Lightweight high-strength high-performance green electromagnetic shielding functional paper and preparation method thereof

Abstract

The invention relates to the crossing field of electromagnetic shielding materials, carbon fiber paper and specialty paper, and discloses lightweight high-strength high-effect green electromagnetic shielding functional paper and a preparation method thereof. According to the method, bleached paper pulp is used as a supporting network, and 3mm short carbon fibers are used as conductive dopants. The method comprises the following steps: pulping paper pulp to swell and fibrillate the paper pulp to improve the binding force between fibers; then carrying out surface modification treatment on the carbon fibers by using concentrated sulfuric acid to increase the binding force between the carbon fibers and cellulose; finally, the pulped paper pulp and the modified carbon fibers are added into water according to a certain proportion to be stirred, and the lightweight, high-strength and high-efficiency electromagnetic shielding functional paper is obtained through a wet papermaking process. Test results show that the electromagnetic shielding effectiveness of the material in an X wave band (8.2-12.4 GHz) reaches 52.8 dB, the specific shielding effectiveness (SSE / t) can reach 5818.42 dB * cm < 2 > * g <-1 >, and meanwhile, the material has excellent tensile strength (19.9 MPa) and low density of 0.2867 g / cm < 3 >. The invention provides a feasible technical path for developing low-density, high-efficiency and degradable electromagnetic shielding functional paper.

Description

Technical Field

[0001] This invention relates to the interdisciplinary fields of electromagnetic shielding materials, carbon fiber paper, and specialty paper, specifically to a conductive functional paper with low density, high mechanical strength, and high shielding effectiveness, and its preparation method. Background Technology

[0002] The rapid development of modern communication technology and the surge in the complexity of electronic devices have made electromagnetic radiation and interference a core challenge that cannot be ignored from the chip level to the system level. This problem not only directly jeopardizes the stable operation of highly sensitive electronic devices and the integrity of high-speed information transmission, but also poses a clear potential threat to human health, equipment lifespan, and the safety of the entire communication system through long-term field effect accumulation. To effectively achieve electromagnetic isolation and suppress signal crosstalk, constructing functional shielding structures using conductive or magnetic materials inside and outside the equipment has become the mainstream protection solution in the industry. According to the standards organizations such as IEEE, the shielding effectiveness of commercial electromagnetic interference shielding materials must be no less than 20 dB to be considered to have basic practical value, and in high-end fields such as aerospace and precision medicine, this threshold is even higher. Looking at the current materials technology system, conductive polymers show broad application prospects to meet the new demands of "lightweight" and "flexible" designs, but they generally encounter bottlenecks in microstructure control and macroscopic performance synergy, making it difficult to achieve an ideal balance between excellent mechanical toughness, fatigue strength, and shielding stability under long-term environmental conditions. On the other hand, while traditional metallic shielding materials (such as copper, aluminum foil, and their alloys) offer excellent intrinsic shielding performance due to their high conductivity, their inherent high density, susceptibility to surface oxidation and corrosion, and tendency to induce strong electromagnetic wave secondary reflections in high-frequency scenarios, causing "space pollution," significantly limit their application in modern integrated electronics and wearable devices. Therefore, developing a new generation of electromagnetic shielding materials that combine low density, high shielding effectiveness, good mechanical adaptability, and environmental durability has become a key research focus in the interdisciplinary field of materials science and cutting-edge electronic engineering.

[0003] The papermaking process demonstrates unique and diverse advantages in the field of electromagnetic shielding materials. Its naturally formed three-dimensional interconnected porous structure not only provides an ideal carrier for the uniform loading of carbon fibers but also allows for the construction of efficient electromagnetic wave absorption and attenuation channels by controlling fiber morphology and distribution. This mature wet-forming process is characterized by low cost and ease of large-scale production, meeting the manufacturing needs of large-area shielding materials. The matrix properties of cellulose fibers give the material unique advantages of being lightweight, flexible, and biodegradable, making it particularly suitable for flexible electronics and wearable devices. Through ingenious material design and functional modification, such as constructing gradient impedance structures or introducing magnetic components, its electromagnetic parameters can be further optimized to achieve a low-reflection shielding mechanism dominated by absorption. These characteristics give paper-based shielding materials broad prospects in the modern electronics field, which pursues lightweight, flexible, and green sustainable development, providing innovative solutions to problems such as the heavy weight, easy corrosion, and secondary pollution of traditional metal shielding materials.

