Phase change capsule-oriented boron nitride array composite film with high enthalpy value and high thermal conductivity as well as preparation method and application of phase change capsule-oriented boron nitride array composite film

Abstract

The invention discloses a phase change capsule-oriented boron nitride array composite film with a high enthalpy value and high heat conductivity as well as a preparation method and application of the phase change capsule-oriented boron nitride array composite film. The phase change capsule-oriented boron nitride array composite film with the high enthalpy value and the high heat conductivity comprises a boron nitride film and a phase change nanocapsule reinforced silicon rubber film which are sequentially stacked; the phase-change nanocapsule reinforced silicone rubber film comprises the following components in percentage by mass: 10%-84% of phase-change nanocapsules and 16%-90% of silicone rubber. The phase change capsule-oriented boron nitride array composite film with high enthalpy value and high thermal conductivity prepared by the invention has high heat storage and high thermal conductivity, is applied to an electronic device, ensures that the electronic device has excellent heat dissipation performance, solves the problem that the electronic device cannot quickly dissipate heat under an extreme working condition in the prior art, and improves the heat dissipation efficiency of the electronic device. The invention is suitable for the technical field of heat-storage heat-transfer materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of phase change materials, and in particular relates to a phase change capsule-oriented boron nitride array composite film with high enthalpy and high thermal conductivity, and a preparation method and application thereof. Background Art

[0002] In recent years, as electronic devices have become increasingly popular around the world, the heat dissipation performance of electronic devices has also begun to attract people's attention. Therefore, the preparation of a high-enthalpy, high-thermal conductivity phase change composite material that provides efficient thermal management has become the goal of scientists at present. Phase change material (PCM) is a substance that can store and release latent heat during the phase change process. It can be divided into solid-liquid PCMs, solid-gas PCMs and liquid-gas PCMs. Among them, the preparation process of solid-liquid PCMs is a relatively mature technology. However, during the process of solid-liquid phase change materials changing from solid phase to liquid phase, leakage will occur. In order to overcome this shortcoming in practical applications, scientists have proposed mixing solid-liquid phase change materials (such as paraffin) with polymers and forming stable composite materials after curing. However, after long-term use, these composite materials still leak after multiple hot and cold cycles. Therefore, in subsequent experiments, scientists tried to encapsulate the phase change material and then mix it with the polymer. It was found that the leakage problem was solved and it still had excellent heat storage capacity. Due to its excellent mechanical properties, thermal conductivity and thermal stability, inorganic shell phase change capsules have become one of the popular options for scientists to prepare composite materials with high enthalpy and high thermal conductivity. However, the composite of phase change capsules and polymer matrix faces the problem of unsatisfactory thermal conductivity and cannot meet the problem of rapid heat dissipation of electrical components such as chips.

[0003] China's public patent number CN116970372A discloses a method for preparing a composite phase change material made of phase change nanocapsules, carbon fibers attached with polydopamine, and polydimethylsiloxane, and obtains a composite phase change thermal conductive material with good mechanical properties and flexibility. China's public patent number CN115725182B discloses a method for preparing a silicone rubber composite material of phase change nanocapsules / boron nitride hybrid fillers, which uses an electrostatic self-assembly method to obtain a hybrid filler of phase change nanocapsules and high thermal conductivity materials, and then introduces it into a polymer matrix to obtain a phase change composite material with good thermal conductivity. However, the mechanical properties and thermal conductivity of the phase change materials obtained in the above patents are not ideal.

[0004] At present, adding high thermal conductivity fillers (such as boron nitride) to the compound of phase change capsules and polymer matrix is ​​a popular solution to optimize the insufficient thermal conductivity of composite phase change materials. However, the added high thermal conductivity fillers (such as boron nitride) are usually not ideally compatible with the polymer matrix and have large phonon scattering, which also leads to a large interfacial thermal resistance between the two. And when the filler content increases, the compound will have problems with inability to solidify and demold. In addition, there is still no good connection between the high thermal conductivity filler and the silica shell phase change capsule (with rich hydroxyl groups on the surface) after surface modification and optimization, and the interfacial thermal resistance is still large, and it is impossible to obtain a composite material with both excellent heat storage and thermal conductivity. Summary of the invention

[0005] In view of this, in order to overcome the existing technical defects, the purpose of the present invention is to provide a high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film suitable for thermal management of electronic devices and its preparation method and application, so as to solve the problem that the phase change material in the prior art has poor thermal conductivity during work and cannot dissipate heat quickly, and is suitable for the field of heat storage and heat transfer material technology.

