A polyphenyl ether composite foamed material, a preparation method and a performance prediction method

Abstract

The application discloses a kind of polyphenyl ether composite foamed materials, preparation method and performance prediction method, the bubble diameter range of the composite foamed material is 5-300 μm, and the foaming ratio in 180-200 ℃ is 4-22.The application takes polyphenyl ether (PPO) and styrene-ethylene-butylene-styrene pre-block copolymer (SEBS) as production example, supercritical CO2 as physical foaming agent, and uses intermittent foaming process to supercritical solid state forming PPO to prepare PPO wave-transparent and wave-absorbing material.The addition of SEBS significantly improves the toughness of PPO, and then improves its foaming ratio, significantly improves the impedance matching with air, and improves the wave-transparent device at high frequency under high-speed low-loss propagation;Combined with the synergistic effect of conductive particles and the design of pore structure, the wave-absorbing performance of the wave-absorbing device is significantly improved.Meanwhile, the dielectric property prediction method provided by the application can provide theoretical guidance for obtaining low dielectric constant and dielectric loss polyphenyl ether composite foamed material.

Description

Technical Field

[0001] This invention relates to a polyphenylene ether composite foam material, its preparation method, and its performance prediction method, belonging to the field of electromagnetic materials technology. Background Technology

[0002] The electronics and information industry has significantly accelerated the development of social informatization and intelligentization through the design and development of electronic devices and information systems. Fifth-generation mobile communication technology (5G) enables ultra-high-speed processing of massive amounts of data, making the Internet of Things (IoT), such as vehicle-to-everything (V2X), possible. Therefore, 5G places higher demands on high-speed and low-latency electromagnetic wave propagation at high frequencies (FR1: 450MHz-6GHz, FR2: 24GHz-52GHz), requiring both high speed and low loss. The development of the electronics and information industry has also led to an increasing environmental impact of electromagnetic radiation, such as interference with the stable operation of aircraft, radar, mobile phones, and electronic diagnostic equipment. Therefore, there is an urgent need to develop electromagnetic wave-transmitting / absorbing devices that can be controlled to meet the needs of current social development.

[0003] Supercritical foaming technology introduces supercritical physical foaming agents (such as CO2 and N2) to produce porous composite materials with uniform pore size after cell nucleation and growth. The introduction of air creates a continuous structure of cell wall-air-cell wall within the material, which significantly improves the impedance matching between the material and air. This allows electromagnetic waves to completely pass through the surface of the product and enter its interior, forming the basis for the fabrication and industrialization of electromagnetic wave-controlled communication devices.

[0004] Polyphenylene oxide (PPO), with its high-temperature resistance and self-flame retardant properties, is highly advantageous for 5G communication devices and microwave absorbing devices. However, its relatively high rigidity of microscopic molecular chains makes molding and processing difficult, and the molded products are prone to internal stress, requiring subsequent annealing treatment, which significantly slows down production efficiency. Furthermore, the rigidity of PPO results in poor toughness, leading to a limited air content that cannot be introduced during supercritical foaming molding. This prevents the full utilization of its impedance matching advantage with air, allowing electromagnetic waves to be introduced into the PPO, causing losses (for transparent devices) and contamination (for microwave absorbing devices) during electromagnetic wave transmission. Summary of the Invention

[0005] This invention provides a polyphenylene ether composite foam material and its preparation method that can improve the high-speed, low-loss propagation of wave-transmitting devices at high frequencies and enhance the wave-absorbing performance of wave-absorbing devices by incorporating conductive particles. Furthermore, this invention provides a method for predicting the dielectric properties of this polyphenylene ether composite foam material, which can provide theoretical guidance for obtaining composite foam materials with low dielectric constants and dielectric losses.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A polyphenylene ether composite foam material comprising, by mass fraction: polyphenylene ether, toughening agent, flame retardant, and coupling agent;

[0008] The toughening agent is one or more of polystyrene, high-impact polystyrene, styrene-butadiene-styrene triblock copolymer, styrene-ethylene-butene-styrene preblock copolymer, acrylonitrile-butadiene-styrene copolymer, and polyphenylene sulfide;

[0009] The polyphenylene ether composite foam material also contains carbon filler by mass fraction;

[0010] The polyphenylene ether composite foam material is prepared by a supercritical foaming method.

