A γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber thermal conductive film, its preparation method and application

Abstract

The present invention discloses a γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber thermal conductive film, and its preparation method and application. The preparation method includes, under the condition of an ice-water bath, mixing a diamine monomer and a dianhydride monomer and stirring until the polymerization reaction is complete to obtain a polyamic acid solution; performing electrospinning on the polyamic acid solution to obtain a polyamic acid fiber mat; performing thermal imidization treatment on the polyamic acid fiber mat to obtain a polyimide fiber mat; adding silver nanowires to a silane modifier, heating and reacting to prepare silane-modified silver nanowires, and loading the silane-modified silver nanowires on the surface of the polyimide fiber mat to prepare a silane-modified silver nanowire / polyimide composite fiber mat. This method is simple to operate and reasonably designed. By constructing a silane modification structure, the dispersion of silver nanowires on polyimide is effectively improved, the usage amount of silver nanowires is effectively reduced, and the material has good processability.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of polymer films, and relates to a γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber thermal conductive film, a preparation method thereof, and an application thereof. Background Art

[0002] Polyimide (PI) is a kind of polymer material with excellent comprehensive properties, having many advantages such as excellent high and low temperature resistance, good chemical corrosion resistance, outstanding electrical insulation, and high dimensional stability. It has been widely used in the fields of aviation, aerospace, and microelectronics. However, its low thermal conductivity limits its application in the field of thermal management. Silver nanowires (AgNWs) have many advantages such as high thermal conductivity coefficient (λ), low dielectric constant (ε), and dielectric loss tangent value (tanδ), excellent oxidation resistance, and corrosion resistance, making them an ideal filler for preparing PI thermal conductive insulating composites. Therefore, the effective combination of polyimide and high thermal conductive filler (AgNWs) is considered an ideal solution.

[0003] Currently, the methods for preparing polyimide films include electrospinning method, blade coating method, and casting method. Among them, electrospinning under a high electric field is a simple and effective method to prepare polymer fibers through a solution. The advantages of the prepared fibers mainly include small diameter, high aspect ratio, and large specific surface area, which makes it possible to prepare highly thermally conductive nanocomposite fibers with oriented arrangement. In addition, the multifunctional and simple electrospinning technology provides an effective way to improve the uniform dispersion of fillers, and at the same time realizes the effective arrangement of inorganic fillers in the polymer matrix. However, in the prior art, the usage amount of silver nanowires is relatively high. Although the thermal conductivity has been improved, the high filler usage leads to poor processing ability of the composite fibers and a significant decline in mechanical properties. At the same time, the dispersion of silver nanowires in the polyimide film is poor, which limits their potential application fields. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention provides a γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber thermal conductive film, a preparation method thereof, and an application thereof, so as to solve the technical problem of poor dispersion in the prior art while using silver nanowires to improve the thermal conductivity of polyimide fiber composite films.

[0005] The present invention is realized through the following technical solutions:

[0006] A preparation method of a γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber, comprising the following steps:

[0007] S1: Under the condition of an ice - water bath, add a diamine monomer into a polar aprotic solvent, stir to completely dissolve the diamine monomer, add a dianhydride monomer, and continuously stir until the polymerization reaction is complete to obtain a polyamic acid solution;

[0008] S2: Electrospin the polyamic acid solution to obtain a polyamic acid fiber mat;

[0009] S3: Perform thermal imidization treatment on the polyamic acid fiber mat to obtain a polyimide fiber mat;

[0010] S4: Add silver nanowires into γ - aminopropyltriethoxysilane, heat and react to prepare γ - aminopropyltriethoxysilane - modified silver nanowires, and load the γ - aminopropyltriethoxysilane - modified silver nanowires on the surface of the polyimide fiber mat to prepare a γ - aminopropyltriethoxysilane - modified silver nanowire / polyimide composite fiber mat.

[0011] Preferably, the diamine monomer is one or a mixture of any ratio of 4,4 - diaminodiphenyl ether, 4,4 - diaminobiphenyl, and p - phenylenediamine; the dianhydride monomer is one or a mixture of any ratio of pyromellitic dianhydride, hexafluorodiacid dianhydride, and 3,3',4,4' - benzophenone tetracarboxylic dianhydride.

[0012] Preferably, the polar aprotic solvent is one or a mixture of any ratio of N,N - dimethylformamide, N,N - dimethylacetamide, N - methylpyrrolidone, and dimethyl sulfoxide.

