WO2022062863A1

WO2022062863A1 - Integrated high-broadband-wave-transmittance strong-toughness polyolefin microporous foam material and preparation method therefor

Info

Publication number: WO2022062863A1
Application number: PCT/CN2021/115866
Authority: WO
Inventors: 龚鹏剑; 李光宪; 王素真; 洪江; 蒋根杰
Original assignee: 江苏集萃先进高分子材料研究所有限公司; 长链轻材(南京)科技有限公司
Priority date: 2020-09-22
Filing date: 2021-09-01
Publication date: 2022-03-31
Also published as: CN113290879B; CN112111101A; CN113290879A; CN112111101B

Abstract

The present invention relates to an integrated high-broadband-wave-transmittance strong-toughness polyolefin microporous foam material and a preparation method therefor, and belongs to the technical field of communication equipment materials. In the present invention, with regard to the wave transmission performance required by communication equipment in a broadband electromagnetic wave band of 600 MHz to 300 GHz, an integrated high-broadband-wave-transmittance strong-toughness polyolefin material is manufactured by means of subjecting a polyolefin foaming raw material to blending and modification with a self-synthesized β-cyclodextrin amino esterification modifier and then to multi-layer co-extrusion and a green and environmentally friendly one-piece solid-state pressure molding foaming technique. With regard to the wave-transmitting material of the present invention, the main raw material thereof is a polyolefin material, and the structure of the material is mainly a middle layer and skin layers located on both sides, wherein the middle layer and the skin layers both have a foamed structure with a foam cell wall thickness of less than 100 nm, and the foaming rates of the two are different. Such a structure can not only effectively improve the transmittance of a millimeter wave, but also greatly improves production efficiency, shortens a process flow, and reduces production costs.

Description

A kind of integrated broadband high-transmittance wave-strength and tough polyolefin microcellular foam material and preparation method thereof

technical field

The invention relates to an integrated broadband, high-wave-transmitting, strong and tough polyolefin microcellular foam material and a preparation method thereof, and belongs to the technical field of communication equipment materials.

Background technique

High-frequency 5G communication is millimeter wave, and the disadvantage is that it tends to propagate in a straight line and has significant attenuation. The frequency bands mainly used in the current 5G communication market are divided into two parts, 5G-sub6 frequency band (617MHz-5GHz) and 5G-mmW frequency band (26.5GHz-40GHz). It also puts forward certain requirements and demands for its wave transmission performance in broadband and high frequency bands.

However, the current millimeter-wave radome wave-transmitting material structures are mostly sandwich structure composite materials, such as foam sandwich structure composite materials or honeycomb sandwich structure composite materials. The skin layer of the foam sandwich composite structure is generally a fiber-reinforced thermosetting resin material, and the core layer is generally a thermosetting rigid foam, such as PMI foam, which has problems such as difficulty in recycling and processing.

In response to the above problems, some manufacturers have used thermoplastic resins as core materials or skins to solve the environmental protection problems of materials, see the following patents for details.

Patent CN103660410A discloses a radome wave-transmitting sandwich material and its preparation method and use. The outer skin is made of fiber-reinforced thermoplastic composite material, and the core layer is foamed polyurethane, phenolic resin or epoxy resin material. In the method, the thermoplastic resin of the skin material is polyolefin, thermoplastic polyester and polyamide. However, in this method, the core layer foam material is still a thermosetting foam, and the environmental protection is low. Although the environmental protection problem of the material is solved to a certain extent, there are many technological processes, high cost, and obvious interface problems in terms of structure. The hidden danger of long-term use, it is easy to cause the interface to separate, thereby reducing the dielectric properties and shortening the service life.

Polyolefins are general-purpose non-polar thermoplastics with low dielectric constant and dielectric loss, strong processability, strong hydrophobicity and low cost. However, its microcellular foam material is relatively brittle and has poor tear resistance, which limits its application in the field of wave-transmitting materials to a certain extent.

SUMMARY OF THE INVENTION

Aiming at the wave-transmitting performance required by the communication equipment in the broadband electromagnetic wave frequency band of 600MHz-300GHz, the invention uses the self-synthesized β-cyclodextrin urethane-based modifier to blend and modify the polyolefin foaming material, and Through multi-layer co-extrusion and green and environment-friendly integral molding molding foaming technology, an integrated broad-band high-wave-transmitting and tough polyolefin material is produced, which is lightweight, high-strength, simple in process and low in cost.

