Roll-fired polyoxadiazole-based graphite film and preparation method thereof
By employing a multi-stage heating carbonization and graphitization process, the problems of poor flexibility and high cost in the production of polyoxadiazole graphite films have been solved, enabling the efficient preparation of roll-to-roll polyoxadiazole-based graphite films with good flexibility and high thermal conductivity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-22
- Publication Date
- 2026-03-20
AI Technical Summary
Existing polyoxadiazole graphite film production processes suffer from poor flexibility, low production efficiency, high cost, and significant losses, especially during the winding and firing process, which cannot be effectively implemented.
A multi-stage heating carbonization and graphitization process was adopted to prepare a roll-up polyoxadiazole-based graphite film by gradually increasing the temperature through the steps of preparing polyoxadiazole solution, polyoxadiazole polymer film, polyoxadiazole carbonized film and polyoxadiazole graphite film.
A roll-type polyoxadiazole-based graphite film with good flexibility and excellent performance was successfully prepared. The thermal conductivity was higher than 1530 W/m·k, with low product loss and low usage cost.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of graphite film production, and particularly relates to a roll-burn type polyoxadiazole-based graphite film and a preparation method thereof. BACKGROUND
[0002] At present, the graphite film used for heat dissipation can be divided into two categories. One is a graphene heat dissipation film synthesized by using graphene oxide as a raw material. The other is an artificial graphite heat dissipation film prepared by pyrolysis of a polymer film material. The graphene heat dissipation film synthesized by using graphene oxide as a raw material has poor performance, and the thermal conductivity is usually less than 1500 W / m·k, and the mechanical property is low. The graphite film prepared by pyrolysis of a polymer resin film has high efficiency.
[0003] The polymer resin film includes, for example, a polyimide film (PI) and a polyoxadiazole film. However, in the prior art, the graphite film manufactured by using polyoxadiazole cannot be roll-burned due to low flexibility and high rigidity. Therefore, the graphite film is usually produced by using a sheet or stack process. The production capacity is low, the labor cost is high, and a large amount of manpower is required for each process. In addition, about 10% of the film is lost in the next production process due to the sheet or stack form, and the use cost is high. SUMMARY
[0004] To solve at least one technical problem in the prior art, the present application provides a roll-burn type polyoxadiazole-based graphite film and a preparation method thereof. The preparation cost is low, and the roll-burn type polyoxadiazole-based graphite film has good performance. To achieve the above technical purpose, the technical solution adopted by the embodiments of the present application is as follows. In a first aspect, the present application provides a preparation method of a roll-burn type polyoxadiazole-based graphite film, including the following steps: Step S1, preparing a polyoxadiazole solution: polymerizing an aromatic dicarboxylic acid compound and a hydrazine salt in sulfuric acid to obtain a polyoxadiazole solution; Step S2, preparing a polyoxadiazole polymer film: casting the polyoxadiazole solution prepared in step S1 on a substrate to form a polyoxadiazole polymer layer, drying and stretching the polyoxadiazole polymer layer, and then performing heat preservation to obtain a polyoxadiazole polymer film; Step S3, preparing a polyoxadiazole carbonized film: placing the polyoxadiazole polymer film prepared in step S2 in a carbonization furnace to perform at least two carbonization treatments, and obtaining a polyoxadiazole carbonized film; Step S4, preparing a polyoxadiazole graphite film: placing the polyoxadiazole carbonized film prepared in step S3 in a graphitization furnace to perform at least two graphitization treatments, and obtaining a roll-burn type polyoxadiazole-based graphite film after cooling; Wherein, in any two adjacent carbonization processes, the temperature of the later carbonization process is higher than the temperature of the earlier carbonization process; and / or, in any two adjacent graphitization processes, the temperature of the later graphitization process is higher than the temperature of the earlier graphitization process.
[0005] Further, the preparation of the polyoxadiazole solution in step S1 includes: first, adding the first fuming sulfuric acid and concentrated sulfuric acid into a reaction vessel and stirring at 50-65°C for 0.1-1 h to prepare the second fuming sulfuric acid; then, adding the aromatic dicarboxylic acid compound into the reaction vessel and stirring at 50-65°C for 0.1-1 h; finally, adding the hydrazine salt into the reaction vessel at least three times, and obtaining the polyoxadiazole solution after the reaction. And / or, the preparation of the polyoxadiazole polymer film in step S2 includes: casting the polyoxadiazole solution obtained in step S1 onto a substrate to form a polyoxadiazole polymer layer; firstly, drying the polyoxadiazole polymer layer at 140-160°C; then, stretching the dried polyoxadiazole polymer layer longitudinally and / or laterally; finally, performing heat preservation, dehydration, and cyclization on the stretched polyoxadiazole polymer layer, and then winding it up to obtain the polyoxadiazole polymer film. And / or, the preparation of the polyoxadiazole carbonized film in step S3 includes: carbonizing the polyoxadiazole polymer film obtained in step S2 in a carbonization furnace under vacuum, at a first carbonization temperature, then at a second carbonization temperature, and finally at a third carbonization temperature to obtain the polyoxadiazole carbonized film. And / or, the preparation of the polyoxadiazole graphite film in step S4 includes: placing the polyoxadiazole carbonized film obtained in step S3 in a graphitization furnace, under inert gas protection, performing graphitization treatment at a first graphitization temperature, then performing graphitization treatment at a second graphitization temperature, and finally performing graphitization treatment at a third graphitization temperature, and obtaining the sintered polyoxadiazole-based graphite film after cooling.