[0013] Preferably, the mass ratio of the diamine monomer to the dianhydride monomer is 1:1.04.

[0014] Preferably, in step S1, add the dianhydride monomer in several batches. After adding each batch of the dianhydride monomer, stir until it is completely dissolved and reacted, and then add the next batch of the dianhydride monomer; the amount of the dianhydride monomer added in each batch does not exceed 0.2 g.

[0015] Preferably, in step S2, the voltage for electrospinning is 15 - 25 kV, and the distance from the needle to the center of the drum is 15 - 20 cm.

[0016] Preferably, before performing the thermal imidization treatment, treat the polyamic acid fiber mat under vacuum; the conditions for vacuum treatment are: vacuum degree 0.08 - 0.1 MPa, temperature 60 - 80 °C, and time 4 - 6 h.

[0017] Preferably, in step S4, the mass percentage of the γ - aminopropyltriethoxysilane - modified silver nanowires in the polyamic acid is 0.1% - 0.5%.

[0018] A γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber is prepared by the above method; the breakdown strength of the γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber is 7.1-13.2 kV / mm.

[0019] Application of the above γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber in the field of electronic packaging.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] A preparation method of a γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber. The silane modified structure constructed on the silver nanowire can be effectively bonded with the polyimide, effectively improving the dispersion of the silver nanowire in the polyimide film. This method is simple to operate and reasonably designed. By constructing the silane modified structure, the dispersion of the silver nanowire on the polyimide is effectively improved, the usage amount of the silver nanowire is effectively reduced, and the material has good processability.

[0022] Further, in step S1, the dianhydride monomer is added in several batches. After each addition of the dianhydride monomer, it is stirred until it is dissolved and the reaction is complete, and then the next batch of the dianhydride monomer is added; the amount of the dianhydride monomer added in each batch does not exceed 0.2 g. This method can effectively control the heat generation during the reaction, reduce the volatilization of the organic solvent, and at the same time enable the dianhydride and diamine to react fully.

[0023] Further, the voltage of the electrospinning is 15-25 kV, which can make the fiber spinning uniform and stable, and the production rate is high.

[0024] Further, before the thermal imidization treatment, the polyamic acid fiber felt is treated under vacuum; the conditions of the vacuum treatment are: the vacuum degree is 0.08-0.1 MPa, the temperature is 60-80 °C, and the time is 4-6 h, which can effectively remove the organic solvent in the product. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts.

[0026] Figure 1 It is a process schematic diagram of a preparation method of a γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber in the present invention;

[0027] Figure 2 Schematic flow chart of the preparation method of γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber thermal conductive film in Example 1 of the present invention;

[0028] Figure 3 Thermal infrared comparison diagram of γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber thermal conductive films with different contents of γ-aminopropyltriethoxysilane and pure polyimide film in the present invention;

[0029] Figure 4 Breakdown strength results of the composite fiber films prepared in Comparative Example 1 and Examples 1 to 5 of the present invention. Detailed implementation manners

[0030] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art for the present invention. In case of conflict, the definition in this specification shall prevail.

[0031] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall in no way limit the scope of the present invention, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0032] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values (including integers and fractions) within the range.

[0033] In this article, unless otherwise specified, the terms "comprising", "including", "containing", "having", or similar expressions cover the meanings of "consisting of" and "mainly consisting of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A only comprises a".

[0034] In this article, for the sake of concise description, not all possible combinations of all technical features in each embodiment or example are described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as within the scope described in this specification.

[0035] The present invention provides a preparation method of a γ-aminopropyltriethoxysilane (KH550) modified silver nanowire / polyimide composite fiber thermal conductive film. The preparation method uses polyamic acid (PAA) condensed from dianhydride monomer and diamine monomer as the matrix, and prepares a polyamic acid (PAA) fiber felt by electrospinning method, and then through thermal imidization and spin-coating a KH550 modified silver nanowire solution with different concentrations on the polyimide composite fiber felt to obtain the KH550 modified silver nanowire / polyimide composite fiber thermal conductive film. As Figure 1 shown, the specific process of this preparation method is as follows:

[0036] S1: Under the condition of an ice-water bath, add the diamine monomer into the polar aprotic solvent, stir to completely dissolve the diamine monomer, add the dianhydride monomer, and continuously stir until the polymerization reaction is complete to obtain a polyamic acid solution;

[0037] Among them, the diamine monomer is a mixture of one or several of 4,4-diaminodiphenyl ether, 4,4-diaminobiphenyl and p-phenylenediamine in any ratio; the dianhydride monomer is a mixture of one or several of pyromellitic dianhydride, hexafluorodiacid anhydride and 3,3',4,4'-benzophenone tetracarboxylic dianhydride in any ratio.