The technical solution is:

An integrated broadband high-transmittance wave-strength polyolefin microcellular foam material, which comprises an intermediate layer and upper and lower skin layers located on both sides of the intermediate layer;

The material of the upper and lower skin layers contains 90-95% of polyolefin, 5-10% of β-cyclodextrin urethane-based modifier, 0-1% of flame retardant, and 0-1% of anti-aging agent by weight percentage. ;

The material of the middle layer contains 93-98% by weight of polyolefin, 1-3% of beta-cyclodextrin urethane-based modifier, 0.5-2% of flame retardant, and 0.5-2% of anti-aging agent ;

In one embodiment, the overall thickness of the foam material is 28-40 mm, the thickness of the upper and lower skin layers is 1-4 mm, and the overall density is between 0.04-0.09 g/cm ³ ; the cell diameter of the intermediate layer is <50 μm, and the cell diameter of the upper and lower skin layers is < 20μm, the cell wall thickness of both is <100nm.

The preparation method of β-cyclodextrin urethane modification agent comprises the following steps: step a, adding polyisocyanate to the pyridine solution of β-cyclodextrin, then adding a catalyst, and reacting to obtain a prepolymer; step b, after cooling down, continue to add chain extender for reaction, then add polymerization inhibitor to complete the reaction, after cooling, obtain β-cyclodextrin urethane-based modifier.

In one embodiment, in the step a, the reaction temperature is 75-85° C., and the reaction time is 1-5 h.

In one embodiment, the cooling in step b refers to cooling to 60°C, the reaction temperature is 75-85°C, and the reaction time is 0.5-3h.

In one embodiment, the polyisocyanate is selected from toluene diisocyanate, the catalyst is selected from organotin catalysts, and the chain extender is a polyol, such as ethylene glycol or glycerin.

In one embodiment, in step a, the amount ratio of polyisocyanate and β-cyclodextrin is such that n(-NCO)/n(-CH ₂ OH) is between 1.8-2.0; in step b, chain extender The added amount is 0.3-0.7 times the amount of residual NCO group substances in the prepolymer.

The preparation method of the integrated broadband high-transmittance wave-strength and tough polyolefin microcellular foam material comprises the following steps:

Step 1, fully mixing polyolefin, modified β-cyclodextrin urethane-based modifier, flame retardant, and anti-aging agent, and extruding a three-layer sheet using a three-layer twin-screw extruder;

In step 2, the sheet obtained in step 1 is placed in the mold cavity of the molding foaming machine, and the upper and lower surfaces of the mold cavity are pasted with release films, filled with supercritical fluid, and the mold is opened to release pressure to obtain a wave-transmitting material. .

In one embodiment, in step 2, after the supercritical fluid is charged, the cavity pressure is 8-25 MPa, the cavity temperature is 120-270° C., and the temperature is maintained for 10-260 minutes.

In one embodiment, the pressure relief speed of the pressure relief process is >5MPa/s; the foaming ratio of the intermediate core material is about 10-40 times, and the foaming ratio of the upper and lower skin layers is about 2-5 times.

beneficial effect

The invention prepares a broad-band, high-transmittance and tough polyolefin material aimed at the broadband electromagnetic wave frequency band of 600MHz-300GHz. When the pore diameter of the material is less than 50 μm and the thickness of the pore wall is less than 100 nm, the permeability of millimeter waves can be effectively improved.

In the preparation process, a three-layer co-extrusion screw was used to extrude a sheet with a three-layer structure, and then it was foamed through a supercritical foaming cavity with a release film to obtain a dense and small foaming ratio on both sides. , The wave-transmitting material with large internal foaming ratio realizes the integrated preparation of materials.

In the preparation of the material, the use of urethane-modified β-cyclodextrin can effectively promote the diffusion and dissolution of CO ₂ , improve the nucleation efficiency, and effectively reduce the size of the cells. The internal cells are small and uniform, suitable for use in communication equipment. The modification of urethane not only increases the melt strength of the material, but also endows the cell wall with more toughness due to the introduction of long chains and improves the mechanical properties of the material.

