A high thermal conductivity composite film with needle-punched open-pore structure and preparation method thereof

Abstract

The present invention discloses a high thermal conductivity composite film with a needle-punched open-pore structure and a preparation method thereof. The film is made by hot rolling of a single-layer or multi-layer fiber film loaded with thermally conductive fillers, and the film has a matrix array of needle-punched open-pore structures; the thermally conductive filler is at least one of a zero-dimensional thermally conductive filler, a one-dimensional thermally conductive filler, a two-dimensional thermally conductive filler or a special-shaped thermally conductive filler. By punching holes in the needle-punched matrix, the degree of freedom of the self-assembled network is effectively constrained, and the loose self-assembled network is further compressed and assembled, which can achieve the densification of the thermal conductive network and form a better thermal conductive path. The composite film solves the problems of dispersed construction of the thermal conductive network in the thermal interface material under the preparation conditions of conventional filling methods, large interface thermal resistance between fillers and contact thermal resistance of the thermal interface, etc. It has the advantages of efficient improvement of thermal conductivity, simple preparation process, and easy large-scale production. It has great potential in the continuous production of thermally conductive composite film materials.

Description

Technical Field

[0001] The present invention relates to the technical field of thermally conductive composite films, in particular to a high-thermal-conductive composite film with a needle-punched open-pore structure and a preparation method thereof. Background Art

[0002] With the increasing development of 5G communication technology, modern electronic devices are moving towards high integration, miniaturization, and high power. This poses a severe challenge to the heat dissipation system of electronic devices. During operation, the equipment usually generates a large amount of heat that cannot be effectively dissipated, seriously affecting its service life and stability. Some studies have shown that an increase of 2% in the internal temperature of electronic devices will cause the heat to dissipate rapidly. ◦ C will cause a decrease in overall device performance of approximately 10%. Polymers, with their advantages of simple processing, good chemical stability, low cost, and light weight, are ideal matrices for preparing thermally conductive composite materials. However, the low thermal conductivity of conventional polymer materials (0.1 W / mK) cannot meet the heat dissipation requirements of electronic devices. Introducing thermally conductive fillers into the polymer matrix to form a coherent and efficient thermal network is one of the effective methods to improve the thermal conductivity of polymer composites.

[0003] For traditional filled polymer-based thermally conductive composites, excessive dispersion or poor contact between fillers, as well as defects in the filler-matrix interface, can lead to an incomplete thermal network, severely degrading thermal conductivity. Therefore, the key to improving the thermal conductivity of composite materials lies in constructing a complete, coherent, and efficient thermal network. Simultaneously, it is also crucial to effectively reduce the contact thermal resistance between fillers and fillers, and between fillers and the matrix. Summary of the Invention

[0004] The present invention aims to address the shortcomings of existing thermal interface materials, such as a loose thermal network, high interfacial contact thermal resistance, and difficulty in improving in-plane thermal conductivity. The present invention provides a high-thermal-conductivity composite film thermal interface material with a needle-punched open-pore structure and a method for preparing the same. This film, through spatial matrix fiber confinement, transforms the original loose self-assembled network into a dense, forced-assembled network, improving the thermal conductivity of the composite material. While forming an excellent, coherent thermal conduction path, it also effectively reduces the interfacial thermal resistance between internal fillers. Furthermore, it increases interfiber contact to achieve lower contact thermal resistance. The material offers advantages such as high thermal conductivity improvement, a simple preparation process, and ease of large-scale production, promising promising future development.

[0005] The technical solution for realizing the present invention is:

[0006] A high thermal conductivity composite film with a needle-punched open-pore structure, which is made by hot calendering a single or multiple fiber film layer loaded with thermally conductive fillers, and has a matrix array of needle-punched open-pore structures within the film; the thermally conductive filler is at least one of a zero-dimensional thermally conductive filler, a one-dimensional thermally conductive filler, a two-dimensional thermally conductive filler or a special-shaped thermally conductive filler.

[0007] The zero-dimensional thermal conductive filler is one of spherical aluminum oxide Al2O3 and spherical aluminum nitride AlN, and its particle size is 500nm-100μm.

[0008] The one-dimensional thermal conductive filler is one of carbon nanotubes CNTs, carbon nitride nanotubes CNNTs, silicon carbide nanowires SiCNWs, and silver nanowires AgNWs, and has a length of 10 μm-200 μm.