[0006] Further, in step S1, the mass fraction of the second fuming sulfuric acid is 20-30%; And / or, the second fuming sulfuric acid comprises a first fuming sulfuric acid and concentrated sulfuric acid in a molar ratio of (0.8–1.2):(0.8–1.2); wherein the mass fraction of the first fuming sulfuric acid is 45–55%, and the concentration of the concentrated sulfuric acid is 98%; And / or, the aromatic dicarboxylic acid compound comprises terephthalic acid and isophthalic acid in a molar ratio of (18-22):(0.8-1.2); And / or, the hydrazine salt comprises hydrazine sulfate with a mass fraction of 5-10%; And / or, the hydrazine salt is added to the reactor in 3 to 5 portions; And / or, the solid content of the polyoxadiazole solution is 8-12%.
[0007] Furthermore, in step S2, the stretching ratio of the transverse stretching is 1.3 to 1.33; And / or, the longitudinal stretching ratio is 1.02 to 1.04.
[0008] Furthermore, in step S2, the heat preservation includes a first heat preservation, wherein the heat preservation temperature of the first heat preservation is 75-85℃ and the heat preservation time is 20-40min; And / or, the insulation further includes a second insulation, wherein the insulation temperature of the second insulation is 90-110℃ and the insulation time is 20-40 min; And / or, the insulation further includes a third insulation, wherein the insulation temperature of the third insulation is 140-160℃ and the insulation time is 20-40 minutes; And / or, the insulation further includes a fourth insulation, wherein the insulation temperature of the fourth insulation is 190-210℃ and the insulation time is 20-40 min; And / or, the thickness of the polyoxadiazole polymer film is 150µm.
[0009] Furthermore, in step S3, the carbonization temperature for the first carbonization is 500–650°C, and the carbonization time is 30–60 minutes. And / or, the carbonization temperature of the second carbonization is 800–850°C, and the carbonization time is 30–60 min. And / or, the carbonization temperature of the third carbonization is 1300-1500℃, and the carbonization time is 30-60 min.
[0010] Furthermore, in step S3, the heating rate for the first carbonization is 3–5 °C / min. And / or, the heating rate for the second carbonization is 3–5 °C / min. And / or, the heating rate for the third carbonization is 3 to 5 °C / min.
[0011] Furthermore, in step S4, the graphitization temperature of the first graphitization is 1800℃~2200℃, and the graphitization time is 60~90min; And / or, the graphitization temperature of the second graphitization is 2400℃~2600℃, and the graphitization time is 60~90min; And / or, the graphitization temperature of the third graphitization is 2800℃~3000℃, and the graphitization time is 90~120min; And / or, the inert gas includes argon.
[0012] Furthermore, in step S4, the heating rate for the first graphitization is 20-30°C / min; And / or, the heating rate for the second graphitization is 20–30 °C / min; And / or, the heating rate for the third graphitization is 20–30 °C / min.
[0013] Secondly, embodiments of the present invention provide a sintered polyoxadiazole-based graphite film prepared by the above-described method for preparing a sintered polyoxadiazole-based graphite film. The sintered polyoxadiazole-based graphite film is calendered using a roll press, and the density of the calendered sintered polyoxadiazole-based graphite film is 2.2 g / cm³. 3 above.
[0014] The beneficial effects of the technical solution provided by the embodiments of the present invention are as follows: (1) The method for preparing the sintered polyoxadiazole-based graphite film provided in the embodiments of the present invention successfully prepares the sintered polyoxadiazole-based graphite film by staged heating of the carbonization process and the graphitization process. Compared with the prior art, which can only produce sheet-like or stacked polyoxadiazole-based graphite films, the synthesis process is relatively simple. The prepared sintered polyoxadiazole-based graphite film has good flexibility, good performance, high defect level, and thermal conductivity greater than 1530W / m·k. The product loss is small and the usage cost is low. Detailed Implementation
[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0016] Furthermore, it should be understood that after reading the contents disclosed in this invention, those skilled in the art can make various alterations or modifications to this invention, and these equivalent forms also fall within the protection scope defined by this invention.
