Conductive and thermally conductive hydrophobic polymer composite films, their preparation methods and applications

Abstract

A conductive and thermally conductive hydrophobic polymer composite membrane, its preparation method, and its application are disclosed. The method involves preparing a PU nanofiber membrane using electrospinning technology. Subsequently, AgNPs are adsorbed onto the surface of the PU nanofibers via interfacial hydrogen bonding, effectively reducing contact thermal resistance and electrical resistance. MWCNTs are then attached to the upper and lower surfaces of the composite membrane through filtration and hot pressing, forming a sandwich structure that further reduces electrical and thermal resistance while maintaining hydrophobicity. The polymer composite membrane of this invention achieves an electrical resistance of 14.8 mΩ / sq and a thermal conductivity of 7.9 W (mK). ‑1 The water contact angle is 132.8°. Strong interfacial interactions ensure the excellent durability of the composite film, making it a promising candidate for application in multifunctional conductive and thermally conductive composite materials.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer materials, and relates to a conductive and thermally conductive hydrophobic polymer composite film, its preparation method, and its application. Background Technology

[0002] Conductive and thermally conductive polymer fiber / fabric composites (CPFCs) possess properties such as light weight, low cost, good flexibility, and excellent breathability, and are rapidly developing due to their potential applications in flexible and wearable electronics. The manufacture of CPFCs typically involves constructing a conductive and thermally conductive network within a polymer fiber / fabric membrane. Hybrid electrospinning is a method for directly preparing conductive and thermally conductive polymer fiber composites. For example, by mixing polyimide (PI) with thermally conductive SiN to form a homogeneous solution, followed by electrospinning, the thermally conductive SiN is arranged according to the fiber structure to form a complete thermally conductive network, while inheriting the excellent thermal stability, chemical resistance, radiation resistance, and mechanical properties of the PI matrix. When the SiN content is 35 wt.%, the heat transfer efficiency of a single fiber is increased by ~25% compared to pure PI fiber (Moradi, et al. Bridging agap in thermal conductivity and heat transfer in hybrid fibers and yarns via polyimide and silicon nitride composites. Small, 2023, 19(52): 2305-104.). However, when conductive or thermally conductive fillers are mixed in a solution for electrospinning, nanoparticles (especially at high concentrations) tend to aggregate, significantly increasing solution viscosity and thus deteriorating processing performance, and also leading to a decrease in the mechanical properties of the fiber membrane. To address this issue, conductive and thermally conductive nanofillers are assembled onto the fiber surface through interfacial interactions such as hydrogen bonding, electrostatic forces, and interfacial sintering. The resulting core-shell structure maintains the good flexibility of the polymer fiber membrane, prevents the aggregation of conductive particles, and constructs a more effective conductive and thermally conductive network. For example, MXene nanosheets with abundant functional groups (such as fluorine-containing groups) can be assembled onto the fiber surface by dip-coating. Conductive nanofillers without surface functional groups can also be modified onto fibers using ultrasonic-assisted interfacial sintering. First, carbon nanomaterials such as reduced graphene oxide, carbon nanotubes, and carbon nanofibers are dispersed in a solvent. Then, an ultrasonic field drives these rigid nanofillers to impact the soft nanofibers at high speed, generating interfacial adhesion. The nanofillers are then fixed at the impacted sites of the nanofibers.Ma et al. reported a method for preparing core / shell conductive nanofibers using an impregnation method. They coated the fiber surface with multi-walled carbon nanotubes (MWCNTs) and then annealed the fiber to further enhance the interfacial interaction between the conductive shell and the internal fibers, as well as between the MWCNTs. The mechanical properties of the composite film also increased with the increase of MWCNT content, which is mainly due to the enhanced interfacial interaction between the components inside the composite material. By adjusting the experimental conditions, the resistivity of the obtained fibers could be controlled between 732 and 30 Ω / sq (Ma, et al. Preparation of core / shell electrically conductive fibers by efficient coating carbon nanotubes on polyester. Advanced Fiber Materials, 2021, 3(3): 180-91.). Whether surface-assembled or sintered, the conductive shell of the polymer fiber is usually very thin, corresponding to a relatively low concentration of nanofillers, resulting in low thermal conductivity and electrical conductivity. Summary of the Invention

