Microporous nano foaming material with micro-nano pore structure as well as preparation method and application of microporous nano foaming material

Abstract

The invention relates to a microporous nano foam material with a micro-nano pore structure as well as a preparation method and application thereof, and belongs to the technical field of foam materials. According to the invention, a micro-cross-linked network is taken as a core, and the problem of insufficient melt strength caused by disentanglement of molecular chains in a high-temperature processing and forming process of the hydroxyl-terminated polymer is solved through a multi-network (a cross-linked structure, a chain extension structure and a branched chain structure) structure. The preparation method comprises the following steps: firstly, preparing a high-performance microporous nano foaming material with a micro-nano pore structure by using a high-pressure foaming technology and then carrying out supercritical forming by using a supercritical foaming technology, so that the problem that all special engineering plastics containing terminal hydroxyl groups are difficult to foam due to rigid chain structures can be solved, and finally, high-frequency high-speed high-performance antennas which are used for 5G and 6G are obtained.

Description

Technical Field

[0001] This invention relates to a microporous nanofoamed material with a micro-nano pore structure, its preparation method and application, belonging to the field of foamed material technology. Background Technology

[0002] To meet the requirements of high-speed transmission and low latency, 5G will utilize sub-6GHz and millimeter waves for signal transmission, achieving downlink data rates exceeding 10Gbit / s. 5G improves spectrum utilization efficiency by integrating 24-100GHz spectrum resources. The selection of next-generation materials for wireless communication requires large-scale innovation to meet new spectrum communication needs, meaning the need to adapt to higher carrier frequencies and larger communication bandwidths, as well as higher efficiency and linearity. The demand for metamaterials and semiconductors in related fields will continue to grow. This also places higher demands on communication materials, especially in terms of dielectric properties. Antennas are the core electromagnetic wave converters in communication systems, undertaking the core tasks of converting high-frequency current in circuits into free-space electromagnetic waves (transmit mode) and vice versa (receive mode). Antennas are mostly used in outdoor environments; in the future, with technological advancements, humans will utilize antennas in more harsh environments such as space and deserts. Therefore, this places even higher demands on antenna materials. Low dielectric constant and loss: meet the signal transmission requirements of current 5G and even future 6G terahertz frequencies (0.1~10THz); weather resistance: satellite communication antennas need to withstand the harsh environment of space, marine or nuclear industrial environments, requiring corrosion resistance and radiation resistance; excellent mechanical properties: able to resist external forces (such as strong winds) and maintain long-term stability.

[0003] Common antenna materials include metals, ceramics, and polymers. Metals offer advantages such as high conductivity, good mechanical properties, and ease of processing; however, they suffer from significant electromagnetic wave loss, leading to reduced radiation efficiency. Furthermore, their high density is causing them to be phased out by the current trend towards lightweight and miniaturized antennas. Ceramic materials possess high hardness, wear resistance, and are not easily damaged by mechanical forces. They also exhibit good weather resistance, resisting harsh environments such as oxidation, corrosion, and high temperatures; however, their dielectric constant (Dk) is relatively low. k Higher (D of transparent ceramics) k≈7), leading to signal and material impedance mismatch and reduced transmission efficiency. Typical ceramic substrates are usually manufactured at high temperatures of 850-1300℃, which requires high-precision molding dies and controlled atmosphere sintering furnaces to control the structure and prevent high-temperature oxidation from causing dielectric property degradation. Polymer materials have many advantages such as easy structure control, easy processing, and excellent strength and dielectric properties. Commonly used polymer materials for antennas include polypropylene (PP), polyethersulfone (PES), polyimide (PI), and liquid crystal polymer (LCP). PP has ultra-low dielectric properties (dielectric constant of 2.1 and dielectric loss of 0.00012 at 3GHz), but as a general-purpose plastic, its strength, heat resistance, and flame retardancy are poor, which cannot meet the requirements of antenna use and needs to be modified. While PES, PI, and LCP have lower dielectric properties than PP, as special engineering plastics, they possess numerous advantages such as high strength, good heat resistance, self-flame retardancy, and chemical resistance. By introducing air through supercritical foaming molding technology, microporous foam materials with microporous structures can be constructed. While maintaining the high performance of special materials, their dielectric properties can be significantly reduced, and the materials can also be given many advantages such as lightweight, thermal insulation, vibration reduction, noise reduction, and environmental friendliness. Therefore, they have become the preferred materials for 5G antennas.

