A template transfer imprinting pre-filled filler loaded network high thermal conductivity composite film and a preparation method thereof

Abstract

The application discloses a template transfer imprint prefabricated filler loaded network high-thermal-conductivity composite film and a preparation method thereof. The composite film is made by hot calendering of a single-layer or multi-layer film loaded with a thermal-conductivity filler, and the film matrix is hot-pressed and transferred by a template with a matrix array to form an imprint network structure. The thermal-conductivity filler is at least one of zero-dimensional, one-dimensional, two-dimensional or special-shaped thermal-conductivity fillers. The 3D continuous network is formed by artificially designing the polymer surface microstructure through the template transfer method, and then the nano filler is loaded in the imprint network space. This method can realize specific spatial loading of the thermal-conductivity filler and optimization of the dense and continuous filler network, thereby forming a better thermal-conductivity path and improving the thermal-conductivity performance. The composite film solves the problems of the thermal-conductivity filler in the conventional filling preparation method, such as too dispersed network construction, incoherent performance and difficult effective improvement, and has the advantages of excellent thermal-conductivity performance improvement effect, simple preparation process, easy realization of large-scale production and great development potential in large-scale production of the thermal-conductivity composite film.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat-conducting composite films, and particularly relates to a template transfer imprint preform filler loading network high-heat-conducting composite film and a preparation method thereof. BACKGROUND

[0002] With the continuous miniaturization and integration of electronic device equipment, electronic equipment is facing urgent heat management problems, and needs heat-conducting composite materials with rapid heat dissipation, low thermal expansion, corrosion resistance, light weight, and good mechanical properties. At present, most heat-conducting polymer composites directly introduce high-heat-conducting ceramic, carbon-based, metal and other fillers into a low-heat-conducting polymer matrix. In order to achieve a percolation value, a large amount of filler needs to be filled, which leads to problems such as high cost, poor mechanical properties, and difficult processing of the composite material. At present, researchers at home and abroad mainly focus on the research theme of "constructing a high-efficiency heat-conducting path in a filler network in a polymer matrix", and explore from the aspects of filler orientation and arrangement, three-dimensional heat-conducting network construction, and composite film preparation process optimization.

[0003] For traditional filled polymer-based heat-conducting composites, excessive dispersion or poor contact between fillers in the composite material and interface defects between the filler and the matrix will lead to incomplete heat-conducting networks, thereby causing poor heat-conducting performance improvement of the composite material. Therefore, the key to improving the heat-conducting performance of the composite material lies in reasonable structural design to effectively play the synergistic effect between the matrix and the filler, construction of a special filler spatial distribution form, and formation of a high-efficiency and continuous three-dimensional (3D) filler network. SUMMARY

[0004] The present application aims to solve the problems of deterioration of performance caused by simple filler doping in the preparation process of the existing heat-conducting composite material, and difficulty in improving the in-plane heat-conducting coefficient due to the discontinuous heat-conducting network, and provides a template transfer imprint preform filler loading network high-heat-conducting composite film and a preparation method thereof. The prepared film can artificially design the matrix surface through template transfer to form a dense and continuous imprint network. After loading the filler, the highly continuous filler network provides a favorable path for rapid heat-conducting transmission. This method can maximize the function with the minimum filler loading, and is one of the best ways to obtain a high heat-conducting coefficient with low filler loading. It forms an excellent and continuous heat-conducting path without affecting the mechanical properties of the composite film. In addition, this method can increase the contact between the fillers and reduce the interfacial thermal resistance between the fillers and the matrix and the contact thermal resistance between the fillers as much as possible, and has the advantages of efficient improvement of heat-conducting performance, simple preparation process, easy realization of large-scale production, and wide development prospects in thermal interface materials.

[0005] The technical scheme of the present application is as follows:

[0006] A template transfer imprint pre-filler loaded network high thermal conductivity composite film, the composite film is formed by a single layer or multiple layers of polymer film layer through a template hot pressing transfer to form an imprint space network structure with a matrix array, then loading a thermal conductive filler on the surface, and finally passing through hot calendering; the thermal conductive filler is at least one of zero-dimensional thermal conductive filler, one-dimensional thermal conductive filler, two-dimensional thermal conductive filler or special-shaped thermal conductive filler.

