Polyphenyl ether foaming material, preparation process and application

Abstract

The invention discloses a polyphenyl ether foaming material as well as a preparation process and application thereof. The polyphenyl ether foaming material comprises the following components in parts by mass: 60-80 parts of polyphenyl ether; 10 to 20 parts of high density polyethylene; 5 to 15 parts of syndiotactic polystyrene; 2-5 parts of nano boron nitride; 1-5 parts of a compatilizer; 1-3 parts of hyperbranched polyester; and 0.5-2 parts of an organic peroxide cross-linking agent. The foaming material disclosed by the invention has excellent wave-transparent performance and stable dielectric property, and can meet the signal transmission requirement in a high-frequency communication scene; meanwhile, the high-temperature-resistant performance is outstanding, the structure and performance can be kept stable in a high-temperature environment, the application scene is wider, the internal foam structure of the material is uniform and regular, the size deviation is small, and the overall structure stability is high.

Description

Technical Field

[0001] This invention relates to the field of polymer foaming materials technology, and particularly to a polyphenylene ether foaming material, its preparation process, and its application. Background Technology

[0002] With the rapid popularization and large-scale application of 5G communication technology, 5G communication equipment (including 5G antenna covers, base station shells and internal protective components, signal transmission device packaging components, etc.) places stringent requirements on the performance of supporting protective foam materials. On the one hand, they must possess excellent physical protection performance to effectively block dust and impurities from entering the equipment and prevent damage to electronic components, while also possessing good mechanical strength to withstand minor external impacts. On the other hand, since 5G signals are high-frequency signals, the dielectric properties of the materials are extremely demanding, requiring low dielectric constant and low dielectric loss to ensure smooth signal transmission without significant attenuation, thus guaranteeing stable 5G communication quality. Furthermore, the materials must be adaptable to complex outdoor environments, maintaining excellent high-temperature resistance and ensuring structural stability and performance even under medium- and high-temperature conditions. Simultaneously, the uniformity of the foam cell structure is crucial to material performance; small pore size deviations and uniform structure are important prerequisites for ensuring stable dielectric performance and avoiding localized signal attenuation. In addition, the large-scale production requirements of 5G communication equipment also place high demands on the efficient, continuous, and stable manufacturing process of foam materials, requiring mass production while ensuring product performance uniformity.

[0003] Polyphenylene oxide (PPO), due to its regular molecular structure and few polar groups, possesses excellent properties such as low dielectric strength, high temperature resistance, and self-flame retardancy, making it an ideal substrate for preparing wave-transparent protective foam materials for 5G communication equipment. However, existing technologies for modifying and optimizing PPO through foaming have significant shortcomings in improving material performance. For example, modification by adding toughening agents such as SEBS results in a significant reduction in the glass transition temperature of the composite material, sacrificing PPO's high-temperature resistance advantage. This leads to a substantial decrease in the structural stability and dimensional retention of the material under medium- and high-temperature operating environments, making it unsuitable for the outdoor use requirements of 5G equipment. Furthermore, existing technologies do not employ targeted measures for cell refinement and homogenization at the formulation and process levels. The resulting foam materials exhibit a wide range of cell diameter distributions and large dimensional deviations, and are prone to structural defects such as cell rupture and aggregation. Even with good basic dielectric properties, the uneven cell structure can cause localized attenuation of 5G high-frequency signals during propagation, failing to guarantee stable wave transmission and making it difficult to meet the high-precision signal transmission requirements of 5G communication.

[0004] Existing modified foaming solutions cannot retain the high-temperature resistance of materials while improving wave transmission and optimizing cell structure. The prepared foam materials are difficult to match the core requirements of 5G communication equipment for protective foam materials. Summary of the Invention

[0005] To address the shortcomings of existing polyphenylene ether (PPE) foam materials, such as poor component compatibility, uneven cell structure, difficulty in balancing microwave transmission and high-temperature resistance, unstable preparation processes, and high industrialization challenges, this invention proposes a new PPE foam material, its preparation process, and its applications. In terms of material formulation, this invention achieves a balance between low dielectric constant, high heat resistance, and structural stability through the synergistic effect of its components. In terms of the preparation process, a continuous flow is employed, including melt blending in a twin-screw extruder, cooling treatment in a single-screw extruder, homogenization in a static mixer, and supercritical CO2 gradient temperature and pressure controlled foaming. Precise control of process parameters at each step ensures stable and controllable foaming, guaranteeing uniform cell structure in the finished product.

