Composite insulation paper and method for manufacturing the same

Abstract

This invention relates to the field of materials technology, and provides a composite insulating paper and its preparation method. The method includes: functionalizing BNNS with polydopamine (PDA) to obtain BNNS@PDA; preparing gallium-indium alloy (LM) using gallium and indium as raw materials; dispersing the gallium-indium alloy LM in polyvinyl alcohol (PVA) by electrospinning to obtain PVA@LM nanofibers; adding poly(p-phenylenebenzodioxazole) (PBO) fibers, BNNS@PDA, and PVA@LM nanofibers to deionized water and shearing to obtain a composite solution; spraying the composite solution onto a substrate to form a thin film; and immersing the thin film in a solution containing C8H... 10 After being immersed in an O8 solution, the material is removed and subjected to a curing and cross-linking reaction to obtain a cured cross-linked film. The cured cross-linked film is then cooled, rinsed, and dried to obtain rough paper. The rough paper is then hot-pressed to obtain composite insulating paper. Compared with existing insulating paper, the composite insulating paper provided by this invention has significantly improved thermal conductivity. The method provided by this invention is simple and low in cost.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and in particular to a composite insulating paper and its preparation method. Background Technology

[0002] As power equipment gradually develops towards larger capacity and higher voltage levels, higher requirements are being placed on the thermal conductivity of the insulation systems of important equipment such as transformers and variable frequency motors.

[0003] Because electrical equipment generates a lot of heat during operation, and the poor thermal conductivity of insulation materials will further accelerate their thermal aging rate, resulting in a shorter lifespan and unreliable operation of the electrical equipment.

[0004] Therefore, in order to extend the service life of power equipment and ensure its stable operation, it is urgent to develop a new type of insulating paper with good thermal conductivity for application in power equipment. Summary of the Invention

[0005] This invention provides a composite insulating paper and its preparation method to solve the defect of insufficient thermal conductivity of insulating paper in the prior art, so as to meet the current needs of electrical insulation systems for power equipment.

[0006] A method for preparing composite insulating paper includes:

[0007] Step 1: Functionalize BNNS with polydopamine PDA to obtain BNNS@PDA;

[0008] Step 2: Gallium-indium alloy LM is prepared by melting gallium and indium as raw materials;

[0009] Step 3: The gallium indium alloy LM is used as a thermally conductive filler and effectively dispersed in polyvinyl alcohol PVA by electrospinning to obtain dry PVA@LM nanofibers;

[0010] Step 4: Add poly(p-phenylenebenzodioxazole) PBO fibers and the BNNS@PDA and PVA@LM nanofibers to deionized water and shear them to obtain a composite solution;

[0011] Step 5: The composite solution is sprayed onto the substrate using an electrostatic spraying method to form a thin film;

[0012] Step 6: Immerse the film in a solution containing C8H 10 After being immersed in the O8 solution for a certain period of time, the film was removed, dried, and then subjected to a curing and crosslinking reaction to obtain a cured and crosslinked film.

[0013] Step 7: Cool, rinse, and dry the cured cross-linked film to obtain rough paper;

[0014] Step 8: The rough paper is hot-pressed using a vacuum hot press to finally obtain the composite insulating paper.

[0015] Furthermore, in the method for preparing composite insulating paper as described above, in step 5, the thickness of the film is 1000μm to 1500μm.

[0016] Furthermore, in the method for preparing the composite insulating paper as described above, the poly(p-phenylenebenzodioxazole) PBO fiber is prepared using the following method:

[0017] Step a: Using 4,6-diaminoresorcinol hydrochloride monomer and terephthalic acid monomer as raw materials, and polyphosphoric acid as solvent, a polymerization reaction is carried out to produce PBO;

[0018] Step b: Dissolve the PBO obtained by polymerization in polyphosphoric acid to prepare a mixed solution with a concentration of 15% to 20%;

[0019] Step c: The mixed solution is subjected to dry-jet wet spinning at an environment of 90-120°C and a spinning speed of 10-12 mm / min to obtain nascent yarn;

[0020] Step d: The nascent filament is subjected to water bath condensation setting, acid washing, drying, and hot stretching treatment to obtain the PBO fiber.

[0021] Furthermore, in the method for preparing the composite insulating paper as described above, step 1 includes the following steps:

[0022] Step a: Place BNNS and sodium hydroxide solution into a ball mill jar, ball mill, wash the mixture after ball milling with deionized water, and finally dry the mixture after ball milling to obtain BNNS-OH;

[0023] Step b: Prepare a Tris-HCl buffer solution using Tris-base and hydrochloric acid solution; the pH of this Tris-HCl solution is 8.5.

