A flexible electromagnetic shielding material with heat conduction and sensing performance, and a preparation method and application thereof

Abstract

The application belongs to the technical field of electromagnetic shielding, and discloses a flexible electromagnetic shielding material with heat conduction and sensing performance, a preparation method and application thereof, and comprises the following steps: adding a polydopamine-coated silica dispersion liquid into a silver nanowire dispersion liquid, mixing through magnetic stirring to obtain a polydopamine-coated silica / silver nanowire dispersion liquid; mixing a nanocellulose dispersion liquid with the polydopamine-coated silica / silver nanowire dispersion liquid, performing ultrasonic treatment first, then adding glutaraldehyde, and performing mechanical stirring to obtain a polydopamine-coated silica / silver nanowire / nanocellulose dispersion liquid; performing vacuum filtration and drying treatment on the polydopamine-coated silica / silver nanowire / nanocellulose dispersion liquid to obtain the flexible electromagnetic shielding material with heat conduction and sensing performance; the application can realize efficient electromagnetic shielding, heat conduction and strain sensing, the preparation process is simple, economic and efficient, and the application has a good industrialization development prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electromagnetic shielding, and particularly relates to a flexible electromagnetic shielding material with heat conduction and sensing performance, and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of modern communication equipment, the adverse effects of electromagnetic radiation are increasingly prominent, such as interfering with information, interrupting communication, causing equipment failure, and even harming health. In recent years, the rapid popularization of flexible electronic products and portable devices has urgently required electromagnetic shielding materials to change from high shielding performance to lightweight and thin; in addition, heat will accumulate inside the equipment during operation, which will seriously affect the accuracy and service life of the equipment if the heat cannot be dissipated in time.

[0003] Currently, it is increasingly important for flexible electronic devices to have strain sensing capability, which not only can broaden the application range of flexible electronics in the fields of biological monitoring, wearable devices and intelligent skin, but also provides the possibility for real-time monitoring with high sensitivity and high reliability; however, the shielding effectiveness of existing electromagnetic shielding materials is generally low, and the high electromagnetic shielding performance of the material is incompatible with lightness, thinness, sensing and heat conduction performance, which cannot meet the application requirements of flexible electronic devices; therefore, it is urgent to develop electromagnetic shielding materials with high shielding, heat conduction and sensing performance. SUMMARY

[0004] In view of the technical problems in the prior art, the present application provides a flexible electromagnetic shielding material with heat conduction and sensing performance, and a preparation method and application thereof, to solve the technical problems that the shielding effectiveness of existing electromagnetic shielding materials is generally low, and the high electromagnetic shielding performance of the material is incompatible with lightness, thinness, sensing and heat conduction performance.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0006] The present application provides a preparation method of a flexible electromagnetic shielding material with heat conduction and sensing performance, comprising:

[0007] The polydopamine-coated silica dispersion liquid is added to the silver nanowire dispersion liquid, and mixed by magnetic stirring, so that the polydopamine-coated silica is combined with the silver nanowire through chelation to obtain a polydopamine-coated silica / silver nanowire dispersion liquid;

[0008] After the nanocellulose dispersion liquid and the polydopamine-coated silica / silver nanowire dispersion liquid are mixed, ultrasonic treatment is first performed, and then glutaraldehyde is added, so that the glutaraldehyde reacts with the amino groups of the polydopamine and the hydroxyl groups of the nanocellulose to form Schiff base bonds, and then mechanical stirring is performed to obtain a polydopamine-coated silica / silver nanowire / nanocellulose dispersion liquid;

[0009] The polydopamine-coated silica / silver nanowire / nanocellulose dispersion liquid is subjected to vacuum filtration and drying treatment to obtain the flexible electromagnetic shielding material with heat conduction and sensing performance.

[0010] Further, the preparation process of the polydopamine-coated silica dispersion liquid is as follows:

[0011] The silica dispersion liquid and the dopamine dispersion liquid are mixed and subjected to magnetic stirring treatment, a coating layer is formed on the surface of the silica through the self-polymerization reaction of dopamine to obtain the polydopamine-coated silica dispersion liquid.

[0012] Further, the preparation process of the silver nanowire dispersion liquid is as follows:

[0013] Silver nitrate is dissolved in ethylene glycol to obtain solution A;

[0014] Polyvinylpyrrolidone and ferric chloride hexahydrate are dissolved in ethylene glycol to obtain solution B;

[0015] The solution B is uniformly mixed with the solution A and then subjected to reaction, after the reaction, impurities are removed through centrifugation to obtain the silver nanowire dispersion liquid.

[0016] Further, after the polydopamine-coated silica dispersion liquid is added into the silver nanowire dispersion liquid, a mixed system b is formed; the solid phase composition in the mixed system b includes: 42wt%-78wt% of polydopamine-coated silica and 22wt%-58wt% of silver nanowire.