[0007] The polymer film layer is a film prepared from polylactic acid PLA, polyvinyl alcohol PVA, thermoplastic polyurethane TPU, polyurethane PU, polyvinylidene fluoride PVDF, polyolefin POE material; or is one of non-woven fabric, woven fabric, fiber felt, carbon fiber cloth, the fiber diameter is 50 nm-50 μm, and the area density is 10-30 g / m 2 .

[0008] The zero-dimensional thermal conductive filler is at least one of spherical ferric oxide Fe3O4, spherical aluminum oxide Al2O3 and spherical aluminum nitride AlN, and the particle size is 500 nm-100 μm.

[0009] The one-dimensional thermal conductive filler is at least one of carbon nanotube CNTs, carbon nitride nanotube CNNTs, silicon carbide nanowire SiCNWs and silver nanowire AgNWs, and the length is 10 μm-200 μm.

[0010] The two-dimensional thermal conductive filler is at least one of boron nitride nanosheet BNNs, graphene nanosheet GNPs and MXene, the particle size is 100 nm-5 μm, and the thickness is 5 nm-800 nm.

[0011] The special-shaped thermal conductive filler is at least one of core-shell structure Al2O3@BN and core-shell structure Fe3O4@CNTs, and the particle size is 500 nm-100 μm.

[0012] The thermal conductive filler is loaded in the imprint space network structure after hot pressing transfer by means of cyclic infiltration adsorption, electrostatic spraying, blade coating, casting and 3D printing injection.

[0013] A preparation method of a template transfer imprint pre-filler loaded network high thermal conductivity composite film, comprising the following steps:

[0014] 1) preparing a polymer film layer by electrospinning, blade coating and spin coating process;

[0015] 2) After the polymer film layers prepared in step 1) are stacked in order, the film layers are subjected to template transfer hot calendering through a hot calendering device with a matrix grid, and a suitable specification of the matrix grid is selected to obtain a precision printed polymer film layer with a printed template template bar space diameter of 0.05-10 mm and a template matrix spacing of 0.1-20 mm;

[0016] 3) Different kinds of heat-conducting fillers are dispersed in a dispersant to obtain different heat-conducting filler dispersions;

[0017] 4) The heat-conducting fillers prepared in step 3) are loaded onto the polymer film layers obtained in step 2) to obtain a composite film layer containing one or more heat-conducting fillers; the total loading amount of the fillers is 5%-100% of the mass of the film;

[0018] 5) The film prepared in step 4) is subjected to hot calendering in a single layer or multiple layers to obtain a template transfer printed pre-filled network high-thermal-conductivity composite film.

[0019] In step 2), the template transfer hot calendering has a process temperature of 10-50 DEG C and a pressure of 1-20 MPa; in step 5), the hot calendering has a process temperature of 100-300 DEG C and a pressure of 1-30 MPa.

[0020] In step 4), the loading is performed by immersing the polymer film layer into one of the heat-conducting filler dispersions prepared in step 3), soaking and adsorbing for 10-30 s, drying, immersing into the same or other heat-conducting filler dispersion for 10-30 s, drying, and repeating the immersion for 1-5 times; or the filler loading is performed by spraying, casting, blade coating, 3D printing injection process.

[0021] The template transfer printed pre-filled network high-thermal-conductivity composite film and the preparation method thereof have the following advantages compared with the prior art.

[0022] (1) The composite film forms a printed template on the surface of the substrate through the action of a specific matrix template hot pressing transfer, thereby constructing a space channel, and allowing the fillers to be as densely and continuously loaded as possible in the space channel in a physical manner. The special filler space distribution form constructed not only forms an efficient and continuous heat-conducting network, but also ensures that too many new defects are not introduced into the composite film matrix, so that the mechanical properties are not deteriorated. The method improves the contact area between the heat-conducting fillers and improves the thermal conductivity of the composite film.

[0023] (2) The composite film can be prepared by scraping, spin coating, electrospinning and other processes, or carbon fiber cloth, non-woven fabric and other film materials can be selected, in addition, one or more heat-conducting fillers can be loaded by ultrasonic-assisted circulation immersion, scraping, spraying and other methods, which can improve the coherence of the filler network and achieve the idea of synergistic regulation of filler structure-space structure, and the reasonable selection of fillers can increase the multifunctional design of the composite film such as electromagnetic shielding.