[0038] The polar aprotic solvent is a mixture of one or several of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide. N,N-dimethylformamide has a high boiling point, a low freezing point, and good chemical and thermal stability. The ratio of the diamine monomer to the dianhydride monomer is 1:1.04. In this step, the dianhydride monomer is added in several batches. After each addition of the dianhydride monomer, stir to dissolve it and react completely, and then add the next batch of the dianhydride monomer; the amount of the dianhydride monomer added in each batch does not exceed 0.2 g.

[0039] S2: Electrospin the polyamic acid solution to obtain a polyamic acid fiber felt;

[0040] Among them, the specific process of electrospinning is as follows: Load the polyamic acid (PAA) solution into a syringe needle equipped with a metal needle, then horizontally fix the syringe needle on the spraying device, connect the positive electrode of the high-voltage power supply of the electrospinning instrument to the metal needle, wrap the tin foil collecting paper on the drum-shaped negative electrode, align the syringe needle with the center of the drum, keep the working chamber of the electrospinning instrument in a sealed state, the temperature in the working chamber during electrospinning is 18-25 °C, the environmental relative humidity is 50%-60%, the voltage of the high-voltage power supply is 15-25 kV, the distance from the needle to the center of the drum is 15-20 cm, and the drum rotation speed is 40-120 m / min.

[0041] S3: Perform thermal imidization treatment on the polyamic acid fiber felt to obtain a polyimide fiber felt;

[0042] Before the thermal imidization treatment, the polyamic acid fiber felt is treated under vacuum. The conditions for the vacuum treatment are as follows: the degree of vacuum is 0.08 - 0.1 MPa, the temperature is 60 - 80 °C, and the time is 4 - 6 h.

[0043] S4: Add silver nanowires to the silane modifier, heat and react to obtain silane-modified silver nanowires, and load the silane-modified silver nanowires on the surface of the polyimide fiber felt, and dry at 60 °C for 1 h to obtain a silane-modified silver nanowire / polyimide composite fiber felt.

[0044] Among them, the ratio of silver nanowires to the silane modifier is 5%, and the mass percentage of the silane-modified silver nanowires in the polyamic acid is 0.1% - 0.5%.

[0045] The present invention adopts a method combining low-temperature polycondensation, electrospinning and spin coating processes. The KH550-modified structure constructed on the silver nanowires can be effectively bonded to the polyimide, effectively improving the dispersion of the silver nanowires in the polyimide film, and significantly improving the mechanical properties and thermal conductivity of the polyimide fiber film. The breakdown strength of the KH550-modified silver nanowire / polyimide composite fiber thermal conductive film prepared by the scheme of the present invention is 6.51 - 12.29 kV / mm. The obtained KH550-modified silver nanowire / polyimide composite fiber thermal conductive film can be applied to the field of electronic packaging.

[0046] In the present invention, the specific process for testing the breakdown strength is as follows: Use a withstand voltage tester to test the KH550-modified silver nanowire / polyimide composite fiber thermal conductive composite film, and reflect the insulation performance of the composite film by testing the magnitude of the electric breakdown strength value. 10 - 15 groups of data are tested for one sample. Since there will be errors in the thickness during the film preparation process, and the magnitude of the electric breakdown strength is related to the sample thickness, the overall electric breakdown strength of the composite film is obtained by using the actual test data.

[0047] E = U / d

[0048] In the formula:

[0049] E - Electrical breakdown strength (kV / mm)

[0050] U - Breakdown voltage (kV)

[0051] d - Sample thickness corresponding to the breakdown point (mm)

[0052] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0053] In the following embodiments, conventional instrument and equipment in the art are used. For the experimental methods without specific conditions noted in the following embodiments, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. In the following embodiments, various raw materials are used. Unless otherwise stated, commercially available products are used, and their specifications are conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0054] Comparative Example 1

[0055] 1.08 g of 4,4'-diaminodiphenyl ether (ODA) was added to a three-necked flask, and 19 g of N,N-dimethylformamide (DMF) was added under an ice-water bath. After the ODA was completely dissolved, 1.244 g of pyromellitic dianhydride (PMDA) was added in batches, with 0.15 g of PMDA added each time. After all the PMDA was added and dissolved, mechanical stirring was carried out for 30 min, and then polyamic acid mixed solution was obtained by polycondensation. Polyamic acid fiber film was obtained by electrospinning, and polyimide film was obtained after imidization.