[0004] However, the rigid molecular chain structure of aromatic rings, which endows special materials with many advantages, profoundly restricts the implementation of supercritical foaming processes. This rigid chain structure leads to extreme contradictions in melt strength across temperature gradients through multiple mechanisms: in the low-temperature processing range, the intermolecular forces formed by the stacking of aromatic rings and the free volume reduction effect caused by the restricted chain segment movement significantly increase melt viscosity, resulting in a significant decrease in the diffusion coefficient of supercritical fluids in the melt. At the same time, the viscoelastic resistance to be overcome for cell growth far exceeds the expansion driving force provided by the melt surface tension, resulting in cell diameters being limited to the submicron level and sparsely distributed. When the temperature rises to near the material's thermal decomposition threshold, the rigid chains undergo local conformational dissociation due to thermal energy input, causing molecular chain deentanglement, significantly reducing melt strength, and inducing cell merging, collapse, and open-cell structures. The inherent contradiction of rigid molecular chains makes it impossible to effectively introduce more air into special engineering plastics, restricting their use as high-performance antennas in 5G and 6G. Therefore, it is urgent to solve the difficult foaming problem caused by the rigid chain structure of special engineering plastics containing terminal hydroxyl groups. Summary of the Invention

[0005] This invention uses a micro-crosslinked network as its core, employing a multi-network structure (crosslinked structure, chain-extended structure, and branched structure) to improve the melt strength of polymers containing terminal hydroxyl groups during high-temperature processing, which is hampered by molecular chain deentanglement. Then, a supercritical foaming process is used for supercritical molding to prepare a high-performance microporous nanofoamed material with a micro-nano pore structure. This solves the foaming problem inherent in the rigid chain structure of all special engineering plastics containing terminal hydroxyl groups, ultimately yielding high-frequency, high-speed, and high-performance antennas suitable for 5G and 6G applications.

[0006] Specifically, the present invention provides a microporous nanofoamed material with a micro-nano pore structure, wherein the microporous nanofoamed material comprises 80-95 wt% of a terminal hydroxyl polymer, 0.2-10 wt% of a dendritic polyepoxy compound, 2-15 wt% of a polyhydroxy compound co-crosslinking agent, and 0.5-2 wt% of a ZnO catalyst.

[0007] Preferably, the dendritic polyepoxy compound is selected from one or more of 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, glycidyl ether, pentaerythritol glycidyl ether, glycidyl etheroxypropyl cage polysilsesquioxane, and glycidyl etheroxypropyl cyclotetrasiloxane.

[0008] Preferably, the polyhydroxy compound co-crosslinking agent is selected from one or more of 1,3,5-benzenetriethanol, pentaerythritol, epiinositol, tris(hydroxymethyl)aminomethane (Tris base), di(2-hydroxyethyl)iminotris(hydroxymethyl)methane (BIS-TRIS), and D-sorbitol.

[0009] Preferably, the hydroxyl-terminated polymer is selected from polyethersulfone, polyimide, and liquid crystal polymer.

[0010] Preferably, the pore size of the microporous nanofoamed material is less than 10 μm.

[0011] The present invention also provides a method for preparing the above-mentioned microporous nanofoamed material with micro-nano pore structure, which includes the following steps:

[0012] (1) A hydroxyl-terminated polymer, a dendritic polyepoxy compound, a polyhydroxy compound crosslinking agent and a ZnO catalyst are mixed in proportion and melted at high temperature in an air-isolated environment to form a nanocomposite material, and then shaped into a preform.

