Polyimide graphite composite material as well as preparation method and application thereof

Abstract

The invention discloses a polyimide-graphite composite material and a preparation method and application thereof, and the polyimide-graphite composite material comprises the following components in percentage by mass: 80-95% of polyimide and 5-20% of graphite. The polyimide is a polyimide terminated polymer containing an aromatic anhydride terminated end. The acid anhydride containing aryl is used for blocking, so that the polarity of an amino-terminated group is reduced, the structure of the aryl (benzene) is similar to that of graphite, and the compatibility of polyimide and graphite is improved; besides, after the amino-terminated group of the polyimide is terminated, the polyimide is prevented from further amidation reaction, so that the generation of condensed water is greatly reduced, the generation of bubbles in the plasticizing process is effectively controlled, and the quality and the use performance of the composite material are improved.

Description

Technical Field

[0001] The invention relates to the technical field of new composite materials, and in particular to a polyimide graphite composite material and a preparation method and application thereof. Background Art

[0002] Wear-resistant composite materials composed of polymer materials and graphite are widely used in the manufacture of air compressors, gasoline engine vacuum pump vanes (scrapers), seals or gaskets. Foreign wear-resistant products are represented by German SGL graphite, BECKER and Roland / Heidelberg, which are far better than domestic products in high temperature resistance (180℃) and wear resistance (speed higher than 1300RPM). The vacuum pump vanes produced less in China are mainly made of polymer bisphenol A epoxy resin graphite composite materials, linear phenolic resin (PF) graphite composite materials and polyphenylene sulfide (PPS) graphite composite materials. Their high temperature resistance and wear resistance are lower than those of foreign products, and it is difficult to meet the requirements of vacuum pump use.

[0003] Polyimide (PI for short) has the characteristics of strong corrosion resistance and good thermal stability, and has been widely used in the field of tribology. The wear resistance and abrasion resistance of polyimide can be further improved by composite modification with graphite. Huang Lijian (Journal of Materials Science and Engineering, Vol. 26, No. 2), Yang Tao (Industrial Technology, 2019.01) and others studied the effect of graphite filler on the performance of polyimide composites and confirmed that graphite can significantly improve the wear resistance of polyimide. Polyimide graphite composites may be used in vane vacuum pumps or sealing gaskets.

[0004] However, polyimide has a linear molecular structure. Due to the polar terminal carboxyl groups (or terminal anhydride groups) and terminal amino groups at both ends of the molecule, its compatibility with graphite is poor. During the plasticizing and pressing process, polyimide easily aggregates into micelles and cannot be evenly dispersed, affecting the overall high temperature resistance and wear resistance of the composite material, resulting in unstable structure and performance of the composite material. In addition, polyimide is further imidized under heating conditions, producing water, which easily causes bubbles to appear in the resin matrix. Therefore, the current polyimide-graphite composite material generally has the problems of poor compatibility between polyimide and graphite, bubbles in the composite material, unstable performance and structure, and cannot meet the application problems in vane vacuum pumps or sealing gaskets. Summary of the invention

[0005] In view of the defects of the prior art, the present invention provides a polyimide graphite composite material, which solves the problems of poor wear resistance and high temperature resistance of the prior composite materials.

[0006] The object of the present invention is also to provide a method for preparing the above-mentioned polyimide graphite composite material;

[0007] The present invention also aims to provide the use of the polyimide graphite composite material in a vane vacuum pump or a sealing gasket.

[0008] In order to achieve the above object, the technical solution of the present invention is implemented as follows: a polyimide graphite composite material, calculated by mass percentage, includes the following components:

[0009] Polyimide 80~95%,

[0010] Graphite 5-20%;

[0011] The polyimide is a polyimide-terminated polymer containing aromatic anhydride end-capping.

[0012] Preferably, the polyimide is at least one of the self-made PI-1, PI-3, and PI-S, wherein the PI-1 is a polymer of 4,4'-oxydiphthalic anhydride and 2,2'-bis[4-(4-aminophenoxy)phenyl]propane; the PI-3 is a polymer of 4,4'-oxydiphthalic anhydride and 4,4'-diaminodiphenyl ether; and the PI-S is a capped polymer of 3,3',4,4'-dibenzophenone tetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether.