[0011] The foam diameter range of the polyphenylene ether composite foam material is 5-300μm;

[0012] The polyphenylene ether composite foam material has a foaming ratio of 4-22 at 180-200℃, a dielectric constant of 1-1.2, and a dielectric loss of 0.0003-0.0020.

[0013] Preferably, in the polyphenylene ether composite foam material, the polyphenylene ether is 45-75 wt%, the toughening agent is 8-20 wt%, the flame retardant is 3-15 wt%, the coupling agent is 2-8 wt%, and the carbon filler is 8-25 wt%.

[0014] Preferably, the carbon filler is a mixture of conductive carbon black and carbon fiber, and the mass ratio of conductive carbon black to carbon fiber is 1:(1~1.5).

[0015] Preferably, the polyphenylene ether composite foam material has a foam diameter range of 5-100 μm and a foaming ratio of 4-12 at 180-200℃.

[0016] Preferably, the flame retardant is one or more of the following: nitrogen-based flame retardant, phosphorus-based flame retardant, antimony-halogen system flame retardant, phosphorus-halogen system flame retardant, and nitrogen-phosphorus system flame retardant.

[0017] The preparation method of the above-mentioned polyphenylene ether composite foam material includes the following steps:

[0018] S1: After drying polyphenylene ether and toughening agent, they are pre-blended with flame retardant, coupling agent and carbon filler, and then extruded through an extruder to obtain composite material;

[0019] S2: The composite material is subjected to supercritical foaming treatment to obtain polyphenylene ether composite foam material.

[0020] Preferably, the drying method is: drying at 70-100℃ for 3-7 hours; the pre-mixing method is: stirring at room temperature at a speed of 10-50 r / min for 2-10 min.

[0021] Preferably, the temperatures of each section of the extruder process are as follows: conveying section 150-200℃, melting section 210-265℃, extrusion section 200-260℃; screw speed 100-200 r / min.

[0022] Preferably, the specific method of supercritical foaming treatment is as follows: CO2 or N2 is used as a foaming agent, and swelling is carried out for 3.5-5 hours at a temperature of 170-210℃ and a pressure of 10-17 MPa.

[0023] The above-mentioned method for preparing polyphenylene ether composite foam materials also includes a method for predicting the dielectric properties of polyphenylene ether composite foam materials, comprising the following steps:

[0024] The solid content ratio and air content ratio of the solid part in the composite foam material are calculated based on the foaming ratio N. The solid content ratio of the solid part is 1 / N, and the air content ratio is (N-1) / N.

[0025] Calculate the percentage of each component in the solid portion of the composite foam material, denoted as y1, y2, ..., y n n is the number of solid components;

[0026] Based on the dielectric constant and dielectric loss calculation formulas, the dielectric constant ε and dielectric loss δ of the composite foam material are obtained; whereby the dielectric constant calculation formula is:

[0027] ε=(ε1×y1+ε2×y2+…+ε n ×y n ) / N+ε 气 ×(N-1) / N

[0028] = (ε1×y1+ε2×y2+…+ε n ×y n +ε 气 ×(N-1)) / N,

[0029] In the formula, ε1, ε2, ..., ε n These are the dielectric constants of components 1, 2, ..., n, respectively; ε 气 is the dielectric constant of air; N is the foaming ratio;

[0030] The formula for calculating dielectric loss is:

[0031] δ=(δ1×y1+δ2×y2+…+δ n ×y n ) / N

[0032] In the formula, δ1, δ2, ..., δ n These represent the dielectric losses of components 1, 2, ..., n, respectively; N is the foaming ratio.

[0033] The beneficial effects of this invention are as follows:

[0034] 1. The improved toughness of composite foam materials significantly increases the foaming ratio of wave-transmitting / wave-absorbing devices made from them. This not only greatly improves their impedance matching with air, making it very easy for electromagnetic waves to enter the device and enable it to function, but also achieves the advantage of significantly reducing costs (significantly reducing material usage for the same volume, thus reducing costs).