[0006] The polymer matrix of the present invention is a two-component silicone rubber adhesive, which tightly adheres the phase change nanocapsules to improve the loading rate of the phase change nanocapsules, and vertically constructs a heat conduction network through a stacking method to obtain a phase change composite material film with excellent heat storage and release performance and ideal thermal conductivity.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A phase-change capsule-oriented boron nitride array composite film with high enthalpy and high thermal conductivity, comprising a boron nitride film and a phase-change nano-capsule reinforced silicone rubber film stacked in sequence;

[0009] The phase-change nano-capsule reinforced silicone rubber film comprises, by mass fraction, 10% to 84% of phase-change nano-capsules and 16% to 90% of silicone rubber.

[0010] Preferably, the phase-change nanocapsule reinforced silicone rubber film comprises 75% to 84% of phase-change nanocapsules and 16% to 25% of silicone rubber by mass fraction.

[0011] Preferably, the high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film comprises, by mass fraction, 2.7% to 75.9% phase change nanocapsules, 10.7% to 72.7% boron nitride film and 4.1% to 80.4% silicone rubber (total 100%).

[0012] Preferably, the boron nitride film comprises 92-95% hexagonal boron nitride by mass fraction, and the remainder is resin. The boron nitride of the present invention is obtained by mixing and bonding with resin.

[0013] Further preferably, the boron nitride film comprises 92% hexagonal boron nitride by mass.

[0014] Preferably, the phase-change nanocapsules include paraffin and silicon dioxide; the silicon dioxide is a shell layer, coating the paraffin;

[0015] Further preferably, the phase change nanocapsules include 64% to 73% paraffin and 27% to 36% silicon dioxide in terms of mass percentage.

[0016] Preferably, the silicone rubber is obtained by curing FG-823A and FG-823B in a mass ratio of 1:1.

[0017] Preferably, the thickness of the boron nitride film is 0.03 to 0.2 mm, and the thickness of the phase-change nanocapsule reinforced silicone rubber film is 0.3 to 1 mm;

[0018] Preferably, the boron nitride film is a single piece of boron nitride or a plurality of boron nitride sheets stacked together.

[0019] Further preferably, the multiple pieces of boron nitride are bonded by silicone rubber.

[0020] Preferably, the total thickness of the high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film is 2 to 3 cm.

[0021] Preferably, the boron nitride film and the phase-change nanocapsule reinforced silicone rubber film are bonded by silicone rubber.

[0022] The phase change enthalpy value of the high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film of the present invention is 3.8-136.6 J / g, and the thermal conductivity in the vertical stacking direction is 3.23-12.17 W / (m·K).

[0023] The method for preparing the above-mentioned high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film comprises the following steps:

[0024] The silicone rubber precursor is evenly coated on both sides of the boron nitride film, and the phase change nanocapsule reinforced silicone rubber film and the boron nitride film coated with the silicone rubber precursor on the surface are cross-stacked, and after curing, the high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film is obtained.

[0025] Preferably, the cross stacking is a layer of phase change nanocapsule reinforced silicone rubber film and a layer of boron nitride film coated with a silicone rubber precursor, which are cross-stacked repeatedly until the desired thickness is reached;

[0026] A layer of boron nitride film with a silicone rubber precursor coated on its surface is obtained by stacking a piece of boron nitride with a silicone rubber precursor coated on both sides or a plurality of pieces of boron nitride with a silicone rubber precursor coated on both sides.

[0027] Preferably, the curing temperature is 120-130° C., the pressure is 90-110 kPa, and the time is 1 h to 2 h.

[0028] Preferably, the method for preparing the phase-change nanocapsule reinforced silicone rubber film comprises the following steps:

[0029] Dispersing phase-change nanocapsules and silicone rubber precursors in a dispersant, heating and curing, and obtaining a phase-change nanocapsule reinforced silicone rubber film;

[0030] More preferably, the heating curing temperature is 120-130° C., the pressure is 90-110 kPa, and the time is 1-4 hours.