[0013] (2) The preform is subjected to supercritical foaming to obtain microporous nano foam material.

[0014] Preferably, the hydroxyl-terminated polymer needs to be vacuum dried before step (1) at a temperature of 100-150°C for 2-10 hours.

[0015] Preferably, in step (1), the temperature of the high-temperature melting is 300-400℃, and a shear field needs to be applied during the melting process.

[0016] Preferably, in step (2), the supercritical foaming agent used is CO2, the foaming temperature is 200-300℃, the foaming pressure is 10-20 MPa, and the foaming time is 0.5-5 h.

[0017] The microporous nanofoamed material with micro-nano pore structure prepared by this invention can be used in terahertz antennas.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] This invention relates to a microporous nanofoamed material, which successfully prepares a high-performance material with a micro- and nanoporous structure by constructing a micro-crosslinked network structure and employing a supercritical CO2 foaming process. This material not only significantly reduces the dielectric constant and dielectric loss, meeting the high-frequency and high-speed material requirements of 5G and even future 6G communications, but also possesses multiple advantages such as lightweighting, thermal insulation, vibration reduction, noise reduction, and environmental friendliness due to the introduction of air. Its pore size is less than 10 μm and is uniformly distributed, further enhancing the material's overall performance and providing a new approach for the development of high-performance communication materials.

[0020] Secondly, the microporous nanofoamed material of this invention can be applied to antenna manufacturing, significantly improving antenna performance and application range. The material's excellent dielectric properties effectively reduce energy loss during signal transmission, improving antenna radiation efficiency and gain, resulting in superior performance in high-speed data transmission and complex electromagnetic environments. Simultaneously, its lightweight, weather-resistant, and excellent mechanical properties enable the antenna to operate stably for extended periods in harsh outdoor environments (such as space and deserts), resisting the corrosive effects of harsh environments on antenna performance. This provides a reliable material foundation for the application of 5G and future 6G communication technologies in fields such as the Internet of Things, intelligent transportation, and public safety services. Attached Figure Description

[0021] Figure 1 Example 1 describes the construction principle of the PES crosslinking network.

[0022] Figure 2 (a) Infrared spectra of PES and its composites; (b) Analysis of the Ar-OR peak variation of PES and its composites at 1240 wavenumber;

[0023] Figure 3(a) DSC curves of PES pure sample, 5% POSS, and samples 1#, 2#, and 7#; (b) DSC curves of PES pure sample, 5% POSS, and samples 2#, 3#, 4#, 5#, and 6#; (c) DSC curves of PES pure sample, 5% POSS, and samples 1#, 8#, 9#, 10#, and 11#.

[0024] Figure 4 : Energy storage modulus versus angular frequency curves (a), (b), (c); Loss modulus versus angular frequency curves (d), (e), (f); Energy storage modulus versus loss modulus curves (g), (h), (i);

[0025] Figure 5 Stress-strain curves of PES and its nanocomposites (a); Elongation at break of PES and its nanocomposites (b); Maximum tensile stress of PES and its nanocomposites (c).

[0026] Figure 6 SEM micrographs of different components at the optimal foaming temperature, (a)-(i) are pure PES sample, 5% POSS, sample 1#, 2#, 3#, 5#, 6#, 7#, 8#, 9#, 10#, and 11#, respectively;

[0027] Figure 7 SEM images of sample #11 after foaming at foaming temperatures of 243℃(a), 244℃(b), 245℃(c), and 247℃(d);

[0028] Figure 8 The foaming ratio of pure PES samples and all PES composite foam materials at different temperatures (a); the foaming ratio of PES composite foam materials with different PES contents at a (PES+THPE):POSS molar ratio of 1:1 (b); the foaming ratio of PES composite foam materials with different (PES+THPE):POSS molar ratios at the same PES content (c); the foaming ratio of PES composite materials with different (PES+THPE):POSS molar ratios as the PES content increases (d).