[0056] The PI film was fixed on a spin-coating device, 0.057 mL of AgNWs dispersion was evenly dropped on the surface of the PI film, and then the pipette gun was aligned with the center of the flat plate. The rotation speed was maintained at 1000 rpm, and it was placed in an oven at 60 °C for 1 h. After cooling to room temperature, it was taken out to obtain silver nanowire / polyimide (AgNWs / PI) composite film, where AgNWs accounted for 0.3 wt.% of the mass of PAA.

[0057] Example 1

[0058] 2 mL of KH550 (γ-aminopropyltriethoxysilane) was added to a mixed solution of 20 mL of deionized water and 180 mL of absolute ethanol, and mixed evenly; 0.019 mL of silver nanowires (AgNWs) was added, and it was heated in a water bath at 60 °C for 60 min, stirred until the reaction was complete, washed with deionized water, and centrifuged at 7000 rpm to remove the supernatant, thus obtaining KH550-modified silver nanowires (s-AgNWs).

[0059] 1.08 g of 4,4'-diaminodiphenyl ether (ODA) was added to a three-necked flask. Under an ice-water bath condition, 19 g of N,N-dimethylformamide (DMF) was added. After the ODA was completely dissolved, 1.244 g of pyromellitic dianhydride (PMDA) was added in batches, with 0.15 g of PMDA added each time. After all the PMDA was added and dissolved, it was mechanically stirred for 30 min and then polycondensed to obtain a polyamic acid mixed solution.

[0060] The PI film was fixed on a spin-coating device. 0.019 mL of the AgNWs dispersion was evenly dropped on the surface of the PI film. Then, the pipette gun was aligned with the center of the flat plate, and the rotation speed was maintained at 1000 revolutions per minute. It was placed in an oven at 60 °C for 1 h, taken out after cooling to room temperature, and a KH550-modified silver nanowire / polyimide (s-AgNWs / PI) composite film was obtained, where s-AgNWs accounted for 0.1 wt.% of the mass of PAA.

[0061] In this example, the preparation method of the KH550-modified silver nanowire / polyimide composite film is shown in Figure 2 .

[0062] Example 2

[0063] 2 mL of KH550 (γ-aminopropyltriethoxysilane) was added to a mixed solution of 20 mL of deionized water and 180 mL of absolute ethanol and mixed evenly; 0.038 mL of silver nanowires (AgNWs) was added, and it was placed in a water bath at 60 °C for 60 min and stirred until the reaction was complete. It was washed with deionized water and centrifuged at 7000 revolutions per minute to remove the supernatant, and KH550-modified silver nanowires (s-AgNWs) were prepared.

[0064] 1.08 g of 4,4'-diaminodiphenyl ether (ODA) was added to a three-necked flask. Under an ice-water bath condition, 19 g of N,N-dimethylformamide (DMF) was added. After the ODA was completely dissolved, 1.244 g of pyromellitic dianhydride (PMDA) was added in batches, with 0.15 g of PMDA added each time. After all the PMDA was added and dissolved, it was mechanically stirred for 30 min and then polycondensed to obtain a polyamic acid mixed solution. Electrospinning was carried out to obtain a polyamic acid fiber film, which was imidized to obtain a polyimide film.

[0065] The PI film was fixed on a spin-coating device. 0.038 mL of the AgNWs dispersion was evenly dropped on the surface of the PI film. Then, the pipette gun was aligned with the center of the flat plate, and the rotation speed was maintained at 1000 revolutions per minute. It was placed in an oven at 60 °C for 1 h, taken out after cooling to room temperature, and a KH550-modified silver nanowire / polyimide (s-AgNWs / PI) composite film was obtained, where s-AgNWs accounted for 0.2 wt.% of the mass of PAA.

[0066] Example 3

[0067] Add 2 mL of KH550 (γ-aminopropyltriethoxysilane) to a mixed solution of 20 mL of deionized water and 180 mL of absolute ethanol, and mix well; add 0.057 mL of silver nanowires (AgNWs), heat in a water bath at 60 °C for 60 min, stir to complete the reaction, wash with deionized water, centrifuge at 7000 rpm, remove the supernatant, and obtain KH550-modified silver nanowires (s-AgNWs).

