A high-temperature resistant polyimide foam material and its preparation method

Abstract

This invention discloses a method for preparing high-temperature resistant polyimide foam material, comprising: preparing a foamable precursor powder using aromatic dianhydride and diamine; performing bilayer extrusion and foaming molding using two single-screw extruders, wherein one extruder extrudes and foams the foamable precursor powder, and the other extrudes fiber-reinforced thermoplastic resin; the two are compounded at a co-extrusion die, and shaped by a shaping die to obtain a polyimide foam composite material with a fiber-reinforced resin layer on the surface; cutting and collecting polyimide foam strips or foam particles of equal length, filling them into a die, and then hot-pressing to obtain the polyimide foam composite material. This invention significantly improves the operability of polyimide foam preparation and simplifies subsequent molding processes. This invention also provides a high-temperature resistant polyimide foam material obtained by the above preparation method, which can simultaneously provide high compressive strength, high modulus, and low density, and is easy to scale up for production.

Description

Technical Field

[0001] This invention relates to a polyimide foam and its preparation method, belonging to the field of polymer materials technology. Background Technology

[0002] Rigid polymer foam is a widely used material. Existing widely used polymer foam materials mainly include PVC and PET, which have been applied in the fields of wind turbine blades and aerospace sandwich materials. Side-chain polyimide (PMI) foam has also been applied and promoted in industries such as weaponry, medical care, and sports. However, with the further upgrading of equipment, the requirements for the temperature resistance of materials are getting higher and higher. Some equipment requires materials to withstand temperatures above 200°C. Traditional rigid foam materials are also facing the challenge of not being able to meet the higher requirements.

[0003] Main-chain polyimide foam (MIM) is a material with good temperature resistance, capable of withstanding temperatures up to 200℃ and above, with some types reaching over 250℃. There are various methods for preparing rigid polyimide foam, a common approach using aromatic dianhydrides and aromatic diamines as the main raw materials. However, the compressive strength of main-chain polyimide foam prepared using this system is currently lower than that of PMI foam of the same density. This means that to achieve the same compressive strength, the density of main-chain polyimide foam must be 80%-100% higher than that of PMI foam, thus limiting its application in aerospace and other fields with high weight reduction requirements. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned defects and provide a high-temperature resistant polyimide foam material and its preparation method. This invention solves the technical problem that traditional main-chain polyimide foam materials cannot simultaneously achieve high compressive strength and low density. The foam material of this invention can simultaneously provide high compressive strength, high modulus and low density.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention discloses a method for preparing high-temperature resistant polyimide foam material, comprising: preparing foamable precursor powder using aromatic dianhydride and diamine; performing bilayer extrusion and foaming molding using two single-screw extruders, wherein one extruder extrudes and foams the foamable precursor powder, and the other extrudes fiber-reinforced thermoplastic resin, the two are compounded at the co-extrusion die, and shaped by a shaping mold to obtain a polyimide foam composite material with a fiber-reinforced resin layer on the surface; cutting and collecting polyimide foam strips or foam particles of equal length, filling them into a mold, heating the core and the outside temperature to be the same, and then hot pressing to obtain a high-performance polyimide foam composite material.

[0007] This invention discloses a method for preparing a high-temperature resistant polyimide foam material, which specifically includes the following steps:

[0008] (1) Using aromatic dianhydrides and diamines, foamable precursor powders were prepared;

[0009] (2) Using foamable precursor powder, polyimide foam strips with a surface coated with fiber-reinforced resin layer are prepared by double-layer co-extrusion and extrusion foaming methods.

[0010] The method of double-layer co-extrusion and extrusion foaming is as follows:

[0011] Using a single-screw extruder, foamable precursor powder or a powder mixture containing foamable precursor powder is extruded and foamed to obtain a foamed strip profile. At the same time, another single-screw extruder is used to extrude fiber-reinforced thermoplastic resin, so that the foamed strip profile and the fiber-reinforced thermoplastic resin are compounded at the co-extrusion die. After being shaped by a sizing die, a polyimide foamed strip with a fiber-reinforced resin layer on the surface is obtained.

[0012] (3) Cut the foam strip obtained in step (2) and fill it into the hot pressing mold, and perform hot pressing and curing to obtain high temperature resistant polyimide foam material.

