Ferroferric oxide electromagnetic absorption ink for 3D printing and preparation method of ferroferric oxide electromagnetic absorption ink

Abstract

The invention relates to ferroferric oxide electromagnetic absorption ink for 3D printing and a preparation method of the ferroferric oxide electromagnetic absorption ink, and belongs to the field of ink processing. The ferroferric oxide electromagnetic absorption ink is prepared from the following raw materials in parts by mass: 0.04 to 0.1 part of multiwalled carbon nanotubes, 0.05 to 0.2 part of polypyrrole, 0.1 to 0.5 part of ferroferric oxide, 30 to 36 parts of hyperbranched polyester acrylate resin, 48 to 56 parts of acryloylmorpholine, 8 to 12 parts of 1, 6-hexanediol diacrylate, 2.5 to 5 parts of a photoinitiator, 0.5 to 1.5 parts of a defoaming agent, 0.5 to 2 parts of a dispersing agent and 1 to 3.5 parts of a surfactant. The ink greatly improves the electromagnetic wave absorption capability of the material, and has a wide absorption frequency band. The electromagnetic absorber is high in curing speed, high in forming precision, not prone to deformation after being cured, good in mechanical property and capable of being applied to rapid manufacturing of high-precision electromagnetic absorbers with different shapes in the military and civil fields.

Description

Technical Field

[0001] The present invention relates to the field of ink processing, and in particular, to a magnetite electromagnetic absorption ink for 3D printing and a preparation method thereof, and more particularly to a multi-walled carbon nanotube / polypyrrole / magnetite electromagnetic absorption ink suitable for ultraviolet light-curing 3D printing and a preparation method thereof. Background Art

[0002] With the development of modern science and technology, electromagnetic radiation has become an inevitable pollution source, and its impact on human production and life is increasing day by day. Military and civilian electronic instruments are becoming more and more miniaturized, and higher demands are put forward for the precision of equipment, the stability of instruments, the security of data, etc. The interference of electromagnetic radiation on electronic instruments will affect the normal operation of space exploration equipment, military machines, scientific equipment, surveillance cameras, etc. Electromagnetic absorption materials are materials that can convert the incident harmful electromagnetic wave energy into other forms of energy and dissipate it, and are rarely reflected back.

[0003] Polymer-based electromagnetic absorption materials have the advantages of high flexibility, good corrosion resistance, low cost, good processability, etc., and can better meet the needs of fields such as aerospace and electronic communication, showing great advantages in the field of electromagnetic absorption materials. At present, when preparing polymer-based electromagnetic absorbers by 3D printing, mainly fused deposition modeling (FDM) type 3D printers are used, and the printing accuracy of this type of printer is not high (generally the accuracy is 500 μm). UV light-curing forming (DLP, SLA type) is one of the 3D printing methods with the highest accuracy (generally the accuracy is 10 μm), and it cures and forms through the chain polymerization reaction of monomers and prepolymers in the resin initiated by ultraviolet light. Selecting UV light-curing resin as the matrix material, filling with electromagnetic absorption agents to prepare electromagnetic absorption ink, and using UV light-curing 3D printing for printing can quickly design and print various complex-shaped and high-precision electromagnetic absorbers, expanding the application range of electromagnetic absorption materials.

[0004] Multi-walled carbon nanotubes have a special helical structure and chirality, can exhibit strong broadband absorption performance, and have the advantages of low specific gravity, high-temperature oxidation resistance, adjustable dielectric properties, and good stability. Therefore, they are an ideal microwave absorber, and these advantages make them a very potential microwave absorption material in military stealth and civilian microwave radiation protection. At the same time, polypyrrole is also a relatively ideal wave-absorbing material due to its many advantages such as chemical stability, wide range of conductivity changes, and easy synthesis. However, both multi-walled carbon nanotubes and polypyrrole basically have no magnetism and very small magnetic losses, which limit the improvement of their wave-absorbing performance.

[0005] As a kind of double complex medium, magnetic iron oxide has stable magnetic properties and strong microwave absorption characteristics. Moreover, its preparation methods are simple, diverse, and easy to control. Currently, it is still widely used in the preparation of microwave absorption materials. In the field of microwave absorption, the combination of iron oxide nanoparticles with excellent magnetic loss and multi-walled carbon nanotubes and polypyrrole with dielectric loss can achieve the combination of dielectric and magnetic properties, endowing the composite material with both magnetic loss and dielectric loss, and dissipating electromagnetic wave energy through multiple loss mechanisms.