[0006] This invention provides a polyphenylene ether foam material, comprising the following components in parts by weight: 60-80 parts of polyphenylene ether, such as 60, 65, 70, 75, 80 parts, preferably 65-75 parts; 10 to 20 parts of high-density polyethylene, such as 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 parts, preferably 13 to 17 parts; 5 to 15 parts of syndiotactic polystyrene, such as 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 parts, preferably 8 to 12 parts; 2 to 5 parts of nano boron nitride, such as 2, 2.5, 3, 3.5, 4, 4.5, 5 parts, etc., preferably 3 to 4 parts; Compatibilizer 1 to 5 parts, such as 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 parts, etc.; The hyperbranched polyester is 1 to 3 parts, such as 1, 1.5, 2, 2.5, or 3 parts, preferably 1.5 to 2.5 parts; The organic peroxide crosslinking agent is 0.5 to 2 parts, such as 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2 parts, etc., preferably 0.8 to 1.5 parts.

[0007] The numerical ranges of each component described in this specification, such as "60-80 parts" or "1-5 parts", include the endpoints of the range and any achievable intermediate values. Unless otherwise expressly defined, the numerical ranges of this invention include not only the explicitly listed preferred intervals, but also any sub-intervals formed by combinations within each interval and their equivalent variations.

[0008] Those skilled in the art will understand that, without departing from the technical concept of the present invention, appropriate adjustments to the proportions of each component within the above-mentioned range are still within the scope of protection of the present invention.

[0009] Preferably, the density of the high-density polyethylene (HDPE) is 0.940~0.965 g / cm³.3 The melt index (190℃, 2.16kg) is 1~10g / 10min; it can ensure that the system has suitable melt strength, support stable foam cell formation, and prevent collapse or pore formation. It can also make the melt fluidity of the system moderate, which is conducive to the uniform dispersion of each component and the dissolution and diffusion of supercritical CO2, so that the final foamed material has good formability, structural uniformity and comprehensive performance.

[0010] Preferably, the D50 particle size of the nano boron nitride is 50~200nm, which is determined by laser particle size analyzer. Nano boron nitride within the particle size range can form a uniform dispersion in the matrix and is not prone to agglomeration, thus avoiding damage to the dielectric uniformity of the material due to excessively large filler particle size.

[0011] In this invention, HDPE is a non-polar polyolefin polymer with molecular chains composed of saturated C-C bonds. It has no polar groups or polarization centers, resulting in extremely low polarization loss under high-frequency electric fields, which will not negatively affect the low dielectric properties of the PPO-based system. The molecular chains have good flexibility and good compatibility with the non-polar regions in the PPO-based system. In addition, the low-polarity continuous phase of HDPE can serve as a dielectric buffer layer, weakening the interfacial polarization effect between nano-boron nitride and the PPO matrix, reducing dielectric loss at the interface, maintaining the overall dielectric constant of the composite system at a low level, and significantly improving the uniformity of dielectric properties.

[0012] In this invention, the well-ordered crystalline phase of syndiotactic polystyrene can serve as a rigid framework to provide uniform dispersion anchoring points for nano-boron nitride. Through the weak interaction between van der Waals forces and the layered surface of nano-boron nitride, the self-aggregation phenomenon of nano-boron nitride due to its high surface energy is effectively suppressed, achieving uniform dispersion at the nanoscale. At the same time, syndiotactic polystyrene is a non-polar polymer with a low intrinsic dielectric constant. Its crystalline phase can regulate the molecular arrangement of the polymer matrix, reducing polarization loss under high-frequency electric fields. In synergy with hexagonal nano-boron nitride, it further optimizes the overall dielectric parameters of the system, ensuring the core wave transmission performance of low dielectric constant and low dielectric loss.

[0013] In this invention, the polyphenylene ether molecular chain has low polarity and weak polarization response, providing a basis for the system to have a low intrinsic dielectric constant.

[0014] In this invention, the polyphenylene ether is preferably a methyl-terminated linear polyphenylene ether, which can effectively reduce the intermolecular forces and improve its compatibility with high-density polyethylene and syndiotactic polystyrene.

[0015] In this invention, the number-average molecular weight of the polyphenylene ether is preferably 20,000 to 50,000 g / mol, and the molecular chain length is moderate. This ensures that the system has suitable melt strength to support stable cell growth and prevent collapse, while also taking into account melt flowability, which facilitates melt blending and foaming molding.

[0016] In some embodiments, the compatibilizer is selected from any one or more of styrene-maleic anhydride copolymer (SMA), ethylene-vinyl acetate copolymer (EVA), and polypropylene grafted maleic anhydride (PP-g-MAH); the components are uniformly dispersed at the molecular level through the compatibilizer, the system is free from defects such as component agglomeration and phase separation, and the physical properties of each region of the melt are consistent.