[0017] Further, after the nanocellulose dispersion liquid is mixed with the polydopamine-coated silica / silver nanowire dispersion liquid and glutaraldehyde is added, a mixed system c is formed; the solid phase composition in the mixed system c includes: 21.5wt%-44.5wt% of nanocellulose, 55wt%-76wt% of polydopamine-coated silica / silver nanowire and 0.5wt%-2.5wt% of glutaraldehyde.

[0018] Further, during the ultrasonic treatment, the ultrasonic power is 300-700W and the ultrasonic time is 5-25min.

[0019] Further, during the mechanical stirring, the stirring speed is 200-600rpm and the stirring time is 30-150min.

[0020] The application further provides the flexible electromagnetic shielding material with heat conduction and sensing performance, which is prepared from the flexible electromagnetic shielding material with heat conduction and sensing performance.

[0021] Further, the absolute electromagnetic shielding effectiveness of the flexible electromagnetic shielding material with heat conduction and sensing performance is 13277.5-15303.1 dB·cm 2 ·g -1 .

[0022] The application further provides an application of the flexible electromagnetic shielding material with heat conduction and sensing performance, which is applied to a flexible electronic device.

[0023] Compared with the prior art, the application has the following beneficial effects:

[0024] The preparation method of the flexible electromagnetic shielding material with heat conduction and sensing performance provided by the application combines polydopamine-coated silicon dioxide and silver nanowires through chelation, constructs a firm "cocoa tree" structure by using the metal chelation of polydopamine, and obtains a polydopamine-coated silicon dioxide / silver nanowire dispersion liquid with a "cocoa tree" structure; secondly, a Schiff base bond is formed by the reaction of glutaraldehyde with the amino groups of polydopamine and the hydroxyl groups of nanocellulose, so as to enhance the interaction; in addition, the nanocellulose is interwoven to form a stable network structure and construct a film with a similar "cocoa tree" structure, so as to realize the purposes of efficient electromagnetic shielding, heat conduction and strain sensing; the flexible electromagnetic shielding material prepared by the application meets the use requirements in portable intelligent electronic devices; compared with the existing electromagnetic shielding materials, the flexible electromagnetic shielding material has higher electromagnetic shielding performance, excellent heat conductivity and sensitive strain sensing performance, and provides favorable technical support for the commercialization of electromagnetic shielding materials; in addition, the preparation process of the flexible electromagnetic shielding material is simple, economical and efficient, and has a good industrial development prospect. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 A surface morphology diagram of the flexible electromagnetic shielding material with heat conduction and sensing performance prepared in Example 4;

[0026] Figure 2 A surface morphology diagram of the polydopamine-coated silicon dioxide / silver nanowire prepared in Example 4;

[0027] Figure 3 A flexible performance display diagram of the flexible electromagnetic shielding material with heat conduction and sensing performance prepared in Example 4;

[0028] Figure 4 An electromagnetic shielding effectiveness diagram of the flexible electromagnetic shielding material with heat conduction and sensing performance prepared in Examples 1-5;

[0029] Figure 5 A thermal conductivity coefficient diagram of the flexible electromagnetic shielding material with heat conduction and sensing performance prepared in Examples 1-5;

[0030] Figure 6 Current signal graph generated when writing on the flexible electromagnetic shielding material with heat conduction and sensing performance prepared in embodiment 4. DETAILED DESCRIPTION

[0031] In order to make the technical problems solved by the present application, the technical solutions and advantages clearer, the following specific embodiments are used to further illustrate the present application. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0032] The present application provides a preparation method of a flexible electromagnetic shielding material with heat conduction and sensing performance, comprising the following steps:

[0033] Step 1, mixing the silica dispersion liquid and dopamine dispersion liquid, and performing magnetic stirring treatment at a rotating speed of 200-600 rpm for 4-8 h, to form a coating layer on the surface of silica through the self-polymerization reaction of dopamine, to obtain a polydopamine-coated silica dispersion liquid; wherein, after mixing the silica dispersion liquid and dopamine dispersion liquid, a mixed system a is formed; the solid phase composition in the mixed system a includes: 40wt%-80wt% of silica and 20wt%-60wt% of dopamine.

[0034] Step 2, dissolving silver nitrate in ethylene glycol to obtain solution A; dissolving polyvinylpyrrolidone and ferric chloride hexahydrate in ethylene glycol to obtain solution B; mixing and stirring solution B and solution A uniformly, and then performing reaction, after the reaction is completed, removing impurities by centrifugation, to obtain the silver nanowire dispersion liquid.