[0004] Developing a new generation of electromagnetic shielding materials that combine low density, high shielding effectiveness, good mechanical adaptability and environmental durability, especially by optimizing the uniform dispersion and strong interfacial bonding of carbon fibers in paper-based materials through interface engineering, has become a key research direction in the interdisciplinary field of materials science and cutting-edge electronic engineering. Summary of the Invention

[0005] This invention aims to provide a lightweight, high-strength, high-efficiency, and green electromagnetic shielding functional paper and its preparation method. By sulfonation modification to enhance the interfacial bonding between carbon fibers and cellulose, the problem of uneven dispersion and performance imbalance is solved, achieving synergistic optimization of low density, high shielding, high strength, and environmental friendliness, thus meeting the application needs of aerospace, flexible electronics, and other fields.

[0006] The technical solution adopted in this invention is as follows:

[0007] A method for preparing a lightweight, high-strength, high-efficiency, and green electromagnetic shielding functional paper includes the following steps:

[0008] Step (1): After soaking the bleached pulp in water until it is fully swollen, it is then decomposed and beaten to prepare high-freezing pulp;

[0009] Step (2): Add 3mm short carbon fibers to concentrated sulfuric acid solution for sulfonation treatment. After washing until neutral, sulfonated carbon fibers are obtained.

[0010] Step (3): Add the high-beating pulp obtained in step (1) and the sulfonated carbon fiber obtained in step (2) to water and stir to obtain a mixed slurry;

[0011] Step (4): The mixed pulp obtained in step (3) is decomposed and wet papermaking is used to obtain wet paper sheets;

[0012] Step (5): Dry the wet paper obtained in step (4) to obtain lightweight, high-strength, high-efficiency green electromagnetic shielding functional paper.

[0013] Furthermore, the bleached pulp is bleached eucalyptus pulp.

[0014] Furthermore, the high-beating pulp has a beatness of 50°SR.

[0015] Furthermore, in step (2), the mass concentration of concentrated sulfuric acid is 98%, and the mass-volume ratio of 3 mm short-cut carbon fiber to concentrated sulfuric acid is 1 g: 60 mL.

[0016] Furthermore, in step (2), the sulfonation treatment is carried out at a temperature of 80°C for 1 hour.

[0017] Furthermore, in step (3), the basis weight of the finished paper is 80-240 g / m³. 2 Sulfonated carbon fiber accounts for 10-40 wt% of the total mass of oven-dry pulp fiber and sulfonated carbon fiber.

[0018] Furthermore, in step (5), the drying temperature is 105°C and the time is 20 min.

[0019] The functional paper prepared by the method of the present invention has a minimum density of 0.28674 g / cm³. 3 It has a tensile strength of up to 19.9 MPa, an electromagnetic shielding effectiveness of up to 52.8 dB in the X-band (8.2-12.4 GHz), and a specific shielding effectiveness (SSE / t) of up to 5818.42 dB·cm. 2 ·g -1 .

[0020] The present invention has the following beneficial effects:

