A pei or peek-based 3d-printed wave-absorbing material and a method of making the same

Abstract

The application discloses a kind of PEI or PEEK-based 3D printing wave-absorbing materials and preparation method thereof.The 3D printing wave-absorbing material includes the following components by mass fraction: polyetherimide resin or polyether ether ketone resin: 45~65 parts;Electromagnetic wave absorber: 10~50 parts;Impact modifier: 4~12 parts;Flow aid: 2~8 parts;Antioxidant: 0.5~3 parts;Wherein, the electromagnetic wave absorber includes magnetic absorber and carbon-based absorber, the impact modifier and the carbon-based absorber are pre-coated to form the carbon-based absorber coated with the impact modifier on the surface, and the magnetic absorber is surface modified by silane coupling agent.The application significantly improves the mechanical properties and thermal stability of the material by using specific raw material composition and combining specific multi-layer co-extrusion and online heat treatment process.The preparation process is simple and easy to operate, and is suitable for industrial continuous production.

Description

Technical Field

[0001] This invention relates to a 3D-printed microwave absorbing material, specifically a PEI or PEEK-based 3D-printed microwave absorbing material, and also to its preparation method, belonging to the field of functional polymer composite materials technology. Background Technology

[0002] Polyetherimide (PEI) and polyetheretherketone (PEEK), as important specialty engineering plastics, have attracted much attention in high-end fields such as aerospace and defense due to their excellent high-temperature resistance, high strength, high rigidity, good flame retardancy, and dimensional stability. Adding electromagnetic wave absorbers (such as carbonyl iron powder and carbon nanotubes) to PEI or PEEK matrices to prepare 3D-printed components with electromagnetic wave absorption capabilities is an effective way to achieve integrated structure-function manufacturing.

[0003] However, to obtain good electromagnetic wave absorption performance, it is usually necessary to fill the matrix with a high content (typically the total absorber content is greater than >10 wt%) of absorbing agent, which raises a series of technical problems:

[0004] (1) Uneven dispersion of microwave absorbers: High surface energy microwave absorber particles, especially nanomaterials (such as carbon nanotubes) and high-density micron-sized metal powders, are prone to agglomeration during melt processing, resulting in uneven dispersion. This not only causes unstable electromagnetic properties and significant anisotropy, but also the agglomerates act as stress concentration points, further deteriorating the material properties;

[0005] (2) Brittle fracture of filament: High content of rigid filler seriously hinders the movement and entanglement of PEI and PEEK molecular chains, significantly reduces the toughness of the material, resulting in high brittleness of composite material. 3D printing filament is prone to breakage during winding, unwinding or printing process, and the impact strength of printed parts is low.

[0006] (3) High melt viscosity leads to processing difficulties: The addition of a large amount of filler drastically increases the melt viscosity of the composite system. In the twin-screw melt blending and granulation stage, this manifests as excessive torque, high energy consumption, and difficulty in dispersing fillers; in the single-screw extrusion and drawing stage, it leads to high extrusion pressure, unstable melt flow, uneven wire diameter, rough surface, and even inability to produce continuously and stably.

[0007] (4) Poor interlayer bonding performance: High filler systems usually lead to changes in melt surface tension and decreased fluidity. During the 3D printing process, the fusion between layers is insufficient, the interface diffusion and molecular chain entanglement are insufficient, resulting in low interlayer bonding strength of the part, which seriously affects the overall structural integrity and load-bearing capacity.

[0008] (5) Insufficient high temperature and high pressure resistance of printed structures: Extreme application environments such as aerospace require components to maintain stable performance under high temperature and high pressure (at least 150°C coupled with two atmospheres of pressure). However, highly filled composite materials are prone to performance degradation, deformation or even failure under high temperature and high pressure environments due to problems such as weak interfacial bonding, large internal stress and insufficient thermal stability.