[0009] The two-dimensional thermal conductive filler is one of boron nitride nanosheets BNNs, graphene nanosheets GNPs, and MXene, and has a particle size of 100nm-5μm and a thickness of 5nm-800nm.

[0010] The special-shaped heat-conductive filler is one of tetrapod-shaped zinc oxide ZnO and expanded graphite EG, and its particle size is 500nm-100μm.

[0011] The thermally conductive filler can be loaded in the fiber film through cyclic infiltration adsorption, electrostatic self-assembly, spraying or electrostatic spinning technology.

[0012] The fiber film layer can be an electrospun fiber film made of TPU, PU, polyvinylidene fluoride PVDF, polyolefin POE, polyvinyl alcohol PVA spinnable material, or one of non-woven fabrics, woven fabrics, fiber felt, and carbon fiber cloth, with a fiber diameter of 50nm-50μm and a surface density of 10g-30g / m 2 .

[0013] A method for preparing a high-thermal-conductivity composite film with a needle-punched open-pore structure comprises the following steps:

[0014] 1) Different types of thermally conductive fillers are added to the dispersant and dispersed evenly to prepare dispersions of different thermally conductive fillers;

[0015] 2) The fiber film layer is completely immersed in one of the thermally conductive filler dispersions prepared in step 1) for 10-30 seconds and then dried, and then immersed in the same or other thermally conductive filler dispersions for 10-30 seconds and then dried, and this immersion is repeated 1-10 times to obtain fiber film layers containing one or more thermally conductive fillers; or a fiber film layer containing thermally conductive fillers is obtained by co-spinning, spraying, or electrostatic self-assembly. The total filler loading is 30%-200% of the fiber film mass.

[0016] 3) After the single-layer fiber film layer or multiple-layer fiber film prepared in step 2) is neatly stacked, the fiber film layer is needle-punched and hot-calendered using a hot calendering device with a roller needle and a punching needle of appropriate specifications to obtain a high thermal conductivity composite film with a needle-punched open hole structure having a pore size of 0.05-1 mm and a pore spacing of 0.1-1 mm.

[0017] In step 3), the needle punching hot calendering process is as follows: temperature of 100-300° C., pressure of 1-30 MPa, and calendering speed of 0.01-10 m / min.

[0018] The present invention provides a high thermal conductivity composite film with a needle-punched open-pore structure and a preparation method thereof, which has the following advantages over the prior art:

[0019] (1) The composite film is made to fit closely together through needle punching and hot pressing, which physically densifies the fibers loaded with fillers as much as possible in the areas without holes. While constraining the freedom of the fiber network, it compresses and assembles the loose self-assembled network, which can spatially constrain the fibers loaded with fillers to form an efficient and coherent heat conduction path. This not only ensures the overall mechanical properties of the film, including tensile properties, but also increases the contact area between the heat-conducting fibers, enhances the interface effect, reduces the contact thermal resistance, and improves the thermal conductivity and heat dissipation performance of the composite film.

[0020] (2) The fiber structure of the composite film can be loaded with one or more thermal conductive fillers by ultrasonic-assisted cyclic impregnation, electrostatic self-assembly, spraying, and co-spinning. While improving the dispersion of the filler load, it can also achieve the idea of synergistic regulation of structure and function, and construct an efficient thermal conductive path.

[0021] (3) The selected fiber membranes are constructed with different numbers of layers and then subjected to heat calendering, so that the fibers come into contact and melt under the combined action of shear force and pressure. The thermally conductive fillers loaded on their surfaces are able to have more effective contact, thereby constructing a three-dimensional coherent thermal conductive network, which enables heat to be transferred in the vertical direction and improves the heat dissipation effect. While reducing the thermal resistance of the filler-matrix and filler-filler interfaces, it also increases the contact area between the film and the heat source, reduces the contact thermal resistance, and improves the thermal conductivity. Compared with the non-needled structure, the thermal conductivity of this structure is improved by 33.65%-70.20%.

[0022] (4) The composite film has the advantages of simple preparation, low cost and good thermal conductivity. It is suitable for use as a thermal interface material in the field of electronic packaging. It can be used to prepare composite materials with dense thermal conductive networks and has great potential in the continuous production of thermal conductive composite materials.