Description of drawings

Fig. 1: SEM image of the liquid nitrogen quenching section of the skin layer of Example 1;

Figure 2: SEM image of the liquid nitrogen quenching section of the intermediate layer of Example 1;

Figure 3: SEM image of the liquid nitrogen quenching section of the skin layer of Comparative Example 1

Figure 4: SEM image of the liquid nitrogen quenching section of the intermediate layer of Comparative Example 1;

Figure 5: Infrared spectrum of modified β-cyclodextrin urethane modifier;

detailed description

The present invention develops a wave-transmitting material for the communication equipment in the broadband electromagnetic wave frequency band of 600MHz-300GHz. The communication equipment used here can be a millimeter wave radome. A wave-transmitting material is installed inside the casing.

In the wave-transmitting material of the present invention, its main raw material is polyolefin material, and the structure of the material is mainly an intermediate layer and a skin layer on both sides. The foaming ratios are different. Such a structure can not only effectively improve the permeability of millimeter waves, but also greatly improve the production efficiency, shorten the process flow, and reduce the production cost.

In a typical embodiment, the overall thickness of the foam material is 28-40 mm, the thickness of the upper and lower skin layers is 1-4 mm, and the overall density is between 0.04-0.09 g/cm ³ ; the cell diameter of the intermediate layer is less than 50 μm, and the cells of the upper and lower skin layers are smaller than 50 μm. Pore size <20μm. Since the wavelength of the commonly used millimeter wave is between 1 and 50 mm, and the cell diameter in the present invention is less than 50 μm and the thickness of the cell wall is within the range of less than 100 nm, according to the relevant electromagnetic wave propagation theory such as Fresnel, it can be known that this structure can effectively Improve millimeter wave transmittance.

The above preparation process of the wave-transmitting material can be divided into two steps: the preparation of raw materials and the foaming process.

For the preparation process of raw materials, the polyolefin pellets (melt index ≤ 5g/10min), β-cyclodextrin urethane-based modifier, flame retardant and anti-aging agent are fully mixed and used three-layer co-extrusion screw. Polyolefin sheet with thickness of 10-15mm in extruder, thickness of upper and lower layers is 0.5mm-2mm, content of β-cyclodextrin urethane modifier is 1%-5%, and middle layer is 6- 14mm thick, the content of β-cyclodextrin urethane modification agent is 3%-10%. The upper and lower skin layers are modified more, that is, the solubility of CO ₂ is promoted, the nucleation efficiency is improved, and the cell size is effectively reduced; under low foaming ratio, the hardness is increased, and the toughening modification can also effectively improve the toughness of the hardened layer, which is both hard and tough .

In the above steps, the purpose of the three-layer twin-screw extruder is to make the density of the upper and lower surface layers of the prepared sheet more dense, and to make the upper and lower layers foaming ratio smaller in the subsequent foaming process. The foaming ratio can be adjusted by adding different proportions of modified β-cyclodextrin urethane modifier into the materials of the upper and lower layers and the middle layer.

In the above-mentioned steps, the modified β-cyclodextrin urethane modified agent used, β-cyclodextrin is a cyclic oligomer composed of 7 D(+)-glucopyranose, and its molecular It is a hollow cylinder with a wide top and a narrow bottom, open at both ends, and the interior of the cavity is relatively hydrophobic, while all the hydroxyl groups are outside the molecule; it has the following advantages: 1. A large number of hydroxyl groups exist outside, and a large number of rigid hydroxyl groups are introduced. The five-membered ring enhances the intermolecular force and the branching degree of the material molecules; the modifier has both the hollow structure of cyclodextrin and the elastic group of polyurethane, and the addition of the modifier can be very good with polyolefin. It can effectively increase the resilience of foamed materials. 2. The interior is a hydrophobic hollow structure, which can not only form a large number of air pockets, reduce the cell nucleation energy barrier, increase the cell nucleation density, but also promote the diffusion of supercritical gas to a certain extent. 3. The whole can play the role of heterogeneous nucleating agent.

In the present invention, its derivative is used as modifier, and the synthesis reaction process is as follows:

Synthesis of Prepolymer:

The prepolymer is labeled R1:

As the flame retardant in the foamed material, halogen-free-antimony-free inorganic flame retardants, such as metal hydroxides, hydrates of metal compounds, and the like are preferred. More specifically, aluminum hydroxide, magnesium hydroxide, magnesium oxide, hydrate of zinc oxide, and the like. The above-mentioned hydrated metal compounds may also be subjected to surface treatment. The flame retardant may be used alone or in combination of two or more. As the antiaging agent in the foamed material, known antiaging agents such as amine-based, phenol-based, imidazole-based, metal carbamate, and the like can be used.

