CN114874588B - Sound-absorbing insulation composite material for double-insulation double-shielding Faraday cage and preparation method thereof - Google Patents

Abstract

The invention relates to the technical field of sound-absorbing insulating composite materials, in particular to a sound-absorbing insulating composite material for a double-insulation double-shielding Faraday cage and a preparation method thereof. The raw materials comprise epoxy resin, a curing agent, an accelerator, organic microspheres and basalt fibers. The invention provides a selection scheme of a double-insulation double-shielding Faraday cage sound-absorbing material for the first time, and provides an application scheme of using an epoxy resin-based composite foam insulation material as a sound-absorbing material. The sound-absorbing/sound-insulating composite material is prepared by compounding the modified basalt fibers, the organic microspheres and the epoxy resin, the performance of the composite material is tested, the acoustic mechanism of the composite material is analyzed, the optimized process for preparing the sound-insulating/sound-absorbing material and related theories are obtained, and theoretical basis and technical support are provided for manufacturing the novel sound-absorbing/sound-insulating material. Moreover, the novel material is light in weight, convenient to transport and quick to construct.

Description

Sound-absorbing insulating composite material for double-insulation and double-shielding Faraday cage and preparation method thereof

technical field

The invention relates to the technical field of sound-absorbing and insulating composite materials, in particular to a sound-absorbing and insulating composite material for double-insulated and double-shielded Faraday cages and a preparation method thereof.

Background technique

At the same time, the high-voltage test hall with double insulation and double shielding function (similar to the structure of Faraday cage) is used as a shielding cavity to protect and isolate electromagnetic interference, but too closed environment is prone to noise interference, and the noise interference is mainly caused by human speech Echo, in a high-voltage laboratory, produces reverberation, which is the result of the accumulation of sound in the room being continuously reflected by the interface. Reverberation can increase the sound in a room by 15dB while reducing speech intelligibility. The human ear is very sensitive to hearing. A normal person can detect a sound change of 1dB, and a difference of 3dB will feel a significant difference. The human ear has a masking effect. When one sound is 10dB higher than another, the smaller sound is difficult to hear and understand due to masking, resulting in inaudible even when speaking at close range. Therefore, it is particularly necessary to provide a sound-absorbing and insulating composite material for a double-insulated and double-shielded Faraday cage.

When the sound wave is incident on the surface of the material, part of the sound energy will be reflected and part of the sound energy will be absorbed by the interface. The unreflected sound energy mainly has three forms of dissipation: one is transmitted through the material to the other side; the other is converted into heat inside the material and dissipated; the third is the vibration kinetic energy is transferred along the boundary structure. After the sound wave is incident on the surface of the material, the sound energy that is not reflected is considered as the absorbed sound energy. According to the different sound-absorbing principles of materials, sound-absorbing materials are divided according to the sound-absorbing mechanism, and can be roughly divided into resonant sound-absorbing materials and porous sound-absorbing materials.

When the resonant sound-absorbing material is used as a resonant system, it has a fixed vibration frequency. When the vibration frequency of the sound wave is close to the natural vibration frequency of the system, the resonant sound-absorbing material will vibrate violently inside, and the sound energy overcomes the friction during the vibration process. The damping work is converted into heat energy and consumed, which makes the sound wave gradually attenuate, so as to achieve the effect of sound absorption and noise reduction. Due to the strong selectivity of resonant sound-absorbing materials for sound wave absorption, only when the sound wave vibration frequency is close to the natural vibration frequency of the system, it has a high sound absorption coefficient. Therefore, resonant sound-absorbing materials are often used to absorb middle and low frequency sound waves.

The sound absorption principle of porous sound-absorbing materials is mainly: there are a large number of interpenetrating and uniformly distributed micropores and gaps inside the material. Vibration will cause vibration of adjacent particles, air vibration will cause vibration of material fibers, and friction and viscosity will be generated between each other, and sound energy will be converted into heat energy for dissipation; at the same time, because of the difference in vibration speed between particles, the air inside the material will There is a temperature difference with the material fiber, resulting in heat transfer and loss of sound energy. Porous sound-absorbing materials are currently the most commonly used materials for noise reduction, and they are divided into fiber-like sound-absorbing materials and foam-like sound-absorbing materials.