[0023] The method of needle-punched spatial matrix fiber confinement can be used to construct a dense and continuous thermal conductive network inside the composite material. This method uses forced compression to physically transform the original loose self-assembled network into a dense forced assembly network, achieving effective densification of the thermal conductive network, which provides the possibility of significantly improving thermal conductivity. In addition, the needle-punched hot pressing method with a multi-layer fiber membrane structure transforms the thermal conductive filler network from a "dispersed state" to a "pillar state", which can promote heat energy transfer. In addition to the heat dissipation of the densified thermal conductive network, the matrix fibers can also absorb a large amount of heat energy and dissipate it into the air. This process is the same as the process of water flowing in a thermal conductive network similar to sand, resulting in a higher heat dissipation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the model for preparing the composite film in Example 3;

[0025] Figure 2 Schematic diagram of the needle-punched open-pore structure composite film prepared in Example 3.

[0026] Figure 3 This is an optical microscope photograph of the needle-punched open-pore structure composite film prepared in Example 3. Implementation Method

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the present invention is not limited thereto. Example

[0028] A method for preparing a BNNS / PET non-woven fabric needle-punched open-pore structure high thermal conductivity composite film, comprising the following steps:

[0029] (1) 2 g of BN powder was added to a 1:1 mixture of isopropanol and deionized water (200 mL). Ultrasonic treatment was performed for 4 h using a CJ-020 ultrasonic cleaner at a frequency of 40 kHz. The unstripped BN sheets were removed by centrifugation at 1000 rpm for 20 min using a TGL-15B supercentrifuge. The supernatant was collected and centrifuged at 9000 rpm for 30 min to collect the successfully stripped BNNS.

[0030] (2) Weigh 2 g of the BNNS peeled in step 1 and add it to 100 ml of a mixed solution of deionized water and anhydrous ethanol in a ratio of 1:1. After stirring evenly, use an ultrasonic cleaner to ultrasonically disperse it for 2 h to obtain a BNNS dispersion with a concentration of 20 mg / ml.

[0031] (3) Dissolve 1 g of polyethyleneimine in 100 ml of deionized water and stir until a uniform solution is obtained to obtain a polyethyleneimine solution with a concentration of 10 mg / ml. Cut the PET nonwoven fabric into several 10 cm × 10 cm square films and immerse them in the polyethyleneimine solution. After 10 seconds, remove the film to obtain the surface-modified PET nonwoven fabric.

[0032] (4) The BNNS dispersion obtained in step (2) was placed in an ultrasonic cleaning machine for ultrasonic dispersion. At the same time, the surface-modified PET non-woven fabric obtained in step (3) was immersed in the BNNS dispersion during ultrasonic treatment, taken out after 10 seconds, and dried at 60°C for 30 minutes to obtain a PET non-woven fabric that had adsorbed BNNS once.

[0033] (5) Repeat the process (3) to (4) five times with the PET nonwoven fabric that has adsorbed BNNS once obtained in step (4) to obtain a PET nonwoven fabric that has cyclically adsorbed BNNS five times.

[0034] (6) The PET nonwoven fabric obtained in step (5) that had been cyclically adsorbed with BNNS five times was used as a single-layer fiber membrane structure. A matrix array of perforated needles of appropriate size was selected and calendered on a double-roll calender to obtain an open-pore fiber film. The calendering process parameters were: temperature 180°C, pressure 12 MPa, and speed 0.6 m / min. The same fiber membrane was selected and simply hot-calendered without needle punching to form the holes as a control sample.

[0035] After the above steps, a heat-conducting composite film with a needle-punched open-pore structure is prepared.

[0036] The resulting thermally conductive composite film was tested for thermal conductivity using the laser flash method. The in-plane thermal conductivity of the porous film was 2.59 W / mK, and the out-of-plane thermal conductivity was 0.98 W / mK. The in-plane thermal conductivity of the non-porous film was 1.93 W / mK, and the out-of-plane thermal conductivity was 0.74 W / mK. This represents a 33.65% improvement in thermal conductivity compared to a non-porous structure. Example

[0037] A method for preparing an Al2O3 / PET non-woven fabric needle-punched open-pore structure high thermal conductivity composite film, comprising the following steps:

[0038] (1) Take 2 g of Al2O3 nanoparticles and add them to 100 ml of a mixed solution of deionized water and anhydrous ethanol in a ratio of 1:1. After stirring evenly, use an ultrasonic cleaner to ultrasonically disperse for 2 h to obtain an Al2O3 nanoparticle dispersion with a concentration of 20 mg / ml.