[0013] Furthermore, the method of step (1) includes:

[0014] (1.1) Add aromatic dianhydride to a polar solvent, then add a capping agent and a fatty alcohol. After the reaction is complete, add a diamine and react at 50-70℃ for 0.5-3h to obtain solution A; the amount of fatty alcohol is 2-6 times the amount of aromatic dianhydride; the molar ratio of the anhydride groups in the aromatic dianhydride and the capping agent to the amino groups in the diamine is 1:1.1-1.

[0015] (1.2) Remove the solvent from solution A and pulverize the solid to obtain foamable precursor powder.

[0016] Furthermore, the aromatic dianhydride mentioned in step (1) includes one or a combination of several of the following: 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, bisphenol A type diphenyl ether dianhydride, or 2,3,3',4'-biphenyl tetracarboxylic dianhydride.

[0017] The diamine includes one or a combination of several of the following: 1,4-p-phenylenediamine, 1,3-m-phenylenediamine, 4,4-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-bis(3-aminophenoxy)benzophenone, 4,4'-bis(3-aminophenoxy)diphenyl sulfone, 1,3-bis(4'-aminophenoxy)benzene, or 2,2'-bis[4-(4-aminophenoxyphenyl)]propane.

[0018] Furthermore, the polar solvent mentioned in step (1) is one or a combination of several of tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide or N-methylpyrrolidone;

[0019] The fatty alcohols include methanol or ethanol;

[0020] The capping agent is 5-norbornene-2,3-dianhydride or a mixture of 5-norbornene-2,3-dianhydride and 4-phenylacetylene phthalic anhydride.

[0021] Furthermore, in step (2), the powder mixture is a mixture of the foamable precursor powder and thermoplastic polyimide powder prepared in step (1), and the mass ratio of the foamable precursor powder to the thermoplastic polyimide powder is 50:50 to 99:1.

[0022] Furthermore, in step (2), the fiber-reinforced thermoplastic resin is a composite of a meltable resin and reinforcing fibers;

[0023] The meltable resin includes one or a combination of several of polyphenylene sulfide (PPS), polyether ether ketone (PEEK), or thermoplastic polyimide resin (TPI).

[0024] The reinforcing fiber includes one or a combination of carbon fiber, glass fiber, or quartz fiber.

[0025] Furthermore, in step (2), the extrusion foaming temperature is 260–340°C; the extrusion temperature of the fiber-reinforced thermoplastic resin is 270–420°C.

[0026] Furthermore, in step (2), when the foamed strip profile and the fiber-reinforced thermoplastic resin are compounded at the co-extrusion die, the extrusion speed is 0.1 to 5 m / min; the thickness of the fiber-reinforced resin layer on the surface of the polyimide foamed strip is 0.01 to 0.5 mm; and the diameter of the polyimide foamed strip is 0.1 to 5 mm.

[0027] Furthermore, in step (3), the foam strips with a fiber-reinforced resin layer on the surface are cut into granules or strips, filled into a hot-pressing mold, and then hot-pressed and cured.

[0028] The curing temperature for hot pressing is 280℃~420℃.

[0029] A high-temperature resistant polyimide foam material is obtained by the above-mentioned preparation method for a high-temperature resistant polyimide foam material, wherein the density of the high-temperature resistant polyimide foam material is ≥100 kg·m³. -3 The compressive strength is greater than 2 MPa.

[0030] The method of this invention uses multi-layer co-extrusion technology for foaming and molding, which greatly improves the operability of polyimide foam preparation and simplifies subsequent molding processes. The prepared polyimide foam material has high compressive strength, is easy to mass-produce, and can simultaneously provide high compressive strength, high modulus, and low density.

[0031] Compared with the prior art, the present invention has at least one of the following advantages:

[0032] (1) This invention creatively proposes a composite material with fiber-reinforced adhesive / meltable resin covering the surface of a foamed strip, wherein the surface density of the foamed strip is greater than or equal to 1200 kg / m³. 3 Core density 50-600 kg / m³ 3 It features a dense surface layer and a low-density core, providing high compressive strength, high modulus, and low density simultaneously.