[0009] Existing improvement methods are mostly limited to solving single problems, such as adding a single coupling agent to improve dispersion or adding a toughening agent to improve toughness. However, the overall performance of the material cannot be balanced, especially for matrices like PEI and PEEK, which have high melt viscosity and narrow processing windows, where traditional modification methods have limited effectiveness. Therefore, there is an urgent need to provide a PEI and PEEK-based 3D-printed microwave absorbing material with excellent overall performance and suitable for industrial production to solve the above problems. Summary of the Invention

[0010] To address the problems existing in the prior art, the first objective of this invention is to provide a PEI or PEEK-based 3D-printed microwave absorbing material. This material possesses excellent mechanical properties, good adhesion, and resistance to high temperatures and pressures.

[0011] The second objective of this invention is to provide a method for preparing PEI or PEEK-based 3D-printed microwave absorbing materials. This method is simple, low-cost, and suitable for continuous industrial production.

[0012] To achieve the above-mentioned technical objectives, the present invention provides a PEI or PEEK-based 3D-printed microwave absorbing material, comprising the following components by mass:

[0013] Polyetherimide resin or polyetheretherketone resin: 45~65 parts;

[0014] Electromagnetic wave absorber: 10-50 parts;

[0015] Impact modifier: 4-12 parts;

[0016] Flow aid: 2-8 parts;

[0017] Antioxidant: 0.5-3 parts;

[0018] The electromagnetic wave absorber includes a magnetic absorber and a carbon-based absorber. The impact modifier and the carbon-based absorber are pre-coated to form a carbon-based absorber with an impact modifier on the surface. The magnetic absorber is surface-modified by a silane coupling agent.

[0019] This invention, through the specific component ratios described above, achieves excellent comprehensive performance of the microwave absorbing material. Specifically, the magnetic absorber, surface-modified with a silane coupling agent, and the carbon-based absorber coated with an impact modifier, serve as electromagnetic wave absorbers. This ensures uniform nano / micron-level dispersion of the absorber within the PEI or PEEK matrix, without significant agglomerates. The carbon-based absorber coated with an impact modifier effectively prevents absorber agglomeration, forming a stable core-shell structure masterbatch. Flow aids improve the flowability of the raw materials, making the screw extrusion process smoother and more stable. Antioxidants enhance the material's thermal and oxygen stability and eliminate processing stress.

[0020] As a preferred embodiment, the PEI or PEEK-based 3D-printed microwave absorbing material comprises the following components by mass percentage:

[0021] Polyetherimide resin or polyetheretherketone resin: 45~65%;

[0022] Electromagnetic wave absorber: 10~50%;

[0023] Impact modifier: 4~12%;

[0024] Flow aid: 2-8%;

[0025] Antioxidant: 0.5~3%.

[0026] As a preferred embodiment, the mass ratio of the magnetic absorber to the carbon-based absorber is 10 to 1:1, more preferably 5 to 1:1. Controlling this ratio within a suitable range is beneficial for improving the overall performance of the material. However, excessive use of the electromagnetic absorber can cause printing blockage, while insufficient use can result in poor wave absorption performance.

[0027] As a preferred embodiment, the magnetic absorber is an iron compound, which includes at least one of carbonyl iron powder, iron-silicon-aluminum powder, and ferrite powder.

[0028] As a preferred embodiment, the carbon-based absorbent includes at least one of carbon nanotubes, graphene, and carbon nanofibers. Multi-walled carbon nanotubes are preferred.

[0029] As a preferred embodiment, the impact modifier includes at least one of impact modifier B-51, impact modifier B-31, impact modifier B-52, and impact modifier B-22. This type of impact modifier is well-suited to the system of the present invention, and preferably includes at least one of impact modifier B-51, impact modifier B-31, impact modifier B-52, and impact modifier B-22 manufactured by Kaneka Corporation of Japan.

[0030] As a preferred embodiment, the flow aid includes at least one of flow aids Hyper-C181 and Hyper-C100. This type of polymeric processing flow aid is suitable for the system of this invention, and preferably includes flow aids Hyper-C181 and / or Hyper-C100 produced by Wuhan Hyperbranched Resin Technology Co., Ltd.

[0031] As a preferred embodiment, the antioxidant includes at least one of antioxidant 2246, antioxidant 425, antioxidant 2246-S, and antioxidant 330.

