PLA / TPU / PMMA / GF flexible wave-absorbing material and preparation method and application thereof

Abstract

The invention provides a PLA (polylactic acid) / TPU (thermoplastic polyurethane) / PMMA (polymethyl methacrylate) / GF (glass fiber) flexible wave-absorbing material as well as a preparation method and application thereof, and belongs to the technical field of wave absorption. The preparation method comprises the following steps: preparing graphene oxide fibers by using wet spinning, reducing the graphene oxide fibers to obtain reduced graphene oxide micro-nanofibers with dielectric loss characteristics, and preparing the PLA / TPU / PMMA / GF flexible wave-absorbing material by using a melt blending method through a twin-screw extruder. The PLA / TPU / PMMA / GF flexible wave-absorbing material is prepared by compounding PLA, TPU, PMMA and GF, the material can effectively absorb electromagnetic waves in different frequency bands, the absorption rate can be improved while the thickness of the material is reduced, and better electromagnetic wave absorption performance is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave absorbing materials, and particularly relates to a PLA / TPU / PMMA / GF flexible microwave absorbing material, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous development of technology, microwave technology plays an increasingly important role in communication, radar, aerospace and other fields. At present, the war environment is complex, and the requirements for the stealth performance and electromagnetic compatibility of weapons and equipment are increasing day by day. Traditional radar absorbing materials are difficult to meet the requirements. In addition, with the continuous development of electronic devices, the problems of electromagnetic radiation and pollution are becoming more serious. The electromagnetic wave absorption technology not only shows the application potential in the fields of stealth and electromagnetic compatibility, but also has the ability to significantly reduce electromagnetic radiation pollution. In addition, this technology also shows great application possibilities and broad development prospects in multiple fields such as energy harvesting, sensing and detection. However, in the process of microwave signal transmission and processing, how to effectively absorb and attenuate microwave energy to prevent signal leakage or interference has become an urgent problem to be solved. Traditional microwave absorbing materials such as ferrites and carbon-based materials have certain absorption properties, but may have limitations in specific frequency ranges, microwave absorption performance, cost and environmental friendliness. Therefore, the research on seeking innovative and excellent microwave absorbing materials has become a hot topic at present. Summary of the Invention

[0003] Based on the above, the purpose of the present invention is to provide a PLA / TPU / PMMA / GF flexible microwave absorbing material, a preparation method thereof, and an application thereof. The present invention first prepares graphene oxide fibers by wet spinning, and then reduces them to obtain reduced graphene oxide micro-nano fibers with dielectric loss characteristics. Then, a PLA / TPU / PMMA / GF composite linear material is prepared by a melt blending method through a twin-screw extruder.

[0004] To achieve the above purpose, the present invention provides the following technical solutions:

[0005] One of the technical solutions of the present invention is a preparation method of a PLA / TPU / PMMA / GF flexible microwave absorbing material, comprising the following steps:

[0006] Step 1. After uniformly mixing pre-reduced graphene oxide and water, perform ultrasonic emulsification to obtain a spinning dope, and then perform wet spinning on the spinning dope to obtain graphene oxide fibers;

[0007] Step 2. Use a reducing agent to react with the graphene oxide fibers to obtain reduced graphene oxide fibers;

[0008] Step 3. Calcinate the reduced graphene oxide fiber to obtain reduced graphene oxide micro-nano fiber (GF);

[0009] Step 4. Melt-blend, extrude, and pelletize PLA, TPU, and PMMA to obtain masterbatch;

[0010] Step 5. Melt-blend the masterbatch with compatibilizer, binder, and reduced graphene oxide micro-nano fiber, and extrude to obtain PLA / TPU / PMMA / GF flexible microwave absorbing material.

[0011] The second technical solution of the present invention is a PLA / TPU / PMMA / GF flexible microwave absorbing material prepared by the above preparation method.