[0033] (2) This invention utilizes cut foam strips or foam strip particles to prepare different types of foam materials. Using particle hot pressing, irregular parts can be formed in one step, such as tubular, conical, and square frame composite foams; using long strip foam strips for hot pressing, high-strength foams along the stretching direction of the foam strips can be prepared.

[0034] (3) The method used in this invention can obtain resin particles that are not fully foamed and not fully cross-linked and cured during extrusion foaming. After coating with fiber-reinforced thermoplastic resin and hot pressing, it can further foam and achieve foaming and complete cross-linking and curing of resin particles / fiber strips.

[0035] (4) The present invention adopts a double-layer co-extrusion and extrusion foaming method. The extrusion foaming method simultaneously realizes the extrusion of foaming material and the coating of surface fiber-reinforced resin layer. The process is simple and conducive to continuous and automated production.

[0036] (5) The present invention provides an extrusion foaming molding temperature of 260-340℃, a fiber-reinforced resin extrusion temperature of 270-420℃, and an extrusion speed of 0.1-5m / min, so that a layer of fiber-reinforced resin is coated on the surface of the foam strip, the thickness of the resin coating is 0.01-0.5mm, and the diameter of the foam strip is preferably 0.1-5mm, which can ensure the uniformity of the resin layer coating and maximize the mechanical properties of the material.

[0037] (6) The present invention prepares polyimide foam by hot pressing after covering the surface of the foam strip with a viscous / fusible resin fiber composite material. The prepared foam material has outstanding mechanical properties. Compared with the foam material of the same density prepared by the current conventional preparation method, the compressive strength is more than 50% higher than that of the traditional main chain polyimide foam material, which is close to the compressive strength of the PMI foam material currently on the market, thus improving the adaptability of this type of foam under high compressive strength.

[0038] (7) The foam material of the present invention can be used at temperatures above 200°C, which broadens the application temperature range of the foam material and can meet the requirements of the corresponding equipment for the use temperature of the sandwich foam material. It can replace foam materials such as PMI in high-temperature scenarios. Detailed Implementation

[0039] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0040] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0041] This invention provides a method for preparing high-temperature resistant polyimide foam, which uses a quasi-double-layer extrusion foaming method. First, a foaming strip profile is prepared using an extruder head, and fiber-reinforced thermoplastic resin is extruded using another extruder. The two are compounded and extruded at a co-extrusion die head, and then shaped by a shaping die to obtain a polyimide foam composite material with a fiber-reinforced resin layer on the surface. Through hot pressing, a foam composite material with high compressive strength is obtained, thus completing this invention.

[0042] In one specific embodiment, the method for preparing high-temperature resistant polyimide foam includes the following steps:

[0043] Step (1): Prepare foamable RTM process resin powder. Add aromatic dianhydride to a polar solvent, then add 2 to 6 times the molar amount of small molecule fatty alcohol, capping agent and solvent. After the reaction is complete, add a measured amount of diamine. After reacting for 0.5 to 3 hours, obtain solution A. Dry solution A to remove the solvent, then pulverize to obtain foamable precursor powder.

[0044] Step (2), extrusion foaming. Using a single-screw extruder, the prepared powder or powder mixture is extruded, foamed and shaped. At the same time, another extruder is used to extrude fiber-reinforced thermoplastic resin. The two are compounded at the co-extrusion die and shaped by a sizing die to obtain a polyimide foam strip with a fiber-reinforced resin layer on the surface.

[0045] Step (3) involves cutting the foam strip extruded in step (2), filling it into a mold, and then hot-pressing and curing it to obtain a composite polyimide foam material.

[0046] In a preferred embodiment of the present invention, in step (1), the aromatic dianhydride includes one or a combination of several of the following: 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, bisphenol A type diphenyl ether dianhydride, or 2,3,3',4'-biphenyltetracarboxylic dianhydride; the diamine includes one or a combination of several of the following: 1,4-p-phenylenediamine, 1,3-m-phenylenediamine, 4,4-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-bis(3-aminophenoxy)benzophenone, 4,4'-bis(3-aminophenoxy)diphenyl sulfone, 1,3-bis(4'-aminophenoxy)benzene, 2,2'-bis[4-(4-aminophenoxyphenyl)]propane.