[0024] Step c: The Tris-HCl buffer solution and dopamine hydrochloride are neutralized under alkaline conditions to obtain a dopamine solution;

[0025] Step d: The BNNS-OH, dopamine solution, and alcohol are mixed and magnetically stirred at 20℃-35℃ for 18 hours to allow dopamine to spontaneously polymerize under alkaline conditions to obtain polydopamine PDA, thus completing the in-situ polymerization of BNNS and PDA. After filtration, repeated washing, and drying, the BNNS@PDA is obtained.

[0026] Furthermore, in the method for preparing the composite insulating paper as described above, step 2 includes the following steps:

[0027] Gallium and indium are heated to 350-400°C with an alcohol lamp in a mass ratio of (0.3-3):1 to fully fuse them, thus obtaining the gallium-indium alloy LM.

[0028] Furthermore, in the method for preparing the composite insulating paper as described above, step 3 includes the following steps:

[0029] Step a: The polyvinyl alcohol (PVA) and gallium indium alloy (LM) are mixed evenly by ultrasonic, shearing and stirring to obtain a spinning solution; the mass ratio of PVA to LM is 1:(3-5).

[0030] Step b: Inject the spinning solution into the jetting device and fix the jetting device on the injection pump of the electrospinning machine. Connect the fiber receiving device to the negative electrode and ground it, placing it directly below the needle. Spinning is performed using a receiving distance of 10-12 cm, a liquid pushing speed of 0.1 mm / min, and a spinning voltage of 10-20 kV to deposit PVA@LM nanofibers on the fiber receiving device. Collect the deposited PVA@LM nanofibers and dry them to obtain dried PVA@LM nanofibers. The drying temperature is 160-180℃, and the drying time is 30 min.

[0031] Furthermore, in the method for preparing the composite insulating paper as described above, the material containing C8H... 10 The solution of O8 is:

[0032] C8H 10 O8 and sodium hypophosphite were dissolved in deionized water in a 2:1 ratio to obtain a solution; the C8H 10 The concentration of O8 is 0.2–0.3 mol / L.

[0033] Furthermore, in the method for preparing composite insulating paper as described above, in step 6, the temperature of the curing crosslinking reaction is 150℃~190℃, and the reaction time is 10min.

[0034] Furthermore, in the method for preparing composite insulating paper as described above, in step 4, the mass ratio of poly(p-phenylenebenzodioxazole) PBO fiber, BNNS@PDA, PVA@LM nanofiber, and deionized water is 1:(0.1-0.3):(0.5-2):400.

[0035] The shearing rate was 10,000–25,000 rpm, and the time was 15 min.

[0036] A composite insulating paper prepared using any of the methods described above.

[0037] The composite insulating paper preparation method provided by this invention uses PBO fibers as the network skeleton, BNNS@PDA and PVA@LM as thermally conductive units, and C8H... 10 O8 is the crosslinking agent, and PBO / BNNS@PDA and PVA@LM are crosslinked in C8H. 10 Under the action of O8, they cross-link with each other, promoting the establishment of a continuous thermally conductive channel between BNNS and LM, and finally forming a continuous thermally conductive network, thereby constructing a high thermal conductivity composite insulating paper to meet the needs of motor insulation systems.

[0038] The composite insulating paper provided by this invention exhibits significantly improved thermal conductivity compared to existing insulating papers. The preparation method for this composite insulating paper is simple, low-cost, and offers excellent performance at a high cost-effectiveness.

[0039] In this application, PBO is commercially available, obtained through polymerization of 4,6-diaminoresorcinol hydrochloride monomer and terephthalic acid monomer; boron nitride nanosheets (BNNS) are commercially available, obtained through experimental exfoliation of hexagonal h-BN boron nitride; Tris-base is commercially available; hydrochloric acid is obtained by dissolving HCl in deionized water; dopamine hydrochloride is commercially available; LM is commercially available, obtained through low-temperature melting of gallium and indium; PVA is commercially available; and C8H... 10 O8 and sodium hypophosphite were obtained through commercial purchase.