[0031] Further preferably, the dispersant is ethanol or n-hexane.

[0032] Further preferably, the mass ratio of the phase change nanocapsules to the silicone rubber precursor is 10-84:16-90.

[0033] Further preferably, the silicone rubber precursor includes FG-823A and FG-823B in a mass ratio of 1:1.

[0034] Further preferably, the phase change nanocapsules are prepared by an interfacial hydrolysis-condensation method;

[0035] Further preferably, the method for preparing the phase change nanocapsule comprises the following steps:

[0036] CTAB (hexadecyltrimethylammonium bromide) is dissolved in a mixed solvent consisting of anhydrous ethanol and deionized water, and stirred at a constant temperature of 60-70° C., and a mixture of paraffin wax and ethyl orthosilicate at 60-70° C. is added to obtain an O / W emulsion; the O / W emulsion is homogenized, and an ammonia initiator is added to stir the reaction, and the mixture is aged, filtered, washed, and dried to obtain phase change nanocapsules.

[0037] More preferably, the mass ratio of CTAB to tetraethyl orthosilicate is 41-50:500;

[0038] More preferably, the volume ratio of anhydrous ethanol to deionized water in the mixed solvent is 355-400:713;

[0039] More preferably, the ratio of the mass of CTAB to the volume of the mixed solvent is 0.82-1 g:106.8 mL;

[0040] More preferably, the mass ratio of the paraffin wax to tetraethyl orthosilicate is 64-73:27-36.

[0041] More preferably, the homogenization speed is 10000-12000 rpm; the homogenization time is 10-15 minutes;

[0042] More preferably, the stirring speed of the stirring reaction is 350-400 rpm; the time of the stirring reaction is 16-20 h; and the temperature of the stirring reaction is 60-70°C.

[0043] More preferably, the aging time is 12 to 15 hours, and the aging temperature is 60 to 70°C.

[0044] The particle size of the phase-change nanocapsule of the invention is 500-1000nm, the phase-change temperature is 42-52°C, and the phase-change latent heat is 120-180J / g.

[0045] The application of the above-mentioned high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film in thermal management of electronic devices.

[0046] A thermal management device for electronic devices made from the above-mentioned high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film, wherein the high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film is attached to the surface of the single or multiple electronic devices in the stacking direction.

[0047] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0048] (1) The present invention uses a mechanical stirring method to compound the phase change nanocapsules into the pores of the two-component silicone rubber matrix, and can prepare a high-enthalpy phase change nanocapsule film with a high capsule loading.

[0049] (2) The present invention arranges hexagonal boron nitride flakes as thermal conductive fillers in a vertical orientation and compounds them with a phase change nanocapsule / silicone rubber mixture to obtain a composite material with oriented high thermal conductivity and high enthalpy value. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a SEM image of the phase change nanocapsules prepared in step (1) of Example 1 of the present invention.

[0051] Figure 2 This is the DSC graph of the phase change nanocapsules prepared in step (1) of Example 1 of the present invention.

[0052] Figure 3 TG curve of the phase change nanocapsules prepared in step (1) of Example 1 of the present invention.

[0053] Figure 4 This is a SEM image of the phase change nanocapsule reinforced silicone rubber film prepared in step (2) of Example 1 of the present invention.

[0054] Figure 5 It is a schematic diagram of the preparation process of the phase change capsule-oriented boron nitride array composite film with high enthalpy and high thermal conductivity of the present invention.

[0055] Figure 6 It is a schematic diagram of the finished product of the phase change capsule-oriented boron nitride array composite film with high enthalpy and high thermal conductivity of the present invention.

[0056] Figure 7 This is a physical picture of the high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film prepared in step (4) of Example 1 of the present invention. DETAILED DESCRIPTION

[0057] The present invention is described in detail below in conjunction with examples, but the implementation manner and protection scope of the present invention are not limited to the following examples.