[0024] (3) The selected film has different layers as the structure and is hot calendered so that the film contacts each other and further melts under the joint action of shear force and pressure, the heat-conducting filler loaded on the imprint space of the film surface can be more effectively contacted to construct a 3D coherent heat-conducting network and improve the heat dissipation effect. Compared with the film without template transfer, the composite film has a 10%-51.6% improvement in heat-conducting performance under the same filler content.

[0025] (4) The composite film has the characteristics of simple preparation process, low cost and excellent heat-conducting performance improvement, and is suitable for application as a thermal interface material in the field of electronic packaging. The preformed imprint network for filler loading has certain flexible processing and extensive functional design, and it is easier to design and assemble multiple filler networks in the composite film. This method has great potential in the continuous production of heat-conducting composite materials. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is the preparation process schematic diagram and related pictures of the composite film in Example 3.

[0027] Figure 2 It is the schematic diagram of the hot press transfer template in Example 3. DETAILED DESCRIPTION

[0028] The application will be further described through the following implementation cases, but it is not limited to the application.

[0029] Example 1

[0030] A preparation method of a template transfer imprint preformed filler-loaded network high-heat-conducting composite film, comprising the following steps:

[0031] (1) 3 g of PVDF powder is weighed by an electronic balance and dissolved in 30 mL of a mixed solvent of DMF and acetone (2:1), and magnetically stirred at room temperature for 3 h until fully dissolved, to prepare a PVDF electrospinning precursor solution. The solution is vacuumed and the operation is repeated three times to remove as much internal air bubbles as possible;

[0032] (2) Using a syringe to suck 10 mL of PVDF electrospinning solution for electrospinning, and the collection device is a cylindrical collector covered with aluminum foil; the electrospinning parameters are set as follows: voltage 15 kv, pushing speed 1 mL / h, solidification collection distance 12 cm, and the receiving speed of the cylindrical collector is 350 rpm; the electrospinning is carried out at 45°C, and the relative humidity of the environment is 20%-25% (RH);

[0033] (3) After electrospinning, the electrospun PVDF fiber membrane is gently peeled off from the aluminum foil, cut into a fiber membrane with a size of 10 cm x 10 cm, and dried at 60°C for 24 h to remove the unvolatilized solvent;

[0034] (4) A matrix template with different intervals is selected, and the electrospun fiber membrane is used as the bottom layer and the template as the surface layer in the hot press, and a certain pressure is used for hot pressing transfer printing, so as to achieve the purpose of prefilling the space network of the filler, and the hot pressing temperature is 30°C and the pressure is 10 MPa;

[0035] (5) The filler loading is carried out in the imprint network on the surface of the fiber membrane after pressure printing by using the infiltration adsorption process: the 10 cm x 10 cm prefilling network PVDF fiber membrane is immersed in a CNTs dispersion liquid with a concentration of 2 mg / ml, the solvent is deionized water, and after ultrasonic immersion adsorption for 2-3 min, it is placed in a 60°C oven for drying. This process is repeated to assemble nanoparticles, and the composite film is named CNT-x / PVDF, wherein x represents the adsorption times, and the same fiber membrane is selected without template transfer printing, and the same times are loaded as a control sample;

[0036] (6) The loaded fiber membrane is selected for hot pressing with a three-layer structure, and the hot pressing process parameters are as follows: temperature 200°C, pressure 15 MPa.

[0037] After the above steps, a template transfer imprint prefilling filler loading network high-thermal-conductivity composite film is prepared.

[0038] The prepared thermal-conductivity composite film is tested for thermal conductivity by using HOT DISK, and the in-plane thermal conductivity of the composite film is 1.91 W / mK, the in-plane thermal conductivity of the control sample without template hot pressing transfer printing is 1.41 W / mK, and the thermal conductivity performance improvement rate is 35.4%.

[0039] Example 2

[0040] A preparation method of a template transfer imprint prefilling filler loading network high-thermal-conductivity composite film, comprising the following steps:

[0041] (1) In 200 mL of a mixed solvent of isopropyl alcohol and deionized water (1:1), 2 g of BN powder was added, and ultrasonic treatment was performed for 4 h using a CJ-020 type ultrasonic cleaner at a frequency of 40 KHz. The unpeeled BN sheets were removed by centrifugation at 1000 rpm for 20 min using a tgl-15b type super centrifuge, and the supernatant was collected. Then, the BNNS was collected by centrifugation at 9000 rpm for 30 min;