[0035] Step 3, adding the polydopamine-coated silica dispersion liquid into the silver nanowire dispersion liquid, and mixing by magnetic stirring, to make the polydopamine-coated silica combine with the silver nanowire through chelation, to obtain a polydopamine-coated silica / silver nanowire dispersion liquid; wherein, after adding the polydopamine-coated silica dispersion liquid into the silver nanowire dispersion liquid, a mixed system b is formed; the solid phase composition in the mixed system b includes: 42wt%-78wt% of polydopamine-coated silica and 22wt%-58wt% of silver nanowire; the magnetic stirring rotating speed is 200-600 rpm, and the magnetic stirring time is 30-150 min.

[0036] Step 4, the nanocellulose dispersion liquid is dispersed and mixed with the polydopamine coated silica / silver nanowire, and ultrasonic treatment is carried out at 300-700W for 5-25min; then glutaraldehyde is added to make the glutaraldehyde and the amino groups of the polydopamine and the hydroxyl groups of the nanocellulose react to form Schiff base bonds; and then mechanical stirring is carried out at a rotating speed of 200-600rpm for 30-150min, to obtain a polydopamine coated silica / silver nanowire / nanocellulose dispersion liquid.

[0037] wherein after the nanocellulose dispersion liquid is dispersed and mixed with the polydopamine coated silica / silver nanowire and glutaraldehyde is added, a mixed system c is formed; the solid phase composition in the mixed system c includes: nanocellulose with a mass fraction of 21.5wt%-44.5wt%, polydopamine coated silica / silver nanowire with a mass fraction of 55wt%-76wt%, and glutaraldehyde with a mass fraction of 0.5wt%-2.5wt%.

[0038] Step 5, vacuum filtration and drying treatment are carried out on the polydopamine coated silica / silver nanowire / nanocellulose dispersion liquid, to obtain the flexible electromagnetic shielding material with heat conduction and sensing performance; wherein the drying temperature is 25-65℃ during the drying treatment.

[0039] Preparation principle:

[0040] The application provides a preparation method of a flexible electromagnetic shielding material with heat conduction and sensing performance,

[0041] The polydopamine-coated silica dispersion liquid is added to the silver nanowire dispersion liquid to enable the polydopamine-coated silica to be combined with the silver nanowire through chelation, and a firm "cocoa tree" structure is constructed by using the metal chelation of the polydopamine, so as to obtain a polydopamine-coated silica / silver nanowire dispersion liquid with a "cocoa tree" structure; wherein the silica particles are "cocoa fruits" in the "cocoa tree" structure, and the silver nanowire is "branches" in the "cocoa tree" structure; then, the nanocellulose dispersion liquid is mixed with the polydopamine-coated silica / silver nanowire dispersion liquid and is subjected to ultrasonic treatment, and then glutaraldehyde is added, so as to form a Schiff base bond through the reaction between the amino group of the glutaraldehyde and the hydroxyl group of the nanocellulose, thereby enhancing the interaction; in addition, the nanocellulose is interwoven to form a stable network structure and construct a film with a similar "cocoa tree" structure, so that a flexible electromagnetic shielding material with heat conduction and sensing performance is obtained; the "cocoa tree" structure constructed in the application has a complete conductive and heat conduction path, which effectively ensures the sensing and heat conduction performance of the material; at the same time, multiple components cause multiple interface polarizations to prolong the electromagnetic wave loss path and improve the electromagnetic shielding efficiency; secondly, the silica embedded in the "cocoa tree" structure can improve the impedance matching and provide good mechanical support for the silver nanowire conductive network; in summary, the flexible electromagnetic shielding material can realize the purposes of efficient electromagnetic shielding, heat conduction and strain sensing; the preparation process is simple, economical and efficient, and has good industrial development prospects.

[0042] Compared with the existing electromagnetic shielding materials, the flexible electromagnetic shielding material prepared in the application has higher electromagnetic shielding performance, excellent heat conductivity and sensitive strain sensing performance, meets the use requirements of electromagnetic shielding materials in portable intelligent electronic devices, and provides favorable technical support for the commercialization of electromagnetic shielding materials; wherein the absolute electromagnetic shielding efficiency of the flexible electromagnetic shielding material is 13277.5-15303.1 dB·cm 2 ·g -1 , the planar heat conductivity coefficient is 3.96-4.39 W / m·k, and the sensitive strain sensing performance is realized in a current range of -8*10 -11 ~26*10 -11 μA.

[0043] Example 1

[0044] The present embodiment 1 provides a preparation method of a flexible electromagnetic shielding material with heat conduction and sensing performance, comprising the following steps:

[0045] Step 1, the silica dispersion liquid and dopamine dispersion liquid are mixed in a magnetic stirrer, and magnetic stirring treatment is carried out at a rotating speed of 200 rpm for 4 h to obtain a polydopamine coated silica dispersion liquid; wherein, after mixing the silica dispersion liquid and dopamine dispersion liquid, a mixed system a is formed; the solid phase composition in the mixed system a includes 40wt% of silica and 60wt% of dopamine.