[0003] Technical Problem Solved: This invention provides a conductive and thermally conductive hydrophobic polymer composite film, its preparation method, and its applications. By constructing a sandwich structure, a composite film possessing excellent electrical conductivity, thermal conductivity, and hydrophobicity is prepared. Spherical silver nanoparticles (AgNPs) are uniformly modified on the surface of polyurethane (PU) nanofibers. Subsequently, multilayer ceramic nanoparticles (MWCNTs) are deposited on the upper and lower surfaces of the nanofiber film, and hot pressing is used to improve interlayer interactions and the mechanical properties of the composite material. At this point, the composite film exhibits low electrical resistance and high thermal conductivity, making it suitable for use as a thermal interface material. Furthermore, MWCNTs also impart good hydrophobicity to the composite film (water contact angle of 132.8°).

[0004] Technical Solution: A method for preparing a conductive and thermally conductive hydrophobic polymer composite film, comprising the following steps: Step 1, adding polyurethane (PU) to a mixture of tetrahydrofuran (THF) and N,N-dimethylformamide (DMF) as a spinning solution, wherein the mass fraction of PU is 10-15 wt.% of the total mass, and the mass ratio of THF to DMF solution is 1:4, and obtaining a polymer nanofiber film by electrospinning; Step 2, drying the polymer nanofiber film to remove residual THF and DMF, then immersing it in a dopamine (DA) solution, and drying it after immersion to obtain a composite material with a surface covered by polydopamine (PDA); Step 3, immersing the PDA-covered composite material in an AgNO3 solution, and then passing it through C6H... 12After reducing AgNO3 with O6 solution, the membrane is dried to obtain a conductive and thermally conductive polymer nanofiber composite membrane with AgNPs coated on the fiber surface. In step 4, a layer of multi-walled carbon nanotubes (MWCNTs) is deposited on the upper and lower surfaces of the conductive and thermally conductive polymer nanofiber composite membrane by vacuum filtration, followed by hot pressing to obtain a conductive and thermally conductive hydrophobic polymer composite membrane with a sandwich structure.

[0005] Preferably, in step 1, the spinning voltage is 15kV, the liquid inlet rate is 2mL / h, and the distance between the needle and the receiver is 12cm.

[0006] Preferably, in step 2, the concentration of the DA solution is 2-4 mg / mL, the pH of the PDA solution is 8-8.5, the soaking time is 6-8 hours, and the soaking temperature is 40-45℃.

[0007] Preferably, in steps 2 and 3, the drying temperature is 30-60℃.

[0008] Preferably, in step 3, the concentration of the AgNO3 solution is 20 mg / mL, and the C6H... 12 The concentration of the O6 solution is 80 mg / mL, and the soaking time is 2-5 hours.

[0009] Preferably, in step 4, the diameter of the sand core used for filtration is 40 mm, the MWCNTs are dispersed in a mixed solvent of ethanol and water with a volume ratio of ethanol to water of 1:1, the concentration of MWCNTs is 1 mg / mL, the hot pressing temperature is 60-120℃, and the hot pressing time is 15 min.

[0010] The above preparation method yields a conductive and thermally conductive hydrophobic polymer composite film.

[0011] The above-mentioned conductive and thermally conductive hydrophobic polymer composite film is used in the preparation of multifunctional conductive and thermally conductive composite materials.

[0012] This invention constructs an AgNPs network in a PU matrix by relying on hydrogen bonds, thereby achieving a conductive and thermally conductive network. Subsequently, through filtration and hot pressing, MWCNTs are attached to the upper and lower surfaces of the composite membrane to construct a sandwich structure, forming a more complete conductive and thermally conductive network while giving it better hydrophobicity.

[0013] Beneficial effects: (1) This invention combines metal ion adsorption and reduction, vacuum filtration and hot pressing technology to construct a unique sandwich structure, which effectively reduces interfacial thermal resistance and electrical resistance, and realizes the functionalization of composite fiber membranes. The electrical resistance is reduced to 14.8 mΩ / sq, while the thermal conductivity reaches 7.9 W(m·K). -1 The composite fiber membrane has good hydrophobicity, with a water contact angle of 132.8°.