[0006] Currently, polymer-based electromagnetic absorbers are mainly formed through molds and calendering, with complex processes, long production cycles, and poor precision. 3D printing technology, also known as 3D rapid prototyping technology, is an additive manufacturing technology. First, the model structure is designed using 3D modeling software in a computer, and then a 3D object with a complex structure is quickly manufactured through precise 3D stacking forming. In some literature, a fused deposition modeling (FDM) type 3D printer is used to prepare electromagnetic absorption materials, but the printing precision of this printer is not high (generally 500 μm). The added electromagnetic absorbers are mainly single carbon materials (electric loss materials) or magnetic metal oxide materials (magnetic loss materials), with a narrow electromagnetic wave absorption width, poor mechanical strength of the materials, not wear-resistant, easy to break, and prone to deformation at high temperatures. Summary of the Invention

[0007] In view of this, in order to solve the above-mentioned many technical problems, the present invention provides a multi-walled carbon nanotube / polypyrrole / iron oxide electromagnetic absorption ink suitable for ultraviolet light-curing 3D printing and its preparation method.

[0008] The first object of the present invention is to provide a multi-walled carbon nanotube / polypyrrole / iron oxide electromagnetic absorption ink suitable for ultraviolet light-curing 3D printing. By using hyperbranched polyester acrylate resin, 1,6-hexanediol diacrylate, and acryloylmorpholine in combination, the resins in the formulation have good mutual compatibility, no delamination phenomenon, and enhance the wetting effect on the multi-walled carbon nanotube / polypyrrole / iron oxide absorbent. At the same time, it has good stability, fluidity, and rapid curing and forming performance. When added to a light-curing 3D printer, the ink can meet the printing requirements, has good dimensional stability after curing and forming, high mechanical strength, stable physical and chemical properties under high-temperature conditions and is not prone to deformation, has very strong electromagnetic absorption ability, and a relatively wide absorption band. It can be applied to the rapid manufacturing of electromagnetic absorbers with various shapes and high precision in military and civilian fields.

[0009] The second object of the present invention is to provide a preparation method for the above-mentioned multi-walled carbon nanotube / polypyrrole / iron oxide electromagnetic absorption ink suitable for ultraviolet light-curing 3D printing. The preparation method has the advantages of being able to completely retain the effective components of the raw materials, and is also simple and easy to operate, with closely connected front and back steps, and mild operating conditions.

[0010] To achieve the above object of the present invention, the following technical solutions are adopted:

[0011] A multi-walled carbon nanotube / polypyrrole / iron oxide electromagnetic absorption ink suitable for ultraviolet-curable 3D printing is mainly prepared from the following raw materials: by mass, 0.04 - 0.1 part of multi-walled carbon nanotubes, 0.05 - 0.2 part of polypyrrole, 0.1 - 0.5 part of iron oxide, 30 - 36 parts of hyperbranched polyester acrylate resin, 48 - 56 parts of acryloylmorpholine, 8 - 12 parts of 1,6 - hexanediol diacrylate, 2.5 - 5 parts of photoinitiator, 0.5 - 1.5 parts of defoamer, 0.5 - 2 parts of dispersant, and 1 - 3.5 parts of surfactant.

[0012] To further optimize the raw material formula, the amounts of raw materials are: 0.07 - 0.09 part of multi-walled carbon nanotubes, 0.09 - 0.12 part of polypyrrole, 0.25 - 0.45 part of iron oxide, 32 - 35 parts of hyperbranched polyacrylate resin, 48 - 53 parts of acryloylmorpholine, 9 - 11 parts of 1,6 - hexanediol diacrylate, 2.5 - 4 parts of photoinitiator, 0.5 - 1.2 parts of defoamer, 0.5 - 1.5 parts of dispersant, and 1.2 - 1.5 parts of surfactant.

[0013] In addition, the amounts of raw materials can also be: 0.05 - 0.1 part of multi-walled carbon nanotubes, 0.1 - 0.15 part of polypyrrole, 0.22 - 0.35 part of iron oxide, 50 - 56 parts of acryloylmorpholine, 32 - 36 parts of hyperbranched polyacrylate resin, 10 - 12 parts of 1,6 - hexanediol diacrylate, 3 - 4 parts of photoinitiator, 1 - 1.5 parts of defoamer, 1 - 1.5 parts of dispersant, and 1.5 - 3 parts of surfactant.

[0014] More preferably, 0.08 - 0.1 part of multi-walled carbon nanotubes, 0.12 - 0.15 part of polypyrrole, 0.3 - 0.35 part of iron oxide, 51 - 54 parts of acryloylmorpholine, 33 - 34 parts of hyperbranched polyacrylate resin, 10 - 11 parts of 1,6 - hexanediol diacrylate, 1.2 - 1.4 parts of photoinitiator, 1.2 - 1.5 parts of defoamer, 1 - 1.2 parts of dispersant, and 1.7 - 2.2 parts of surfactant.