[0068] Add 1.08 g of 4,4'-diaminodiphenyl ether (ODA) to a three-necked flask, add 19 g of N,N-dimethylformamide (DMF) under an ice-water bath. After ODA is completely dissolved, add 1.244 g of pyromellitic dianhydride (PMDA) in batches, with each batch adding 0.15 g of PMDA. After all PMDA is added and dissolved, stir mechanically for 30 min and then carry out polycondensation to obtain a polyamic acid mixed solution. Electrospinning gives a polyamic acid fiber film, and after imidization, a polyimide film is obtained.

[0069] Fix the PI film on a spin-coating device, evenly drop 0.057 mL of the AgNWs dispersion on the surface of the PI film, then align the pipette gun with the center of the flat plate, keep the rotation speed at 1000 rpm, place it in an oven at 60 °C for 1 h, take it out after cooling to room temperature, and obtain a KH550-modified silver nanowire / polyimide (s-AgNWs / PI) composite film, where s-AgNWs accounts for 0.3 wt.% of the mass of PAA.

[0070] Example 4

[0071] Add 2 mL of KH550 (γ-aminopropyltriethoxysilane) to a mixed solution of 20 mL of deionized water and 180 mL of absolute ethanol, and mix well; add 0.076 mL of silver nanowires (AgNWs), heat in a water bath at 60 °C for 60 min, stir to complete the reaction, wash with deionized water, centrifuge at 7000 rpm, remove the supernatant, and obtain KH550-modified silver nanowires (s-AgNWs).

[0072] Add 1.08 g of 4,4'-diaminodiphenyl ether (ODA) to a three-necked flask, add 19 g of N,N-dimethylformamide (DMF) under an ice-water bath. After ODA is completely dissolved, add 1.244 g of pyromellitic dianhydride (PMDA) in batches, with each batch adding 0.15 g of PMDA. After all PMDA is added and dissolved, stir mechanically for 30 min and then carry out polycondensation to obtain a polyamic acid mixed solution. Electrospinning gives a polyamic acid fiber film, and after imidization, a polyimide film is obtained.

[0073] Fix the PI film on the spin-coating device, evenly drop 0.076 mL of the AgNWs dispersion on the surface of the PI film, then align the pipette gun with the center of the flat plate, keep the rotation speed at 1000 revolutions per minute, place it in an oven at 60 °C for 1 h, take it out after cooling to room temperature, and obtain the KH550-modified silver nanowire / polyimide (s-AgNWs / PI) composite film, where s-AgNWs accounts for 0.4 wt.% of the mass of PAA.

[0074] Example 5

[0075] Add 2 mL of KH550 (γ-aminopropyltriethoxysilane) to a mixed solution of 20 mL of deionized water and 180 mL of absolute ethanol, mix well; add 0.095 mL of silver nanowires (AgNWs), react in a water bath at 60 °C for 60 min, stir to make the reaction complete, wash with deionized water, centrifuge at 7000 revolutions, and remove the supernatant to obtain KH550-modified silver nanowires (s-AgNWs).

[0076] Add 1.08 g of 4,4'-diaminodiphenyl ether (ODA) to a three-necked flask, add 19 g of N,N-dimethylformamide (DMF) under an ice-water bath. After the ODA is completely dissolved, add 1.244 g of pyromellitic dianhydride (PMDA) in batches, adding 0.15 g of PMDA each time. After all the PMDA is added and dissolved, mechanically stir for 30 min and then carry out polycondensation to obtain a polyamic acid mixed solution. Electrospinning is used to obtain a polyamic acid fiber film, and a polyimide film is obtained after imidization.

[0077] Fix the PI film on the spin-coating device, evenly drop 0.095 mL of the AgNWs dispersion on the surface of the PI film, then align the pipette gun with the center of the flat plate, keep the rotation speed at 1000 revolutions per minute, place it in an oven at 60 °C for 1 h, take it out after cooling to room temperature, and obtain the KH550-modified silver nanowire / polyimide (s-AgNWs / PI) composite film, where s-AgNWs accounts for 0.5 wt.% of the mass of PAA.

[0078] The results of the thermal infrared tests of the composite fiber films prepared in Comparative Example 1 and Examples 3 and 5 of the present invention are shown in Figure 3 , from Figure 4 it can be seen that at 20 s, when the addition amount of s-AgNWs is 0.3% and 0.5%, the temperature has been significantly increased to nearly 80 °C, while the temperature of the pure PI film is about 60 °C, and the thermal conductivity and mechanical properties of the s-AgNWs / PI composite film have been significantly improved.