[0014] (2) This invention improves the interfacial strength between nanoparticles and polymer matrix through multiple interfacial interactions (interfacial hydrogen bonding and physical adhesion), thereby enhancing the surface stability and durability of the composite fiber membrane.

[0015] (3) The polymer composite film prepared by the present invention has excellent photothermal conversion and electrothermal conversion performance, and can achieve rapid and stable heating effect under standard sunlight and small voltage.

[0016] (4) The polymer composite membrane prepared by the present invention has strain sensing properties and maintains a stable response effect under different tensile strains and tensile rates, and has potential application scenarios in strain sensing. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the preparation process of polymer composite membranes.

[0018] Figure 2 Scanning electron microscope (SEM) images of the composite membrane surface (a) prepared for Comparative Example 1, the dopamine-modified PU surface (b), the composite membrane surface (c) prepared for Comparative Example 2, and the composite membrane surface (d) prepared for Example 1.

[0019] Figure 3 Scanning electron microscope (SEM) images of the composite membrane cross section (a) prepared in Comparative Example 2, the composite membrane cross section (b) prepared in Example 1, and the elemental distribution diagram of the composite membrane cross section (c) prepared in Example 1.

[0020] Figure 4 The stress-strain curves (a) of the polymer composite membranes prepared in Examples 1, 2, 9, 10 and 11, the cyclic tensile curve (b) of the composite membrane prepared in Example 1 and the fatigue resistance curve after 1000 loading-unloading cycles (c) are shown.

[0021] Figure 5 The resistivity comparison diagrams are for the polymer composite films prepared in Examples 1-3 and Comparative Examples 3-11.

[0022] Figure 6 This is a comparison diagram of the horizontal and vertical thermal conductivity of the polymer composite films prepared in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2.

[0023] Figure 7 The images show a comparison of the water contact angles of the polymer composite membranes prepared in Examples 1-3 and Comparative Examples 3-11.

[0024] Figure 8 This is a comparison chart of the photothermal conversion performance under standard sunlight for the polymer composite films prepared in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2.

[0025] Figure 9 The cyclic heating and cooling curves (a), the 1-hour heating curve (b), and the comparison of photothermal conversion performance under different light intensities for the polymer composite film prepared for Experimental Example 1 are shown in Figure (c).

[0026] Figure 10 The current-voltage characteristic curve (a), the heating curve at different voltages (b), and the comparison diagram (c) of the first and tenth heating and cooling cycles of the polymer composite membrane prepared in Example 1 are shown.

[0027] Figure 11 The self-cleaning performance (a) and photothermal de-icing performance (b) of the polymer composite film prepared for Experimental Example 1.

[0028] Figure 12 The resistance response of the polymer composite film prepared in Example 1 under different strains (a), resistance response under different stretching rates (b), real-time detection curve of neck bending resistance change (c), and real-time monitoring curve of elbow bending resistance change (d) are shown.

[0029] Figure 13 (a) Schematic diagram of thermal interface material; (b) Comparison of the cooling effect of the polymer composite film prepared in Example 1 as thermal interface material with that of commercial thermal pads or no thermal interface material on the chip; (c) Comparison of the temperature of different locations of the polymer composite films prepared in Experiment 1, Experiment 2 and Experiment 3 when heated by a point heat source. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the selected embodiments are only for illustrating the present invention and do not limit the scope of the present invention.