[0017] In some embodiments, the polyphenylene ether foam material further includes 0.1 to 0.5 parts of an additive, wherein the additive is an antioxidant or a lubricant; The antioxidant is selected from one or more of hindered phenolic antioxidants and phosphite antioxidants; The lubricant is selected from one or more of stearic acid, zinc stearate, and ethylene bis-stearamide.

[0018] In some embodiments, the hyperbranched polyester is a hydroxyl-terminated hyperbranched polyester; the number-average molecular weight of the hydroxyl-terminated hyperbranched polyester is 1000~5000 g / mol, such as 1000, 2000, 3000, 4000, 5000 g / mol; the hydroxyl functionality is 8~30, such as 8, 10, 12, 14, 16, 18, 20, 30, etc. Controlling the number-average molecular weight within the range of 1000~5000 g / mol allows nucleation sites to be uniformly dispersed in the melt at the nanoscale, further refining the pores, reducing pore size deviation, and ensuring uniform dielectric properties of the material; a hydroxyl functionality of 8~30 can achieve the optimal balance between dispersion effect and dielectric properties. Too many hydroxyl groups will lead to excessively strong polarity of the hyperbranched polyester, which will not only reduce compatibility with the non-polar polymer matrix, but also introduce additional polarization centers, resulting in an increase in the dielectric constant and dielectric loss of the system, thus sacrificing the material's wave transmission performance.

[0019] In some embodiments, the mass ratio of syndiotactic polystyrene to nano-boron nitride is (2~5):1, such as 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, preferably (3~5):1. When the ratio of syndiotactic polystyrene to nano-boron nitride is too low, the nano-boron nitride is prone to agglomeration, resulting in enhanced interfacial polarization and an increase in dielectric constant. When the ratio is too high, the system rigidity is excessively enhanced, the melt flowability decreases, and cell growth is restricted, leading to increased pore size and decreased dielectric uniformity. Therefore, the present invention limits a specific ratio range to achieve a balance between low dielectric constant and good processability.

[0020] In some embodiments, the organic peroxide crosslinking agent is selected from any one or more of dicumyl peroxide, benzoyl peroxide, and di-tert-butyl peroxide; the organic peroxide crosslinking agent achieves in-situ mild crosslinking of the material at 160~180℃, and the formed three-dimensional crosslinking network improves the thermal stability and structural rigidity of the molecular chain, making the material less prone to molecular chain slippage and structural deformation in medium and high temperature environments.

[0021] This invention also provides a preparation process for the polyphenylene ether foam material, comprising the following steps: S1: Mix each component evenly according to the corresponding mass parts to obtain the composite substrate; S2: The composite substrate described in S1 is added to a twin-screw extruder for melt blending and plasticizing to obtain a melt substrate; S3: Supercritical carbon dioxide is introduced into the end of the twin screw, and the temperature is controlled at 240~290℃, the pressure at 10~13MPa, and the time at 4~8 min. After mixing evenly, it is fed into a single screw extruder to cool down to 200~220℃. S4: The material cooled by the single screw extruder is fed into a static mixer for further cooling, and then fed into a foaming die. The temperature is then increased to 240-290°C at a rate of 3-8°C / min, the pressure is reduced to 8-10MPa and maintained for 2-4 minutes, and then cooled at a rate of 2-5°C / min to obtain the polyphenylene ether foam material.

[0022] This invention employs a multi-stage homogenization system consisting of twin-screw melt blending and plasticizing, single-screw extrusion, and static mixer cooling. It ensures consistent cell nucleation through precise supercritical CO2 injection and dissolution, and achieves orderly cell growth and shaping through gradient temperature and pressure control in the foaming die. The fully continuous extrusion foaming process is suitable for the large-scale production needs of 5G equipment and ensures uniform cell size, stable dielectric and heat resistance properties of the material from a process perspective.

[0023] In some embodiments, the screw speed of the twin-screw extruder in step S2 is 80~120 rpm, the feed section temperature is 150~160℃, the mixing section temperature is 240~290℃, and the discharge section temperature is 230~280℃. Using a twin-screw extruder as the mixing equipment, its strong shearing and mixing capabilities can promote rapid and uniform dispersion of the components, avoiding agglomeration.