[0012] The third technical solution of the present invention is a dielectric ring prepared by 3D printing with the above PLA / TPU / PMMA / GF flexible microwave absorbing material.

[0013] The fourth technical solution of the present invention is a honeycomb-shaped microwave absorbing component prepared by 3D printing with the above PLA / TPU / PMMA / GF flexible microwave absorbing material; the shape of the honeycomb-shaped microwave absorbing component is honeycomb-shaped, with an inner diameter of 4 mm and an outer diameter of 6.3 - 7.3 mm.

[0014] The present invention discloses the following technical effects:

[0015] By compounding PLA, TPU, PMMA, and GF, the present invention prepares a PLA / TPU / PMMA / GF flexible microwave absorbing material, which can effectively absorb electromagnetic waves in different frequency bands, improve the absorption rate while reducing the material thickness, and achieve better electromagnetic wave absorption performance. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0017] Figure 1 It is a physical diagram of the composite linear material obtained in Example 1.

[0018] Figure 2 It is a 3D composition of honeycomb-shaped structural members with different outer diameters in Example 1, where (a) is HC6.3, (b) is HC6.8, and (c) is HC7.3.

[0019] Figure 3Figures (a) and (b) are SEM images of reduced graphene oxide micro-nano fibers at different magnification factors.

[0020] Figure 4 Figure (a) is the overall morphology image, and figures (b), (c), and (d) are partial enlarged images of the surface obtained by cryo-fracturing the linear material in Example 1.

[0021] Figure 5 Schematic diagrams of the memory resilience processes of different samples, where (a) is the blank control group, (b) is Sample No. 0, (c) is Sample No. 1, (d) is Sample No. 2, (e) is Sample No. 3, (f) is Sample No. 4, and (g) is Sample No. 5.

[0022] Figure 6 Reflectivity curves of Sample No. 1 - Sample No. 5 when the thickness is 3.0 mm.

[0023] Figure 7 Reflectivity curves of three honeycomb structural members of HC 6.3, HC 6.8, and HC 7.3 in the 2 - 18 GHz frequency band.

[0024] Figure 8 Reflectivity curves of three honeycomb structural members of HC 6.3, HC 6.8, and HC 7.3 in the 26.5 - 40 GHz frequency band. Detailed implementation manners

[0025] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0026] It should be understood that the terms used in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0027] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0028] Without departing from the scope or spirit of the present invention, various modifications and variations can be made to the specific embodiments of the specification of the present invention, which will be apparent to those skilled in the art. Other embodiments obtained from the specification of the present invention will be apparent to those skilled in the art. The specification and examples of the present invention are merely exemplary.

[0029] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0030] The first aspect of the present invention provides a preparation method of a PLA / TPU / PMMA / GF flexible microwave absorbing material, comprising the following steps:

[0031] Step 1. After uniformly mixing pre-reduced graphene oxide and water, ultrasonic emulsification is carried out to obtain a spinning dope, and then the spinning dope is subjected to wet spinning to obtain graphene oxide fibers.

[0032] Step 2. A reduction reaction is carried out between a reducing agent and the graphene oxide fibers to obtain reduced graphene oxide fibers.

[0033] Step 3. The reduced graphene oxide fibers are calcined to obtain reduced graphene oxide micro-nano fibers (GF).

[0034] Step 4. PLA, TPU and PMMA are melt-blended, extruded and pelletized to obtain master batches.

[0035] Step 5. The master batches are melt-blended with a compatibilizer, an adhesive and reduced graphene oxide micro-nano fibers and extruded to obtain a PLA / TPU / PMMA / GF flexible microwave absorbing material.

[0036] In some embodiments of the present invention, the mass ratio of the pre-reduced graphene oxide to water is 1:1000 - 1:25 (more preferably 1:25 - 100, 1:25 - 40 or 1:40); the preparation method of the pre-reduced graphene oxide is: reacting H2O2 and graphene oxide in water at 60 - 100 °C for 0.5 - 4 h. Pre-reduction can promote the formation of graphene fibers and extend the fiber length.