[0031] Example 1

[0032] (1) PU was added to a mixture of THF and DMF as the spinning solution. The mass fraction of PU was 15 wt.% of the total mass, and the mass fraction ratio of THF to DMF solution was 1:4. Electrospinning parameters were set as follows: voltage 15 kV, feed rate 2 mL / h, and distance from needle to collection device 12 cm. The obtained fiber membrane was dried in a 60°C oven to remove residual solvent. Dopamine hydrochloride was dissolved in water to prepare a 2 mg / mL dopamine solution, and the pH was adjusted to 8.5. The above fiber membrane was placed in the dopamine solution and soaked for 6 hours. After soaking, it was removed and dried in a 60°C oven for later use. AgNO3 particles were dissolved in water to prepare a 20 mg / mL AgNO3 solution. The above dopamine-modified fiber membrane was placed in the AgNO3 solution, and an equal volume of 80 mg / mL C6H3O3 was added dropwise while stirring. 12After adding O6 solution, the reaction proceeded until the solution became clear. The solution was then removed and dried in a 60°C oven. The AgNPs-loaded fiber membrane was placed on a 40mm sintered stone core. 7mL of MWCNT (1mg / mL) ethanol / water solution was added dropwise to both the upper and lower surfaces (ethanol to water volume ratio 1:1). The membrane was then filtered, and after filtration, dried in a 60°C oven. The hydraulic press was controlled at 100°C and 10MPa, and the composite fiber membrane was hydraulically compressed for 15 minutes. Subsequently, the pressure of the flatbed vulcanizer was adjusted to 15MPa, and compression was performed at room temperature for 2 minutes. The preparation process is as follows: Figure 1 As shown, the microstructure of the prepared composite material is as follows. Figure 2 and Figure 3 As shown.

[0033] (2) Mechanical property testing:

[0034] The samples were cut into dumbbell-shaped strips, 50 mm long and 4 mm wide at the neck, using a cutting tool. The samples were then stretched at a rate of 50 mm / min using a universal testing machine until fracture to determine the strength and elongation at break of different samples. Each sample was tested at least five times. In addition, cyclic loading tests with a fixed strain were performed on the samples using a fatigue tensile testing machine. Figure 4 As shown.

[0035] (3) Conductivity test:

[0036] The sheet resistance of the polymer composite film was tested using an RTS-9 four-probe tester. The test results are as follows: Figure 5 As shown, the resistance of the polymer composite film reaches 14.8 mΩ / sq.

[0037] (4) Thermal conductivity test:

[0038] The vertical thermal conductivity, thermal diffusivity, and parallel thermal diffusivity of the polymer composite film were measured using an LFA 467 thermal conductivity meter. The horizontal thermal conductivity of the polymer nanofiber composite film was calculated. The test results are as follows: Figure 6 As shown, the vertical thermal conductivity reaches 0.9 W / (m·K). -1 The horizontal thermal conductivity reaches 7.9 W / (m·K). -1 .

[0039] (5) Hydrophobicity test:

[0040] The water contact angle of the polymer composite membrane was tested using a contact angle meter, and the test results are as follows: Figure 7 As shown, the water contact angle of the polymer composite membrane reaches 132.8°.

[0041] (6) Photothermal conversion performance test:

[0042] Using a xenon lamp to simulate standard sunlight intensity, the test results are as follows: Figure 8 and Figure 9 As shown, the polymer composite film can be heated to approximately 45°C under standard sunlight.

[0043] (7) Electrothermal conversion performance test:

[0044] A small voltage was applied across the polymer composite film, and the test results are as follows: Figure 10 As shown, the composite membrane can be heated rapidly and stably under low voltage.

[0045] (8) Self-cleaning performance test:

[0046] The polymer composite membrane was tilted and some sand and dust were sprinkled on it. Water droplets naturally fell onto the surface of the polymer composite membrane, and the test results were as follows. Figure 11 As shown, dust is removed from the composite membrane after water flows through it.

[0047] (9) Photothermal de-icing performance test:

[0048] The xenon lamp was adjusted to simulate standard sunlight. The polymer composite film was placed under the light source, and the melting time of the ice on the polymer composite film was observed. The test results are as follows: Figure 11 As shown, the composite membrane can effectively shorten the melting time of ice, and its hydrophobicity prevents water from penetrating into the composite membrane.

[0049] (10) Strain sensing performance test:

[0050] The composite membrane is adhered to the joints of the human body, and human movement is monitored in real time. The test results are as follows: Figure 12 As shown, the composite membrane can respond quickly and stably to human movement.