[0035] 2. Improved toughness significantly increases the foaming ratio of wave-transmitting / wave-absorbing devices made from composite foamed materials, while also significantly improving the high-frequency, high-speed, low-loss propagation of electromagnetic waves and the full absorption of electromagnetic waves (the absorption efficiency is extremely high after adding absorbing fillers CB and CNF, with an absorption rate of up to 96%).

[0036] 3. The improved toughness also significantly reduces the internal stress of the wave-transmitting / absorbing devices made from composite foam materials during the molding process, avoiding the problem of internal stress cracking in the production process. At the same time, the annealing post-treatment step is eliminated, greatly improving production efficiency.

[0037] 4. Because SEBS itself has good stability and aging resistance, it also gives the microwave absorbing / transmitting device good characteristics. Combined with the high temperature resistance and self-flame retardant properties of PPO, the device made of composite foam material has excellent performance, significantly improving the service life of the device in harsh environments, and thus saving the cost of use.

[0038] 5. The synergistic effect between 0D CB and 1D CNF nanoparticles, combined with the excellent air impedance matching pore structure introduced by supercritical molding, will significantly improve the absorption performance of the microwave absorbing device made of composite foam material, namely, high absorption and low reflection of polluting electromagnetic waves. Attached Figure Description

[0039] Figure 1 This is a comparison diagram of the pore structures of the materials obtained in Example 1 and Comparative Example 1;

[0040] Figure 2 This is a comparison diagram of the pore structures of the materials obtained in Example 2 and Comparative Example 2;

[0041] Figure 3 The graph shows the change in viscoelastic properties of PPO after the addition of carbon filler (CNF / CB).

[0042] Figure 4 A comparison chart of the thermal properties of PPO composite materials;

[0043] Figure 5 A comparison diagram of the dielectric and wave transmission properties of PPO transparent thin materials;

[0044] Figure 6 A comparison chart of the specific absorption efficiency and microwave absorption performance of PPO absorbing materials;

[0045] Figure 7 (a)-(c) are flame retardancy test charts of PPO / SEBS microwave-transparent material with a foaming ratio of 14.7; (d)-(f) are flame retardancy test charts of PPO / SEBS microwave-transparent material with a foaming ratio of 20.8. Detailed Implementation

[0046] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0047] Example 1

[0048] PPO and SEBS granules were dried in an oven at 80-100℃ for 4-6 hours to remove moisture interference. PPO, SEBS, melamine phosphate, and silane coupling agent were pre-blended at room temperature for 3 minutes using a high-speed mixer at 20 r / min. The PPO / SEBS composite sheets were then extruded using a twin-screw extruder. The formulation and process are shown in Tables 1 and 2.

[0049] The resulting composite board was swollen for 4 hours in a supercritical foaming equipment at 185℃, 188℃, 191℃ and 194℃ and a CO2 pressure of 13 MPa. After rapid depressurization and mold opening, PPO / SEBS wave-transparent board was obtained. After post-processing such as edge cutting, slitting and fine carving, various high-frequency, high-speed, low-loss, and high-transparency devices for 5G communication were obtained.

[0050] Table 1. Formulation of PPO / SEBS Composite Board

[0051] Material PPO SEBS melamine phosphate Silane coupling agent Mass fraction (wt%) 70 15 10 5

[0052] Table 2 Extrusion process of PPO / SEBS glass-transparent sheet

[0053] Feed inlet temperature (°C) Maximum barrel temperature (°C) Die head temperature (°C) Screw speed (r / min) Feed rate (kg / h) 170 250 240 160 30

[0054] Example 2

[0055] PPO and SEBS were dried in an oven at 80-100℃ for 4-6 hours to remove moisture interference. PPO, SEBS, melamine phosphate, silane coupling agent, CB, and CNF were pre-blended for 3 minutes at room temperature using a high-speed mixer at 20 rpm. The PPO / SEBS conductive composite sheets were then extruded using a twin-screw extruder. The formulation and process are shown in Tables 3 and 4.

[0056] The obtained conductive composite board was swelled in a supercritical foaming equipment at 185℃, 188℃, 191℃ and 194℃ and CO2 pressure of 13 MPa for 4 hours, and then quickly depressurized and molded to obtain PPO / SEBS absorbing board. After post-processing such as edge cutting, slitting and fine carving, it is used to obtain absorbing devices for radar, communication and other applications.