[0013] Preferably, the graphite is at least one of high-purity graphite and static-pressure graphite.

[0014] Preferably, the size of the polyimide graphite composite material is 365×245×5.5 mm, and the density is 1.75-1.95 g / cm 3 , linear expansion coefficient ≤1.

[0015] The second technical solution of the present invention is achieved as follows: the preparation method of the above-mentioned polyimide graphite composite material comprises the following steps:

[0016] S1, mixing polyimide and graphite in a mixer at a weight ratio of (80-95):(5-20) to obtain a premix;

[0017] S2, adding the premix obtained in S1 into a mold, hot pressing and then cooling under pressure to obtain a polyimide graphite composite material.

[0018] Preferably, in S1, the particle size of the polyimide is 800-1000 mesh; the particle size of the graphite is 800-1250 mesh.

[0019] Preferably, the rotation speed of the mixer is 15 rpm, and the mixing time is 2 to 4 hours.

[0020] Preferably, the specific method in S2 is:

[0021] S2-1. Take a certain amount of premix and fill it into the mold. Then put the mold with the material into the hot press. After the hot press is heated to 350°C, adjust the pressure of the hot press to 100KN and keep it warm and pressurized for 40 to 45 minutes.

[0022] S2-2, after the mold is heat-insulated and pressure-pressed, the mold is placed in a cold press, the pressure of the cold press is set to 1500KN and pressing is started. After pressing for 5 to 7 minutes, the pressure of the cold press is kept unchanged, and the mold is cooled by air cooling. When the temperature drops to below 200°C, the cold press is depressurized and the mold is taken out;

[0023] S2-3. When the mold is placed at room temperature and naturally cooled to below 50° C., the mold is disassembled to obtain a polyimide graphite composite material.

[0024] The third technical solution of the present invention is achieved by using the polyimide graphite composite material in a vane vacuum pump or a sealing gasket.

[0025] The principle of the present invention is described as follows:

[0026] The polyimide used in the present invention is a self-made polyimide-terminated polymer, which has good compatibility with graphite. The hot-pressed plate does not bend or warp, and the test indicators of self-lubricity, wear resistance and high temperature resistance are qualified. The customer trial effect is ideal and it has been put into mass production.

[0027] The key technology is to use phthalic acid groups to end-cap the amino groups of polyimide, which reduces the polarity of the polyimide end groups, improves the compatibility with graphite, and reduces the agglomeration of polyimide during the plasticization process; in addition, after the amino groups are end-capped, the water produced by further condensation of polyimide during the thermoplastic process is greatly reduced, the bubbles in the sheet are reduced, and the overall strength, heat resistance and wear resistance of the composite material are improved.

[0028] One of the general structural formulas of the polyimide-terminated polymer containing aromatic anhydride end-capping of the present invention is as follows:

[0029]

[0030] Linear polyimide has excellent thermal stability, good mechanical properties, outstanding radiation resistance and solvent resistance, and also has excellent wear resistance. During dry friction, a transfer film is formed with its opposite surface, which plays a self-lubricating role. However, the polyimide resin itself has a high friction coefficient and generates a large shear force, which causes greater adhesive wear; graphite has the function of a dry friction lubricant due to its unique lamellar crystal structure, and is usually used as a solid lubricant filler for polyimide self-lubricating composite materials. After graphite is added to the resin, the friction properties of the resin are improved. Graphite has a tendency to enrich on the friction opposite surface and form a transfer film, which may cause the friction surface of the sample to be not smooth enough when the graphite content is low, but when the graphite content is high, graphite can form a complete transfer film on the opposite surface and the sample surface, so the friction surface of the sample containing 15% graphite is very smooth.

[0031] The beneficial effects of the present invention are as follows: the present invention reduces the polarity of the terminal amino group by using anhydride containing an aromatic group for end-capping, the aromatic group (benzene) is similar to the graphite structure, and the compatibility of the polyimide and the graphite is improved; in addition, since the terminal amino group of the polyimide is capped, further imidization reaction of the polyimide is prevented, the generation of condensation water is greatly reduced, the generation of bubbles in the plasticizing process is effectively controlled, and the quality and use performance of the composite material are improved; in addition, the compatibility of the solid lubricant graphite with the polyimide is improved, the continuous phase of the material is evenly distributed, and the wear resistance and high temperature resistance are improved.