After the above-mentioned sheet is obtained, a foaming step is performed. The method can be as follows: step 1, providing the raw material of the foaming material; step 2, adding the raw material in step 1 into the mold cavity of the foaming machine, and two opposite surfaces inside the mold cavity of the foaming machine are affixed with release molds In the present invention, the release film is arranged on the upper and lower positions of the mold cavity, which can form relatively dense skin layers on the upper and lower surfaces of the wave-transmitting material after the foaming process, thereby improving the weather resistance and mechanical properties of the material to a certain extent. . Step 3: Fill the mold cavity of the foaming machine with supercritical fluid, open the mold to release pressure, and obtain a wave-transmitting material. In the above preparation process, placing a smooth release film in the mold helps to form a smooth crust on the surface of the wave-transmitting microcellular foam, thereby improving the mechanical properties such as pressure resistance of the material to a certain extent.

In a typical preparation process, the preparation steps are as follows: put the obtained polyolefin sheet into the cavity of a multi-layer molding foaming machine (with smooth release films attached to the upper and lower sides), fill it with supercritical fluid, and the pressure is 8 -25MPa, the temperature is 150-170℃, after heat preservation and pressure keeping for 10-60min, the mold is quickly opened to release the pressure (the pressure release speed is greater than 5MPa/s), that is, the polyolefin strong and tough microcellular foam wave-transmitting material with upper and lower smooth skins is obtained. .

Example 1

The preparation process of β-cyclodextrin urethane modification agent is as follows: in a dry three-necked flask, the toluene diisocyanate solution is dropped into the pyridine solution of the dehydrated β-cyclodextrin, wherein n(-NCO)/ n( _-CH2OH ) is between 1.8-2.0. Then add a small amount of catalyst (organotin such as dibutyltin dilaurate) and stir evenly. The reaction exotherm is automatically heated to 80 °C, and the reaction is performed at a constant temperature for about 2 hours to obtain a prepolymer. Cool down to about 60°C, add the chain extender ethylene glycol dropwise (the amount of the substance is 0.43 times the amount of the residual NCO group substance in the prepolymer), and quickly mix it evenly. When the temperature rises to about 80°C, stop stirring and turn it on. Vacuum devolatilization. The reaction was cooled for about 0.5-1 h, and a polymerization inhibitor (organic amines such as dibutylamine) was added at 40°C, and the mixture was rapidly stirred and poured into a low-temperature container to cool to room temperature. That is, the β-cyclodextrin urethane modification agent is obtained. The FTIR spectrum of the prepared β-cyclodextrin urethane modifier is shown in Figure 4, wherein the characteristic absorption peak of NH- at 1552cm ^-1 and the characteristic absorption peak of -C=O at 1707cm ^-1 , 3500cm ^-1 is the characteristic absorption peak of -OH on β-cyclodextrin, which confirms the synthesis of the above modifier.

Uniform polypropylene pellets (melt index 5g/10min), β-cyclodextrin urethane-based modifier, flame retardant and anti-aging agent at 90:8:1:1 and 95:2:1:1 After blending, it is respectively added to the twin-screw multi-layer sheet extruder of the outer layer and the inner layer, the processing temperature is 210-290°C, and the temperature of the sheet extrusion die is between 180-240°C. A polyolefin sheet having a thickness of 10 mm was obtained through a three-roll cooling stand.

Put the obtained polypropylene sheet into the mold cavity of the multi-layer molding foaming machine (with smooth release films on the top and bottom), fill it with supercritical fluid, the pressure is 13MPa, the temperature is 163°C, and after heat preservation and pressure preservation for 30min, Quickly open the mold and release the pressure to obtain a high-toughness one-piece polyolefin microporous and high wave-transmitting material.

Example 2

Homogenize polypropylene pellets (melt index 2g/10min), β-cyclodextrin urethane-based modifier, flame retardant and anti-aging agent according to 91:7:1:1 and 97:1:1:1 After blending, it is respectively added to the twin-screw multi-layer sheet extruder of the outer layer and the inner layer, the processing temperature is 210-290°C, and the temperature of the sheet extrusion die is between 180-240°C. A polyolefin sheet having a thickness of 10 mm was obtained through a three-roll cooling stand.