Fiber-based sound-absorbing materials Fiber-based sound-absorbing materials can be divided into organic fiber sound-absorbing materials, metal fiber sound-absorbing materials and inorganic fiber sound-absorbing materials; organic sound-absorbing fiber materials are mostly plant fibers and animal fur. This kind of material has good sound-absorbing performance at medium and high frequencies and low cost of use, but the sound-absorbing performance of low-frequency and ultra-high frequency is very poor, and it does not have fireproof, anti-station, anti-corrosion candle, moisture-proof and other properties, and now it is rare Use alone. Metal fiber sound-absorbing materials are a kind of sound-absorbing materials with broad development prospects. At present, the common metal fiber sound-absorbing materials include stainless steel fibers and aluminum fibers. It has the characteristics of high strength, corrosion resistance, high temperature resistance and strong environmental adaptability, etc., but the cost is high, it is not suitable for mass production, and its conductivity is higher than other types of sound-absorbing materials, which is required by double-insulated and double-shielded Faraday cages. The insulation requirements do not meet. Inorganic fiber sound-absorbing material is a kind of fiber material based on inorganic minerals, mainly including fiber sound-absorbing materials such as glass fiber, basalt fiber, asbestos fiber, carbon fiber, etc. These materials not only have good sound-absorbing performance, but also have fire resistance, moisture resistance and corrosion resistance It is a sound-absorbing material commonly used in the prior art, but it needs an additional carrier load to realize its application, and an excessively high load of inorganic fiber sound-absorbing materials will affect the overall performance of the composite material. If the load is too small, the absorption The sound effect is not good.

Foam sound-absorbing materials can be divided into three categories according to their physical and chemical properties: foam glass sound-absorbing materials, foam metal sound-absorbing materials and foam plastic sound-absorbing materials. Foam glass porous sound-absorbing material is made of glass powder, which is fired at high temperature under the action of foaming agent and external dopant. The advantages of this type of material are light weight, odorless, non-flammable, non-aging and deformation, easy processing and no environmental pollution. Its disadvantages are mainly low strength and easy damage. Foam metal sound-absorbing material is a new type of porous sound-absorbing material. A large number of bubbles are generated in the metal phase through the foaming process. These bubbles constitute the pores of the sound-absorbing material. This type of material has good electromagnetic shielding properties. In addition, because it It is made of metal and has strong corrosion resistance. But also because of its metal properties, its water resistance and weather resistance are also poor, and the most important thing is that its manufacturing process is more complicated, so the cost is higher. Foamed plastic porous sound-absorbing materials are made by foaming different resins. The advantages of this type of material are simple manufacturing process, low cost, shockproof, moisture-proof and corrosion-resistant, and available frequency bandwidth.

Contents of the invention

Based on the above, the present invention provides a sound-absorbing and insulating composite material for a double-insulated and double-shielded Faraday cage and a preparation method thereof. Combining the advantages of inorganic fiber sound-absorbing materials and foam-like porous sound-absorbing materials, a composite material with good sound-absorbing and insulating functions is prepared.

One of the technical proposals of the present invention is a sound-absorbing and insulating composite material for a double-insulated and double-shielded Faraday cage. The raw materials include 25-30 parts of epoxy resin, 22-28 parts of curing agent, and 0.1-0.5 parts of accelerator. , 0.8-1.5 parts of organic microspheres, 0.8-1.5 parts of basalt fiber.

Further, in terms of parts by mass, the raw materials include 28-29 parts of epoxy resin, 24-25 parts of curing agent, 0.2-0.3 parts of accelerator, 1.0-1.1 parts of organic microspheres, and 1.0-1.0 parts of basalt fiber.

Further, the organic microspheres are polymethyl methacrylate (PMMA) hollow microspheres.