[0021] This invention uses bleached pulp as the supporting network and 3mm chopped carbon fibers as the conductive dopant. First, the bleached pulp is treated with beating, which, through swelling and fibrillation, significantly improves the bonding force between cellulose fibers. Then, the 3mm chopped carbon fibers are sulfonated with concentrated sulfuric acid to increase the number of oxygen-containing hydrophilic functional groups on the carbon fiber surface, allowing for more uniform dispersion in the pulp suspension and forming a more uniform conductive network. This enhances the hydrogen bonding force and interfacial compatibility between the carbon fibers and cellulose fibers. This optimization treatment enables better bonding between cellulose and carbon fibers, forming a uniform cross-linked network. Subsequently, a lightweight, high-strength, and high-efficiency electromagnetic shielding functional paper is successfully produced using a wet papermaking process. Furthermore, this invention achieves controllable performance by adjusting the matching relationship between basis weight (80-240 g / m²) and carbon fiber doping ratio (10-40 wt%). This material exhibits excellent performance in electromagnetic shielding applications, achieving an electromagnetic shielding effectiveness of 52.8 dB in the X-band (8.2-12.4 GHz) and a specific shielding effectiveness (SSE / t) of 5818.42 dB·cm. 2 ·g -1 It also possesses excellent tensile strength (19.9 MPa) and low density (0.2867 g / cm³). 3 It also possesses environmentally friendly properties, providing a promising technological path for the development of next-generation green electromagnetic shielding materials. This material demonstrates enormous application potential in fields with high electromagnetic shielding requirements, such as electronics, aerospace, new energy equipment, wearable technology, and smart homes. Attached Figure Description

[0022] Figure 1 a is a graph showing the change in tensile properties of CFP with different basis weights in Comparative Example 4;

[0023] Figure 1 b is a graph showing the effect of different sulfonated carbon fiber ratios on the tensile properties of SCFP in Comparative Example 2;

[0024] Figure 1 c is a graph showing the change in tensile properties of SCFP with different basis weights in Comparative Example 3;

[0025] Figure 1 d is a graph showing the change in CFP density with different weights in Comparative Example 4;

[0026] Figure 1 e is a graph showing the effect of different sulfonated carbon fiber ratios on SCFP density in Comparative Example 2;

[0027] Figure 1 f is a graph showing the change in SCFP density with different weights in Comparative Example 3;

[0028] Figure 2a is a graph showing the change in electromagnetic shielding effectiveness of CFP with different weights in Comparative Example 4;

[0029] Figure 2 b is a graph showing the effect of different proportions of sulfonated carbon fiber on the electromagnetic shielding effectiveness of SCFP in Comparative Example 2.

[0030] Figure 2 c is a graph showing the change in electromagnetic shielding effectiveness of SCFP with different weights in Comparative Example 3.

[0031] Figure 2 d is a graph showing the change in the shielding effectiveness of CFP with different basis weights in Comparative Example 4;

[0032] Figure 2 e is a graph showing the effect of different proportions of sulfonated carbon fiber on the shielding effectiveness of SCFP in Comparative Example 2;

[0033] Figure 2 f is a graph showing the change in the shielding effectiveness of SCFP with different weights in Comparative Example 3. Detailed Implementation

[0034] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. However, it should be understood that the scope of protection of the present invention is not limited to the specific implementation methods.

[0035] Example 1

[0036] A method for preparing a lightweight, high-strength, high-efficiency, green electromagnetic shielding functional paper is as follows:

[0037] (1) High freeness bleached eucalyptus pulp was obtained by pulping operation: 365 g of bleached eucalyptus pulp was soaked in 5 L of water for more than 4 hours to fully swell. After adding water to 18 L in the Wali pulper, the pulp was slowly added and then subjected to 0.5 h of descaling and 1 h of pulping treatment to obtain 50°SR pulp with the required freeness.

[0038] (2) Add 5 g of 3 mm short carbon fiber to 300 mL of 98% sulfuric acid solution and stir in a water bath at 80°C for 1 h. Then filter using a sand core funnel and wash repeatedly with water and dilute sodium bicarbonate solution until the carbon fiber is neutral to obtain sulfonated carbon fiber.

[0039] (3) Add the high-freezing pulp obtained in step (1) and the sulfonated carbon fiber obtained in step (2) to water and stir to obtain a mixed pulp. The pulp content is 80 g / m³. 2 Sulfonated carbon fiber accounts for 20 wt% of the total mass of oven-dry pulp fiber and sulfonated carbon fiber.

[0040] (4) Pour the mixed slurry obtained in step (3) into the defrosting machine and defrost it at 80,000 rpm. After defrosting, add it to the rapid Kaiser paper forming machine and form wet paper sheets with 4 L of water.

