A PAEK composite material resistant to ultra-low temperatures and its preparation method

Abstract

This invention relates to the field of polyaryletherketone (PAEK) material modification technology, specifically to an ultra-low temperature resistant PAEK composite material and its preparation method, comprising the following materials: PAEK resin, polyethersulfone resin, aramid fibers with surface carboxylation pretreatment, sheet-like thermally conductive filler with a thermal conductivity of at least 400 W / m·K, and a coupling agent; this invention, through the synergistic blending modification of sheet-like thermally conductive filler with polyethersulfone (PES) microspheres and aramid fibers, achieves the advantages of high strength, high toughness, and low thermal stress in the composite material under extreme low temperature environments.

Description

Technical Field

[0001] This invention relates to the field of polyaryletherketone (PAEK) material modification technology, specifically to a low-temperature resistant PAEK composite material and its preparation method. Background Technology

[0002] Polyaryletherketones (PEEKs) are a class of crystalline polymers composed of phenylene rings linked by oxygen bridges (ether bonds) and carbonyl groups (ketones). Based on the different sequences and ratios of ether bonds, ketone groups, and benzene rings in the molecular chain, they are mainly classified into the following varieties: polyetheretherketone (PEEK), polyetherketone (PEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK), and polyetherketoneetherketoneketone (PEKEKK). The rigid benzene rings in the PEEK molecular structure give it excellent high-temperature performance, mechanical properties, electrical insulation, radiation resistance, and chemical corrosion resistance; while the ether bonds in its molecular structure provide flexibility. Among the PEEK series, the lower the ratio of ether bonds to ketone groups (E / K) in the molecular chain, the higher its melting point and glass transition temperature. Polyetheretherketone (PEEK), as a semi-crystalline special engineering plastic, is widely used in aerospace, medical devices, energy equipment, and other fields. With the rapid development of extreme low-temperature scenarios such as liquid hydrogen (-253℃) and liquid nitrogen (-196℃) (e.g., liquid oxygen / liquid hydrogen tanks for commercial rockets and cryogenic support systems for superconducting magnets), the limitations caused by the low-temperature brittleness of traditional PAEK materials are gradually being exposed.

[0003] Existing technologies often use fillers for modification, but there are significant drawbacks to improving the low-temperature performance of PAEK by adding fillers such as fibers or particles: glass fiber (GF) modification leads to low-temperature thermal stress concentration due to the large difference in the interfacial thermal expansion coefficients between GF and PEEK; carbon fiber (CF) modification can improve the modulus, but the high modulus results in low stress transfer efficiency at low temperatures, and the conductivity of CF is not suitable for insulation applications; the addition of traditional toughening agents (such as PTFE) leads to a decrease in the material's creep resistance, making it unable to meet long-term pressure requirements. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a PAEK composite material resistant to ultra-low temperatures and its preparation method. This invention utilizes phosphorus-doped hexagonal boron nitride (P-BN) in conjunction with the blending modification of polyethersulfone (PES) microspheres and aramid fibers. Under extreme low-temperature conditions, the composite material exhibits advantages such as high strength, high toughness, and low thermal stress.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A cryogenic PAEK composite material comprising the following 100% by weight of materials:

[0007] PAEK resin 60%-75%

[0008] Polyethersulfone resin 5%-10%,

[0009] 10%-20% of aramid fibers were pretreated with surface carboxylation.

[0010] 5%-10% of sheet-like thermally conductive fillers with a thermal conductivity of at least 400 W / m·K.

[0011] Coupling agent 0.5%-1%.