[0037] In some embodiments of the present invention, when carrying out the wet spinning, the extrusion speed is 0.01 - 1 m / s; the wet spinning uses a CaCl2 solution with a mass fraction of 0.5% - 30% as a coagulation bath; the temperature of the coagulation bath is 20 - 60 °C.

[0038] In some embodiments of the present invention, the reducing agent is hydroiodic acid; the parameters of the reduction reaction are set as follows: reacting in a water bath at 60 - 100°C for 2 - 24 h (more preferably, reacting in a water bath at 60°C for 5 h). The wave-absorbing intensity of the fiber after reduction treatment is higher and the wave-absorbing frequency band is wider.

[0039] The present invention does not make special limitations on the dosage of hydroiodic acid, and the dosage of hydroiodic acid can completely submerge the graphene oxide fiber.

[0040] In some embodiments of the present invention, after the reduction reaction, the steps of washing and drying are further included.

[0041] In some embodiments of the present invention, the calcination temperature is 200 - 1000°C (more preferably 200 - 500°C, 200 - 300°C or 200°C), the heating rate and the cooling rate are both 0.5 - 10°C / min (more preferably 1 - 5°C / min, 2 - 3°C / min or 2°C / min), and the constant temperature time is 0.1 - 2 h (more preferably 0.5 - 1.5 h, 1 - 1.5 h or 1 h).

[0042] In some embodiments of the present invention, the mass ratio of PLA, TPU and PMMA is 8:1:1 - 5:3:2 (more preferably 8:1:1).

[0043] In some embodiments of the present invention, the melt blending and extrusion of PLA, TPU and PMMA are carried out using a twin-screw extruder. The temperatures of each zone of the twin-screw extruder are as follows: zone 1 is 175°C, zone 2 is 183°C, zone 3 is 190°C, zone 4 is 185°C, and the screw speed is 30.6 Hz. During the extrusion process, uniform winding is carried out by a winder at a certain winding speed to ensure the uniform thickness of the linear material and facilitate subsequent processing.

[0044] In some embodiments of the present invention, the compatibilizer is maleic anhydride; the binder is KH570 or KH550; the mass-volume ratio of the masterbatch, the compatibilizer and the binder is 50 g:1 g:1 mL; the reduced graphene oxide micro-nano fiber accounts for 0.2 wt% - 1.0 wt% of the mass of the masterbatch (more preferably 0.6 wt% - 1.0 wt% or 0.8 wt%).

[0045] In some embodiments of the present invention, the parameters for melt blending and extrusion of the masterbatch, the compatibilizer, the binder and the reduced graphene oxide micro-nano fiber are the same as those for melt blending and extrusion of PLA, TPU and PMMA.

[0046] The second aspect of the present invention provides a PLA / TPU / PMMA / GF flexible wave-absorbing material prepared by the above preparation method.

[0047] In the third aspect of the present invention, a dielectric ring is provided, which is prepared by 3D printing with the above PLA / TPU / PMMA / GF flexible microwave absorbing material.

[0048] In some embodiments of the present invention, when 3D printing the PLA / TPU / PMMA / GF flexible microwave absorbing material, the 3D printing parameters are set as follows: the printing temperature is 190 - 240 °C, the printing bed temperature is 60 - 80 °C, and the printing speed is 60 - 120 mm / s.

[0049] In the fourth aspect of the present invention, a honeycomb-shaped microwave absorbing member is provided, which is prepared by 3D printing with the above PLA / TPU / PMMA / GF flexible microwave absorbing material; the honeycomb-shaped microwave absorbing member has a honeycomb shape, an inner diameter of 4 mm, and an outer diameter of 6.3 - 7.3 mm.

[0050] In some embodiments of the present invention, the honeycomb-shaped microwave absorbing member has a honeycomb shape, an inner diameter of 4 mm, and an outer diameter of 6.3 mm, 6.8 mm, or 7.3 mm.