[0042] (2) 0.5 g of the BNNS peeled in step one was weighed and added to 100 ml of a mixed solution of deionized water and anhydrous ethanol at a ratio of 1:1. After stirring, ultrasonic dispersion was performed for 2 h using an ultrasonic cleaner to obtain a BNNS dispersion liquid with a concentration of 5 mg / ml;

[0043] (3) Different space interval matrix templates were selected, and a pre-cut 10 cm x 10 cm size non-woven fabric (PET) was used as the bottom layer, and the template was used as the surface layer. A certain pressure was used for hot pressing transfer printing, and the matrix was pressed to achieve the purpose of preloading the filler network. The hot pressing temperature was 80°C, and the pressure was 20 MPa;

[0044] (4) Using the infiltration adsorption process, the filler loading was carried out in the imprint network on the surface of the imprinted non-woven fabric after pressing: the 10 cm x 10 cm size of the pre-filled filler loading network non-woven fabric was immersed in the BNNS dispersion liquid with a concentration of 5 mg / ml, the solvent was deionized water, and after ultrasonic immersion adsorption for 2-3 min, it was placed in a 60°C oven for drying. This process was repeated to assemble the nanoparticles. The composite film is named BNNS-x / PET, where x represents the number of adsorptions. At the same time, the same non-woven fabric was selected without template transfer printing, and the same number of loadings were used as a control sample;

[0045] (5) The loaded non-woven fabric film was selected and hot pressed with a three-layer structure. The hot pressing process parameters were: temperature 180°C, pressure 15 MPa.

[0046] After the above steps, a template transfer imprint pre-filled filler loading network high thermal conductivity composite film was prepared.

[0047] The prepared thermal conductivity composite film was tested for thermal conductivity using HOT DISK. The in-plane thermal conductivity of the composite film was 3.38 W / mK, and the in-plane thermal conductivity of the control sample without template hot pressing transfer printing was 2.23 W / mK. The thermal conductivity performance improvement rate was 51.6%.

[0048] Example 3

[0049] A preparation method of a template transfer printing imprint prefilled filler load network high thermal conductivity multifunctional composite film, comprising the following steps:

[0050] (1) 3 g of PVDF powder is weighed with an electronic balance and dissolved in 30 mL of a mixed solvent of DMF and acetone (2:1), and magnetically stirred at room temperature for 3 h until completely dissolved, to prepare a PVDF electrospinning precursor solution. The solution is vacuumed and the operation is repeated three times to remove as much internal excess bubbles as possible;

[0051] (2) 10 mL of the PVDF electrospinning solution is taken by a syringe for electrospinning, and a cylindrical collector covered with aluminum foil is used as the collection device. The electrospinning parameters are set as follows: voltage 15 kv, syringe advancing speed 1 mL / h, solidification collection distance 12 cm, receiving rotation speed of the collector 350 rpm, and electrospinning is carried out at 45°C, with an environmental humidity of 23% to 25% (RH) relative humidity;

[0052] (3) After electrospinning, the electrospun PVDF fiber membrane is gently peeled off from the aluminum foil, cut into a 10 cm × 10 cm size fiber membrane, and dried at 60°C for 24 h to remove the unevaporated solvent;

[0053] (4) A template with different spacing matrices is selected, and the electrospun fiber membrane is used as the bottom layer and the template is used as the surface layer in a hot press. A certain pressure is used for hot pressing transfer printing, and the fiber substrate is pressed to achieve the purpose of prefilled filler load network. The hot pressing temperature is 50°C, and the pressure is 15 MPa;

[0054] (5) DIC, HOBT, KH550 and CNT-COOH (mass ratio 0.01:0.01:0.01:1) are added to the solvent DMSO, ultrasonic for 30 min, and mechanical stirring for 6 h. The mixture is left to stand, centrifuged, the supernatant is discarded and washed with anhydrous ethanol for 2-3 times to obtain KH550 modified CNTs. Then it is dispersed in anhydrous ethanol with Fe3O4 (mass ratio Fe3O4:CNTs=4:1), ultrasonic for 10 min, then add deionized water (mass ratio deionized water:anhydrous ethanol=4:96) dropwise to the mixture, keep stirring for 10 min, then centrifuge to remove the supernatant, vacuum drying to obtain Fe3O4@CNTs heterogeneous filler, marked as (Fe@C);