[0015] Among them, carbon nanotubes have the characteristics of low cost, good chemical stability, good mechanical properties, and excellent electromagnetic absorption performance. Polypyrrole, as a typical conductive polymer material, is a colorless oily liquid at room temperature and has the advantages of good environmental stability, environmental friendliness, a wide and adjustable conductivity range, etc. Magnetic iron tetroxide, as a double complex medium, has stable magnetic properties and strong microwave absorption characteristics and is still widely used in the preparation of wave-absorbing materials. Selecting these three materials to be mixed as the wave-absorbing agent can achieve the synergistic effect of magnetic loss and electrical loss, and can greatly improve the electromagnetic wave absorption ability of the material. In addition, acryloylmorpholine and 1,6-hexanediol diacrylate are selected as the monomer components in the resin, and hyperbranched polyester acrylate resin is used as the oligomer, which can ensure the mechanical strength of the formed sample, and has a relatively fast curing rate, good dimensional stability, and good dispersibility for the added electromagnetic absorber.

[0016] Preferably, the inner diameter of the multi-walled carbon nanotubes is 5 - 15 nm, and the outer diameter is 30 - 80 nm.

[0017] Preferably, the iron tetroxide is in powder form with a particle size of 5 - 15 nm.

[0018] Preferably, the degree of branching of the hyperbranched polyacrylate resin is 0.5 - 0.9, the molecular weight is 1500 - 10000, the appearance is a light yellow or colorless transparent viscous liquid, and the viscosity is 8 - 10 Pa·s.

[0019] Preferably, the photoinitiator is 2,4,6-trimethylbenzoyl diphenylphosphine oxide.

[0020] Preferably, the defoamer in the present invention is a polyether silicone copolymer defoamer, including BYK-810, TEGO 920, TEGO 843, TEGO 883, and / or TEGO 825. In this way, by reducing the surface tension of the raw materials during the production of the ink, the purpose of suppressing the generation of foam can be achieved.

[0021] Preferably, the dispersant is a high molecular weight polymer solution, including BYK-163, BYK-9077, BYK-9151, BYK-111, and / or TEGO Dispers 670 wetting and dispersing agent. The concentration of the active component contained is more than 40 wt%. It can achieve the effects of reducing the time and energy required for the dispersion process, stabilizing the dispersed electromagnetic absorber, and can also modify the surface properties of the absorber particles, adjust the mobility of the multi-walled carbon nanotube / polypyrrole / iron tetroxide electromagnetic absorber particles. Through experiments, it is found that the effect is better when the content of the active component is more than 40 wt%.

[0022] Preferably, the surfactant is a polysiloxane-polyether copolymer surfactant, including Degussa TEGOTwin4100, Dow HW 1000, Sangjing Chemical ST-333, and / or Sangjing Chemical COATOSIL 77, which can significantly reduce the surface tension and increase the wettability of the ink on the substrate.

[0023] It should be noted that from the amounts of each raw material, it can be seen that the addition amount of acryloylmorpholine monomer is relatively large, which can reduce the overall viscosity of the resin system, improve the leveling property, make it not easy to generate bubbles, and ensure a certain curing rate and mechanical strength. The hyperbranched polyacrylate resin acts as a prepolymer to increase the curing speed, and 1,6-hexanediol diacrylate acts to increase the accuracy of the formed sample and is mainly used in combination with the first two resins, so the addition amount is relatively small. 2,4,6-Trimethylbenzoyl diphenylphosphine oxide is a free radical polymerization photoinitiator suitable for the ultraviolet light source of 3D printers (DLP, SLA type). The specific addition amounts of these raw materials were determined through a large amount of creative work by the inventors. Only when controlled within an appropriate range can the prepared ultraviolet-curable 3D printing multi-walled carbon nanotube / polypyrrole / iron oxide electromagnetic absorption ink meet the required use performance. If the addition amount of a certain raw material is too large or too small, it will affect the mechanical properties of the final ink. In addition, although various additives are common raw materials in this field and are also added correspondingly in other 3D printing ink formulations, their amounts have been adjusted accordingly to adapt to the specific raw material system of the present invention. It is necessary to strictly follow the scheme of the present invention to perform the operation of ingredient preparation and not to randomly change the ingredient amounts.