[0039] (2) Dissolve 1g of polyethyleneimine in 100ml of deionized water and stir until a uniform solution is obtained to obtain a polyethyleneimine solution with a concentration of 10mg / ml. Cut the PET nonwoven fabric into several 10cm×10cm square films and immerse them in the polyethyleneimine solution. After 10 seconds, remove them and obtain the surface-modified PET nonwoven fabric.

[0040] (3) The Al2O3 nanoparticle dispersion was loaded into a commercial spray gun and evenly sprayed once on the upper and lower surfaces of the PET nonwoven fiber membrane. During the spraying process, the working distance between the nozzle and the sample was 5 cm and the pressure was 0.5 MPa.

[0041] (4) The PET nonwoven fabric sprayed with aluminum oxide nanoparticles obtained in step (3) was dried before the next spraying, with 5 ml of the dispersion being sprayed on each side of the fiber membrane.

[0042] (5) The PET nonwoven fabric sprayed with aluminum oxide nanoparticles obtained in step (4) was formed into a double-layer fiber membrane structure with a single-layer membrane thickness as the depth. A perforated needle array of appropriate size was selected and the single-sided perforated fiber film was obtained by calendering on a double-roll calender. The calendering process parameters were: temperature 180°C, pressure 12 MPa, and speed 0.6 m / min. The same double-layer fiber membrane was selected and simply hot-calendered without needle punching as a control sample.

[0043] After the above steps, a heat-conducting composite film with a needle-punched open-pore structure is prepared.

[0044] The resulting thermally conductive composite film was tested for thermal conductivity using the laser flash method. The in-plane thermal conductivity of the porous film was 3.27 W / mK, and the out-of-plane thermal conductivity was 0.82 W / mK. The in-plane thermal conductivity of the non-porous film was 2.35 W / mK, and the out-of-plane thermal conductivity was 0.59 W / mK. This represents a 39.03% improvement in thermal conductivity compared to a non-porous structure. Example

[0045] A method for preparing a CNTs / PVDF polyvinylidene fluoride needle-punched open-pore structure high thermal conductivity composite film comprises the following steps:

[0046] (1) 2 g of CNTs were weighed using an electronic balance and dispersed in 30 mL of a mixed solvent of DMF and acetone (2:1). Ultrasonic dispersion was performed at 25 °C for 2 h to obtain a uniformly dispersed mixture.

[0047] (2) Then, 3 g of PVDF powder was dissolved in the CNTs dispersion and magnetically stirred at room temperature for 3 h until fully dissolved to prepare a CNTs / PVDF electrospinning precursor solution. The mixed solution was vacuumed and the operation was repeated three times to remove as many bubbles as possible.

[0048] (3) 10 mL of PVDF electrospinning solution was drawn into a syringe for electrospinning. A cylindrical collector covered with aluminum foil was used as the collection device. The electrospinning parameters were set as follows: voltage 15 kV, propulsion speed 1 mL / h, solidification collection distance 12 cm, and cylindrical collector receiving speed 350 rpm. Electrospinning was performed at 45°C in an ambient humidity of 23% to 25% relative humidity (RH).

[0049] (4) After electrospinning, the co-spun PVDF / CNTs fiber membrane was gently peeled off from the aluminum foil, cut into 10 cm × 10 cm fiber membranes and dried at 60 °C for 24 h to remove the unevaporated solvent.

[0050] (5) A co-spun fiber membrane was selected, with a three-layer structure. A matrix of perforated needles of appropriate size was selected and the membrane was calendered on a double-roll calender to obtain an open-pore fiber film. The calendering process parameters were: temperature 180°C, pressure 14 MPa, and speed 0.6 m / min. A control sample was also selected from the same three-layer fiber membrane, which was not needle-punched and was simply hot-calendered.

[0051] After the above steps, a heat-conducting composite film with a needle-punched open-pore structure is prepared.