[0058] The steps for preparing the high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film of the present invention are as follows:

[0059] Synthesis of phase-change nanocapsules: Dissolve CTAB in a mixed solvent of anhydrous ethanol and deionized water and stir at 60°C. Add a mixture of paraffin and ethyl orthosilicate melted in advance at 60°C to the solution to obtain an O / W emulsion. Homogenize the O / W emulsion at 10,000 rpm for 10 minutes using a homogenizer. Then, place the emulsion in a preheated three-necked flask and stir at 350 rpm for 5 minutes before adding ammonia initiator. Keep the reaction at 350 rpm for 16 hours, age for 12 hours, filter, wash, and dry to obtain nano phase-change capsules.

[0060] Preparation of thermally conductive enhanced polymer film containing phase change microcapsules: Stir the prepared silica phase change nanocapsules and two-component mixed silicone rubber in a planetary mixer according to a predetermined program for 10 minutes under ethanol dispersant to evenly mix the silica phase change nanocapsules and the two-component mixed silicone rubber, then fill the mixed filler into the mold, flatten the surface, and then heat and cure at 120°C and 90-110kPa for 4 hours. After curing, demould while hot, and obtain a phase change nanocapsule enhanced silicone rubber film after demoulding.

[0061] Preparation of high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film: Use a fiber laser marking machine to cut the boron nitride film into small thin slices according to the length and width of the mold, and evenly apply the two-component mixed silicone rubber on the cut boron nitride film. The thermally conductive enhanced polymer film containing phase change microcapsules and the boron nitride film coated with a thin layer of two-component mixed silicone rubber on the surface are neatly stacked, and a composite film is matched with a piece (or multiple pieces) of boron nitride film, and the stacking is repeated crosswise until the required sample thickness is reached. Then, the laminated structure of the phase change nanocapsule enhanced silicone rubber film / boron nitride film composite material is cured at 120°C for 2h. After curing, slice along the vertical direction of the stacked layer to obtain the high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film.

[0062] Example 1

[0063] (1) Prepare 15g paraffin and 10g TEOs and put them into beaker 1, seal it with plastic wrap, and then heat it on a heating plate at 60℃ until it melts. While the paraffin is heating, weigh 0.82g CTAB, 35.5ml anhydrous ethanol, and 71.3ml deionized water into beaker 2, seal it with plastic wrap, and heat it in a water bath on a heating plate to 60℃. Subsequently, pour the melted paraffin into beaker 2, homogenize it at 10000rpm at 60℃ for 10min, then put the emulsion into a preheated three-necked flask, stir it at 350rpm at 60℃ for 5min, and then add 1.5ml ammonia water (15wt%) as initiator. Keep 350rpm and 60℃ for 16h, age it at 60℃ for 12h, filter, wash, and dry to obtain silica phase change nanocapsules.

[0064] (2) Add 8g of silica phase change nanocapsules, 8ml of ethanol, and 2g of two-component mixed silicone rubber (Smooth-On, Ecoflex 00-30: a-gel FG-823A, b-gel FG-823B, mass ratio 1:1) into a mixing cup, stir for 10 minutes in a planetary mixer according to a predetermined program, and then fill the mixed filler into a mold with a length, width and height of 20mm×20mm×0.6mm, and then heat and cure at 120℃ and 110kPa for 4h. After curing, demold while hot, and a 0.6mm thick phase change nanocapsule reinforced silicone rubber film is obtained after demolding.

[0065] (3) Use a fiber laser marking machine to cut a 0.1 mm thick boron nitride film (Guangdong Shengpeng Technology Co., Ltd., SPA-TF40, boron nitride content 92 wt%) into 20 mm × 20 mm small pieces, and evenly apply the two-component mixed silicone rubber on both sides of the cut boron nitride film.

[0066] (4) The phase change nanocapsule reinforced silicone rubber film and the boron nitride film coated with a two-component mixed silicone rubber thin layer are neatly stacked, with one phase change nanocapsule reinforced silicone rubber film and one boron nitride film on the top and bottom, and the stacking is repeated until it reaches 16.8 mm (21 layers). Then, the laminated phase change nanocapsule reinforced silicone rubber film / boron nitride film composite material is heated and cured at 120°C and 110 kPa for 2 hours. After curing, the stacked layers are sliced ​​vertically to obtain a phase change capsule-oriented boron nitride array composite film with a high enthalpy value and high thermal conductivity of 1 mm thick.