[0079] The breakdown strength results of the composite fiber films prepared in Comparative Example 1 and Examples 1 to 5 of the present invention are shown in Figure 4 , from Figure 4It can be seen that with the increase in the addition amount of silver nanowires, the mechanical properties of the composite fiber film will be affected.

[0080] The present invention also protects the application of the polyimide film prepared by the above method in the field of electronic packaging. The film has good mechanical properties, insulation properties, and high-temperature resistance, and the service life of the film is effectively extended, ensuring the use reliability of devices and equipment.

[0081] Example 6

[0082] A preparation method of a γ-aminopropyltriethoxysilane-modified silver nanowire / polyimide composite fiber thermal conductive film, and the specific process is as follows:

[0083] S1: Under the condition of an ice-water bath, add 4,4-diaminodiphenyl ether to N,N-dimethylformamide, stir to completely dissolve 4,4-diaminodiphenyl ether, add pyromellitic dianhydride, and continuously stir until the polymerization reaction is complete to obtain a polyamic acid solution;

[0084] Among them, the ratio of the diamine monomer to the dianhydride monomer is 1:1.04. In this step, the pyromellitic dianhydride is added in several batches. After each addition of pyromellitic dianhydride, stir to dissolve it and react completely, and then add the next batch of pyromellitic dianhydride; the amount of pyromellitic dianhydride added in each batch is 0.18 g.

[0085] S2: Load the polyamic acid solution into a syringe equipped with a metal needle, then horizontally fix the syringe on the spraying device, connect the positive electrode of the high-voltage power supply of the electrospinning instrument to the metal needle, wrap the tin foil collecting paper around the drum-shaped negative electrode, align the syringe with the center of the drum, keep the working chamber of the electrospinning instrument in a sealed state, the temperature in the working chamber during electrospinning is 18 °C, the environmental relative humidity is 50%, the voltage of the high-voltage power supply is 15 kV, the distance from the needle to the center of the drum is 15 cm, and the drum rotation speed is 40 m / min.

[0086] S3: Vacuum-treat the polyamic acid fiber felt under the conditions of a vacuum degree of 0.08 - 0.1 MPa and a temperature of 60 - 80 °C for 4 h, and then perform thermal imidization treatment on the polyamic acid fiber felt to obtain a polyimide fiber felt;

[0087] S4: Add silver nanowires to the silane modifier, heat and react to prepare silane-modified silver nanowires, and load the silane-modified silver nanowires on the surface of the polyimide fiber felt, and dry at 60 °C for 1 h to obtain a silane-modified silver nanowire / polyimide composite fiber felt. Among them, the ratio of silver nanowires to the silane modifier is 5%, and the mass percentage of silane modification in silver nanowire polyamic acid is 0.1%.

[0088] The breakdown strength of the KH550-modified silver nanowire / polyimide composite fiber thermal conductive film prepared in this example is 6.5 kV / mm.

[0089] Example 7

[0090] A preparation method of a γ-aminopropyltriethoxysilane-modified silver nanowire / polyimide composite fiber thermal conductive film, the specific process is as follows:

[0091] S1: Under the condition of an ice-water bath, add 4,4-diaminobiphenyl to N,N-dimethylacetamide, stir to completely dissolve 4,4-diaminodiphenyl ether, add hexafluorodiacid anhydride, and continuously stir until the polymerization reaction is complete to obtain a polyamic acid solution; among them, the mass ratio of 4,4-diaminobiphenyl to hexafluorodiacid anhydride is 1:1.04. In this step, the hexafluorodiacid anhydride is added in several batches. After each addition of hexafluorodiacid anhydride, stir to dissolve it and react completely, and then add the next batch of hexafluorodiacid anhydride; the amount of hexafluorodiacid anhydride added in each batch is 0.1 g.

[0092] S2: Load the polyamic acid solution into a syringe equipped with a metal needle, then horizontally fix the syringe on the spraying device, connect the positive electrode of the high-voltage power supply of the electrospinning instrument to the metal needle, wrap the tin foil collecting paper on the drum-shaped negative electrode, align the syringe with the center of the drum, keep the working chamber of the electrospinning instrument in a sealed state, the temperature in the working chamber during the electrospinning process is 20 °C, the environmental relative humidity is 50%, the voltage of the high-voltage power supply is 20 kV, the distance from the needle to the center of the drum is 18 cm, and the drum rotation speed is 80 m / min.