[0029] Figure 9 Pore ​​diameter at the optimal foaming ratio for different components (mean value after statistical analysis of 300 cells) (a); Pore diameter of sample #11 at different foaming temperatures (b);

[0030] Figure 10 Cell density at the optimal expansion ratio for different components (a); Cell density of sample #11 at different foaming temperatures (b); Figure 11Dielectric constants of PES / POSS composites with different components (a); dielectric loss of PES / POSS composites with different components (b); dielectric constants of PES / POSS composite foams with different components (c); dielectric loss of PES / POSS composite foams with different components (d).

[0031] Figure 12 Gain pattern (ah) of 5% POSS, 2#, 5#, 6#, 8#, 9#, 10# and 11# foamed materials with optimal expansion ratio;

[0032] Figure 13 Gain (a) and efficiency (b) of 5% POSS, 2#, 5#, 6#, 8#, 9#, 10# and 11# foamed materials with optimal expansion ratios. Detailed Implementation

[0033] Example 1

[0034] In this embodiment, hydroxyl-terminated PES was used as the hydroxyl-terminated polymer. First, PES particles were dried in a vacuum oven at 120°C for 6 hours. Then, the dried particles, 1,1,1-tris(4-hydroxyphenyl)ethane (THPE) co-crosslinking agent, glycidyl etheroxypropyl cage-like polysilsesquioxane (POSS), and zinc oxide (ZnO) catalyst were reactantly melt-mixed in a high-temperature torque rheometer at 350°C under a shear field in an air-isolated environment to obtain 11 groups of PES nanocomposites. The PES content, THPE co-crosslinking agent content, POSS content, PES+THPE:POSS molar ratio, and ZnO content are shown in Table 1.

[0035] PES nanocomposite materials were pressed into sheets at 360°C using a high-temperature vacuum press. The sheets were then placed in a molding foaming kettle and, using supercritical CO2 as the physical foaming agent, 1 mm thick PES nanocomposite materials were swelled for 2 hours under different temperature and the same pressure (18 MPa) conditions. After depressurization and foaming, PES nanocomposite foamed materials were obtained.

[0036] Comparative Example 1

[0037] The difference between Comparative Example 1 and Example 1 is that pure hydroxyl-terminated PES was used, without the addition of 1,1,1-tris(4-hydroxyphenyl)ethane (THPE) co-crosslinking agent, glycidyl etheroxypropyl cage polysilsesquioxane (POSS), and zinc oxide (ZnO) catalyst.

[0038] Comparative Example 2

[0039] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 is a mixture of 95.wt% terminal hydroxyl PES and 5.wt% POSS, and does not contain THPE and ZnO.

[0040] Table 1. Components of the PES / POSS nanocomposites used in the examples and comparative examples.

[0041]

[0042]

[0043] Characterization

[0044] (1) Fourier transform infrared (FTIR) tests were performed on 13 groups of PES nanocomposites prepared in Example 1 and Comparative Example 1, as well as pure PES. The crosslinking network density was obtained by testing the gel content. The glass transition temperature (Tg) was obtained by performing differential scanning calorimetry (DSC).

[0045] (2) Rotational rheological test, tensile property test and vector network analysis test were performed on the plate to obtain its viscoelastic properties, tensile strength and dielectric properties.

[0046] (3) After the PES nanocomposite foam material was placed in room temperature air for 72 hours, SEM and density tests were performed to obtain the pore structure information of the PES nanocomposite material; the dielectric properties of the material were tested at 10 GHz using a vector network analyzer to obtain its dielectric constant and dielectric loss; the antenna performance of the material was simulated using CST Studio Suite to obtain its gain and efficiency and evaluate its antenna performance.