[0024] In some embodiments, the supercritical carbon dioxide injection rate in step S3 is 0.5~2 L / min. When the injection rate is too low, the amount of carbon dioxide (CO2) dissolved in the melt is insufficient and the dispersion is uneven, resulting in a small number of cell nuclei and uneven cell size during foaming. When the injection rate is too high, CO2 cannot be fully mixed with the melt in time, which easily leads to local bubble aggregation, destroys the uniformity of the system, and may also cause excessive system pressure fluctuations, affecting the foaming stability.

[0025] In some embodiments, the screw speed of the single-screw extruder in step S3 is 60~100 rpm, the screw length-to-diameter ratio is (25~35):1, the feed section temperature is 170~180℃, the plasticizing section temperature is 240~290℃, and the discharge section temperature is 230~280℃.

[0026] The process parameters such as temperature, pressure, and time described in this specification are allowed to have reasonable errors or equipment deviations in industrial production. As long as they do not substantially affect the material structure and performance, they should be considered to fall within the technical scope of this invention.

[0027] The present invention also provides the application of the polyphenylene ether foam material in 5G communication equipment; the 5G communication equipment includes, but is not limited to, 5G antenna covers, 5G base station shells and internal protective components, 5G signal transmission device packages, and 5G terminal equipment signal protection components.

[0028] In summary, compared with the prior art, the present invention achieves the following technical effects: 1. The foaming material of the present invention has both excellent wave transmission performance and stable dielectric properties, which can meet the signal transmission requirements in high-frequency communication scenarios; at the same time, it has outstanding high temperature resistance, can maintain structural and performance stability in high temperature environments, has a wider range of applications, and the internal cell structure of the material is uniform and regular with small dimensional deviations, resulting in strong overall structural stability.

[0029] 2. This invention uses a specific process to achieve stable and controllable foaming, with uniform cell nucleation and growth, resulting in good consistency in finished product quality. While ensuring low dielectric constant and high heat resistance, the mechanical properties and processing performance of the material are also taken into account. It is highly practical, and the overall formula and process are highly adaptable, enabling continuous and stable production and facilitating industrial promotion and application. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0031] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all materials and reagents used are commercially available.

[0032] The product names or manufacturers listed in this instruction manual are for illustrative purposes only and do not constitute a limitation on the source of materials. Materials with the same or similar technical parameters and performance indicators can be used as substitutes.

[0033] Main raw material information: Polyphenylene oxide: SABIC NORYL TM PPE 646, number average molecular weight 21700 g / mol, SABIC.

[0034] High-density polyethylene: DMDA-8007 NT 7 HDPE, density 0.965 g / cm³ 3 Melt index 8.3 g / 10min (190°C / 2.16kg), Dow Chemical.

[0035] Syndiotactic polystyrene: XAREC TM S123, inter-specificity >99%, produced by Ikumitsu Kogyo.

[0036] Nano boron nitride: Q-0002505, particle size 100 nm, Shanghai Qiyue Biotechnology.

[0037] Hyperbranched polyester #1: HyPer H2O2, number average molecular weight 1200 g / mol, 10~12 hydroxyl groups, Wuhan Hyperbranched Resin Technology Co., Ltd.

[0038] Hyperbranched polyester #2: HyPer H201, number average molecular weight 600 g / mol, 5-7 hydroxyl groups, Wuhan Hyperbranched Resin Technology Co., Ltd.

[0039] Compatibilizer #1: Ethylene-vinyl acetate copolymer, TAISOX® 7A50H, Formosa Plastics, Taiwan.

[0040] Compatibilizer #2: Styrene-maleic anhydride copolymer, SMA-1000, Alibaba.

[0041] Organic peroxide crosslinking agent: dicumyl peroxide, 98%, Beijing Bailingwei.

[0042] Antioxidant: Irganox® 1010; the same substance was used in parallel tests.

[0043] Styrene-ethylene-butene-styrene block copolymer (SEBS): G1650, Kronen.

[0044] In this invention, the selection and proportioning of each component aim to achieve a synergistic effect of low dielectric constant, low dielectric loss, excellent heat resistance, and uniform cell structure in the foaming material. Any technical means that can achieve the above-mentioned technical effects, regardless of whether they use the exact same material type or processing conditions as this embodiment, should be considered an equivalent solution to the technical concept of this invention.

[0045] Raw material pretreatment: Polyphenylene ether, high-density polyethylene, syndiotactic polystyrene, hyperbranched polyester, and compatibilizer were placed in a hot air circulating drying oven and dried at 100℃ for 4 hours to remove moisture from the raw materials; nano boron nitride was placed in an 80℃ drying oven and dried for 6 hours to prevent the agglomeration of inorganic fillers; dicumyl peroxide (DCP) and antioxidant 1010 were sealed and stored at room temperature for later use.