[0032] As a preferred embodiment, the preparation method of the carbon-based absorbent coated with the impact modifier is as follows: the carbon-based absorbent and the impact modifier solution are mixed and ultrasonically dispersed, and then the solvent is removed by rotary evaporation to obtain the absorbent.

[0033] As a preferred embodiment, the method for surface modification of the magnetic absorber using a silane coupling agent is as follows: the magnetic absorber is mixed and reacted with a silane coupling agent solution, and after solid-liquid separation, a silane coupling agent-modified magnetic absorber is obtained. The silane coupling agent is preferably at least one of KH550, KH560, and KH570.

[0034] This invention also provides a method for preparing PEI or PEEK-based 3D printed microwave absorbing materials. The method involves mixing polyetherimide resin or polyetheretherketone resin with an electromagnetic wave absorber, a flow aid, and an antioxidant at different rotation speeds to obtain a premix. The premix is ​​then extruded and granulated using a twin-screw extruder to obtain a composite masterbatch. A multi-layer co-extrusion drawing system is then used to co-extrude the composite masterbatch and a core material coating skin material to obtain a composite core material with a coating skin. The composite core material is then subjected to online heat treatment, cooling molding, traction, and winding processes to obtain the final product.

[0035] The multilayer co-extrusion fiber drawing system includes a core material extrusion unit, a skin extrusion unit, and a co-extrusion die head with concentric annular flow channels. Composite masterbatch is added to the core material extrusion unit, and core material is added to the skin extrusion unit to coat the skin material. The core melt obtained by the core material extrusion unit flows out from the central flow channel of the co-extrusion die head, and the skin melt obtained by the skin extrusion unit flows out from the annular flow channel of the co-extrusion die head. Finally, the two melts merge at the die of the co-extrusion die head.

[0036] This invention obtains 3D printed filaments with a special "skin-core" structure through a specific multi-layer co-extrusion drawing system process supplemented by online heat treatment. The multi-layer co-extrusion die head used in this invention is a special die head with a concentric annular flow channel. The core material melt passes through the central flow channel, and the skin melt passes through the annular flow channel surrounding the central flow channel. The two converge at the die head orifice to form a composite structure in which the core material is uniformly covered by the skin.

[0037] Meanwhile, online heat treatment before the composite filament enters the cooling device can significantly improve the filament performance. This heat treatment step can eliminate the internal stress generated by rapid cooling of the core layer, promote further fusion between the core layer and the surface layer at the interface, enhance interlayer bonding, and also facilitate the adjustment of the crystallinity of the surface material, so that it has better melt bonding behavior during printing.

[0038] As a preferred embodiment, the core material extrusion unit is a main single-screw extruder. This extruder is used to process high-viscosity, high-filling PEI or PEEK microwave absorbing composite masterbatch (core material).

[0039] As a preferred embodiment, the skin extrusion unit is an auxiliary single-screw extruder. The auxiliary single-screw extruder is used to process specially formulated high-adhesion polymers (skin materials).

[0040] As a preferred embodiment, the core material covering the outer skin material includes at least one of polyphthalamide and polyethersulfone.

[0041] As a preferred embodiment, the volume ratio of the core material to the outer sheath in the composite core material is 4 to 8:1. The thickness ratio of the core material to the outer sheath is controlled by precisely adjusting the ratio of the output rates (screw speeds) of the two extruders. For example, for a wire with a final diameter of 1.75 mm, the surface thickness is controlled between 0.05 mm and 0.15 mm.

[0042] As a preferred option, the temperature of the core material extrusion unit is 320~410°C. This temperature range allows the core material to be fully plasticized but avoids decomposition.

[0043] As a preferred embodiment, the temperature of the skin extrusion unit is 320~410℃.

[0044] As a preferred option, the temperature of the co-extrusion die head is 320~410℃. The die head temperature needs to be precisely controlled, preferably set between the core material and skin processing temperatures. This allows for better adhesion and appropriate mutual diffusion of the two melt layers at the interface.