[0017] This invention provides a method for preparing a roll-up polyoxadiazole-based graphite film, comprising the following steps: Step S1, Preparation of polyoxadiazole solution: Aromatic dicarboxylic acid compound and hydrazine salt are polymerized in sulfuric acid to obtain polyoxadiazole solution; Step S2, preparation of polyoxadiazole polymer film: The polyoxadiazole solution obtained in step S1 is cast onto a substrate to form a polyoxadiazole polymer layer. The polyoxadiazole polymer layer is dried, stretched, and then kept at a temperature to obtain a polyoxadiazole polymer film. Step S3, preparing polyoxadiazole carbonized film: the polyoxadiazole polymer film obtained in step S2 is placed in a carbonization furnace for at least two carbonization treatments to obtain polyoxadiazole carbonized film; Step S4, Preparation of polyoxadiazole graphite film: The polyoxadiazole carbonized film obtained in step S3 is placed in a graphitization furnace for at least two graphitization treatments, and after cooling, a rolled polyoxadiazole-based graphite film is obtained. Wherein, in any two adjacent carbonization processes, the temperature of the later carbonization process is higher than the temperature of the earlier carbonization process; and / or, in any two adjacent graphitization processes, the temperature of the later graphitization process is higher than the temperature of the earlier graphitization process.
[0018] Further, the preparation of the polyoxadiazole solution in step S1 includes: first, adding the first fuming sulfuric acid and concentrated sulfuric acid into a reaction vessel and stirring at 50-65°C for 0.1-1 h to prepare the second fuming sulfuric acid; then, adding the aromatic dicarboxylic acid compound into the reaction vessel and stirring at 50-65°C for 0.1-1 h; finally, adding the hydrazine salt into the reaction vessel at least three times, and obtaining the polyoxadiazole solution after the reaction. And / or, the preparation of the polyoxadiazole polymer film in step S2 includes: casting the polyoxadiazole solution obtained in step S1 onto a substrate to form a polyoxadiazole polymer layer; firstly, drying the polyoxadiazole polymer layer at 140-160°C; then, stretching the dried polyoxadiazole polymer layer longitudinally and / or laterally; finally, performing heat preservation, dehydration, and cyclization on the stretched polyoxadiazole polymer layer, and then winding it up to obtain the polyoxadiazole polymer film. And / or, the preparation of the polyoxadiazole carbonized film in step S3 includes: carbonizing the polyoxadiazole polymer film obtained in step S2 in a carbonization furnace under vacuum, at a first carbonization temperature, then at a second carbonization temperature, and finally at a third carbonization temperature to obtain the polyoxadiazole carbonized film. And / or, the preparation of the polyoxadiazole graphite film in step S4 includes: placing the polyoxadiazole carbonized film obtained in step S3 in a graphitization furnace, under inert gas protection, performing graphitization treatment at a first graphitization temperature, then performing graphitization treatment at a second graphitization temperature, and finally performing graphitization treatment at a third graphitization temperature, and obtaining the sintered polyoxadiazole-based graphite film after cooling.
[0019] Further, in step S1, the mass fraction of the second fuming sulfuric acid is 20-30%; And / or, the second fuming sulfuric acid comprises a first fuming sulfuric acid and concentrated sulfuric acid in a molar ratio of (0.8–1.2):(0.8–1.2); wherein the mass fraction of the first fuming sulfuric acid is 45–55%, and the concentration of the concentrated sulfuric acid is 98%; And / or, the aromatic dicarboxylic acid compound comprises terephthalic acid and isophthalic acid in a molar ratio of (18-22):(0.8-1.2); And / or, the hydrazine salt comprises hydrazine sulfate with a mass fraction of 5-10%; And / or, the hydrazine salt is added to the reactor in 3 to 5 portions; And / or, the solid content of the polyoxadiazole solution is 8-12%, for example, it can be 8%, 9%, 10%, 11%, 12%, etc.
[0020] Furthermore, in step S2, the stretching ratio of the transverse stretching is 1.3 to 1.33; And / or, the longitudinal stretching ratio is 1.02 to 1.04.