[0051] In some embodiments of the present invention, the 3D printing parameters for the PLA / TPU / PMMA / GF flexible microwave absorbing material are set as follows: the printing temperature is 190 °C, the printing bed temperature is 80 °C, and the printing speed is 90 mm / s.

[0052] The technical solutions of the present invention are conventional solutions in the art unless otherwise specified. The reagents or raw materials used are commercially available or publicly disclosed unless otherwise specified.

[0053] To better understand the present invention, the content of the present invention will be further clarified below with reference to embodiments, but the content of the present invention is not limited to the following embodiments.

[0054] Example 1

[0055] 1. A preparation method of a PLA / TPU / PMMA / GF flexible microwave absorbing material, the steps are as follows:

[0056] Step 1. Take 30 ml of 30% H2O2 aqueous solution and 150 mL of 3 mg / ml GO aqueous solution, react in an aqueous solution at 100 °C for 2 h to obtain pre-reduced graphene oxide, then mix the pre-reduced graphene oxide and water in a mass ratio of 1:40 evenly, emulsify for 10 min, and then remove bubbles by ultrasonic oscillation to obtain a spinning dope. Then, the spinning dope is wet-spun in a 20 wt% CaCl2 solution at room temperature to obtain graphene oxide fibers.

[0057] Step 2. Immerse the graphene oxide fiber completely in hydroiodic acid, and carry out a reduction reaction in a water bath at 60 °C for 5 h. After that, wash it with water and dry it to obtain reduced graphene oxide fiber;

[0058] Step 3. Heat it to 500 °C at a rate of 2 °C / min and keep it at a constant temperature for 1 h, then calcine the reduced graphene oxide fiber, and cool it at a rate of 2 °C / min to obtain reduced graphene oxide micro-nano fiber;

[0059] Step 4. Melt-blend, extrude and pelletize PLA, TPU and PMMA with a mass ratio of 8:1:1 through a twin-screw extruder to obtain masterbatch; the temperatures of each zone of the twin-screw extruder are: zone 1 at 175 °C, zone 2 at 183 °C, zone 3 at 190 °C, zone 4 at 185 °C, and the screw speed is: 30.6 Hz;

[0060] Step 5. Melt-blend 50 g of masterbatch, 1 g of maleic anhydride, 1 mL of KH570 and reduced graphene oxide micro-nano fiber through a twin-screw extruder, and extrude to obtain composite linear materials with different graphene micro-nano fiber addition amounts (i.e., PLA / TPU / PMMA / GF flexible microwave absorption materials); among them, the temperatures of each zone of the twin-screw extruder are: zone 1 at 175 °C, zone 2 at 183 °C, zone 3 at 190 °C, zone 4 at 185 °C, and the screw speed is: 30.6 Hz; the reduced graphene oxide micro-nano fibers are 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, 1.0 wt% of the masterbatch respectively. According to the reduced graphene oxide micro-nano fibers being 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, 1.0 wt% of the masterbatch respectively, name the obtained PLA / TPU / PMMA / GF flexible microwave absorption materials as sample No. 1, sample No. 2, sample No. 3, sample No. 4, and sample No. 5 respectively. When the addition amount of the reduced graphene oxide micro-nano fiber is 0, the obtained PLA / TPU / PMMA / GF flexible microwave absorption material is used as a blank control group.

[0061] Perform 3D printing on sample No. 5, set the printing temperature to 190 °C, the printing bed temperature to 80 °C, and the printing speed to 90 mm / s. As Figure 2 , design three honeycomb structure components with the same inner diameter and different outer diameters for 3D composition. The inner diameter is 4 mm, and the outer diameters are 6.3 mm, 6.8 mm, and 7.3 mm respectively, and name them HC6.3, HC6.8, and HC7.3 respectively.