[0032] The preparation method of the present invention improves the wear resistance and self-lubricating properties of the polyimide and graphite composite material by adding graphite to the polyimide matrix and performing hot pressing and cold pressing and holding pressure processes, and the mechanical strength of the vacuum pump vane or sealing gasket pressed can meet the use requirements; in addition, by using dry powder to press into a rotary vane, the processing technology is simple, the raw materials are easy to purchase, there is no volatile organic compound (VOCs) emission, it is clean and environmentally friendly, and it is convenient for large-scale production. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] The present invention provides a polyimide graphite composite material, characterized in that it comprises the following components by mass percentage:

[0035] Polyimide 80~95%,

[0036] Graphite 5-20%;

[0037] The polyimide is a polyimide-terminated polymer containing aromatic anhydride end-capping.

[0038] The polyimide is at least one of the self-made PI-1, PI-3 and PI-S, with a fineness of 800-1000 meshes, wherein the PI-1 is a polymer of 4,4'-oxydiphthalic anhydride and 2,2'-bis[4-(4-aminophenoxy)phenyl]propane; the PI-3 is a polymer of 4,4'-oxydiphthalic anhydride and 4,4'-diaminodiphenyl ether; and the PI-S is a capped polymer of 3,3',4,4'-dibenzophenone tetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether.

[0039] The graphite is at least one of high-purity graphite and static-pressure graphite.

[0040] The present invention also provides a method for preparing a polyimide graphite composite material, which comprises the following steps in sequence:

[0041] S1, mixing polyimide and graphite in a weight ratio of (80-95): (5-20) in a V-type mixer at a speed of 15 rpm for 2-4 hours to obtain a premix;

[0042] The particle size of the polyimide is 800-1000 meshes, and it is pre-treated by drying in an oven at 240-260° C. for 5-8 hours before use; the particle size of the graphite is 800-1250 meshes.

[0043] S2, adding the premix obtained in S1 into a mold, hot pressing and then cooling under pressure to obtain a polyimide graphite composite material. Specifically comprising the following steps:

[0044] S2-1, take a certain amount of the premix obtained in S1 and fill it into the mold, then put the mold with the material into the hot press, heat the hot press to 350°C, adjust the pressure of the hot press to 100KN, and keep the temperature and pressure for 40 to 45 minutes;

[0045] S2-2, after the mold is heat-insulated and pressure-pressed, the mold is placed in a cold press, the pressure of the cold press is set to 1500KN and pressing is started. After pressing for 5 to 7 minutes, the pressure of the cold press is kept unchanged, and the mold is cooled by air cooling. When the temperature drops to below 200°C, the cold press is depressurized and the mold is taken out;

[0046] S2-3. When the mold is placed at room temperature and naturally cooled to below 50° C., the mold is disassembled to obtain a polyimide graphite composite material.

[0047] The invention also applies the prepared polyimide graphite composite material to a sliding vane vacuum pump or a sealing gasket.

[0048] Test method:

[0049] 1. Density: GB / T 1033.1-2008 (immersion method);

[0050] 2. Flexural strength and flexural modulus: GB / T 9341-2008 Determination of flexural properties of plastics;

[0051] 3. Compressive strength: GB 8624-2006;

[0052] 4. GB / T 531.1-2008 Test method for indentation hardness of vulcanized rubber or thermoplastic rubber Part 1: Shore hardness tester method (Shore hardness);

[0053] 5. Load thermal deformation temperature: GB / T 1634.2-2004;

[0054] 6. Linear expansion coefficient: GB 1036-89, determination method of linear expansion coefficient of plastics.