[0024] The multi-walled carbon nanotube / polypyrrole / iron oxide electromagnetic absorption ink of the present invention suitable for ultraviolet-curable 3D printing can be used on a photo-curable 3D printer with a printing accuracy of 10 μm, and can print various complex-shaped and high-precision microwave absorbers. The main raw materials in this ink are hyperbranched polyester acrylate resin, 1,6-hexanediol diacrylate, and acryloylmorpholine. These resins are used because of their relatively fast reaction speed, high forming strength and accuracy. As an electromagnetic absorber, iron oxide / carbon nanotubes are added to the UV-curable resin to prepare an electromagnetic absorption ink with a synergistic electromagnetic wave dissipation effect of magnetic loss and electrical loss, which can greatly improve the electromagnetic wave absorption ability of the material, and has stable physical and chemical properties and is not easy to deform.

[0025] The electromagnetic absorption ink of iron oxide (Fe₃O₄) / carbon nanotube for ultraviolet (UV) curable 3D printing in the present invention is only applicable to UV curable 3D printers (DLP, SLA types), and is not applicable to other types of 3D printers, showing specificity. For example, laser etching type and fused deposition modeling 3D printers are not applicable to the ink of the present invention. When the inventor conducted specific practices, reasonable ingredients were specifically prepared for UV curable 3D printers. The performance of the ink in all aspects is also more suitable for the electromagnetic absorption field. Since the performance index requirements and standards of UV curable 3D printing inks in other industries are different, when formulating the raw materials of the ink, the types and dosages of the formula definitely need to be adjusted accordingly.

[0026] In addition to providing an electromagnetic absorption ink of multi-walled carbon nanotube / polypyrrole / iron oxide (Fe₃O₄) for UV curable 3D printing, the present invention also provides a preparation method of the 3D printing ink, including the following steps: mixing all raw materials, first performing mechanical stirring, after mixing evenly, performing grinding and dispersion, and obtaining the product after passing quality inspection, filtering and packaging.

[0027] Among them, the carbon nanotube / polypyrrole / iron oxide (Fe₃O₄) composite material mainly plays the role of electromagnetic absorption in the ink. Hyperbranched polyacrylate resin, acryloylmorpholine, and 1,6-hexanediol diacrylate are used as 3D printing resins, which play the role of dispersing the carbon nanotube / polypyrrole / iron oxide (Fe₃O₄) composite absorbent, and endow the ink with UV curable characteristics during printing, and form a polymer matrix with certain mechanical strength after drying. The dispersant is an interfacial active agent, which can reduce the interfacial tension between liquid and solid, enhance the wettability of the absorbent, improve the mixing and stirring efficiency. The dispersant adsorbs on the surface of the absorbent to form a charge effect or steric hindrance effect, preventing the microwave absorbent from flocculating and settling, and keeping the ink in a stable state. Since air bubbles are often generated during the stirring and grinding of the ink, affecting the grinding efficiency and effect, an antifoaming agent should be added to the ink system. During 3D printing, it is required that the ink has a good leveling effect to ensure the surface smoothness and precision requirements of the printed structure, so a surfactant needs to be added to reduce the surface tension of the ink system.

[0028] Among them, the rate of mechanical mixing and stirring of all raw materials is controlled between 260 - 450 rpm, and the stirring time is controlled between 25 - 40 min.

[0029] Preferably, a sand mill is used during the grinding process. The working pressure of the diaphragm pump of the sand mill is between 0.2 - 0.4 MPa, and it is ground repeatedly for 2 - 5 times to make the particle size of the ink product more uniform and the flatness better.

[0030] In addition, the ink of the present invention has good printing applicability, and the particle size of the grinding is controlled below 0.8 μm, preferably between 0.5 - 0.6 μm.

[0031] The preparation method of the multi-walled carbon nanotube / polypyrrole / iron tetroxide electromagnetic absorption ink of the present invention has the advantages of being able to completely retain the effective components of the raw materials, and also has the advantages of simple method, easy operation, tight connection of front and back steps, mild operation conditions, etc. The inventor finally adopted a better preparation route through repeated experiments.

[0032] No waste residue is generated during the whole operation process of the present invention, which is green and environmentally friendly, and the operation process is relatively simple and easy to industrialize. The above preparation method is only one of the better ones among many preparation methods, and does not represent the only preparation method. As long as the ink with the effect of the present invention is prepared by using the raw materials of the present invention, it is within the protection scope of the present invention.

[0033] In addition, the present invention also provides the application of the ultraviolet-curable 3D printing multi-walled carbon nanotube / polypyrrole / iron tetroxide electromagnetic absorption ink in ultraviolet-curable 3D printing. This ink can be used in UV-curable molding DLP-type and SLA-type 3D printers. The DLP 3D printer includes Creality LD-003, and the SLA 3D printer includes Formlabs form3+.