[0062] 2. Structural Characterization and Property Testing

[0063] 2.1 Scanning Electron Microscope Test (SEM)

[0064] Figure 3For the electron microscope photos of reduced graphene oxide micro-nano fibers at different magnifications, it can be clearly observed that their fibrous structure is a wrinkled graphene micro-nano fiber with a long diameter.

[0065] Figure 4 It is the electron microscope photo of the surface obtained after the linear material of Sample No. 4 was quenched and broken with liquid nitrogen. It can be observed that TPU and PMMA are evenly distributed in PLA and do not exist independently, indicating that the mixture is relatively uniform. Figure 4 It can be seen from (c) in the figure that compared with the inside, the outside of the linear material is more evenly mixed, the structure is more regular, and the surface is smoother. Figure 4 In the magnified picture (d) in the figure, it can be seen that the graphene fibers are wrapped into balls, which may be because the TPU in the composite material melts faster and wraps it inside.

[0066] 2.2 Memory rebound analysis

[0067] In order to exclude the influence of KH570 and maleic anhydride on the recovery rate of the linear material, the present invention prepared Sample No. 0 by adding the same mass of KH570 and maleic anhydride. Figure 5 Analysis shows that the recovery rate of the blank control group is 41%, the recovery rate of Sample No. 0 is 41%, the recovery rate of Sample No. 1 is 70%, the recovery rate of Sample No. 2 is 69%, the recovery rate of Sample No. 3 is 64%, the recovery rate of Sample No. 4 is 70%, and the recovery rate of Sample No. 5 is 75%. It can be seen that the recovery rates of the blank control group and Sample No. 0 are the same, indicating that the addition of KH570 and maleic anhydride has no effect on the memory rebound performance of the material. For other groups, although the recovery rates are slightly deviated, the overall trend is that the recovery rate increases with the increase of the content of graphene micro-nano fibers.

[0068] 2.3 Microwave absorption performance test

[0069] In order to compare the microwave absorption performance of Sample No. 1 to Sample No. 5, the microwave absorption effects of the five materials were selected at the same thickness of 3.0 mm. Figure 6(In the figure, 1#, 2#, 3#, 4#, and 5# represent Sample No. 1, Sample No. 2, Sample No. 3, Sample No. 4, and Sample No. 5 respectively). It can be seen that Sample No. 1 can have an effective absorption bandwidth of 0.84 GHz, and the effective absorption range is (10.67 - 11.51 GHz). At a frequency of 11.1 GHz, the reflection loss can reach -11.33 dB; Sample No. 2 can have an effective absorption bandwidth of 2.22 GHz, and the effective absorption range is (12.99 - 15.21 GHz). At a frequency of 14.2 GHz, the reflection loss can reach -19.9 dB; Sample No. 3 can reach an effective absorption bandwidth of 2.16 GHz, and the effective absorption ranges are (11.41 - 12.03 GHz), (12.22 - 12.99 GHz), (16.31 - 17.01 GHz). At a frequency of 11.7 GHz, the reflection loss can reach -27.18 dB; Sample No. 4 can reach an effective absorption bandwidth of 4.97 GHz, and the effective absorption ranges are (10.77 - 13.71 GHz), (15 - 16.24 GHz), (16.48 - 17.27 GHz). At a frequency of 11.85 GHz, the reflection loss can reach -35.31 dB; Sample No. 5 can reach an effective absorption bandwidth of 3.73 GHz, and the effective absorption ranges are (12.54 - 12.87 GHz), (13.01 - 14.35 GHz), (15.41 - 17.22 GHz). At a frequency of 13.56 GHz, the reflection loss can reach -45.35 dB. Generally speaking, Sample No. 4 has the best wave absorption performance.