[0040] The present invention controls the film thickness to be between 1000μm and 1500μm, which can make the thermal conductivity and mechanical properties of the insulating paper even better. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the composite insulating paper structure provided by the present invention;

[0043] Figure 2 A comparison chart of the thermal conductivity of different BNNS@PDAs formed in Comparative Example 1 and Examples 1-4 of the present invention;

[0044] Figure 3 A comparison chart of thermal conductivity formed in Comparative Example 2 and Examples 1, 5-8 of the present invention with different PVA@LM contents;

[0045] Figure 4Comparison of thermal conductivity for films with different thicknesses formed in Examples 1, 9-12 of this invention. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0047] PBO, as a superfiber, is widely used in insulation systems due to its high specific strength, high specific modulus, good heat resistance, good flame retardancy, and excellent dielectric properties. However, the smooth surface and chemical inertness of PBO fibers affect their overall performance. Therefore, this invention utilizes PDA to enhance hydrogen bonding and the conjugation of π-π*, which can effectively improve the interfacial connection between BNNS and the matrix PBO, enhance the interaction between BNNS and PBO, and promote the construction of thermal conductive channels in BNNS.

[0048] This invention provides a method for preparing a high thermal conductivity composite insulating paper, comprising the following steps:

[0049] 1) Using 4,6-diaminoresorcinol hydrochloride monomer and terephthalic acid monomer as raw materials, and polyphosphoric acid as solvent, PBO is produced by polymerization reaction; the PBO obtained by polymerization is dissolved in polyphosphoric acid to prepare a PBO mixed solution with a concentration of 15% to 20%; the PBO mixed solution is subjected to dry-jet wet spinning at an environment of 90 to 120°C and a spinning speed of 10 to 12 mm / min to obtain nascent yarn; the nascent yarn is then subjected to water bath condensation setting, acid washing, drying, and hot stretching treatment to obtain PBO fiber.

[0050] In this step, PBO fibers are prepared by using a dry-jet wet spinning method to treat PBO. This is beneficial for closing the pores inside the fibers, forming a dense structure, and achieving a high degree of molecular chain orientation along the stress and fiber long axis. This results in PBO fibers with better strength and modulus. Using PBO with better strength and modulus to prepare composite insulating paper can enhance the mechanical properties of the composite insulating paper, making it more resistant to external forces and stresses during use and less prone to damage.

[0051] 2) Take 1g of lithium citrate and 1g of h-BN, add them to a mixed solution of deionized water and isopropanol with a volume ratio of 3:1, stir thoroughly, and then place it in an ultrasonic disperser for 15min, followed by ultrasonic treatment for 6h. Then transfer it to an electric thermostatic drying oven and heat it at 160℃~180℃ for 6h to prepare the exfoliated BNNS. Place BNNS and sodium hydroxide solution in a ball mill jar, ball mill it, wash the ball-milled mixture with deionized water, and finally dry the ball-milled mixture to obtain BNNS-OH. Take a certain amount of tris-hydroxymethylaminomethane (Tris-base) and add 0.1mol / L hydrochloric acid to adjust the pH of the solution to 8. 5. Prepare a Tris-HCl buffer solution with a concentration of 10 mmol / L and a hydrochloric acid solution with a concentration of 0.1 mol / L. Neutralize the Tris-HCl buffer solution and dopamine hydrochloride under alkaline conditions to obtain a dopamine solution. Mix the BNNS-OH, dopamine solution, and alcohol and stir magnetically at 20℃-35℃ for 18 hours to allow dopamine to spontaneously polymerize under alkaline conditions to obtain polydopamine PDA, thus completing the in-situ polymerization of BNNS and PDA. Then, filter, wash repeatedly, and dry to obtain the BNNS@PDA.

[0052] In this step, polydopamine (PDA) is obtained by the spontaneous polymerization of dopamine solution under alkaline conditions. Functionalizing BNNS-OH with PDA enhances the binding force between BNNS-OH and PBO. Specifically, BNNS-OH has a delocalized π-electron cloud on its surface, and PDA, a polymer with numerous conjugated structures, also possesses a delocalized π-electron cloud. When BNNS-OH and PDA come into contact, their π-electron clouds overlap, forming π-π* bonds. This interaction results in a strong adsorption force between BNNS-OH and PDA, contributing to increased binding strength. PDA molecules contain abundant functional groups such as hydroxyl (-OH) and amino (-NH2). The hydrogen atoms in these functional groups can form hydrogen bonds with nitrogen or oxygen atoms on the BNNS-OH surface. The formation of hydrogen bonds further enhances the interaction between BNNS-OH and PDA, improving their stability and compatibility. Therefore, in subsequent steps, using BNNS@PDA can significantly improve the bonding ability between BNNS and PBO fibers, thereby reducing the interfacial thermal resistance between BNNS and PBO and improving the thermal conductivity of the composite insulating paper. Furthermore, since PDA can directly adhere to the BNNS-OH surface during the self-polymerization of dopamine into PDA, the bond between BNNS-OH and PDA can be made tighter.