[0012] Furthermore, the sheet-like thermally conductive filler is selected from phosphorus-doped hexagonal boron nitride, with a phosphorus content of 3wt%-5wt%, a sheet thickness of 20-50nm, and an aspect ratio of at least 300. A phosphorus content <3wt% results in insufficient PN bond density and limited improvement in impact resistance; a phosphorus content >5wt% leads to excessive phosphorus damaging the layered structure of BN, decreasing thermal conductivity, and accelerating interface aging due to the oxidation of free phosphorus. A phosphorus content of 3wt%-5wt% represents the optimal window for low-temperature modification of PAEK, maximizing low-temperature toughening, enhanced thermal conductivity, and interface strengthening while ensuring the stability of the P-BN structure. Method for obtaining phosphorus-doped hexagonal boron nitride: Using boron phosphate (BPO4) as a solid-phase boron-phosphorus source, the temperature is raised to 1000-1100℃ under an inert gas protective atmosphere and the reaction is held for 0.5-2h. Then, a nitrogen source of ammonia (NH3) or nitrogen (N2) is introduced, and the reaction is continued at the holding temperature for 30-60 minutes. The product is taken out, ultrasonically treated in ethanol, filtered and dried to obtain phosphorus-doped hexagonal boron nitride with a sheet thickness of about 20-50nm and an aspect ratio of at least 300. The flow rate of the nitrogen source is 200-500sccm, and the flow rate of the inert gas protective atmosphere is 800-1000sccm.

[0013] Furthermore, the PAEK resin is selected from one or more resins selected from polyetheretherketone (PEEK), polyetherketone (PEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK), and polyetherketoneetherketoneketone (PEKEKK), with a resin particle size not exceeding 200 micrometers and a melt index of 10-50 g / 10 min under test conditions of 380°C and a load of 2.16 kg.

[0014] Furthermore, the particle size of the polyethersulfone resin does not exceed 50 micrometers; the length of the aramid fiber is 100-300 micrometers and the diameter is 10-15 micrometers; the coupling agent is selected from phosphate coupling agents.

[0015] Furthermore, the coupling agent is selected from one or more of the following: tetraisopropyl di(dioctylphosphoyloxy)titanate, a compound of di(2-ethylhexyl) phosphate and triethanolamine, a chelate of dioctyloxypyrophosphate titanate and triethanolamine, octadecyl phosphate, isopropyl tri(dioctylphosphoyloxy)titanate, isopropyl tri(dioctylphosphoyloxy)titanate, bis(dioctyloxypyrophosphate)ethylene titanate, 2-fluoro-1,3-dimethylimidazolium chloride hexafluorophosphate, and isopropylated triphenyl phosphate.

[0016] The preparation method of the above-mentioned ultra-low temperature resistant PAEK composite material includes the following steps:

[0017] S1. Prepare materials according to the formula; pretreat the sheet-like thermally conductive filler with a thermal conductivity of at least 400 W / m·K with polyethersulfone resin using a phosphate coupling agent to obtain the first material;

[0018] A second material is obtained by introducing carboxyl groups onto the surface of aramid fibers;

[0019] S2. PAEK resin, the first material, and the second material are melt-blended, extruded, and granulated to obtain a PAEK composite material resistant to ultra-low temperatures.

[0020] Further, the pretreatment step of S1 is as follows: the sheet-like thermally conductive filler and the polyethersulfone resin are dispersed in an alcohol solvent, ultrasonically dispersed, and then the phosphate coupling agent is added. The temperature is raised to 2-8°C below the boiling point of the alcohol solvent and ultrasonically dispersed for 1-5 hours. Then the mixture is dried, ground, and sieved.

[0021] Furthermore, the surface introduction method of S1 is as follows: first, the aramid fiber is dried to a moisture content of less than 0.1 wt%, and then treated with low-temperature oxygen plasma at a power of 60-100 W and an oxygen flow rate of 5-20 sccm for 4-10 minutes.