[0067] The SEM image of the silica phase change nanocapsules prepared in step (1) is as follows: Figure 1 , DSC diagram Figure 2 TG curve is as follows Figure 3 .from Figure 1 It can be seen that ethyl orthosilicate hydrolyzes under alkaline conditions to form a compact silica shell, which wraps the core paraffin wax, forming a phase-change nanocapsule with a smooth surface and a particle size of 500 nm. Figure 2 It can be seen that the phase change temperature of the phase change nanocapsule in the present invention is 42.73° C., and the phase change enthalpy value is as high as 160.2 J / g. Figure 3 The TG curve in the figure shows the excellent thermal stability of the phase change nanocapsule. Its thermal decomposition point is 231.2°C, which is 35°C higher than that of paraffin. This is because the thermal conductivity of the silica shell on its surface is low, which isolates the impact of high-intensity heat flow from the outside world on the paraffin wrapped in it and plays a protective role.

[0068] The SEM image of the phase change nanocapsule reinforced silicone rubber film prepared in step (2) is as follows: Figure 4 It can be seen that the silicone rubber wraps the phase change nanocapsules intactly. The raised spheres in the figure are the phase change nanocapsules compounded into the silicone rubber.

[0069] Step (4) The schematic diagram of the preparation process of the high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film is as follows Figure 5 , the heat conduction direction mechanism diagram is as follows Figure 6 , the actual picture is as follows Figure 7 (The left and middle pictures are sliced ​​samples, and the right picture is a block sample). It can be seen that after Figure 5 Process stacking and compounding can be obtained Figure 7 The boron nitride sheets and nanocapsule-reinforced silicone rubber films shown are alternately and closely arranged in layers to form a high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film.

[0070] The thermal conductivity of the hexagonal boron nitride (h-BN) film measured and announced by the manufacturer through experiments is 40W / (m·K), and its latent heat is measured by differential scanning calorimetry to be 0J / g.

[0071] Phase change nanocapsule reinforced silicone rubber film was prepared by thermal flow method Figure 6 The thermal conductivity of the x-axis orientation was tested to be 0.25 W / (m·K), and the latent heat was measured by differential scanning calorimetry to be 134.2 J / g.

[0072] Through calculation, the theoretical thermal conductivity is 10.2W / (m·K) and the theoretical latent heat is 118.4J / g.

[0073] The high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film was studied by heat flow method. Figure 6 The thermal conductivity of the x-axis orientation was tested to be 5.59 W / (m·K), and the latent heat was measured to be 114.4 J / g by differential scanning calorimetry.

[0074] Example 2

[0075] (1) Prepare 15g paraffin and 10g TEOs and put them into beaker 1, seal it with plastic wrap, and then heat it on a heating plate at 60℃ until it melts. While the paraffin is heating, weigh 0.82g CTAB, 35.5ml anhydrous ethanol, and 71.3ml deionized water into beaker 2, seal it with plastic wrap, and heat it in a water bath on a heating plate to 60℃. Subsequently, pour the melted paraffin into beaker 2, homogenize it at 10000rpm at 60℃ for 10min, then put the emulsion into a preheated three-necked flask, stir it at 350rpm at 60℃ for 5min, and then add 1.5ml ammonia water (15wt%) as initiator. Keep 350rpm and 60℃ for 16h, age it at 60℃ for 12h, filter, wash, and dry to obtain silica phase change nanocapsules.

[0076] (2) Add 8g of silica phase change nanocapsules, 8ml of ethanol, and 2g of two-component mixed silicone rubber (Smooth-On, Ecoflex 00-30: a-gel FG-823A, b-gel FG-823B, mass ratio 1:1) into a mixing cup, stir for 10 minutes in a planetary mixer according to a predetermined program, and then fill the mixed filler into a mold with a length, width and height of 20mm×20mm×0.6mm, and then heat and cure at 120℃ and 110kPa for 4h. After curing, demold while hot, and a 0.6mm thick phase change nanocapsule reinforced silicone rubber film is obtained after demolding.

[0077] (3) Use a fiber laser marking machine to cut a 0.1 mm thick boron nitride film into 20 mm × 20 mm small slices, and evenly apply the two-component mixed silicone rubber on both sides of the cut boron nitride film.