[0053] 3) Using gallium and indium as raw materials, gallium and indium are heated to 350-400°C with an alcohol lamp in a low-temperature melting process at a mass ratio of (0.3-3):1 to fully fuse gallium and indium, and finally gallium-indium alloy LM is prepared.

[0054] 4) Polyvinyl alcohol (PVA) and gallium indium alloy (LM) are uniformly mixed at a ratio of 1:(3-5) using ultrasonication, shearing, and stirring to obtain a spinning solution. The spinning solution is injected into a jetting device, which is then fixed to the injection pump of an electrospinning machine. A suitable fiber receiving device is selected, connected to the negative electrode and grounded, and placed directly below the needle. Spinning is performed using a receiving distance of 10-12 cm, a liquid-pushing speed of 0.1 mm / min, and a spinning voltage of 10-20 kV. The charged liquid is ejected from the Taylor cone, and under the action of the electric field, the ejected liquid forms long and thin nanofibers, which are deposited on the fiber receiving device to obtain PVA@LM nanofibers. The obtained PVA@LM nanofibers are collected and dried in a vacuum drying oven at 160℃ for 30 min.

[0055] In this step, since polyvinyl alcohol (PVA) has excellent thermal stability, the present invention can effectively disperse the metal filler gallium indium alloy (LM) in the PVA matrix through electrospinning, so that the prepared PVA@LM nanofibers have excellent thermal conductivity and thermal stability.

[0056] Furthermore, when there is a small amount of gallium indium alloy (LM) as a filler for polymer PVA, the filler LM is isolated by the polymer matrix and cannot form a thermally conductive network. When there is an excessive amount of filler LM, the system will gradually reach saturation, and the fillers will accumulate with each other, generating thermal resistance. The thermal conductivity of the composite material will improve very slowly. Therefore, this invention controls the mass ratio of polyvinyl alcohol (PVA) to gallium indium alloy (LM) at 1:(3-5), which can optimize the thermal conductivity and thermal stability of PVA@LM nanofibers, thereby optimizing the thermal conductivity and thermal stability of the final insulating paper.

[0057] 5) Add the PBO fibers prepared in step 1) to the BNNS@PDA prepared in step 2) and the PVA@LM nanofibers prepared in step 4) to deionized water, and obtain a uniformly mixed composite solution by high-speed shearing; the mass ratio of PBO, BNNS@PDA, PVA@LM and deionized water is 1:(0.1~0.3):(0.5~2):400, the high-speed shearing rate is 10000~25000 rpm, and the time is 15 min.

[0058] In this step, the present invention constructs a thermally conductive channel by combining the metal filler gallium indium alloy LM with BNNS. Since PDA contains a large number of catechol functional groups, the present invention utilizes the enhanced hydrogen bonding and π-π* conjugation effect of PDA to improve the interfacial compatibility and adhesion between BNNS-OH and PBO, thereby improving the mutual bonding ability between BNNS and PBO fibers and further improving the thermal conductivity of the insulating paper.

[0059] 6) Place the substrate on a horizontal surface and inject the composite solution mixed evenly in step 5) into the spray gun. The spray gun is tightly connected to the spraying device and sprayed onto the substrate under the action of electric field force to form a thin film with a thickness of 1000μm.

[0060] 7) C8H 10 O8 and sodium hypophosphite catalyst were dissolved in deionized water at a mass ratio of 2:1, C8H 10 The concentration of O8 is 0.2–0.3 mol / L.

[0061] 8) Immerse the film containing C8H prepared in step 7). 10 Immerse the film in the O8 solution for 5 minutes. After the film has fully absorbed the solution, remove the film and use absorbent paper to remove excess water from the surface.

[0062] In this step, the present invention uses C8H 10 O8, acting as a crosslinking agent, undergoes an esterification reaction with BNNS-OH and PVA, which can connect PBO fibers, BNNS@PDA, and PVA@LM, thus facilitating the formation of a thermally conductive network.

[0063] 9) Place the film in a vacuum oven and pre-dry it at 80°C for 15 minutes.