[0021] Furthermore, in step S2, the heat preservation includes a first heat preservation, wherein the heat preservation temperature of the first heat preservation is 75-85℃ and the heat preservation time is 20-40min; for example, the temperature can be 75℃, 77℃, 80℃, 82℃, 85℃, etc., and the time can be 20min, 25min, 30min, 35min, 40min, etc. And / or, the insulation further includes a second insulation, wherein the insulation temperature of the second insulation is 90-110℃ and the insulation time is 20-40min; for example, the temperature can be 90℃, 95℃, 100℃, 105℃, 110℃, etc., and the time can be 20min, 25min, 30min, 35min, 40min, etc. And / or, the insulation further includes a third insulation, wherein the insulation temperature of the third insulation is 140-160℃ and the insulation time is 20-40min; for example, the temperature can be 140℃, 145℃, 150℃, 155℃, 160℃, etc., and the time can be 20min, 25min, 30min, 35min, 40min, etc. And / or, the heat preservation further includes a fourth heat preservation, wherein the heat preservation temperature of the fourth heat preservation is 190-210℃ and the heat preservation time is 20-40min; for example, the temperature can be 190℃, 195℃, 200℃, 205℃, 210℃, etc., and the time can be 20min, 25min, 30min, 35min, 40min, etc. And / or, the thickness of the polyoxadiazole polymer film is 150µm.
[0022] Furthermore, in step S3, the carbonization temperature of the first carbonization is 500-650℃, and the carbonization time is 30-60min. For example, the temperature can be 500℃, 520℃, 550℃, 580℃, 600℃, 620℃, 650℃, etc., and the time can be 30min, 40min, 50min, 60min, etc. And / or, the carbonization temperature of the second carbonization is 800-850℃, and the carbonization time is 30-60min. For example, the temperature can be 800℃, 810℃, 820℃, 840℃, 850℃, etc., and the time can be 30min, 40min, 50min, 60min, etc. And / or, the carbonization temperature of the third carbonization is 1300-1500℃, and the carbonization time is 30-60min. For example, the temperature can be 1300℃, 1350℃, 1400℃, 1450℃, 1500℃, etc., and the time can be 30min, 40min, 50min, 60min, etc.
[0023] Furthermore, in step S3, the heating rate of the first carbonization is 3 to 5 °C / min, for example, it can be 3 °C / min, 3.5 °C / min, 4 °C / min, 4.5 °C / min, 5 °C / min, etc.; And / or, the heating rate of the second carbonization is 3 to 5 °C / min, for example, it can be 3 °C / min, 3.5 °C / min, 4 °C / min, 4.5 °C / min, 5 °C / min, etc.; And / or, the heating rate of the third carbonization is 3 to 5 °C / min, for example, it can be 3 °C / min, 3.5 °C / min, 4 °C / min, 4.5 °C / min, 5 °C / min, etc.
[0024] Furthermore, in step S4, the graphitization temperature of the first graphitization is 1800℃~2200℃, and the graphitization time is 60~90min. For example, the temperature can be 1800℃, 1900℃, 2000℃, 2100℃, 2200℃, etc., and the time can be 60min, 70min, 80min, 90min, etc. And / or, the graphitization temperature of the second graphitization is 2400℃~2600℃, and the graphitization time is 60~90min. For example, the temperature can be 2400℃, 2450℃, 2500℃, 2550℃, 2600℃, etc., and the time can be 60min, 70min, 80min, 90min, etc. And / or, the graphitization temperature of the third graphitization is 2800℃~3000℃, and the graphitization time is 90~120min. For example, the temperature can be 2800℃, 2850℃, 2900℃, 2950℃, 3000℃, etc., and the time can be 90min, 100min, 110min, 120min, etc.
[0025] And / or, the inert gas includes argon.
[0026] Furthermore, in step S4, the heating rate of the first graphitization is 20-30℃ / min, for example, it can be 20℃ / min, 23℃ / min, 25℃ / min, 27℃ / min, 30℃ / min, etc. And / or, the heating rate of the second graphitization is 20-30℃ / min, for example, it can be 20℃ / min, 23℃ / min, 25℃ / min, 27℃ / min, 30℃ / min, etc.; And / or, the heating rate of the third graphitization is 20 to 30 °C / min, for example, it can be 20 °C / min, 23 °C / min, 25 °C / min, 27 °C / min, 30 °C / min, etc.
[0027] Secondly, embodiments of the present invention provide a sintered polyoxadiazole-based graphite film prepared by the above-described method for preparing a sintered polyoxadiazole-based graphite film. The sintered polyoxadiazole-based graphite film is calendered using a roll press, and the density of the calendered sintered polyoxadiazole-based graphite film is 2.2 g / cm³. 3 above.
[0028] In the following specific embodiments, operations not specified under certain conditions are performed under standard conditions or conditions recommended by the manufacturer. All raw materials without specified manufacturers and specifications are commercially available products.