[0051] (11) Cooling test:

[0052] A polymer composite film was placed between the heating chip and the heat sink to serve as a thermal interface material. Infrared imager was used to record the temperature change on the chip surface during the heating process. The experimental results are as follows: Figure 13 As shown, the composite film effectively transfers heat to the heat sink, thus reducing the chip temperature.

[0053] Example 2

[0054] (1) The preparation of the polymer composite membrane is basically the same as in Example 1, except that the volume of the MWCNT suspension used for filtration is 5 mL.

[0055] (2) Mechanical property testing:

[0056] Cut the sample into dumbbell-shaped strips, 50 mm long and 4 mm wide at the neck, using a cutting tool. Tensile the samples using a universal testing machine at a rate of 50 mm / min until fracture to determine the strength and elongation at break of different samples. Each sample should be tested at least five times. Figure 4 As shown.

[0057] (3) Conductivity test:

[0058] The sheet resistance of the polymer composite film was tested using an RTS-9 four-probe tester. The test results are as follows: Figure 5 As shown, the resistance of the polymer composite film reaches 30 mΩ / sq.

[0059] (4) Thermal conductivity test:

[0060] The vertical thermal conductivity, thermal diffusivity, and parallel thermal diffusivity of the polymer composite film were measured using an LFA 467 thermal conductivity meter. The horizontal thermal conductivity of the polymer nanofiber composite film was calculated. The test results are as follows: Figure 6 As shown, the vertical thermal conductivity reaches 0.4 W / (m·K). -1 The horizontal thermal conductivity reaches 3.6 W / (m·K). -1 .

[0061] (5) Hydrophobicity test:

[0062] The water contact angle of the polymer composite membrane was tested using a contact angle meter, and the test results are as follows: Figure 7 As shown, the water contact angle of the polymer composite membrane reaches 128.1°.

[0063] (6) Photothermal conversion performance test:

[0064] Using a xenon lamp to simulate standard sunlight intensity, the test results are as follows: Figure 8 As shown, the polymer composite film can be heated to approximately 40°C under standard sunlight.

[0065] Example 3

[0066] (1) The preparation of the polymer nanofiber composite membrane is basically the same as in Example 1, except that the volume of the MWCNT suspension used for filtration is 3 mL.

[0067] (2) Mechanical property testing:

[0068] Cut the sample into dumbbell-shaped strips, 50 mm long and 4 mm wide at the neck, using a cutting tool. Tensile the samples using a universal testing machine at a rate of 50 mm / min until fracture to determine the strength and elongation at break of different samples. Each sample should be tested at least five times. Figure 4 As shown.

[0069] (3) Conductivity test:

[0070] The sheet resistance of the polymer composite film was tested using an RTS-9 four-probe tester. The test results are as follows: Figure 5 As shown, the resistance of the polymer composite film reaches 36.3 mΩ / sq.

[0071] (4) Thermal conductivity test:

[0072] The vertical thermal conductivity, thermal diffusivity, and parallel thermal diffusivity of the polymer composite film were measured using an LFA 467 thermal conductivity meter. The horizontal thermal conductivity of the polymer nanofiber composite film was calculated. The test results are as follows: Figure 6 As shown, the vertical thermal conductivity reaches 0.3 W / (m·K). -1 The horizontal thermal conductivity reaches 3.3 W / (m·K). -1 .

[0073] (5) Hydrophobicity test:

[0074] The water contact angle of the polymer composite membrane was tested using a contact angle meter, and the test results are as follows: Figure 7 As shown, the water contact angle of the polymer composite membrane reaches 129.6°.

[0075] (6) Photothermal conversion performance test:

[0076] Using a xenon lamp to simulate standard sunlight intensity, the test results are as follows: Figure 8 As shown, the polymer composite film can reach approximately 37°C under standard sunlight.

[0077] Comparative Example 1

[0078] PU was added to a mixture of THF and DMF as a spinning solution. The mass fraction of PU was 15 wt.% of the total mass, and the mass fraction ratio of THF to DMF solution was 1:4. Electrospinning parameters were set as follows: voltage was 15 kV, liquid feed rate was 2 mL / h, and distance from needle to collection device was 12 cm. The obtained fiber membrane was dried in a 60℃ oven to remove residual solvent.