[0045] As a preferred option, the online heat treatment conditions are: temperature 200~230℃, time 2~10 seconds. Before the composite wire enters the cooling device, it undergoes instantaneous heat treatment through a temperature-controlled online heat treatment tunnel to improve wire performance. Furthermore, the combination of antioxidants and the online heat treatment process effectively enhances the material's thermo-oxidative stability and eliminates processing stress, enabling the material to retain more than 85% of its performance after long-term service under high temperature and high pressure (e.g., 200℃, 0.5MPa) conditions.

[0046] After heat treatment and cooling, the wire is processed into the final product through a precision traction and diameter measurement winding system: the diameter is monitored in real time by a laser diameter gauge, and the speed of the traction machine is controlled by feedback to ensure that the wire diameter tolerance is strictly controlled within ±0.05mm. Finally, a constant tension winding device is used to wind it up to obtain a 3D printed composite wire with a smooth surface and uniform structure.

[0047] As a preferred embodiment, the gradient mixing process is as follows: first, mix at low speed for 10 to 20 minutes at 80 to 100°C and 150 to 250 rpm, and then mix at medium speed for 20 to 40 minutes at 100 to 120°C and 250 to 300 rpm.

[0048] This invention employs gradient mixing of raw materials, enabling all solid components and additives to achieve uniform pre-dispersion and pre-coating at both the macroscopic and microscopic levels. This improves the stability of the subsequent "multi-stage temperature-controlled and shear-controlled screw process." First, mixing is performed at 80-100℃ and low speed for 10-20 minutes to allow the additives to initially disperse and adsorb onto the filler surface. Then, the temperature is increased to 100-120℃ and mixing is performed at medium speed for 20-40 minutes to further enhance the mixing of the components.

[0049] As a preferred embodiment, during the extrusion granulation process of the twin-screw extruder, the screw is divided into three sections: the first section is located in the first 1 / 3 of the screw, with a heating temperature of 320~350℃; the second section is located in the middle of the screw, with a heating temperature of 360~385℃; and the third section is located in the last 1 / 3 of the screw, with a heating temperature of 390~410℃. The screw speed is 50~70 rpm. This invention employs multi-stage temperature-controlled and shear-controlled melt blending granulation, using a co-rotating twin-screw extruder with a length-to-diameter ratio (L / D) ≥ 40. The melt is extruded through a die, cooled, and pelletized to obtain composite masterbatch. The twin-screw extruder performs blending in three process stages:

[0050] First stage (low-temperature, high-shear dispersion stage, corresponding to the first 1 / 3 of the screw): The premix obtained in step one is added through the main feed port. The barrel temperature in this stage is set to 320~350℃, and the screw speed is set to 50~70 rpm. The lower melt temperature inhibits premature complete melting of PEI or PEEK, and combined with high shear force, it prioritizes efficient dispersion of the microwave absorber and forced coating of the interface modifier.

[0051] The second stage (medium-temperature, medium-shear melting stage, corresponding to the middle 1 / 3 of the screw): The barrel temperature in this stage is set to 360~385℃, and the screw speed is set to 50~70rpm. During this stage, the PEI or PEEK matrix is ​​fully melted.

[0052] The third stage (high-temperature, low-shear homogenization and exhaust stage, corresponding to the last 1 / 3 of the screw): Set the barrel temperature to 390~410℃ and the screw speed to 50~70 rpm, and activate vacuum exhaust. The higher temperature is beneficial for the full homogenization of the melt and the removal of small molecule volatiles, while avoiding secondary agglomeration of the dispersed packing.

[0053] In addition, the introduction of a high-molecular-weight processing flow aid (hyperbranched polymer) in this invention, combined with an optimized multi-screw process, significantly reduces the melt viscosity and processing torque of the high-filler system, resulting in stable twin-screw granulation, smooth single-screw wire drawing, and good wire quality consistency.

[0054] Through the above-described process steps, the present invention can achieve the following effects:

[0055] A leap forward in interlayer bonding properties: During printing, the surface layer of the filament (low melting point, high adhesion) melts before the core layer, and can fully wet and penetrate the surface of the printed layer like a "hot melt adhesive", forming a very strong mechanical interlock and physicochemical bond, which can increase the interlayer shear strength of the printed part by 80% to 150% compared with pure core layer filament.