[0057] Table 3 Formulation of PPO / SEBS Conductive Composite Board

[0058] Material PPO SEBS melamine phosphate Silane coupling agent CB CNF Mass fraction (wt%) 55 15 10 5 7 8

[0059] Table 4 Extrusion Process of PPO / SEBS Absorbing Sheets

[0060] Feed inlet temperature (°C) Maximum barrel temperature (°C) Die head temperature (°C) Screw speed (r / min) Feed rate (kg / h) 182 265 252 160 30

[0061] Comparative Example 1

[0062] The PPO granules were dried in an oven at 80-100℃ for 4-6 hours to remove moisture interference. The PPO, melamine phosphate, and silane coupling agent were pre-blended at room temperature for 3 minutes using a high-speed mixer at 20 r / min. The PPO composite sheets were then extruded using a twin-screw extruder. The formulation and process are shown in Tables 5 and 6.

[0063] The resulting composite board was swollen for 4 hours in a supercritical foaming equipment at 185℃, 188℃, 191℃ and 194℃ and a CO2 pressure of 13 MPa. After rapid depressurization and mold opening, PPO wave-transparent board was obtained. After post-processing such as edge cutting, slitting and fine carving, PPO 5G communication devices were obtained.

[0064] Table 5. Formulation of PPO Composite Board

[0065] Material PPO melamine phosphate Silane coupling agent Mass fraction (wt%) 85 10 5

[0066] Table 6 Extrusion Process of PPO Wave Transparent Material

[0067]

[0068]

[0069] Comparative Example 2

[0070] PPO was dried in an oven at 80-100℃ for 4-6 hours to remove moisture interference. PPO, melamine phosphate, silane coupling agent, CB, and CNF were pre-blended at room temperature for 3 minutes at 20 rpm using a high-speed mixer. The PPO conductive composite sheets were then extruded using a twin-screw extruder. The formulation and process are shown in Tables 7 and 8.

[0071] The resulting conductive composite board was swelled in a supercritical foaming equipment at 185℃, 188℃, 191℃ and 194℃, and CO2 pressure of 13 MPa for 4 hours. After rapid depressurization and mold opening, PPO absorbing board was obtained. After post-processing such as edge cutting, slitting and fine carving, absorbing devices for radar, communication and other applications were obtained.

[0072] Table 7 Formulation of PPO Conductive Composite Board

[0073] Material PPO melamine phosphate Silane coupling agent CB CNF Mass fraction (wt%) 70 10 5 7 8

[0074] Table 8 Extrusion Process of PPO Conductive Absorbing Sheet

[0075] Feed inlet temperature (°C) Maximum barrel temperature (°C) Die head temperature (°C) Screw speed (r / min) Feed rate (kg / h) 220 294 278 160 30

[0076] Experimental Results Analysis

[0077] Electromagnetic wave transmission modulation -- aperture structure:

[0078] Figure 1 The images show the pore structures of Example 1 and Comparative Example 1. The processes are identical in both images, with temperatures from left to right being 185℃, 188℃, 191℃, and 194℃, respectively. Analysis revealed that the addition of SEBS significantly improved the foaming ratio under the same foaming process, while the porosity of Example 1 was significantly lower than that of Comparative Example 1. This indicates that the addition of SEBS, which has good compatibility with PPO, significantly enhances the mobility of the molecular chains, improves the rigidity of PPO, and thus enhances the toughness of the PPO wave-transmitting device. The improved toughness significantly enhances the mobility of the molecular chains, improving not only the absorption and transmission performance but also significantly reducing the internal stress of the device. This eliminates the need for annealing, improves production efficiency, and enhances various performance characteristics of the device.

[0079] Figure 2 The images show the pore structures of Example 2 and Comparative Example 2, with identical manufacturing processes. The temperatures from left to right are 185°C, 188°C, 191°C, and 194°C, respectively. Analysis revealed that the addition of CNF / CB synergistically constructs a rheological network, enhancing the melt strength of PPO. This significantly inhibits cell growth, resulting in a foaming ratio as low as 1.4. The addition of SEBS significantly broadens its toughness, allowing for a larger foaming ratio and pore size at the same temperature. A larger foaming ratio better matches the impedance of air, while the larger pore size and lower cell density result in thicker cell walls. This promotes the bonding between CNFs, further facilitating the construction of the conductive network and consequently the absorption network. These two advantages significantly enhance its absorption performance, i.e., specific absorption efficiency.