[0034] The ink of the present invention has good printing quality, strong electromagnetic loss ability, wide electromagnetic absorption frequency band, high mechanical strength, good surface flatness, low volume shrinkage rate, fast curing speed, and high forming accuracy. The ink of the present invention can be printed by using a UV-curable molding (DLP, SLA type) 3D printer to quickly manufacture electromagnetic absorbers with various shapes and high precision.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] (1) In the formula of the ink of the present invention, three materials, multi-walled carbon nanotube / polypyrrole / iron tetroxide, are compounded as the electromagnetic absorber. Among them, the multi-walled carbon nanotube has very excellent mechanical properties, and also has the electrical conductivity of metal materials and the light weight and easy processability of polymer materials. As a wave-absorbing material, it has excellent electromagnetic properties and is an ideal microwave absorption material. Polypyrrole, as a typical conductive polymer, has low cost, simple synthesis, low density, and excellent electrical conductivity. And magnetic iron tetroxide has stable magnetic properties and strong microwave absorption characteristics, and its preparation methods are simple, diverse, and easy to control, and it is currently widely used in the preparation of wave-absorbing materials. Compounding these three materials as the wave-absorbing agent can realize the combination of dielectric properties and magnetic properties, and dissipate electromagnetic wave energy through multiple loss mechanisms.

[0037] (2) The multi-walled carbon nanotube / polypyrrole / iron tetroxide electromagnetic absorption ink for UV-curable 3D printing of the present invention is applicable to printing by UV light-curable (DLP, SLA type) 3D printers. The production process of this ink is simple, it has good leveling property, high mechanical strength, good surface flatness, low volume shrinkage rate, fast curing speed and high forming accuracy after curing. For general metal alloy 3D printing inks, problems such as slow curing speed, poor dispersibility, poor stability and easy sedimentation are most likely to occur, and they cannot meet the requirements of printing machines. However, through reasonable combination and proportioning of raw materials, the present invention has well solved this technical problem.

[0038] (3) The preparation method of the multi-walled carbon nanotube / polypyrrole / iron tetroxide electromagnetic absorption ink for UV-curable 3D printing of the present invention has the advantages of being able to completely retain the effective components of the raw materials, and also has the advantages of simple method, easy operation, tight connection of front and back steps, mild operation conditions, etc. The inventor finally adopted a better preparation route through repeated experiments. Brief Description of the Drawings

[0039] Figure 1 It is a schematic diagram of 3D printing mechanical property test samples and electromagnetic parameter test samples;

[0040] Figure 2 It is the coaxial method sample size of the electromagnetic parameter test sample. Detailed Embodiments

[0041] The following will describe the implementation plan of the present invention in detail in conjunction with embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0042] The multi-walled carbon nanotube / polypyrrole / iron tetroxide electromagnetic absorption ink for UV-curable 3D printing of the present invention is mainly prepared from the following raw materials: by mass, 0.04 - 0.1 parts of multi-walled carbon nanotubes, 0.05 - 0.2 parts of polypyrrole, 0.1 - 0.5 parts of iron tetroxide, 30 - 36 parts of hyperbranched polyester acrylate resin, 48 - 56 parts of acryloylmorpholine, 8 - 12 parts of 1,6-hexanediol diacrylate, 3 - 5 parts of photoinitiator 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 0.5 - 1.5 parts of defoamer, 0.5 - 2 parts of dispersant, and 1 - 3.5 parts of surfactant. The preparation method includes: mixing all raw materials and stirring evenly, grinding and dispersing, and then, after passing quality inspection and filtering and packaging, the product is obtained.

[0043] Raw materials used in the following examples: Inner diameter of multi-walled carbon nanotubes: 5 - 15 nm, outer diameter: 30 - 80 nm, from Shanghai Aladdin; ferric oxide powder, particle size: 5 - 15 nm; hyperbranched polyacrylate resin: Shanghai Yinchang YC 2509S; photoinitiator: 2,4,6-trimethylbenzoyl diphenylphosphine oxide; defoamer: TEGO 843; dispersant: TEGO Dispers 670; surfactant: TEGO Twin4100.

[0044] Example 1

[0045] A preparation method of multi-walled carbon nanotube / polypyrrole / ferric oxide electromagnetic absorption ink applicable to ultraviolet-curable 3D printing is as follows:

[0046] 1) Weigh each raw material according to the following mass: 0.04 kg of multi-walled carbon nanotubes, 0.07 kg of polypyrrole, 0.12 kg of ferric oxide, 33.5 kg of hyperbranched polyacrylate resin, 50 kg of acryloylmorpholine, 9.5 kg of 1,6-hexanediol diacrylate, 3.5 kg of photoinitiator 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 0.9 kg of defoamer, 1 kg of dispersant, 1.3 kg of surfactant;

[0047] 2) Pour the above components into a stirring device after weighing, stir at a speed of 260 rpm with a mechanical stirrer for 35 minutes, then grind and disperse with a sand mill. The working pressure of the diaphragm pump is 0.23 MPa, and grind repeatedly for 3 - 4 times until the particle size is 0.6 - 0.8 μm. If the particle size does not meet the standard, continue to grind. Finally, detect the various indicators and properties of the ink, and filter and package it after passing the test to obtain the finished product.