[0029] Example 1 A method for preparing a roll-up polyoxadiazole-based graphite film includes the following steps: Step S1, preparing polyoxadiazole solution: First, 50% fuming sulfuric acid and 98% concentrated sulfuric acid are added to a reaction vessel at a molar ratio of 1:1 and stirred at 50°C for 0.5 h to fully mix the fuming sulfuric acid and concentrated sulfuric acid to prepare 25% fuming sulfuric acid; then, terephthalic acid and isophthalic acid are added to the reaction vessel at a molar ratio of 20:1 and stirred at 50°C for 0.5 h to fully dissolve in the fuming sulfuric acid solvent; finally, 5% hydrazine sulfate is added to the reaction vessel in three portions, and after the reaction, the polyoxadiazole solution with a solid content of 10% is obtained. Step S2, preparation of polyoxadiazole polymer film: The polyoxadiazole solution obtained in step S1 is cast onto a glass substrate to form a polyoxadiazole polymer layer. First, the polyoxadiazole polymer layer is dried at 150°C. Then, the dried polyoxadiazole polymer layer is stretched longitudinally and laterally, with a longitudinal stretching ratio of 1.02 and a lateral stretching ratio of 1.3. Finally, the stretched polyoxadiazole polymer layer is subjected to dehydration and cyclization by sequentially holding it at 80°C for 30 min, at 100°C for 30 min, at 150°C for 30 min, and at 200°C for 30 min. After winding, a polyoxadiazole polymer film with a thickness of 150µm is obtained. Step S3, preparation of polyoxadiazole carbonized film: The polyoxadiazole polymer film obtained in step S2 is placed in a carbonization furnace under vacuum. First, the temperature is increased to 600°C at a heating rate of 3°C / min and held for 30 min. Then, the temperature is increased to 800°C at a heating rate of 3°C / min and held for 30 min. Finally, the temperature is increased to 1300°C at a heating rate of 3°C / min and held for 30 min to obtain the polyoxadiazole carbonized film. Step S4, Preparation of polyoxadiazole graphite film: The polyoxadiazole carbonized film obtained in step S3 is placed in a graphitization furnace under argon protection. First, the temperature is increased to 2200℃ at a heating rate of 20℃ / min and held for 60min. Then, the temperature is increased to 2400℃ at a heating rate of 20℃ / min and held for 60-90min. Finally, the temperature is increased to 2800℃ at a heating rate of 20℃ / min and held for 90min. After natural cooling, the sintered polyoxadiazole-based graphite film is obtained.
[0030] The sintered polyoxadiazole-based graphite film was calendered using a roller press, and the density of the calendered sintered polyoxadiazole-based graphite film was 2.2 g / cm³. 3 above.
[0031] Example 2 A method for preparing a roll-up polyoxadiazole-based graphite film includes the following steps: Step S1, preparation of polyoxadiazole solution: First, 50% fuming sulfuric acid and 98% concentrated sulfuric acid are added to a reaction vessel in a 1:1 ratio and stirred at 60°C for 0.5 h to fully mix the fuming sulfuric acid and concentrated sulfuric acid to prepare 25% fuming sulfuric acid; then, terephthalic acid and isophthalic acid are added to the reaction vessel in a 20:1 ratio and stirred at 60°C for 0.5 h to fully dissolve in the fuming sulfuric acid solvent; finally, 7% hydrazine sulfate is added to the reaction vessel in 4 portions, and after the reaction, a polyoxadiazole solution with a solid content of 10% is obtained. Step S2, preparation of polyoxadiazole polymer film: The polyoxadiazole solution obtained in step S1 is cast onto a glass substrate to form a polyoxadiazole polymer layer. First, the polyoxadiazole polymer layer is dried at 150°C. Then, the dried polyoxadiazole polymer layer is stretched longitudinally and laterally, with a longitudinal stretching ratio of 1.03 and a lateral stretching ratio of 1.32. Finally, the stretched polyoxadiazole polymer layer is subjected to dehydration and cyclization by sequentially holding it at 80°C for 30 min, at 100°C for 30 min, at 150°C for 30 min, and at 200°C for 30 min. After winding, a polyoxadiazole polymer film with a thickness of 150µm is obtained. Step S3, preparation of polyoxadiazole carbonized film: The polyoxadiazole polymer film obtained in step S2 is placed in a carbonization furnace under vacuum. First, the temperature is increased to 600°C at a heating rate of 4°C / min and held for 30 min. Then, the temperature is increased to 800°C at a heating rate of 4°C / min and held for 30 min. Finally, the temperature is increased to 1400°C at a heating rate of 4°C / min and held for 30 min to obtain the polyoxadiazole carbonized film. Step S4, Preparation of polyoxadiazole graphite film: The polyoxadiazole carbonized film obtained in step S3 is placed in a graphitization furnace under argon protection. First, the temperature is increased to 2200℃ at a heating rate of 25℃ / min and held for 75min. Then, the temperature is increased to 2400℃ at a heating rate of 25℃ / min and held for 75min. Finally, the temperature is increased to 2900℃ at a heating rate of 25℃ / min and held for 100min. After natural cooling, the sintered polyoxadiazole-based graphite film is obtained.
