] This embodiment provides a gradient-oriented porous sound-absorbing / insulating rubber, which is prepared in a manner that is basically the same as in Example 1, except that in S5, the gradient-oriented porous filler is 70 parts.

[0036] Example 5

[0037] This embodiment provides a gradient-oriented porous sound-absorbing / insulating rubber. The preparation method is basically the same as that in Example 4, except that the inflation pressure in S6 is 0.2 MPa.

[0038] Example 6

[0039] This embodiment provides a gradient-oriented porous sound-absorbing / insulating rubber. The preparation method is basically the same as that in Example 4, except that the inflation pressure is 0.3 MPa in S6.

[0040] Example 7

[0041] This embodiment provides a gradient-oriented porous sound-absorbing / insulating rubber, which is prepared in a manner that is basically the same as that in Example 1, except that in S5, the gradient-oriented porous filler is 130 parts.

[0042] Example 8

[0043] This embodiment provides a gradient-oriented porous sound-absorbing / insulating rubber. The preparation method is basically the same as that in Example 7, except that the inflation pressure in S6 is 0.2 MPa.

[0044] Example 9

[0045] This embodiment provides a gradient-oriented porous sound-absorbing / insulating rubber. The preparation method is basically the same as that in Example 7, except that in S6, the inflation pressure is 0.3 MPa.

[0046] Comparative Example 1

[0047] This comparative example provides a rubber prepared in a manner that is essentially the same as that in Example 1, except that no gradient-oriented porous filler is added.

[0048] Comparative Example 2

[0049] This comparative example provides a rubber prepared in a manner that is basically the same as that of comparative example 1, except that in S6, the inflation pressure is 0.2 MPa.

[0050] Comparative Example 3

[0051] This comparative example provides a rubber prepared in a manner that is basically the same as that of comparative example 1, except that in S6, the inflation pressure is 0.3 MPa.

[0052] Comparative Example 4

[0053] This comparative example provides a rubber prepared in a manner that is essentially the same as in Example 1, except that the modified biomass porous carbon is not assembled with a multi-level pore gradient, i.e., the gradient oriented porous filler in S5 is replaced with modified biomass porous carbon.

[0054] Comparative Example 5

[0055] This comparative example provides a rubber prepared in a manner that is basically the same as that of comparative example 4, except that in S6, the inflation pressure is 0.2 MPa.

[0056] Comparative Example 6

[0057] This comparative example provides a rubber prepared in a manner that is basically the same as that of comparative example 4, except that in S6, the inflation pressure is 0.3 MPa.

[0058] Mechanical properties, microwave absorption properties, and sound insulation properties of the rubbers from Examples 1-9 and Comparative Examples 1-6 were tested, and the results are shown in Table 1. Mechanical properties were tested using a universal testing machine, microwave absorption properties were tested using a vector network analyzer, and sound insulation properties were tested using an anechoic chamber (free field) via the reverberation chamber-anechoic chamber method.

[0059] Table 1 Mechanical properties, wave absorption properties, and sound insulation properties of rubber

[0060]

[0061]

[0062] Comparative Examples 1, 4, and 7 show that the electromagnetic wave absorption performance of the gradient-oriented porous absorbing / sound-insulating rubber does not increase with the increase of the gradient-oriented porous filler ratio. On the contrary, a higher filler ratio not only leads to impedance matching in attenuating electromagnetic waves, but also causes a decrease in strength due to stress concentration and interface defects. However, an appropriate filler ratio can play a good reinforcing role. Comparative Examples 1 and 4 show that the addition of modified biomass porous carbon improves both the wave absorption performance and mechanical properties of the rubber. Comparative Examples 1-3, 4-6, and 7-9 show that with the increase of internal air pressure, the rubber's electromagnetic wave absorption performance weakens somewhat, but its sound insulation performance is improved to a certain extent.

[0063] In this invention, unless otherwise stated, scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, the reagents, materials, and procedures used herein are all widely used in the relevant fields.