Further, the basalt fiber is a surface-treated modified basalt fiber, and the specific steps include:

(1) The basalt fiber obtains the hydroxyl grafted basalt fiber through hydroxyl grafting;

(2) Using a silane coupling agent to modify the surface of the hydroxyl-grafted basalt fiber to obtain a surface-treated modified basalt fiber.

Further, the step (1) specifically includes: placing the chopped basalt fiber in a 5 mol/L sodium hydroxide solution, treating it at 120°C for 2 hours, cleaning and filtering until the pH value is neutral, and drying at 80°C Dry to obtain hydroxyl-grafted basalt fibers.

Further, the step (2) specifically includes: dissolving the coupling agent KH-550 in 95% ethanol solution, adding hydrochloric acid to adjust the pH value to 5, adding hydroxyl grafted basalt fibers, heating and stirring at 60°C for 6 hours, and then suction filtration , washing, and vacuum drying to obtain surface-treated modified basalt fibers; wherein the solid-liquid ratio of coupling agent KH-550 and 95% ethanol solution is 1g:500mL.

Further, the vacuum drying is vacuum drying at 120° C. for 24 hours.

The second technical solution of the present invention, the preparation method of the sound-absorbing and insulating composite material for the double-insulated and double-shielded Faraday cage, comprises the following steps: adding a curing agent to the epoxy resin, and then dispersing the basalt fiber in the epoxy resin, stirring and mixing After homogenizing, add an accelerator, add organic microspheres after vacuum stirring again, pour and solidify after vacuum defoaming to obtain the sound-absorbing and insulating composite material for double-insulated and double-shielded Faraday cages.

Further, the vacuum defoaming condition: a vacuum degree of 98 kPa; the curing condition: curing at 90° C. for 50 minutes, and then raising the temperature to 110° C. for curing for 4 hours. Curing at 90°C for 50 minutes is pre-curing, the purpose is to increase the viscosity of the mixed system and avoid serious stratification during curing. After stirring/vacuum defoaming again, solidify at 110° C. for 4 hours.

The third technical solution of the present invention is the application of the sound-absorbing and insulating composite material for the double-insulated and double-shielded Faraday cage in the double-insulated and double-shielded Faraday cage.

Further, the thickness of the sound-absorbing and insulating composite material for the double-insulated and double-shielded Faraday cage is 200±0.2mm.

Compared with prior art, the beneficial effect of the present invention:

In the present invention, composite foam plastic resin is used as a matrix, organic microspheres and fiber materials are used as filling materials, and auxiliary agents (modifiers and curing agents for basalt fibers) are organically combined to produce a synergistic effect between various raw materials to obtain a Sound-absorbing insulating composite with good properties. Its attenuation of sound waves is mainly achieved through two effects. The first is the damping effect of the polymer matrix. In addition, the organic microspheres in the syntactic foam can strengthen the interaction between the material and the sound wave due to the reflection and scattering of the sound wave by the organic microsphere, which is beneficial to the attenuation of the sound wave by the material.

In terms of mechanical properties, basalt fiber is a fiber between carbon fiber and glass fiber, but its price is about 1/7 of that of carbon fiber, which is more cost-effective. In terms of acoustics, its sound absorption coefficient can reach up to 0.99, which is higher than that of glass fiber, and it is a good acoustic functional material. In terms of heat, its thermal conductivity is low. At 25°C, the thermal conductivity of basalt fiber board is lower than 0.04W/(m·K). The use temperature of basalt fiber is -260 to 700°C, which is much higher than that of glass fiber. The working temperature of carbon fiber is -600 to 800°C, which seems to be a wide range. In fact, carbon fiber starts to oxidize at 300°C, so it has an advantage in an oxygen-free environment. Electrically, the volume resistivity of basalt fiber is lower than that of aramid fiber, but it is an order of magnitude higher than that of glass fiber. After special treatment, its dielectric loss tangent value is 50% lower than that of glass fiber, which can be used to manufacture high-voltage insulating materials. and heat-resistant dielectric materials. In addition, basalt fiber also has good chemical stability, environmental protection and composite compatibility with other materials. Basalt fiber is heated in 2mol/L HCl and NaOH for 3 hours, and its strength attenuation is only 2% and 6% respectively. Even in the artificial seawater environment with alternating dry and wet conditions, its corrosion resistance and aging resistance are stronger than other fibers. , and the hygroscopicity of basalt fiber is extremely low, only 0.2% to 0.3%, and basalt fiber also has good chemical stability. When basalt fiber is combined with other materials (such as various resins, concrete, metal and other fibers, etc.), it has a stronger affinity than glass fiber and carbon fiber, which means that it is more advantageous to prepare composite materials with basalt fiber. The modification of the basalt fiber after hydroxyl grafting enhances its affinity with the matrix resin, which greatly improves the performance of the overall composite material.