[0046] Example 1 The raw materials for the polyphenylene ether foaming material in this embodiment are as follows: 60 parts polyphenylene ether, 10 parts high-density polyethylene, 5 parts syndiotactic polystyrene, 2 parts nano boron nitride, 1 part compatibilizer #1, 1 part hyperbranched polyester #1, 0.5 parts organic peroxide crosslinking agent, and 0.1 parts antioxidant.

[0047] The preparation steps of the polyphenylene ether foam material in this embodiment are as follows: Step 1: Weigh all the pretreated raw materials according to the formula weight, add the above raw materials into a high-speed mixer, control the speed to 800 r / min, mix at room temperature, so that the components are initially dispersed evenly, and obtain the composite substrate.

[0048] Step 2: Add the composite substrate from Step 1 to a twin-screw extruder (screw length-to-diameter ratio 40:1) for melt blending and plasticizing. Specific process parameters are as follows: screw speed: 100 rpm; temperatures of each section: feed section 155℃, mixing section 260℃, discharge section 240℃; barrel pressure: 2.5 MPa; melt blending time: 10 min; crosslinking reaction time: 8 min. Supercritical CO2 was introduced into the last third of the twin-screw extruder through a high-pressure metering pump with the following parameters: supercritical CO2 injection rate: 1.0 L / min; dissolution section temperature: 240℃, pressure: 12 MPa; isothermal and pressure dissolution time: 4 min, resulting in a homogeneous CO2 melt.

[0049] Step 3: The CO2 homogeneous melt obtained in Step 2 is continuously fed into a single-screw extruder (screw length-to-diameter ratio 30:1, speed 80 rpm) for cooling treatment, and then introduced into a static mixer at a mixing temperature of about 200℃.

[0050] Step 4: The homogeneous CO2 melt obtained in Step 3 is continuously fed into a foaming die (die diameter 80mm) for gradient temperature and pressure controlled foaming, followed by gradient cooling and molding. The specific process parameters are as follows: Gradient heating: The temperature inside the foaming die is increased from 200℃ to 260℃ at a rate of 5℃ / min; Gradient depressurization: The pressure inside the die is simultaneously reduced from 12MPa to 9MPa. After the melt is extruded through the die, it is instantly reduced to atmospheric pressure to form uniform bubble nuclei, and the cell growth and shaping are completed in the external cooling zone to obtain polyphenylene ether foam material.

[0051] Example 2 The raw materials for the polyphenylene ether foaming material in this embodiment are as follows: 75 parts polyphenylene ether, 15 parts high-density polyethylene, 10 parts syndiotactic polystyrene, 3.5 parts nano boron nitride, 13 parts compatibilizer #, 2 parts hyperbranched polyester #1, and 1 part organic peroxide crosslinking agent.

[0052] The preparation steps of the polyphenylene ether foam material in this embodiment are the same as in Example 1.

[0053] Example 3 The raw materials for the polyphenylene ether foaming material in this embodiment are as follows: 75 parts polyphenylene ether, 15 parts high-density polyethylene, 10 parts syndiotactic polystyrene, 3.5 parts nano boron nitride, 13 parts compatibilizer #1, 2 parts hyperbranched polyester #2, and 1 part organic peroxide crosslinking agent.

[0054] The preparation steps of the polyphenylene ether foam material in this embodiment are the same as in Example 1.

[0055] Example 4 The raw materials for the polyphenylene ether foaming material in this embodiment are as follows: 75 parts polyphenylene ether, 15 parts high-density polyethylene, 10 parts syndiotactic polystyrene, 3.5 parts nano boron nitride, 23 parts compatibilizer #2, 2 parts hyperbranched polyester #1, and 1 part organic peroxide crosslinking agent.

[0056] The preparation steps of the polyphenylene ether foam material in this embodiment are the same as in Example 1.

[0057] Example 5 The raw materials for the polyphenylene ether foaming material in this embodiment are as follows: 80 parts polyphenylene ether, 20 parts high-density polyethylene, 15 parts syndiotactic polystyrene, 5 parts nano boron nitride, 5 parts compatibilizer #1, 3 parts hyperbranched polyester #1, 2 parts organic peroxide crosslinking agent, and 0.5 parts antioxidant.

[0058] The preparation steps of the polyphenylene ether foam material in this embodiment are as follows: Step 1: Weigh all the pretreated raw materials according to the formula weight, add the above raw materials into a high-speed mixer, control the speed to 800 r / min, mix at room temperature, so that the components are initially dispersed evenly, and obtain the composite substrate.