[0032] The sintered polyoxadiazole-based graphite film was calendered using a roller press, and the density of the calendered sintered polyoxadiazole-based graphite film was 2.2 g / cm³. 3 above.
[0033] Example 3 A method for preparing a roll-up polyoxadiazole-based graphite film includes the following steps: Step S1, preparation of polyoxadiazole solution: First, 50% fuming sulfuric acid and 98% concentrated sulfuric acid are added to a reaction vessel in a 1:1 ratio and stirred at 65°C for 0.5 h to fully mix the fuming sulfuric acid and concentrated sulfuric acid to prepare 25% fuming sulfuric acid; then, terephthalic acid and isophthalic acid are added to the reaction vessel in a 20:1 ratio and stirred at 65°C for 0.5 h to fully dissolve in the fuming sulfuric acid solvent; finally, 10% hydrazine sulfate is added to the reaction vessel in 5 portions, and after the reaction, a polyoxadiazole solution with a solid content of 10% is obtained.
[0034] Step S2, preparation of polyoxadiazole polymer film: The polyoxadiazole solution obtained in step S1 is cast onto a glass substrate to form a polyoxadiazole polymer layer. First, the polyoxadiazole polymer layer is dried at 150°C. Then, the dried polyoxadiazole polymer layer is stretched longitudinally and laterally, with a longitudinal stretching ratio of 1.04 and a lateral stretching ratio of 1.33. Finally, the stretched polyoxadiazole polymer layer is subjected to dehydration and cyclization by sequentially holding it at 80°C for 30 min, at 100°C for 30 min, at 150°C for 30 min, and at 200°C for 30 min. After winding, a polyoxadiazole polymer film with a thickness of 150µm is obtained. Step S3, preparation of polyoxadiazole carbonized film: The polyoxadiazole polymer film obtained in step S2 is placed in a carbonization furnace under vacuum. First, the temperature is increased to 600°C at a heating rate of 5°C / min and held for 30 min. Then, the temperature is increased to 800°C at a heating rate of 5°C / min and held for 30 min. Finally, the temperature is increased to 1500°C at a heating rate of 5°C / min and held for 30 min to obtain the polyoxadiazole carbonized film. Step S4, Preparation of polyoxadiazole graphite film: The polyoxadiazole carbonized film obtained in step S3 is placed in a graphitization furnace under argon protection. First, the temperature is increased to 2200℃ at a heating rate of 30℃ / min and held for 90min. Then, the temperature is increased to 2400℃ at a heating rate of 30℃ / min and held for 90min. Finally, the temperature is increased to 3000℃ at a heating rate of 30℃ / min and held for 120min. After natural cooling, the sintered polyoxadiazole-based graphite film is obtained.
[0035] The sintered polyoxadiazole-based graphite film was calendered using a roller press, and the density of the calendered sintered polyoxadiazole-based graphite film was 2.2 g / cm³. 3 above.
[0036] Comparative Example 1 A method for preparing a polyoxadiazole graphite film includes the following steps: Step S1, preparation of polyoxadiazole solution: First, 50% fuming sulfuric acid and 98% concentrated sulfuric acid are added to a reaction vessel in a 1:1 ratio and stirred at 50°C for 0.5 h to fully mix the fuming sulfuric acid and concentrated sulfuric acid to prepare 25% fuming sulfuric acid; then, terephthalic acid and isophthalic acid are added to the reaction vessel in a 20:1 ratio and stirred at 50°C for 0.5 h to fully dissolve in the fuming sulfuric acid solvent; finally, 5% hydrazine sulfate is added to the reaction vessel, and after the reaction, a polyoxadiazole solution with a solid content of 10% is obtained.
[0037] Step S2, preparation of polyoxadiazole-based graphite film: The polyoxadiazole solution obtained in step S1 is cast onto a glass substrate to form a polyoxadiazole polymer layer. First, the polyoxadiazole polymer layer is dried at 150°C. Then, the dried polyoxadiazole polymer layer is stretched longitudinally and laterally, with a longitudinal stretching ratio of 1.02 and a lateral stretching ratio of 1.3. Finally, the stretched polyoxadiazole polymer layer is kept at 200°C for 30 minutes for dehydration and cyclization. After winding, a polyoxadiazole polymer film with a thickness of 150 μm is obtained. Step S3, preparation of polyoxadiazole carbonized film: The polyoxadiazole polymer film obtained in step S2 is heated to 1500℃ at a heating rate of 5℃ / min and held for 30min under vacuum to obtain polyoxadiazole carbonized film. Step S4, preparation of polyoxadiazole graphite film: The polyoxadiazole carbonized film obtained in step S3 is heated to 3000℃ in a graphitization furnace under argon protection, first heated at a heating rate of 30℃ / min and held at that temperature for 120min, and then cooled naturally to obtain the polyoxadiazole graphite film.