[0055] (6) Using infiltration adsorption process, loading filler in the pre-prepared space network on the surface of the fiber membrane after imprinting: 10 cm x 10 cm size hot-pressed transfer printing PVDF fiber membrane is immersed in Fe3O4@CNTs dispersion liquid with a concentration of 2 mg / ml, the solvent is deionized water, after ultrasonic infiltration adsorption for 2-3 min, it is placed in a 60 ℃ oven for drying, and this process is repeated for nano-particle assembly. The composite film is named Fe@C-x / PVDF, where x represents the number of times of infiltration adsorption, and the same fiber membrane is selected without template transfer printing, only loaded with the same number of times as a control sample;

[0056] (7) The loaded fiber membrane is selected to be hot-pressed with a three-layer structure, and the hot-pressing process parameters are: temperature 180 ℃, pressure 15 MPa.

[0057] After the above steps, a template transfer imprint pre-prepared filler loading network high-thermal-conductivity multifunctional composite film is prepared.

[0058] The prepared composite film is tested for thermal conductivity and electromagnetic shielding performance using HOT DISK and a vector network analyzer. The in-plane thermal conductivity of the composite film is 2.01 W / mK, and the electromagnetic shielding performance is 48.6 dB. The in-plane thermal conductivity of the control sample without template hot-pressing transfer printing is 1.62 W / mK, and the electromagnetic shielding performance is 30.6 dB. Compared with the control sample, the thermal conductivity is improved by 42%, and the electromagnetic shielding performance is also improved to a certain extent.

[0059] Example 4

[0060] A preparation method of a template transfer imprint pre-prepared filler loading network high-thermal-conductivity composite film, comprising the following steps:

[0061] (1) 2 g of BN powder is added to 200 mL of a mixed solvent of isopropanol and deionized water (1:1), and ultrasonic treatment is performed for 4 h using a CJ-020 type ultrasonic cleaner with a frequency of 40 KHz. The tgl-15b type super centrifuge is used for centrifugation at a speed of 1000 rpm for 20 min to remove the BN sheets that are not successfully exfoliated, and the supernatant is collected, and then 9000 rpm centrifugation is performed for 30 min to collect the successfully exfoliated BNNS;

[0062] (2) 0.5 g of the exfoliated BNNS of step one is added to 100 ml of a mixed solution of deionized water and anhydrous ethanol with a ratio of 1:1, and after stirring uniformly, ultrasonic dispersion is performed for 2 h using an ultrasonic cleaner to obtain a BNNs dispersion liquid with a concentration of 5 mg / ml;

[0063] (3) 500 mg CNFs were added into the obtained BNNs dispersion liquid, and high-speed stirring was carried out at 2000 rpm for 15 min to obtain a BNNs / CNFs dispersion liquid with a concentration of 5 mg / ml;

[0064] (4) 3 g PVA particles were weighed by an electronic balance and dissolved in 30 mL deionized water, and magnetic stirring was carried out at 90 ℃ for 3 h until complete dissolution. The solution was vacuumized, and the operation was repeated three times to remove as much internal excess bubbles as possible;

[0065] (5) The obtained PVA solution was uniformly coated into a film by using a doctor blade, and then was placed in a 60 ℃ oven for 10 min for thin film pre-curing;

[0066] (6) A matrix template with different spacing was selected, and the prepared film was used as a bottom layer and the template was used as a surface layer in a hot press. A certain pressure was used for hot pressing transfer printing, and the matrix was printed to achieve the purpose of preloading the filler network. The hot pressing temperature was 25 ℃, and the pressure was 10 MPa;

[0067] (7) A casting process was used to load fillers in the pre-prepared space network on the surface of the printed film: the BNNs / CNFs dispersion liquid with a concentration of 5 mg / ml prepared in the previous step was cast onto the surface of the film, and then was placed in a 60 ℃ oven for drying. The composite film was named PVA / BNNs / CNFs, and the same fiber film was selected without template transfer printing, and only the same number of fillers were loaded as a control sample;

[0068] (8) The loaded film was selected and hot pressed with a two-layer structure. The hot pressing process parameters were: temperature 100 ℃, pressure 10 MPa.

[0069] After the above steps, a template transfer printed pre-prepared filler loading network high thermal conductivity composite film was prepared.

[0070] The prepared thermal conductivity composite film was tested for thermal conductivity by HOT DISK. The in-plane thermal conductivity of the composite film was 1.79 W / mK, the in-plane thermal conductivity of the control sample without template hot pressing transfer printing was 1.33 W / mK, and the thermal conductivity performance improvement rate was 35.2%.