[0064] 10) Place the film in an environment of 150℃~190℃ for 10 min to cure and crosslink, then remove it and cool it to room temperature.

[0065] 11) Rinse the membrane with running water for 15 minutes and soak it in deionized water for 24 hours to remove excess ionic impurities.

[0066] 12) Place the film in a vacuum oven and vacuum dry it at 105°C for 20 minutes to obtain rough paper.

[0067] 13) High thermal conductivity composite insulating paper is prepared by hot pressing rough paper through a vacuum hot press at a temperature of 195℃ and a pressure of 20Mpa.

[0068] Example 1:

[0069] This embodiment provides a high thermal conductivity composite insulating paper, which is prepared by the following method:

[0070] 1) Using 4,6-diaminoresorcinol hydrochloride monomer and terephthalic acid monomer as raw materials, and polyphosphoric acid as solvent, PBO is produced by polymerization reaction. The PBO obtained by polymerization is dissolved in polyphosphoric acid to prepare a 20% PBO mixed solution. The PBO mixed solution is dry-jet wet-spun at 120°C and the spinning speed is 10 mm / min to obtain nascent yarn. Subsequently, the nascent yarn is subjected to water bath condensation setting, acid washing, drying and hot stretching treatment to obtain PBO fiber.

[0071] 2) Take 1g of lithium citrate and 1g of h-BN, add them to a mixture of deionized water and isopropanol in a volume ratio of 3:1, stir thoroughly, and then treat with an ultrasonic disperser for 15 minutes, followed by ultrasonic treatment for 6 hours. Transfer to an electric thermostatic drying oven and heat at 160℃ for 6 hours to prepare exfoliated BNNS. Place BNNS and sodium hydroxide solution in a ball mill jar for ball milling, wash the mixture after ball milling with deionized water, and finally dry the mixture to obtain BNNS-OH. Take a certain amount of tris-hydroxymethylaminomethane (Tris-base), add 0.1mol / L hydrochloric acid, and adjust the pH of the solution to 8.5. A Tris-HCl buffer solution with a concentration of 10 mmol / L was prepared, and the hydrochloric acid solution used had a concentration of 0.1 mol / L. The Tris-HCl buffer solution and dopamine hydrochloride were neutralized under alkaline conditions to obtain a dopamine solution. The BNNS-OH, dopamine solution, and alcohol were mixed and magnetically stirred at 20℃-35℃ for 18 hours to allow dopamine to spontaneously polymerize under alkaline conditions to obtain polydopamine PDA, thus completing the in-situ polymerization of BNNS and PDA. The mixture was then filtered, repeatedly washed, and dried to obtain the BNNS@PDA.

[0072] 3) Using gallium and indium as raw materials, gallium and indium are heated to 400°C with an alcohol lamp in a low-temperature melting process at a mass ratio of 3:1 to fully fuse them, and finally gallium-indium alloy LM is prepared.

[0073] 4) Polyvinyl alcohol (PVA) and gallium indium alloy (LM) are uniformly mixed at a ratio of 1:3 using ultrasonication, shearing, and stirring to obtain a spinning solution. The spinning solution is injected into a jetting device, which is then fixed to the injection pump of an electrospinning machine. A suitable fiber receiving device is selected, connected to the negative electrode and grounded, and placed directly below the needle. Spinning is performed using a receiving distance of 12 cm, a liquid-pushing speed of 0.1 mm / min, and a spinning voltage of 10 kV. The charged liquid is ejected from the Taylor cone, and under the action of the electric field, the ejected liquid forms long and thin nanofibers, which are deposited on the fiber receiving device to obtain PVA@LM nanofibers. The obtained PVA@LM nanofibers are collected and dried in a vacuum drying oven at 160℃ for 30 min.

[0074] 5) Add the PBO fibers prepared in step 1) to the BNNS@PDA prepared in step 2) and the PVA@LM nanofibers prepared in step 4) to deionized water, and obtain a uniformly mixed composite solution by high-speed shearing; wherein, the mass ratio of PBO, BNNS@PDA, PVA@LM and deionized water is 1:0.1:0.5:400, the high-speed shearing rate is 20000 rpm, and the time is 15 min;

[0075] 6) Place the substrate on a horizontal surface and inject the composite solution mixed evenly in step 5) into the spray gun. The spray gun is tightly connected to the spraying device and sprayed onto the substrate under the action of electric field force to form a thin film with a thickness of 1000μm.