[0047] In a preferred embodiment of the present invention, the solvent in step (1) is one or a combination of several of tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; the fatty alcohol includes methanol or ethanol.

[0048] In a preferred embodiment of the present invention, the end-capping agent in step (1) is 5-norbornene-2,3-dianhydride or a mixture thereof with 4-phenylacetylene phthalic anhydride.

[0049] In a preferred embodiment of the present invention, in step (1), the molar ratio of fatty alcohol to aromatic dianhydride is 6:1 to 2:1, the molar ratio of acid anhydride group to amine group is 1:1.1 to 1, and the reaction temperature for adding the measured diamine is 50 to 70°C.

[0050] In a preferred embodiment of the present invention, in step (2), the powder mixture is a mixture of the powder in step (1) and thermoplastic polyimide powder, and the mass ratio of the two powders is 50:50 to 99:1.

[0051] In a preferred embodiment of the present invention, in step (2), the reinforcing resin is a composite of a fusible resin material and a reinforcing fiber; the fusible resin includes, but is not limited to, polyphenylene sulfide (PPS), polyether ether ketone (PEEK), and thermoplastic polyimide resin (TPI), and the reinforcing fiber includes, but is not limited to, one or more fibers such as carbon fiber, glass fiber, and quartz fiber.

[0052] In a preferred embodiment of the present invention, the reinforcing resin is extruded into the co-extrusion die after extrusion foaming molding, forming a fiber-reinforced resin layer on the surface of the foam strip, so that the surface of the foam strip is coated with a layer of fiber-reinforced resin, and the diameter of the foam strip can be adjusted according to the diameter of the molding cavity of the foaming mold.

[0053] In a preferred embodiment of the present invention, in step (2), the extrusion foaming temperature is 260-340°C; the fiber-reinforced resin extrusion temperature is 270-420°C; the co-extrusion process is that the foam strip and the fiber-reinforced resin are compoundly extruded through a co-extrusion die at an extrusion speed of 0.1-5 m / min, so that a layer of fiber-reinforced resin is coated on the surface of the foam strip, the thickness of the resin coating is 0.01-0.5 mm, and the diameter of the foam strip can be adjusted according to the diameter of the mold cavity, preferably 0.1-5 mm.

[0054] In step (3) of this invention, the extruded foam strip from step (2) is cut into granules or strips, then filled into a mold and hot-pressed to solidify, resulting in a composite polyimide foam material. The hot-pressing temperature is 280℃-420℃. This invention utilizes cut foam strips or foam strip granules to prepare different types of foam materials. Using granular hot pressing, one-step forming of irregularly shaped parts can be achieved, such as tubular, conical, and square frame-shaped composite foam forming; using long strip foam strips for hot pressing, high-strength foam can be prepared along the stretching direction of the foam strip.

[0055] The foam material prepared by the above method has a density ≥100 kg·m³. -3 The compressive strength is greater than 2 MPa.

[0056] Example:

[0057] (1) Foamable resin based on 2,3,3',4'-biphenyltetraic dianhydride

[0058] RTM1: In a three-necked flask equipped with a stirrer and a condenser, add 1400g of tetrahydrofuran and 570g of ethanol, then add 728g of 2,3,3',4'-biphenyltetracarboxylic dianhydride and 375g of 5-norbornene-2,3-dianhydride. Heat to 65℃ and continue the reaction for 3 hours. Then add 410g of 1,3-m-phenylenediamine, mix for 2 hours, remove the solvent, and then dry at 240℃. Finally, pulverize using a high-speed pulverizer and set aside for later use.

[0059] RTM2: In a three-necked flask equipped with a stirrer and a condenser, add 1000g of tetrahydrofuran and 340g of methanol, then add 880g of 2,3,3',4'-biphenyltetracarboxylic dianhydride and 830g of 5-norbornene-2,3-dianhydride. Heat to 65℃ and continue the reaction for 3 hours. Then add 490g of 1,3-m-phenylenediamine and 320g of 1,3-bis(4'-aminophenoxy)benzene. Mix for 2 hours and remove the solvent. Then dry at 240℃ and pulverize using a high-speed pulverizer for later use.