[0080] Changes in the substrate structure of the absorbing device:

[0081] Figure 3This figure compares the rheological properties of PPO with CNF and CB (carbon fillers) to pure PPO. As shown in the figure, the PPO with added carbon fillers not only exhibits an increased modulus but also shows a distinct plateau region near the angular frequency of 0.1 rad / s. This indicates that the addition of carbon fillers constructs a rheological network within the matrix, restricting the movement of microscopic molecular chains, resulting in an increased glass transition temperature (Tg). This inhibits cell growth, leading to a lower foaming ratio under the same processing conditions (especially temperature). This will suppress the improvement of microwave absorption performance; therefore, it is necessary to add SEBS to improve molecular chain mobility and increase the amount of introduced air, thereby improving microwave absorption performance.

[0082] Thermal properties of PPO composite materials:

[0083] Figure 4 The figure shows the thermal properties of PPO composites. As can be seen, the Tg of PPO with added SEBS decreases, while the Tg of PPO with added carbon filler increases. Although the addition of SEBS significantly improves its toughness, the overall Tg of the composite material decreases because SEBS itself has lower heat resistance than PPO. The addition of carbon filler constructs a rheological network, restricting the movement of molecular chains and increasing the temperature at which molecular chain movement begins, thus increasing the Tg.

[0084] Wave transmission properties of wave-transmitting devices:

[0085] The empirical formula for the dielectric constant of foamed materials is based on: the percentage of air in the whole material multiplied by the dielectric constant of air (1) plus the percentage of each material in the whole material multiplied by the dielectric constant of each material.

[0086] The empirical formula for dielectric loss of foamed materials is based on the fact that since dry air has no dielectric loss, the dielectric loss of the overall foamed material is the dielectric loss of each individual material multiplied by the percentage of the material volume in the total material volume.

[0087] The relationship between expansion ratio and air content:

[0088] Let the foaming ratio be N, the solid content be 1 / N, and the air content be (N-1) / N;

[0089] Calculate the percentage of each component in the solid portion of the composite foam material, denoted as y1, y2, ..., y n n is the number of solid components;

[0090] Based on the dielectric constant and dielectric loss calculation formulas, the dielectric constant ε and dielectric loss δ of the composite foam material are obtained; whereby the dielectric constant calculation formula is:

[0091] ε=(ε1×y1+ε2×y2+…+ε n ×yn ) / N+ε 气 ×(N-1) / N

[0092] = (ε1×y1+ε2×y2+…+ε n ×y n +ε 气 ×(N-1)) / N,

[0093] In the formula, ε1, ε2, ..., ε n These are the dielectric constants of components 1, 2, ..., n, respectively; ε 气 is the dielectric constant of air, taken as 1; N is the foaming ratio;

[0094] The formula for calculating dielectric loss is:

[0095] δ=(δ1×y1+δ2×y2+…+δ n ×y n ) / N

[0096] In the formula, δ1, δ2, ..., δ n These represent the dielectric losses of components 1, 2, ..., n, respectively; N is the foaming ratio.

[0097] Tables 9 and 11 show the dielectric constant and dielectric loss of PPO / SEBS wave-transparent materials; Tables 10 and 12 show the dielectric constant and dielectric loss of PPO wave-transparent materials. Figure 5 The figure shows the dielectric properties of PPO transparent devices. As can be seen, compared to PPO, PPO / SEBS exhibits a lower dielectric constant and dielectric loss under the same manufacturing process, resulting in better wave transmission. This is because the introduction of SEBS significantly broadens the toughness of PPO, allowing PPO / SEBS to have a higher foaming ratio. Since air has a dielectric constant of 1 and the dielectric loss of dry air is infinitesimal, increasing the amount of air introduced significantly reduces dielectric properties, thus enabling electromagnetic waves to propagate at higher speeds and with lower losses at high frequencies. Conversely, PPO, due to its higher rigidity and limited molecular chain mobility, has a limited capacity for introducing air, resulting in inferior wave transmission performance compared to PPO / SEBS.