[0038] The polyoxadiazole graphite film was calendered using a roller press, and the density of the calendered polyoxadiazole graphite film was 2.2 g / cm³. 3 above.
[0039] Application Examples This application example evaluates the defect level and thermal conductivity of the roll-to-roll polyoxadiazole-based graphite films provided in Examples 1-3 and the polyoxadiazole-based graphite film provided in Comparative Example 1. Specifically, roll-to-roll polyoxadiazole-based graphite films of the same mass provided in Examples 1-3 and the polyoxadiazole-based graphite film provided in Comparative Example 1 were selected as samples. The number of joints in the polyoxadiazole-based graphite films was observed visually. The thermal conductivity of the four samples was tested according to the method provided in the standard GB / T22588-2008 "Measurement of Thermal Diffusion Coefficient or Thermal Conductivity by Flash Method". The specific test parameters of the roll-to-roll polyoxadiazole-based graphite films provided in Examples 1-3 and the polyoxadiazole-based graphite film provided in Comparative Example 1 are detailed in Table 1 below.
[0040] Table 1 Performance test results of polyoxadiazole graphite films in Examples 1-3 and Comparative Example 1 Among the defect levels, S level: 0 joints; A level: <5 joints; B level: 5 to 10 joints; C level: >10 joints. The joints refer to the places in the 200m polyoxadiazole graphite film where there are breaks and they are connected with tape.
[0041] As shown in Table 1, the polyoxadiazole-based graphite film provided in the comparative example has a large number of joints and a poor defect level. However, using the roll-to-roll polyoxadiazole-based graphite film provided in Examples 1-3 of this application, a roll-to-roll morphology polyoxadiazole-based graphite film can be successfully prepared. Furthermore, the prepared roll-to-roll polyoxadiazole-based graphite film has fewer than 5 joints, a defect level of A or higher, and a thermal conductivity of 1530 W / m·K or higher. It exhibits excellent performance, a simple preparation process, low cost, and a good morphology, which is beneficial for subsequent processes.
[0042] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A method for preparing a roll-up polyoxadiazole-based graphite film, characterized in that, Includes the following steps: Step S1, Preparation of polyoxadiazole solution: Aromatic dicarboxylic acid compound and hydrazine salt are polymerized in sulfuric acid to obtain polyoxadiazole solution; Step S2, preparation of polyoxadiazole polymer film: The polyoxadiazole solution obtained in step S1 is cast onto a substrate to form a polyoxadiazole polymer layer. The polyoxadiazole polymer layer is dried, stretched, and then kept at a temperature to obtain a polyoxadiazole polymer film. Step S3, preparing polyoxadiazole carbonized film: the polyoxadiazole polymer film obtained in step S2 is placed in a carbonization furnace for at least two carbonization treatments to obtain polyoxadiazole carbonized film; Step S4, Preparation of polyoxadiazole graphite film: The polyoxadiazole carbonized film obtained in step S3 is placed in a graphitization furnace for at least two graphitization treatments, and after cooling, a rolled polyoxadiazole-based graphite film is obtained. Wherein, in any two adjacent carbonization processes, the temperature of the later carbonization process is higher than the temperature of the earlier carbonization process; and / or, in any two adjacent graphitization processes, the temperature of the later graphitization process is higher than the temperature of the earlier graphitization process.