[0047] Characterization results

[0048] like Figure 1 As shown, in Example 1, THPE with trifunctional phenolic hydroxyl groups was used as a crosslinking aid, and a crosslinking network was constructed using POSS as the crosslinking point. The phenolic hydroxyl groups of THPE and PES reacted with the eight epoxy groups on POSS to construct the crosslinking network. Figure 2 The reflectance infrared spectra of PES, PES+5%POSS, and sample #3 were tested respectively, and the results were obtained by analyzing the infrared spectra ( Figure 2 ) 1240cm -1 Changes in the characteristic ether bond peak (Ar-OR) at the IR position can qualitatively indicate changes in the degree of reaction. The three sets of infrared curves were baseline-calibrated and normalized, with normalization at 1319 cm⁻¹. -1 Using the sulfone S=O asymmetric stretching vibration as the reference peak, the peak height and peak area of ​​each curve at the Ar-OR characteristic peak were quantitatively obtained after processing, as shown in Table 2. With the addition of POSS and THPE, the peak area showed an increasing trend, indicating that during the reaction melt blending process, the hydroxyl group reacted with the epoxy to generate new ether bonds.

[0049] Table 2. Variation of peak intensity and peak area of ​​Ar-OR peak.

[0050]

[0051] Table 3 shows the gel content of PES nanocomposites with different crosslinking network densities. The tested ratio was (PES+THPE):POSS = 1:3. The test results showed that the gel content decreased with the decrease of THPE and POSS content, which is consistent with the reaction principle.

[0052] Table 3. Gel content of different PES nanocomposites

[0053]

[0054] The thermal properties of PES nanocomposites are influenced by both component content and cross-linking network. Figure 3 (a) It can be seen that under the condition of a fixed (PES+THPE):POSS molar ratio of 1:1, reducing the PES content will lead to a decrease in system T. g A significant decrease. This is because PES has a high molecular chain rigidity and strong intermolecular forces, which are essential for maintaining the system's high T. g The core component. When the PES content decreases, the proportion of rigid segments in the system decreases, directly leading to T g The temperature decreases. While excessive THPE and POSS increase the crosslinking network density, THPE has poor heat resistance (melting point 247℃) and, as a small molecule, may act as a plasticizer. Therefore, as the PES content decreases, the Tg of the PES / POSS / THPE ratio decreases. g The trend is downward. While keeping the PES content constant, by adjusting the molar ratio of (PES+THPE):POSS, PES / POSS / THPE composites with different heat resistances can be obtained, such as... Figure 3 As shown in (c). When the molar ratio of (PES+THPE):POSS is 1:3, the crosslinking density and molecular chain rigidity of the system reach a relatively good balance, and the material's T... g It has a maximum temperature of 222.1℃. Finally, by controlling the rigid chain, small molecule ratio and crosslinking network density, a PES nanocomposite material with better heat resistance was obtained.

[0055] Rotational rheological tests were performed on PES and its nanocomposites, and the results are as follows: Figure 4 As shown. PES pure sample and 5% POSS sample in... Figure 4 The low-frequency regions within curves (a)-(c) did not exhibit plateau regions, while curves 1-11# all exhibited certain plateau regions. Furthermore, with the increase of THPE and POSS content, the plateau regions in the low-frequency regions became more pronounced, indicating that the surface cross-linked network structure was successfully constructed. Figure 4(c) The data shows that as the molar content of THPE and POSS decreases, the plateau region becomes less distinct and shifts to lower frequencies, indicating that the material has a low internal crosslinking density and a micro-crosslinking network structure. The micro-crosslinking network provides PES elasticity without excessively restricting the movement of molecular chains, which is very beneficial for air introduction and the construction of high-transparency antennas. Figure 4 The Han diagrams for (g), (h), and (i) more clearly show the changes in the crosslinking network density of the PES composite material as the molar content of the three components changes.