The present invention proposes the selection scheme of the double-insulated and double-shielded Faraday cage sound-absorbing material for the first time, and proposes the application scheme of using the epoxy resin-based composite foam insulation material as the sound-absorbing material. By using modified basalt fiber, organic microspheres and epoxy resin to prepare sound-absorbing/sound-insulating composite materials, and testing its performance, analyzing its acoustic mechanism, and obtaining an optimized process and related theory for preparing sound-absorbing/sound-absorbing materials, it is a new sound-absorbing/sound-absorbing material. The manufacture of sound insulation materials provides theoretical basis and technical support. Moreover, the new material is light in weight, which is convenient for transportation and rapid construction.

Description of drawings

Fig. 1 is the flow chart of the preparation of sound-absorbing and insulating composite foam material according to Embodiment 1 of the present invention;

Fig. 2 is the result graph of the sound absorption coefficient of the sound-absorbing and insulating composite foam material prepared in Example 1 of the present invention and Comparative Example 1;

3 is a schematic diagram of the sound-absorbing principle of the sound-absorbing and insulating composite foam material prepared in Example 1 of the present invention;

Figure 4 is a front view of the assembly of the sound-absorbing and insulating composite foam material prepared in Example 1 of the present invention and the double-shielding double-insulating metal mesh;

Figure 5 is a side view of the assembly of the sound-absorbing and insulating composite foam material prepared in Example 1 of the present invention and the double-shielding double-insulating metal mesh;

Fig. 6 is an oblique view of the assembly of the sound-absorbing and insulating composite foam material prepared in Example 1 of the present invention and the double-shielding double-insulating metal mesh.

Detailed ways

Various exemplary embodiments of the present invention will now be described in detail. The detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features and embodiments of the present invention.

It should be understood that the terminology described in the present invention is only used to describe specific embodiments, and is not used to limit the present invention. In addition, regarding the numerical ranges in the present invention, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated value or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded from the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only the preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and/or materials in connection with which the documents are described. In case of conflict with any incorporated document, the contents of this specification control.

It will be apparent to those skilled in the art that various modifications and changes can be made in the specific embodiments of the present invention described herein without departing from the scope or spirit of the present invention. Other embodiments will be apparent to the skilled person from the description of the present invention. The description and examples of the invention are illustrative only.

As used herein, "comprising", "comprising", "having", "comprising" and so on are all open terms, meaning including but not limited to.

Example 1

The specific preparation flow chart is shown in Figure 1;

(1) Weigh raw materials: epoxy resin E-51: 28.9059g, curing agent A6: 24.5700g, accelerator (DMP-30): 0.2674g, organic microspheres (polymethyl methacrylate (PMMA) hollow Microspheres): 1.0695g, chopped basalt fiber (3mm) 1.0695g.

(2) Hydroxyl grafting: Add chopped basalt fiber to 5mol/L sodium hydroxide solution, treat it at 120°C for 2 hours, then wash and filter with deionized water until the pH value is neutral, and the obtained The hydroxyl-grafted basalt fiber was dried at 80°C for 5 hours.

(3) Dissolve 1 g of coupling agent KH-550 in 95% ethanol solution, add dilute hydrochloric acid to adjust the pH value to 5. Add 5 g of hydroxyl-grafted basalt fiber, heat and stir at 60°C for 2 hours, then cool to room temperature, filter the solution through a 0.22 μm polyvinylidene fluoride membrane, and rinse the sample on the membrane with ethanol solution three times to further remove ungrafted Branch coupling agent, followed by drying under vacuum at 120°C for 24 hours to obtain surface-treated chopped basalt fibers.