Put the obtained polypropylene sheet into the mold cavity of the multi-layer molding foaming machine (with smooth release films on the top and bottom), fill it with supercritical fluid, the pressure is 10MPa, the temperature is 163 ℃, and after heat preservation and pressure for 30min, Quickly open the mold and release the pressure to obtain a high-toughness one-piece polyolefin microporous and high wave-transmitting material.

Comparative Example 1

Compared to Example 1, the only difference is that there is no β-cyclodextrin urethane modifier in the blend.

Comparative Example 2

Compared with Example 1, the only difference is that a glass fiber reinforced epoxy resin skin (cured after hand lay-up) is pasted on the top and bottom in the later stage, and the thickness of the skin is 1 mm, ensuring that the overall thickness is the same as that of Example 1.

Comparative Example 3

Compared with Example 1, the only difference is that no smooth release film is placed in the foaming cavity.

Comparative Example 4

Compared with Example 1, the only difference is that the screw extruder of three-layer co-extrusion is not adopted, and the ordinary single-layer die screw extruder is directly adopted, and the material is the material mixing ratio of the middle layer (polypropylene pellets (melt index). 5g/10min), β-cyclodextrin urethane modification agent, flame retardant and anti-aging agent according to 90:8:1:1), the obtained sheet has no surface skin layer.

Comparative Example 5

Compared with Example 1, the only difference is that the modifier added is not modified with polyurethane.

test method:

Measurement of cell diameter and cell wall thickness: Use Nano Measurer software to mark the diameter of each cell and cell wall thickness in the SEM image of the sample, and then check the average cell diameter from the software analysis report, and use the formula to calculate the average cell wall thickness ,Calculated as follows:

where ρ _o is the average density of the unfoamed product, ρ _f is the apparent density of the foamed product, dw is the cell wall thickness, and Φc is the cell diameter;

Wave transmittance: measure the wave transmittance under the condition of 24GHz-60GHz by free space method;

Mechanical properties: The test standard for peel strength is GB8808-1988, the test standard for compressive strength is GB8813-2008, and the test standard for tensile strength and elongation at break is GB9641-1988.

Performance test table

It can be seen from the data and SEM images of Example 1, Example 2 and Comparative Example 1 that the integrated millimeter-wave wave-transmitting material cells were prepared by using the modifier independently developed by this project and the green supercritical solid foaming technology. All are less than 100 μm. The addition of the self-modifying agent improves the tensile and compressive properties of the product, and the obtained cell has a smaller pore size. This is because the hollow and hydrophobic pores of the self-developed modifier not only accelerate the ultra The diffusion of the critical gas in the foamed matrix also plays a certain role in nucleation and improves the nucleation density of the product. On the other hand, the elastic group it carries also increases the toughness of the product, offsetting the influence of the nucleation of part of the modifier on the toughness of the material.

From the comparison of the wave transmittance and mechanical properties of Example 1 and Comparative Example 2, it can be seen that although the wave-transmitting material of the sandwich structure can improve the performance of the material in terms of tensile strength, it is more integral than the present invention. Due to the obvious interface, the wave-transmitting material of the type structure has obvious deficiencies in peel strength and wave-transmitting performance, and is heavier and difficult to recycle.

From the relevant data of Example 1 and Comparative Example 3, it can be seen that placing a smooth release film in the mold helps to form a smooth crust on the surface of the wave-transmitting microcellular foam, thereby improving the mechanical properties such as stretching of the material to a certain extent. performance.

From the relevant data of Example 1 and Comparative Example 4, it can be seen that by adopting the processing method of three-layer co-extrusion screw extrusion, and adjusting the content of the modifier in the upper and lower layers, the upper and lower layers are realized in the foaming process. The change in magnification further improves the strength of the prepared material, simplifies the material modification process, and reduces the cost.

It can be seen from the relevant data of Example 1 and Comparative Example 5 that after the urethane modification of the β-cyclodextrin modifier, the mechanical properties such as compression and tension of the material have been greatly improved. This is because the modification of urethane not only increases the melt strength of the material, but also endows the cell wall with more toughness due to the introduction of long chains and improves the mechanical properties of the material.