[0078] (4) The conductive phase change nanocapsule reinforced silicone rubber film and the boron nitride film coated with a two-component mixed silicone rubber thin layer are neatly stacked, one composite film is matched with one boron nitride film, and the stacking is repeated crosswise until it reaches 16.8 mm (24 layers). Then, the laminated phase change nanocapsule reinforced silicone rubber film / boron nitride film composite material is heated and cured at 120°C and 110 kPa for 2 hours. After curing, the stacked layers are sliced ​​vertically to obtain the phase change capsule-oriented boron nitride array composite film with a thickness of 1 mm and a high enthalpy and high thermal conductivity.

[0079] The thermal conductivity of the hexagonal boron nitride (h-BN) film measured and announced by the manufacturer through experiments is 40W / (m·K), and its latent heat is measured by differential scanning calorimetry to be 0J / g.

[0080] Phase change nanocapsule reinforced silicone rubber film was prepared by thermal flow method Figure 6 The thermal conductivity of the x-axis orientation was tested to be 0.25 W / (m·K), and the latent heat was measured by differential scanning calorimetry to be 134.2 J / g.

[0081] Through calculation, the theoretical thermal conductivity is 5.93W / (m·K) and the theoretical latent heat is 125.8J / g.

[0082] The material was subjected to heat flow Figure 6 The thermal conductivity of the x-axis orientation was tested and the thermal conductivity was 3.50 W / (m·K). The latent heat was measured by differential scanning calorimetry to be 125.3 J / g.

[0083] Example 3

[0084] (1) Prepare 15g paraffin and 10g TEOs and put them into beaker 1, seal it with plastic wrap, and then heat it on a heating plate at 60℃ until it melts. While the paraffin is heating, weigh 0.82g CTAB, 35.5ml anhydrous ethanol, and 71.3ml deionized water into beaker 2, seal it with plastic wrap, and heat it in a water bath on a heating plate to 60℃. Subsequently, pour the melted paraffin into beaker 2, homogenize it at 10000rpm at 60℃ for 10min, then put the emulsion into a preheated three-necked flask, stir it at 350rpm at 60℃ for 5min, and then add 1.5ml ammonia water (15wt%) as initiator. Keep 350rpm and 60℃ for 16h, age it at 60℃ for 12h, filter, wash, and dry to obtain silica phase change nanocapsules.

[0085] (2) Add 6g of silica phase change nanocapsules, 6ml of ethanol, and 4g of two-component mixed silicone rubber (Smooth-On, Ecoflex 00-30: a-gel FG-823A, b-gel FG-823B, mass ratio 1:1) into a mixing cup, stir for 10 minutes in a planetary mixer according to a predetermined program, and then fill the mixed filler into a mold with a length, width and height of 20mm×20mm×0.6mm, and then heat and cure at 120℃ and 110kPa for 4h. After curing, demold while hot, and a 0.6mm thick phase change nanocapsule reinforced silicone rubber film is obtained after demolding.

[0086] (3) Use a fiber laser marking machine to cut a 0.1 mm thick boron nitride film into 20 mm × 20 mm small slices, and evenly apply the two-component mixed silicone rubber on both sides of the cut boron nitride film.

[0087] (4) The conductive phase change nanocapsule reinforced silicone rubber film and the boron nitride film coated with a two-component mixed silicone rubber thin layer are neatly stacked, one composite film is matched with one boron nitride film, and the stacking is repeated crosswise until it reaches 16.8 mm (24 layers). Then, the laminated phase change nanocapsule reinforced silicone rubber film / boron nitride film composite material is heated and cured at 120°C and 110 kPa for 2 hours. After curing, the stacked layers are sliced ​​vertically to obtain the phase change capsule-oriented boron nitride array composite film with a thickness of 1 mm and a high enthalpy and high thermal conductivity.

[0088] The thermal conductivity of the hexagonal boron nitride (h-BN) film measured and announced by the manufacturer through experiments is 40W / (m·K), and its latent heat is measured by differential scanning calorimetry to be 0J / g.