[0093] S3: Vacuum-treat the polyamic acid fiber felt under the conditions of a vacuum degree of 0.08 MPa and a temperature of 65 °C for 4.5 h, and then perform thermal imidization treatment on the polyamic acid fiber felt to obtain a polyimide fiber felt;

[0094] S4: Add silver nanowires to the silane modifier, heat and react to obtain silane-modified silver nanowires, and load the silane-modified silver nanowires on the surface of the polyimide fiber felt, and dry at 60 °C for 1 h to obtain a silane-modified silver nanowire / polyimide composite fiber felt. Among them, the ratio of silver nanowires to the silane modifier is 5%, and the mass percentage of the silane-modified silver nanowire polyamic acid is 0.2%.

[0095] The breakdown strength of the KH550-modified silver nanowire / polyimide composite fiber thermal conductive film prepared in this example is 10.51 kV / mm.

[0096] Example 8

[0097] A preparation method of a γ-aminopropyltriethoxysilane-modified silver nanowire / polyimide composite fiber thermal conductive film, the specific process is as follows:

[0098] S1: Under the condition of an ice-water bath, add p-phenylenediamine to N-methylpyrrolidone, stir to completely dissolve p-phenylenediamine, add 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and continuously stir until the polymerization reaction is complete to obtain a polyamic acid solution; wherein, the mass ratio of p-phenylenediamine to 3,3',4,4'-benzophenone tetracarboxylic dianhydride is 1:1.04. In this step, the 3,3',4,4'-benzophenone tetracarboxylic dianhydride is added in several batches. After each addition, stir to dissolve it and react completely, and then add the next batch of 3,3',4,4'-benzophenone tetracarboxylic dianhydride; the amount of 3,3',4,4'-benzophenone tetracarboxylic dianhydride added in each batch is 0.15 g.

[0099] S2: Fill the polyamic acid solution into a syringe equipped with a metal needle, then horizontally fix the syringe on a spraying device, connect the positive electrode of the high-voltage power supply of the electrospinning instrument to the metal needle, wrap the tin foil collecting paper around the cylindrical negative electrode, align the syringe with the center of the cylinder, keep the working chamber of the electrospinning instrument in a sealed state. During the electrospinning process, the temperature of the working chamber is 25°C, the environmental relative humidity is 55%, the voltage of the high-voltage power supply is 23 kV, the distance from the needle to the center of the cylinder is 20 cm, and the rotation speed of the cylinder is 100 m / min.

[0100] S3: Treat the polyamic acid fiber felt under vacuum at a vacuum degree of 0.1 MPa and a temperature of 70°C for 6 h, and then perform thermal imidization treatment on the polyamic acid fiber felt to obtain a polyimide fiber felt;

[0101] S4: Add silver nanowires to a silane modifier, heat and react to prepare silane-modified silver nanowires, and load the silane-modified silver nanowires on the surface of the polyimide fiber felt, and dry at 60°C for 1 h to prepare a silane-modified silver nanowire / polyimide composite fiber felt. Among them, the ratio of silver nanowires to the silane modifier is 5%, and the mass percentage of silane modification in silver nanowire polyamic acid is 0.3%.

[0102] The breakdown strength of the KH550-modified silver nanowire / polyimide composite fiber thermal conductive film prepared in this example is 11.20 kV / mm.

[0103] Example 9

[0104] A preparation method of a γ-aminopropyltriethoxysilane-modified silver nanowire / polyimide composite fiber thermal conductive film, and the specific process is as follows:

[0105] S1: Under the condition of ice-water bath, add 4,4'-diaminodiphenyl ether and 4,4'-diaminobiphenyl into dimethyl sulfoxide, stir to completely dissolve 4,4'-diaminodiphenyl ether and 4,4'-diaminobiphenyl, add pyromellitic dianhydride and hexafluorodiacid anhydride, and continuously stir until the polymerization reaction is complete to obtain a polyamic acid solution; wherein, the mass ratio of 4,4'-diaminodiphenyl ether and 4,4'-diaminobiphenyl to pyromellitic dianhydride and hexafluorodiacid anhydride is 1:1.04. In this step, the pyromellitic dianhydride and hexafluorodiacid anhydride are added in several batches. After each addition, stir to dissolve it and react completely, and then add the next batch of pyromellitic dianhydride and hexafluorodiacid anhydride; the amount of pyromellitic dianhydride and hexafluorodiacid anhydride added in each batch is 0.10 g.