[0056] Pure preservation of core layer performance: The core layer material does not need to sacrifice the content of the absorbing agent or add additives that affect the electromagnetic performance in order to accommodate adhesion. It can fully optimize its electromagnetic wave absorption performance and body mechanical strength.

[0057] Printing process friendliness: Surface materials typically have better lubricity and a wider printing temperature window, reducing the risk of printhead clogging and improving the stability of the printing process and the surface quality of the formed parts.

[0058] Perfect division of function and structure: It truly realizes the collaborative design of "core material is responsible for function (wave absorption and load bearing)" and "outer skin is responsible for process (bonding and molding)", which can solve the internal performance conflicts of multifunctional composite materials.

[0059] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0060] (1) The present invention obtains a 3D printed microwave absorbing material with a "skin-core" structure, which has excellent mechanical properties, bonding properties and high temperature and high pressure resistance.

[0061] (2) The method is simple, the process is short, the cost is low, and it is suitable for continuous industrial production. Detailed Implementation

[0062] The technical solution 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. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0063] Example 1

[0064] Core material raw material composition: 52% polyetherimide resin, 28% flake carbonyl iron powder, 8% multi-walled carbon nanotubes, 6% impact modifier B-51, 5.5% high-molecular processing flow aid Hyper-C181, and 0.5% antioxidant 2246.

[0065] Skin material: Polyphthalamide (PPA).

[0066] Surface modification process of carbonyl iron powder: Place the flake carbonyl iron powder in a high-speed mixer (350 rpm), spray it with 1.5% by weight of KH-550 silane coupling agent ethanol solution at 100℃, and treat for 20 minutes.

[0067] Preparation process of multi-walled carbon nanotubes coated with surface modifier B-51: Multi-walled carbon nanotubes and modifier B-51 were added to N-methylpyrrolidone and ultrasonically dispersed for 1.5 hours, and then the solvent was removed by rotary evaporation.

[0068] Preparation of 3D-printed microwave absorbing materials:

[0069] (1) Polyetherimide resin, carbonyl iron powder modified with silane coupling agent, multi-walled carbon nanotubes with surface coating modifier B-51, high molecular weight processing flow aid Hyper-C181 and antioxidant are added to a high-speed mixer according to the above mass composition. First, mix at low speed at 90°C and 150 rpm for 15 minutes, then heat to 110°C and mix at medium speed at 260 rpm for 30 minutes to obtain a premix.

[0070] (2) A co-rotating twin-screw extruder is used to add the above premixed material from the main feed port. The process parameters are set as follows:

[0071] First stage (zones 1-4, low temperature and high shear): 340℃ / 345℃ / 350℃ / 350℃, screw speed 50rpm.

[0072] Second stage (zones 5-7, medium temperature melting): 375℃ / 380℃ / 385℃, screw speed 50 rpm.

[0073] Third stage (zones 8-10, high-temperature homogenization): 400℃ / 405℃ / 400℃, screw speed 50 rpm, vacuum exhaust turned on.

[0074] The melt is extruded through a die, cooled in water, and pelletized to obtain a core material composite masterbatch, which is then vacuum dried at 150°C for 12 hours.

[0075] (3) A one-to-two co-extrusion system is adopted, equipped with a core material single screw extruder (A), a skin single screw extruder (B), a concentric annular gap co-extrusion die and an online heat treatment tunnel furnace.

[0076] Core material extrusion: Add the above-mentioned dried core material composite masterbatch to the core material single screw extruder (A), and set the temperature of each zone as follows: 340℃ / 360℃ / 375℃ / 390℃ / 400℃.

[0077] Skin extrusion: Add the skin material polyphthalamide (PPA) to the skin single-screw extruder (B), and set the temperature of each zone as follows: 320℃ / 340℃ / 355℃ / 370℃ / 380℃.

[0078] Co-extrusion and molding: Adjust the speed of extruders A and B, with extruder A at 60 rpm and extruder B at 40 rpm, so that the volume ratio of core material to skin is 6:1 (corresponding to a final core material diameter of about 1.65 mm and a skin thickness of about 0.05 mm). The co-extrusion die temperature is 385℃ to obtain a composite wire with a "skin-core" structure.