[0059] Step 2: Add the composite substrate from Step 1 to a twin-screw extruder (screw length-to-diameter ratio 40:1) for melt blending and plasticizing. The specific process parameters are as follows: screw speed: 80 rpm; temperatures of each section: feed section 150℃, mixing section 290℃, discharge section 260℃; barrel pressure: 3 MPa; melt blending time: 10 min; crosslinking reaction time: 8 min. Supercritical CO2 was introduced through a high-pressure metering pump at one-third of the end of the twin-screw extruder. The specific parameters were: supercritical CO2 injection rate: 2.0 L / min; dissolution section temperature: 240℃, pressure: 12MPa; constant temperature and pressure dissolution time: 4min, to obtain a homogeneous CO2 melt.

[0060] Step 3: The CO2 homogeneous melt obtained in Step 2 is continuously fed into a single-screw extruder (screw length-to-diameter ratio 30:1, rotation speed 80 rpm) for cooling treatment, and then introduced into a static mixer at a mixing temperature of 200℃.

[0061] Step 4: The homogeneous CO2 melt obtained in Step 3 is continuously fed into a foaming die (die diameter 80mm) for gradient temperature and pressure controlled foaming, followed by gradient cooling and molding. The specific process parameters are as follows: Gradient heating: The temperature inside the foaming die is raised to 260℃ at a rate of 5℃ / min; Gradient depressurization: The pressure inside the die is simultaneously reduced from 12MPa to 9MPa. After the melt is extruded through the die, it is instantly reduced to atmospheric pressure to form uniform bubble nuclei, and the cell growth and shaping are completed in the external cooling zone to obtain polyphenylene ether foam material.

[0062] Example 6 The raw materials for the polyphenylene ether foaming material in this embodiment are as follows: 75 parts polyphenylene ether, 15 parts high-density polyethylene, 10.8 parts syndiotactic polystyrene, 2.7 parts nano boron nitride, 3 parts compatibilizer #1, 2 parts hyperbranched polyester #1, and 1 part organic peroxide crosslinking agent.

[0063] The preparation steps of the polyphenylene ether foam material in this embodiment are the same as in Example 1.

[0064] Comparative Example 1 The raw materials for the polyphenylene ether foam material in this comparative example are as follows: 77 parts polyphenylene ether, 15 parts high-density polyethylene, 10 parts syndiotactic polystyrene, 3.5 parts nano boron nitride, 13 parts compatibilizer #, and 1 part organic peroxide crosslinking agent.

[0065] The preparation steps are the same as in Example 1.

[0066] Comparative Example 2 The raw materials for the polyphenylene ether foam material in this comparative example are as follows: 85 parts polyphenylene ether, 15 parts high-density polyethylene, 10 parts syndiotactic polystyrene, 3.5 parts nano boron nitride, 13 parts compatibilizer #, 2 parts hyperbranched polyester #1, and 1 part organic peroxide crosslinking agent.

[0067] The preparation steps are the same as in Example 1.

[0068] Comparative Example 3 The raw materials for the polyphenylene ether foam material in this comparative example are as follows: 78.5 parts polyphenylene ether, 15 parts high-density polyethylene, 10 parts syndiotactic polystyrene, 3 parts compatibilizer #1, 2 parts hyperbranched polyester #1, and 1 part organic peroxide crosslinking agent.

[0069] The preparation steps are the same as in Example 1.

[0070] Comparative Example 4 The raw materials for the polyphenylene ether foam material in this comparative example are as follows: 75 parts polyphenylene ether, 15 parts high-density polyethylene, 10 parts SEBS, 3.5 parts nano boron nitride, 3 parts compatibilizer #1, 2 parts hyperbranched polyester #1, and 1 part organic peroxide crosslinking agent.

[0071] The preparation steps are the same as in Example 1.

[0072] Comparative Example 5 The raw materials for the polyphenylene ether foam material in this comparative example are as follows: 90 parts polyphenylene ether, 10 parts syndiotactic polystyrene, 3.5 parts nano boron nitride, 3 parts compatibilizer #1, 12 parts hyperbranched polyester #, and 1 part organic peroxide crosslinking agent.

[0073] The preparation steps are the same as in Example 1.

[0074] Comparative Example 6 The raw materials of the polyphenylene ether foam material in this comparative example are the same as those in Example 2. The difference in the preparation steps is that in step 4, the temperature is directly increased from 200°C to 220°C and the pressure is suddenly reduced from 12MPa to 9MPa, without using gradient temperature control and gradient pressure reduction.