[0106] S2: Load the polyamic acid solution into a syringe equipped with a metal needle, then horizontally fix the syringe on the spraying device, connect the positive electrode of the high-voltage power supply of the electrospinning instrument to the metal needle, wrap the tin foil collecting paper around the cylindrical negative electrode, align the syringe with the center of the cylinder, keep the working chamber of the electrospinning instrument in a sealed state. During the electrospinning process, the temperature of the working chamber is 25 °C, the environmental relative humidity is 60%, the voltage of the high-voltage power supply is 25 kV, the distance from the needle to the center of the cylinder is 20 cm, and the rotation speed of the cylinder is 120 m / min.

[0107] S3: Treat the polyamic acid fiber felt under vacuum at a vacuum degree of 0.1 MPa and a temperature of 80 °C for 6 h, and then perform thermal imidization treatment on the polyamic acid fiber felt to obtain a polyimide fiber felt;

[0108] S4: Add silver nanowires to the silane modifier, heat and react to prepare silane-modified silver nanowires, and load the silane-modified silver nanowires on the surface of the polyimide fiber felt, and dry at 60 °C for 1 h to prepare a silane-modified silver nanowire / polyimide composite fiber felt. Among them, the ratio of silver nanowires to the silane modifier is 5%, and the mass percentage of silane modification in silver nanowire polyamic acid is 0.5%.

[0109] The breakdown strength of the KH550-modified silver nanowire / polyimide composite fiber thermal conductive film prepared in this example is 12.30 kV / mm.

[0110] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A preparation method of γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber, which is characterized in that, It includes the following steps: S1: Under the condition of ice-water bath, add diamine monomer into polar aprotic solvent, stir to completely dissolve the diamine monomer, add dianhydride monomer, and continuously stir until the polymerization reaction is complete to obtain a polyamic acid solution; S2: Electrospun the polyamic acid solution to obtain a polyamic acid fiber felt; S3: Carry out thermal imidization treatment on the polyamic acid fiber felt to obtain a polyimide fiber felt; S4: Add silver nanowires into γ-aminopropyltriethoxysilane, heat and react to prepare γ-aminopropyltriethoxysilane-modified silver nanowires, and load the γ-aminopropyltriethoxysilane-modified silver nanowires on the surface of the polyimide fiber felt to prepare a γ-aminopropyltriethoxysilane-modified silver nanowire / polyimide composite fiber felt.

2. The preparation method of a γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber according to claim 1, wherein, The diamine monomer is one or a mixture of any ratio of 4,4-diaminodiphenyl ether, 4,4-diaminobiphenyl and p-phenylenediamine; the dianhydride monomer is one or a mixture of any ratio of pyromellitic dianhydride, hexafluorodiacid dianhydride and 3,3',4,4'-benzophenone tetracarboxylic dianhydride.

3. The preparation method of a γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber according to claim 1, characterized in that, The polar aprotic solvent is one or a mixture of any ratio of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide.

4. The preparation method of a γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber according to claim 1, characterized in that The mass ratio of diamine monomer to dianhydride monomer is 1:1.

04.

5. The preparation method of a γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber according to claim 1, characterized in that, In step S1, add the dianhydride monomer in several batches. After adding the dianhydride monomer each time, stir to dissolve and react it completely, and then add the next batch of dianhydride monomer; the amount of dianhydride monomer added in each batch does not exceed 0.2 g.

6. The preparation method of a γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber according to claim 1, characterized in that In step S2, the voltage of electrospinning is 15-25 kV, and the distance from the needle to the center of the drum is 15-20 cm.

7. The preparation method of a γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber according to claim 1, characterized in that, Before carrying out the thermal imidization treatment, treat the polyamic acid fiber felt under vacuum; the conditions of vacuum treatment are: vacuum degree 0.08-0.1 MPa, temperature 60-80 °C, and time 4-6 h.

8. The preparation method of a γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber according to claim 1, characterized in that, In step S4, the mass percentage of the γ-aminopropyltriethoxysilane-modified silver nanowires in the polyamic acid is 0.1%-0.5%.

9. A γ-aminopropyltriethoxysilane modified silver nanowire / polyimide composite fiber, characterized in that, It is prepared by the method described in any one of claims 1-8; the breakdown strength of the γ-aminopropyltriethoxysilane-modified silver nanowire / polyimide composite fiber is 7.1-13.2 kV / mm.

10. Application of the γ-aminopropyltriethoxysilane-modified silver nanowire / polyimide composite fiber described in claim 9 in the field of electronic packaging.

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