[0052] The resulting thermally conductive composite film was tested for thermal conductivity using the laser flash method. The in-plane thermal conductivity of the porous film was 4.19 W / mK, and the out-of-plane thermal conductivity was 1.16 W / mK. The in-plane thermal conductivity of the non-porous film was 3.06 W / mK, and the out-of-plane thermal conductivity was 0.85 W / mK. This represents a 37.20% improvement in thermal conductivity compared to a non-porous structure. Example

[0053] A method for preparing a BN / PVDF polyvinylidene fluoride needle-punched open-pore structure high thermal conductivity composite film comprises the following steps:

[0054] (1) 2 g of BN powder was added to a 1:1 mixture of isopropanol and deionized water (200 mL). Ultrasonic treatment was performed for 4 h using a CJ-020 ultrasonic cleaner at a frequency of 40 kHz. The unstripped BN sheets were removed by centrifugation at 1000 rpm for 20 min using a TGL-15B supercentrifuge. The supernatant was collected and centrifuged at 9000 rpm for 30 min to collect the successfully stripped BNNS.

[0055] (2) Negative ion modification of BNNS nanoparticles: 1.0 g of sodium polyacrylate (PAAS) was added to 200 ml of distilled water to obtain a 0.5 wt% anionic polyelectrolyte solution. The exfoliated BNNS was placed in the mixed solution and magnetically stirred at 25 degrees for 48 h. The negatively charged BNNS was collected by filtration. After filtration and drying, it was dissolved in 80 ml of a mixed solution of deionized water and anhydrous ethanol (3:1) and ultrasonically dispersed for 2 h to obtain PAAS-BNNS.

[0056] (3) 3 g of PVDF was weighed and dissolved in 30 ml of a mixed solvent of DMF and acetone (2:1). The mixture was stirred magnetically for 30 minutes until fully dissolved to prepare an electrospinning precursor solution. Subsequently, 10 ml of the PVDF electrospinning solution was drawn up using a syringe for electrospinning. The collection device used a high-speed rotating hub aluminum foil. The electrospinning parameters were set as follows: voltage 15 kV, propulsion speed 1 ml / h, solidification collection distance 12 cm, and hub collector speed 360 r / min. The electrospun film was collected and dried at 60 degrees for 24 h.

[0057] (4) PEI positive modification of the electrospun film: Pure PVDF electrospun films cut into 10*10 cm pieces were immersed in a 2 mg / ml PEI solution (80 ml of a 1:1 mixture of deionized water and anhydrous ethanol). The film was immersed in the PEI solution for 3 minutes to ensure that the film was fully modified by PEI. After immersion, the film surface was rinsed with deionized water.

[0058] (5) The modified film is immersed in the BNNS particle dispersion again to absorb the nanoparticles, and then dried in an oven at 60 degrees for 24 hours. This process is repeated, and the BNNS nanoparticles are assembled layer by layer through the electrostatic interaction of positive and negative charges.

[0059] (6) A three-layered fiber membrane after electrostatic assembly loading was selected. A matrix of punching needles of appropriate size was used and the membrane was calendered on a double-roll calender to obtain an open-pore fiber film. The calendering process parameters were: temperature 180°C, pressure 14 MPa, and speed 0.6 m / min. At the same time, the same three-layered fiber membrane was selected and subjected to simple hot calendering without needle punching as a control sample.

[0060] After the above steps, a heat-conducting composite film with a needle-punched open-pore structure is prepared.

[0061] The thermal conductivity of the prepared thermally conductive composite film was tested using the laser flash method. The in-plane thermal conductivity of the perforated film was 4.46W / mK, and the out-of-plane thermal conductivity was 0.88W / mK. The in-plane thermal conductivity of the non-perforated film was 3.13W / mK, and the out-of-plane thermal conductivity was 0.62W / mK. The thermal conductivity is about 42.71% higher than that of the non-punctured perforated structure. Example

[0062] A method for preparing an Al2O3 / Ni-CNTs / PVDF polyvinylidene fluoride needle-punched open-pore structure high thermal conductivity composite film comprises the following steps:

[0063] 2 g of Al2O3 and Ni-CNTs were weighed using an electronic balance and dispersed in 30 mL of a mixed solvent of DMF and acetone (2:1) in sequence. Ultrasonic dispersion was performed at 25 °C for 2 h to obtain two uniformly dispersed mixed solutions.

[0064] Subsequently, 3 g of PVDF powder was dissolved in the two prepared dispersions and magnetically stirred at room temperature for 3 h until fully dissolved to prepare an electrospinning precursor solution. The mixed solution was vacuumed and the operation was repeated three times to remove as many bubbles as possible.