[0048] Example 2

[0049] A preparation method of multi-walled carbon nanotube / polypyrrole / ferric oxide electromagnetic absorption ink applicable to ultraviolet-curable 3D printing is as follows:

[0050] 1) Weigh each raw material according to the following mass: 0.04 kg of multi-walled carbon nanotubes, 0.08 parts of polypyrrole, 0.18 kg of ferric oxide, 33.6 kg of hyperbranched polyacrylate resin, 50.3 kg of acryloylmorpholine, 9.3 kg of 1,6-hexanediol diacrylate, 3 kg of photoinitiator 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 1 kg of defoamer, 1 kg of dispersant, 1.5 kg of surfactant;

[0051] 2) Weigh the above components and pour them into a stirring device. Stir at a speed of 300 rpm with a mechanical stirrer for 40 minutes, then grind and disperse with a sand mill. The working pressure of the diaphragm pump is 0.4 MPa, and grind repeatedly for 2 - 4 times until the particle size is below 0.8 μm. If the particle size does not meet the standard, continue grinding. Finally, detect the various indicators and properties of the ink. After passing the test, filter and package to obtain the finished product.

[0052] Example 3

[0053] The preparation method of multi-walled carbon nanotube / polypyrrole / iron oxide electromagnetic absorption ink applicable to ultraviolet light-curing 3D printing is as follows:

[0054] 1) Weigh each raw material according to the following mass: 0.05 kg of multi-walled carbon nanotubes, 0.1 kg of polypyrrole, 0.25 kg of iron oxide, 33.5 kg of hyperbranched polyacrylate resin, 50 kg of acryloylmorpholine, 9 kg of 1,6-hexanediol diacrylate, 3 kg of photoinitiator 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 1.1 kg of defoamer, 1.5 kg of dispersant, 1.5 kg of surfactant;

[0055] 2) Weigh the above components and pour them into a stirring device. Stir at a speed of 400 rpm with a mechanical stirrer for 30 minutes, then grind and disperse with a sand mill. The working pressure of the diaphragm pump is 0.3 MPa, and grind repeatedly for 2 - 4 times until the particle size is below 0.75 μm. If the particle size does not meet the standard, continue grinding. Finally, detect the various indicators and properties of the ink. After passing the test, filter and package to obtain the finished product.

[0056] Example 4

[0057] The preparation method of multi-walled carbon nanotube / polypyrrole / iron oxide electromagnetic absorption ink applicable to ultraviolet light-curing 3D printing is as follows:

[0058] 1) Weigh each raw material according to the following mass: 0.07 kg of multi-walled carbon nanotubes, 0.13 kg of polypyrrole, 0.3 kg of iron oxide, 35 kg of hyperbranched polyacrylate resin, 48 kg of acryloylmorpholine, 10 kg of 1,6-hexanediol diacrylate, 4 kg of photoinitiator 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 0.5 kg of defoamer, 0.5 kg of dispersant, 1.5 kg of surfactant;

[0059] 2) Weigh the above components and pour them into a stirring device. Stir at a speed of 450 rpm with a mechanical stirrer for 35 minutes, then grind and disperse with a sand mill. The working pressure of the diaphragm pump is 0.30 MPa, and grind repeatedly for 3 - 4 times until the particle size is between 0.6 - 0.7 μm. If the particle size does not meet the standard, continue grinding. Finally, detect the various indicators and properties of the ink. After passing the test, filter and package to obtain the finished product.

[0060] Example 5

[0061] The preparation method of multi-walled carbon nanotube / polypyrrole / ferroferric oxide electromagnetic absorption ink suitable for UV-curable 3D printing is as follows:

[0062] 1) Weigh the following raw materials according to mass: 0.08 kg multi-walled carbon nanotubes, 0.17 kg polypyrrole, 0.35 kg ferrosoferric oxide, 33 kg hyperbranched polyacrylate resin, 51 kg acryloylmorpholine, 9 kg 1,6-hexanediol diacrylate, 2.8 kg photoinitiator 2,4,6-trimethylbenzoyldiphenoxyphosphine, 1.2 kg defoamer, 1.3 kg dispersant, and 1.1 kg surfactant;

[0063] 2) Weigh the above components and pour them into a stirring device. Stir them at 320 rpm for 25 minutes using a mechanical stirrer. Then disperse them by sand grinding with a sand mill. The working pressure of the diaphragm pump is 0.28 MPa. Grind them repeatedly 2-3 times until the particle size is below 0.65 μm. If the particle size does not meet the standard, continue grinding. Finally, test the various indicators and properties of the ink. After meeting the standards, filter and package the finished product.