[0079] Online heat treatment: The extruded composite wire is immediately passed through a tunnel furnace set to 220°C for 5 seconds.

[0080] Cooling and winding: The wire after online heat treatment is cooled in a water cooling tank and monitored by a laser diameter measuring instrument. The traction machine automatically adjusts to ensure that the diameter is stable at 1.75 ± 0.02 mm. Finally, it is wound up under constant tension to obtain PEI-based 3D printed microwave absorbing material.

[0081] The PEI-based 3D-printed microwave absorbing material prepared in this embodiment was subjected to relevant performance tests. The interlaminar shear strength test standard was based on GB / T1455-2005 "Test Method for Shear Properties of Sandwich Structures or Cores", the tensile strength test standard was based on GB / T1040.1-2018 "Determination of Tensile Properties of Plastics Part 1: General Rules", and the notched impact strength test standard was based on GB / T 1043.1-2008 "Determination of Impact Properties of Simply Supported Beams of Plastics Part 1: Non-Instrumental Impact Tests". The relevant test results are as follows:

[0082] Mechanical properties: The wire is flexible and can withstand repeated bending of 180 degrees without breaking. The tensile strength is 72 MPa and the notched impact strength is 48 J / m.

[0083] Interlayer adhesion performance: interlayer shear strength reaches 4 MPa;

[0084] High temperature and high pressure resistance: After the printed sample was placed in an environment of 200℃ and 0.5 MPa for 100 hours, the tensile strength retention rate was 93% and the impact strength retention rate was 89%.

[0085] Example 2

[0086] Core material raw material composition: 46% polyetherimide resin, 28% flake carbonyl iron powder, 8% multi-walled carbon nanotubes, 12% impact modifier B-51, 5.5% high-molecular processing flow aid Hyper-C181, and 0.5% antioxidant 2246.

[0087] Skin material: Polyphthalamide (PPA).

[0088] The carbonyl iron powder surface modification treatment and carbon-based absorber pre-coating treatment were carried out in accordance with the method of Example 1. Then, the 3D printed microwave absorbing material was prepared in accordance with the method of Example 1. In order to adapt to the viscosity change of the system, the temperature of the third section of the twin screw in step (2) was increased by 5°C, and the temperature of each zone of the core material extrusion in step (3) was increased by 5°C.

[0089] Under the conditions of this embodiment, the mechanical properties are outstanding, with the notched impact strength increased to 55 J / m and the interlaminar shear strength simultaneously increased to 6.5 MPa.

[0090] Example 3

[0091] The core material raw material composition is as follows: polyetheretherketone resin 52%, iron-silicon-aluminum powder 20%, carbon nanofiber powder 16%, impact modifier B-52 6%, polymeric processing flow aid 5.5%, and antioxidant 425 0.5%. Among them, the iron-silicon-aluminum powder was purchased from the Metal Research Institute of China Metallurgical Group Corporation, and the carbon nanofiber was purchased from Hangzhou Gaoke Composite Materials Co., Ltd.

[0092] Skin material: Polyethersulfone (PES).

[0093] The surface pretreatment of raw materials iron-silicon-aluminum powder and carbon nanofiber powder was carried out using the method of Example 1.

[0094] The method of Example 1 was used to prepare 3D printed microwave absorbing material. The difference is that the temperature of the co-extrusion and molding die head in step (3) is 382°C, and the temperature of the online heat treatment is 220°C for 10 seconds.

[0095] The PEEK-based 3D-printed microwave absorbing material prepared under the conditions described in this embodiment was subjected to relevant performance tests, and the results are as follows:

[0096] Mechanical properties: The wire is flexible and can be repeatedly bent 180 degrees without breaking. Its tensile strength is 75 MPa and its notched impact strength is 50 J / m.

[0097] Interlayer adhesion performance: interlayer shear strength reaches 4.6 MPa;

[0098] High temperature and high pressure resistance: After the 3D printed microwave absorbing material sample was placed in an environment of 200℃ and 0.5 MPa for 100 hours, the tensile strength retention rate was 95% and the impact strength retention rate was 90%.