[0046] Step 2, silver nitrate is dissolved in ethylene glycol to obtain solution A; polyvinylpyrrolidone and ferric chloride hexahydrate are dissolved in ethylene glycol to obtain solution B; solution B is mixed with solution A and stirred uniformly, and then the reaction is carried out in an environment of 160℃; after the reaction is completed, impurities are removed by centrifugation to obtain the silver nanowire dispersion liquid.

[0047] Step 3, the polydopamine coated silica dispersion liquid is added to the silver nanowire dispersion liquid, and mixed by magnetic stirring, so that the polydopamine coated silica is combined with the silver nanowire through chelation to obtain a polydopamine coated silica / silver nanowire dispersion liquid; wherein, after the polydopamine coated silica dispersion liquid is added to the silver nanowire dispersion liquid, a mixed system b is formed; the solid phase composition in the mixed system b includes 42wt% of polydopamine coated silica and 58wt% of silver nanowire; the magnetic stirring speed is 200 rpm, and the magnetic stirring time is 30 min.

[0048] Step 4, the nanocellulose dispersion liquid is mixed with the polydopamine coated silica / silver nanowire dispersion liquid, first ultrasonic treatment is carried out at an ultrasonic power of 300 W for 5 min; then glutaraldehyde is added to make the glutaraldehyde react with the amino groups of the polydopamine and the hydroxyl groups of the nanocellulose to form Schiff base bonds; and then mechanical stirring is carried out at a rotating speed of 200 rpm for 30 min to obtain a polydopamine coated silica / silver nanowire / nanocellulose dispersion liquid.

[0049] Wherein, after the nanocellulose dispersion liquid is mixed with the polydopamine coated silica / silver nanowire dispersion liquid and glutaraldehyde is added, a mixed system c is formed; the solid phase composition in the mixed system c includes 44.5wt% of nanocellulose, 55wt% of polydopamine coated silica / silver nanowire, and 0.5wt% of glutaraldehyde.

[0050] Step 5, the polydopamine coated silica / silver nanowire / nanocellulose dispersion liquid is subjected to vacuum filtration and drying treatment to obtain the flexible electromagnetic shielding material with heat conduction and sensing performance; wherein, during the drying treatment, the drying temperature is 25℃.

[0051] Example 2

[0052] The embodiment 2 provides a preparation method of a flexible electromagnetic shielding material with heat conduction and sensing performance, comprising the following steps:

[0053] Step 1, the silica dispersion liquid and dopamine dispersion liquid are added into a magnetic stirrer for mixing, and magnetic stirring treatment is carried out at a rotating speed of 300 rpm for 5 h to obtain a polydopamine coated silica dispersion liquid; wherein, after the silica dispersion liquid and the dopamine dispersion liquid are mixed, a mixed system a is formed; the solid phase composition in the mixed system a comprises 50wt% of silica and 50wt% of dopamine.

[0054] Step 2, a silver nanowire dispersion liquid is prepared; the preparation method of the silver nanowire dispersion liquid is exactly the same as the process of step 2 in the above embodiment 1, and details are not repeated here.

[0055] Step 3, the polydopamine coated silica dispersion liquid is added into the silver nanowire dispersion liquid, and mixed by magnetic stirring, so that the polydopamine coated silica is combined with the silver nanowire through chelation to obtain a polydopamine coated silica / silver nanowire dispersion liquid; wherein, after the polydopamine coated silica dispersion liquid is added into the silver nanowire dispersion liquid, a mixed system b is formed; the solid phase composition in the mixed system b comprises 59wt% of polydopamine coated silica and 41wt% of silver nanowire; the magnetic stirring rotating speed is 300 rpm, and the magnetic stirring time is 60 min.

[0056] Step 4, the nanocellulose dispersion liquid is mixed with the polydopamine coated silica / silver nanowire dispersion liquid, first ultrasonic treatment is carried out at an ultrasonic power of 400 W for 10 min; then glutaraldehyde is added to make the glutaraldehyde react with the amino groups of the polydopamine and the hydroxyl groups of the nanocellulose to form Schiff base bonds; and then mechanical stirring is carried out at a rotating speed of 300 rpm for 60 min to obtain a polydopamine coated silica / silver nanowire / nanocellulose dispersion liquid.

[0057] Wherein, after the nanocellulose dispersion liquid is mixed with the polydopamine coated silica / silver nanowire dispersion liquid and glutaraldehyde is added, a mixed system c is formed; the solid phase composition in the mixed system c comprises 36wt% of nanocellulose, 63wt% of polydopamine coated silica / silver nanowire and 1.0wt% of glutaraldehyde.