[0075] Comparative Example 7 The raw materials for the polyphenylene ether foaming material in this comparative example are the same as those in Example 2. The difference in the preparation steps is that steps 3 and 4 are replaced by placing the obtained molten substrate into a high-pressure reactor, sealing it, and then introducing CO2 gas. The reactor is kept at 200°C and 12MPa for 60 minutes. After saturation, the pressure relief valve is opened instantly to quickly release the pressure to atmospheric pressure, thus completing the foaming process.

[0076] <Testing Methods> All performance parameters described in this invention were measured under specific test conditions. If the test methods or test conditions are reasonably changed, and the obtained data exhibits reasonable fluctuations while still meeting relevant standards, it still falls within the scope of the technical effects achieved by this invention.

[0077] (1) Wave transmission performance: The tests were conducted according to the standard GB / T 1409-2006, adapted to 5G high-frequency signal application scenarios. The test frequency was set to 3GHz. Before testing, the foamed material sheets prepared in each embodiment and comparative example were cut into standard samples of 50mm×50mm×2mm to ensure that the sample surface was flat, free of bubbles, damage, and impurities. Three parallel samples were prepared for each test group. During testing, the high-frequency dielectric constant tester was preheated for 30 minutes. The zero point and accuracy of the instrument were calibrated using a polytetrafluoroethylene standard block (with a known dielectric constant ≈ 2.1). The samples were then placed in the test chamber, and the test environment temperature was controlled at 23±2℃ and the relative humidity at 50±5%. The samples were kept in close contact with the test electrodes without gaps. After starting the test, each sample was tested three times, and the average value was taken as the final test results of the dielectric constant (ε) and dielectric loss tangent (tanδ) of the foamed material. (2) High temperature resistance: Referring to the standard GB / T 1634.2-2004, a load of 0.45 MPa was used to simulate the long-term heat load of the material in 5G outdoor equipment, and the heat distortion temperature was tested to characterize the high-temperature resistance of the material. The test specimens were cut to standard dimensions of 80 mm × 10 mm × 4 mm, and the specimens were required to be free of cracks and bubbles and have a smooth surface. Three parallel specimens were prepared for each test group. Before the test, the load was calibrated to 0.45 MPa, the heating rate was set to 120 °C / h and the heating program was started. The temperature corresponding to the specimen deformation of 0.32 mm (i.e., heat distortion temperature) was observed and recorded in real time. Each specimen was tested three times and the average value was taken as the final test result.

[0078] (3) Bubble performance test: The average diameter of the bubble cells and the dimensional deviation rate were tested in accordance with the standard GB / T 12833-2022.

[0079] The test results are shown in Table 1:

[0080] As shown in Table 1, the foaming materials of the present invention exhibit excellent comprehensive performance. The dielectric constants are all less than 1.20, the dielectric loss tangent is no higher than 0.0007, and the wave transmission effect is excellent. The heat distortion temperature is all greater than 130℃, with Example 6 reaching as high as 140℃, demonstrating excellent high-temperature resistance and suitability for 5G outdoor high-temperature environments. The average cell diameter of all examples is no higher than 38μm, and the dimensional deviation rate is no higher than 7.0%, indicating good cell uniformity and meeting the requirements for dielectric uniformity and structural stability of 5G wave-transparent materials.

[0081] Compared to Example 2, Comparative Example 1 showed fewer cell nuclei and uneven nucleation rates during foaming, leading to disordered cell growth and cloning, resulting in excessively large cell sizes and a surge in deviation rates, thus disrupting dielectric uniformity. Simultaneously, the unstable cell structure caused a slight decrease in heat resistance. In Comparative Example 2, the melt strength decreased, and the cell walls could not withstand internal pressure during foaming, easily leading to cloning and collapse. Furthermore, the melt viscosity imbalance resulted in uneven CO2 dispersion, disordered cell nucleation and growth, and increased size deviation. In Comparative Example 3, the heat resistance significantly decreased, and the uneven thermal conductivity and stress distribution within the melt caused cell collapse and increased size deviation during foaming. Dielectric loss also increased, and wave transmission performance deteriorated. In addition, the absence of syndiotactic polystyrene disrupted the dielectric uniformity of the system, leading to an increase in dielectric constant and a decrease in wave transmission performance. Heat resistance also slightly declined due to the lack of synergistic effects from the heat-resistant components. In Comparative Example 4, the compatibility decreased, melt blending was uneven, and the cell wall strength during foaming was insufficient. In Comparative Example 5, the melt flowability is poor, CO2 cannot penetrate and dissolve quickly and uniformly, and the molten substrate has insufficient plasticity. During foaming, the cell growth is limited and the size is uneven, affecting both heat resistance and microwave transmission performance. In Comparative Example 6, sudden changes in temperature and pressure during foaming cause the cell growth rate to run out of control. When high temperature and high pressure are released instantaneously, the cells expand rapidly and grow unevenly. Some cells rupture due to excessive expansion, while others do not grow completely due to insufficient pressure, resulting in large cell size deviations and unstable structures, which in turn affects dielectric uniformity. In Comparative Example 7, the molten substrate and CO2 cannot be fully mixed and dissolved, and there is no gradient temperature and pressure control. During foaming, cell nucleation and growth are in a disordered state. Compared with the continuous gradient foaming process of this application, the cell size is more disordered and the deviation rate is higher. At the same time, the intermittent process leads to uneven component dispersion, and the heat resistance and microwave transmission performance are significantly worse than those of the examples.