[0041] (5) Transfer the wet paper obtained in step (4) to a paper dryer and dry it at 105°C for 20 min to obtain the final lightweight, high-strength, high-efficiency green electromagnetic shielding functional paper (SCFP).

[0042] The test results of the SCFP prepared in Example 1 show that the electromagnetic shielding effectiveness in the X-band (8.2-12.4 GHz) reaches 52.8 dB, and the specific shielding effectiveness (SSE / t) can reach 5818.42 dB·cm. 2 ·g -1 It also possesses excellent tensile strength (19.9 MPa) and low density (0.2867 g / cm³). 3 ...

[0043] Comparative Example 1

[0044] Unlike Example 1, Comparative Example 1 did not undergo the sulfonation treatment in step (2).

[0045] (1) High freeness bleached eucalyptus pulp was obtained by pulping operation: 365 g of bleached eucalyptus pulp was soaked in 5 L of water for more than 4 hours to fully swell. After adding water to 18 L in the Wali pulper, pulp was slowly added and then subjected to 0.5 h of descaling and 1 h of pulping treatment to obtain 50°SR pulp with the required freeness.

[0046] (2) Add the high-freezing pulp obtained in step (1) and ordinary 3 mm chopped carbon fibers to water and stir to obtain a mixed pulp. The pulp content is 80 g / m³. 2 Carbon fiber accounts for 20 wt% of the total mass of oven-dry pulp fiber and carbon fiber.

[0047] (3) Pour the mixed slurry obtained in step (2) into the defrosting machine and defrost it at 80,000 rpm. After defrosting, add it to the rapid Kaiser paper forming machine and form wet paper sheets with 4 L of water.

[0048] (4) Transfer the wet paper obtained in step (3) to a paper dryer and dry it at 105°C for 20 minutes to obtain the final electromagnetic shielding functional paper (CFP).

[0049] The CFP prepared in Comparative Example 1 had a tensile strength of 11.2 MPa and a density of 0.4938 g / cm³. 3The electromagnetic shielding effectiveness in the X-band (8.2-12 GHz) reaches 23.4 dB, with a specific shielding effectiveness (SSE / t) of 2927.61 dB·cm. 2 ·g -1 .

[0050] Comparative Example 2

[0051] Different proportions of sulfonated carbon fiber were selected to verify the effect of the sulfonated carbon fiber ratio on SCFP. The steps are as follows:

[0052] (1) High freeness bleached eucalyptus pulp was obtained by pulping operation: 365 g of bleached eucalyptus pulp was soaked in 5 L of water for more than 4 hours to fully swell. After adding water to 18 L in the Wali pulper, pulp was slowly added and then subjected to 0.5 h of descaling and 1 h of pulping treatment to obtain 50°SR pulp with the required freeness.

[0053] (2) Add 5 g of 3 mm short carbon fiber to 300 mL of 98% concentrated sulfuric acid solution, stir in a water bath at 80°C for 1 h, then filter using a sand core funnel, and wash repeatedly with water and dilute sodium bicarbonate solution until the carbon fiber is neutral to obtain sulfonated carbon fiber.

[0054] (3) Add the high-freezing pulp obtained in step (1) and the sulfonated carbon fiber obtained in step (2) to water and stir to obtain a mixed pulp. The pulp content is 80 g / m³. 2 Sulfonated carbon fiber accounts for 10, 20, 30, and 40 wt% of the total mass of oven-dry pulp fiber and sulfonated carbon fiber, respectively.

[0055] (4) Pour the mixed slurry obtained in step (3) into the defrosting machine and defrost it at 80,000 rpm. After defrosting, add it to the rapid Kaiser paper forming machine and form wet paper sheets with 4 L of water.

[0056] (5) Transfer the wet paper obtained in step (4) to a paper dryer and dry it at 105°C for 20 min to obtain the final lightweight, high-strength, high-efficiency green electromagnetic shielding functional paper (SCFP).

[0057] Comparative Example 3

[0058] To verify the effect of paper basis weight on SCFP, different paper weights were selected. The steps are as follows:

[0059] (1) High freeness bleached eucalyptus pulp was obtained by pulping operation: 365 g of bleached eucalyptus pulp was soaked in 5 L of water for more than 4 hours to fully swell. After adding water to 18 L in the Wali pulper, pulp was slowly added and then subjected to 0.5 h of descaling and 1 h of pulping treatment to obtain 50°SR pulp with the required freeness.