[0060] (2) Preparation of linear (thermoplastic) polyimide resin powder

[0061] In a three-necked flask equipped with a stirrer and a condenser, 6000 g of N,N-dimethylacetamide, 216 g of 1,3-m-phenylenediamine, and 146 g of 1,3-bis(4'-aminophenoxy)benzene were added. After complete dissolution, the mixture was cooled to 0°C, and then 735 g of 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride was added. The mixture was reacted at this temperature for 24 h. Then, 510 g of acetic anhydride and 510 g of triethylamine were added as chemical dehydrating agents, and the mixture was dehydrated at room temperature for 8 h. The mixture was then filtered, washed three times with ethanol, dried in an oven at 100°C, and then dried at 240°C for 4 h to obtain linear polyimide resin powder.

[0062] Example 1

[0063] Take 400g of RTM1 sample, add 60g of linear polyimide resin powder, mix evenly, and then extrude and foam using a small single-screw extruder at an extrusion temperature of 260-300℃. Simultaneously co-extrude PPS / carbon fiber composite material at an extrusion temperature of 280-320℃ (product of Shandong Sainji New Material Co., Ltd., model: PPS-SGC301STF), and cut it to obtain foamed particles with a diameter of about 3mm and a coating layer thickness of 0.20mm.

[0064] The co-extrusion process involves extrusion through a co-extrusion die, with the interface temperature at the foaming extruder being 320°C and the interface temperature at the coating and reinforcing resin extruder also being 320°C.

[0065] 200g of the above-mentioned foamed granules were filled into a sealed mold and hot-pressed for curing at 340℃ and 5MPa. The resulting foam had a density of 150kg / m³. 3 The compressive strength is 3.3 MPa, and the compressive strength at 200℃ is 2.7 MPa.

[0066] Example 2

[0067] Take 400g of RTM1 sample, add 40g of linear polyimide resin powder, mix evenly, and then extrude and foam using a small single-screw extruder at an extrusion temperature of 260-300℃. Simultaneously, co-extrude PPS / carbon fiber composite material at a temperature of 280-320℃ (product of Shandong Sainji New Material Co., Ltd., model: PPS-SGC301STF), and cut it to obtain foam strips with a diameter of about 3mm, a coating layer thickness of 0.2mm, and a length of about 10cm.

[0068] The co-extrusion process involves extrusion through a co-extrusion die, with the interface temperature at the foaming extruder being 320°C and the interface temperature at the coating and reinforcing resin extruder also being 320°C.

[0069] Arrange the foam strips neatly, take a 200g sample, fill it into a mold, and perform hot pressing and curing at 340℃ and 5MPa. Then cut and shape the foam, with the cutting direction perpendicular to the direction of the foam strips. The density of the resulting foam is 140kg / m³. 3 The compressive strength is 4.1 MPa, and the compressive strength at 200℃ is 3.41 MPa (the compression direction is the same as the direction of the foam strip arrangement).

[0070] Example 3

[0071] Take 300g of RTM1 sample, add 300g of linear polyimide resin powder, mix evenly, and then extrude and foam using a small single-screw extruder at an extrusion temperature of 260-300℃. Simultaneously co-extrude PEEK / carbon fiber composite material at an extrusion temperature of 360-420℃ (product of Shandong Sainji New Material Co., Ltd., model: PEEK-SGC301ATF), and cut it to obtain foamed particles with a diameter of about 3mm and a coating layer thickness of 0.30mm.

[0072] The co-extrusion process involves extrusion through a co-extrusion die, with the interface temperature at the foaming extruder being 320°C and the interface temperature at the coating and reinforcing resin extruder being 420°C.

[0073] 250g of the above-mentioned foamed granules were filled into a mold and then hot-pressed and cured at a temperature of 410℃ and a pressure of 5MPa. The resulting foam had a density of 210kg / m³. 3 The compressive strength is 5.1 MPa, and the compressive strength at 200℃ is 4.4 MPa.

[0074] Example 4

[0075] Take 300g of RTM2 sample, add 300g of linear polyimide resin powder, mix evenly, and then extrude and foam using a small single-screw extruder at an extrusion temperature of 260-300℃. Simultaneously co-extrude PEEK / carbon fiber composite material at an extrusion temperature of 360-420℃. (Product of Shandong Sainji New Material Co., Ltd., model: PEEK-SGC301ATF), and cut into foam strips with a diameter of approximately 3mm, a coating layer thickness of approximately 0.22mm, and a length of 10cm.