[0058] Step 5, the polydopamine coated silica / silver nanowire / nanocellulose dispersion liquid is subjected to vacuum filtration and drying treatment to obtain the flexible electromagnetic shielding material with heat conduction and sensing performance; wherein, during the drying treatment, the drying temperature is 35℃.

[0059] Embodiment 3

[0060] The embodiment 3 provides a preparation method of a flexible electromagnetic shielding material with heat conduction and sensing performance, comprising the following steps:

[0061] Step 1, the silica dispersion liquid and dopamine dispersion liquid are added into a magnetic stirrer for mixing, and magnetic stirring treatment is carried out at a rotating speed of 400 rpm for 6 h to obtain a polydopamine coated silica dispersion liquid; wherein, after the silica dispersion liquid and the dopamine dispersion liquid are mixed, a mixed system a is formed; the solid phase composition in the mixed system a comprises 60wt% of silica and 40wt% of dopamine.

[0062] Step 2, a silver nanowire dispersion liquid is prepared; the preparation method of the silver nanowire dispersion liquid is exactly the same as the process of step 2 in the above embodiment 1, and details are not repeated here.

[0063] Step 3, the polydopamine coated silica dispersion liquid is added into the silver nanowire dispersion liquid, and mixed by magnetic stirring, so that the polydopamine coated silica is combined with the silver nanowire through chelation to obtain a polydopamine coated silica / silver nanowire dispersion liquid; wherein, after the polydopamine coated silica dispersion liquid is added into the silver nanowire dispersion liquid, a mixed system b is formed; the solid phase composition in the mixed system b comprises 68wt% of polydopamine coated silica and 32wt% of silver nanowire; the magnetic stirring rotating speed is 400 rpm, and the magnetic stirring time is 90 min.

[0064] Step 4, the nanocellulose dispersion liquid is mixed with the polydopamine coated silica / silver nanowire dispersion liquid, first ultrasonic treatment is carried out at an ultrasonic power of 500 W for 15 min; then glutaraldehyde is added to make the glutaraldehyde react with the amino groups of the polydopamine and the hydroxyl groups of the nanocellulose to form Schiff base bonds; and then mechanical stirring is carried out at a rotating speed of 400 rpm for 90 min to obtain a polydopamine coated silica / silver nanowire / nanocellulose dispersion liquid.

[0065] Wherein, after the nanocellulose dispersion liquid is mixed with the polydopamine coated silica / silver nanowire dispersion liquid and glutaraldehyde is added, a mixed system c is formed; the solid phase composition in the mixed system c comprises 29.5wt% of nanocellulose, 69wt% of polydopamine coated silica / silver nanowire and 1.5wt% of glutaraldehyde.

[0066] Step 5, the polydopamine coated silica / silver nanowire / nanocellulose dispersion liquid is subjected to vacuum filtration and drying treatment to obtain the flexible electromagnetic shielding material with heat conduction and sensing performance; wherein, during the drying treatment, the drying temperature is 45 DEG C.

[0067] Example 4

[0068] The present example 4 provides a preparation method of a flexible electromagnetic shielding material with both heat conduction and sensing performance, comprising the following steps:

[0069] Step 1, the silica dispersion liquid and dopamine dispersion liquid are added into a magnetic stirrer for mixing, and magnetic stirring treatment is carried out at a speed of 500 rpm for 7 h to obtain a polydopamine coated silica dispersion liquid; wherein, after mixing the silica dispersion liquid and dopamine dispersion liquid, a mixed system a is formed; the solid phase composition in the mixed system a includes: 70wt% of silica and 30wt% of dopamine.

[0070] Step 2, a silver nanowire dispersion liquid is prepared; the preparation method of the silver nanowire dispersion liquid is exactly the same as the process of step 2 in the above example 1, which will not be repeated here.

[0071] Step 3, the polydopamine coated silica dispersion liquid is added into the silver nanowire dispersion liquid for mixing by magnetic stirring, so that the polydopamine coated silica is combined with the silver nanowire through chelation to obtain a polydopamine coated silica / silver nanowire dispersion liquid; wherein, after the polydopamine coated silica dispersion liquid is added into the silver nanowire dispersion liquid, a mixed system b is formed; the solid phase composition in the mixed system b includes: 74wt% of polydopamine coated silica and 26wt% of silver nanowire; the magnetic stirring speed is 500 rpm, and the magnetic stirring time is 120 min.

[0072] Step 4, the nanocellulose dispersion liquid is mixed with the polydopamine coated silica / silver nanowire dispersion liquid, first ultrasonic treatment is carried out at a power of 600 W for 20 min; then glutaraldehyde is added to make the glutaraldehyde react with the amino groups of the polydopamine and the hydroxyl groups of the nanocellulose to form Schiff base bonds; after that, mechanical stirring is carried out at a speed of 500 rpm for 120 min to obtain a polydopamine coated silica / silver nanowire / nanocellulose dispersion liquid.