[0022] Furthermore, S2 employs a co-rotating twin-screw extruder for melt blending. The twin-screw extruder has a screw diameter of 35mm, a length-to-diameter ratio of 40:1, and a rotational speed of 250-350rpm. The temperature settings for each section of the twin-screw extruder are as follows: feeding section 340-350℃, melting section 370-380℃, mixing section 370-380℃, venting section 345-365℃, homogenizing section 355-365℃, and die head 340-355℃. The second material is added from the side feed port at a feeding rate of 3-6kg / h (to avoid fiber heat damage). The venting section has an exhaust port connected to a vacuum system, which removes volatile small molecules such as alcohol solvents from the melt through negative pressure. The vacuum negative pressure is -0.06MPa to -0.09MPa.

[0023] Beneficial technical effects:

[0024] This invention involves treating phosphorus-doped hexagonal boron nitride (P-BN) with polyethersulfone (PES) microspheres using a phosphate ester coupling agent, followed by melt blending modification with surface-carboxylated aramid fibers and PAEK matrix resin. The resulting composite material exhibits advantages such as high strength, high toughness, and low thermal stress under extreme low-temperature environments. This composite material is suitable for components in liquid hydrogen / liquid oxygen storage and transportation systems, such as sealing rings and valve components; for superconducting magnet support structures with low thermal expansion and high insulation; and for polar equipment, such as mechanical joints and sensor housings. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] Unless otherwise specifically stated, the numerical values ​​set forth in these embodiments do not limit the scope of the invention. Techniques and methods known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques and methods should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that values ​​expressed, for example, as "within the range of ab" or "between the range of ab," do not include the endpoint values ​​a and b; values ​​expressed as "for ab," "is ab," or "ab" include the endpoint values ​​a and b.

[0027] Furthermore, it should be noted that the use of terms such as "first" and "second" to define the materials is merely for the purpose of distinguishing the substances in each step. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0028] Experimental methods not specified in the following examples are generally performed according to national standards; if there is no corresponding national standard, they are performed according to general standard requirements or general methods.

[0029] Preparation Example 1

[0030] This case study focuses on the preparation of phosphorus-doped hexagonal boron nitride:

[0031] Take 200g of boron phosphate powder, place it in a crucible, and heat it to 1000℃ at a rate of 10℃ / min under an argon atmosphere of 1000 sccm. Then, anneal it at 1000℃ for 10 min, and then introduce ammonia gas at a rate of 500 sccm. Continue the reaction at 1000℃ for 30 min. After naturally cooling to room temperature, take out the product, sonicate it in ethanol, filter and dry it to obtain phosphorus-doped hexagonal boron nitride with a sheet thickness of 20-50 nm and an aspect ratio of at least 300, denoted as P-BN-Ⅰ.

[0032] Take 200g of boron phosphate powder, place it in a crucible, and heat it to 1100℃ at a rate of 10℃ / min under an argon atmosphere of 900 sccm. Then, anneal it at 1100℃ for 10 min, and then introduce ammonia gas at a rate of 300 sccm. Continue the reaction at 1100℃ for 60 min. After naturally cooling to room temperature, take out the product, sonicate it in ethanol, filter and dry it to obtain phosphorus-doped hexagonal boron nitride with a sheet thickness of 20-50 nm and an aspect ratio of at least 300, denoted as P-BN-II.

[0033] Take 200g of boron phosphate powder, place it in a crucible, and heat it to 1000℃ at a rate of 10℃ / min under an argon atmosphere of 800 sccm. Then, anneal it at 1000℃ for 10 min, and then introduce ammonia gas at a rate of 400 sccm. Continue the reaction at 1000℃ for 45 min. After naturally cooling to room temperature, take out the product, sonicate it in ethanol, filter and dry it to obtain phosphorus-doped hexagonal boron nitride with a sheet thickness of 20-50 nm and an aspect ratio of at least 300, denoted as P-BN-Ⅲ.

[0034] The phosphorus content of the above phosphorus-doped hexagonal boron nitride was tested to be approximately 3-5 wt%.

[0035] Example 1

[0036] A cryogenic PEEK composite material comprising the following 100% by weight of materials:

[0037] PEEK resin (Junhua, PEEK3600UF) with a melt index of 30 g / 10 min under test conditions of 100-200 micrometers particle size, 380℃, and 2.16 kg load was 64%.