[0065] Electrospinning was performed using a syringe to draw 10 mL of the mixed electrospinning solution. A cylindrical collector covered with aluminum foil was used as the collection device. The electrospinning parameters were: voltage 14 kV, propulsion speed 1 mL / h, solidification collection distance 12 cm, and cylindrical collector speed 350 rpm. Electrospinning was performed at 45°C in an ambient humidity of 23% to 25% relative humidity (RH). Two co-spun fiber membranes, Al2O3 / PVDF and Ni-CNTs / PVDF, were prepared.

[0066] After electrospinning, the co-spun fiber membrane was gently peeled off from the aluminum foil, cut into 10 cm × 10 cm fiber membranes and dried at 60 °C for 24 h to remove the unvolatile solvent.

[0067] A punching needle with a matrix array of appropriate size is selected to punch holes in the Ni-CNTs / PVDF co-spun fiber membrane, and then the needle-punched perforated fiber membrane is obtained by calendering it with a double-roll calender.

[0068] A sandwich structure was assembled using a needle-punched Ni-CNTs / PVDF fiber membrane as the middle layer and unpunctured Al2O3 / PVDF fiber membranes as the upper and lower surface layers, then hot-pressed. The calendering process parameters were: temperature 180°C, pressure 14 MPa, and speed 0.6 m / min. A control sample was also selected, using the same three-layer fiber membrane but subjected to simple hot calendering without needle-punching.

[0069] Through the above steps, a heat-conducting and electromagnetic shielding multifunctional film with a needle-punched open-hole structure is prepared.

[0070] The thermal conductivity of the prepared composite film was tested using the laser flash method. The in-plane thermal conductivity of the perforated film was 5.11W / mK, and the out-of-plane thermal conductivity was 1.28W / mK. The in-plane thermal conductivity of the non-perforated film was 3.81W / mK, and the out-of-plane thermal conductivity was 0.96W / mK. The thermal conductivity is about 34.33% higher than that of the non-punctured perforated structure. Example

[0071] A method for preparing a BN / PET / PDMS needle-punched open-pore structure high thermal conductivity composite film comprises the following steps:

[0072] (1) 2 g of BN powder was added to a 1:1 mixture of isopropanol and deionized water (200 mL). Ultrasonic treatment was performed for 4 h using a CJ-020 ultrasonic cleaner at a frequency of 40 kHz. The unstripped BN sheets were removed by centrifugation at 1000 rpm for 20 min using a TGL-15B supercentrifuge. The supernatant was collected and centrifuged at 9000 rpm for 30 min to collect the successfully stripped BNNS.

[0073] (2) Weigh 2 g of the BNNS peeled in step 1 and add it to 100 ml of a mixed solution of deionized water and anhydrous ethanol in a ratio of 1:1. After stirring evenly, use an ultrasonic cleaner to ultrasonically disperse it for 2 h to obtain a BNNS dispersion with a concentration of 20 mg / ml.

[0074] (3) Dissolve 1 g of polyethyleneimine in 100 ml of deionized water and stir until a uniform solution is obtained to obtain a polyethyleneimine solution with a concentration of 10 mg / ml. Cut the PET nonwoven fabric into several 10 cm × 10 cm square films and immerse them in the polyethyleneimine solution. After 10 seconds, remove the film to obtain the surface-modified PET nonwoven fabric.

[0075] (4) The BNNS dispersion obtained in step (2) was placed in an ultrasonic cleaning machine for ultrasonic dispersion. At the same time, the surface-modified PET non-woven fabric obtained in step (3) was immersed in the BNNS dispersion during ultrasonic treatment, taken out after 10 seconds, and dried at 60°C for 30 minutes to obtain a PET non-woven fabric that had adsorbed BNNS once.

[0076] (5) Repeat the process (3) to (4) five times with the PET nonwoven fabric that has adsorbed BNNS once obtained in step (4) to obtain a PET nonwoven fabric that has cyclically adsorbed BNNS five times.

[0077] (6) The PET nonwoven fabric obtained in step (5) that had been cyclically adsorbed with BNNS five times was used as a three-layer fiber membrane structure. A matrix array of perforated needles of appropriate size was selected and calendered on a double-roll calender to obtain an open-pore fiber film. The calendering process parameters were: temperature 180°C, pressure 12 MPa, and speed 0.6 m / min. The same fiber membrane was selected and simply hot-calendered without needle punching to form the holes as a control sample.