[0073] Wherein, after the nanocellulose dispersion liquid is mixed with the polydopamine coated silica / silver nanowire dispersion liquid and glutaraldehyde is added, a mixed system c is formed; the solid phase composition in the mixed system c includes: 25wt% of nanocellulose, 73wt% of polydopamine coated silica / silver nanowire, and 2.0wt% of glutaraldehyde.

[0074] Step 5, vacuum filtration and drying treatment are performed on the polydopamine-coated silica / silver nanowire / nanocellulose dispersion liquid to obtain the flexible electromagnetic shielding material with heat conduction and sensing performance; wherein, during the drying treatment, the drying temperature is 55°C.

[0075] Example 5

[0076] The present example 5 provides a preparation method of a flexible electromagnetic shielding material with heat conduction and sensing performance, comprising the following steps:

[0077] Step 1, the silica dispersion liquid and the dopamine dispersion liquid are added into a magnetic stirrer for mixing, and magnetic stirring treatment is performed at a rotation speed of 600 rpm for 8 h to obtain a polydopamine-coated silica dispersion liquid; wherein, after the silica dispersion liquid and the dopamine dispersion liquid are mixed, a mixed system a is formed; the solid phase composition in the mixed system a includes: 80wt% of silica and 20wt% of dopamine.

[0078] Step 2, a silver nanowire dispersion liquid is prepared; the preparation method of the silver nanowire dispersion liquid is exactly the same as the process of step 2 in the above example 1, which will not be repeated here.

[0079] Step 3, the polydopamine-coated silica dispersion liquid is added into the silver nanowire dispersion liquid, and mixed by magnetic stirring, so that the polydopamine-coated silica is combined with the silver nanowire through chelation to obtain a polydopamine-coated silica / silver nanowire dispersion liquid; wherein, after the polydopamine-coated silica dispersion liquid is added into the silver nanowire dispersion liquid, a mixed system b is formed; the solid phase composition in the mixed system b includes: 78wt% of polydopamine-coated silica and 22wt% of silver nanowire; the magnetic stirring rotation speed is 600 rpm, and the magnetic stirring time is 150 min.

[0080] Step 4, the nanocellulose dispersion liquid is mixed with the polydopamine-coated silica / silver nanowire dispersion liquid, first ultrasonic treatment is performed at an ultrasonic power of 700 W for 25 min; then glutaraldehyde is added to make the glutaraldehyde react with the amino groups of the polydopamine and the hydroxyl groups of the nanocellulose to form Schiff base bonds; and then mechanical stirring is performed at a rotation speed of 600 rpm for 150 min to obtain a polydopamine-coated silica / silver nanowire / nanocellulose dispersion liquid.

[0081] Wherein, after the nanocellulose dispersion liquid is mixed with the polydopamine-coated silica / silver nanowire dispersion liquid and glutaraldehyde is added, a mixed system c is formed; the solid phase composition in the mixed system c includes: 21.5wt% of nanocellulose, 76wt% of polydopamine-coated silica / silver nanowire, and 2.5wt% of glutaraldehyde.

[0082] Step 5, vacuum filtration and drying treatment are performed on the polydopamine-coated silica / silver nanowire / nanocellulose dispersion liquid to obtain the flexible electromagnetic shielding material with heat conduction and sensing performance; wherein, during the drying treatment, the drying temperature is 65°C.

[0083] As shown in the accompanying Figure 1 , the surface morphology of the flexible electromagnetic shielding material with heat conduction and sensing performance prepared in Example 4 is given in the accompanying Figure 1 ; it can be seen from the accompanying Figure 1 that the flexible electromagnetic shielding material prepared in Example 4 has the phenomenon of interweaving of polydopamine-coated silica / silver nanowires in nanocellulose, and utilizes the nanocellulose network to disperse the polydopamine-coated silica / silver nanowires, forming uniform conductive and heat conduction paths, which is conducive to the improvement of electromagnetic shielding efficiency.

[0084] As shown in the accompanying Figure 2 , the surface morphology of the polydopamine-coated silica / silver nanowires prepared in Example 4 is given in the accompanying Figure 2 ; it can be seen from the accompanying Figure 2 that the prepared polydopamine-coated silica / silver nanowires have the phenomenon of silica particles adhering to the surface of silver nanowires, forming a structure similar to a “cocoa tree”, which can effectively improve the electromagnetic shielding efficiency by combining the electric conduction loss, polarization loss and internal multiple scattering and scattering.