[0060] (2) Add 5 g of 3 mm short carbon fiber to 300 mL of 98% concentrated sulfuric acid solution, stir in a water bath at 80°C for 1 h, then filter using a sand core funnel, and wash repeatedly with water and dilute sodium bicarbonate solution until the carbon fiber is neutral to obtain sulfonated carbon fiber.

[0061] (3) Add the high-freezing pulp obtained in step (1) and the sulfonated carbon fiber obtained in step (2) to water and stir to obtain a mixed pulp. The pulp composition is 80, 120, 160, 200, and 240 g / m³, respectively, according to the paper basis weight. 2 Sulfonated carbon fiber accounts for 20 wt% of the total mass of oven-dry pulp fiber and sulfonated carbon fiber.

[0062] (4) Pour the mixed slurry obtained in step (3) into the defrosting machine and defrost it at 80,000 rpm. After defrosting, add it to the rapid Kaiser paper forming machine and form wet paper sheets with 4 L of water.

[0063] (5) Transfer the wet paper obtained in step (4) to a paper dryer and dry it at 105°C for 20 min to obtain the final lightweight, high-strength, high-efficiency green electromagnetic shielding functional paper (SCFP).

[0064] Comparative Example 4

[0065] To verify the effect of paper basis weight on CFP, different paper weights were selected. The steps are as follows:

[0066] (1) High freeness bleached eucalyptus pulp was obtained by pulping operation: 365 g of bleached eucalyptus pulp was soaked in 5 L of water for more than 4 hours to fully swell. After adding water to 18 L in the Wali pulper, pulp was slowly added and then subjected to 0.5 h of descaling and 1 h of pulping treatment to obtain 50°SR pulp with the required freeness.

[0067] (2) Add the high-freezing pulp obtained in step (1) and ordinary 3 mm chopped carbon fibers to water and stir to obtain a mixed pulp. The pulp composition is 80, 120, 160, 200, and 240 g / m³. 2 Carbon fiber accounts for 20 wt% of the total mass of oven-dry pulp fiber and carbon fiber.

[0068] (3) Pour the mixed slurry obtained in step (2) into the defrosting machine and defrost it at 80,000 rpm. After defrosting, add it to the rapid Kaiser paper forming machine and form wet paper sheets with 4 L of water.

[0069] (4) Transfer the wet paper obtained in step (3) to a paper dryer and dry it at 105°C for 20 minutes to obtain the final electromagnetic shielding functional paper (CFP).

[0070] Experimental Analysis

[0071] The effect of sulfonated carbon fiber doping ratio on SCFP was investigated by comparing samples in Comparative Example 2 with different proportions of sulfonated carbon fiber. Figure 1 As shown in b, the tensile properties of the synthesized SCFP decrease continuously with the increase of sulfonated carbon fibers. This phenomenon can be explained by the fact that the increase of sulfonated carbon fibers reduces the bonding force of the fibers in the material, resulting in a weakening of the material strength. Figure 1 The term "e" indicates that the density of SCFP decreases with the increase of sulfonated carbon fiber, which can be attributed to the addition of sulfonated carbon fiber making the material more porous. Meanwhile, Figure 2 b、 Figure 2 As can be seen from e, with the increase of the proportion of sulfonated carbon fiber, the electromagnetic shielding effectiveness and specific shielding effectiveness of SCFP are continuously enhanced. This is because the continuous increase of conductive filler in the material leads to the stacking of the effective shielding components, thereby increasing the electromagnetic shielding effectiveness. At the same time, the increase in electromagnetic shielding effectiveness leads to the increase in specific shielding effectiveness.