[0099] Example 4

[0100] The 3D printed microwave absorbing material was prepared using the method of Example 1, with the difference being that the core material raw material composition was as follows: 65% polyether ether ketone resin, 18% iron-silicon-aluminum powder, 5% multi-walled carbon nanotubes, 6% impact modifier B-51, 5.5% polymeric processing flow aid Hyper-C181, and 0.5% antioxidant 2246.

[0101] The relevant performance test results of the PEEK-based 3D-printed microwave absorbing material prepared under the conditions of this embodiment are as follows:

[0102] Mechanical properties: The wire is flexible and can withstand repeated bending of 180 degrees without breaking. The tensile strength is 85 MPa and the notched impact strength is 62 J / m.

[0103] Interlayer adhesion performance: interlayer shear strength reaches 4.2 MPa;

[0104] High temperature and high pressure resistance: After the printed sample was placed in an environment of 200℃ and 0.5 MPa for 100 hours, the tensile strength retention rate was 95% and the impact strength retention rate was 90%.

[0105] Comparative Example 1

[0106] The core material was prepared according to the composition ratio of the core material in Example 1 and the method of Example 1. The difference is that step (3) adopts the ordinary single-layer extrusion process, that is, only the core material is extruded and the skin is not co-extruded.

[0107] The relevant properties of the 3D-printed microwave absorbing material obtained under the comparative conditions are as follows:

[0108] Mechanical properties: The wire is flexible and can be repeatedly bent 180 degrees without breaking. Its tensile strength is 70 MPa and its notched impact strength is 20 J / m.

[0109] Interlayer adhesion performance: interlayer shear strength is 1.2 MPa.

[0110] The mechanical properties of the microwave absorbing material prepared under the comparative conditions are significantly lower than those of Example 1, indicating that the co-extrusion process can significantly improve the overall performance of the material.

[0111] Comparative Example 2

[0112] The method of Example 1 was used to prepare 3D printed microwave absorbing material, except that the online heat treatment procedure in step (3) was omitted.

[0113] The microwave absorbing material prepared under the comparative conditions has a tensile strength of 36 MPa and a notched impact strength of 20 J / m, which are significantly lower than those in the embodiments of this invention. It is evident that the wire, without online heat treatment, suffers a significant decrease in tensile strength and notched impact strength due to stress concentration and poor bonding between the core and surface layers.

[0114] Comparative Example 3

[0115] The method of Example 1 was used to prepare 3D printed microwave absorbing materials, except that the carbonyl iron powder surface modification treatment was omitted, and the pre-coating treatment of multi-walled carbon nanotubes was also omitted. Instead, multi-walled carbon nanotubes were directly mixed with impact modifier B-51.

[0116] The microwave absorbing material prepared under the comparative conditions was brittle, breaking after two 180-degree bends. Its tensile strength was 35 MPa, notched impact strength was 25 J / m, and interlaminar shear strength was 3.2 MPa. This indicates that the lack of surface pretreatment of the flake carbonyl iron powder and the absence of impact modifier pre-coating of the multi-walled carbon nanotubes resulted in uneven dispersion of the absorber components, leading to a significant decrease in material performance.

[0117] The above examples and comparative examples fully demonstrate that the present invention has successfully solved a series of problems in the dispersibility, toughness, processability, interlayer adhesion and environmental resistance of high-filled PEI absorbing materials, and the prepared filaments fully meet the application requirements of high-performance 3D printing.

[0118] Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A PEI or PEEK-based 3D-printed microwave absorbing material, characterized in that: Includes the following components by weight: Polyetherimide resin or polyetheretherketone resin: 45~65 parts; Electromagnetic wave absorber: 10-50 parts; Impact modifier: 4-12 parts; Flow aid: 2-8 parts; Antioxidant: 0.5-3 parts; The electromagnetic wave absorber includes a magnetic absorber and a carbon-based absorber. The impact modifier and the carbon-based absorber are pre-coated to form a carbon-based absorber with an impact modifier on the surface. The magnetic absorber is surface-modified by a silane coupling agent.

2. The PEI or PEEK-based 3D-printed microwave absorbing material according to claim 1, characterized in that: The mass ratio of the magnetic absorbent to the carbon-based absorbent is 10 to 1:

1.