[0056] Room temperature tensile tests were performed on pure PES samples, 5% POSS samples, samples #5, #6, and #8-11, respectively, and stress-strain curves of the samples were obtained, as shown below. Figure 5 As shown, sample #11 exhibits the best tensile stress (86.5 MPa) and a relatively good elongation at break (slightly lower than the pure sample). The tensile properties of the remaining samples are poor, especially the elongation at break, which is due to the reduced PES content. The increased amount of THPE, a ternary functional crosslinking agent, significantly increases the crosslinking point density of the system, forming a dense three-dimensional crosslinked network. Although this structure improves rigidity (elastic modulus E increases) by restricting molecular chain slip, excessive crosslinking hinders the movement of molecular chain segments, reducing energy dissipation capacity and macroscopically manifesting as a sharp decrease in toughness. This is consistent with the performance degradation caused by excessive crosslinking agents in traditional rubber vulcanization systems; that is, after the crosslinking density exceeds the critical threshold, the material transitions from ductile fracture to brittle fracture. The stress-strain curve of the material exhibits a hard and brittle characteristic. High crosslinking density leads to increased polymer melt viscosity and restricted CO2 diffusion channels, hindering cell nucleation and growth during subsequent supercritical fluid foaming, potentially causing cell collapse or uneven pore size distribution, which is detrimental to subsequent foaming and molding.

[0057] Air has a dielectric constant of 1, and its dielectric loss is close to zero in dry conditions, allowing electromagnetic waves to propagate at near-light speed without loss in dry air. Therefore, introducing air into a polymer matrix can significantly reduce the material's dielectric constant and loss, while also providing better impedance matching with the air medium. Supercritical CO2 autoclaving molding, by introducing scCO2 into the polymer at a suitable temperature, can produce PES supercritical microporous composite foam materials. Figure 6 SEM images of the pore structure of each component with the optimal foaming ratio are shown. Figure 6SEM images show that (a), (b), (g), (i), (k), and (l) all exhibit good cell morphology, with uniform pore size and low porosity. (a) is a pure PES sample, (b) is a 5% POSS sample, and (g), (i), (k), and (l) are composite materials with different PES contents at a fixed (PES+THPE):POSS molar ratio of 1:3. This indicates that a (PES+THPE):POSS molar ratio of 1:3 is optimal, resulting in a more uniform cross-linked network structure and better cell structure. Systematic foaming molding tests were conducted on sample #11, yielding a series of PES supercritical microporous composite foam materials with different temperatures, the same pressure (18 MPa), and swelling time (2 hours). Figure 7 As shown. Pore structure parameters of all component foam materials. Figure 8 , Figure 9 and Figure 10 As shown.

[0058] Figure 8 (a) A trend graph showing the foaming ratio of all component samples; (b) A trend graph showing the foaming ratio of composite materials with different PES contents when the (PES+THPE):POSS molar ratio is 1:1; (c) A trend graph showing the foaming ratio of PES composite materials with different (PES+THPE):POSS molar ratios when the PES molar content is fixed at 0.0026 mol; (d) A trend graph showing the foaming ratio of PES composite materials with increasing (PES+THPE):POSS molar ratio. Figure 8 (a) Data shows that under the same experimental conditions (swelling at 18 MPa for 2 hours), the maximum foaming ratio of the pure PES sample was 2.4, while the highest foaming ratio of sample #11 reached 5.3. The significantly improved foaming ratio indicates that the melt strength of the sample has an optimal value after introducing a micro-crosslinked network. Compared with the original sample, the foaming temperature range is widened, and the optimal foaming ratio is obtained while having a small and uniform pore structure, which will significantly reduce the dielectric properties of the material and obtain the best antenna performance.

[0059] Figure 9 This demonstrates the pore size parameters of the composite materials for each component when achieving the optimal foaming ratio; the pore size of all components is less than 10 μm. Figure 9 (a) Figure 10 (a) It can be seen that sample #11, at its optimal foaming ratio, has a small pore size (6.5 μm) and a pore density of 1.6 * 10⁻⁶. 9 pcs / cm 3 .