[0089] Phase change nanocapsule reinforced silicone rubber film was prepared by thermal flow method Figure 6 The thermal conductivity of the x-axis orientation was tested to be 0.255 W / (m·K), and the latent heat was measured to be 100.2 J / g by differential scanning calorimetry.

[0090] Through calculation, the theoretical thermal conductivity is 5.93W / (m·K) and the theoretical latent heat is 93.9J / g.

[0091] The material was subjected to heat flow Figure 6 The thermal conductivity of the x-axis orientation was tested and the thermal conductivity was 3.52 W / (m·K). The latent heat was measured by differential scanning calorimetry to be 89.7 J / g.

Claims

1. A phase change capsule-oriented boron nitride array composite film with high enthalpy and high thermal conductivity, characterized in that: It includes a boron nitride film and a phase-change nano-capsule reinforced silicone rubber film stacked in sequence; The phase-change nano-capsule reinforced silicone rubber film comprises, by mass fraction, 10% to 84% of phase-change nano-capsules and 16% to 90% of silicone rubber.

2. The high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film according to claim 1, characterized in that: The boron nitride film comprises 92-95% hexagonal boron nitride by mass fraction; The phase-change nanocapsules include paraffin and silicon dioxide; the silicon dioxide is a shell layer covering the paraffin; The silicone rubber is obtained by curing FG-823A and FG-823B in a mass ratio of 1:

1.

3. The high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film according to claim 2, characterized in that: Calculated by mass percentage, the phase-change nanocapsule comprises 64% to 73% paraffin and 27% to 36% silicon dioxide.

4. The high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film according to claim 1, characterized in that: The thickness of the boron nitride film is 0.03 to 0.2 mm, and the thickness of the phase-change nanocapsule-reinforced silicone rubber film is 0.3 to 1 mm; The boron nitride film and the phase-change nano-capsule reinforced silicone rubber film are bonded by silicone rubber.

5. The method for preparing the high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film according to any one of claims 1 to 4, characterized in that: The following steps are involved: The silicone rubber precursor is evenly coated on both sides of the boron nitride film, and the phase change nanocapsule reinforced silicone rubber film and the boron nitride film coated with the silicone rubber precursor on the surface are cross-stacked, and after curing, the high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film is obtained.

6. The preparation method according to claim 5, characterized in that: The cross stacking is to cross-stack a layer of phase-change nanocapsule reinforced silicone rubber film with a layer of boron nitride film coated with a silicone rubber precursor until the desired thickness is reached; The curing temperature is 120-130° C., the pressure is 90-110 kPa, and the curing time is 1 h to 2 h.

7. The preparation method according to claim 5, characterized in that: The preparation method of the phase-change nanocapsule reinforced silicone rubber film comprises the following steps: Dispersing phase-change nanocapsules and silicone rubber precursors in a dispersant, heating and curing, and obtaining a phase-change nanocapsule reinforced silicone rubber film; The heating curing temperature is 120-130°C, the pressure is 90-110 kPa, and the time is 1-4 hours; The dispersant is ethanol or n-hexane.

8. The preparation method according to claim 7, characterized in that: The phase-change nanocapsules are prepared by an interfacial hydrolysis-polycondensation method; The preparation method of the phase-change nanocapsule comprises the following steps: The CTAB is dissolved in a mixed solvent consisting of anhydrous ethanol and deionized water, and the mixture is stirred at a constant temperature of 60-70° C., and a mixture of paraffin wax and ethyl orthosilicate at 60-70° C. is added to obtain an O / W emulsion; the O / W emulsion is homogenized, and an ammonia initiator is added to stir the reaction, and the mixture is aged, filtered, washed, and dried to obtain phase change nanocapsules.

9. The preparation method according to claim 8, characterized in that: The mass ratio of CTAB to tetraethyl orthosilicate is 41-50:500; The volume ratio of anhydrous ethanol to deionized water in the mixed solvent is 355-400:713; The ratio of the mass of CTAB to the volume of the mixed solvent is 0.82-1 g:106.8 mL; The mass ratio of the paraffin wax to ethyl orthosilicate is 64-73:27-36.

10. Application of the high enthalpy and high thermal conductivity phase change capsule-oriented boron nitride array composite film according to any one of claims 1 to 4 in thermal management of electronic devices.

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