(4) Using a vacuum planetary mixer, add a curing agent to the epoxy resin, and then disperse the surface-treated chopped basalt fibers in the epoxy resin, the rotation speed: 1000r/min, and the time: 300s. After adding the accelerator, stir in vacuum to form a premix, then add organic microspheres for stirring/vacuum defoaming, speed: 1000r/min, time: 500s. The suspension was obtained by defoaming under the condition of vacuum degree of 98kPa.

(5) Pour the mixed suspension (basalt fiber-filled epoxy resin/microsphere system) into a mold, pre-cure at 90°C for 50 minutes to obtain a slightly layered basalt fiber-filled epoxy resin/microsphere system, and stir again /Vacuum degassing, pour the mold into the mold and then rise to 110° C. for 4 hours to cure and release the mold to obtain the sound-absorbing and insulating composite material.

Comparative example 1

Same as Example 1, the difference is that the chopped basalt fiber is replaced by an equal amount of 3mm glass fiber.

Effect verification example 1

The composite material prepared in embodiment 1 and comparative example 1 is carried out sound absorption coefficient measurement (the test sample is contained in one end of a straight, rigid, airtight impedance tube. The plane sound wave in the tube is produced by random noise sound source. In Measure the sound pressure at two positions close to the sample, obtain the sound transfer function of the two microphone signals, and calculate the normal incident complex reflection factor, normal incident sound absorption coefficient and acoustic impedance rate of the specimen through this function), the result See Figure 2. From Fig. 2, it can be concluded that the sound absorption effect of Comparative Example 1 is better before the noise is 2000Hz, and is above Example 1 as a whole; after 2000Hz, the sound absorption effect of Example 1 is improved, and it exceeds that of Comparative Example 1 as a whole, and the sound absorption effect of Example 1 The highest sound absorption coefficient is much larger than Comparative Example 1. It shows that the sound absorption effect of basalt fiber is better after 2000Hz.

The sound-absorbing principle of the sound-absorbing insulating composite material prepared in Example 1 is shown in Fig. 3. In Fig. 3, E ₀ is the total incident sound energy, E ₁ is the reflected sound energy, E ₂ is the sound energy absorbed by the sound-absorbing material, and E ₃ is the transmitted sound energy. The sound-absorbing and insulating composite foam material in this embodiment combines the advantages of fiber and foam sound-absorbing, and under the same noise condition, its parameter _E2 is greater than that of the sound-absorbing material constructed with a single filler.

The sound-absorbing and insulating composite foam material in Example 1 uses basalt fibers and organic microspheres as fillers. Among them, basalt fiber avoids the characteristics of poor performance of organic fiber sound-absorbing materials such as fire prevention, anti-station, anti-corrosion candle, moisture-proof, etc., and it is not like metal fiber sound-absorbing materials that have high cost, are not suitable for mass production, and have strong electrical conductivity. ; Compared with foam glass porous sound-absorbing materials, organic microspheres have higher strength and are not easy to be damaged. Compared with foam metal sound-absorbing materials, they have better water resistance, weather resistance, and electrical insulation. The manufacturing process is simple and the cost is low. mass production.

Comparative example 2

Same as in Example 1, the difference is that the step (2) and step (3) of surface treatment and modification of chopped basalt fibers are omitted.

Comparative example 3

Same as Example 1, the difference is that the organic microspheres are omitted.

The sound absorption coefficient of the composite material of Comparative Example 2-3 was tested, and the results showed that the sound absorption performance of Comparative Example 2 showed a downward trend as a whole, and reached the maximum sound absorption coefficient in the noise interval of 1500 Hz, which was about 50% of that of Example 1; The sound absorption coefficient of 3 does not fluctuate greatly as a whole, and they are all at a low level, with no prominent sound absorption range.