[0071] Example 5

[0072] A preparation method of a template transfer printed pre-prepared filler loading network high thermal conductivity composite film, comprising the following steps:

[0073] (1) 3 g PVDF powder was weighed by an electronic balance and dissolved in 30 mL of a mixed solvent of DMF and acetone (2:1), and magnetically stirred at room temperature for 3 h to fully dissolve, to prepare a PVDF electrospinning precursor solution. The solution was vacuumed and the operation was repeated three times to remove as much internal excess bubbles as possible;

[0074] (2) 10 mL of the PVDF electrospinning solution was taken by a syringe for electrospinning, and a cylindrical collector covered with aluminum foil was used as the collection device. The electrospinning parameters were set as follows: voltage 15 kv, syringe advancing speed 1 mL / h, solidification collection distance 12 cm, and the receiving rotation speed of the collector was 350 rpm. The electrospinning was carried out at 45 ℃, and the environmental humidity was 20%-25% (RH) relative humidity;

[0075] (3) After electrospinning, the electrospun PVDF fiber membrane was gently peeled off from the aluminum foil, cut into a fiber membrane with a size of 10 cm × 10 cm, and dried at 60 ℃ for 24 h to remove the unevaporated solvent;

[0076] (4) A template with different spacing matrices was selected, and the electrospun fiber membrane was used as the bottom layer and the template as the surface layer in the hot press. A certain pressure was used for hot pressing transfer printing, and the fiber substrate was printed to achieve the purpose of preloading the filler network. The hot pressing temperature was 30 ℃, and the pressure was 20 MPa;

[0077] (5) 0.5 g of Al2O3 was weighed by an electronic balance and added to 100 ml of a mixed solution of deionized water and anhydrous ethanol in a ratio of 1:1. After stirring uniformly, ultrasonic dispersion was carried out for 2 h using an ultrasonic cleaning machine to obtain an Al2O3 dispersion solution with a concentration of 5 mg / ml;

[0078] (6) The 3D printing injection method was used to load the filler in the pre-prepared space network on the surface of the printed film: the Al2O3 dispersion solution with a concentration of 5 mg / ml prepared in the previous step was placed in the container of the 3D printing equipment, and the filler was injected into the pre-prepared space network on the surface of the film according to a certain precise program. Subsequently, the film was placed in a 60 ℃ oven for drying. The composite film is named Al2O3 / PVDF. At the same time, the same fiber membrane was selected, and no template transfer printing was performed, only the same number of loadings were used as the control sample;

[0079] (7) The loaded fiber membrane was selected and hot pressed with a three-layer structure. The hot pressing process parameters were as follows: temperature 200 ℃, pressure 15 MPa.

[0080] After the above steps, a template transfer printing pre-prepared filler loading network high-thermal-conductivity composite film was prepared.

[0081] The prepared heat-conducting composite film is tested for heat-conducting performance using a HOT DISK, and the in-plane heat-conducting coefficient of the composite film is 1.32 W / mK, the in-plane heat-conducting coefficient of a comparative sample without template hot-pressing transfer is 1.02 W / mK, and the heat-conducting performance improvement rate is 29.8%.

[0082] Example 6

[0083] A preparation method of a template transfer imprint preformed filler loaded network high-heat-conducting composite film, comprising the following steps:

[0084] (1) 3 g of PVDF powder is weighed using an electronic balance and dissolved in 30 mL of a mixed solvent of DMF and acetone (2:1), and magnetically stirred at room temperature for 3 h until completely dissolved, to prepare a PVDF electrospinning precursor solution, and the solution is vacuumed and the operation is repeated three times to remove as much internal excess bubbles as possible;

[0085] (2) 10 mL of the PVDF electrospinning solution is taken using a syringe for electrospinning, and a cylindrical collector covered with aluminum foil is used as the collection device, and the electrospinning parameters are set as follows: voltage 15 kv, syringe advancing speed 1 mL / h, solidification collection distance 12 cm, and the receiving speed of the collector is 350 rpm, and the electrospinning is carried out at 45°C, and the relative humidity of the environment is 20%-25% (RH);

[0086] (3) After electrospinning, the electrospun PVDF fiber membrane is gently peeled off from the aluminum foil, cut into a fiber membrane with a size of 10 cm × 10 cm, and dried at 60°C for 24 h to remove the unevaporated solvent;