[0079] After photothermal conversion performance testing and thermal conductivity testing, the test results are as follows: Figure 6 and Figure 8 As shown, the polymer fiber membrane only rises to about 20°C under standard sunlight, and its thermal conductivity is only 2.2 W / (m·K). -1 It cannot meet the requirements for photothermal conversion and heat conduction.

[0080] Comparative Example 2

[0081] PU was added to a mixture of THF and DMF as the spinning solution. The mass fraction of PU was 15 wt.% of the total mass, and the mass ratio of THF to DMF solution was 1:4. Electrospinning parameters were set as follows: voltage 15 kV, feed rate 2 mL / h, and needle-to-collection device distance 12 cm. The obtained fiber membrane was dried in a 60°C oven to remove residual solvent. Dopamine hydrochloride was dissolved in water to prepare a 2 mg / mL dopamine solution, and the pH was adjusted to 8.5. The above fiber membrane was placed in the dopamine solution and soaked for 6 hours, then removed and dried in a 60°C oven for later use. AgNO3 was dissolved in water to prepare a 20 mg / mL AgNO3 solution. The above fiber membrane was placed in the AgNO3 solution, and while stirring, an equal volume of 80 mg / mL C6H2O was added dropwise. 12 After adding O6 solution, react until the solution becomes clear, then remove it and dry it in a 60℃ oven.

[0082] After mechanical property testing, thermal conductivity testing, and photothermal conversion performance testing, the test results are as follows: Figure 4 , Figure 6 and Figure 8 As shown, the polymer fiber membrane exhibits low elongation at break and low strength, rising to only about 22°C under standard sunlight, with a thermal conductivity of only 3.1 W / (m·K). -1 .

[0083] Comparative Example 3

[0084] The preparation of the polymer composite membrane was basically the same as in Example 1, except that the volume of the MWCNT suspension used for filtration was 3 mL and the hot pressing temperature was 60 °C.

[0085] After conductivity and hydrophobicity tests, the test results are as follows: Figure 5 and Figure 7 As shown, the resistance and water contact angle reach 55.3 mΩ / sq and 128.1°, respectively.

[0086] Comparative Example 4

[0087] The preparation of the polymer composite membrane is basically the same as in Example 1, except that the volume of the MWCNT suspension used for filtration is 3 mL and the hot pressing temperature is 80 °C.

[0088] After conductivity and hydrophobicity tests, the test results are as follows: Figure 5 and Figure 7 As shown, the resistance and water contact angle reach 40.3 mΩ / sq and 132.5°, respectively.

[0089] Comparative Example 5

[0090] The preparation of the polymer composite membrane was basically the same as in Example 1, except that the volume of the MWCNT suspension used for filtration was 3 mL and the hot pressing temperature was 120 °C.

[0091] After conductivity and hydrophobicity tests, the test results are as follows: Figure 5 and Figure 7 As shown, the resistance and water contact angle reach 78.7 mΩ / sq and 120.5°, respectively.

[0092] Comparative Example 6

[0093] The preparation of the polymer composite membrane was basically the same as in Example 1, except that the volume of the MWCNT suspension used for filtration was 5 mL and the hot pressing temperature was 60 °C.

[0094] After conductivity and hydrophobicity tests, the test results are as follows: Figure 5 and Figure 7 As shown, the resistance and water contact angle reach 43.3 mΩ / sq and 126.9°, respectively.

[0095] Comparative Example 7

[0096] The preparation of the polymer composite membrane was basically the same as in Example 1, except that the volume of the MWCNT suspension used for filtration was 5 mL and the hot pressing temperature was 80 °C.

[0097] After conductivity and hydrophobicity tests, the test results are as follows: Figure 5 and Figure 7 As shown, the resistance and water contact angle reach 37.3 mΩ / sq and 136.3°, respectively.

[0098] Comparative Example 8

[0099] The preparation of the polymer composite membrane was basically the same as in Example 1, except that the volume of the MWCNT suspension used for filtration was 5 mL and the hot pressing temperature was 120 °C.