[0076] 7) C8H 10 O8 and sodium hypophosphite catalyst were dissolved in deionized water at a mass ratio of 2:1, C8H 10 The concentration of O8 is 0.3 mol / L.

[0077] 8) Immerse the film containing C8H prepared in step 7). 10 Immerse the film in the O8 solution for 5 minutes. After the film has fully absorbed the solution, remove the film and use absorbent paper to remove excess water from the surface.

[0078] 9) Place the film in a vacuum oven and pre-dry it at 80°C for 15 minutes.

[0079] 10) Place the film in an environment of 190℃ for curing and crosslinking reaction for 10 min, then remove it and cool it to room temperature.

[0080] 11) Rinse the membrane with running water for 15 minutes and soak it in deionized water for 24 hours to remove excess ionic impurities.

[0081] 12) Place the film in a vacuum oven and vacuum dry it at 105°C for 20 minutes to obtain rough paper.

[0082] 13) High thermal conductivity composite insulating paper is prepared by hot pressing rough paper through a vacuum hot press at a temperature of 195℃ and a pressure of 20Mpa.

[0083] Figure 1 This is a schematic diagram of the composite insulating paper structure provided by the present invention, as shown below. Figure 1 As shown, this invention uses poly(p-phenylenebenzodioxazole) (PBO) as the network framework, boron nitride nanosheets (BNNS) and gallium indium alloy (LM) as thermally conductive elements, and butanetetracarboxylic acid (C8H2O) as the thermally conductive element. 10 Using O8 as a crosslinking agent, a continuous thermally conductive network is formed, which significantly improves the thermal conductivity of the composite insulating paper prepared by this invention. This effectively solves the problem of thermal aging of insulating paper and extends its service life. Furthermore, the prepared composite insulating paper can meet the high thermal conductivity requirements of electrical equipment such as transformers and generators with large capacity and high voltage levels.

[0084] Example 2:

[0085] This embodiment operates in the same way as Embodiment 1, except that in step 5), the mass ratio of PBO fiber, BNNS@PDA, PVA@LM, and deionized water is 1:0.2:0.5:400.

[0086] Example 3:

[0087] This embodiment operates in the same way as Embodiment 1, except that in step 5), the mass ratio of PBO fiber, BNNS@PDA, PVA@LM, and deionized water is 1:0.3:0.5:400.

[0088] Example 4:

[0089] This embodiment operates in the same way as Embodiment 1, except that in step 5), the mass ratio of PBO fiber, BNNS@PDA, PVA@LM, and deionized water is 1:0.4:0.5:400.

[0090] Example 5:

[0091] This embodiment operates in the same way as Embodiment 1, except that in step 5), the mass ratio of PBO fiber, BNNS@PDA, PVA@LM, and deionized water is 1:0.1:1:400.

[0092] Example 6:

[0093] This embodiment operates in the same way as Embodiment 1, except that in step 5), the mass ratio of PBO fiber, BNNS@PDA, PVA@LM, and deionized water is 1:0.1:1.5:400.

[0094] Example 7:

[0095] This embodiment operates in the same way as Embodiment 1, except that in step 5), the mass ratio of PBO fiber, BNNS@PDA, PVA@LM, and deionized water is 1:0.1:2:400.

[0096] Example 8:

[0097] This embodiment operates in the same way as Embodiment 1, except that in step 5), the mass ratio of PBO fiber, BNNS@PDA, PVA@LM, and deionized water is 1:0.1:2.5:400.

[0098] Example 9:

[0099] This embodiment operates in the same way as Embodiment 1, except that in step 6), the film thickness is 800 μm.

[0100] Example 10:

[0101] This embodiment operates in the same way as Embodiment 1, except that in step 6), the film thickness is 1200 μm.

[0102] Example 11:

[0103] This embodiment operates in the same way as Embodiment 1, except that in step 6), the film thickness is 1400 μm.

[0104] Example 12:

[0105] This embodiment operates in the same way as Embodiment 1, except that in step 6), the film thickness is 1600 μm.