[0076] The co-extrusion process involves extrusion through a co-extrusion die, with the interface temperature at the foaming extruder being 320°C and the interface temperature at the coating and reinforcing resin extruder being 420°C.

[0077] 250g of the above-mentioned foam strip was filled into a mold and cured by hot pressing at a temperature of 410℃ and a pressure of 5MPa. The resulting foam had a density of 250kg / m³. 3 The compressive strength is 8.3 MPa, and the compressive strength at 200℃ is 7.1 MPa (the compression direction is the same as the direction of the foam strip arrangement).

[0078] Example 5

[0079] Take 400g of RTM2 sample, add 60g of linear polyimide resin powder, mix evenly, and then extrude and foam using a small single-screw extruder at an extrusion temperature of 260-300℃. At the same time, co-extrude PPS / carbon fiber composite material at an extrusion temperature of 280-320℃ (product of Shandong Sainji New Material Co., Ltd., model: PPS-SGC301STF), and cut it to obtain foamed particles with a diameter of about 3mm and a coating layer thickness of about 0.22mm.

[0080] The co-extrusion process involves extrusion through a co-extrusion die, with the interface temperature at the foaming extruder being 320°C and the interface temperature at the coating and reinforcing resin extruder also being 320°C.

[0081] 200g of the above-mentioned foamed granules were filled into a mold and then hot-pressed and cured at a temperature of 340℃ and a pressure of 3MPa. The resulting foam had a density of 150kg / m³. 3 The compressive strength is 3.5 MPa, and the compressive strength at 200℃ is 2.94 MPa.

[0082] Example 6

[0083] Take 400g of RTM2 sample, add 60g of linear polyimide resin powder, mix evenly, and then extrude and foam using a small single-screw extruder at an extrusion temperature of 260-300℃. At the same time, co-extrude PPS / carbon fiber composite material at an extrusion temperature of 280-300℃ (product of Shandong Sainji New Material Co., Ltd., model: PPS-SGC301STF), and cut it to obtain foam strips with a diameter of about 3mm, a coating layer thickness of about 0.22mm, and a length of about 10cm.

[0084] The co-extrusion process involves extrusion through a co-extrusion die, with the interface temperature at the foaming extruder being 300℃ and the interface temperature at the coating and reinforcing resin extruder being 300℃.

[0085] Arrange the foam strips neatly, take a 200g sample, fill it into a mold, and perform hot pressing and curing at 340℃ and 3MPa. Then cut and shape the foam, with the cutting direction perpendicular to the direction of the foam strips. The density of the resulting foam is 160kg / m³. 3 The compressive strength is 4.3 MPa, and the compressive strength at 200℃ is 3.6 MPa (the compression direction is the same as the direction of the foam strip arrangement).

[0086] Example 7

[0087] Take 400g of RTM2 sample, add 60g of linear polyimide resin powder, mix evenly, and then extrude and foam using a small single-screw extruder at an extrusion temperature of 260-300℃. Simultaneously co-extrude PPS / glass fiber composite material at an extrusion temperature of 280-300℃ (product of Shandong Sainji New Material Co., Ltd., model: PPS-SG401A87-01), and cut it into foam strips with a diameter of about 3mm, a coating layer thickness of about 0.21mm, and a length of about 10cm.

[0088] The co-extrusion process involves extrusion through a co-extrusion die, with the interface temperature at the foaming extruder being 300℃ and the interface temperature at the coating and reinforcing resin extruder being 300℃.

[0089] Arrange the foam strips neatly, take a 200g sample, fill it into a mold and cure it at 340℃ and 3MPa. Then cut and shape it, with the cutting direction perpendicular to the direction of the foam strips. The density of the resulting foam is 180kg / m³. 3 The compressive strength is 4.7 MPa, and the compressive strength at 200℃ is 3.9 MPa (the compression direction is the same as the direction of the foam strip arrangement).