[0064] Example 6

[0065] The preparation method of multi-walled carbon nanotube / polypyrrole / ferroferric oxide electromagnetic absorption ink suitable for UV-curable 3D printing is as follows:

[0066] 1) Weigh the following raw materials according to mass: 0.1 kg multi-walled carbon nanotubes, 0.2 kg polypyrrole, 0.50 kg ferrosoferric oxide, 32 kg hyperbranched polyacrylate resin, 50 kg acryloylmorpholine, 11 kg 1,6-hexanediol diacrylate, 3 kg photoinitiator 2,4,6-trimethylbenzoyldiphenoxyphosphine, 1 kg defoamer, 1 kg dispersant, and 1.2 kg surfactant;

[0067] 2) Weigh the above components and pour them into a stirring device. Stir them at 280 rpm for 30 minutes with a mechanical stirrer. Then disperse them with a sand mill. The working pressure of the diaphragm pump is 0.32 MPa. Repeat the grinding 2-4 times until the particle size is 0.5-0.6 μm. If the particle size does not meet the standard, continue grinding. Finally, test the various indicators and properties of the ink. After meeting the standards, filter and package the finished product.

[0068] Performance testing:

[0069] The multi-walled carbon nanotube / polypyrrole / ferroferric oxide electromagnetic absorption ink suitable for UV-curing 3D printing produced in Examples 1-6 was used to test the printing performance. The electromagnetic absorption material was printed using a UV-curing 3D printer (Chuangxiang 3D LD-003 3D printer). Figure 1As shown, there are samples for 3D printing mechanical property testing and samples for electromagnetic parameter testing. Both the 3D printing mechanical property testing samples and the electromagnetic parameter testing samples include real and imaginary parts, and the mechanical properties and electromagnetic properties are tested.

[0070] 1. Particle size μm: Refer to GB / T 1724-2019 Detection of Grinding Fineness of Printing Inks.

[0071] 2. Young's modulus MPa, tensile fracture length %, tensile stress MPa: Refer to GBT1040.2-2022 Determination of Tensile Properties of Plastics.

[0072] 3. Surface tension mN / m: At 25 °C, it is tested using a surface tension meter.

[0073] 4. Conductivity, permeability, electromagnetic loss (dB): Use a vector network analyzer (VNA, N5234A PAN-L, Agilent, USA) to analyze the electromagnetic parameters of the material, and the test frequency range is 2 - 18 GHz.

[0074] The electromagnetic property test of the sample is carried out on a vector network analyzer. The coaxial test fixture is connected to the two ports of the vector microwave network analyzer through two coaxial cables. Calibrate the system before measurement, and then carefully place the sample in the fixture, and conduct the test of electromagnetic parameters through the vector network analyzer.

[0075] For coaxial samples, as Figure 1 shown is the structural schematic diagram of the coaxial sample of the specimen. As Figure 2 shown is the size of the coaxial method sample. Its size is: inner diameter is 3.04 mm, outer diameter is 7 mm, and thickness is 2 mm.

[0076] The specific process of sample preparation is as follows:

[0077] (1) Calculate and weigh the UV-curable microwave absorbing material to be tested according to the pre-determined ratio.

[0078] (2) Pour the UV-curable microwave absorbing material into the mold.

[0079] (3) Carry out photocuring on the UV-curable microwave absorbing material in the mold.

[0080] (4) After complete curing, use a blade and fine sandpaper to level the surface of the sample to achieve the appropriate size.

[0081] Use the obtained electromagnetic parameters to further analyze the electromagnetic wave absorption performance of the composite material, and study the relationship between the loss value RL of the electromagnetic wave reflection absorbed by the single-layer flat plate with the same thickness and the frequency. Based on the electromagnetic parameters, calculate the electromagnetic loss according to the absorption screen theory.

[0082] RL(dB) = 20 log|(Z in - 1) / (Z in + 1)| (1)

[0083] Z in = Z0(μ γ / ε γ ) 1 / 2 tanh[j(2πfd / c)(μ γ ε γ ) 1 / 2 (2)

[0084] Wherein, Z in and Z0 respectively represent the normalized input impedance of the wave - absorbing material and the input impedance of free space, while μ γ and ε γ respectively represent the relative permeability and permittivity of the material, d is the thickness of the absorption layer, c represents the speed of light, and f represents the free - space frequency of the electromagnetic wave. As long as ε is large enough, the larger μ is, the better the absorption of electromagnetic waves. However, neither ε nor μ is simply the larger the better. Other influencing factors such as impedance and specific materials also need to be considered.