To sum up, the present invention aims at the wave-transmitting performance required by communication equipment in the broadband electromagnetic wave frequency band of 600MHz-300GHz, and uses the self-synthesized β-cyclodextrin urethane-based modifier to blend the polyolefin foam raw material. Through multi-layer co-extrusion and green and environmentally friendly integrated solid-state molding and foaming technology, an integrated broadband, high-wave-transmitting, and tough polyolefin material is produced. In the wave-transmitting material of the present invention, its main raw material is polyolefin material, and the structure of the material is mainly an intermediate layer and a skin layer on both sides. The foaming ratios are different. Such a structure can not only effectively improve the permeability of millimeter waves, but also greatly improve the production efficiency, shorten the process flow, and reduce the production cost.

Claims

An integrated broadband high-transmittance wave-strength and tough polyolefin microcellular foam material, characterized in that it comprises an intermediate layer and upper and lower skin layers located on both sides of the intermediate layer;

The material of the upper and lower skin layers contains 90-95% of polyolefin, 3-10% of β-cyclodextrin urethane-based modifier, 1-2% of flame retardant, and 1-2% of anti-aging agent by weight percentage. ;

The material of the middle layer contains 92-96% by weight of polyolefin, 1-5% of beta-cyclodextrin urethane modifier, 1-2% of flame retardant, and 1-2% of anti-aging agent ;

In one embodiment, the overall thickness of the foam material is 28-40 mm, the thickness of the upper and lower skin layers is 1-4 mm, and the overall density is between 0.04-0.09 g/cm 3 ; the cell diameter of the intermediate layer is <50 μm, and the cell diameter of the upper and lower skin layers is < 20μm, the cell wall thickness of both is <100nm.
The integrated broadband, high-wave-transmitting, and tough polyolefin microcellular foam material according to claim 1, wherein the preparation method of the β-cyclodextrin urethane-based modifier comprises the following steps: Step a: Isocyanate is added to the pyridine solution of β-cyclodextrin, and then a catalyst is added to carry out the reaction to obtain a prepolymer; in step b, after cooling down, continue to add a chain extender to carry out the reaction, and then add a polymerization inhibitor to complete the reaction, and after cooling, The β-cyclodextrin urethane modifier was obtained.
The integrated broadband high-transmittance and tough polyolefin microcellular foam material according to claim 2, characterized in that, in one embodiment, in the step a, the reaction temperature is 75-85°C, and the reaction time is 1 -5h.
The integrated broadband, high-wave-transmitting, and tough polyolefin microcellular foam material according to claim 2, wherein, in one embodiment, the cooling in step b refers to cooling to 60°C, and the reaction temperature is 75-85°C, the reaction time is 0.5-3h.
The integrated broadband, high-wave-transmitting, and tough polyolefin microcellular foam material according to claim 2, wherein, in one embodiment, the polyisocyanate is selected from toluene diisocyanate, and the catalyst is selected from organic Tin-based catalyst, the chain extender is polyols, such as ethylene glycol or glycerol.
The integrated broadband, high-wave-transmitting, and tough polyolefin microcellular foam material according to claim 2, wherein, in one embodiment, in step a, the dosage ratio of polyisocyanate and β-cyclodextrin is such that n (-NCO)/n(-CH 2 OH) is between 1.8-2.0; in step b, the amount of chain extender added is 0.3-0.7 times the amount of residual NCO group species in the prepolymer.
The method for preparing an integrated broadband high-transmittance wave-strength and tough polyolefin microcellular foam material is characterized by comprising the following steps: Step 1: urethane-based modification agent flame retardant of polyolefin and modified β-cyclodextrin , The anti-aging agent is fully mixed and the three-layer co-extrusion screw extruder is used to extrude the sheet; step 2, the sheet obtained in step 1 is placed in the cavity of the molding foaming machine, and the upper and lower surfaces of the cavity are attached There is a release film, which is filled with supercritical fluid, and the mold is opened to release the pressure to obtain a wave-transmitting material.
The method for preparing an integrated broadband, high-wave-transmitting, and tough polyolefin microcellular foam material according to claim 6, characterized in that, in one embodiment, in step 2, the cavity pressure after filling with supercritical fluid is 8 -25MPa, the cavity temperature is 120-270℃, and the heat preservation and pressure are maintained for 10-260min.
The method for preparing an integrated broadband, high-wave-transmitting, and tough polyolefin microcellular foam material according to claim 6, wherein, in one embodiment, the pressure-releasing speed of the pressure-releasing process is >5MPa/s; the intermediate core material The foaming ratio is about 10-40 times, and the foaming ratio of the upper and lower skin layers is about 2-5 times.