3. A PEI or PEEK-based 3D-printed microwave absorbing material according to claim 1 or 2, characterized in that: The magnetic absorbent is an iron compound, which includes at least one of carbonyl iron powder, iron-silicon-aluminum powder, and ferrite powder. The carbon-based absorbent includes at least one of carbon nanotubes, graphene, and carbon nanofibers.

4. The PEI or PEEK-based 3D-printed microwave absorbing material according to claim 1, characterized in that: The impact modifier includes at least one of impact modifier B-51, impact modifier B-31, impact modifier B-52, and impact modifier B-22; The flow aid includes at least one of flow aid Hyper-C181 and flow aid Hyper-C100; The antioxidant includes at least one of antioxidant 2246, antioxidant 425, antioxidant 2246-S, and antioxidant 330.

5. The PEI or PEEK-based 3D-printed microwave absorbing material according to claim 1, characterized in that: The preparation method of the carbon-based absorbent coated with the impact modifier is as follows: the carbon-based absorbent and the impact modifier solution are mixed and ultrasonically dispersed, and then the solvent is removed by rotary evaporation to obtain the absorbent. The method for surface modification of the magnetic absorber by silane coupling agent is as follows: the magnetic absorber is mixed and reacted with a silane coupling agent solution, and after solid-liquid separation, a silane coupling agent modified magnetic absorber is obtained.

6. A method for preparing a PEI or PEEK-based 3D-printed microwave absorbing material according to claims 1-5, characterized in that: Polyetherimide resin or polyetheretherketone resin is mixed with electromagnetic wave absorber, flow aid and antioxidant at different speeds to obtain a premix. The premix is ​​extruded and granulated by a twin-screw extruder to obtain a composite masterbatch. Then, the composite masterbatch and the core material coating skin material are co-extruded and drawn into fibers using a multi-layer co-extrusion fiber drawing system to obtain a composite core material with a coating skin. The composite core material is then subjected to online heat treatment, cooling and molding, traction and winding processes in sequence to obtain the final product. The multilayer co-extrusion fiber drawing system includes a core material extrusion unit, a skin extrusion unit, and a co-extrusion die head with concentric annular flow channels. Composite masterbatch is added to the core material extrusion unit, and core material is added to the skin extrusion unit to coat the skin material. The core melt obtained by the core material extrusion unit flows out from the central flow channel of the co-extrusion die head, and the skin melt obtained by the skin extrusion unit flows out from the annular flow channel of the co-extrusion die head. Finally, the two melts merge at the die of the co-extrusion die head.

7. The method for preparing a PEI or PEEK-based 3D-printed microwave absorbing material according to claim 6, characterized in that: The core material extrusion unit is a main single-screw extruder; The skin extrusion unit is an auxiliary single-screw extruder; The core material covering the outer skin material includes at least one of polyphthalamide and polyethersulfone; The volume ratio of the core material to the outer skin in the composite core material is 4~8:

1.

8. A method for preparing a PEI or PEEK-based 3D-printed microwave absorbing material according to claim 6 or 7, characterized in that: The core material extrusion unit temperature is 320~410℃; the skin extrusion unit temperature is 320~410℃; the co-extrusion die head temperature is 320~410℃; The conditions for online heat treatment are: temperature 200~230℃, time 2~10 seconds.

9. The method for preparing a PEI or PEEK-based 3D-printed microwave absorbing material according to claim 6, characterized in that: The gradient mixing process is as follows: first, mix at low speed for 10 to 20 minutes at 80 to 100°C and 150 to 250 rpm, and then mix at medium speed for 20 to 40 minutes at 100 to 120°C and 250 to 300 rpm.

10. The method for preparing a PEI or PEEK-based 3D-printed microwave absorbing material according to claim 6, characterized in that: During the extrusion granulation process of the twin-screw extruder, the screw is divided into three sections on average. The first section is located in the first 1 / 3 of the screw and is heated at 320~350℃. The second section is located in the middle of the screw and is heated at 360~385℃. The third section is located in the last 1 / 3 of the screw and is heated at 390~410℃. The screw speed is 50~70 rpm.