[0085] The specific test results are shown in Table 1 below:

[0086] Table 1 Test Results

[0087]

[0088]

[0089] It can be seen from the above table that the ink of the present invention has appropriate viscosity, uniform particle size, strong electromagnetic loss ability, wide electromagnetic absorption bandwidth, high mechanical strength, good surface flatness, low volume shrinkage rate, fast curing speed, high forming accuracy, and good printing performance. Such effects are inseparable from the specific raw material formula adopted in the present invention.

[0090] The ultraviolet - curable 3D - printed Fe₃O₄ / carbon nanotube electromagnetic - absorption ink in the embodiment of the present invention uses the Fe₃O₄ / carbon nanotube composite material as the electromagnetic - absorption agent, which can play a synergistic electromagnetic - wave dissipation role of magnetic loss and electrical loss, greatly improving the electromagnetic - wave absorption ability of the material and having a wide absorption bandwidth. Using 1,6 - hexanediol diacrylate, hyperbranched polyester acrylate resin, and acryloylmorpholine compounded as the polymer matrix material, it has a relatively fast curing speed, high forming accuracy, is not easy to deform after curing, and has good mechanical properties, and can be applied to the rapid manufacturing of electromagnetic absorbers with various shapes and high precision in military and civilian fields.

[0091] Although the present invention has been illustrated and described with reference to specific embodiments, it will be appreciated that many other changes and modifications may be made without departing from the spirit and scope of the invention. Accordingly, it is intended that all such variations and modifications that fall within the scope of the present invention be included in the appended claims.

Claims

1. A magnetite electromagnetic absorption ink for 3D printing, characterized in that: It is prepared from the following raw materials: by mass, 0.04 - 0.1 part of multi-walled carbon nanotubes, 0.05 - 0.2 part of polypyrrole, 0.1 - 0.5 part of iron oxide, 30 - 36 parts of hyperbranched polyester acrylate resin, 48 - 56 parts of acryloylmorpholine, 8 - 12 parts of 1,6 - hexanediol diacrylate, 2.5 - 5 parts of photoinitiator, 0.5 - 1.5 parts of defoamer, 0.5 - 2 parts of dispersant, and 1 - 3.5 parts of surfactant.

2. The electromagnetic absorption ink of magnetite for 3D printing according to claim 1, characterized in that: The inner diameter of the multi-walled carbon nanotubes is 5 - 15 nm, and the outer diameter is 30 - 80 nm.

3. The electromagnetic absorption ink of magnetite for 3D printing according to claim 1, wherein: The iron oxide is in powder form with a particle size of 5 - 15 nm.

4. The electromagnetic absorption ink of magnetite for 3D printing according to claim 1, characterized in that: The degree of branching of the hyperbranched polyacrylate resin is 0.5 - 0.9, and the molecular weight is 1500 - 10000.

5. The electromagnetic absorption ink of magnetite for 3D printing according to claim 1, characterized in that: The photoinitiator is 2,4,6 - trimethylbenzoyl diphenylphosphine oxide; the defoamer is a polyether silicone copolymer defoamer; the dispersant is TEGO Dispers 670 wetting dispersant; the surfactant is a polysiloxane - polyether copolymer surfactant.

6. The preparation method of the iron oxide electromagnetic absorption ink for 3D printing according to any one of claims 1 - 5 includes the following steps: Mix all raw materials, first conduct mechanical stirring, and after mixing evenly, conduct grinding and dispersion, and then conduct quality inspection, filtration, and packaging.

7. The preparation method of the magnetite electromagnetic absorption ink for 3D printing according to claim 6, characterized in that: The rate of the mechanical stirring is between 260 - 450 rpm, and the stirring time is between 25 - 40 min.

8. The preparation method of the magnetite electromagnetic absorption ink for 3D printing according to claim 6, characterized in that: Use a sand mill for grinding and dispersion. The working pressure of the diaphragm pump of the sand mill is 0.2 - 0.4 MPa, and grind repeatedly for 2 - 5 times to make the particle size of the ink finished product more uniform and the flatness better.

9. The preparation method of the magnetite electromagnetic absorption ink for 3D printing according to claim 6, wherein: The particle size after grinding is below 0.8 μm.

10. The application of the iron oxide electromagnetic absorption ink for 3D printing according to any one of claims 1 - 5 in ultraviolet - curable 3D printing.

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