[0055] Table 1 Vacuum pump vane detection indicators

[0056] Test items Control indicators <![CDATA[Density (g / cm 3 )]]> 1.75-1.95 Bending strength (MPa) (23±2℃) ≥60 Flexural modulus (MPa) (23℃±2℃) ≥16000 Compressive strength (MPa) (23±2℃) ≥80 Shore Hardness ≥65 <![CDATA[Heat distortion temperature under load (18.6 kg / cm 2 ) °C]]> ≥270 <![CDATA[Coefficient of linear expansion (23 to 200 °C), (10 -5 cm / cm / °C)]]> ≤1

[0057] The following are specific embodiments

[0058] Example 1

[0059] A polyimide-graphite composite material provided in Example 1 of the present invention comprises the following components by mass percentage: 95% polyimide and 5% graphite; the polyimide is PI-S.

[0060] The method for preparing the polyimide graphite composite material provided in Example 1 of the present invention comprises the following steps in sequence:

[0061] S1, mixing polyimide with a particle size of 800-1000 mesh and pretreated by drying in an oven at 240° C. for 5 h and high-purity graphite with a particle size of 800-1250 mesh in a V-type mixer at a weight ratio of 95:5, with a rotation speed of 15 rpm and a mixing time of 2 h to obtain a premix;

[0062] S2, adding the premix obtained in S1 into a mold, hot pressing and then cooling under pressure to obtain a polyimide graphite composite material. Specifically comprising the following steps:

[0063] S2-1, take a certain amount of the premix obtained in S1 and fill it into the mold, then put the mold with the material into the hot press, heat the hot press to 350°C, adjust the hot press pressure to 100KN, and keep the temperature and pressure for 40 minutes;

[0064] S2-2, after the mold is heat-insulated and pressure-pressed, the mold is placed in a cold press, the pressure of the cold press is set to 1500KN and pressing begins. After pressing for 5 minutes, the pressure of the cold press is kept unchanged, and the mold is cooled by air cooling. When the temperature drops to below 200°C, the cold press is depressurized and the mold is taken out;

[0065] S2-3. When the mold is placed at room temperature and naturally cooled to below 50° C., the mold is disassembled to obtain a finished polyimide graphite composite material slide.

[0066] Example 2

[0067] Embodiment 2 of the present invention provides a polyimide-graphite composite material, which comprises the following components by mass percentage: 90% polyimide and 10% graphite; the polyimide is PI-S.

[0068] The method for preparing the polyimide graphite composite material provided in Example 2 of the present invention comprises the following steps in sequence:

[0069] S1, mixing polyimide with a particle size of 800-1000 mesh and pretreated by drying in an oven at 260° C. for 8 h and high-purity graphite with a particle size of 800-1250 mesh in a V-type mixer at a weight ratio of 90:10, with a rotation speed of 15 rpm and a mixing time of 4 h to obtain a premix;

[0070] S2, adding the premix obtained in S1 into a mold, hot pressing and then cooling under pressure to obtain a polyimide graphite composite material. Specifically comprising the following steps:

[0071] S2-1, take a certain amount of the premix obtained in S1 and fill it into the mold, then put the mold with the material into the hot press, heat the hot press to 350°C, adjust the pressure of the hot press to 100KN, and keep the temperature and pressure for 45 minutes;

[0072] S2-2, after the mold is heat-insulated and pressure-pressed, the mold is placed in a cold press, the pressure of the cold press is set to 1500KN and pressing begins. After pressing for 7 minutes, the pressure of the cold press is kept unchanged, and the mold is cooled by air cooling. When the temperature drops to below 200°C, the cold press is depressurized and the mold is taken out;

[0073] S2-3. When the mold is placed at room temperature and naturally cooled to below 50° C., the mold is disassembled to obtain a finished polyimide graphite composite material slide.

[0074] Example 3

[0075] A polyimide-graphite composite material provided in Example 3 of the present invention comprises the following components by mass percentage: 85% polyimide and 15% graphite; the polyimide is PI-S.