[0038] 8% of polyethersulfone resin microspheres with a particle size of 10 micrometers (further ground using Solvay VW-10200RSFP)

[0039] 17% of aramid fibers (length 100-300 micrometers, diameter 10-15 micrometers) underwent surface carboxylation treatment.

[0040] 10% phosphorus-doped hexagonal boron nitride sheet filler (P-BN-Ⅰ)

[0041] 1% bis(dioctyloxypyrophosphate) ethylene titanate;

[0042] The preparation method of the above-mentioned ultra-low temperature resistant PEEK composite material includes the following steps:

[0043] S1. Prepare materials according to the formula;

[0044] Phosphorus-doped hexagonal boron nitride sheet filler and polyethersulfone resin microspheres were dispersed in anhydrous ethanol (solid-liquid ratio of 1g:10mL), and ultrasonically dispersed at 600W power and 40kHz frequency for 30min. Then, bis(dioctyloxypyrophosphate) ethylene titanate was added, the temperature was raised to 70℃ and ultrasonic dispersion was continued for 2h. After drying, grinding, and passing through a 300-mesh sieve, the pretreatment yielded the first material.

[0045] The aramid fiber was dried to a moisture content of less than 0.1 wt%, and then treated with low-temperature oxygen plasma at a power of 80 W and an oxygen flow rate of 10 sccm for 8 minutes (the aramid fiber was spread in the reaction chamber of the low-temperature oxygen plasma equipment with a stack thickness of ≤3 cm, and the amount of a single batch was not more than 15% of the effective volume of the reaction chamber). Carboxyl groups were introduced on the surface of the aramid fiber to obtain the second material.

[0046] S2. PEEK resin, the first material, and the second material are melt-blended and extruded using a co-rotating twin-screw extruder. The twin-screw extruder has a screw diameter of 35 mm, a length-to-diameter ratio of 40:1, and a rotation speed of 280 rpm. The temperature settings for each section of the twin-screw extruder are as follows: feeding section 340℃, melting section 370℃, mixing section 370℃, venting section 350℃, homogenizing section 365℃, and die head 340℃. The second material is added from the side feed port at a feeding speed of 5.0 kg / h. The venting section has an exhaust port connected to a vacuum system, which removes volatile small molecules such as alcohol solvents from the melt through negative pressure. The vacuum negative pressure is -0.09 MPa. After extrusion, the material is granulated to obtain a PEEK composite material resistant to ultra-low temperatures.

[0047] Example 2

[0048] A cryogenic PEEK composite material comprising the following 100% by weight of materials:

[0049] 70% of PEEK resin (Junhua, PEEK3600UF) with a melt index of 30 g / 10 min under test conditions of 100-200 micrometers particle size, 380℃, and 2.16 kg load.

[0050] 10% polyethersulfone resin microspheres with a particle size of 10 micrometers (further ground using Solvay VW-10200RSFP),

[0051] 12% of aramid fibers (length 100-300 micrometers, diameter 10-15 micrometers) underwent surface carboxylation treatment.

[0052] 7% phosphorus-doped hexagonal boron nitride sheet filler (P-BN-II)

[0053] 1% isopropyl tris(dioctylpyrophosphoryloxy)titanate;

[0054] The preparation method of the above-mentioned ultra-low temperature resistant PEEK composite material includes the following steps:

[0055] S1. Prepare materials according to the formula;

[0056] Phosphorus-doped hexagonal boron nitride sheet filler and polyethersulfone resin microspheres were dispersed in anhydrous ethanol (solid-liquid ratio of 1g:10mL), and ultrasonically dispersed at 600W power and 40kHz frequency for 30min. Isopropyl tris(dioctylpyrophosphoryloxy)titanate was added, the temperature was raised to 70℃ and ultrasonically dispersed for 2h. Then, the mixture was dried, ground, and passed through a 300-mesh sieve. The pretreatment yielded the first material.