[0085] As shown in the accompanying Figure 3 , the flexibility performance display of the flexible electromagnetic shielding material with heat conduction and sensing performance prepared in Example 4 is given in the accompanying Figure 3 ; it can be seen from the accompanying Figure 3 that the flexible electromagnetic shielding material prepared in Example 4 has good flexibility.

[0086] As shown in the accompanying Figure 4 , the electromagnetic shielding efficiency of the flexible electromagnetic shielding material with heat conduction and sensing performance prepared in Examples 1-5 is given in the accompanying Figure 4 ; it can be seen from the accompanying Figure 4 that the flexible electromagnetic shielding materials prepared in Examples 1-5 all have excellent electromagnetic shielding performance; specifically, when the thickness of the flexible electromagnetic shielding material prepared in Example 1 is 71 μm, the material electromagnetic shielding efficiency reaches 67.74 dB, and the calculated absolute electromagnetic shielding efficiency is 14189.6 dB·cm 2 ·g -1 ; when the thickness of the flexible electromagnetic shielding material prepared in Example 2 is 67 μm, the material electromagnetic shielding efficiency reaches 70.67 dB, and the calculated absolute electromagnetic shielding efficiency is 13609.5 dB·cm2 ·g -1 When the thickness of the flexible electromagnetic shielding material prepared in Example 3 is 63 μm, the electromagnetic shielding effectiveness reaches 74.05 dB, and its absolute electromagnetic shielding effectiveness is calculated to be 14494.2 dB·cm. 2 ·g -1 When the thickness of the flexible electromagnetic shielding material prepared in Example 4 is 59 μm, the electromagnetic shielding effectiveness reaches 76.91 dB, and its absolute electromagnetic shielding effectiveness is calculated to be 15303.1 dB·cm. 2 ·g -1 When the thickness of the flexible electromagnetic shielding material prepared in Example 5 is 54 μm, the electromagnetic shielding effectiveness reaches 71.17 dB, and its absolute electromagnetic shielding effectiveness is calculated to be 13277.5 dB·cm. 2 ·g -1 Therefore, it can be seen that the flexible electromagnetic shielding materials prepared in Examples 1-5 all meet the requirements of portable electronic devices for electromagnetic shielding materials to be thin, light and efficient.

[0087] As attached Figure 5 As shown, attached Figure 5 The appendix provides thermal conductivity diagrams for the flexible electromagnetic shielding materials with both thermal conductivity and sensing properties prepared in Examples 1-5; from the appendix... Figure 5 As can be seen, the planar thermal conductivity of the flexible electromagnetic shielding material prepared in Example 1 reaches 4.39 W / (m·k), the planar thermal conductivity of the flexible electromagnetic shielding material prepared in Example 2 reaches 4.31 W / (m·k), the planar thermal conductivity of the flexible electromagnetic shielding material prepared in Example 3 reaches 4.24 W / (m·k), the planar thermal conductivity of the flexible electromagnetic shielding material prepared in Example 4 reaches 4.15 W / (m·k), and the planar thermal conductivity of the flexible electromagnetic shielding material prepared in Example 5 reaches 4.39 W / (m·k). All of these materials can quickly transfer heat and improve the thermal management capability of electronic devices.

[0088] As attached Figure 6 As shown, attached Figure 6 The figure shows the current signal generated when writing the flexible electromagnetic shielding material with both thermal conductivity and sensing properties prepared in Example 4; specifically, Figure A is the current signal generated when writing the letter A, Figure B is the current signal generated when writing the letter B, and Figure C is the current signal generated when writing the letter C.

[0089] From the appendix Figure 6As can be seen, the prepared flexible electromagnetic shielding material changes the corresponding current signal when the local strain changes, and the generated electric signal remains basically consistent when the same letter is repeatedly written; when different letters are written, different external stresses are received, and different changes are shown; thus, the flexible electromagnetic shielding material prepared in Example 5 has high sensitivity and stable strain sensing performance, and has great application value in the fields of flexible electronics and medical health.

[0090] The present application aims at the problem that the existing electromagnetic shielding materials are light and thin, have high electromagnetic shielding efficiency, and do not consider sensing and heat conduction performance, and uses the metal chelation of polydopamine to construct a firm "cocoa tree" structure - polydopamine coated silica / silver nanowire, crosslink the nanocellulose with glutaraldehyde, and form a stable network structure to form an electromagnetic shielding film with a similar "cocoa tree" structure; the "cocoa tree" structure is constructed to improve impedance matching, prolong the electromagnetic wave loss path, form a "resistor-capacitor circuit", cause multiple interface polarization, and produce polarization loss; at the same time, complete conductive and heat conduction paths are formed to realize a multifunctional electromagnetic shielding film with high efficient electromagnetic shielding, heat conduction and strain sensing, and provide a new strategy for the research and development of high performance and multifunctional integrated new electromagnetic shielding materials.