[0082] In summary, all comparative examples exhibited significantly reduced wave transmission performance, insufficient high-temperature resistance, and poor cell uniformity due to missing formulation components, improper component substitution, or deviations in preparation processes. These issues failed to meet the requirements of 5G communication equipment for wave transmission, high-temperature resistance, and structural stability. In contrast, the embodiments of this application, through reasonable formulation design and optimized preparation processes, achieve a synergistic effect of good wave transmission, excellent high-temperature resistance, and uniform cell size in the foamed material, significantly outperforming the comparative examples that deviated from the technical solution of this application.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A polyphenylene ether foam material, characterized in that, Based on parts by weight, it includes the following components: 60-80 parts of polyphenylene ether; 10-20 parts of high-density polyethylene; 5-15 parts of syndiotactic polystyrene; 2-5 parts of nano boron nitride; 1-5 parts compatibilizer; 1-3 parts of hyperbranched polyester; 0.5 to 2 parts of organic peroxide crosslinking agent.

2. The polyphenylene ether foam material according to claim 1, characterized in that, The compatibilizer is selected from any one or more of styrene-maleic anhydride copolymer, ethylene-vinyl acetate copolymer, and polypropylene grafted with maleic anhydride.

3. The polyphenylene ether foam material according to claim 1, characterized in that, The polyphenylene ether foam material further includes 0.1 to 0.5 parts of additives, wherein the additives are antioxidants or lubricants; The antioxidant is selected from one or more of hindered phenolic antioxidants and phosphite antioxidants; The lubricant is selected from one or more of stearic acid, zinc stearate, and ethylene bis-stearamide.

4. The polyphenylene ether foam material according to claim 1, characterized in that, The hyperbranched polyester is a hydroxyl-terminated hyperbranched polyester; The number-average molecular weight of the terminal hydroxyl hyperbranched polyester is 1000~5000 g / mol, and the hydroxyl functionality is 8~30.

5. The polyphenylene ether foam material according to claim 1, characterized in that, The mass ratio of syndiotactic polystyrene to nano-boron nitride is (2~5):

1.

6. The polyphenylene ether foam material according to claim 1, characterized in that, The organic peroxide crosslinking agent is selected from any one or more of dicumyl peroxide, benzoyl peroxide, and di-tert-butyl peroxide.

7. The preparation process of the polyphenylene ether foam material according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1: Mix each component evenly according to the corresponding mass parts to obtain the composite substrate; S2: The composite substrate described in S1 is added to a twin-screw extruder for melt blending and plasticizing to obtain a melt substrate; S3: Supercritical carbon dioxide is introduced into the end of the twin screw extruder, and the temperature is controlled at 240~290℃, the pressure at 10~13 MPa, and the time at 4~8 min. After being mixed evenly, it is fed into a single screw extruder to cool down to 200~220℃. S4: The material cooled by the single screw extruder is fed into a static mixer for further cooling, and then fed into a foaming die. The temperature is then increased to 240-290°C at a rate of 3-8°C / min, the pressure is reduced to 8-10MPa and maintained for 2-4 minutes, and then cooled at a rate of 2-5°C / min to obtain the polyphenylene ether foam material.

8. The preparation process according to claim 7, characterized in that, The screw speed of the twin-screw extruder in step S2 is 80~120 rpm, the feed section temperature is 150~160℃, the mixing section temperature is 240~290℃, and the discharge section temperature is 230~280℃.

9. The preparation process according to claim 7, characterized in that, The supercritical carbon dioxide injection rate in step S3 is 0.5~2 L / min.

10. The application of the polyphenylene ether foam material according to any one of claims 1 to 6 in 5G communication equipment.

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