[0057] The aramid fiber was dried to a moisture content of less than 0.1 wt%, and then treated with low-temperature oxygen plasma at a power of 80 W and an oxygen flow rate of 10 sccm for 8 minutes to introduce carboxyl groups on the surface of the aramid fiber to obtain the second material.

[0058] S2. PEEK resin, the first material, and the second material are melt-blended and extruded using a co-rotating twin-screw extruder. The twin-screw extruder has a screw diameter of 35 mm, a length-to-diameter ratio of 40:1, and a rotation speed of 300 rpm. The temperature settings for each section of the twin-screw extruder are as follows: feeding section 340℃, melting section 375℃, mixing section 375℃, venting section 355℃, homogenization section 365℃, and die head 345℃. The second material is added from the side feed port at a feeding speed of 4.5 kg / h. The venting section has an exhaust port connected to a vacuum system, which removes volatile small molecules such as alcohol solvents from the melt through negative pressure. The vacuum negative pressure is -0.09 MPa. After extrusion, the material is granulated to obtain a PEEK composite material resistant to ultra-low temperatures.

[0059] Example 3

[0060] A cryogenic PEEK composite material comprising the following 100% by weight of materials:

[0061] PEEK resin (Junhua, PEEK3600UF) with a melt index of 30 g / 10 min under test conditions of 100-200 micrometers particle size, 380℃, and 2.16 kg load was 68%.

[0062] 7% of polyethersulfone resin microspheres with a particle size of 10 micrometers (further ground using Solvay VW-10200RSFP)

[0063] 19% of aramid fibers (length 100-300 micrometers, diameter 10-15 micrometers) underwent surface carboxylation treatment.

[0064] Phosphorus-doped hexagonal boron nitride sheet filler (P-BN-Ⅲ) 5%,

[0065] 1% isopropyl tris(dioctylphosphoyloxy)titanate;

[0066] The preparation method of the above-mentioned ultra-low temperature resistant PEEK composite material includes the following steps:

[0067] S1. Prepare materials according to the formula;

[0068] Phosphorus-doped hexagonal boron nitride sheet filler and polyethersulfone resin microspheres were dispersed in anhydrous ethanol (solid-liquid ratio of 1g:10mL), and ultrasonically dispersed at 600W power and 40kHz frequency for 30min. Isopropyl tris(dioctylphosphoyloxy)titanate was added, the temperature was raised to 70℃ and ultrasonically dispersed for 3h. Then, the mixture was dried, ground, and passed through a 300-mesh sieve. The pretreatment yielded the first material.

[0069] The aramid fiber was dried to a moisture content of less than 0.1 wt%, and then treated with low-temperature oxygen plasma at a power of 80 W and an oxygen flow rate of 10 sccm for 8 minutes to introduce carboxyl groups on the surface of the aramid fiber to obtain the second material.

[0070] S2. PEEK resin, the first material, and the second material are melt-blended and extruded using a co-rotating twin-screw extruder. The twin-screw extruder has a screw diameter of 35 mm, a length-to-diameter ratio of 40:1, and a rotation speed of 320 rpm. The temperature settings for each section of the twin-screw extruder are as follows: feeding section 345℃, melting section 375℃, mixing section 380℃, venting section 360℃, homogenizing section 365℃, and die head 355℃. The second material is added from the side feed port at a feeding speed of 5.5 kg / h. The venting section has an exhaust port connected to a vacuum system, which removes volatile small molecules such as alcohol solvents from the melt through negative pressure. The vacuum negative pressure is -0.09 MPa. After extrusion, the material is granulated to obtain a PEEK composite material resistant to ultra-low temperatures.