[0090] Example 8

[0091] Take 400g of RTM2 sample, add 40g of linear polyimide resin powder, mix evenly, and then extrude using a small single-screw extruder at an extrusion temperature of 260-300℃. Simultaneously co-extrude PPS / glass fiber composite material at an extrusion temperature of 280-300℃ (product of Shandong Sainji New Material Co., Ltd., model: PPS-SG401A87-01), and cut it into foam strips with a diameter of about 3mm, a coating layer thickness of about 0.27mm, and a length of about 10cm.

[0092] The co-extrusion process involves extrusion through a co-extrusion die, with the interface temperature at the foaming extruder being 320℃ and the interface temperature at the coating and reinforcing resin extruder being 300℃.

[0093] Arrange the foam strips neatly, take a 200g sample, fill it into a mold and cure it. Curing temperature: 340℃, hot-press curing, pressure: 3MPa. Then cut and shape it, cutting direction perpendicular to the direction of the foam strips. The density of the resulting foam is 210kg / m³. 3 The compressive strength is 6.0 MPa, and the compressive strength at 200℃ is 5.1 MPa (the compression direction is the same as the direction of the foam strip arrangement).

[0094] Example 9

[0095] Take 300g of RTM2 sample, add 30g of linear polyimide resin powder, mix evenly, and then extrude using a small single-screw extruder at an extrusion temperature of 260-320℃. Simultaneously co-extrude PPS / glass fiber composite material at an extrusion temperature of 280-300℃ (product of Shandong Sainji New Material Co., Ltd., model: PPS-SG401A87-01), and cut it into foam strips with a diameter of about 5mm, a coating layer thickness of 0.38mm, and a length of about 10cm.

[0096] The co-extrusion process involves extrusion through a co-extrusion die, with the interface temperature at the foaming extruder being 320℃ and the interface temperature at the coating and reinforcing resin extruder being 300℃.

[0097] Arrange the foam strips neatly, take a 200g sample, fill it into a mold for further curing at 340℃ and 3MPa. Then cut and shape the foam, with the cutting direction perpendicular to the direction of the foam strips. The density of the resulting foam is 205kg / m³. 3 The compressive strength is 6.9 MPa, and the compressive strength at 200℃ is 6.0 MPa (the compression direction is the same as the direction of the foam strip arrangement).

[0098] Example 10

[0099] Take 300g of RTM2 sample and extrude it using a small single-screw extruder at an extrusion temperature of 260-320℃. Simultaneously, co-extrude PPS / glass fiber composite material at an extrusion temperature of 280-300℃ (product of Shandong Sainji New Material Co., Ltd., model: PPS-SG401A87-01). Cut the material into foam strips with a diameter of approximately 5mm, a coating layer thickness of 0.38mm, and a length of approximately 10cm.

[0100] The co-extrusion process involves extrusion through a co-extrusion die, with the interface temperature at the foaming extruder being 320℃ and the interface temperature at the coating and reinforcing resin extruder being 300℃.

[0101] Arrange the foam strips neatly, take a 200g sample, fill it into a mold for further curing at 340℃ and 3MPa. Then cut and shape the foam, with the cutting direction perpendicular to the direction of the foam strips. The resulting foam has a density of 200kg / m³. 3 The room temperature compressive strength is 3.8 MPa, and the 200℃ compressive strength is 3.23 MPa (the compression direction is the same as the direction of the foam strip arrangement).

[0102] The density of the foam material obtained in the above embodiments is 140 kg / m³. 3 ~250kg / m 3Between these values, the room temperature compressive strength is 3.3 MPa to 8.3 MPa, and the 200℃ compressive strength is 2.7 MPa to 7.1 MPa. The high-temperature compressive strength is far superior to that of PMI foam. In other words, the high-temperature mechanical strength of the foam obtained by this invention is significantly better than that of PMI.