[0060] The uniform pore structure formed by introducing supercritical CO2 foaming process can significantly reduce the dielectric properties of materials. Figure 11(a) and (b) tested the dielectric constant and dielectric loss of the PES composite material at a frequency of 10 GHz; Figure 11 (c) and (d) estimate the dielectric constant and dielectric loss of the composite foam material based on the dielectric properties of (a) and (b) and formulas (1) and (2). Figure 11 Data analysis in (c) and (d) shows that the dielectric constant of the unfoamed PES composite material is around 3.2, and the dielectric loss tangent is around 0.008. The theoretical dielectric constant and loss of the foamed system, calculated using formulas (1) and (2), are reduced to 1.4–1.8 and 0.0013–0.004, respectively. Since sample #11 has the highest foaming ratio of 5.3, it exhibits the lowest dielectric constant and dielectric loss.

[0061]

[0062] Figure 12 This is a two-dimensional antenna radiation pattern for each component of the foamed sample at 10 GHz, representing a graph of the antenna's radiation parameters as a function of spatial coordinates. The radiation parameters can include the antenna's radiated power flux density, field strength, phase, polarization, etc. It can be seen that a narrower main lobe indicates more concentrated energy radiation, while smaller side lobes indicate less energy dispersion and higher gain. Figure 13 It can be seen that the gains of the foamed PES / POSS composite materials are all high, exceeding 8.4 dBi, and the efficiencies are all above 85%. Among them, sample #11 has the highest gain and efficiency, indicating that the antenna concentrates the radiation of input power to a high degree, thus the antenna has a strong ability to transmit and receive signals in a specific direction and has high energy conversion efficiency. This shows that the nanocomposite material prepared by constructing a micro-crosslinked network within PES, and introducing air with scCO2, yields an excellent antenna material.

[0063] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the invention is intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope.

Claims

1. A microporous nanofoamed material with a micro-nano pore structure, characterized in that, The microporous nanofoamed material comprises 80-95 wt% of hydroxyl-terminated polymer, 0.2-10 wt% of dendritic polyepoxy compounds, 2-15 wt% of polyhydroxy compound co-crosslinking agents, and 0.5-2 wt% of ZnO catalyst.

2. The microporous nanofoamed material according to claim 1, characterized in that, The dendritic polyepoxy compound is selected from one or more of 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, glycidyl ether, pentaerythritol glycidyl ether, glycidyl etheroxypropyl cage polysilsesquioxane, and glycidyl etheroxypropyl cyclotetrasiloxane.

3. The microporous nanofoamed material according to claim 1, characterized in that, The polyhydroxy compound co-crosslinking agent is selected from one or more of 1,1,1-tris(4-hydroxyphenyl)ethane, 1,3,5-benzenetriethanol, pentaerythritol, epiinositol, tris(hydroxymethyl)aminomethane (Tris base), di(2-hydroxyethyl)iminotris(hydroxymethyl)methane (BIS-TRIS), and D-sorbitol.

4. The microporous nanofoamed material according to claim 1, characterized in that, The hydroxyl-terminated polymer is selected from polyethersulfone, polyimide, and liquid crystal polymer.

5. The microporous nanofoamed material according to claim 1, characterized in that, The pore size of the microporous nanofoamed material is less than 10 μm.

6. A method for preparing the microporous nanofoamed material with a micro-nanoporous structure as described in claim 1, characterized in that, Includes the following steps: (1) A hydroxyl-terminated polymer, a dendritic polyepoxy compound, a polyhydroxy compound crosslinking agent and a ZnO catalyst are mixed in proportion and melted at high temperature in an air-isolated environment to form a nanocomposite material, and then shaped into a preform. (2) The preform is subjected to supercritical foaming to obtain microporous nano foam material.

7. The method according to claim 6, characterized in that, Before step (1), the hydroxyl-terminated polymer needs to be vacuum dried at a temperature of 100-150℃ for 2-10 hours.

8. The method according to claim 6, characterized in that, In step (1), the temperature of the high-temperature melting is 300-400℃, and a shear field needs to be applied during the melting process.

9. The method according to claim 6, characterized in that, In step (2), the supercritical foaming agent used is CO2, the foaming temperature is 200-300℃, the foaming pressure is 10-20Mpa, and the foaming time is 0.5-5h.

10. The application of the microporous nanofoamed material with micro-nano pore structure according to claim 1 in terahertz antennas.

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