[0071] Comparative Example 1

[0072] The formulation and preparation process of the composite material in this case are the same as those in Example 2. The difference is that the PEEK composite material includes the following 100% materials: 70% PEEK, 7% hexagonal boron nitride (layer thickness of 20-50nm, aspect ratio of at least 300, phosphorus-free), 8% polyethersulfone resin microspheres, 14% untreated aramid fiber, and 1% isopropyltrioleoyl oxytitanate; the remaining conditions are the same as in Example 2.

[0073] Comparative Example 2

[0074] The formulation and preparation process of the composite material in this case are the same as those in Example 2, except that untreated aramid fibers are used in the formulation; and no pretreatment is performed during the preparation process to obtain the first material.

[0075] Comparative Example 3

[0076] The formulation and preparation process of the composite material in this case are the same as in Example 2, except that the formulation is: 74% PEEK resin, 10% polyethersulfone resin microspheres, 15% surface carboxylated aramid fiber (treatment process is the same as the second material in Example 2), and 1% isopropyl tris(dioctyl pyrophosphate) titanate. The composite material preparation process is the same as S2 in Example 2. This case does not have thermally conductive fillers.

[0077] Comparative Example 4

[0078] The formulation and preparation process of the composite material in this case are the same as in Example 2, except that the formulation is: 75% PEEK resin, 10% polyethersulfone resin microspheres, 15% phosphorus-doped hexagonal boron nitride sheet filler, and 1% isopropyl tris(dioctyl pyrophosphoryloxy)titanate. The preparation process of the composite material is the same as the first material in S1 and S2 of Example 2. This case uses aramid fibers without surface carboxylation treatment.

[0079] Test case

[0080] The performance of the composite materials of the above embodiments and comparative examples was tested after sample preparation, and the results are shown in Table 1.

[0081] Table 1 Performance of each case

[0082]

[0083]

[0084] As shown in Table 1, the present invention, through the treatment of phosphorus-doped hexagonal boron nitride (P-BN) and polyethersulfone (PES) microspheres with a phosphate ester coupling agent, and then combining them with surface-carboxylated aramid fibers and a PEEK matrix resin, results in a composite material with good ultra-low temperature toughness. This is achieved by the cavitation of the PES microspheres to absorb impact energy, the bridging of the surface-carboxylated aramid fibers to inhibit crack propagation, and the uniform dispersion of the P-BN sheets to reduce stress concentration. The ultra-low temperature toughness is significantly improved: in a liquid nitrogen environment at -196℃, the notched impact strength of the material in Example 2 reaches 21.8 kJ / m. 2 (Comparative Example 1: 16.5 kJ / m) 2 (32% improvement); simultaneously, the composite material of the present invention can effectively reduce the thermal stress gradient in low-temperature environments, and the thermal conductivity of the material in Example 2 reaches 1.9 W / mK (the thermal conductivity of the scheme in Comparative Example 1 is 1.5 W / mK, an improvement of 27%); furthermore, it has low thermal expansion properties and high insulation properties (volume resistivity > 2.5 × 10⁻⁶). 15 The coefficient of thermal expansion of the composite material in Example 2 is 3.5 × 10⁻⁶ Ω·cm, within the range of -196 to 25°C. -5 / ℃ (compared to 4.1×10 in Comparative Example 1) -5 (C℃ decreases by 15%), which can be used to match metal parts (such as aluminum alloy shells of liquid hydrogen storage tanks).

[0085] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A PAEK composite material resistant to ultra-low temperatures, characterized in that, Includes the following materials by weight percentage: PAEK resin 60%-75%, Polyethersulfone resin 5%-10%, 10%-20% of aramid fibers were pretreated with surface carboxylation. 5%-10% of sheet-like thermally conductive fillers with a thermal conductivity of at least 400 W / m·K. The coupling agent is 0.5%-1%; the coupling agent is selected from phosphate ester coupling agents; The sheet-like thermally conductive filler is selected from phosphorus-doped hexagonal boron nitride, with a phosphorus content of 3wt%-5wt%, a sheet thickness of 20-50nm, and an aspect ratio of at least 300; The method for introducing carboxyl groups on the surface of aramid fibers is as follows: first, the aramid fibers are dried to a moisture content of less than 0.1 wt%, and then treated with low-temperature oxygen plasma at a power of 60-100 W and an oxygen flow rate of 5-20 sccm for 4-10 minutes.