[0078] (7) Weigh 0.5 g of the BNNS exfoliated in step 1 and disperse it in PDMS. Add the curing agent at a mass ratio of 10:1 PDMS prepolymer to curing agent, and dilute with 5 ml of n-hexane. Ultrasonic disperse the mixture into a uniform mixture. Transfer the mixture to a vacuum chamber for defoaming until no bubbles appear. Finally, apply the resulting mixture evenly to the upper and lower surfaces of the needle-punched fiber membrane. The same treatment is applied to the fiber membrane without holes. Dry the fiber membrane at 120°C for 24 h.

[0079] After the above steps, a heat-conducting composite film with a needle-punched open-pore structure is prepared.

[0080] The resulting composite film was tested for thermal conductivity using the laser flash method. The in-plane thermal conductivity of the porous film was 5.49 W / mK, and the out-of-plane thermal conductivity was 1.42 W / mK. The in-plane thermal conductivity of the non-porous film was 4.1 W / mK, and the out-of-plane thermal conductivity was 1.06 W / mK. This represents a 34.03% improvement in thermal conductivity compared to a structure without puncture holes.

Claims

1. A high thermal conductivity composite film with a needle-punched open-pore structure, characterized in that: The film is made by hot calendering of a single or multi-layer fiber film loaded with a thermally conductive filler, and the film has a matrix array of needle-punched open pores; the thermally conductive filler is at least one of a zero-dimensional thermally conductive filler, a one-dimensional thermally conductive filler, a two-dimensional thermally conductive filler, or a special-shaped thermally conductive filler; The method for preparing the composite film comprises the following steps: 1) Different types of thermally conductive fillers are added to the dispersant and dispersed evenly to prepare dispersions of different thermally conductive fillers; 2) Immersing the fiber film layer completely in one of the thermally conductive filler dispersions prepared in step 1) for 10-30 seconds, followed by drying. Then, immersing the fiber film layer in the same or another thermally conductive filler dispersion for 10-30 seconds, followed by drying, repeating this immersion process 1-10 times to obtain fiber film layers containing one or more thermally conductive fillers. Alternatively, the film layer may be loaded with thermally conductive fillers by co-spinning, spraying, or electrostatic self-assembly processes; the total loading of thermally conductive fillers is 30%-200% of the mass of the fiber film. 3) stacking the single or multiple fiber film layers obtained in step 2) neatly, and then performing needle punching and hot calendering on the fiber film layers using a roller needle hot calendering device with perforated needles of appropriate specifications, thereby producing a high thermal conductivity composite film having a needle-punched perforated structure with a pore size of 0.05-1 mm and a pore spacing of 0.1-1 mm; In step 3), the needle punching hot calendering process is as follows: temperature 100-300°C, pressure 1-30 MPa, and calendering speed 0.01-10 m / min; The fiber film layer is an electrospun fiber film made of TPU, PU, polyvinylidene fluoride PVDF, polyolefin POE, polyvinyl alcohol PVA spinnable material, or is one of non-woven fabrics, woven fabrics, fiber felt, and carbon fiber cloth, with a fiber diameter of 50nm-50μm and a surface density of 10-30g / m 2 .

2. The high thermal conductivity composite film with needle-punched open-pore structure according to claim 1, characterized in that: The zero-dimensional thermal conductive filler is one of spherical aluminum oxide Al2O3 and spherical aluminum nitride AlN, and its particle size is 500nm-100μm.

3. The high thermal conductivity composite film with needle-punched open-pore structure according to claim 1, characterized in that: The one-dimensional thermal conductive filler is one of carbon nanotubes CNTs, carbon nitride nanotubes CNNTs, silicon carbide nanowires SiCNWs, and silver nanowires AgNWs, and has a length of 10 μm-200 μm.

4. The high thermal conductivity composite film with needle-punched open-pore structure according to claim 1, characterized in that: The two-dimensional thermal conductive filler is one of boron nitride nanosheets BNNs, graphene nanosheets GNPs, and MXene, and has a particle size of 100nm-5μm and a thickness of 5nm-800nm.

5. The high thermal conductivity composite film with needle-punched open-pore structure according to claim 1, characterized in that: The special-shaped heat-conductive filler is one of tetrapod-shaped zinc oxide ZnO and expanded graphite EG, and its particle size is 500nm-100μm.

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