[0091] The electromagnetic shielding efficiency of the flexible electromagnetic shielding material prepared in the present application is 76.91 dB, the planar heat conduction coefficient is 4.15 W / (m·k), the current signal changes correspondingly when different letters are written, has high sensitivity and stable strain sensing performance, realizes light and thin, high electromagnetic shielding efficiency, excellent heat conduction performance and sensitive sensing performance, the preparation process is simple and safe, and has the potential and technical feasibility of industrial scale production.

[0092] The above examples are only one of the implementation manners of the technical solutions of the present application, and the scope of protection of the present application is not limited to the above examples, but also includes any changes, substitutions and other implementation manners easily thought by those skilled in the art within the technical scope disclosed in the present application.

Claims

1. A method for preparing a flexible electromagnetic shielding material with both thermal conductivity and sensing properties, characterized in that, include: A polydopamine-coated silica dispersion was added to a silver nanowire dispersion and mixed by magnetic stirring so that the polydopamine-coated silica could bind to the silver nanowires through chelation, thus obtaining a polydopamine-coated silica / silver nanowire dispersion. After dispersing and mixing the nanocellulose dispersion with polydopamine-coated silica / silver nanowires, the mixture was first subjected to ultrasonic treatment, and then glutaraldehyde was added to allow the glutaraldehyde to react with the amino groups of polydopamine and the hydroxyl groups of nanocellulose to form Schiff base bonds. After mechanical stirring, the polydopamine-coated silica / silver nanowires / nanocellulose dispersion was obtained. The polydopamine-coated silica / silver nanowire / cellulose nanofiber dispersion was subjected to vacuum filtration and drying to obtain the flexible electromagnetic shielding material with both thermal conductivity and sensing properties. The preparation process of the silver nanowire dispersion is as follows: Silver nitrate was dissolved in ethylene glycol to obtain solution A; Polyvinylpyrrolidone and ferric chloride hexahydrate were dissolved in ethylene glycol to obtain solution B; Solution B and solution A were mixed and stirred until homogeneous before being reacted. After the reaction was completed, the silver nanowire dispersion was obtained by centrifugation to remove impurities.

2. The method for preparing a flexible electromagnetic shielding material with both thermal conductivity and sensing properties according to claim 1, characterized in that, The preparation process of polydopamine-coated silica dispersion is as follows: A silica dispersion and a dopamine dispersion were mixed and magnetically stirred. The dopamine self-polymerization reaction formed a coating layer on the silica surface, resulting in a polydopamine-coated silica dispersion.

3. The method for preparing a flexible electromagnetic shielding material with both thermal conductivity and sensing properties according to claim 1, characterized in that, After adding the polydopamine-coated silica dispersion to the silver nanowire dispersion, a mixed system b is formed; the solid phase composition of the mixed system b includes: polydopamine-coated silica with a mass fraction of 42wt%-78wt% and silver nanowires with a mass fraction of 22wt%-58wt%.

4. The method for preparing a flexible electromagnetic shielding material with both thermal conductivity and sensing properties according to claim 1, characterized in that, A nanocellulose dispersion was dispersed and mixed with polydopamine-coated silica / silver nanowires, and glutaraldehyde was added to form a mixed system c. The solid phase composition of the mixed system c includes: nanocellulose with a mass fraction of 21.5wt%-44.5wt%, polydopamine-coated silica / silver nanowires with a mass fraction of 55wt%-76wt%, and glutaraldehyde with a mass fraction of 0.5wt%-2.5wt%.

5. The method for preparing a flexible electromagnetic shielding material with both thermal conductivity and sensing properties according to claim 1, characterized in that, During ultrasonic treatment, the ultrasonic power is 300-700W and the ultrasonic time is 5-25min.

6. The method for preparing a flexible electromagnetic shielding material with both thermal conductivity and sensing properties according to claim 1, characterized in that, The mechanical stirring process involves a stirring speed of 200-600 rpm and a stirring time of 30-150 min.

7. A flexible electromagnetic shielding material possessing both thermal conductivity and sensing properties, characterized in that, The flexible electromagnetic shielding material with both thermal conductivity and sensing properties is prepared using any one of the flexible electromagnetic shielding materials with both thermal conductivity and sensing properties as described in any one of claims 1-6.

8. A flexible electromagnetic shielding material with both thermal conductivity and sensing properties according to claim 7, characterized in that, The absolute electromagnetic shielding effectiveness of the flexible electromagnetic shielding material, which combines thermal conductivity and sensing properties, is 13277.5-15303.1 dB·cm. 2 ·g -1 .

9. The application of a flexible electromagnetic shielding material with both thermal conductivity and sensing properties as described in claim 7 or 8, characterized in that, The flexible electromagnetic shielding material, which combines thermal conductivity and sensing properties, is used in flexible electronic devices.

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