[0106] Example 13:

[0107] This embodiment operates the same as Embodiment 1, except that: in step 1), the concentration of the PBO mixed solution is 15%; the dry-jet wet spinning temperature is 90℃; and the spinning speed is 11 mm / min; in step 2), the temperature of the electric thermostatic drying oven is 180℃; in step 3), the mass ratio of gallium to indium is 0.3:1; the alcohol lamp heating temperature is 350℃; in step 4), the mass ratio of polyvinyl alcohol (PVA) to gallium-indium alloy (LM) is 1:4; the receiving distance is 10 cm; the spinning voltage is 20 kV; and the drying temperature is 170℃; in step 5), the shear rate is 25000 rpm; in step 6), the film thickness is 1200 μm; and in step 7), C8H... 10 The concentration of O8 is 0.2 mol / L; in step 10), the curing and crosslinking temperature is 180℃; in step 13), the vacuum hot press temperature is 175℃.

[0108] Example 14:

[0109] This embodiment operates the same as Embodiment 1, except that: in step 1), the concentration of the PBO mixed solution is 18%; the dry-spinning temperature is 100℃; and the spinning speed is 12mm / min; in step 2), the temperature of the electric thermostatic drying oven is 170℃; in step 3), the mass ratio of gallium to indium is 2:1; and the alcohol lamp heating temperature is 380℃; in step 4), the mass ratio of polyvinyl alcohol (PVA) to gallium-indium alloy (LM) is 1:5; the receiving distance is 11cm; the spinning voltage is 15kV; and the drying temperature is 180℃; in step 5), the shear rate is 10000rpm; in step 6), the film thickness is 1500μm; and in step 7), C8H... 10 The concentration of O8 is 0.25 mol / L; in step 10), the curing and crosslinking temperature is 150℃; in step 13), the vacuum hot press temperature is 190℃.

[0110] Comparative Example 1:

[0111] This embodiment operates in the same way as Embodiment 1, except that the raw materials used in this embodiment do not contain BNNS@PDA, and the mass ratio of PBO fiber, PVA@LM, and deionized water is 1:0.5:400.

[0112] Comparative Example 2:

[0113] This embodiment operates in the same way as Embodiment 1, except that the raw materials used in this embodiment do not contain PVA@LM, and the mass ratio of PBO, BNNS@PDA, and deionized water is 1:0.1:400.

[0114] The thermal conductivity of Examples 1-4 and Comparative Example 1 of this invention was tested using an LFA467 flash thermal conductivity tester manufactured by Netzsch AG, Germany. The test results are shown in [Figure number missing]. Figure 2 The thermal conductivity of Examples 1, 5-8, and Comparative Example 2 of this invention was tested using an LFA467 flash thermal conductivity tester manufactured by Netzsch AG, Germany. The test results are shown in [Figure number missing]. Figure 3 The thermal conductivity of Examples 1 and 9-12 of this invention was tested using an LFA467 flash thermal conductivity tester manufactured by Netzsch AG, Germany. The test results are shown in [Figure number missing]. Figure 4 .Depend on Figure 2 It can be seen that the addition of BNNS@PDA in this invention significantly improves the thermal conductivity of insulating paper. As the BNNS@PDA content increases, the thermal conductivity of the insulating paper also increases. However, when the BNNS@PDA content is too high, the thermal conductivity of the insulating paper decreases to some extent. This is because after the addition reaches a certain level, the filler may agglomerate, preventing the formation of an effective thermal conduction path and hindering heat transfer. Comparative Example 1, which is a composite insulating paper without BNNS@PDA, has significantly lower thermal conductivity than the insulating paper prepared by this invention.

[0115] Depend on Figure 3 As can be seen, this invention further improves the thermal conductivity of insulating paper by adding PVA@LM. With the increase of PVA@LM content, the thermal conductivity of the insulating paper increases accordingly. Similarly, if the amount added is too high, the thermal conductivity of the insulating paper will decrease. Comparative Example 2, which is insulating paper without PVA@LM, has significantly lower thermal conductivity than the insulating paper obtained by this invention. This is because the composite insulating paper obtained by this invention uses BNNS@PDA and PVA@LM to jointly construct thermal conductive channels, establishing phonon transmission channels in all directions, thus significantly improving the thermal conductivity of the insulating paper.