[0087] (4) A matrix template with different spacing is selected, and the electrospun fiber membrane is used as the bottom layer and the template is used as the surface layer in the hot press, and a certain pressure is used for hot-pressing transfer, and the fiber substrate is imprinted to achieve the purpose of preformed filler loading network, and the hot-pressing temperature is 30°C and the pressure is 20 MPa;

[0088] (5) 2 g of BN powder is added to 200 mL of a mixed solvent of isopropanol and deionized water (1:1), and a CJ-020 type ultrasonic cleaner is used for ultrasonic treatment for 4 h, and the frequency is 40 KHz. A tgl-15b type super centrifuge is used for centrifugation at a speed of 1000 rpm for 20 min, and the BN sheets that are not successfully peeled off are removed, and the supernatant is collected, and then 9000 rpm centrifugation is performed for 30 min, and the successfully peeled BNNS is collected;

[0089] (6) Take 0.5 g of BNNS peeled off in step one and add to 100 ml of a mixed solution of deionized water and anhydrous ethanol in a ratio of 1:1, stir uniformly, and then use an ultrasonic cleaning machine for ultrasonic dispersion for 2 h to obtain a BNNS dispersion solution with a concentration of 5 mg / ml;

[0090] (7) Adopt a doctor blade process to load fillers in the pre-prepared space network on the surface of the fiber film after embossing: place the previously prepared BNNS dispersion solution with a concentration of 5 mg / ml in a doctor blade, and load fillers on the surface of the film in the form of a doctor blade. Then dry the film in a 60°C oven, and here the composite film is named BNNs / PVDF, and the same fiber film is selected, without template transfer, and only loaded the same number of times as a control sample;

[0091] (8) Select the loaded film to be hot-pressed in a three-layer structure, with the hot-pressing process parameters being: temperature 180°C, pressure 20 MPa.

[0092] After the above steps, a template transfer imprint pre-prepared filler-loaded network high-thermal-conductivity composite film is prepared.

[0093] The prepared thermal-conductivity composite film is tested for thermal conductivity using a HOT DISK, and the in-plane thermal conductivity of the composite film is 2.64 W / mK, the in-plane thermal conductivity of the control sample without template hot-pressing transfer is 1.90 W / mK, and the thermal conductivity performance improvement rate is 38.9%.

[0094] Example 7

[0095] A method for preparing a template transfer imprint pre-prepared filler-loaded network high-thermal-conductivity composite film, comprising the following steps:

[0096] (1) Weigh 3 g of PVDF powder with an electronic balance and dissolve it in 30 mL of a mixed solvent of DMF and acetone (2:1), and magnetically stir at room temperature for 3 h until completely dissolved, to prepare a PVDF electrospinning precursor solution. Vacuumize the solution and repeat the operation three times to remove as much internal excess gas bubbles as possible;

[0097] (2) Use a syringe to take 10 mL of the PVDF electrospinning solution for electrospinning, and use a cylindrical collector covered with aluminum foil as the collection device; the electrospinning parameters are set as follows: voltage 15 kv, push speed 1 mL / h, solidification collection distance 12 cm, and the receiving speed of the cylindrical collector is 350 rpm; electrospinning is carried out at 45°C, and the relative humidity of the environment is 20%-25% (RH);

[0098] (3) After electrospinning, the electrospun PVDF fiber membrane was gently peeled off from the aluminum foil, cut into a 10 cm x 10 cm fiber membrane and dried at 60°C for 24 h to remove the unvolatilized solvent;

[0099] (4) Select a matrix template with different spacing, use the electrospun fiber membrane as the bottom layer and the template as the surface layer in the hot press, and perform hot press transfer printing under a certain pressure to press the fiber substrate to achieve the purpose of prefilling the space network. The hot press temperature is 30°C, and the pressure is 10 MPa;

[0100] (5) Using the infiltration adsorption process, load the filler in the imprint network on the surface of the fiber membrane after pressure printing: immerse the 10 cm x 10 cm hot press transfer printed PVDF fiber membrane into a BNNS and CNTs dispersion solution with a concentration of 2 mg / ml, the solvent is deionized water, and after ultrasonic immersion adsorption for 2-3 min, place it in a 60°C oven for drying. This process is repeated to assemble nanoparticles. The two composite films are named BNNS-x / PVDF and CNT-x / PVDF, respectively, where x represents the number of adsorptions. Select the same fiber membrane without template transfer printing and load the same number of times as the control sample;

[0101] (6) Select the loaded fiber membrane and adopt the layered film particle insulation property regulation strategy. Design the BNNS-x / PVDF fiber membrane as the upper and lower insulating layers, and the CNT-x / PVDF as the middle high thermal conductivity and conductivity layer. Perform hot pressing with a three-layer structure, and the hot pressing process parameters are: temperature 200°C, pressure 15 MPa.