2. The method for preparing the roll-up polyoxadiazole-based graphite film as described in claim 1, characterized in that, The preparation of the polyoxadiazole solution in step S1 includes: first, adding the first fuming sulfuric acid and concentrated sulfuric acid into a reaction vessel and stirring at 50-65°C for 0.1-1 h to prepare the second fuming sulfuric acid; then, adding the aromatic dicarboxylic acid compound into the reaction vessel and stirring at 50-65°C for 0.1-1 h; finally, adding the hydrazine salt into the reaction vessel at least three times, and obtaining the polyoxadiazole solution after the reaction. And / or, the preparation of the polyoxadiazole polymer film in step S2 includes: casting the polyoxadiazole solution obtained in step S1 onto a substrate to form a polyoxadiazole polymer layer; firstly, drying the polyoxadiazole polymer layer at 140-160°C; then, stretching the dried polyoxadiazole polymer layer longitudinally and / or laterally; finally, performing heat preservation, dehydration, and cyclization on the stretched polyoxadiazole polymer layer, and then winding it up to obtain the polyoxadiazole polymer film. And / or, the preparation of the polyoxadiazole carbonized film in step S3 includes: carbonizing the polyoxadiazole polymer film obtained in step S2 in a carbonization furnace under vacuum, at a first carbonization temperature, then at a second carbonization temperature, and finally at a third carbonization temperature to obtain the polyoxadiazole carbonized film. And / or, the preparation of the polyoxadiazole graphite film in step S4 includes: placing the polyoxadiazole carbonized film obtained in step S3 in a graphitization furnace, under inert gas protection, performing graphitization treatment at a first graphitization temperature, then performing graphitization treatment at a second graphitization temperature, and finally performing graphitization treatment at a third graphitization temperature, and obtaining the sintered polyoxadiazole-based graphite film after cooling.
3. The method for preparing the roll-up polyoxadiazole-based graphite film as described in claim 2, characterized in that, In step S1, the mass fraction of the second fuming sulfuric acid is 20-30%; And / or, the second fuming sulfuric acid comprises a first fuming sulfuric acid and concentrated sulfuric acid in a molar ratio of (0.8-1.2):(0.8-1.2); wherein the mass fraction of the first fuming sulfuric acid is 45-55%, and the concentration of the concentrated sulfuric acid is 98%; And / or, the aromatic dicarboxylic acid compound comprises terephthalic acid and isophthalic acid in a molar ratio of (18-22):(0.8-1.2); And / or, the hydrazine salt comprises hydrazine sulfate with a mass fraction of 5-10%; And / or, the hydrazine salt is added to the reactor in 3 to 5 portions; And / or, the solid content of the polyoxadiazole solution is 8-12%.
4. The method for preparing the roll-up polyoxadiazole-based graphite film as described in claim 2, characterized in that, In step S2, the stretching ratio of the transverse stretching is 1.3 to 1.33; And / or, the longitudinal stretching ratio is 1.02 to 1.
04.
5. The method for preparing the roll-up polyoxadiazole-based graphite film as described in claim 2, characterized in that, In step S2, the heat preservation includes a first heat preservation, wherein the heat preservation temperature of the first heat preservation is 75-85℃ and the heat preservation time is 20-40min; And / or, the insulation further includes a second insulation, wherein the insulation temperature of the second insulation is 90-110℃ and the insulation time is 20-40 min; And / or, the insulation further includes a third insulation, wherein the insulation temperature of the third insulation is 140-160℃ and the insulation time is 20-40 minutes; And / or, the insulation further includes a fourth insulation, wherein the insulation temperature of the fourth insulation is 190-210℃ and the insulation time is 20-40 min; And / or, the thickness of the polyoxadiazole polymer film is 150µm.
6. The method for preparing the roll-up polyoxadiazole-based graphite film as described in claim 2, characterized in that, In step S3, the carbonization temperature for the first carbonization is 500–650°C, and the carbonization time is 30–60 minutes. And / or, the carbonization temperature of the second carbonization is 800–850°C, and the carbonization time is 30–60 min. And / or, the carbonization temperature of the third carbonization is 1300-1500℃, and the carbonization time is 30-60 min.
7. The method for preparing the roll-up polyoxadiazole-based graphite film as described in claim 2, characterized in that, In step S3, the heating rate for the first carbonization is 3–5 °C / min. And / or, the heating rate for the second carbonization is 3–5 °C / min. And / or, the heating rate for the third carbonization is 3 to 5 °C / min.
8. The method for preparing the roll-up polyoxadiazole-based graphite film as described in claim 2, characterized in that, In step S4, the graphitization temperature of the first graphitization is 1800℃~2200℃, and the graphitization time is 60~90min; And / or, the graphitization temperature of the second graphitization is 2400℃~2600℃, and the graphitization time is 60~90min; And / or, the graphitization temperature of the third graphitization is 2800℃~3000℃, and the graphitization time is 90~120min; And / or, the inert gas includes argon.
9. The method for preparing the roll-up polyoxadiazole-based graphite film as described in claim 2, characterized in that, In step S4, the heating rate for the first graphitization is 20-30°C / min; And / or, the heating rate for the second graphitization is 20–30 °C / min; And / or, the heating rate for the third graphitization is 20–30 °C / min.
10. The spun-on polyoxadiazole-based graphite film prepared by the method according to any one of claims 1 to 8 is characterized in that, The sintered polyoxadiazole-based graphite film is calendered using a roll press, and the density of the calendered sintered polyoxadiazole-based graphite film is 2.2 g / cm³. 3 above.