[0072] from Figure 1 As can be seen from c, 1f, 2c, and 2f, as the basis weight of SCFP in Comparative Example 3 increases, the tensile strength of SCFP increases continuously, the density also gradually increases, and the electromagnetic shielding effectiveness also increases accordingly. However, the specific shielding effectiveness gradually decreases. This can be attributed to the fact that the increase in basis weight leads to an increase in the thickness and density of the material, which in turn leads to the structural strengthening of the material and the superposition of effectiveness. The decrease in specific shielding effectiveness is because the increase in the material's shielding effectiveness cannot keep up with the increase in the material's mass density, thus forming this phenomenon.

[0073] The effects of different CFP basis weights on the tensile properties, density, electromagnetic shielding effectiveness, and specific shielding effectiveness of CFPs were investigated by testing samples of proportion 4. The results are as follows: Figure 1 As shown in Figure a, the tensile strength of the material increases with increasing basis weight. This is mainly due to the fact that the paper density increases with increasing basis weight. Figure 1 d gradually increases, and the paper structure becomes more complete. Figure 2 As can be seen from a and 2d, as the paper weight increases, the electromagnetic shielding effectiveness of the material continuously increases, while the specific shielding effectiveness gradually decreases. This can be attributed to the fact that the increase in weight increases the thickness and density of the material, which leads to the structural strengthening of the material and the superposition of effectiveness. The decrease in specific shielding effectiveness is because the increase in the material's shielding effectiveness cannot keep up with the increase in the material's mass density, thus forming this phenomenon.

[0074] from Figure 1 , Figure 2In summary, it can be seen that, compared with Comparative Example 1, under the same conditions, Example 1 exhibits superior performance in all aspects. This is mainly due to the fact that sulfonated carbon fiber has more hydrophilic groups than carbon fiber, which allows it to better combine with pulp in paper-based materials and be uniformly dispersed in the paper-based materials.

[0075] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for the present invention. Further modifications can be readily implemented by those skilled in the art.

Claims

1. A method for preparing a lightweight, high-strength, high-efficiency, green electromagnetic shielding functional paper, characterized in that, Includes the following steps: Step (1): After soaking the bleached pulp in water until it is fully swollen, it is then decomposed and beaten to prepare high-freezing pulp; Step (2): Add 3mm short carbon fibers to concentrated sulfuric acid solution for sulfonation treatment. After washing until neutral, sulfonated carbon fibers are obtained. Step (3): Add the high-beating pulp obtained in step (1) and the sulfonated carbon fiber obtained in step (2) to water and stir to obtain a mixed slurry; Step (4): The mixed pulp obtained in step (3) is decomposed and wet papermaking is used to obtain wet paper sheets; Step (5): Dry the wet paper obtained in step (4) to obtain lightweight, high-strength, high-efficiency green electromagnetic shielding functional paper.

2. The preparation method according to claim 1, characterized in that, The bleached pulp is bleached eucalyptus pulp.

3. The preparation method according to claim 1, characterized in that, The high-beaten pulp has a beatness of 50°SR.

4. The preparation method according to claim 1, characterized in that, In step (2), the mass concentration of concentrated sulfuric acid is 98%, and the mass-volume ratio of 3 mm short-cut carbon fiber to concentrated sulfuric acid is 1 g: 60 mL.

5. The preparation method according to claim 1, characterized in that, The sulfonation treatment in step (2) is carried out at a temperature of 80°C for 1 hour.

6. The preparation method according to claim 1, characterized in that, In step (3), the paper basis weight is 80-240 g / m³. 2 Sulfonated carbon fiber accounts for 10-40 wt% of the total mass of oven-dry pulp fiber and sulfonated carbon fiber.

7. The preparation method according to claim 1, characterized in that, In step (5), the drying temperature is 105℃ and the time is 20min.

8. The preparation method according to claim 1, characterized in that, The density of the functional paper is 0.28674 g / cm³. 3 It has a tensile strength of 19.9 MPa, an electromagnetic shielding effectiveness of 52.8 dB in the X-band (8.2-12.4 GHz), and a specific shielding effectiveness (SSE / t) of 5818.42 dB·cm. 2 ·g -1 .

9. A lightweight, high-strength, high-efficiency, green electromagnetic shielding functional paper prepared by the preparation method according to any one of claims 1-7.

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