[0102] After the above steps, a template transfer imprint prefilling network high thermal conductivity composite film is prepared.

[0103] The prepared thermal conductivity composite film is tested for thermal conductivity using HOT DISK. The in-plane thermal conductivity of the BNNs-3 / CNTs-3 / PVDF composite film is 2.68 W / mK, and the in-plane thermal conductivity of the control sample without template hot press transfer printing is 1.96 W / mK, and the thermal conductivity performance improvement rate is 36.6%.

Claims

1. A stencil transfer printed imprint preform filler loaded network high thermal conductivity composite film, characterized in that, The composite film is formed by the following steps: 1) preparing a polymer film layer by electrospinning, blade coating or spin coating process; 2) stacking the polymer film layer prepared in step 1) in order, and then performing template transfer hot pressing on the film layer by using a hot press with a matrix grid to obtain a precision imprinted polymer film layer with a template imprinting grid line space diameter of 0.05-10 mm and a template matrix spacing of 0.1-20 mm; 3) uniformly dispersing different types of heat-conducting fillers in a dispersant to obtain different heat-conducting filler dispersions; 4) loading the heat-conducting filler dispersions obtained in step 3) onto the polymer film layer obtained in step 2) to obtain a composite film layer containing one or more types of heat-conducting fillers; the total loading amount of the fillers is 5%-100% of the mass of the film; and 5) hot pressing the film prepared in step 4) in a single-layer or multi-layer structure to obtain a template transfer imprinted pre-filled network high-thermal-conductivity composite film. The polymer film layer is prepared from polylactic acid (PLA), polyvinyl alcohol (PVA), thermoplastic polyurethane (TPU), polyurethane (PU), polyvinylidene fluoride (PVDF) or polyolefin (POE) material. The one-dimensional heat-conducting filler is at least one of carbon nanotube (CNT), carbon nitride nanotube (CNNT), silicon carbide nanowire (SiCNW) or silver nanowire (AgNW), and has a length of 10-200 μm. The two-dimensional heat-conducting filler is at least one of boron nitride nanosheet (BNN), graphene nanosheet (GNP) or MXene, and has a particle size of 100 nm-5 μm and a thickness of 5 nm-800 nm. The special-shaped heat-conducting filler is at least one of core-shell structure Al2O3@BN or core-shell structure Fe3O4@CNT, and has a particle size of 500 nm-100 μm. The heat-conducting filler is loaded in the imprinted space network structure after hot transfer printing by means of cyclic infiltration adsorption, electrostatic spraying, blade coating, casting or 3D printing injection.

2. The template transfer printed preformed filler loaded network high thermal conductivity composite film according to claim 1, wherein, In step 2), the template transfer hot pressing process is performed at a temperature of 10-50 ℃ and a pressure of 1-20 MPa; and in step 5), the hot pressing process is performed at a temperature of 100-300 ℃ and a pressure of 1-30 MPa.

3. The template transfer printed preformed filler loaded network high thermal conductivity composite film according to claim 1, wherein, ​ 4. The template transfer printed preformed filler loaded network high thermal conductivity composite film of claim 1, wherein, ​ ​ 5. The template transfer printed preformed filler loaded network high thermal conductivity composite film according to claim 1, wherein, ​ 6. The template-stamped imprint preformed filler loaded network high thermal conductivity composite film according to claim 1, wherein, ​ 7. The template transfer printed preformed filler loaded network high thermal conductivity composite film according to claim 1, wherein, In step 4), the loading is to completely immerse the polymer film layer into one of the thermally conductive filler dispersions prepared in step 3), and after adsorbing for 10-30 s, dry, and then immerse into the same or other thermally conductive filler dispersion for 10-30 s, and dry, and repeat the immersion for 1-5 times; or use spraying, casting, blade coating, 3D printing injection process to imprint space on the film layer with fillers.

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