[0070] It can be seen from Figure 7 that samples HC 6.3, HC 6.8, and HC 7.3 also have good absorption in the range of 2 - 18 GHz. Among them, HC6.8 has the widest effective absorption bandwidth, which is 9.92 GHz, and the effective absorption range is (3.01 - 6.47 GHz), (11.54 - 18 GHz). It can be seen from Figure 8 that honeycomb structural members with three outer diameter side lengths achieve total absorption in the range of 26.5 - 40 GHz. After electromagnetic waves enter the structural members, they are coherently superimposed. Different wavelengths may be sensitive to a certain structure. For example, when the outer diameter side length is 6.8 mm, the honeycomb structural member will enhance its refraction and reflection effects.

[0071] In summary, through the SEM test analysis of the blended wire, it can be known that the PLA / TPU / PMMA / GF blended composite wire has good compatibility; through the wave absorption performance analysis, it can be known that when the addition amount of reduced graphene oxide micro-nano fibers is 0.8 wt%, the wave absorption effect is the best, the frequency bandwidth is the widest at 4.97 GHz, and the minimum reflection loss is the smallest among all addition amounts, which is -35.31 dB.

[0072] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a PLA / TPU / PMMA / GF flexible microwave absorbing material, characterized in that, It includes the following steps: Step 1. After uniformly mixing pre-reduced graphene oxide and water, perform ultrasonic emulsification to obtain a spinning dope. Then, perform wet spinning on the spinning dope to obtain graphene oxide fibers; Step 2. Use a reducing agent to react with the graphene oxide fibers to obtain reduced graphene oxide fibers; Step 3. Calcinate the reduced graphene oxide fibers to obtain reduced graphene oxide micro-nano fibers; Step 4. Melt-blend, extrude, and pelletize PLA, TPU, and PMMA to obtain masterbatch; Step 5. Melt-blend the masterbatch with a compatibilizer, an adhesive, and the reduced graphene oxide micro-nano fibers, and extrude to obtain a PLA / TPU / PMMA / GF flexible microwave absorbing material.

2. The preparation method of the PLA / TPU / PMMA / GF flexible microwave absorbing material according to claim 1, wherein, The mass ratio of the pre-reduced graphene oxide to water is 1:1000 to 1:25; the preparation method of the pre-reduced graphene oxide is: react H2O2 and graphene oxide in water at 60 - 100 °C for 0.5 - 4 h.

3. The preparation method of the PLA / TPU / PMMA / GF flexible microwave absorbing material according to claim 1, wherein, The reducing agent is hydroiodic acid; the parameter settings for the reduction reaction are: react in a water bath at 60 - 100 °C for 2 - 24 h.

4. The preparation method of the PLA / TPU / PMMA / GF flexible microwave absorbing material according to claim 1, characterized in that, The calcination temperature is 200 °C to 1000 °C, the heating rate and the cooling rate are both 0.5 - 10 °C / min, and the isothermal time is 0.5 - 2 h.

5. The preparation method of the PLA / TPU / PMMA / GF flexible microwave absorbing material according to claim 1, wherein, The mass ratio of PLA, TPU, and PMMA is 8:1:1 to 5:3:

2.

6. The preparation method of the PLA / TPU / PMMA / GF flexible microwave absorbing material according to claim 1, characterized in that, The compatibilizer is maleic anhydride; the adhesive is KH570 or KH560; the mass-volume ratio of the masterbatch to the compatibilizer and the adhesive is 50 g:1 g:1 mL; the reduced graphene oxide micro-nano fibers account for 0.2 wt% - 1.0 wt% of the mass of the masterbatch.

7. A PLA / TPU / PMMA / GF flexible microwave absorbing material prepared by the preparation method according to any one of claims 1 - 6.

8. A dielectric ring, characterized in that, It is prepared by 3D printing the PLA / TPU / PMMA / GF flexible microwave absorbing material according to claim 7.

9. A honeycomb-shaped wave-absorbing member, characterized in that, It is prepared by 3D printing the PLA / TPU / PMMA / GF flexible microwave absorbing material according to claim 7; the shape of the honeycomb-shaped microwave absorbing component is honeycomb-shaped, the inner diameter is 4 mm, and the outer diameter is 6.3 - 7.3 mm.

Images