[0098] Table 9 Dielectric constants of PPO / SEBS wave-transmitting materials

[0099] Foaming ratio Dielectric constant Empirical value of dielectric constant 1 2.54 2.5625 7.6 1.175 1.20559 11.4 1.117 1.13706 14.7 1.09 1.10629 20.8 1.064 1.07512

[0100] Table 10 Dielectric constants of PPO wave-transparent materials

[0101] Foaming ratio Dielectric constant Empirical value of dielectric constant 1 2.6 2.6 2.1 1.757 1.7619 2.9 1.552 1.55172 3.6 1.445 1.44444 4.5 1.355 1.35556

[0102] Table 11 Dielectric Loss of PPO / SEBS Wave-Transmitting Materials

[0103] Foaming ratio Dielectric loss Empirical value of dielectric loss 1 0.0056 0.005 7.6 0.0017 6.59E-04 11.4 0.0012 4.39E-04 14.7 8.00E-04 3.40E-04 20.8 5.00E-04 2.41E-04

[0104] Table 12 Dielectric Loss of PPO Wave-Transmitting Materials

[0105] Foaming ratio Dielectric loss Empirical value of dielectric loss 1 0.0056 0.0056 2.1 0.0037 0.00276 2.9 0.0029 0.002 3.6 0.0026 0.00161 4.5 0.0022 0.00129

[0106] The absorption performance of the absorbing device:

[0107] Figure 6 The figure shows the absorption performance of PPO absorbing devices. As can be seen, the maximum specific absorption efficiency of the PPO / CNF / CB absorbing device is 45.31 dB*cm. 3 / g, while under the same process conditions, the maximum specific absorption efficiency of PPO / SEBS / CNF / CB absorbing devices is 151.93dB*cm. 3 / g, meaning that after adding SEBS, the specific absorption efficiency increased by 3.35 times. This is because the introduction of air not only significantly improved the impedance to air but also allowed the carbon filler to be selectively distributed within the matrix (only within the polymer, partially not in the air), thus greatly enhancing its specific absorption efficiency. Figure 2 The porous structure, i.e., the thicker bubble wall thickness, is more conducive to the carbon filler building a microwave absorption network within the pore wall. The comprehensive structure gives PPO / SEBS / CNF / CB microwave absorbing devices extremely high microwave absorption performance.

[0108] Flame retardant properties of high foaming ratio devices:

[0109] Figure 4 The DSC curves of the thermal properties show that the addition of SEBS results in a decrease in heat resistance (Tg) because SEBS itself has poorer heat resistance and flame retardancy than PPO. Therefore, the addition of flame retardants synergistically with PPO can improve the flame retardant performance of microwave transmission / absorbing devices. Figure 7 The flame retardant performance of PPO / SEBS microwave-transparent materials with foaming ratios of 14.7 and 20.8 times was tested using vertical burning tests. For the 14.7 times foaming ratio PPO / SEBS microwave-transparent material, the first afterflame time was 2.1s, the second afterflame time was 2.5s, the second afterglow time was 2.2s, and the total time for the second test was 4.7s. No dripping occurred in either test, and the samples self-extinguished rapidly after being removed from the flame, classifying it as V0 grade according to standards. For the 20.8 times foaming ratio PPO / SEBS microwave-transparent material, the first afterflame time was 3.2s, the second afterflame time was 3.9s, the second afterglow time was 2.9s, and the total time for the second test was 6.8s. No dripping occurred in either test, and the samples self-extinguished rapidly after being removed from the flame, classifying it as V0 grade according to standards. Therefore, both microwave-transparent and microwave-absorbing devices exhibit a V0 flame retardant rating at high foaming ratios, meeting the requirements for stable outdoor use.