[0100] After conductivity and hydrophobicity tests, the test results are as follows: Figure 5 and Figure 7 As shown, the resistance and water contact angle reach 52.3 mΩ / sq and 121.8°, respectively.

[0101] Comparative Example 9

[0102] The preparation of the polymer composite membrane was basically the same as in Example 1, except that the volume of the MWCNT suspension used for filtration was 7 mL and the hot pressing temperature was 60 °C.

[0103] After conductivity and hydrophobicity tests, the test results are as follows: Figure 5 and Figure 7 As shown, the resistance and water contact angle reach 23.8 mΩ / sq and 123.8°, respectively.

[0104] Comparative Example 10

[0105] The preparation of the polymer composite membrane was basically the same as in Example 1, except that the volume of the MWCNT suspension used for filtration was 7 mL and the hot pressing temperature was 80 °C.

[0106] After conductivity and hydrophobicity tests, the test results are as follows: Figure 5 and Figure 7 As shown, the resistance and water contact angle reach 18.3 mΩ / sq and 136.4°, respectively.

[0107] Comparative Example 11

[0108] The preparation of the polymer composite membrane was basically the same as in Example 1, except that the volume of the MWCNT suspension used for filtration was 7 mL and the hot pressing temperature was 120 °C.

[0109] After conductivity and hydrophobicity tests, the test results are as follows: Figure 5 and Figure 7 As shown, the resistance and water contact angle reach 32 mΩ / sq and 132.9°, respectively.

[0110] The above examples are merely illustrative of the technical concept and features of the present invention, intended to enable those skilled in the art to understand the content of the invention and implement it accordingly, and should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a conductive and thermally conductive hydrophobic polymer composite film, characterized in that, Includes the following steps: Step 1: Polyurethane (PU) is added to a mixture of tetrahydrofuran (THF) and N,N-dimethylformamide (DMF) as a spinning solution. The mass fraction of PU is 10-15 wt.% of the total mass, and the mass ratio of THF to DMF solution is 1:

4. A polymer nanofiber membrane is obtained by electrospinning. Step 2: After drying the polymer nanofiber membrane to remove residual THF and DMF, it is immersed in a dopamine (DA) solution. After immersion, it is dried to obtain a composite material with a surface covered by polydopamine (PDA). Step 3: The PDA-coated composite material is immersed in AgNO3 solution and spun using C6H... 12 After reducing AgNO3 with O6 solution, the membrane is dried to obtain a conductive and thermally conductive polymer nanofiber composite membrane with AgNPs coated on the fiber surface. In step 4, a layer of multi-walled carbon nanotubes (MWCNTs) is deposited on the upper and lower surfaces of the conductive and thermally conductive polymer nanofiber composite membrane by vacuum filtration, followed by hot pressing to obtain a conductive and thermally conductive hydrophobic polymer composite membrane with a sandwich structure. The diameter of the sand core used for vacuum filtration is 40 mm. The MWCNTs are dispersed in a mixed solvent of ethanol and water with a volume ratio of 1:1 and a concentration of 1 mg / mL. The hot pressing temperature is 60-120 °C and the hot pressing time is 15 min.

2. The preparation method according to claim 1, characterized in that, In step 1, the spinning voltage is 15 kV, the liquid feed rate is 2 mL / h, and the distance between the needle and the receiver is 12 cm.

3. The preparation method according to claim 1, characterized in that, In step 2, the concentration of the DA solution is 2-4 mg / mL, the pH of the PDA solution is 8-8.5, the soaking time is 6-8 hours, and the soaking temperature is 40-45 ℃.

4. The preparation method according to claim 1, characterized in that, In steps 2 and 3, the drying temperature is 30-60 ℃.

5. The preparation method according to claim 1, characterized in that, In step 3, the concentration of AgNO3 solution is 20 mg / mL, C6H 12 The concentration of the O6 solution is 80 mg / mL, and the soaking time is 2-5 hours.

6. The conductive and thermally conductive hydrophobic polymer composite film prepared by any of the preparation methods described in claims 1 to 5.

7. The application of the conductive and thermally conductive hydrophobic polymer composite film of claim 6 in the preparation of multifunctional conductive and thermally conductive composite materials.

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