[0116] Depend on Figure 4 It can be seen that the present invention can significantly improve the performance of insulating paper by controlling the film thickness to be between 1000 and 1500 μm. When the film thickness is large, the heat dissipation effect of the insulating paper is poor, and the thermal conductivity deteriorates accordingly; while when the film thickness is small, the insulating paper is easily damaged, and its mechanical properties are poor.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing composite insulating paper, characterized in that, include: Step 1: Functionalize boron nitride nanosheets BNNS with polydopamine PDA to obtain BNNS@PDA; Step 2: Gallium and indium are fully fused at a mass ratio of (0.3~3):1 at a temperature of 350~400 ℃ to prepare gallium-indium alloy LM; Step 3: The gallium indium alloy LM is used as a thermally conductive filler and dispersed in polyvinyl alcohol PVA by electrospinning to finally obtain dried PVA@LM nanofibers. Step 4: Add poly(p-phenylene benzodioxazole) PBO fibers and the BNNS@PDA and PVA@LM nanofibers to deionized water and shear to obtain a composite solution; the mass ratio of poly(p-phenylene benzodioxazole) PBO fibers, BNNS@PDA, PVA@LM nanofibers and deionized water is 1:(0.1~0.3):(0.5~2):400; the shearing rate is 10000~25000 rpm and the time is 15 min; The poly(p-phenylenebenzodioxazole) PBO fiber was prepared using the following method: Step a: Using 4,6-diaminoresorcinol hydrochloride monomer and terephthalic acid monomer as raw materials, and polyphosphoric acid as solvent, a polymerization reaction is carried out to produce PBO; Step b: Dissolve the polymerized PBO in polyphosphoric acid to prepare a PBO mixed solution with a concentration of 15%~20%; Step c: The PBO mixed solution is subjected to dry-jet wet spinning at an environment of 90~120℃ and a spinning speed of 10~12 mm / min to obtain nascent yarn; Step d: The nascent filaments are subjected to water bath condensation setting, acid washing, drying, and hot stretching treatment to obtain PBO fibers; Step 5: The composite solution is sprayed onto the substrate using an electrostatic spraying method to form a thin film; Step 6: Immerse the film in a solution containing C8H 10 After being immersed in the O8 solution for a certain period of time, the film was removed, dried, and then subjected to a curing and crosslinking reaction to obtain a cured and crosslinked film. The temperature of the curing and crosslinking reaction was 150℃~190℃, and the reaction time was 10min. Step 7: Cool, rinse, and dry the cured cross-linked film to obtain rough paper; Step 8: The rough paper is hot-pressed using a vacuum hot press to finally obtain the composite insulating paper.

2. The method for preparing composite insulating paper according to claim 1, characterized in that, In step 5, the thickness of the film is 1000 μm to 1500 μm.

3. The method for preparing composite insulating paper according to claim 1, characterized in that, Step 1 includes the following steps: Step a: Place BNNS and sodium hydroxide solution into a ball mill jar, ball mill, wash the mixture after ball milling with deionized water, and finally dry the mixture after ball milling to obtain BNNS-OH; Step b: Prepare a Tris-HCl buffer solution using Tris-base and hydrochloric acid solution; the pH of this Tris-HCl buffer solution is 8.5; Step c: Neutralize the Tris-HCl buffer solution and dopamine hydrochloride under alkaline conditions to obtain a dopamine solution; Step d: The BNNS-OH, dopamine solution, and alcohol are mixed and magnetically stirred at 20℃-35℃ for 18 hours to allow dopamine to spontaneously polymerize under alkaline conditions to obtain polydopamine PDA. The mixture is then filtered, repeatedly washed, and dried to obtain the BNNS@PDA.

4. The method for preparing composite insulating paper according to claim 1, characterized in that, Step 3 includes the following steps: Step a: The polyvinyl alcohol (PVA) and gallium indium alloy (LM) are mixed evenly by ultrasonication, shearing, and stirring to obtain a spinning solution; the mass ratio of PVA to LM is 1:(3~5). Step b: Inject the spinning solution into the jetting device and fix the jetting device on the injection pump of the electrospinning machine. Connect the fiber receiving device to the negative electrode and ground it, placing it directly below the needle. Spinning is performed using a receiving distance of 10~12 cm, a liquid pushing speed of 0.1 mm / min, and a spinning voltage of 10~20 kV to deposit PVA@LM nanofibers on the fiber receiving device. Collect the deposited PVA@LM nanofibers and dry them to obtain dried PVA@LM nanofibers. The drying temperature is 160~180℃, and the drying time is 30 min.

5. The method for preparing composite insulating paper according to claim 1, characterized in that, The one containing C8H 10 The solution of O8 is: C8H 10 The solution obtained by dissolving O8 and sodium hypophosphite in deionized water at a ratio of 2:1; the C8H 10 The concentration of O8 is 0.2~0.3 mol / L.

6. A composite insulating paper prepared by any one of the methods described in claims 1-5.

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