[0110] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. Use of a polyphenylene ether composite foamed material in a wave-transparent device, characterized in that, The preparation method of polyphenylene ether composite foam material is to dry polyphenylene ether and styrene-ethylene-butene-styrene block copolymer, pre-blend them with melamine phosphate and silane coupling agent, and then extrude them through an extruder to obtain composite material; then the composite material is subjected to supercritical foaming treatment to obtain PPO / SEBS wave-transparent board; In the composite material formulation, the mass fractions of polyphenylene ether, styrene-ethylene-butene-styrene block copolymer, melamine phosphate, and silane coupling agent are 70 wt%, 15 wt%, 10 wt%, and 5 wt%, respectively. The specific method of supercritical foaming treatment is as follows: CO2 is used as a foaming agent, and the solution is swollen for 4 hours at 194℃ and 13 MPa. The preparation method also includes a method for predicting the dielectric properties of the PPO / SEBS wave-transparent substrate, comprising the following steps: The solid content ratio and air content ratio of the solid part in the composite foam material are calculated based on the foaming ratio N. The solid content ratio of the solid part is 1 / N, and the air content ratio is (N-1) / N. Calculate the percentage of each component in the solid portion of the composite foam material, denoted as y1, y2, ..., y n n is the number of solid components; Based on the dielectric constant and dielectric loss calculation formulas, the dielectric constant ε and dielectric loss δ of the composite foam material are obtained; whereby the dielectric constant calculation formula is: ε = (ε1 x y1+ ε2 x y2 +...+ ε n x y n ) / N + ε 气 x (N-1) / N = (ε1 x y1 + ε2 x y2 +... + ε n x y n + ε 气 x (N - 1)) / N, In the formula, ε1, ε2, ..., ε n These are the dielectric constants of components 1, 2, ..., n, respectively; ε 气 is the dielectric constant of air; N is the foaming ratio; The formula for calculating dielectric loss is: δ = (δ1 x y1+ δ2 x y2+...+ δ n x y n ) / N, where δ1, δ2,..., δn are the dielectric losses of components 1, 2,..., n, respectively; and N is the foaming ratio. n where δ1, δ2,..., δn are the dielectric losses of components 1, 2,..., n, respectively; and N is the foaming ratio.

2. Use of a polyphenylene ether composite foamed material in a wave-absorbing device, characterized in that, The preparation method of polyphenylene ether composite foam material is to dry polyphenylene ether and styrene-ethylene-butene-styrene block copolymer, then pre-blend them with melamine phosphate, silane coupling agent, conductive carbon black and carbon fiber, and then extrude them through an extruder to obtain composite material; then the composite material is subjected to supercritical foaming treatment to obtain PPO / SEBS microwave absorbing board. In the composite material formulation, the mass fractions of polyphenylene ether, styrene-ethylene-butene-styrene block copolymer, melamine phosphate, silane coupling agent, conductive carbon black, and carbon fiber are 55 wt%, 15 wt%, 10 wt%, 5 wt%, 7 wt%, and 8 wt%, respectively. The specific method of supercritical foaming treatment is as follows: CO2 is used as a foaming agent, and the solution is swollen for 4 hours at 194℃ and 13 MPa. The resulting PPO / SEBS absorbing sheet has a bubble diameter range of 5-300μm and a foaming ratio of 11.

4.

3. Use of the polyphenylene ether composite foamed material according to claim 1 in a wave-transparent device, characterized in that, The drying method is: drying at 70-100℃ for 3-7 hours; the pre-mixing method is: stirring at room temperature at a speed of 10-50 r / min for 2-10 minutes.

4. The use of the polyphenylene ether composite foamed material according to claim 2 in a wave-absorbing device, characterized in that, The drying method is: drying at 70-100℃ for 3-7 hours; the pre-mixing method is: stirring at room temperature at a speed of 10-50 r / min for 2-10 minutes.

5. Use of the polyphenylene ether composite foamed material according to claim 1 in a wave-transparent device, characterized in that, The temperatures of each section of the extruder process are as follows: conveying section 150-200℃, melting section 210-265℃, extrusion section 200-260℃; screw speed 100-200r / min.

6. The use of the polyphenylene ether composite foamed material according to claim 2 in a wave-absorbing device, characterized in that, The temperatures of each section of the extruder process are as follows: conveying section 150-200℃, melting section 210-265℃, extrusion section 200-260℃; screw speed 100-200r / min.

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