2. The ultra-low temperature resistant PAEK composite material according to claim 1, characterized in that, The PAEK resin is selected from one or more resins selected from polyetheretherketone, polyetherketone, polyetherketoneketone, polyetheretherketoneketone, and polyetherketoneetherketoneketone. The particle size of the resin does not exceed 200 micrometers, and the melt index is 10-50 g / 10 min under the test conditions of 380°C and 2.16 kg load.

3. The ultra-low temperature resistant PAEK composite material according to claim 1, characterized in that, The polyethersulfone resin has a particle size of no more than 50 micrometers; the aramid fiber has a length of 100-300 micrometers and a diameter of 10-15 micrometers.

4. The ultra-low temperature resistant PAEK composite material according to claim 1, characterized in that, The coupling agent is selected from one or more of the following: tetraisopropyl di(dioctylphosphoyloxy)titanate, a compound of di(2-ethylhexyl) phosphate and triethanolamine, a chelate of dioctyloxypyrophosphate titanate and triethanolamine, octadecyl phosphate, isopropyl tri(dioctylphosphoyloxy)titanate, isopropyl tri(dioctylphosphoyloxy)titanate, bis(dioctyloxypyrophosphate)ethylene titanate, 2-fluoro-1,3-dimethylimidazolium chloride hexafluorophosphate, and isopropylated triphenyl phosphate.

5. A method for preparing a PAEK composite material resistant to ultra-low temperatures, characterized in that, The composite material applicable to any one of claims 1-4 comprises the following steps: S1. Prepare materials according to the formula; pretreat the sheet-like thermally conductive filler with a thermal conductivity of at least 400 W / m·K with polyethersulfone resin using a phosphate coupling agent to obtain the first material; A second material is obtained by introducing carboxyl groups onto the surface of aramid fibers; S2. PAEK resin, the first material, and the second material are melt-blended, extruded, and granulated to obtain a PAEK composite material resistant to ultra-low temperatures.

6. The method for preparing a PAEK composite material resistant to ultra-low temperatures according to claim 5, characterized in that, The pretreatment steps of S1 are as follows: the sheet-like thermally conductive filler and the polyethersulfone resin are dispersed in an alcohol solvent, ultrasonically dispersed, and then the phosphate coupling agent is added. The temperature is raised to 2-8°C below the boiling point of the alcohol solvent and ultrasonically dispersed for 1-5 hours. Then the mixture is dried, ground, and sieved.

7. The method for preparing a PAEK composite material resistant to ultra-low temperatures according to claim 5, characterized in that, The surface introduction method of S1 is as follows: first, the aramid fiber is dried to a moisture content of less than 0.1 wt%, and then treated with low-temperature oxygen plasma at a power of 60-100W and an oxygen flow rate of 5-20 sccm for 4-10 minutes.

8. The method for preparing a PAEK composite material resistant to ultra-low temperatures according to claim 5, characterized in that, S2 uses a co-rotating twin-screw extruder for melt blending. The twin-screw extruder has a screw diameter of 35mm, a length-to-diameter ratio of 40:1, and a rotational speed of 250-350rpm. The temperature settings for each section of the twin-screw extruder are as follows: feeding section 340-350℃, melting section 370-380℃, mixing section 370-380℃, venting section 345-365℃, homogenizing section 355-365℃, and die head 340-355℃. The second material is added from the side feed port at a feeding speed of 3-6kg / h. The venting section has an exhaust port connected to a vacuum system, which removes volatile substances from the melt through negative pressure. The vacuum negative pressure is -0.06MPa to -0.09MPa.

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