[0064] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A gradient-oriented porous sound-absorbing / sound-insulating rubber, characterized in that: It is prepared from ethylene propylene diene monomer (EPDM) rubber, gradient oriented porous filler, zinc oxide, stearic acid, sulfur, accelerators, and additives; The method for preparing the gradient oriented porous filler is as follows: modified biomass porous carbon is ultrasonically dispersed in water, and then a single-crystal ordered bimetallic porous MOF is added. The single-crystal ordered porous bimetallic MOF and modified biomass porous carbon are assembled together by electrostatic adsorption effect. The mass ratio of modified biomass porous carbon to single-crystal ordered porous bimetallic MOF is 1~3:

1. The method for preparing the modified biomass porous carbon is as follows: Pine cones are pulverized, sieved, and heated to 200-300℃ at 1-3℃ / min and held for 1.5-2.5 h to remove impurities; then, under a nitrogen atmosphere, the mixture is heated to 750-850℃ at 1-3℃ / min and held for 1.5-2.5 h to obtain biomass porous carbon; finally, it is soaked in an acidic solution with a pH of 1-3 for acidification for 10-14 h to obtain the final product. The method for preparing the single-crystal ordered bimetallic porous MOF is as follows: a PS template is added to a mixed solution of dimethylimidazole, cobalt salt, nickel salt and organic solvent, degassed under vacuum, allowed to stand and dried; then a mixed solution of ammonia and organic solvent is added, degassed under vacuum and dried to obtain the MOF; the cobalt salt is cobalt nitrate hexahydrate; the nickel salt is nickel nitrate hexahydrate; the mass ratio of PS template, dimethylimidazole, cobalt nitrate hexahydrate and nickel nitrate hexahydrate is 40~60∶15~25∶10~20∶10~20.

2. The gradient-oriented porous sound-absorbing / sound-insulating rubber according to claim 1, characterized in that: The PS template is prepared by dissolving PVP in boiling water, adding styrene, stirring at 70-80℃ for 20-40 min to reach equilibrium, adding K2S2O8 dissolved in boiling water using a sonic method, and reacting for 20-30 h to obtain the final product. The ratio of PVP, styrene and K2S2O8 is 1~3 g : 50~70 mL : 0.5~1.5 g.

3. The gradient-oriented porous sound-absorbing / sound-insulating rubber according to claim 1, characterized in that: In the preparation method of the single-crystal ordered bimetallic porous MOF, the organic solvent is methanol. The first vacuum degassing time is 15~25 min, the standing time is 20~30 h, and the first drying temperature is 25~35 ℃; In the mixed solution of ammonia and organic solvent, the volume ratio of ammonia to organic solvent is 0.5~1.5:0.5~1.5; The second vacuum degassing time is 5~15 min, and the second drying temperature is 25~35 ℃.

4. The gradient-oriented porous sound-absorbing / sound-insulating rubber according to claim 1, characterized in that: The accelerator includes accelerator M and accelerator TMTD; The additive is a silane coupling agent.

5. The gradient-oriented porous sound-absorbing / sound-insulating rubber according to claim 4, characterized in that: The mass ratio of the EPDM rubber, gradient oriented porous filler, zinc oxide, stearic acid, sulfur, accelerator M, accelerator TMTD and silane coupling agent is 70~130∶70~130∶3~7∶0.5~1.5∶1~2∶0.2~0.7∶1~5∶1~3.

6. The method for preparing gradient-oriented porous microwave absorbing / sound insulating rubber according to any one of claims 1 to 5, characterized in that: The EPDM rubber, gradient oriented porous filler, zinc oxide, stearic acid, sulfur, accelerator and additives are added to an open mill, mixed evenly, cut, and placed in a flat vulcanizing machine for vulcanization at 150~200 ℃ for 5~15 min; the obtained rubber is then inflated to obtain the final product.

7. The application of the gradient-oriented porous sound-absorbing / sound-insulating rubber as described in any one of claims 1 to 5 in sound absorption / insulation.

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