Application example

Assemble the sound-absorbing and insulating composite material prepared in Example 1 and the double-shielded double-insulated metal mesh (see Figures 4-6), where Figure 4 is the front view of the assembly, Figure 5 is the side view of the assembly, and Figure 6 is the oblique view. The thickness of the sound-absorbing insulating composite material is 200±0.2mm, and then the indoor sound increase value is tested. The results show that the sound-absorbing effect of the sound-absorbing insulating composite material and double-shielded double-insulated metal mesh is better than that of the test sample, due to the unique wave shape The design, coupled with the fact that the material is filled with small voids, can absorb a large amount of incoming sound wave energy and attenuate the sound wave. Through the back and forth reflection of the sound wave in the composite material, the sound with a frequency as low as 500HZ is absorbed, so that the added value of the indoor sound is relatively low.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention within.

Claims (9)

1. The sound-absorbing insulating composite material for the double-insulation double-shielding Faraday cage is characterized by comprising, by mass, 25-30 parts of epoxy resin, 22-28 parts of curing agent, 0.1-0.5 part of accelerator, 0.8-1.5 parts of organic microspheres and 0.8-1.5 parts of basalt fibers;

the basalt fiber is a surface treatment modified basalt fiber, and the specific steps comprise:

(1) Carrying out hydroxyl grafting on the basalt fiber to obtain hydroxyl grafted basalt fiber;

(2) Carrying out surface treatment modification on the hydroxyl grafted basalt fiber by using a silane coupling agent to obtain a surface treatment modified basalt fiber;

the organic microspheres are polymethyl methacrylate hollow microspheres.

2. The sound-absorbing insulating composite material for the double-insulation double-shielding Faraday cage according to claim 1, wherein the raw materials comprise, by mass, 28-29 parts of epoxy resin, 24-25 parts of curing agent, 0.2-0.3 part of accelerator, 1.0-1.1 parts of organic microspheres, and 1.0 part of basalt fibers.

3. The sound-absorbing insulating composite for a double-insulated, double-shielded faraday cage according to claim 1, wherein the step (1) comprises in particular: and (2) placing the chopped basalt fiber in a 5mol/L sodium hydroxide solution, treating for 2 hours at the temperature of 120 ℃, cleaning, filtering until the pH value is neutral, and drying at the temperature of 80 ℃ to obtain the hydroxyl grafted basalt fiber.

4. The sound absorbing and insulating composite material for a double-insulated, double-shielded faraday cage according to claim 1, wherein the step (2) comprises: dissolving a coupling agent KH-550 into a 95% ethanol solution, adding hydrochloric acid to adjust the pH value to 5, adding hydroxyl grafted basalt fiber, heating and stirring at 60 ℃ for 6 hours, and then performing suction filtration, washing and vacuum drying to obtain the surface-treated modified basalt fiber; wherein the material-liquid ratio of the coupling agent KH-550 to 95% ethanol solution is 1g:500mL.

5. The sound-absorbing insulation composite for a double-insulated, double-shielded faraday cage according to claim 4, wherein the vacuum drying is performed at 120 ℃ for 24 hours.

6. A method of making a sound absorbing and insulating composite for a double insulated double shielded Faraday cage according to any of claims 1-5, comprising the steps of: and adding a curing agent into the epoxy resin, dispersing the basalt fiber into the epoxy resin, uniformly stirring, adding an accelerant, stirring again in vacuum, adding the organic microspheres, defoaming in vacuum, and pouring and curing to obtain the sound-absorbing insulating composite material for the double-insulation double-shielding Faraday cage.

7. The method for preparing the sound-absorbing and insulating composite material for the double-insulated and double-shielded faraday cage according to claim 6, wherein the vacuum defoaming condition is as follows: vacuum degree of 98kPa, and curing conditions: curing at 90 ℃ for 50min, and then heating to 110 ℃ for curing for 4h.

8. Use of the sound absorbing insulating composite for a double insulated double shielded faraday cage according to any of claims 1 to 5 in a double insulated double shielded faraday cage.

9. The use according to claim 8, wherein the sound absorbing insulating composite for a double insulated double shielded faraday cage has a thickness of 200 ± 0.2mm.

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