[0076] The method for preparing the polyimide graphite composite material provided in Example 3 of the present invention comprises the following steps in sequence:

[0077] S1, mixing polyimide and graphite in a weight ratio of 85:15 in a V-type mixer, rotating speed 15 rpm, mixing time 3 h, to obtain a premix;

[0078] S2, adding the premix obtained in S1 into a mold, hot pressing and then cooling under pressure to obtain a polyimide graphite composite material. Specifically comprising the following steps:

[0079] S2-1, take a certain amount of the premix obtained in S1 and fill it into the mold, then put the mold with the material into the hot press, heat the hot press to 350°C, adjust the pressure of the hot press to 100KN, and keep the temperature and pressure for 42 minutes;

[0080] S2-2, after the mold is heat-insulated and pressure-pressed, the mold is placed in a cold press, the pressure of the cold press is set to 1500KN and pressing begins. After pressing for 6 minutes, the pressure of the cold press is kept unchanged, and the mold is cooled by air cooling. When the temperature drops to below 200°C, the cold press is depressurized and the mold is taken out;

[0081] S2-3. When the mold is placed at room temperature and naturally cooled to below 50° C., the mold is disassembled to obtain a finished polyimide graphite composite material slide.

[0082] Example 4

[0083] A polyimide-graphite composite material provided in Example 4 of the present invention comprises the following components by mass percentage: 80% polyimide and 20% graphite; the polyimide is PI-S.

[0084] The method for preparing the polyimide graphite composite material provided in Example 4 of the present invention comprises the following steps in sequence:

[0085] S1, mixing polyimide and graphite in a weight ratio of 80:20 in a V-type mixer at a speed of 15 rpm for 3 h to obtain a premix;

[0086] S2. Same as Example 3.

[0087] Example 5

[0088] Example 5 of the present invention provides a polyimide-graphite composite material, wherein the polyimide is PI-1, the graphite is statically pressed graphite, and the rest is the same as Example 1.

[0089] Example 6

[0090] Example 6 of the present invention provides a polyimide-graphite composite material, wherein the polyimide is PI-3, the graphite is statically pressed graphite, and the rest is the same as Example 2.

[0091] Example 7

[0092] Example 7 of the present invention provides a polyimide graphite composite material, wherein the polyimide is a mixture of PI-1, PI-3, and PI-S, and the high-purity graphite is a mixture of static pressed graphite, and the rest is the same as Example 1.

[0093] Example 8

[0094] Example 8 of the present invention provides a polyimide graphite composite material, wherein the polyimide is a mixture of PI-1, PI-3, and PI-S, and the high-purity graphite is a mixture of static pressed graphite, and the rest is the same as Example 2.

[0095] Table 2 Test data of Examples 1-4

[0096]

[0097]

[0098] The following is a comparative example

[0099] The polymer matrix used in the domestic vacuum pump vanes is usually PPS (polyphenylene sulfide) and PF (phenolic resin). After research and optimization, the following comparative example was obtained. The data was compared with that of German SGL EK60.

[0100] Comparative Example 1

[0101] The polymer resin and graphite composite plate material provided in this comparative example 1 comprises the following components by mass percentage: 30% polyphenylene sulfide PPS and 70% graphite;

[0102] A polymer resin and graphite composite plate material comprises the following steps in sequence:

[0103] S1, polyphenylene sulfide PPS and graphite are mixed in a V-type mixer at a weight ratio of 30:70, with a rotation speed of 15 rpm and a mixing time of 2 h to obtain a premix;

[0104] S2. Same as Example 1.

[0105] Comparative Example 2

[0106] The comparative example 2 provides a polymer resin and graphite composite plate material, and its raw material composition and weight ratio are as follows: the weight ratio of phenolic resin PF is 28 parts, and the weight ratio of graphite is 72 parts.

[0107] The preparation method is the same as that in Example 2.

[0108] A polymer resin and graphite composite plate material, comprising the following components by mass percentage: phenolic resin PF28%, graphite 72%;

[0109] A method for preparing a polymer resin and graphite composite plate material comprises the following steps in sequence:

[0110] S1, phenolic resin PF and graphite are mixed in a V-type mixer in a weight ratio of 28:72, with a rotation speed of 15 rpm and a mixing time of 4 h to obtain a premix;

[0111] S2. Same as Example 1.

[0112] Comparative Example 3

[0113] Comparative Example 3 provides a polymer resin and graphite composite plate material, using the EK60 dry vacuum pump vane produced by SGL of Germany, and makes a comparison with Example 3 for testing.