[0103] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0104] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for preparing a high-temperature resistant polyimide foam material, characterized in that, include: (1) Using aromatic dianhydrides and diamines, foamable precursor powders are prepared; (2) Using foamable precursor powder, polyimide foam strips with a surface coated with fiber-reinforced resin layer were prepared by double-layer co-extrusion and extrusion foaming methods. The method of double-layer co-extrusion and extrusion foaming is as follows: A single-screw extruder is used to extrude and foam foamed precursor powder or powder mixture containing foamable precursor powder to obtain foamed strip profiles. At the same time, another single-screw extruder is used to extrude fiber-reinforced thermoplastic resin, so that the foamed strip profile and fiber-reinforced thermoplastic resin are compounded at the co-extrusion die. After being shaped by a shaping die, a polyimide foamed strip with a fiber-reinforced resin layer on the surface is obtained. (3) Cut the foam strip obtained in step (2) and fill it into a hot pressing mold, then hot press and solidify it to obtain high temperature resistant polyimide foam material; The density of high-temperature resistant polyimide foam material is ≥100 kg·m³. -3 The compressive strength is greater than 2 MPa; The method of step (1) includes: (1.1) Add aromatic dianhydride to a polar solvent, then add a capping agent and a fatty alcohol. After the reaction is complete, add a diamine and react at 50~70℃ for 0.5~3h to obtain solution A; the amount of fatty alcohol is 2~6 times the amount of aromatic dianhydride; the molar ratio of the anhydride groups in the aromatic dianhydride and the capping agent to the amino groups in the diamine is 1:1.1~1; (1.2) Remove the solvent from solution A and pulverize the solid to obtain foamable precursor powder; In step (3), the foam strips with a fiber-reinforced resin layer on the surface are cut into granules or strips, filled into a hot-pressing mold, and then hot-pressed and cured.

2. The method for preparing a high-temperature resistant polyimide foam material according to claim 1, characterized in that, The aromatic dianhydride mentioned in step (1) includes one or a combination of several of the following: 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, bisphenol A type diphenyl ether dianhydride, or 2,3,3',4'-biphenyl tetracarboxylic dianhydride. The diamine includes one or a combination of several of the following: 1,4-p-phenylenediamine, 1,3-m-phenylenediamine, 4,4-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-bis(3-aminophenoxy)benzophenone, 4,4'-bis(3-aminophenoxy)diphenyl sulfone, 1,3-bis(4'-aminophenoxy)benzene, or 2,2'-bis[4-(4-aminophenoxyphenyl)]propane.

3. The method for preparing a high-temperature resistant polyimide foam material according to claim 1, characterized in that, The polar solvent mentioned in step (1) is one or a combination of several of tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide or N-methylpyrrolidone; The fatty alcohols include methanol or ethanol; The capping agent is 5-norbornene-2,3-dianhydride or a mixture of 5-norbornene-2,3-dianhydride and 4-phenylacetylene phthalic anhydride.

4. The method for preparing a high-temperature resistant polyimide foam material according to claim 1, characterized in that, In step (2), the powder mixture is a mixture of foamable precursor powder and thermoplastic polyimide powder prepared in step (1), and the mass ratio of foamable precursor powder to thermoplastic polyimide powder is 50:50~99:

1.

5. The method for preparing a high-temperature resistant polyimide foam material according to claim 1, characterized in that, In step (2), the fiber-reinforced thermoplastic resin is a composite of a meltable resin and reinforcing fibers; The meltable resin includes one or a combination of several of polyphenylene sulfide (PPS), polyether ether ketone (PEEK), or thermoplastic polyimide resin (TPI). The reinforcing fiber includes one or a combination of carbon fiber, glass fiber, or quartz fiber.

6. The method for preparing a high-temperature resistant polyimide foam material according to claim 1, characterized in that, In step (2), the extrusion foaming temperature is 260~340℃; the extrusion temperature of fiber-reinforced thermoplastic resin is 270~420℃.

7. The method for preparing a high-temperature resistant polyimide foam material according to claim 1, characterized in that, In step (2), when the foamed strip profile and fiber-reinforced thermoplastic resin are compounded at the co-extrusion die, the extrusion speed is 0.1~5m / min; the thickness of the fiber-reinforced resin layer on the surface of the polyimide foamed strip is 0.01~0.5mm; and the diameter of the polyimide foamed strip is 0.1~5mm.

8. The method for preparing a high-temperature resistant polyimide foam material according to claim 1, characterized in that, The curing temperature for hot pressing is 280℃~420℃.

9. A high-temperature resistant polyimide foam material, characterized in that, The high-temperature resistant polyimide foam material is obtained by the preparation method according to any one of claims 1-8, wherein the density of the high-temperature resistant polyimide foam material is ≥100 kg·m³. -3 The compressive strength is greater than 2 MPa.