[0114] Table 3 Comparative Example 1-2 Installation and Operation

[0115]

[0116] Table 4 Comparative Examples 2 and 3 and German Technical Indicators

[0117]

[0118] In Examples 1-4, as the amount of graphite filler increases, the mechanical properties of the composite material gradually decrease. Because graphite, as a self-lubricating filler, has no toughening and strengthening effect on the composite material. Due to the low inherent strength of graphite, the interface strength between the graphite particles and the polyimide matrix is ​​not high, and the bonding force (compatibility) is poor, resulting in reduced mechanical properties of the composite material. After the polyimide is capped, its compatibility with graphite is improved, and its mechanical properties, heat resistance and wear resistance are all improved. The performance of Example 3 is relatively good.

[0119] In Comparative Examples 1-2, the composite material sheet of polyphenylene sulfide PPS and graphite in Comparative Example 1 is prone to bending or warping and has poor lubrication. The composite material sheet of phenolic resin PF and graphite in Comparative Example 2 is better than Comparative Example 1, but the operating conditions do not meet the use requirements.

[0120] Comparative Example 3 is a composite vane EK60 made of resin and graphite produced by SGL in Germany. Its overall performance, especially wear resistance, is better than that of Example 3, but the thermal deformation temperature and linear expansion coefficient performance indicators of Examples 1-4 are better than those of SGL vane EK60. Therefore, the composite material composed of polyimide and graphite has its specific lubrication performance, can meet the performance requirements of high-performance vacuum pump vanes, and has good product space and market prospects.

[0121] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A polyimide graphite composite material, characterized in that: Calculated by mass percentage, it includes the following components: Polyimide 80~95%, Graphite 5-20%; The polyimide is a polyimide-terminated polymer containing aromatic anhydride end-capping.

2. A polyimide graphite composite material according to claim 1, characterized in that: The polyimide is at least one of the self-made PI-1, PI-3 and PI-S, wherein the PI-1 is a polymer of 4,4'-oxydiphthalic anhydride and 2,2'-bis[4-(4-aminophenoxy)phenyl]propane; the PI-3 is a polymer of 4,4'-oxydiphthalic anhydride and 4,4'-diaminodiphenyl ether; and the PI-S is a capped polymer of 3,3',4,4'-dibenzophenone tetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether.

3. The polyimide graphite composite material according to claim 1, characterized in that: The graphite is at least one of high-purity graphite and static-pressure graphite.

4. The polyimide graphite composite material according to claim 1, characterized in that: The size of the polyimide graphite composite material is 365×245×5.5 mm, and the density is 1.75-1.95 g / cm 3 , linear expansion coefficient ≤1.

5. A method for preparing the polyimide graphite composite material according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, mixing polyimide and graphite in a mixer at a weight ratio of (80-95):(5-20) to obtain a premix; S2, adding the premix obtained in S1 into a mold, hot pressing and then cooling under pressure to obtain a polyimide graphite composite material.

6. The method for preparing a polyimide graphite composite material according to claim 5, characterized in that: In S1, the particle size of the polyimide is 800-1000 mesh; the particle size of the graphite is 800-1250 mesh.

7. The method for preparing a polyimide graphite composite material according to claim 5, characterized in that: In S1, the rotation speed of the mixer is 15 rpm, and the mixing time is 2 to 4 hours.

8. The method for preparing a polyimide graphite composite material according to claim 5, characterized in that: The specific method in S2 is: S2-1. Take a certain amount of premix and fill it into the mold. Then put the mold with the material into the hot press. After the hot press is heated to 350°C, adjust the pressure of the hot press to 100KN and keep it warm and pressurized for 40 to 45 minutes. S2-2, after the mold is heat-insulated and pressure-pressed, the mold is placed in a cold press, the pressure of the cold press is set to 1500KN and pressing is started. After pressing for 5 to 7 minutes, the pressure of the cold press is kept unchanged, and the mold is cooled by air cooling. When the temperature drops to below 200°C, the cold press is depressurized and the mold is taken out; S2-3. When the mold is placed at room temperature and naturally cooled to below 50° C., the mold is disassembled to obtain a polyimide graphite composite material.

9. Use of the polyimide graphite composite material according to any one of claims 1 to 4 in a vane vacuum pump or a sealing gasket.

Images